Abstract:To reduce the serious vibration and fruit dropping that may occur in highspeed robotic harvesting of fruit clusters, a simulation model of fruit cluster vibration is necessary to vibration law discovery, influencing factor analysis and optimal control study. To achieve all of the above objectives, the simulation model must take into account of the individual difference of component properties and embody the complex multilevel stem structure, multiple fruits distribution and multiplex excitation transmission. Therefore, a flexible rodhingerigid rodmass composite model was first put forward based on the structure of stemfruit system of grape cluster, and viscoelastic property of hinges and bending property of main spikestalk were determined by large sample tests. Then, simulation model of grape fruit cluster was constructed by reconstitution of the solid stem system with 3D laser scan, replacement of main spikestalk with flexible rod, random addition of fruits and definition of different components according to their normal distribution from the above test results. The accuracy of the simulation model was verified by experiments, and error of the mean value and standard deviation of fruit relative swinging angle under different excitation methods are within 2% and 6.6%, respectively. Finally, the effects of various excitation methods and harvesting stages on cluster vibration were analyzed with this model. To conclude, the successful establishment of this simulation model of grape fruit cluster provides an excellent analytical tool for robotic lowvibration and antifall harvesting of various fruit clusters.

Abstract:Aiming at establishing a 3D point cloud model of fruit tree with true color to provide scientific guidance for the production management of orchard, a research on the registration method for two pieces of 3D original point clouds of fruit tree obtained from different perspectives was carried out. The 3D raw point clouds of apple tree in two perspectives were obtained based on Kinect camera and information fusion technology. Firstly, the background removal and noise filtering approaches were used to implement a data pretreatment for each piece of raw point cloud, and every relative exact point cloud of single apple tree was acquired in each specific angle. Secondly, by using depth information of fruit tree’s point cloud image and object boundary characteristics, the key points were extracted based on NARF (Normal aligned radial feature) algorithm. Meanwhile, the FPFH (Fast point feature histograms) descriptor was developed to obtain the characteristic vector for each key point. Thirdly, according to the characteristic vectors, the pairs of corresponding key points between two pieces of point cloud were estimated and extracted. And the spatial mapping relationships between two pieces of point cloud were calculated by validating and refining all pairs of corresponding key points based on the RANSAC (Random sample consensus) algorithm. Then the rotation matrix and translation vector between the two neighboring point clouds were computed, by which, the initial registration of two adjacent pieces of point cloud was achieved further. Finally, on the basis of the initial registration, two pieces of point cloud were fused into the same space coordinate system to complete their precise registration through applying the ICP(Iterative closest point) algorithm. This paper carried out the experiments based on the above algorithms, and the results showed that the improved point cloud registration method could be used to match two pieces of point cloud at any original positions in space, and its mean registration error reached 0.7cm.

Abstract:With the increase of demand for organic vegetable, automated mechanical weeding machines are more and more in need. According to the working condition and requirement of weeding operation for transplanted vegetable crops, an electric driven weeding robot system was developed and tested. Carried by a middle or lowhorsepower tractor, the weeding robot could efficiently remove inter and intrarow weeds. The system was equipped with a machine vision system, which acquired and processed field images in real time to recognize crops and obtain their locations. Four electric motors were used to drive three crescent weeding blades and the steering mechanism to avoid crops and follow crop rows. The system had two microcontrollers to control weeding blades and the steering mechanism separately. The controllers fused bladecrop distance, phase position of motors and forward speed of robot, to accurately guide the weeding blades avoiding crops and tracking the rows. To evaluate the working performance of weeding robot, tests were conducted on concrete road surface and in field respectively. Results of the tests indicated that the robot could remove 90% weeds while the crop damage rate was less than 10%, when the speed was under 1.5km/h and plant spacing was above 0.35m. Compared with hydraulic driven weeding machine, it had lower energy consumption, less pollution and better servo property.

Abstract:The displacement of soil and straw is an important part of conservation tillage and straw returning to field. To analyze and compare the displacements, field experiments with downcut and upcut rotary tillage were conducted under rotational speeds of 180, 230, 280r/min. The aluminum block and colored straw were labeled and arranged in lines parallel to the rotor axial to measure soil and straw displacement. The original and final positions of soil and straw tracers were drawn in CAD, it is found that the shape of final positions was similar to the arrangement of rotary blades attached to the rotor. The comparison of soil surface morphology and displacements of soil and straw were done with downcut and upcut rotary tillage, and conclusions are drawn as follows: straw burial rate in the downcut rotary tillage was higher than that of upcut rotary tillage, but the soil breakage rate in upcut rotary tillage was higher. The distribution of soil tracers was uniform after tillage; lateral and longitudinal straws appear aggregation phenomenon after two kinds of tillage and downcut rotary tillage was more obvious. The displacements of soil and straw in upcut rotary tillage are better than those of downcut rotary tillage, the displacements in upcut rotary tillage decreased with increasing rotational speed while the displacements in downcut rotary tillage increased with increasing rotational speed. Based on these findings, the operation type, rotational speed and the shape of the arrangement of rotary blades could be adjusted to meet the different requirements in horticulture.

Abstract:Panax notoginseng is one of rare medicinal herbs in China, and it is mainly grown in Yunnan Province. Market demand of Panax notoginseng is very large, and hence, until December 2014, the planting area of Panax notoginseng has reached 40000hm2. However, there is no precision seeding device suitable for Panax notoginseng. Seedfilling performance is the key factor that influences the properties of metering device. In order to improve the seedfilling performance of pneumatic cylinder seedmetering device, Yunnan Wenshan notoginseng seeds were adopted as sowing objects, the method of coupling DEM-CFD was used as research technique, meanwhile, variance yields of average normal stress and height of supplying seeds were considered as the optimizing targets. Through single factor experiment, the blowing wind pressure, vibration frequency and vibration angle were numerically simulated. It can be found that the experimental phenomenon and effect were in consistent with the simulation ones. Results showed that the blowing wind pressure can break the original steady state, thus reduce seeds transient normal stress which lower seeds internal friction; vibration frequency increases variance yields of average normal stress of seeds, hence disturbance of seeds was enhanced; and adequate vertical oscillation can effectively improve height of supplying seeds. Reducing internal friction, enhancing disturbance, improving height of supplying seeds can effectively improve the seed filling performance. To find the best parameter combination, this paper used three factors and five levels orthogonal experimental method to test the metering performance, afterwards, the results of the test were optimized and verified. Results showed that at the vibration frequency of 85Hz, blowing wind pressure of 3kPa, vertical oscillation of 45°, experimental index is the best. Test indicators, including eligible index, missing index, multiple index can reach up to 93.02, 1.42 and 5.56, respectively.

Abstract:In order to shorten the corn seeding period, reduce the waste of corn seeds and insure the sowing quality, the highspeed precise seeding technology has become an important direction of corn seeder development, which mainly includes pneumatic type of corn seeder and mechanical type of corn seeder. So the corn metering device which is the core component of corn seeder attracted many experts and scholars to study. And the results showed that the pneumatic corn metering device existed inaccurate sowing precision and the mechanical corn metering device owns poor adaptability for highspeed operation and different corn seed shapes and so on. According to the above practical problems, a telescopic clip finger type of corn precise metering device was developed which owns two advantages such as simple structure and good seeding performance. Its influenced laws with the main structural parameters to the metering performance were firstly studied, and the main parameters influenced the metering performance were determined by the orthogonal test method which included clamping force, opening distance of clipfinger and the rotating speed of metering plate. And their optimal experimental results were: the clamping force of 0.87N, opening distance of 16mm and the rotating speed of metering plate of 45r/min. And the corresponding performance indexes are as following: the spacing of the qualified rate is 95.4%, the leakage sowing rate is 1.9% and the replanting rate is 2.7%, which could completely meet the requirement of the technical specifications of quality evaluation for drills in China. The research provides a reference for further improving quality and optimizing the parameter for clip finger type of metering device.

Abstract:To meet the requirements of precision rice directseeder and linear and holey sowing of the seeds lining and holing in the operation of field seeding , a precision hilldirectseeding seed metering device with spiral slots and hookspoons was developed to improve the current situation of labor .The movement track of spiral slot inner sprouting rice seed was analyzed in the process of seedsowing by means of the Matlab software, as well as rotational quadratic orthogonal experiments was used to further analyze the effects of the rate of average hill diameter, the rate of seeds’ number in the hill and leakseeding rate on seeding performance: rotation speed, working length of spiral sheave and lead angle. The JPS-12 detecting and experimental set of seed metering device was selected to test sowing performance. Experimental data was analyzed by Design-Expert software so as to establish the mathematical model between the experimental factors and experimental indexes. The result showed that the best operational parameter combination was lead angle of 71.0°, working length of spiral sheave of 10.8mm, and the rotation speed of 23.2r/min. The correct rate of average hill diameter was 91.06%, the correct rate of seeds’ number in the hill was 94.64% and the leakageseeding rate was 3.64%. The sowing performance can meet the requirement of rice planting in the operation of field.

Abstract:Dynamics analysis and relative tests were conducted for an innovatively designed rotary rice potseedling transplanting mechanism of planetary gear train with ellipse gears and incomplete noncircular gear. Based on the force analysis of each moving component in the transplanting mechanism with dynamic static analysis method, the dynamics equations in analytical form were established while the dynamics mathematical model of the mechanism was built. The order to solve the dynamics mathematical model of the mechanism was determined by using the dynamics equations sequencesolution method, then the variation law of force between various positions and the rotary angle of planetary carrier of the mechanism in a working cycle was obtained, with the use of a dynamics analysis software which was independently developed on the basis of Visual Basic software. Through the analysis of the mutation points and some key points of the variation curves and combining the working process of the mechanism, the causes of the force changes were explained in theory. Finally, dynamics test bench was built to carry out noload dynamics tests to obtain dynamics characteristics of the mechanism with three different rotary speeds of 130r/min, 160r/min and 190r/min. At the same time, the correctness of dynamics model was verified through comparing test curves and theoretical curves. The study will provide a reliable dynamics model and test basis for the optimization of the dynamics performance and the improvement of the working performance of the mechanism.

Abstract:Xinjiang is one of the most important highquality cotton production areas in China, and sprayers with horizontal boom and hang boom are widely used in ripening and defoliation of the cotton. Due to the close planting cultivation of cotton, in the lower part of the cotton canopy, the spraying coverage of the defoliant is low and defoliation effect is poor, which seriously affects the cotton quality. In order to improve the spraying coverage rate of the defoliant in the middle and lower cotton, a scheme for 〖JP3〗optimizing the parameters of the divider was put forward, and it was designed and developed by using Box-〖JP〗Behnken. The parameters, such as top rake of the crop divider, ground clearance, field speeds were taken as the influencing factors, and spray coverage and resistance of crop divider were used as test indices in the experimental study, obtaining the test indices though field test with test equipment designed. By using the ellipsoidal basis function neural network (EBFNN) the relationship between the indices and test factors was approached, then accurate and reliable approximation model was established. Then the multiobjective genetic algorithm was used to optimize the coverage rate and resistance of crop divider based on this approximate model in Isight software platform, the optimal parameters combination was obtained through determining the weight coefficient of the optimized solution set. Best combination of test parameters were listed below: ground clearance of the crop divider was 210mm, the top rake of the crop divider was 12°, and the operation speed of the sprayer was 4km/h. Field experiments were carried out under this condition, the results show that the average droplet coverage on cotton canopy was 22.49%, compared with the model prediction, the error range was less than 10.89%, and the root mean square value of grain resistance test was 70.9N, the error range was less than 7.78%. It can provide a reference for cotton crop divider design and spraying parameters optimization of boom sprayer, and also greatly promote the progress of cotton defoliation harvesting mechanization.

Abstract:Separation chamber is an important part of the seed airscreening machine, and therefore the values of its fan frequency and air outlet magnitude have significant effects on the quality of seed separation. The RNG k-ε turbulence model and the DPM discrete phase model were adopted to simulate the separation process of seeds in the separation chamber. Then, the simulation results were analyzed by means of polynomial fitting, and the relationship between the working parameters, i.e. fan frequency and air outlet magnitude, and the cleaning performance, i.e. cleaning rate and loss rate were acquired. Based on this relationship, cleaning efficiency can be determined by calculating cleaning rate and losing rate, which synthetically reflects the quality of cleaning effect under different working conditions. It is convenient to analyze optimal working parameters of separation chamber by 3D map and contour map of the cleaning efficiency. By this means, the optimal working parameters of the fan frequency and air outlet magnitude for Chinese cabbage seeds, spinach seeds and pakchoi seeds, were obtained, which are 35Hz and 75%, 42Hz and 80%, 36Hz and 80%, respectively. The values of corresponding cleaning efficiency are 88%, 84% and 88%. The verification test of Chinese cabbage seeds in the real machine was designed, by comparing the cleaning performance of simulation with test, found that the results of simulation and test were consistent, which proves reliability of gassolid twophase flows model in separation chamber. The study provides reference for design and optimization of the separation chamber of seed airscreening machine.

Abstract:No customized fertilizer machines are widely applied in tea fields and traditional spreaders for field crops are constrained by the narrow row spacing of tea trees when used for tea fields. According to the row spacing of tea trees and the characteristics of fertilizer, fertilizerpushing blades were deployed away from the center of the centrifugal plate with their adjustable offset angles, and the horseshoeshaped outlet was adopted. A dynamic model of the fertilizer particle’s movement on the centrifugal plate was established through force and kinetic analysis. With orthogonal test design and central composite design in Design-Expert, the fertilizer spreading process was simulated with EDEM based on a discrete element model. A regression equation of the relationship between variation coefficient of fertilizer particles’ distribution and spreader forwarding speed, blade number and blade offset angle was obtained, and the order of the influence of the above factors on the variation coefficient of fertilizer particle distribution was: blade number, forwarding speed, blade offset angle. The influence of the interaction between blade number and offset angle on variation coefficient was significant, while the influence was less for the interaction between forwarding speed and blade offset angle. It is found out after regression analysis and optimization that the variation coefficient decreased to the minimum of 6.12% when blade number was 5, forwarding speed was 0.6 m/s and blade offset angle was 13.44°. The validation experiment showed that the average relative error between the measurements and the predictions was 11.18%. Therefore, the EDEM simulation model could be used to optimize operation parameters of a centrifugalplate fertilizer spreader, and achieve the expected spreading uniformity in tea fields.

Abstract:In order to improve the upright degree and reduce the damage in the process of transplanting for the film transplanting machine, a crankchute planting mechanism was designed and the mathematical model of this mechanism was built. The optimization program of mechanism was programmed on the base of the model with the Matlab software, and the influence law of the key parameters of this mechanism on the trajectory of the planting point was analyzed. The upright degree was chosen as the optimization indicator, which is, the insert point and the leaving point is perpendicular to the soil ridge as much as possible and these two points should be close to the planting point as much as possible. With the optimization program, a group of optimal parameters of this mechanism were obtained, that means, the velocity of the machine, which was 500mm/s, the length of different bars including L1=150mm, L3=120mm, L4=310mm, L=680mm, different angles including θ1=10°,θ3=15°, θ=20°, and with these parameters the trajectory of the planting point was γ，which was beneficial to the seedling to be upright and had less damage to the film. The experimental prototype was manufactured according to the optimal parameter, the field experiment was done with the tobacco seedlings chosen as the experiment object, the experiment result showed that the upright degree was above 93%，and the damage rate of the planting mechanism on the film can be diminished to 8%.

Abstract:On the basis of analyzing the defects and shortcomings of the existing sugarcane harvester feeding system, simulation analysis and experimental research has shown that the improvement of gearbox of feeding system is helpful to ameliorate the knife dish plugging problem in the sugarcane harvester. The structure improvement of feeding system was mainly carried out with respect to the functional characteristics of the gearbox. The gearbox was changed by feeding roller, and the shafts of two cutters were driven by a pair of reverse synchronous rotating hydraulic synchronous motor. The improved feeding system can expand the logistics channel of cutting transmission mechanism. Meanwhile, the negative sliding frictional resistance the gearbox has on sugarcane was converted into positive rolling frictional driving force produced by the feeding roller. The trapezoidal tooth on feeding roller can not only play the role of clamping and conveying sugarcane, but also envelope sugarcane and increase the contact surface between the sugarcane and feeding roller, which increases the dynamic friction of sugarcane. 3D graphics software SolidWorks was used to modeling, then the improved model was imported into simulation software ADAMS for motion and force analysis. The results show that the improved feeding roller can shorten the retention time on screw conveyor by 359%, as well as reduce the force exerted to the sugarcane by 86% compared to gearbox. That is to say, the sugarcane was more easily to skid into the logistics channel, and the conveying speed is faster with backward transport distance farther. The transmission performance is significantly improved, which can effectively suppress the feeding system plugging problem and play a disproof role of the test about cutter motor pressure measurement. The simulation experiment also shows that the retention time of the sugarcane on the screw was reduced relative to the speed of the feeding roller, and the amount of time of 150r/min speed was shortened by 20% compared to that of 250r/min speed. And the times that the feeding roller applied to the sugarcane was reduced relatively and the radial force exerted to the sugarcane was reduced significantly. Therefore, an appropriate increase in the feeding roller speed can improve the transportation quality of sugarcane and reduce the blocking rate of sugarcane harvester, which can provide a reference for improvement of cutter structure and position parameters.

Abstract:In order to solve the problems of halfway separating and high losing rate of the cyclone separation system, material movement analysis was done by using of highspeed photography. The wheat and mixture of stalk were chosen as the experiment objects, statistical experiment was carried out when diameter of air pores, rotating speed of the fan and rotating speed of the winnower were chosen as the experiment factors and cleaning rate and losing rate were chosen as the experiment indicators. Single factor experiment result showed that the arrangement of the air pores had effect on the cleaning ability. When the arrangement of the pores was spiral, the system performed better. The cleaning rate was increased first and went down later with the increasing of the rotating speed of the fan, winnower and the diameter of the air pores. The losing rate was increased with the increasing of the rotating speed of the fan, winnower and the diameter of the air pores, the value of losing rate was no more than 2%. Multifactor experiment result showed that when the rotating speed of the fan was 1900r/min, the rotating speed of the winnower was 1100r/min and the diameter of the air pores was 8mm, the cleaning system worked better, the average value of losing rate was less than 1.5%, which was reduced by 25% compared with the former.

Abstract:In recent years, with rapid growth of potato planting area, potato has become the fourth largest food crop and the largest noncereal food. Potato plays an important role in solving the problem of food security in developing countries. In view of potato massive planting situation, it is very important to solve the problem of the use of potato haulm before the harvest. At the present stage in China, the main way of dealing with potato seedling or burning is using chemicals which leads to the increased burden on the environment. It is a waste of resources with vine abandoned or burned, as the potato vine is rich of nutrients, and do not meet the requirements of the sustainable development of agriculture in China. Cutting treatment of potato haulm before the potato harvest can not only reduce the potato harvesting machine failure rate and power consumption, but also very much conform to the agronomic requirements. Potato machinery cut haulms can make potato tuber skin aging that can make it easier separate from vine. After cutting haulms, potato tuber can significantly reduce the mechanical damage because of harvest, transport and storage. So that cutting seedlings before the potato harvest has a great role in promoting to improve the quality of potato and the potato harvest efficiency. Currently available machines for potato haulm cutting effect is not very ideal, and there are some problems such as poor breaking length qualified rate, high rate of tuber and soil severe adhesion in the shield, and so on. In order to solve the problems above, this paper presented a potato haulm cutter. This article described the main structure and working principle of the machine. The experiment was carried out with the combination design of orthogonal and quadratic regression equation for the flail. The influence factors of field experiment included rotational speed of knifecylinder, forward speed and distance between knife on ridge and ground. Evaluation indices included break length pass rate, stubble height and the potato carrying rate. The Design-Expert software was used to analyze and optimize the test results, and to obtain a better combination of factors. According with the comparison with the potato professional standard validation, the superiority of this haulm cutter was verified. Results indicated that: the performance of cutting haulm was improved because of the design of structure parameters of flail and the shield eccentric arc structure could reduce the soil adhesion. The field test showed that when rotational speed of knifecylinder was 1500~1600r/min, forward speed was 4.5~6.0km/h and distance between knife on ridge and ground was 50~52mm, break length pass rate was 94.7%~95.5%, stubble height was 56.0~59.9mm and the potato carrying rate was 0.15%~0.23%. The research provided a solution of the potato haulm cutter to soil adhesion serious, low breaking length, qualified rate and high stubble height after cut the haulm. The study provided a solution during cutting the potato haulm and provided the reference for further research of potato haulm cutter.

Abstract:Deepfertilization technology of liquid fertilizer is a kind of agricultural technology which can apply liquid fertilizer accurate quantitatively in deep soil near the roots of crop according to the distribution characteristics of soil nutrient and crops. A type of picking hole mechanism of deep liquid fertilizer with planetary Bezier gears that was designed by using a fitted Bezier curve as a noncircular gear pitch curve was proposed. Taking picking hole mechanism as the research object, a dynamics model was established, thus, the variation law of force both on axle centers and meshing points of gears in a working cycle due to the changing of the rotaryangle of planetary carrier was obtained using Visual Basic software. Soil bin dynamics test bench was also set up. Dynamics properties of picking hole mechanism, spray fertilizer needle and bearing were determined with rotary speed of 40r/min, 60r/min and 80r/min, moving speed of soil bin of 0.8m/s and soil firmness of 0.4~1.0MPa. Experimental results show that vibration of picking hole mechanism was increased with the increase of rotary speed of planetary carrier. With the 180° rotation angle as the center, the reaction force of bearing was symmetrically distributed. The test results were consistent with theoretical analysis, which verified the correction of theoretical models and the feasibility of test method. This research provides a theoretical foundation to dynamic balance control of the liquid fertilizer applicator during highspeed operation, and lays a foundation for the further design of high speed and lightduty machine. 

Abstract:The chosen of lateral layout is the basis of hydraulic design of microirrigation laterals. A simple and easily adaptable analytical approach was developed for the hydraulic design of microirrigation laterals laid on uniformly sloping grounds based on the appropriate layouts. Two indictors for comparing the emitter flow variation and inlet working pressure head from the paired layout and single downhill layout were proposed based on the analytical models of microirrigation laterals. By evaluating the effects of microirrigation laterals layouts on the emitter flow variation and working pressure head, the application condition for paired layout was suggested as the best manifold position is not less than 0.13. When the best manifold position is less than 0.13, the microirrigation lateral was proposed to use the single downhill layout in order to save the extra cost of material and installation from the paired layout. The design procedure for hydraulic design of microirrigation laterals was revised by considering the determination of appropriate layout. Two design cases covering various conditions indicated that the best manifold position criterion for determining the appropriate layout is more effective than the value of ground slope proposed by Keller method. The proposed approach could produce accurate results for practical purposes. This research could provide valuable information for improving the hydraulic design of microirrigation systems.

Abstract:Water erosion process is the interaction between erosion force of rainfall and runoff and soil resistance under the various factors, especially the vegetation plays a signification role, therefore, a better understanding of the effects of different raindrops and runoff characteristics on soil detachment of ground cover hillslope is basis to research soil erosion dynamics processes. A slope soil detachment experiment was conducted to reveal the slope erosion dynamic mechanism of herbs coverage. There erosion plots (0.5m wide×2m long) which were composed of upslope sink (1.5m long) and downslope soil box (0.5m long) with average coverage of 0, 20%~30%, 50%~60% and 80%~90% were installed. In order to research the quantitative influence of herbs structure on soil detachment rate and erosion dynamics, the experimental treatments separately measured the detachment effect of rainfall and runoff on slope soil. The results showed that the effect of herbs structure on soil detachment was different, and sediment reduction rate of roots was higher than the canopy （P<0.05). For two kinds of experimental herbs, the raindrops retardation coefficient of Artemisia carvifolia canopy is higher than that of Setaria viridis (L.) Beauv. canopy（P<0.05), and the sediment reduction effect of roots is the opposite, the sediment reduction rate was decreased by 57.79%~74.74% and 62.87%~81.21%, respectively. This is mainly related to leaf area index and fibrous root content, and root length density and soil detachment rate present index function relation. Comparing with the soil detachment resistance characteristics, for the slope of herbs coverage, granule resistance and wave resistance were increased with the increasing vegetation coverage. The slope soil detachment dynamics mainly includes the rainfall and runoff, the herbs coverage on the influence of rainfall and runoff erosion dynamics are 189.21~698.92J·mm/(m2·min) and 6.27~20.38kg/(m·s2), respectively. The reduction coefficients were 22.75%~84.04% and 19.68%~63.97%. This study reveals the important effect of ground cover on soil detachment from dynamic mechanism, aimed to provide basis research on the hillslope erosion dynamics.

Abstract:Straw mulching of farmland is a main method to reduce soil erosion and to improve water retention. However, overmuch straw mulching may lower the antiblocking capacity of notill planter, which is important to production efficiency and seeding quality. This research aims at discussing the influence of maize straw mulching on infiltration and sediment yield process under different soil texture conditions, and concluding an appropriate straw mulching rate for the optimization of notill planter performance as well as the conservation of water and soil in the conservation agriculture research areas of north China. A rainfall simulation experiment was carried out from October to November in 2014, and the experimental field was located at Experimental Station of China Agricultural University, in Zhuozhou City, Hebei Province, North China. The runoff monitoring site was designed as a Vshaped symmetrical distribution, composed of six experimental plots. A UGT runoff measuring device made in German was installed to monitor the runoff and sediment yield process, and maize straw was collected cut off (less than 100mm) after maize harvesting (early October). Two kind of soil type (sandy soil and loam soil) and five kind of straw mulching rate (0, 10%, 20%, 30%, 40%) were considered as two independent variables in experimental design (three repeated). Each simulated rainfall lasted 1h. The impacts of maize straw mulching on infiltration and sediment yield were analyzed. The results indicated that straw mulching delayed runoff time, enhanced infiltration, and reduced soil loss. Specifically, 30% straw mulching treatment significantly enhanced accumulative infiltration by 25.7%~33.9%, reduced soil loss by 22.2%~46.4%, compared with no mulching treatment. The experimental results also showed that the erosionresistance of soil under different texture was different: under a 1h simulated rainfall with 80mm/h rainfall intensity, the steady infiltration rate and accumulative infiltration in loam soil were 0.02mm/min and 5.9mm less than that in sandy soil condition, and the corresponding total sediment yield was less by 1.364g compared with sandy soil. Although 10% mulching treatment under sandy soil condition reduced soil loss significantly, the total sediment yield was much greater than that of loam soil in 10% mulching treatment. So least straw mulching rate of 30% was recommended on farmland surface in sandy soil and loam soil of north China, comparing the water and soil conservation effect of straw mulching under different soil texture conditions. However, in conservation tillage fields, over mulching (>80%) may lower the antiblocking capacity of notill planter, and thus affected seeding quality and grain production in north China. In conclusion, in conservation tillage system of sandy soil and loam soil planting area, 30%~60% maize straw mulching (1600~3000kg/hm2) is recommended to achieve high performance of planting and high efficient soil and water conservation, which provides the valuable information for suitable straw mulching rate of maize in north China during the application of conservation tillage practice.

Abstract:Super absorbent polymers (SAP) can absorb water up to a few hundred or even a few thousand times of their own mass. Their special physical structures, unique chemical compositions, and characteristics of high water absorption capacity allow super absorbent polymers to be widely used in agriculture, forestry and other industries to relieve drought and reserve water for farmland, afforestation and crop yield improvement. However, the ways of super absorbent polymers applied is an important factor to evaluate．In order to explore the effect of SAP application ways on microecological environment in rhizophere soil of Platycladus orientalis, a pot experiment including five treatments, i.e. CK (neither fertilizer nor SAP was applied), U (urea was applied alone), S (SAP was applied alone), SUM (SAP was mixed with urea) and SUG (gel was made of SAP and urea) was performed. The experiment was to evaluate the effect of different ways of SAP application on enzyme activity and microbial functional diversity in rhizosphere soil as well as growth of Platycladus orientalis. Results indicated that in comparison to U treatment, the SUG treatment significantly increased total amino acids, total organic acids and total sugar in the root exudates. The activity of catalase enzyme, urease enzyme, polyphonic oxidase enzyme and invertase enzyme was also improved by SUG treatment, showing the urease enzyme activity was increased by 29.53%, 14.88%, 27.81% and 7.82% compared to the treatments of CK, U, S and SUM, respectively. At the same time, the values of AWCD and indexes of Shannon and McIntosh were significantly higher in the SUG treatment than in the other treatments, while the Simpson index was decreased by the SUG treatment, indicative of 28.78%, 30.22%, 26.91% and 8.39% increases in Shannon index over the treatments of CK, U, S and SUM. Additionally, the SUG treatment obviously promoted the growth of ground diameter and plant height, and had significant differences with other treatments. However, in S and SUM treatments, less effect on soil enzyme activity and microbial diversity was observed than in SUG treatment, which indicated that the gel way could significantly improve the drought adaptability of Platycladus orientalis compared with the ways of SAP application alone and mixture of SAP and urea. As a result, the gel was beneficial to improve the microecological environment of rhizosphere soil, enhance the ability of drought resistance and promote growth of Platycladus orientalis.

Abstract:Field plot experiment was carried out to investigate the effects of gravel mulching degree on soil moisture dynamics, water consumption characteristic， crop yields and water use efficiency in the whole growth period of summer maize and winter wheat in the crops rotation. The results showed that gravel mulching can hold soil water storage and suppress evaporation, the increase of gravel mulching degree could improve soil storage ability for precipitation and irrigation, compared with CK, and the water storage capacity is mainly reflected in the 0~40cm soil layer, followed by the 40~100cm soil layer water storage, 100~200cm soil water storage did not change obviously. The gravel mulching improving soil water storage ability was observed mainly at seedling stage of summer maize and jointing stage of winter wheat in the crops rotation system, and the gravel mulching degree of 8kg/m2 increased the soil water storage by 12.77% and 6.63% compared with CK respectively, and the effects was weakened because of the increased canopy and rainfall. The total water consumption was decreased during growing period approximately，and the water consumption coefficient was decreased with gravel mulching degree in the crops rotation systems. The water consumption percentage in each stage was increased with the increase of gravel mulching degree besides the period before jointing. Gravel mulching treatments significantly improved the WUE and PUE of summer maize and winter wheat. In the growing period of summer maize, WUE  and PUE were increased by 33.05% and 26.65%, and the winter wheat were increased by 12.68% and 20.00% respectively. In addition, gravel mulching treatments, compared with CK, could significantly increase economic yields and biomass yields. In the growing period of summer maize, economic yields and biomass yields were increased by 4.45%~26.66% and 5.81%~25.78%,the winter wheat were increased by 2.06%~15.34% and 2.32%~26.49%, respectively.

Abstract:Energy is the base of economic and social development. As a kind of renewable new energy, biological energy has been recognized as a major energy in future world. Pyrolysis is a kind of important method for biomass energy conversion and utilization, and how to effectively condense and separate the gas produced in the process of biomass pyrolysis to yield refined biooil has received widespread attention. Preliminary separation and refinement of biooil can be achieved by fractional condensation in the process of pyrolysis, which provides the possibility for further comprehensive utility of biooil and has been proved to be the best economic method. Focusing on the latest research on fractional condensation of biooil, various relatively efficient fractional condensation devices were compared and analyzed, and the physicochemical properties of the product were analyzed and summarized. Seen from the current research results, by controlling reasonable temperature and selecting appropriate condensing medium, multistage condensation device has achieved preliminary hierarchical collection of biooil. As for heavy components of fractional condensation, their low water content and high heating value and less small organic molecules make biooil more stable, and lead to its physical and chemical properties and components are similar to fossil fuel. So heavy components obtained by multistage condensation can be used as industrial combustion directly or crude biooil after further refinement, which is the main alternative to traditional energy. The light components of fractional condensation can be used to agricultural production. Both heavy and light components can be used to extract chemical raw materials with high quality. Meanwhile, due to the complexity of biooil components, the mechanism of the condensation is very intricate and there is no consistent discussion and recognition, so the mechanisms of the condensation deserve further study. Furthermore, the components and physicochemical properties of biooil obtained by fractional condensation can also be influenced by other factors such as the type of material, the reaction devices and the reaction conditions. So far, the research on fractional condensation is confined only to experimental stage and still far from widespread application. Biooil with different components obtained by fractional condensation can’t be utilized until further refinement, so the research of fractional condensation has a long way to go.

Abstract:Many straws and wastes should be treated effectively every year in China. The improper treatments of these wastes have caused severe environmental pollutions. At the same time, with the growing energy demand of the word, biomass conversion technologies have attracted considerable attention because they effectively convert biomass into renewable energy products. It’s found that the biochar, as the main product of pyrolysis technology, could improve the properties of the soil and stay for a long time in the soil. The biochar has a good prospect working as the soil amendment, but difficult to transport, storage and use directly. Therefore, molded biochar was necessary and it could be used as the fertilizer carrier. The biocharbased urea fertilizer can reduce nutrient release rate and improve efficiency of fertilizers, as well as environmental benefits of soil. Thus, the ethanol and wood vinegar were chosen to dissolve the lignin which were used as adhesive during preparing the biochar coated urea fertilizer. The properties of biochar coated urea with different lignin adhesive were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), viscometer and differential scanning calorimety (DSC) methods. The universal testing machine and homemade leaching equipment were used to analyze the biochar coated urea’s mechanics and slowrelease property. The experimental results showed that there is no obvious chemical reaction in the two solutions, and the ligninwood vinegar adhesive had a better surface properties and the viscosity value is 300% higher than ligninethanol adhesive. Comparing with the biochar coated urea of different adhesives, it is found that the ligninwood vinegar adhesive biochar coated urea has a higher coated and granulation rates which are up to 269.4% and 94.83% respectively; the particle size distribute uniform and qualified rate is almost up to 80%; the mechanics and slow release properties are superior too. Hence the ligninwood vinegar adhesive had a better performance on the viscosity and surface properties than ligninethanol adhesive, which is more suitable for the preparation of biomass carbon coated urea.

Abstract:Seed germination index (GI) is a key indicator of plant toxicity and maturity for composting. A combined aerobic composting experiment was carried out in a selfdeveloped intelligent aerobic composting reactor system. The main materials were poultry manure digestate and pig slurry. The wheat straw and mushroom substrates were taken as bulking agents. Based on the obtained data of GI and the basic physicochemical parameters (volatile solid, VS; hemicellulose, HC; total carbon, CT; total nitrogen, NT; the ratio of total carbon to total nitrogen, CT/NT; lignin), Pearson correlation analysis and regression modeling were developed. The results showed that there were significant correlations （R≥0.83, Sig. was 0.000) between GI and the total volatile solid, total carbon, total nitrogen, hemicellulose and lignin contents on a dry basis, respectively. The unitary and binary linear models constructed had good degree of fitting （R≥0.81, Sig. was 0.000). The values of R and SEP of unitary linear models were (0.88, 9.75), (0.88, 10.32), (0.82, 12.73), (0.81, 12.77), (0.91, 8.23) and (0.91, 8.74) based on VS, HC, CT, NT, CT/NT and lignin, respectively. And the values of R and SEP of binary linear models were (0.92, 7.48) and (0.93, 7.58) using CT-NT and HClignin. In all calibrations, modeling using CT-NT as binary variables （R was 0.92, SEP was 7.58) had the best prediction efficiency. This study provides a methodology to support the rapid prediction analysis of GI. Although binary modeling using CT-NT had the best prediction efficiency, it was limited by the aerobic composting reactor volume and the number of samples obtained. Therefore, expanding the sample size should be needed to improve the model accuracy in the further research.

Abstract:In order to improve the efficiency of biogas fermentation and biogas yields, the influence of different phosphorus potassium powder as the functional catalysts of biogas fermentation on anaerobic fermentation of cow dung was explored. Eight treatments were contained as follows: no addition（CK）, the addition of 2.5%（T1）, 5.0%（T2）, 7.5%（T3）, 10.0%（T4）Yunnan microcrystallization phosphate powder, 5.0%（T5）Henan microcrystallization phosphate powder, 5.0%（T6）Yunnan common phosphate powder, and 5.0%（T7）Henan microcrystalline muscovite rock. Results indicated that: with the increase of microcrystalline phosphate powder concentration, the ultimate production of biogas was improved significantly. Adding 7.5% microcrystallization phosphate powder results in the fastest anaerobic fermentation starting, the most biogas yield, and CH4 volume fraction was up to 62.5%, the removal rate of VS reached 61.99%, the chemical oxygen demand (COD) was 4871.4mg/L, the volatile fatty acid (VFA) was 469.9mg/L respectively. As microcrystalline phosphate powder concentration was increased as high as 10.0%, the ultimate accumulative biogas production was inhibited to 317.63mL/g. Adding microcrystallization phosphate powder of 7.5% was considered as the appropriate amount to improve the anaerobic digestion of cow manure. The microcrystalline grinding technology enhanced the nutrient release from the phosphate rock. Thus, it was significant to exploit and utilize the phosphate rock. This study provided a theoretical basis for developing a high efficient biogas catalysts formula and sustainable agriculture.

Abstract:Energy grass, as the second generation of new energy crops, has a brightly development prospect. Five kinds of energy grasses were selected as the raw materials. Their physicochemical characteristics were investigated together with the biogas production performances of anaerobic digestion in the process of laboratory scaled batch anaerobic fermentation at mesophilic temperature(35℃). And the dynamics of cumulative biogas production was analyzed. The results indicate that these energy grasses have good performances for the biogas production. But there are great differences in the relationship between the biogas production performances and the energy grass properties. The biogas yield and the lignin content are in a negative linear correlation, it means the lower is the lignin content of raw materials, the better is biogas production performance. The lignin content of Hybrid Pennisetum(24.88%) is higher for its long time growth, so it has a worse biogas production performance and the specific methane yield is only about 26.95% of the theoretical methane production. While the lignin content of Pennisetum purpureum cv.Huanan is lower, it has a better anaerobic digestion performance: the cumulative biogas yield, methane yield and methane content are 379.58mL/g, 228.55 CH4mL/g and 60.21%, respectively. By fitting the cumulative gas production curve, it was concluded that the energy grass digestion process of cumulative biogas production could be appropriately described by the modified Gompertz equation. This study provides a reference for the development and utilization of different energy grasses.

Abstract:Delignification is crucial in the energy utilization process of lignocellulose materials. In this study, efficiency of biological pretreatment of corn straw using different carriers of precolonized fungis, including Trametes versicolor, Trichoderma chromospermum, Trichoderma atroviride and combined fungi (T. versicolor + T. chromospermum, T. versicolor + T. atroviride) was investigated under unsterilized condition. Results showed that nearly negligible lignin degraded in the process of direct fungal pretreatment of unsterilized corn straw within 30d. It seems that inoculum of fungi cannot compete to the indigenous microorganisms of unsterilized corn straw, resulting in low lignin degradation rate. However, the degradation rates of 34.0%, 38.1%, 38.1%, 39.1% and 40.3% lignin in the sterilized corn straw were observed after 30d of cultivation by T. versicolor, T. chromospermum, T. atroviride, T. versicolor + T. chromospermum and T. versicolor + T. atroviride, respectively. To decrease the cost of sterilization, corn straw was pretreated by T. versicolor + T. atroviride and T. versicolor + T. atroviride with 1∶9, 1∶4 and 1∶1 of the ratio of precolonized carrier and substrate for 30d. During T. versicolor + T. chromospermum and T. versicolor + T. atroviride, pretreatment with an inoculum/substrate ratio of 1∶9, 1∶4 and 1∶1, the degradation rate of lignin were 30% ~ 40%. Therefore, precolonized carrier inoculum is an effective pretreatment method to decrease cost due to precolonized carrier can adjust the unsterilized condition and degrade lignin effectively. 

Abstract:The characteristics of both the piston stamping forming machine and the die roller briquetting machine were combined. The piston stamping forming machine has low energy consumption and low productivity while the die roller briquetting machine has high productivity and high energy consumption, a new kind of roller briquetting method was put forward, and the prototype was designed and manufactured. Compared with other same type briquetting machine, a series of plungers distributed on the roller mesh into the ring die holes in the briquetting process, which could avoid the loss of energy consumption and the serious wear problem in the process of biomass materials squeezed outside ring die holes. In order to test the property of this briquetting machine, the orthogonal experiment was preceded. Results showed that the optimal processing parameters for the roll briquetting machine with plungers: the length to diameter ratio of forming mould is 525, the spindle speed is 47.25r/min, and the moisture content of raw material is 15%. Under the optimal processing parameters, sawdust was used as raw material for the briquetting test. Experimental results showed that the diameter of the forming particle is 10mm, the density of forming particle is 1.15g/cm3, the mechanical durability is 96.28%, the productivity of the briquetting machine is 75kg/h, the energy consumption is 56kW·h/t, the forming rate is 95%, and the working noise is 79dB. All the indexes meet the design requirements, and realize continuous and stable production. This has a certain role in promoting the development of biomass curing technology, and the briquetting method put forward in this paper provides the reference for the biomass densification technology and the development of the same kind equipment.

Abstract:The freezingthawing phenomenons of fruits and vegetables are inevitable during the refrigerated transport process. The quality of fruits and vegetables will also be changed. Grapes as test objects are used to test the quality change during the freezingthawing process. The cryomicroscope system (including CCD camera, BCS 196 cryostage, the liquid nitrogen tank, the crystage temperature control system) was used to test the grape sample during the freezingthawing process. The temperature range of cryomicroscope system is -196℃ to 125℃. The crystallization change of grape cells has been researched. The freezingthawing rate is 2,6,8,11,14,20,50, 90℃/min. Micrograph, volume, internal pressure and permeability coefficient of grape cells were analyzed during the freezingthawing process. The result shows that the formation process of crystallization in the intercellular space depends on the freezing rate. Grape cell freezing temperatures will decrease with increasing freezing rate and the general trend of change in volume of grape cells will decrease with the decreasing of temperature. However, grape cells volume will increase at -5~0℃ due to the volume changes of intracellular free water. Grape cells volumes were reduced by 54.5%, 26.3% respectively at 14℃/min and 50℃/min freezing rates. The larger the freezing rate is, the smaller the cell volume changes to be. During the freezing process, the permeability coefficient of grape cells will decrease with the decreasing temperature and freezing rate. Increasing thawing temperature can effectively reduce the damage of the grape cells during freezingthawing process. This research will optimize the temperature gradient of fruit and vegetable during cold storage.

Abstract:In order to investigate the characteristics of temperature decreasing of litchi fruits with packages during precooling in a cold room, a twodimension numerical model was built based on the test platform with controlled atmosphere for fruits and vegetables. According to the thermophysical properties of the package, litchi fruit and the platform, the process of the temperature decreasing of litchi fruit during precooling was simulated by Fluent, after which the airflow information in the container and package were obtained. After that, some results can be drawn. Improving the ventilation velocity can shorten the process of precooling but will improve the variable coefficient of temperature among litchi fruits in the package; When the air duct velocity is bigger than 6m/s, the cooling rate trends to be steady along with the growing of air duct velocity, the variable coefficient was steady at roughly 0.25; Reducing the air temperature on the partition outlet can effectively improve the temperature decreasing of litchi fruits during precooling but also will improve the variable coefficient of temperature among litchi fruits in the package. A test was done to verify the accuracy of the model, and it found that the simulation values and experimental values are in good agreement, the average difference rate (MD) is 1.91%, and the rootmeansquare error (RMSE) is 2.34%. Such results of this research reviews some characteristics of the precooling of litchi fruits with packages in a cold room, which can provide a reference value for the optimization of the equipments and technologies for litchi fruit.

Abstract:Microwave can stabilize the quality of wheat germ rapidly and uniformly with the advantages of losing nutrition minimally. To investigate the mechanism of microwave on the stability of wheat germ, the dielectric properties (ε′ and ε″) of wheat germ were studied under different frequencies, water contents, fat contents and salts, including sodium, potassium, magnesium, calcium and iron ion. The results showed that, when the frequency was 915MHz, ε′ is slightly higher than that at 2450MHz, while ε″ was less than that at 2450MHz significantly. When water content is 16%, with frequency changes from 915MHz to 2450MHz, ε′ was decreased from 4.91 to 4.32, and ε″ was increased from 0.33 to 0.80. As water content of wheat germ increasing, the dielectric properties of wheat germ were increased significantly. When the water content was increased from 4% to 16%, the ε′ was increased from 2.61 to 4.32, and ε″ increased from 0.02 and 0.8, respectively. Fat content had little effect on the dielectric properties of wheat germ, particularly has no effect on ε″. Among the five salts, adding NaCl can increase ε′ and ε″ of wheat germ. Especially when NaCl concentration was 1%, ε′ was increased slightly while ε″ was increased apparently from 0.8 to 1.3, which can enhance enzyme inactivation effect of microwave.

Abstract:The behavioral information on individual animal has a considerable relationship with animal’s welfare and diseases. Thus, perceiving animal information and behaviors are fundamental to precision livestock farming. A research review of respiration detection, locomotion score, body condition score, individual identification, behavioral analysis,etc. were summarized focusing on large animals,including cows, pigs, sheep， which are prevalent instock farming industry. And a summary of the advantages and disadvantages of different methods applied in all the aspects was presented in this review. In term of individual information acquisition and analysis(e.g., individual identification and body condition score), solutions based on 3D camera and depth image processing technolygy were emphasized, because such cameras were more robust to the environment when extracting the animal target from the image. In addition, locomotion score was one of the most important topics in precision livestock farming. Electronic sensors, audio recorder and digital cameras were used to perceive the individual information and prove feasible to detect the animals’ lameness automatically. Because of the earlier lameness detection requirements of practical application, the pathology of the limbs and hooves disease, the automatic trauma detection and universal parameters of lameness without scoring system should be considered in the future. In the behavior analysis aspect, some new research approaches were emphasized including the limb segmentation algorithm and the combination with human behavior analysis theory and method. Considering the development trend and requirements of practical application in precision farming, animals’ social behavior should be considered. The precision live farming should also consider the effectiveness, robustness and the stress to animals of the detection equipments, continue to move in contactless, high precision and automation direction.

Abstract:With the increase of event flow generated from sensor kind electronic devices in IOT(Internet of things) and increasing demand of matching accuracy/confidence of more complex events, uncertain complex event processing is becoming more and more been concerned. A large number of RFID or sensor monitoring data exist in precision agriculture, but current hardware and wireless communication techniques cannot support 100% confident data. One stream processing engine which can process uncertain data in precision agriculture is needed. In this paper, a new type of complex event processing engine PUCEP(Provenance uncertain complex event processing) was proposed, in which probability flow theory and data provenance management theory were added based on the existing flow processing engine SASE. Sufficient approximate lineage query algorithm is used to calculate the probability of an event in order to improve the efficiency of probability calculation of large amount of data and the pattern matching was carried out by using the two fork tree and NFA. This optimized method can not only calculate the probability of outputs of compound events but also improve the matching efficiency of uncertain complex events, thereby reducing the computation cost and response time to a realistic degree. The experiment uses sensor data acquired from an agricultural greenhouse and shows that this method is efficient in processing complex events over probabilistic event streams.

Abstract:To build a stable and effective internet of things system of pig breeding, coverage rate and connectivity of wireless sensor network are two key problems for node deployment. Obstacles have some effects on the wireless communication. The pig farm was used as an example for modeling and the piggery wall was considered as the obstacle. The sensor node’s communication radius was decreased with the logdistance path loss model when obstacle was blocking the wireless signal. To improve the coverage rate in situation of obstacles with particle swarm optimization (PSO) algorithm combined with virtual force was the aim. Besides, PSO algorithm can find the best positions in the network to add extra nodes for improving connectivity until all nodes get together. Matlab was used to do simulation experiments; the results showed that the virtual forcedirected PSO algorithm has good performance on global optimization and convergence rate. In situation of obstacles and communication radius decreasing, the coverage rate was improved about 15% with only adding 10 nodes, which make the whole network connective.

Abstract:Hybrid rice seeds inevitably produced crackglume of rice husk during the maturation process, so the germination performance of appearing crackglume seed would be affected. These effects included seed vigor reducing, germination potential and germination rate decreasing and seedling quality lessening. So it is of great significance to distinguish and sort out the crackglume rice seeds from rice seeds during the producing and processing. In order to detect the crackglume rice seeds, the acoustic characteristics of the normal and crackglume hybrid rice seeds, which were fell at different drop heights and different spacing distances from tilt glass to microphone by using selfdeveloped acoustic detection devices, were tested. The experiment results manifested that voice voltage amplitude of normal hybrid rice seeds which impacted with glass plate was generally higher than that of crackglume hybrid rice seeds. Optimum drop height for hybrid rice seed was 150mm, optimum spacing distance from tilt glass to microphone was 10mm or 20mm, under maximum comprehensive identification rate condition. The comprehensive identification rate of Liangyou 108 hybrid rice seeds reached 94%, the comprehensive identification rate of Xin Liangyou 6380 and Liangyou 6326 hybrid rice seeds reached 88% and 92%, respectively. The average identification rate of normal, crackglume hybrid rice seed were 92% and 90.67% individually under optimum working condition. The crackglume rice seed could be separated effectively from normal rice seed by using impacting acoustic characteristics of rice seeds.

Abstract:In order to increase the efficiency and robustness of automatic recognition of cucumber downy mildew disease, a disease recognition method was proposed in the fashion of visual saliency. Firstly, image sample of RGB color space was transformed into HSV color space, and a color correction method was performed on the sample image. Then the colorcorrected image was transformed from HSV color space back to RGB color space, and a linear combination of the R, G, B components was carefully chosen to generate visual saliency map of disease area on the leaf image. Finally, based on the visual saliency map, the disease area was extracted from the leaf area of original image. 50 samples for testing were acquired from warm houses in northern Beijing from September to October, 2015. Samples were taken by consumer grade digital cameras and mobilephones with camera module. In order to focus on the problem of disease recognition, original leaf images’ background were removed manually and uniformly fitted into 512 pixel by 512 pixel squares before experiments. Result of testing shows that this method can effectively extract disease area from color image with relatively high accuracy, the average of mis-classification rate is 6.98%, better than Kmeans(11.38%) and OTSU(15.98%); the average running time is 0.6614s, faster than K-means(1.4249s); the RMSE of running time is 0.0515s, robuster is better than K-means. Result also shows that CC(Color correction) method makes better results than original proposed disease recognition method proposed, mis-classification rate was decreased from 8.63%(Saliency method) to 6.98%(CC+Saliency method).

Abstract:Leaf wilting is a common phenomenon in plants. Wilting detection is of high importance for plant precision management. In this study, the 3D image of plant leaf was collected using a timeofflight (TOF) camera to quantificationally identify the degree of plant leaf wilting. The 3D information of targeted leaf was examined by the custom wilting index based on discrete time Fourier transform, in which the leaf is equivalent to a mathematical surface in 3D space. Rapid dehydration and rehydration method was used to make plant leaf state different wilting degrees. The image acquisition experiment was proceeded by a acquisition system based on the seeding of cucumber and zucchini. De-noising, threshold segmentation and dot product were used in image preprocessing after the images were collected, and then the wilting index was calculated. The experiments were divided into three periods, which means, dehydration period Ⅰ, rehydration period and dehydration period Ⅱ, and the trend of wilting index was favorable at each stage. The universality was simulated through the variance analysis of a piece of leaf and different pieces of leaf from the same plant. The significance levels are respectively 0.8904, 0.2922 and 0.9036, which are all larger than 0.05. In general, the feasibility and accuracy of the identification of leaf wilting using TOF camera are verified. As leaf wilting embodys in many aspects because of different kinds of factors, control variate method was used in this paper. The identification of outdoor plant leat wilting needs to be intensively studied.

Abstract:Beijing-Tianjin-Hebei Region is one of the most important developing regions in China, which relates to the national development strategy. The papers purpose is to analyze the fragmentation degree and artificial interference of the cultivated land. The space grid was taken as the basic unit and the density of cultivated land was calculated by kernel density function. And the density zoning was realized by natural breaks method. Then, the spatial distribution characteristics and the fragmentation degree of the cultivated land quantitatively were analyzed by using landscape pattern indexes. Finally, the direction of the consolidation of cultivated land was indicated by making a comparative analysis of the cultivated land fragmentation index and the artificial disturbance index. The results show that, the variation range of the density of cultivated land is 0~95.08points/km2, and more than 85% of the cultivated lands are distributed in the medium to high density region, centrally located in the central and southeastern of the region. The cultivated land area was decreased with the reduction of density value. The patch density, patch edge density, area weighted fractal dimension and the variation of the degree of aggregation in different density zones of the cultivated land all showed that, the fragmentation of the cultivated land was increased with the reduction of density value, but it was decreased with the reduction of density value in different density zones of artificial landscape. Both the degree of fragmentation and the degree of artificial disturbance were increased gradually with the increasing density value of cultivated land. And the human disturbance is the main factor to the increasing fragmentation in the region. Using kernel density function method can reflect the aggregation degree and the change characteristics of fragmentation of cultivated land more reasonably, and it can provide a reference for land consolidation and land use optimization in Beijing-Tianjin-Hebei Region.

Abstract:Target detection is the basic work for analyzing the behavior of the cows using video analysis technology. It is difficult to extract the moving cows accurately and realtimely with the existing target detection methods because of the complex background environment. In this study, a series of improvement measures were proposed based on Gaussian mixture model to meet the system requirements. A dynamic background modeling method with penalty factor was proposed for the mathematical model of the background which can overcome the high model complexity. A twoclass classification algorithm based on chromaticity distortion and brightness distortion was proposed to avoid the influence of the shaded area in the foreground detection algorithm. Local update method was proposed to avoid missing the target if it stays for a long time. In order to verify the validity of the algorithm, four evaluation parameters were introduced to test the detection algorithm including model complexity, false detection rate of foreground, false detection rate of background and processing time. Experimental results show that model complexity was 5085% lower than the classical method. False detection rate of foreground and false detection rate of background were 18.18% and 7.52%, which had 19.50 and 13.37 percent lower than the classical Gaussian mixture model. Processing time of average single frame was 29.25% lower. Statistics indicate that the algorithm proposed in this study can improve the detection performance and it is an extension to classical Gaussian mixture model.

Abstract:In order to decrease the effect of moisture content on the accuracy of tomato nutrition level in the ontime monitoring system and improve the accuracy of nutrition level prediction model, an ontime measurement method for moisture content based on impedance and capacitance of leaf was proposed. A monitoring system of moisture content with four electrodes was designed. The relationship between electric properties and moisture content of tomato leaves was investigated within a frequency range from 1×10-6MHz to 1MHz. The sensitive frequency of 3.98kHz was obtained. Therefore, an equation was developed that simultaneously satisfies both impedance and capacitance. The new method increased the accuracy of moisture measurement as compared to that obtained by using a single parameter. It is suspected that the variation of tissue structure during the growth process of tomato had the effect on electric properties. Therefore, the experimental samples were divided into four classes depending on four growth stages such as strong seedling stage, flowering stage, fruiting stage and picking stage, the samples were reanalyzed. The linear regression equations with the correlation coefficient of 0.973 at least and root mean square error(RMSE) of 5.06% at most for four growth periods respectively were acquired by the least square method. Results showed that the accuracy of model for four growth stages was further enhanced. When the moisture content of leaves was between 50.5% and 94.4%, the logarithmic functions of impedance and capacitance can be used to estimate the moisture content at 3.98kHz.

Abstract:The lactation period is a critical period for sows to breed their piglets, and the specific voice of lactating sows in this period is the most direct expression of their physiology, emotional health, and maternal ability to care for piglets. The rapid location and accurate identification will be more complex due to a variety of vocalizations during this period. Therefore, the vocalizations of nursing grunt, drinking, feeding and sham chewing were observed, and a fine energy calculation for frequency domain with a power ratio as a vector was carried out. Then, the subband clustering method based on skewness was presented to merge the sub bands without significant characteristics to reduce the number of parameters. Thirdly, the recognizer for sow’s vocalizations was built based on support vector machine(SVM) to calculate the duration of the different types of vocalization. A sound mode of successful nursing was established further within single lactation circle. It is shown that the max power ratio frequency domain of the nursing grunt, the sham chawing, the feeding and the drinking are ranged from 0Hz to 1000Hz, 1000Hz to 1500Hz, 1500Hz to 2500Hz, and 2500Hz to 8000Hz, respectively. The accuracy of the vocalization recognition mode with these four sub bands power ratio frequency as parameters were 100%, 100%, 95.17% and 96.61%, respectively. Compared with the uniformlyspaced subband division and principal component analysis (PCA), the number of features was reduced, and the recognition accuracy was significantly improved in the clustering algorithm based on skewness. Thus, the proposed method could be further applied in the health and maternal ability of sows monitoring realtimely and nonstressly.

Abstract:Leaf area index (LAI) is one of the most important structural parameters of terrestrial ecosystems. In recent years, the use of LAI-2200 to measure leaf area index of grassland has gradually increased, but few studies have evaluated the accuracy of the optical method to estimate LAI in grassland ecosystems. In order to validate the measurement accuracy of LAI-2200 for grassland leaf area index, the effective plant area index (PAIe) retrievals by LAI-2200 were compared with the simulated LAI-2200 measurements and the plant area index (PAI) retrievals by destructive sampling in 19 grassland sites. As an additional biophysical parameter of comparable importance to LAI, the clumping index (CI) of grassland was also analyzed. The PAIe retrievals from LAI-2200 4ring data with smaller zenith angle perform better than from LAI-2200 5 ring data, and correspond very well with the destructive PAI values (R2=0.951). Reasonable agreement of the PAIe retrievals from LAI-2200 with the destructive sampling and the simulated results verifies the reliability of LAI-2200 used in sparse grassland. PAIe is slightly less than PAI when PAI is less than 3. As PAI continues to increase, PAIe has been seriously 〖JP2〗underestimated due to clumping effect: CI=0.97 for PAI < 3, CI= 0.88 for 3 6. Therefore, the LAI retrieved from LAI-2200 with the assumption of the random foliage distribution might yield inaccurate results in clumped grass, which need to be corrected using CI values.

Abstract:Immunomagnetic beads separation (IMBS) technique plays more and more important roles in biological detection recently. One of the key technologies for immunomagnetic beads separation is the magnetic nanobead separator (MNS) which is capable of providing a magnetic field of high intensity and high gradient. The innovative MNS was constructed by NdFeB magnetic tile blocks and permalloy clinohedral magnetizers. There are six separation holes on this annular MNS providing with the magnetic field of high intensity and high gradient. The MNS was successfully applied in the field of nanobead magnetic separation on both Escherichia coli and avian influenza virus. The magnetic intensity measurement results show that the highest MNS magnetic field intensity of 1.44T and the highest MNS magnetic field gradient of 96.3T/m (865.5cm3 volume, 4.8kg weight) were achieved. The measurement average relative error among each hole of the four sets of MNS was between 2.0% to 3.3%. The study results also show that MNS volume, material and profile of magnetizer have different effects on the intensity and gradient of magnetic field. The larger MNS or the MNS with permalloy magnetizer or with sidleingmagnetizer can obtained higher intensity and gradient of the magnetic field compared to the smaller MNS or MNS with soft iron magnetizer or MNS with straightshape magnetizer. Therefore, according to different IMBS application requirements, it can be obtained the ideal separator easily with different structure elements.

Abstract:The quantity and spatial distribution of cereal field are important for food security and ecology function, especially in metropolitan area. A new method was presented to design the layout of cereal field in metropolitan area and these factors were accounted for in this method such as the land productivity, the ecological function as well as the geographical location. The first step was to identify the priority assigned region (PAR) and the none priority assigned region (NPAR) according to the properties and the locations of crop lands. If the crop lands were basic farmland and they also were within the region of allowable construction, these crop lands were identified as PAR and the others were identified as NPAR. The second step was to classify the NPAR into the suitable region (SR), the optional region (OR), the unsuitable region (UR) based on the comprehensive evaluation model(CEM). As a case study, this method was applied in Pinggu District in Beijing City to optimize the layout of cereal field. The results were as follow: the area of PAR was 1427.26hm2, accounting for 11.62% of the total cultivated area, and PAR distributed mainly around the urban area and neighboring towns. The area of NPAR was 10850.96hm2 The area of SR was 4450.75hm2, with the evaluation scores higher than 85.17. SR distributed mainly in the eastern region of Pinggu District. The area of OR was 3881.18hm2, with the evaluation scores between 8000 and 8517. OR distributed mainly in the western and southern regions of Pinggu District. The area of UR was 2519.03hm2, with the scores lower than 80.00. UR distributed mainly in the northern region of Pinggu District and the topography of UR is usually mountainous. The layout method of cereal field accounting for “Production-Ecology-Location” in this paper can provide a scientific basis for the grain layout in ecological conservation area of Beijing.

Abstract:The cultivated land quality grading results have played an important role in the protection of cultivated land, therefore, research on the test method of cultivated land quality grading results has important practical significance. The main purpose of this study was to prove the rationality of the cultivated land quality gradating results by testing cultivated land natural quality index. This paper presented an improved model, and it was established with inverse distance weighting (IDW) matrix which was amended by cultivated land area, then suspected outliers of the improved model and the original IDW model were extacted. In order to determine the accuracy of suspected outliers, a further study was carried out to establish a standard for judging and extracting suspected outliers, which included analyzing the standard deviation of cultivated land natural quality index of cultivated land unit, and selecting a distance which is greater than the threshold distance of biggest Moran index as a buffer radius. This new method was illustrated by using Ningcheng County of Inner Mongolia as a case study, the standard deviation was 78 and the buffer radius was 600 m were obtained. The results indicated that the method using standard to judge suspected outliers can accurately judge determined outliers and exclude most nondeterministic outliers. Besides, the improved model was better than the original IDW model on extracting the determined outliers unit in the same threshold distance, which illustrated that both the area and the distance were important indicators of the quality of cultivated land. This method can provide a reference for testing the cultivated land quality gradating results at county level, and also provide a new way for the application of spatial autocorrelation analysis in related fields.

Abstract:Ecosystem services value pressure has different driving factors and shows differences in different regions. Taking Beijing City as the study area, considering the spatial distance and local spatial connection factors, this paper explores the driving factors and spatial heterogeneity analysis of ecosystem services value based on STIRPAT model. The factors chosen in the paper are population, per capita GDP, green rate, the proportion of the third industry, the total energy consumption per capita and urbanization rate. The result shows that, population, per capita GDP, green rate, the proportion of the third industry, the total energy consumption per capita and urbanization rateare the important driving factors that affect the value of ecosystem services in Beijing City, and the green rate is positive, the other indicators have a negative impact on the per capita ecosystem service value, in which, the influence of the proportion of the third industry and urbanization rateare the maximum two factors. The relationship between ecosystem services value and its driving factors is very complicated, so this paper takes geographical space effects into the STIRPAT model, and the driving factors of each district is gotten, By analyzing the driving factors of the ecosystem services value of each district, the influence of the driving factors in different regions of Beijing is great. Generally speaking，the influence of the urban expansion area and the urban development zone is higher than that of the ecological conservation area. Based on quantitative analysis of the driving factors and spatial heterogeneity analysis, the relevant measures to improve the service value of the ecosystem services in different regions of Beijing were proposed.

Abstract:Electro-spraying is an effective technique to enhance combustion of liquid fuel in micro/smallscale. A new combustor using a stainless steel capillary tube with inner diameter of 0.9mm was designed. Electrospraying experiments using ethanol as fuel were carried out under single electric field and combined electric field, and the spraying angels in the spraying region were measured under stable conejet mode. The experimental results found that the spraying angel under the combined electric field was bigger than that under single electric field at the same flow rate of 1.6mL/h. It can be inferred that the ring electrode can enhance the spraying process of ethanol. The space electric field during the electrospraying process was established by the combination of the combined electrodes and space charges. Both the electrode parameters and space charges play great roles in the electric field distribution. According to the uniformly charged ring electric potential and field strength formula, the limited long and thin cylinder was regarded as a set of uniformly charged ring. Based on superposition theorem, the distribution of electric field strength in the spraying region was calculated using ellipse integral method and the relationship between Cartesian coordinates and polar coordinates. The electric field established by the space charges depends on the form of spraying region and the quantity of electric charge. The results show that the electric field strength was an axial symmetry and extremely nonuniform when using the ring electrode only. When keeping the voltage of nozzle as a constant, the electric field strength in the spraying region varies greatly along with increasing the electrode spacing and voltage of ring electrode. The electric field strength from the space charges was also an axial symmetry and extremely nonuiform, which cannot be ignored. Especially near to the steel mesh, the space charge dominated the whole electric field. The electric field strength under combined electrodes was enhanced greatly when comparing with that under single electrode. The selection of suitable electrode spacing and voltage is very important for the form of stable conejet mode. The present study can supply some guidelines for the design and operation of smallscale combustor.

Abstract:In order to effectively realize the damping control and regenerative energy recovery of vehicle suspension, electrohydrostatic actuator (EHA) technology in the aerospace field was introduced into vehicle suspension system and a kind of vehicle semiactive suspension with EHA was put forward. For the following simulation analysis of suspension performance, 2DOF mechanical model of vehicle semiactive suspension and EHA mathematical model were established. The EHA prototypes were designed and developed for test parameters identification and regenerative energy recovery. Then, the characteristic tests of the generator and energy regenerative tests of EHA were completed. The optimal control and energy management control strategies of EHA semiactive suspension were designed. The dynamic performances and energy regenerative characteristics of semiactive suspension with EHA were simulated by AMESim and Matlab/Simulink software. The test bench systems for semiactive suspension were developed. Then, the tests of semiactive suspension with EHA were done. The simulation results show that for semiactive suspension with EHA, sprung mass acceleration drops by 23.97%, suspension dynamic deflection drops by 18.36%, and tire dynamic load drops by 11.50%. And the energy regenerative efficiency is 36.4% under vehicle speed of 30km/h and C level road excitation is 67.4% under amplitude of 0.05m and frequency of 4Hz sinusoidal excitation. The test results show that compared with passive suspension, sprung mass acceleration of semi-active suspension with EHA drops by about 20%. The damping effect of developed semi-active suspension with EHA is obvious.

Abstract:Electronic unit pump system is a type fuel injection system with high injection pressure which can be applied to control fuel quantity and timing of insection flexibly. The solenoid valve in the electronic unit pump (EUP) controls pressure buildup within the highpressure fuel line. When it is open, highpressure fuel transfers with high velocity from the narrow crosssection into the lowpressure fuel line. During its operation, the flow in the field of solenoid valve is quite complex that affects the performance of EUP. In order to study the change characteristics of transient flow fields in poppet valve downstream area during the oil return process of an electronic unit pump injection system, a diaphanous glass window was designed in the pump. Highspeed photography was introduced to visually investigate the transient flow fields. By means of experiment data, extracted the cavitation image boundaries and calculated the brightness of the cavitation bubble clouds, the cavitation periodic time and the change of brightness were analyzed and calculated. The test results show that with the increase of the cam rotational speed, the average cavitation periodic time was decreased almost linearly, and the average brightness was increased gradually. At the idle condition (500r/min), the average cavitation periodic time and the standard deviation of fluctuation are maximum, which are 4.5ms and 0.15 respectively. Furthermore, the simulation was conducted based on the test data such as the pressure and the displacement of valve core. The simulation results of cavitation phenomenon occur along opening process of valve. In the process of reciprocating motion of valve core, several swirling regions appear in the flow field of poppet valve downstream area, and keep constantly changing. The streamlines have significant influence on swirling regions.

Abstract:The paper focuses on the pressure information application of digital pen in sketching system and proposes a novel design pattern based on the direct conversion from the pressure information to the threedimensional stoke depth. The method firstly defines the curve modification region and the pressure scale, determines the stroke influence area of the plana or spatial curve with the simplified method of normal pressure estimation on each node of stroke point. Then the pressuresensitive stoke was smoothly shown with the pressure information by width and color. Finally, the pressuresensitive information was converted to the depth information of a planar stroket in order to create a threedimensional stroke with the endpoint locked and the parabolic pressure conversion methods. The conversion method based on the pressuresensitive digital pen was applied in the new version of automotive threedimensional freehand sketching system. The experimental results show that the pressure information of digital pen can be effectively converted into the depth information of a planar stroke, which can be changed into a spatial curve directly. The calculation time of the conversion was short, and the visualization effect was satisfied obviously. In addition to the application during the concept design phase of the automotive 3D sketching modeling, this conversion can also be applied to mechanical design and other engineering design areas.

Abstract:By controlling the amount of feedback to the corresponding stable platform servo control mechanism to achieve stability control for stabilizing the platform, gyro is used to measure angular velocity of stabilized platform with respect to inertial space and then get the gesture of stabilized platform in inertial space. By analyzing the influence of gyro random error on the stabilized platform accuracy in detail, a processing method for gyro random drift was proposed. Firstly, owing to the values of the parameter α is artificially unreasonable of the Singer model in the field of motor tracking, the parameter of α in real time was estimated adaptively, and a new method of gyro modeling output module directly was established based Modified Singer (MS); secondly, on the basis of the established output model, an improved Kalman filter (IKF) based on interacting multiple model (IMM) was applied to the gyros output random error processing, and the theoretical analysis and derivation of the algorithm were explained in detail. Through numerical simulations and verification experiments of a certain type of gyro stabilized platform analysis, the static filter root mean square error is only 0.0227°/s, and this method was proved to be feasible and effective with the gyro drift treatments；finally, through the dynamic and static steady experiments of gyro stabilized platform, the MS-IMMIKF filtering algorithm was proved to be effective and practical for improving the accuracy of the stable platform. The dynamic and static steady experiments of gyro stabilized platform results show that the accuracy of the stable platform could be controlled within error of 3° and 25° respectively after the MS-IMMIKF algorithm filtering.

Abstract:In order to provide a precise model of dynamic components in the electrohydraulic proportional variable pump and improve the accuracy when design a system, firstly, the mechanical structure parameters of a certain electrohydraulic proportional variable pump were measured and the basic structural parameters of the pump were confirmed. Then a single model of a piston and the model of the proportional flow servo valve and variable pump were built in AMESim software platform according to the actual parameters of the valve and pump. And the whole model of electrohydraulic proportional variable pump was constructed based on the sub models. Through the coordinated control of pressure, flow and proportional valve opening, comprehensive simulation test and experimental verification of the dynamic characteristics of the pump were carried out. The dynamic response of the simulation was consistent with the experimental data, which verified the accuracy of the model. The dynamic response of the proportional flow servo valve spool, the angle of the swash plate and the system pressure could be observed directly in the model. The response speed of proportional flow servo valve, valve opening gain and diameter of control piston in this simulation model were adjusted further so effects of these parameters on the dynamic response of the swash plate were obtained. The results show that the swash plate will response more quickly with bigger valve opening gain, faster proportional flow servo valve response, and smaller diameter of the control piston. However, when the valve opening gain gets too large, the swash plate overshoot will increase and it will affect the dynamic characteristics of the swash plate. In this paper, an accurate simulation model was provided for the theoretical research and engineering selection of the electrohydraulic proportional variable pump. 

Abstract:Under the traditional proportional integral differential (PID) controllers, it is usually not easy to obtain a satisfactory control performance for Buck converters subject to large disturbances. Aiming at this problem, a chatteringfree control method based on the second order sliding mode control was proposed to improve the robustness of the Buck converters. Firstly, the average statespace model of Buck converter was established and the design of the chatteringfree sliding mode controller was associated with controlling the output voltage of the Buck converter by selecting an appropriate sliding mode surface. The control design was accomplished by designing a discontinuous second order sliding mode controller where the derivative of the duty ratio was regarded as a virtual controller. The actual controller was the integration of the discontinuous secondorder sliding mode controller, and thus the chattering problem can be avoided. On this basis, taking a direct discretization on the proposed algorithm by using Euler method, the chatteringfree sliding mode controller can be implemented by the way of fixedfrequency PWM control technique based on a LabVIEW platform. Finally, the reliability and superiority of the chatteringfree sliding mode controller were verified by comparing PID controller through simulation and experimentation. It can be shown that: the system startup time can be shortened by nearly 50%; the variation range of system output voltage is significantly reduced under the conditions of load perturbation and input voltage change.

Abstract:In order to make the simulation model closer to physical prototype, mechanical hydraulic coupling simulation model on axial piston hydraulic motor was established, and the factors including the friction force of cylinder plunger and cylinder block, cylinder plunger and swash plate, the viscous damping of fluid and the triangle damping groove which is to decrease the pressure fluctuation were taken into consideration. Through the high pressure oil of the hydraulic motor pushing plunger to move and mechanical energy driving plunger to discharge oil, the mutual conversion between hydraulic energy and mechanical energy was implemented. The simulation model mainly included the pressure source (constant current source or constant voltage source )，load (external resistance moment), piston and cylinder components, reciprocating and rotating motion transformation components of the plunger, oildistribution port, etc. In the model, cylinder was connected with rigid or elastic locking device. Piston and cylinder surface is simplified to a springdamper elastic sealing unit. In order to realize positive inversion of the hydraulic motor, triangle unloading groove was set in the both ends of the oil inlet and outlet of the valve plate. Through the contrast between simulation result and experimental data from literature, it can be found that the errors of motor speed, acceleration time and maximum flow output are less than 5%. The accuracy of simulation model was testified. According to the simulation result, on account of the flow area mutation of the unloading groove and the waist type slot transitional region, there is a local pressure pulse; and the higher rotational speed is, the greater pressure fluctuation is. The pulsating pressure could be alleviated through improvement of structure and optimization of parameters of the load discharging groove. The performance characteristic of hydraulic motor will be affected by load, when the moment of inertia of load is high, the acceleration time will be long, the fluctuating region of steady rotational speed will be narrow, and the corresponding impulse will be smaller.

Abstract:A new kind of roller thrusttorsion coupling was designed with low friction and simple structure, the linear movement of proportional electromagnet armature can be changed into the rotation of the spool movement, at the same time, the rotary torque of spool was enlarged. With large flow and simple structure, the new kind of 2D electrohydraulic proportional directional valve (EPDV) mainly consists of roller thrusttorsion coupling and electromagnet armature, which has position feedback. Based on the principle of the roller compressiontorsion coupling, the mathematical model was established, and 2D valve was simulated by the software Matlab. Direct and pilot experiment results show that, with good input and output characteristics, the high pressure and large flow control can be achieved by this valve, the noload hysteresis is 1.0%, flow hysteresis is under 5% when system pressure is at 21MPa, and the linearity and repeating characteristic are all good. Frequency width is improved to about 12Hz at -3dB and -90°and rising time of step response is about 0.45s. The valve’s static and dynamic performance is good, and simulation analysis and experimental results are basically same, which lay foundation for its engineering application.

Abstract:Impeller is key functional unit of centrifugal compressor. It is widely used in industrial and agricultural fields and often subjects to damage because of the bad work environment. Since the technology of remanufacturing the impeller has been dominated by foreign companies, domestic companies have to invest a tremendous amount of cost and time in having damaged impeller repaired. This paper is to put forward a method in an attempt to remanufacture damaged impeller based on structure characteristics. Firstly, the process of remanufacturing the damaged impeller was designed. Secondly, the point cloud data of damaged impeller was acquired; the original point cloud data were filtered and simplified reasonably to improve modeling accuracy and efficiency. Thirdly, for the undamaged area of the impeller blade, the SS, PS, LE and TE of the crosssection point cloud were automatically identified, the crosssection curve of the impeller blade was extracted and fitted based on design features; for the damaged area of the impeller blade, the boundary curve of the impeller blade crosssection was extracted and fitted using grey prediction method; the 3D digital models of impeller blade were reconstructed and the 3D model of damaged blade was obtained via Boolean operation. Finally, the 3D point cloud process platform and reconstruction experiment platform were introduced; using laser cladding forming technology and adaptive grinding, an application example of remanufactured impeller was given, which proved that the method is feasible, and the future research direction was also proposed.