Abstract:Agricultural robot is an important branch of robot family, and it reshapes the modern agriculture industry via replacing human with machines. The definition and classification of agricultural robots were presented, followed by the analysis of its current status, application requirements and technical challenges. Therefore, the phases of agricultural robots were divided into three stages. Through investigating a broad spectrum of agricultural robots with in diverse productional scenes, totally five aspects of the key technologies of agricultural robots, i.e., the biological and environment perception, smart decision-making and control, dexterous robotic arm and hand operation, autonomous navigation, and end-terminal-cloud coordinated robotic system integration, were highlighted to foresee its developing trends. Relevant standard architecture was proposed to forge the foundation of agricultural robotics. The agricultural robot common key technologies were beneficial to the intelligent agricultural machinery and smart agriculture industry development, indicating that the agricultural robots were in rapid progress which can be seized to catch up and overtake international counterparts. Finally, the developing direction suggestions and roadmaps were given for guiding the domestic agricultural robot industry in the future.

Abstract:Analyzing the interaction of straw-soil-machinery and clarifying the movement and distribution of straw plays an important role in straw management and optimal design of farming machinery. Design-Expert software and Box-Behnken test were used to conduct an experimental study on the performance of key operation parameters under the interaction of straw-soil-rotary tiller on straw displacement and burying effect. In the tillage experiment, a quadratic regression orthogonal experiment was designed with three factors and three levels, including the influencing factors of the straw length, the tillage depth, and the rotary speed, and the response indexes of straw displacement and burial rate. By establishing the response surface mathematical model, the effects of various factors on the performance of rotary tillage were analyzed. The experimental results showed that the significant order of the influence on the amount of straw burial rate and straw displacement was as follows: the tillage depth, the straw length, and the rotary speed. The interaction between the tillage depth and the straw length had a significant impact on the straw burial rate and straw displacement, while the interactions between other parameters were not significant. When the straw length was 5cm, the tillage depth was 14.99cm and the rotary speed was 320r/min, the straw returning effect was the best. The corresponding indexes of straw burial rate and straw displacement were 95.5% and 27.6cm, respectively. The optimized parameters were used for experimental verification. The straw burial rate and straw displacement were 93.3% and 28.1cm,respectively. The results can provide reference for the adjustment of operation parameters of rotary tillage and provide theoretical support for the study of straw-soil-machine interaction mechanism.

Abstract:Hillside crawler tractor (equipped with attitude adjustment mechanism) has good stability and obstacle-surmounting performance, and it is especially suitable for operation on hilly and mountainous slopes. However, due to the existence of the slope angle, the stress distribution under the tracks on both sides of the tractor is extremely uneven, which reduces the adhesion and passability of the tractor. Aiming at the problem that the internal stress distribution law of sloping soil is not clear when the hillside crawler tractor is driving and operating on the contour line slope, on the basis of in-depth analysis of the basic laws of the maximum grounding specific pressure and stress transfer of the crawler under sloping conditions, the EDEM-RecurDyn coupling method was used to carry out the simulation test, and the method of burying the soil pressure sensor was used to carry out the static test based on the small slope soil trench and the dynamic test on the slope field respectively. The static test explored the vertical stress distribution law of soil at different depths under the influence of moisture content, initial compactness, loading quality and slope angle. The variation law of the vertical, horizontal and lateral stresses of soil under the crawler with operating speed, state of the tractor body (leveled and unleveled) and the load when the tractor drive and rotary tillage on the contour line slope was studied by dynamic tests. And the influence of crawler tension on soil vertical and horizontal stress distribution was analyzed. The results showed that the vertical stress under the crawler presented a stress peak at the axis of each roller. The horizontal stress had a stress peak at the front and rear of each roller axis. Appropriately increasing the operating speed can reduce the peak value of vertical and horizontal stress in the soil. When the tractor speed was increased from 0.5km/h to 1.5km/h, the peak value of vertical stress was reduced by 35%, and the peak value of horizontal stress was reduced by 27%. The leveling of the tractor body can better improve the uniformity of vertical and horizontal stress distribution under the crawler on both sides. The vertical stress peaks on the low and high sides of the slope were respectively decreased by 13% and increased by 18%, and the horizontal stress peaks on the low and high sides of the slope were respectively decreased by 28% and increased by 23%. When the crawler tension was reduced from 1.2×104kPa to 8.0×103kPa, the vertical and horizontal stress peaks were respectively decreased by 31% and 22%, which showed that moderately reducing crawler tension reduced soil compaction. The research result can provide a theoretical basis for the optimization of relevant parameters of hillside crawler tractors, so as to improve the uniformity of soil stress distribution on slopes and alleviate the soil compaction.

Abstract:The work of adding seed and fertilizer is an indispensable operation for seeding machinery unit. The research on quantitative relationship between seed or fertilizer adding parameters for seeding machinery unit and operational plot length is of great theoretical and practical significance to objectively analyze the regulars of seed and fertilizer adding parameters varying with plot length, and to improve the time utilization rate for seeding machinery unit. Based on the actual operation organization needs for the seeding machinery unit, the concept of the travel ratio of seed and fertilizer adding αw was put forward, the mathematic models of the distance between two adjacent seed or fertilizer adding positions, seed or fertilizer adding amount, seed or fertilizer adding times, and seed and fertilizer adding time for seeding machinery unit varying with the parameters of operational plot length were established under the conditions of three adding seed and fertilizer modes and with or without αw. Combined with experimental data and Matlab software, the various regulars of four seed and fertilizer adding parameters varying with operational plot length were determined when four typical seeding machinery units were operated with adding seed and fertilizer at one side of the plot. Regulars of four seed adding parameters of seeding machinery unit with or without αw all had a “two-ranges one-point” feature varying with plot length. When the plot area was 5hm2, the demarcation points between the corresponding plot length ranges with different seed adding parameters and with the same seed adding parameters, and the upper limit points of plot lengths that can be operated by four typical seeding machinery units with adding seed and fertilizer at one side of the plot were determined: the demarcation point of John Deere 7830 seeding machinery unit was 575m and the upper limit point was 1151m, the demarcation point of Valtra 171 seeding machinery unit was 438m and the upper limit point was 1031m, the demarcation point of Changfa 504 seeding machinery unit was 457m and the upper limit point was 1035m, and the demarcation point of the Huanghai 254 seeding machinery unit was 517m and the upper limit point was 1035m. The research results can improve the relevant application theory of agricultural machinery unit, provide theoretical and technical support for effectively improving time utilization rate and operational efficiency, and provide scientific basis for operation planning for seeding machinery unit and high-quality developing of agricultural mechanization.

Abstract:Considering the facts that the uniformity of seeding distribution in the existing mechanical centrifugal centralized metering device for rapeseed which led to the lower apiece row consistency, a spinning disc precision centralized metering device for rapeseed based on Bezier curve was developed. The working principle of the distributor device was elaborated. The parameter equation of the guide vane curve of the spinning disc was constructed by using Bezier curve’s tangential vector property and the characteristic of no curvature mutation. The dynamic and kinematic models of seed particles were established, and the key structural parameters and ranges affecting the seed performance were determined. The EDEM discrete element simulation software was used to carry out the quadratic orthogonal combination test in order to establish a mathematical model between the performance of the apiece row consistency variation coefficient and guide vane’s inlet angle, the outlet angle, the wrap angle and the quantity. The results showed that the sequence of factors affecting the apiece row consistency variation coefficient were vane’s inlet angle, the outlet angle, the quantity and the wrap angle. The optimal parameter combination was established when the guide vane’s inlet angle was 36°, the outlet angle was 26°, the wrap angle was 55° and the number was 8. Based on the optimal parameter combination, the bench verification test results of the metering performance at different rotational speeds showed that the metering device could adapt to different rotational speeds according to the sowing demand, and when the rotational speed was 60~100r/min, the apiece row consistency variation coefficient was less than 3.9%, the single row stability variation coefficient was less than 4.6%, and the damage rate was less than 0.5%. The field experiment showed that when the planting speed of the seeder was 4.15km/h, the apiece row plant distribution consistency variation coefficient of rapeseed was less than 14%. It could meet the seeding performance requirements of rapeseed.

Abstract:In order to save man-hours and improve labor efficiency, a dual-operating machine for transplanting dry land pot seedlings was proposed, and aiming at the problems of low planting qualification rate due to unsatisfactory planting trajectory and high missing seedlings rate due to planting claws clogged in the transplanting process, a dryland pot seedling planting mechanism was designed. The mechanism was composed of crank, rocker, pendulum and finger-type planter, and the functions of receiving, transporting, planting and resetting seedlings were realized, so that the planting trajectory and movement posture reached the optimal state of planting agronomic requirements. The finger-type planter was designed as an open structure, the clamping finger solved the problem of soil clogging by flushing with water and closing momentary vibration. Based on the theoretical analysis of the transplanting mechanism, the kinematics model was established. The computer-aided optimization design software was developed by using Visual Basic 6.0 software, and a group of mechanism parameters that corresponded to the best trajectory of the planting mechanism was obtained. A 3D modeling of the planting mechanism was established, and the kinematics simulation analysis was carried out by using ADAMS software, which verified the rationality of the mechanism design. The prototype field experiment results showed that under the working conditions of pot seedlings with a height of about 15cm and an operating speed of 20m/min, the planting qualification rate was 98.1%, the seedling leakage rate was 0.4%, the coefficient of variation of plant spacing was 4.3%, and the qualified rate of planting depth was 96.5%, meeting the requirements for transplanting dry land pot seedlings.

Abstract:In agricultural fields with full straw retention, due to the large amount of rice straw and the high humidity and toughness of the rice straw, it is difficult for the wheat to be spread uniformly after wheat planting. To achieve uniform crushed straw throwing in dense fields of rice stubble and high-quality straw mulching in dense fields, the uniform throwing device of a no-tillage planter to perform uniform throwing of crushed straw stubble on fields was analyzed and the device operation mechanism was determined. From kinematics and dynamics analyses of particles of crushed rice straw during spread uniformly, a flexible-body model of crushed straw was developd based on EDEM. By adopting the Box-Behnken design, the cover straw inhomogeneity and percent of pass for scatters width as the evaluation index was set and a response surface test was performed on the rotation speed of throwing impeller, the number of pole tooth blade of throwing impeller, angle of throwing impeller. Through a field verification test, the respective parameters for maximum implementation performances were obtained: when the number of pole tooth blade of throwing impeller was 4, the angle of throwing impeller was 15°, and the rotation speed of throwing impeller was 1195r/min, the cover straw inhomogeneity and percent of pass for scatters width by the models were 80.84% and 9.32%. The research result can provide a theoretical basis and data support for innovating seeding technologies and optimizing equipment to uniform crushed straw throwing in dense fields of rice stubble. The uniform throwing device provided high spreading performance for actual operation. Design and optimization of uniform throwing device by no-tillage planter of wheat after rice provided a theoretical basis and data support for innovating seeding technologies and optimizing equipment to evenly throw.

Abstract:In view of the existing problems of the three-arm rice transplanting mechanism, such as the insufficient angle of pushing seedlings, and the partial absolute movement trajectory forward after planting, a reverse design method based on the local motion trajectory was proposed to overcome this problem. Firstly, the relationship between the absolute motion trajectory and relative motion trajectory of the mechanism was analyzed, and combined the existing problems of the original mechanism to preset the return section trajectory of the local standard absolute motion trajectory, the picking-seeding angle to reverse the local relative motion trajectory and key position points of the transplanting mechanism. The non-uniform B-spline curve was used to fit the trajectory. Secondly, a reverse design model for transplanting mechanism was established. A Matlab-based reverse analysis design software for seedling transplanting mechanism was developed to solve the parameters that met the design requirements of the mechanism. At last, the structure of three-arms rotary rice seedling transplanting mechanism was designed, and a physical prototype of the mechanism was manufactured. A virtual kinematic simulation and high-speed photographic kinematics bench test of the seedling transplanting mechanism were carried out to study the motion characteristics of the physical prototype of the mechanism. The results showed that the simulation trajectory, test trajectory and theoretical trajectory were basically the same, and the pushing-seedling angle was increased by more than 9.08°, the return height of the moving trajectory greater than 120mm, the difference between the taking-seedlings and pushing-seedlings’ angle difference and the seedling box’s installation angle was within ±2°, which met the design requirements. The correctness of the design method and design results of the mechanism were verified.

Abstract:To meet the requirements of maize grain harvester for cleaning large feeding mass of maize mixture, the double-layer jitter plates with holes were designed to shunt the maize mixture when they entered the cleaning device. The movement of particles after leaving jitter plates before arriving at vibrating screen was analyzed. The position of the upper and lower jitter plates relative to the vibrating screen, the distribution and size of the sieve holes on the upper jitter plate were determined. The angles of the jitter plates installed, the amplitude and the frequency of the jitter plates were chosen as the experimental factors. The time of cleaning maize mixture by the screeens, the cleaning rate and the loss rate of the maize grains were chosen as the performance indexes. The CFD-DEM coupled method was used. The effect of test factors on performance indexes was determined. The quadratic orthogonal rotational-combinational simulation tests were designed. The regression mathematical models between factors and indexes were founded. When the inlet velocity of airflow was 12.8m/s, the direction angle of airflow was 25°, the feeding mass was 7kg/s, the best combination of parameters were that the angle of the jitter plates installed was -3.85°, that the frequency of the jitter plates was 5.62Hz and the amplitude of jitter plates was 44.77mm. The cleaning and loss rate of maize grain and the time of cleaning maize mixture by the screens were 98.36%, 1.45% and 6.74s, respectively. Compared with the cleaning system with single-layer jitter plate, the cleaning rate of maize grain was reduced by 1.72 percentage points, the loss rate of maize grian was reduced by 0.84 percentage points and the time of cleaning maize mixture was shortened by 0.57s. The performance tests were done in the laboratory to verify the accuracy of the simulation results.

Abstract:Mature rapeseed pods split easily. Under the shearing and vibration forces of the side knife, the pod splits, and the rapeseed scatters out of the header, resulting in high rapeseed losses. Aiming at the problem, side knife cutting scattered seed pneumatic recovery method was proposed, and positive and negative pressure combined side knife cutting scattered seed recovery device was designed. The scattered materials were collected by the positive pressure airflow direction and transported to the entrance of the negative pressure airflow, and then directed by the negative pressure airflow to recover and pneumatically transported back to the header to achieve recovery and loss reduction. The internal flow field simulation analysis model of the recycling tube was built based on Fluent. The results of the single-factor test showed that the negative pressure airflow velocity was decreased with the increase of the throat diameter and increased with the increase of the throat inclination angle, and the diameter and inclination angle of the throat were determined to be 70mm and 120° respectively. Negative pressure airflow velocity was decreased with the increase of decreasing angle and decreasing angle in a certain range and there was an interactive effect, the determining factors were the inlet diameter, shrinkage length, outlet diameter and diffusion length. A quadratic regression orthogonal combination test was conducted using negative pressure airflow velocity as the evaluation index. The results showed that the importance of the factors affecting the negative pressure airflow velocity were length of the diffusion length, inlet diameter, shrinkage length, and outlet diameter. The optimized parameter combination was inlet diameter of 94mm, shrinkage length of 38mm, outlet diameter of 115mm and diffusion length of 350mm. A coupled CFD-DEM simulation model of the internal airflow-material in the recovery device was developed to study the influence of positive and negative pressure airflow velocity on the material recovery effect. The results showed that the material recovery rate was firstly increased and then decreased with the increase of positive pressure airflow velocity, and continued to increase with the increase of negative pressure airflow velocity. The optimal positive pressure airflow velocity was determined to be 20m/s. Based on the analysis of positive and negative airflow, the ratio of the cross-sectional area of the two airflow channels in the airflow distributor was determined to be 1∶3. Field tests showed that the loss rate of rapeseed header and side knife were 1.26% and 0.39% respectively after equipping scattered seed recovery device, and the loss rate was decreased by 21.8% and 47.3% respectively. The header loss and side knife loss were effectively reduced. The study can provide a reference for the design of low loss rapeseed header.

Abstract:Camellia oleifera industry has developed rapidly in China, and the planting scale has increased year by year. Aiming at the problems of low efficiency of manual harvesting, high labor cost, short ripening period of Camellia oleifera fruit and synchronization of flowers and fruits, a crawler-type high clearance Camellia oleifera fruit vibrating harvester which can realize continuous vibration fruit dropping and collection was designed. A straddle frame was used to walk along the planting line of Camellia oleifera, and the crank rocker mechanism was used to drive the finger row rods of multi row array to strike both sides of the tree crown at the same time according to a certain motion track. The fallen fruits were collected through the collection plate and transported to the fruit box. According to the hitting track, the crank rocker mechanism of the hitting device of the harvester was designed, and the motion track of the finger frame was verified by ADAMS software. Through the finite element modal analysis of the hitting device frame and harvester frame with ANSYS software, the first six-order natural frequencies were obtained to determine that there would be no resonance. In order to receive the fallen Camellia oleifera fruit, a collection plate with staggered height distribution was designed, which can not only receive the fallen fruit, but also avoid the trunk smoothly, so as to complete the vibration fruit falling and collection operation of the whole machine in motion. Finally, the prototype of vibration harvester was processed and assembled, and the whole machine test of Camellia oleifera forest land was carried out under the condition of hitting the hydraulic motor speed of 360r/min. The test results showed that the average recovery rate of Camellia oleifera fruit was 87.56%, the average drop rate of flower bud was 25.86%, which fitted the requirements of Camellia oleifera fruit recovery.

Abstract:Directional sowing of maize, i.e. the tip of seeds in the soil should be in the same direction and so does the embryo side, can improve crop yield. In order to realize the embryo side orientation of maize seed, an embryo side orientation device of maize seed based on vibration sorting was developed. The selector and orientor set on the spiral track of the device were innovated, the principle of embryo side orientation was proved, and the dimension parameters and space position of the selector and the orientor were determined. The optimum working parameters of the device were optimized by the test method. The experiment was employed through the method of Box-Behnken orthogonal rotating center combination of three factors and three levels. In test, dent corn seed was selected as experimental material. Combining with extensive pre-experiment and theoretical analysis, the output voltage of the controller, the vertical distance between the end point of the first orientor for turning over and the side wall and the vertical distance from the end point of the first orientor for turning over to the track surface were taken as main influencing factors, and the success rate of the embryo side orientation was taken as response index. The optimal combination of parameters was as follows: the output voltage of the controller was 101V, the vertical distance between the end point of the first orientor for turning over and the side wall was 4.38mm, and the vertical distance between the end point of the first orientor for turning over and the track surface was 7.96mm. Under the optimal combination of parameters, the success rate of the embryo side orientation was 94.85%. The verification test was repeated three times. And in the verification test, the success rate of the embryo side orientation was 94.82% with the discharge rate of 85 per minute. The actual test results were in agreement with the optimization results. In order to verify the adaptability of embryo side orientation device to different varieties of maize, the variety adaptability test was carried out, and the test results showed that the success rates of the embryo side orientation of two varieties were greater than 91%, which indicated that the device can meet the requirements of design. The research laid a foundation for the development of device for mechanized directional sowing of maize, and provided a reference for the subsequent production of seed tape of directional sowing of maize.

Abstract:The discrete element simulation parameters calibration of pellet feed attrition was carried out by using EDEM simulation software, aiming at the lack of accurate attrition simulation model of pellet feed, so as to explore the damage mechanism of pellet feed in pneumatic conveying. The intrinsic parameters of pellet feed with a particle size of 2.50mm, which was used as the object and served for polyculture adult fish, were determined through basic experiments. The coefficient of restitution, coefficient of static friction and coefficient of rolling friction between feeds were determined to be 0.58, 0.23 and 0.12, respectively, while these three coefficients between feeds and soft plastics (soft PVC, polyvinyl chloride) were 0.69, 0.22 and 0.18, respectively through AoR (angle of repose) test of pellet feed, coefficient of restitution calibration test and discharge time of pellet feed, combined with the experimental optimization design method. The normal stiffness per unit area, shear stiffness per unit area, critical normal stress and critical shear stress were determined by uniaxial compression breakage test and simulation test of pellet feed, combined with response surface optimization, which were 2.25×109N/m3,8.05×108N/m3, 455MPa and 305MPa, respectively. The AoR simulation test and uniaxial compression simulation test were conducted with the determined parameters, whose results showed that the relative errors between the simulated value and the measured value in AoR, breakage force and discharge time were 0.35%, 1.43% and 2.81%, respectively;the contact parameters of the bonding model were verified by tests of free discharge, inclined sliding and inclined rolling, whose results showed that the contact parameters of the bonding model were reasonably set. The model developed could provide a method and theoretical basis for the calibration of discrete element simulation parameters and the study of attrition mechanism of pellet feed.

Abstract:Fertilizers play an irreplaceable role in agricultural production. In China, the use of chemical fertilizers is large but the fertilizer utilization efficiency is low. In order to ensure the sustainable development of agricultural production, controlled release fertilizers with high nutrient efficiency and environmental friendliness have received widespread attention. The controlled release fertilizers adopt polymer coating, which can quantitatively control the nutrient release amount and release period of the fertilizer, so that the nutrient supply is consistent with the law of fertilizer demand in each growth period of the crop, and the effect of saving fertilizer and increasing efficiency is significant. The nutrient release characteristics of coated fertilizers are closely related to the material and structure of the coating layer. In the process of discharging fertilizers, the discharging device will cause different degrees of mechanical damage to some fertilizers, resulting in damage to the coating layer and affecting the nutrient release characteristics. Therefore, it is of great significance to design a fertilizer discharging device suitable for non-destructive discharging of coated fertilizers. In order to ensure that the numerical simulation truly reflects the crushing of fertilizer particles, it is necessary to calibrate the parameters of the crushing model of coated fertilizer particles. The critical crushing displacement and critical crushing load of the coated fertilizer particles were obtained through uniaxial compression tests. With this as the goal, the Bonding model parameters were systematically calibrated, based on sequential tests (Placket-Burman test, Steepest ascent test and Box-Behnken test), and finally the optimal parameters combination was optimized. The uniaxial compression test was carried out again under the optimal parameters combination condition. The relative error of the critical crushing displacement and critical crushing load and the actual value were 0.222% and 0.554%, respectively. The observed qualitative and quantitative results of numerical and experimental approaches were in good agreement. Based on these results, comparing the actual and simulated fertilizer particle crushing in the fertilizer discharging process, it was obtained that the fertilizer particle crushing rate in the simulation was slightly higher than that of the actual situation. Overall, DEM modeling better reproduced the damage of fertilizer particles in the fertilizer discharger.

Abstract:Aiming at the problems of waste of pesticide, low utilization rate and environmental pollution caused by spraying the same amount of pesticide in the traditional plant protection spray rod sprayer, a wheat variable spray operation system based on positioning system and machine vision was designed. The region of interest (ROI) was obtained by double-plane height projection method. The effects of velocity and plant density on spray volume were studied, and the control method of variable spray volume was proposed. In the target area planned by the positioning system, variable spray was realized by machine vision processing. The test results showed that at the same unit speed, the average fog drop coverage in the sparse area of plant density was reduced by 12.06% compared with that in the normal area of plant density. At the same plant density, the average fog drop coverage rate at unit advancing speed of 0.75m/s was 3.94% higher than that at speed of 1.50m/s. Under the condition that the spray standard was satisfied, variable spray can be realized at different speeds and different plant densities. In order to verify the grade transformation accuracy of the driving speed at the boundary of the target area, the positioning sensor was used to judge the relative position of the nozzle at the boundary of the target area in real time and control the opening and closing. The test results showed that the accuracy was the highest when the driving speed was 0.50m/s, and the average exceeding error at the boundary of the region was 48.72cm. In order to verify the influence of driving mode on the accuracy of spray level transformation, a test on the influence of driving mode on the accuracy of spray level transformation was carried out at the boundary of the target area by the positioning system. The test results showed that the average value of the minimum outsize error of driving into the target area was 7.20cm.

Abstract:Aiming at the high requirements of seed quality for sugarcane transversal planting, a combined furrow opener for transversal planting of sugarcane was designed based on the formation conditions of effective seeding space. The furrow opener designed included leak-proof plough, rotary tillage unit and furrow plough. The influencing factors of seeding effect and structural parameters were confirmed via analysis of seeding and soil movement law. Rotary tillage speed, working depth, and forward speed were used as factors, and the effective seeding depth, energy consumption of rotary tillage, and furrowing resistance were employed as indexes. The influence rules of working parameters on the furrow opener performance were studied by a three-factor and three-level field orthogonal experimental design. Results showed that working depth significantly influenced the effective seeding depth, energy consumption of rotary tillage, and furrowing resistance. Moreover, rotary tillage speed significantly influenced the energy consumption of rotary tillage, whereas forward speed significantly affected the energy consumption of rotary tillage. Thus, the influence of the working depth and rotary tillage speed was extremely significant, but that of forward speed was generally significant. The better parameters were obtained with the rotary tillage speed of 200r/min, the working depth of 30cm, and the forward speed of 1.20m/s. The field verification experiment results with better parameters showed that the effective seeding depth was 29.9cm, the stability of seeding depth was 97.6%, the thickness of covering soil was 8.8cm, the thickness of regolith was 3.4cm, the energy consumption of rotary tillage was 34.0kW, and the unilateral furrowing resistance was 14.1kN. The indicators could meet the requirements of sugarcane transversal planting.

Abstract:Pressure fluctuation is the main factor affecting the operation stability of pump turbine. In the existing studies, the frequency domain and transmission characteristics of high frequency pressure fluctuation were investigated, while low frequencies less than blade frequency were also the main sources of pressure pulsation. Comparing with numerical simulation, more accurate results can be obtained with experimental method. The main frequency components were not lost easily. Different pressure fluctuation monitor points from volute to draft tube were arranged. The transmission characteristics of high frequency and low frequency components under turbine operation and pump operation were studied by experimental method separately. The results showed that under both of the turbine and pump operation conditions, the pressure pulsation in the vaneless zone was the largest, and the main frequencies were the blade frequency and its multiple frequencies. These frequencies were decreased sharply when these frequencies propagate toward upstream and downstream, so their propagation characteristics were weak. The attenuation of the rotation frequency with small amplitude was less when it transmitted toward upstream and downstream. So transmission property of the rotation frequency was strong. The frequencies less than the blade frequency were increased at other monitoring points. Under the turbine operation, propagation of the low frequencies less than the rotation frequency forming in the volute and the conical tube of draft turbine was strong, but their propagation ability can be weakened by the runner. Under the pump operation, most of the frequencies less than the blade frequency were large in the vaneless region. The amplitudes of these frequencies were decreased when they were transmitted toward the upstream and downstream. The transmission characteristic of the low frequency f/fn =0.006 was strong toward upstream and downstream. The propagation property toward the upstream was enhanced when the operation condition was deviated from the optimal condition. The amplitude for the multiple frequency of rotation frequency f/fn=3 was small, but its attenuation was less when it was transmitted throughout the flow field.

Abstract:Accurately identifying the spatio-temporal information of surface changes will help to explore the law of development and evolution of surface natural environment and ecosystems, and support related scientific research and administrative management. Taking part of the implementation area of an ecological protection and restoration project in Henan Province as the study area, based on the Google Earth Engine (GEE) cloud platform, using 98view Landsat8/OLI remote sensing images from 2013 to 2020 as the data source, and the Breaks for additive season and trend (BFAST) algorithm theory was applied to extract and map information on land surface changes. The methodological experimental process included: firstly, the Landsat8/OLI land surface reflectance dataset was called and pre-processed based on GEE, the cloud shadow masking of the remote sensing dataset based on CFMask algorithm, the calculation of the spectral index (vegetation index NDVI) and the construction of the time series dataset. Secondly, based on the time series data set and the BFAST algorithm theory, a generalized linear regression model consisted of trend terms, seasonal terms and residual terms was constructed, and the unknown parameter set in the model was solved by the least square method, so as to further construct a time series fitting model and detect time-series structure changes in near real-time based on the Moving sums of the residuals (MOSUM) method. Finally, image element sample points were extracted from the detection results, and the results were validated and evaluated in terms of accuracy by overlaying with Google Earth high-resolution image data and visual interpretation. The analysis of the results showed that the method proposed had high detection accuracy in the detection of time-series land surface ecological changes in the study area (83.7% overall accuracy, 86.5%, 80.7% and 87.7% accuracy of the detection results in the sub-years from 2018 to 2020, respectively) in the detection of time-series land surface changes in the study area. Overall, the method proposed was a basic method for remote sensing big database construction, near real-time disturbance identification and monitoring of land surface ecological information and other technologies, which can provide technical support and decision-making support for the investigation and monitoring of ecological protection and restoration in national land space and assessment and early warning.

Abstract:In order to reveal the temporal and spatial differentiation characteristics of carbon emissions from cultivated land use transition, taking Harbin section of Songhua River Basin as an example,the carbon emission intensity of cultivated land use transition from 1990 to 2020 was measured based on the grid element method and carbon emission coefficient. In addition, the means of gravity center analysis, exploratory spatial data analysis, cold and hot spot analysis tools and geodetector were implemented to reveal the spatial heterogeneity and formation mechanism of carbon emissions from cultivated land use transition. The results showed that the cultivated land area demonstrated a downward trend in 1990—2020, and the conversion between cultivated land and construction land, forest land was the most dramatic, and cultivated land mainly converted into construction land.The carbon emission of cultivated land use transformation showed an upward trend in 1990—2020, from 3704.12t in 1990—2000 to 35656.29t in 2010—2020 with an increase of nearly 8.63 times. The carbon emission of cultivated land use transformation eventually appeared as a carbon source. From 1990 to 2020, the carbon emission center of arable land use transformation remained basically stable, moving 15.17km to the east, of which the center of gravity moved the longest from 1990 to 2010. Overall the carbon emissions in the northeast region continue to deteriorate, while the carbon emissions in the southwest region were improved significantly. In 1990—2020, the carbon emissions from cultivated land use transformation were non randomly distributed, but had strong spatial agglomeration. The hot spots mainly spread around Nangang District to the surrounding boundary, and the cold spots were scattered in the southeast. Urban center distance was the main factor of carbon emission for cultivated land use transformation, and the interaction between various factors was mainly enhanced by two factors. Among them, the interaction between land use degree, and annual average precipitation, urban center distance had strong explanatory power. The spatial differentiation characteristics of carbon emission for cultivated land use transformation were the result of multi-factor interaction.

Abstract:Soil salinization seriously restricts sustainable agricultural development, and it is a main environmental problem in arid and semiarid regions. Therefore, the method of assimilating remote sensing data is used to monitor spatial and temporal information of soil salinity in a regional scale, which is of great significance to management of soil salinization. The feasibility of soil salinity estimation to assimilate HYDRUS-1D model and remote sensing data was explored by using ensemble Kalman filter. The study area was located in Shahaoqu Irrigation District of Hetao Irrigation District. The remote sensing data was obtained by GF-1 satellite. Spectral indexes were screened by gray correlation method, and inversion models of soil salinity at different depths were constructed by ridge regression models. Then remote sensing data was applied to HYDRUS-1D model by using ensemble Kalman filter to carry out assimilation study of soil salinity of different depths in a regional scale. The main conclusions were as follows: based on ridge regression models of soil salinity at different depths, R2 were above 0.64 and RE were 0.14~0.22. Inversion accuracies were relatively good and inversion values were relatively accurate. In a single point scale, compared with inversion values and simulation values, assimilation values were closer to measured values. EFF of assimilation values were 0.84~0.93 and their NER were 0.61~0.73. They were all positive values. And their RMSE were reduced to 0.006%~0.011%. These results showed the scheme of data assimilation improved simulation accuracies of HYDRUS-1D model. In a regional scale, r of assimilation values were above 0.94 and their NER were above 0.61. And they were better than r and NER of inversion values and simulation values. Meanwhile, with increase of depth, the accuracy of assimilation was decreased. The results indicated that data assimilation greatly improved simulation accuracies of soil salinity at different depths by using ensemble Kalman filter. The research result can provide certain reference value for improving monitoring accuracy of soil salinity in a regional scale.

Abstract:In view of the problem that most remote sensing prediction methods take spectral information as the main feature of the model and ignore the temporal variation characteristics when obtaining leaf area index (LAI) quickly and accurately, the UAV was equipped with a five channel multispectral camera to obtain the multispectral images of different growth periods of maize in the study area. The vegetation indices of maize in corresponding growth period were calculated based on the images. Then the sub models of each growth period were established by using the vegetation indices. The contribution of the root mean square error (RMSE) of each sub model to the RMSE of the whole growth period model was calculated based on Shapley theory. The weight of each sub model was given based on its contribution. The combination estimation model was built with LAI timeseries variation characteristics according to the weight. And different combination models were built based on support vector regression (SVR) algorithm, multilayer perceptron (MLP), random forest (RF) algorithm and XGBoost algorithm for comparison. The results showed that the estimation effect of the combined LAI estimation model based on Shapley theory was better than that of the whole growth period LAI estimation model. Compared with other LAI estimation models (SVR-Shapley, MLP-Shapley and RF-Shapley), the XGBoost-Shapley model had the best estimation effect (R2 was 0.97, RMSE was 0.021, RPD was 6.9). Thus the XGBoost-Shapley model was applied to LAI prediction in the study area. The research results showed that the LAI change rate in different growth periods were different, and the prediction results accorded with the growth trend of maize in different growth periods. The research result can provide a method for remote sensing monitoring of field maize growth.

Abstract:The extraction of rivers in cold and arid regions is of great significance to the rational utilization of water resources, water conservancy planning and early warning of water disasters. In order to solve the problem of refined river extraction from remote sensing images, a segmentation network (AFR-LinkNet network) was proposed based on the LinkNet model. AFR-LinkNet introduced residual channel attention structure, asymmetric convolution module and dense skip connection structure on the basis of LinkNet, and replaced the original ReLU activation function with visual activation function FReLU. The residual channel attention structure can strengthen the features that were effective for segmentation tasks to improve the classification ability of the model and obtain more detailed information. The asymmetric convolution module was used to compress and accelerate the model. The FReLU activation function boosting network was used to extract fine spatial layout of rivers in remote sensing images. The experimental results on the river dataset in cold and arid regions showed that compared with FCN, UNet, ResNet50, LinkNet, DeepLabv3+ network, the intersection ratio of AFR-LinkNet network was improved by 26.4 percentage points, 22.7 percentage points, 17.6 percentage points, 12.0 percentage points and 9.7 percentage points respectively, the pixel accuracy was increased by 25.9 percentage points, 22.5 percentage points, 13.2 percentage points, 10.5 percentage points and 7.3 percentage points, respectively. After the introduction of the asymmetric convolution module, the intersection ratio was increased by 5.1 percentage points, and the pixel accuracy rate was increased by 2.9 percentage points. On this basis, after introducing the residual channel attention structure, the intersection ratio was improved by 2.2 percentage points, the pixel accuracy rate was improved by 2.3 percentage points, and its performance was better, and the extracted river coherence and details were better preserved. Therefore, AFR-LinkNet algorithm was of great and far-reaching significance for analyzing river distribution, water disaster warning, rational utilization of water resources and agricultural irrigation development in cold and arid regions of China, laying a foundation for the realization of sustainable development in China.

Abstract:Aim to identify and position corn seed, an object detection model based on improved YOLO v4 was proposed. This model combined with multi-spectral images with four channels (RGB+NIR), the appearance quality of corn seeds was identified and classified. In order to reduce the number of parameters in the model, the trunk feature extraction network was replaced with the lightweight network MobileNet V1. To improve the performance of the model, the effect of spatial pyramid pooling (SPP) structure on the model performance was studied. Finally, the improved YOLO v4-MobileNet V1 model was selected to detect the appearance quality of corn seeds. The experimental results showed that the comprehensive evaluation indexes F1 and mAP of the model reached 93.09% and 98.02%, respectively. The average detection time of each image was 1.85s, and the average detection time of each corn seed was 0.088s. And the number of model parameters was compressed to 20% of the original model. The spectral band of four channel multi-spectral image can be extended beyond the visible range. Image can extract more representative feature information. The improved model had the advantages of strong robustness, good real-time performance and lightweight. It can provide a reference for high throughput quality detection and optimal classification of seeds.

Abstract:In view of the characteristics of small size, dense distribution and changeable color of Camellia oleifera fruit, in order to realize the rapid and accurate identification of Camellia oleifera fruit in complex natural scene, and determine the appropriate clamping position for the automatic oscillating harvesting device according to the density distribution of the fruit, the YOLO v5s convolutional neural network model was used to carry out research on the image detection method of Camellia oleifera fruit in the natural scene. Through data enhancement, totally 3296 Camellia oleifera fruit images were obtained to make the PASCAL VOC data set. After 150 rounds of training, the optimal weight model was got. The accurate rate was 90.73%, the recall rate was 98.38%, the comprehensive evaluation index was 94.4%, the average detection accuracy was 98.71%, the single image detection time was 12.7ms, and the memory size of the model was 14.08MB. Compared with the current mainstream first-stage detection algorithms YOLO v4-tiny and RetinaNet, its accuracy rate was increased by 1.99 percentage points and 4.50 percentage points, the recall rate was increased by 9.41 percentage points and 10.77 percentage points, and the time was reduced by 96.39% and 96.25%, respectively. In addition, the weight file of the YOLO v5s model was small, indicating that its network was simpler and had the advantage of rapid deployment. It could be transplanted to edge devices in the future to provide algorithm reference for the vision system of the Camellia oleifera fruit automatic harvesting device. Through comparative experiment, the results also showed that the model can achieve high-precision recognition and positioning of fruits in dense, occluded, dim environments and fuzzy blur conditions, and it had strong robustness. The research results can provide a reference for the research of mechanical harvesting of Camellia oleifera fruit under the natural complex environment.

Abstract:The underwater images of aquaculture ponds, rivers and sea inlets were generally fuzzy and low contrast due to the influence of water turbidity and light attenuation in water. However, the existing literature found that the clarity brought by image enhancement cannot directly improve the detection ability of fish detection model, and even the detection accuracy of the model was degraded. An multiple and outputs blend enhanced method was proposed for fish detection. Blurred underwater images were enhanced by various image enhancement methods, and the enhanced images were input into the fish detection model to obtain multiple outputs. Then the mixed results were postprocessed by non-maximal inhibition method to obtain final test results. Compared with the detection results of the original image, the experimental results on YOLO v3, YOLO v4 tiny and YOLO v4 models showed that the detection accuracy of the proposed method was improved by 2.15 percentage points, 8.35 percentage points and 1.37 percentage points, and the number of fish was increased by 15.5%, 49.8% and 12.7%, respectively. The proposed method achieved the purpose of improving the model detection ability, and it can be applied to fish count and fish category detection.

Abstract:Accurate prediction of rice pest plays a very important role in ensuring high yield of rice and reducing economic losses. Manual rice pest survey methods in paddy fields are time-consuming. With the developments in computer vision technology and theory, machine learning and deep learning have been applied in automatic identification of agricultural pests, which have greatly improved image classification accuracy of rice pest. Target detection algorithm YOLO v5 was introduced to identify and count Cnaphalocrocis medinalis and Chilo suppressalis on monitoring equipment and traps. Based on the biological habits of C.medinalis and C.suppressalis, a multi-source rice pest images dataset was constructed from the images of adults of C.medinalis and C.suppressalis , which were captured by a self-developed rice pest trap and photo device, triangular traps and light traps. The number of images in the dataset were increased by flipping the image left to right, increasing the image contrast, and flipping the image up and down. The detection performance of different training models on rice pest images captured by triangle traps and monitoring device was compared, and the effects of different training sample sizes on the identification results were compared. Precision, recall, F1 score and average precision were used to evaluate the difference of each model. The models were tested on the rice pest images captured by triangle traps and monitoring device. The results showed that the precision and recall of C.medinalis were 91.67% and 98.30%, respectively, and the F1 score was 94.87%. The precision and recall of C.suppressalis were 93.39% and 98.48%, respectively, and the F1 score was 95.87%. Multi-source rice pest images dataset constructed by different sampling background and equipment can improve the accuracy of rice pest by identification model. The rice pest identification and counting model developed based on YOLO v5 algorithm can achieve high identification accuracy and it can be used to monitor population of C.medinalis and C.suppressalis in the field.

Abstract:Tomato leaf-type diseases have the characteristics of large intra-class differences and small inter-class differences in the early and late stages. The conventional neural network is not effective in classifying such diseases. Therefore, based on the fine-grained weakly supervised classification method, a Res2Net bilinear attention network, combining the bilinear model and attention mechanism, was proposed. The fine-grained representation ability was improved through extracting multi-scale features and combining the attention mechanism. First of all, for the problem of information loss in the process of conventional channel attention acquisition, the EFCA channel attention module was proposed. On the basis of no dimensionality reduction, two-dimensional discrete cosine transform was used instead of global average pooling to avoid some features from being lost in downsampling. Secondly, by adding the maximum pooling after the outer product, and the concat module designed by drawing on the shortcut idea in the residual network, the problem of redundant features caused by the excessively high dimensionality after bilinear fusion was solved. The obtained classification accuracies of the proposed model on the data set with 7 types and 14 different degrees of tomato leaf type diseases were 98.66% and 86.89%, respectively.

Abstract:In view of the problems that the existing closed breeding pig performance measurement station is less researched at home and abroad, the degree of automation is not high, and the body size information of breeding pigs cannot be provided. The enclosed breeding pig performance measurement system was designed, which integrated automatic breeding pig identification, automatic weight weighing, automatic feed intake statistics and automatic body size measurement. The front and back end separation design was adopted in the mechanical part of the system. Feeding device and access controlling device were designed to provide a closed measurement environment for breeding pigs. On this basis, the dynamic weighing algorithm of breeding pigs was designed based on FIR filter, the ideal pose selection algorithm of breeding pigs was designed based on ellipse fitting, and the size measurement algorithm of breeding pigs based on envelope analysis was further proposed. The growth performance and body size of simulated breeding pigs were measured respectively. The experiment verification results were as follows: the daily feeding times of pigs were 8.94, the daily feeding time was 92.93min, the feed to meat ratio of pigs was 2.66, the inflection age of growth curve was 126.18d, and the inflection weight was 72.70kg, which were in line with the growth law of pigs in the growth performance experiment. Ideal pose frames were selected for body size measurement experiment pigs. The average relative detection errors of body length, body width, hip width, body height and hip height were 3.69%, 2.53%, 2.60%, 2.59% and 2.17%, respectively, meeting the requirements of body size measurement. The results showed that the closed breeding station designed could be used to measure the production performance of breeding pigs, and the information of weight, feeding and body size of breeding pigs at the same time could be provided to improve the breeding efficiency and promote the development of domestic production of breeding pigs.

Abstract:Visual simulation of root system growth, an important approach to analyze the root system growth mechanism affected by the surrounding environment, is a significant task in the fields of computer graphics and botanical research, especially in agriculture and forestry. A modeling approach was presented to simulate the interaction between root system growth and the environment. This approach was dominated by the interaction of the root tips with the environment, and regulated by an internal resource allocation mechanism. Firstly, the nutrients absorbed by each root tip were calculated, and then the elongation rate and lateral root density of the root tip were regulated through internal resource allocation mechanism and the scaling function of environmental influence, while adjusting the growth direction of the root tip in real time by considering the blocking factors of the tropisms and obstacles. In addition, the approach provided several ways to control the shape of a root stem and its overall morphology of the root system, including editing the template curve, setting resource allocation weights and directional weights, etc. In the experiments, the root systems of different species were firstly simulated, followed by simulations of root systems in different soil environments, including various nutrient distributions and the influence of obstacles and pot walls. The results showed that the proposed approach had the ability to generalize the realistic models for multiple types of root systems for plants, while effectively representing a reasonable interaction response with the environment in a real-time way.

Abstract:To address problems of low mechanization level and labor-intensive sorting tasks before packaging of hydroponic lettuce, an automatic sorting system for abnormal hydroponic lettuce was designed in combination with the deep learning method. The automatic sorting system was composed of an information perception sub-system, an information processing sub-system, and a sorting action execution sub-system. Hydroponic lettuce classification was based on the difference between abnormal and normal leaves. Three cameras from bottom to top were used to capture images. Real-time processing of hydroponic lettuce images was realized based on semantic segmentation DeepLabV3+. The image segmentation model had mIoU of 83.26%, PA of 99.24% and image processing velocity of (193.4±4)ms/frame. To realize sorting of abnormal hydroponic lettuce, a bracket-type hydroponic lettuce sorting sub-system was designed based on phenotype and harvesting mode of the hydroponic lettuce. Quadratic orthogonal rotational-combinational experiments were designed. Experiments on factoring in horizontal and longitudinal support rod angles and stepping motor speed were conducted to obtain the highest sorting success rate. Regression mathematical models between factors and index were multi-objectively optimized by using Design-Expert software. Optimal combination of parameters was obtained, including the horizontal support rod angle of 146°, the longitudinal support angle of 150°, and the stepping motor speed of 11r/min. Perform test was carried out according to the optimal combination of parameters. The sorting success rate of the sorting action execution sub-system was 98%, and the sorting success rate of the abnormal hydroponic lettuce automatic sorting system was 95%, which met technical standard requirements of lettuce refrigerated transportation.

Abstract:The LiDAR frame data can be processed by LiDAR SLAM algorithms to obtain target point cloud of forest plots. As a SLAM algorithm, LOAM can locate and map by extracting line and surface features, which has the advantages of fast computing speed and better robustness than ICP algorithm. However, it is difficult to use this algorithm directly in forest inventory due to poor lines and surface features in forests. A forest LiDAR SLAM system was developed to address the problem as follows: the modules of secondary de-distortion and secondary registration were introduced into the workflow of the new SLAM system to improve the robustness and accuracy of location and mapping;and the priori information, such as LiDAR device measurement accuracy and positional estimation accuracy, was introduced into the optimization algorithm of the de-distortion and registration to improve SLAM accuracy. Four 32m×32m forest sample plots were scanned by 32line LiDAR, and the raw data for the plot point clouds were processed by using the forest SLAM system. An indirect evaluation of the mapping accuracy of the system in forests was completed by comparing the tree position and DBH extracted from the point clouds with the reference data. The results showed that the mean error of the tree position estimates in the x-axis and y-axis directions were -0.004m and -0.011m, respectively. The root mean square error (RMSE) in the x-axis and y-axis directions were 0.081m and 0.083m, respectively. The deviation of the DBH estimates was 0.25cm (relative deviation of 1.18%) and the RMSE was 1.03cm (relative RMSE of 5.53%). And the estimates had higher accuracy compared with the LOAM system estimates. The results showed that the forest LiDAR SLAM system can be used for processing of the plot data scanned by multi-line LiDAR. It was a potential solution for accurate forest inventory.

Abstract:In polarimetric interferometric synthetic aperture ray (PolInSAR) forest structure parameter estimation, the data are affected by the baseline length size, signal-to-noise ratio, environmental topography, and radar wavelength, especially under complex forest environmental conditions, which can lead to errors in the observed complex coherence and thus affect the final inversion results. Firstly the effect of volume coherence selection on the RVoG three-stage forest canopy height inversion was explored, and the coherence farthest from the ground phase was selected as the volume coherence with the ground phase as the reference pixel by pixel. Secondly, the ground phase estimation method was improved by using two coherence linear fitting methods, Deming regression (DMR) and orthogonal regression (OGR), to improve the estimation of the ground phase, and different error ratios (0.3 and 0.6) were set in the DMR fitting method to compare the effects of the ground phase estimation method on the RVoG three-stage forest canopy height inversion. The results showed that the inversion accuracy of the inversion of volume coherence with ground phase as the reference pixel-by-pixel selection was improved compared with that of the complex coherence with the HV polarization channel directly. The coefficient of determination（R2）was increased from 0.349 to 0.383, and the mean square error（MSE） was decreased from 7.097m2 to 5.755m2. Based on the optimal selection of the volume coherence, the ground phase estimation method was improved by using Deming regression and orthogonal regression. It was shown that the least squares regression (LSR)-based ground phase estimation had the lowest accuracy of RVoG three-stage inversion, using DMR and OGR for coherence line fitting had a certain improvement in inversion accuracy compared with LSR, and the coefficient of determination (R2) of all inversion results was around 0.440, and all MSE was reduced by about 2m2. The conclusions indicated that the forest canopy height inversion using the RVoG three-phase method introduced some errors in the height inversion by using the traditional LSR estimation of the ground phase in the presence of errors in the complex coherence. Using other coherence linear fitting methods to overcome the influence of the complex coherence error can improve the final forest canopy height inversion results, and it was also more reasonable to choose volume coherence inversion method with the ground phase as the reference.

Abstract:Studying the trend of crop water demand and identifying key influencing factors can provide a basis for scientific crop irrigation, improvement of agricultural water use efficiency, and optimal allocation of water resources. Based on the daily meteorological data of Jiansanjiang Reclamation Area from 1995 to 2018, according to the Penman-Monteith formula combined with the single-crop coefficient method, the water requirement of the main crops of rice, corn, and soybeans during the growth period were calculated. Using the trend-free pre-whitening Mann-Kendall (TFPW-MK) method to study the change characteristics of the water demand of three crops, adopt the rescaled range (R/S) analysis method to predict the change trend of the future water demand of the crops, and the path analysis method was used to quantitatively analyze the influence of six meteorological factors such as average temperature, net radiation, sunshine hours, wind speed, precipitation, and relative humidity on crop water demand. The key influencing factors of water demand changes were determined, and the relationship between the change trend of key influencing factors and the change trend of water demand was analyzed. The results showed that the average multi-year water requirement of the reference crops in Jiansanjiang Reclamation Area was 606.68mm. The inter-annual changes in the water requirement of major crops such as rice, corn and soybeans during the growth period were relatively stable. There was a significant difference between the amount of water. The average multi-year water requirement of the three crops were 484.84mm, 425.91mm and 319.11mm, respectively. In the time series from 1995 to 2018, the water demand of rice and soybeans during the whole growth period showed an upward trend, while the water demand of maize during the whole growth period showed a downward trend. In the future, water demand during the whole growth period of rice and soybeans would increase, and water demand during the whole growth period of corn would decrease. Average temperature, radiation and sunshine hours were the key influencing factors for the water demand of rice, corn and soybeans, and they played a role in increasing the water demand. Precipitation increased the water demand of crops, but it was not obvious. Wind speed and relative humidity played a certain restrictive effect on the water demand of the three crops. Therefore, the water demand of rice, corn and soybeans in Jiansanjiang Reclamation Area was affected by many influencing factors. The change trend of water demand caused by the changes of meteorological factors during the whole growth period of rice and soybean was consistent with the change trend of water demand of rice and soybean in the TFPW-MK test analysis. The increase in the average temperature during the whole growth period of corn was not enough to offset the influence of radiation and the reduction of sunshine hours on the water requirement of corn, so the water requirement of corn showed a downward trend, which was consistent with the change trend of water requirement of corn in the TFPW-MK test analysis.

Abstract:In order to explore the effects of nitrogen fertilizer solution on soil infiltration characteristics and water and nitrogen migration patterns before and after magnetization, a 300mT constant magnetic field intensity was used to magnetize different potassium nitrate solution concentrations (0g/L, 0.4g/L, 0.7g/L and 1.1g/L), un-magnetized treatments were used as control, and electrical conductivity, pH value, dissolved oxygen amount, cumulative infiltration amount, and wetting front migration distance of solution under different treatments and water and nitrogen migration distribution in different soil profiles after infiltration were determined. The results showed that the amount of dissolved oxygen was significantly increased and electrical conductivity and surface tension were significantly reduced by magnetized fertilizer solution, and the change degree became more significant with the increase of fertilizer solution concentration. The cumulative infiltration amount and the wetting front migration distance within the same time were increased by magnetized fertilizer solution. Soil sorptivity rate S, soil saturated hydraulic conductivity Ks, and effective soil water diffusivity D- in the Philip, Green-Ampt, and one-dimensional algebramic infiltration models were increased, while the suction Sf at the wetting peak and the soil moisture characteristic curve and comprehensive shape coefficient of unsaturated water conductivity m were reduced. The effect of increased infiltration was increased with the increase of nitrogen fertilizer solution concentration. The magnetized nitrogen fertilizer solution improved soil water holding capacity and it was increased with the increase of solution concentration. The one-dimensional algebraic infiltration formula could well describe the distribution of soil water content at the end of soil infiltration of each fertilizer solution concentration under different magnetic field intensities. Both the nitrogen fertilizer solution concentration and magnetization had significant positive correlations with soil nitrate content, and magnetized fertilizer solution with high concentration had the highest values under the combined effect which benefited the conservation of soil inorganic nitrogen.

Abstract:In order to explore the comprehensive benefits of different biochar application modes (different biochar application amounts and application years) on sloping farmland in the black soil region, a 3° slope farmland runoff plot in the black soil region of Northeast China was taken as the research object, and experimental research was conducted from 2015 to 2018, the conventional treatment without biochar (C0) was set, and the applied amount of biochar were 25t/hm2(C25), 50t/hm2(C50), 75t/hm2(C75), 100t/hm2(C100) to analyze the comprehensive benefits of different amounts of biochar application and the duration of biochar application, the results showed that in terms of ecological benefits, biochar can effectively improve soil structure, enhance soil fertility, and improve soil water storage and soil conservation capacity. For two years of continuous application, the effect of soil water retention and soil conservation was the best when the amount of biochar applied was 50t/hm2;for three years of continuous application, the soil structure was optimal when the amount of carbon applied was 50t/hm2;for four years of continuous application soil fertility was the best when the amount of carbon was 100t/hm2. In terms of economic benefits, biochar can effectively improve crop water-saving, yield-generating performance and its economic output value. Applied for one year, when the amount of biochar was 75t/hm2, the water use efficiency reached the maximum. For two consecutive years, when the amount of biochar was 25t/hm2, the marginal productivity of biochar was the largest. For each additional ton of biochar applied, the output was increased by 11.20kg. For three consecutive years of application, when the amount of biochar applied was 50t/hm2, the soybean yield was the best;for four years of continuous application, when the amount of biochar applied was 50t/hm2, the return reached the maximum value. The improved fuzzy comprehensive evaluation model was used to calculate the ecological benefit, economic benefit and comprehensive benefit of different biochar application models. The results showed that the ecological benefit index reached the maximum value when the biochar application amount was 72.74t/hm2 for two consecutive years of application, the economic benefit index reached the maximum value when the biochar application amount was 36.32t/hm2 for three consecutive years of application. The best biochar application mode in the black soil area was continuous application for three years, and the biochar application amount was 62.30t/hm2.

Abstract:With the aim to reduce the resistance during root-cutting operation, the physical properties and root distribution characteristics of grasslands with different degradation degrees were analyzed by measuring the soil firmness, bulk density, water content, porosity, root content, and root diameter. The constitutive relationship of the grassland soil-root composite was studied through triaxial tests of the undisturbed soil of the grassland and the remolded soil. The constitutive relationship of grassland soil with different degradation degrees was verified by numerical simulation. It was found that the physical characteristics and root distribution characteristics of grasslands with different degradation degrees were quite different, and the physical condition of degraded grassland with coverage of 30%~50% was the best. The cohesion, shear strength, elastic modulus, and secant modulus of undisturbed grassland soil samples were decreased with the aggravation of grassland degradation, and the shear strength of root-cutters on grassland should be greater than 24303kPa. The relative error of the deviator stress limit value obtained by the simulated triaxial test and the actual triaxial test was less than 8%, and the triaxial test of grassland soil simulated by ABAQUS was reliable. The constitutive parameters can be directly applied to the numerical modeling of grassland soil. The research can provide a theoretical basis for grassland root-cutting operation and the optimal design of root cutter.

Abstract:By analyzing the response of the fungal community structure in the facility continuous cropping soil to bio-charcoal, a theoretical foundation was laid for alleviating the obstacles of facility continuous cropping and the application of bio-charcoal in facility continuous cropping cultivation. The grafted cucumber “Der 3” was chosen for the test material based on the greenhouse pot experiment, and the vegetable soil of continuous cropping 20a, 15a, 10a, 5a, 1a and 0a (control) was taken respectively. After adding a certain amount of biochar （20t/hm2）, the effects of biochar on fungal community structure and diversity in continuous cropping soils were studied. The results were as follows: the proportion of Basidiomycota and Zygomycota in the soil increased adding a certain amount of biochar to the continuous cropping soil of different years, the chytridiomycota (Chytridiomycota) and other unknown fungal phyla decreased at a certain extent, and it was most obvious in the treatment of 15 a continuous cropping vegetables (L15J). The performance was most obvious in the soil (L1J);at the same time, the diversity of fungi in soil of continuous cropping for 20 a (L20J) was improved. The similarity of the number of fungi in each treatment was relatively small, and the specificity of fungi in each treatment was relatively high. With the increase of planting years, the specificity of fungal flora in the soil was increased, and a large number of new species of fungi appeared at 200~400 OTUs, and the emergence rate of new species showed a downward trend at 1000 OTUs, the fungal species in the soil of continuous cropping 20a (L20J) were the most. Those results showed that applying a certain amount of biochar to the soil for different continuous cropping years increased the proportion of beneficial fungal flora in the soil, and improved the fungal richness and diversity in the soil, which may contribute for soil improvement.

Abstract:Photosynthesis directly affects the quality and yield of blueberries, and the photosynthetic rate of crops is mainly affected by temperature, light and CO2. At present, the control of light and CO2 is mainly based on the saturation point of photosynthesis rate, and the control and control efficiency is low. Aiming at the current problems of greenhouse light and CO2 control efficiency, a comprehensive control strategy of blueberry greenhouse light and CO2 based on the maximization of Gaussian curvature was proposed. Firstly, by collecting the blueberry net photosynthetic rate under different temperatures, light, and CO2 nesting, a blueberry net photosynthetic rate mechanism model was established, including light intensity and CO2 concentration at different temperatures;then according to the Gaussian curvature function of the blueberry photosynthetic rate mechanism model at different temperatures, the fitness function was constructed, and the particle swarm algorithm was used to optimize the maximum value, the light intensity and CO2 concentration corresponding to the maximum Gaussian curvature were calculated, and the maximum point of light and CO2 Gaussian curvature at different temperatures were obtained;finally, based on polynomial fitting, different comprehensive control strategy of light and CO2 was established at different temperatures. By comparing with the control of the saturation point of the maximum net photosynthetic rate, it was found that the average light intensity was decreased by 60.73%, the CO2 concentration was decreased by 25.00%, and the average net photosynthetic rate was only decreased by 14.29%. Compared with the actual blueberry net photosynthetic rate, it was found that using the proposed comprehensive control strategy of light and CO2, the blueberry net photosynthetic rate was increased by more than 1.87 times on average compared with the actual value. It showed that the proposed comprehensive regulation strategy of illumination and CO2 had the characteristics of high comprehensive benefit, and it can provide theoretical support for the regulation of illumination and CO2 in greenhouse.

Abstract:Combining the development and utilization of bioenergy with carbon capture, utilization and storage (BECCUS) is one of the important methods to reduce CO2 emissions in the energy field as it can achieve the negative carbon emissions. Biomass ash (BA) generated from the direct combustion of biomass, can be used to absorb and sequestrate CO2 permanently. However, the issue adopting biomass ash to achieve the negative carbon emissions should be investigated carefully. CO2 mineralization performance of biomass ash from atmospheric CO2 and CO2-rich gas streams with a moderate (101.3kPa) and high CO2 partial pressure (300~1400kPa) was experimented in terms of CO2 sequestration capacity. Moreover, negative carbon emissions of these three mineralization pathways were evaluated as well. Results showed that among all the three pathways, the lowest CO2 sequestration capacity with 60.66g/kg after 40 days was acquired when CO2 came from atmosphere. Comparatively, when the initial CO2 partial pressure was elevated to about 101.3kPa (i.e., the moderate CO2 partial pressure case), the maximum CO2 sequestration capacity of 121.68g/kg can be achieved. When CO2 partial pressure was increased to about 1400kPa (i.e., the high CO2 partial pressure case), a CO2 sequestration capacity of 216.85g/kg was obtained. The actual negative carbon emissions of three mineralization pathways of biomass ash were assessed by comparing CO2 emissions reduction ascribed to CO2 sequestration of biomass ash and CO2 emissions related to energy consumption in the mineralization process and biomass ash transportation. When the transportation distance of biomass ash was less than 207km, adopting this mineralization pathway in which CO2 came from the CO2-rich gas streams with a moderate CO2 partial pressure (101.3kPa) might be reasonable for achieving a highest negative carbon emission. When the transportation distance was above 207km, the pathway in which CO2 came from the gases with a high CO2 partial pressure should be sensible.

Abstract:Food packaging performs three basic functions: containment, preservation of quality, and protection from environmental, physical, and microbiological factors. In recent times, the role of packaging has increased beyond its basic function with changing consumer preferences and expectations. Now, it is also contributing towards extending the shelf life and acts as a quality indicator of the packed food products. The focus is also on the development of active and intelligent packaging. An active and intelligent film with antioxidant activity and freshness indicator was prepared by using low-acyl gellan gum and red cabbage anthocyanins. The rheological behaviors of gellan gum-red cabbage anthocyanin film forming solution were studied. Moreover, the effect of anthocyanin concentration on the physicochemical properties, antioxidant activity, pH color response properties and microstructure of film was measured. In addition, the application performance of film in freshness indication of large yellow croaker and lard preservation were carried out. The results of dynamic measurement showed that the film-forming solution underwent a liquid-solid transition during the cooling process. The dynamic modulus and gelation temperature of film forming solution was increased with the increase of anthocyanin concentration. With the increase of anthocyanin concentration, the moisture content and tensile strength were gradually decreased, while the thickness, water vapor permeability and elongation at break were increased gradually. The addition of anthocyanins endowed the film with good anti-oxidation and pH response properties, and it can improve the thermal stability of the film. The changes of lard quality and freshness indexes of large yellow croaker (volatile base total nitrogen content, total number of colonies and thiobarbituric acid value) and the color difference ΔE of the active intelligent film during storage were investigated. Correlation analysis showed that the color difference of the film had a significant correlation with each freshness index of large yellow croaker. The active and intelligent film can effectively delay the oxidative rancidity of lard, and it had excellent preservation performance for lard.

Abstract:Shelf life is an important indicator for evaluating the freshness of mutton, which is directly related to its quality. To explore the application prospects of bioimpedance technology for shelf-life detection of food, a nondestructive and efficient shelflife detection method was proposed for ready-to-prepare mutton. Combining the key factors affecting the change of freshness of ready-to-prepare mutton and the measurement principle of bioimpedance, the electrodes were designed independently for measuring bioimpedance according to the different testing conditions such as the number of electrodes, electrode materials, and electrode arrangement. The changes of impedance and TVB-N content of read-to-prepare mutton at three storage temperatures of 0℃, 4℃ and 8℃ and the correlation of impedance with TVB-N content and shelf life were revealed;a shelf-life prediction model and evaluation method of ready-to-prepare mutton based on BP neural network was established with TVB-N content as the key indicator, and it was compared with SVM (support vector machine) model and decision tree model. The F1-score of the BP neural network model was up to 95.9%. Based on the BP neural network model established above, a shelf-life detection system of ready-to-prepare mutton was developed by using Java language, which realized user-friendly data visualization and real-time detection of the shelf life of ready-to-prepare mutton. The research result can provide theoretical basis and software tool for the rapid and nondestructive detection of the shelf life of ready-to-prepare mutton, which can ensure the quality and safety of ready-to-prepare mutton and promote the sustainable and healthy development of the food industry.

Abstract:The automated segmentation of sheep carcass is of great significance for improving the productivity of sheep slaughtering and processing enterprises and can contribute to a more intelligent sheep slaughtering and processing industry in China. In order to achieve accurate and efficient segmentation of the sheep carcass point cloud data into multiple splits, and provide a reference for the sheep carcass segmentation robot, a sheep carcass point cloud segmentation method was used based on surface convexity, and the Bame mutton sheep was taken as the research object. The sample point cloud data was collected on the sheep carcass segmentation production line of Meiyangyang Food Co., Ltd. in Inner Mongolia, Bayannaoer. Using the point cloud collection method, a handheld scanner was used to surround the sheep carcass. Multiple laser photosensitive films were randomly attached to the surface of the sheep carcass for three-dimensional positioning and scanning in data collection. The distance between the scanner and the sheep carcass was controlled within 200mm. The point cloud processing steps were as follows: the voxel filtering method was used to downsample the sheep carcass point cloud;the point cloud data was supervoxelized to obtain the supervoxel adjacency graph;the common edge of the adjacent point cloud in the supervoxel adjacency graph was judged by concave and convex, and the concave and convex edges were given different weights;a score function was introduced, and the relationship between the score of each point cloud and the minimum cut score according to different weights were calculated and compared;according to the comparison results, the Ransac algorithm was used to determine the segmentation plane, divide the segmentation area, and complete the segmentation of the sheep carcass point cloud. The test results showed that the average precision, average recall ratio, average F1 value and average overall accuracy of sheep carcass point cloud segmentation were 92.3%, 91.3%, 91.8% and 92.1%, respectively, and the average accuracy of each split were 92.7%, 90.7%, 92.6%, 93.2%, 92.5% and 92.2%, the average recall ratio were 86.0%, 93.2%, 92.8%, 91.6%, 90.9% and 93.4%, respectively. The average time to process a single sheep carcass point cloud was 18.82s. The applicability of this method was judged by segmenting combinations of different sheep carcass split point clouds and sheep carcass point clouds of different body weights, and the comprehensive segmentation ability of this method was verified by comparing two point cloud segmentation algorithms, namely the commonly used region grow and the Euclidean clustering. The results showed that the method can maintain high segmentation accuracy and processing speed in processing three different body types of sheep carcass point cloud samples. The segmentation effect and index results, however, showed obvious advantages: the sheep carcass point cloud can be accurately segmented into hexads, and the segmentation boundary between the splits was flat and clear. It can be used as the basis for the follow-up robots segmentation;the four indexes to evaluate the segmentation accuracy were higher than that of the region grow by 27.1%, 11.5%, 19.2% and 8.9%, and higher than that of the Euclidean clustering by 10.8%, 21.7%, 16.3% and 16.6%, respectively. Research results showed that the method had high segmentation accuracy, good real-time performance and certain applicability, and the comprehensive segmentation showed good ability.

Abstract:Soybean lipophilic protein and methyl cellulose complex were used as hydrophilic emulsifiers to form the outer phase of W/O/W emulsion. Using PGPR as lipophilic emulsifier, olive oil as oil phase and vitamin B12 as indicator, W/O/W emulsion was prepared by a two-step method. The effects of the ratio of LP to MC in the complex and outer phase on the stability of W/O/W emulsion were investigated by means of laser scanning confocal microscope, optical microscope, particle size, Zeta-potential, rheological properties and stability index. The experimental results showed that when LP∶MC was 3∶1 and the external water phase ratio was 70%, the force between the droplets of W/O/W emulsion was the strongest, and the particle size was the smallest, the absolute value of Zeta-potential was the largest, the protection of active substances was the strongest, and 28d storage stability index and rheological properties were the best. The development of emulsifier for W/O/W emulsion was helpful to improve its stability. Aiming to provide a strong basis for the use of soybean lipophilic protein as emulsifier, and further explore the effect of its interaction with methylcellulose on the emulsifying properties, the research result can also provide a theoretical basis for the application of soybean lipophilic protein and methyl cellulose in W/O/W emulsion system, and provide reference for improving the stability of bioactive substance delivery system.

Abstract:Owing to high center of mass and heavy tractor body, the high-power wheeled tractor has a tendency to bump when it drives on the bumpy farmland during high-speed transportation. Especially the frequency of the excitation from ground is approximately the inherent frequency of the front axle suspension, which will result in handling stability and ride comfort or even endangering security of its driving. Based on it, through comprehensively considering the simulations control of body vibration acceleration and displacement of suspension and the nonlinear control of suspension system in the process of filling a discharging oil, a damping scheme for front axle suspension of high-power wheeled tractor was put forward. Firstly, the front axle suspension damping system was designed, and a 1/4 tractor vibration model with front axle suspension was established. Secondly, based on the control characteristics of the front axle suspension, a hierarchical control algorithm based on the reference sky-hook and ground-hook model for active suspension system was proposed. The simulation model was constructed by using Matlab/Simulink and compared with the conventional PID algorithm. The simulation results indicated that the hierarchical algorithm was better than the PID control. Finally, the HILS platform of the control system and the indoor test platform of the front axle suspension system were built, at the same time, the suspension vibration control strategy gest verification was carried out. The test results showed that the hierarchical control algorithm based on the reference sky-hook and ground-hook model can quickly adjust the control parameters, the root mean square of the body vibration acceleration of the designed suspension system was reduced to about 2.36m/s2, which was 55.8% lower than that of the passive suspension. At the same time, the root mean square of the suspension dynamic deflection was limited to a small range, which was obviously better than passive suspension system, and met the vibration reduction requirements of the front axle suspension of high-power wheeled tractor. The test results were well matched with the simulation results, which verified the effectiveness of the vibration reduction scheme. Thereby, the research result can provide reference for the design and development of the front axle active suspension system for high-power wheeled tractor.

Abstract:As autonomous mobile machines become more intelligent, the trajectory planning of mobile robots in complex environments often faces the problem of obstacle avoidance failure due to the cluttered and irregular placement of obstacles. Trajectory planning of robot was reduced to optimization problem, that was, the objective function was defined, and then the constraint conditions were set according to the actual planning requirements of the mobile robot, and the appropriate solver was selected. Firstly, the constraint modeling of optimization, including the robot’s kinematics, geometric model, variable extremum constraint and obstacle collision avoidance model were considered. Then an optimization strategy was established to discretize variables by means of interval equipartition of variables, built-in interpolation points and variable description method based on Lagrange polynomial. And for the constraint failure caused by discretization, the variables were discretized by equidistance time and the penalty function was established, so as to realize effective obstacle avoidance. Finally, the stochastic fractal search algorithm was used to solve the above optimization problem. The simulation results showed that the method described can effectively solve the obstacle avoidance problem of mobile robots in complex environments. Also both satisfied the constraints of maximum speed and maximum steering angle. Compared with the existing classical algorithm in the simulation, the experimental results showed that the algorithm described had good robustness in the narrow environment with many obstacles.

Abstract:A type of SCARA parallel mechanism with double parallelogram branches was proposed, which included four identical branches and had the advantages of compact structure, high bearing capacity and stiffness. Firstly, the topological structure and degree of freedom of the mechanism were described based on Lie group theory. Secondly, the closed-loop vector equation was constructed to derive the forward/inverse position solution, and two numerical examples were used to verify the correctness of the position solution. By deriving the closed-loop vector equation with respect to time, the Jacobian matrix of the mechanism was obtained, and the mapping relations between the input angular velocity and the end output velocity, and between the input angular acceleration and the end output acceleration were established, and the numerical simulation analysis was carried out. Then, based on the inverse position solution, the limit boundary search method was used to solve the workspace of the mechanism, and the corresponding atlas was drawn for analysis. In order to clarify the rotation performance of the moving platform of the mechanism, the spatial distribution maps of the maximum and minimum rotation angles of the moving platform under different working planes were drawn. On this basis, the dimensional homogeneous Jacobian matrix was constructed with the help of characteristic factors, and the motion transmission performance of the mechanism was analyzed by two methods of condition number and operability. Based on the direct and indirect Jacobian matrices, three kinds of singular positions of the mechanism were analyzed systematically, and the conditions of singularity occurrence were clarified. Finally, the correctness and feasibility of the theoretical analysis and design results were verified by simulation experiments with Matlab and ADAMS software. The research result can provides theoretical basis for the subsequent optimization and prototype manufacturing of the SCARA parallel mechanism in future.

Abstract:In order to realize the compensation of large-scale pose disturbance and the isolation of medium high frequency vibration, a configuration of multi-dimensional orientation adjustment and vibration isolation platform was proposed. The mechanism consisted of three branches, each of which contained a closed-loop chain composed of active orientation adjustment and passive vibration isolation unit. Referring to the screw algebra and the influence coefficient theory, the kinematics model of the mechanism was established, and the first and second order influence coefficient of the mobile platform, the open-chain branch and the electric cylinder branch on the generalized coordinates were obtained. A dynamic model of active-passive separation form of the mechanism was established. On this basis, the modal of the mechanism was analyzed. The modal experiment of the principle prototype was carried out by pulse excitation. The experimental results showed that the measured natural frequency was close to the theoretical calculation value, which verified the correctness of the theoretical model. The experimental results of response characteristics showed that the principle prototype can compensate the pose disturbance in the low frequency. Combined with the passive vibration isolation in the medium high frequency, the principle prototype had the ability to adjust the orientation and isolate the vibration in a wide frequency band.

Abstract:Aiming at solving the problems of poor control accuracy, deficient anti-disturbance ability, and weak stability in agricultural drive motor, a sliding mode variable structure control strategy based on variable speed approaching rate was proposed. The motor control accuracy and stability in the motor control process were improved through the sliding mode variable structure control. In view of the problems of slow approaching speed, broad chattering fluctuation, and low control accuracy at the constant speed approaching rate in the convergence process of traditional sliding mode variable structure control, the variable speed approaching rate was studied for optimization and improvement. At the variable speed approaching rate, the problem of approach speed/buffeting fluctuation balance was effectively realized through introducing the system norm in the motor control process, which improved the control efficiency of the agricultural drive motor and ensures stability. In addition, because of the internal mechanical parameters and external load disturbance, which can have a detective influence on the speed control performance of the agricultural motor, an anti-disturbance method based on an extended sliding mode observer was designed to observe and compensate the internal parameters and external load disturbance in the motor control process. Through Matlab/Simulink simulation test and motor platform experiment, it can be proved that the control strategy proposed can complete the starting speed response within 0.1s in the starting process without overshoot, which effectively improved the control accuracy and response speed of agricultural drive motor. The designed disturbance observer improved its anti-interference ability and robustness. When the external load disturbance of 10N·m/-10N·m was received, the speed error can be eliminated within 5%, which effectively improved the stability and safety of the agricultural motor in the operation process.