• Volume 54,Issue 8,2023 Table of Contents
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    • >特约专稿
    • Research Review of Agricultural Equipment Automatic Control Technology

      2023, 54(8):1-18. DOI: 10.6041/j.issn.1000-1298.2023.08.001

      Abstract (1863) HTML (0) PDF 18.13 M (1391) Comment (0) Favorites

      Abstract:With the advancement of information and control theory, automatic control technology has been extensively applied in the realm of agricultural machinery. This has significantly enhanced the intelligence, modernization, and scalability of agricultural production. The two central components of intelligent agricultural machinery's automatic control technology are motion control and operation control. These elements ensure safe navigation and precise operation of unmanned agricultural machinery in complex environments. The research progress in speed control and steering control of intelligent agricultural machinery was discussed, which formed the foundation of its motion control. Additionally, navigation tracking control was highlighted as a crucial aspect of intelligent agricultural machinery's motion control. A comprehensive summary of automatic navigation tracking motion control methods was also provided based on geometric models, kinematics models, and model-independent methods. The control mechanisms of intelligent agricultural machinery during various stages such as cultivation, planting, management, and harvesting were further analyzed. It particularly focused on the multi-machine cooperative operation control method. In conclusion, it was suggested that future developments in the automatic control technology of intelligent agricultural machinery should focus on constructing more precise mathematical models of agricultural machinery, researching advanced chassis motion control technology for complex scenarios, developing agricultural machinery control technology that deeply integrates AI and control theory, and enhancing multi-machine collaborative control technology that combines agricultural machinery and agronomy.

    • >农业装备与机械化工程
    • Design and Test of Key Components of Potato Soil-crushing Site Preparation Machine

      2023, 54(8):19-29. DOI: 10.6041/j.issn.1000-1298.2023.08.002

      Abstract (1343) HTML (0) PDF 2.85 M (908) Comment (0) Favorites

      Abstract:In view of the problems faced in the land preparation operation in northeast China, such as more clods, serious soil stubble and thickened plow bottom layer, a driven soil crushing and preparation combination machine mainly applicable to potato fields was designed according to the power conditions of the existing Dongfanghong-75 and 802 tractors. This was a new type of machine designed according to the advanced foreign soil conservation tillage method and developed by combining the soil conditions of the northeast and the requirements of potato field preparation. The overall structure and working principle of the machine were described. By designing the soil crushing roller, the author clarified and analyzed the soil crushing roller motion process, the resistance of the wedge-shaped teeth during the working process of the soil crushing roller and the power required during the operation of the soil crushing roller. Based on EDEM discrete element simulation technology, a component-soil simulation model was established with soil crushing rate as test index, and end deflection angle of crushing straight tooth, length of crushing straight edge and unit speed as test influencing factors for simulation experiments. The field tests were conducted on the basis of simulation. The test results showed that the designed soil crusher had a soil crushing rate of 98.45%, an average tillage depth of 14.5cm, a unit speed of 5.7m/s and a crushing roller power consumption of 19.24kW, which proved to have a good operation effect and met the requirements of potato field preparation.

    • Design and Experiment of Pneumatic Adaptive Seeding System for Small Particle Size Seeds

      2023, 54(8):30-41. DOI: 10.6041/j.issn.1000-1298.2023.08.003

      Abstract (1015) HTML (0) PDF 7.47 M (636) Comment (0) Favorites

      Abstract:The suitable working negative pressure of pneumatic seed metering device is related to working speed and seed size. However, the working pressure of the seeding system of the existing pneumatic seeder is frequently set to a fixed value which cannot be optimized and adjusted timely. A pneumatic adaptive seeding system was designed based on the positive and negative pressure combined small particle size seeds metering device. The system was controlled by STM32 single-chip microcomputer. By adjusting the working speed of the metering device with speed and monitoring the seeding performance in real time, the working negative pressure of the metering device can be dynamically adjusted, and the actual working negative pressure of the metering device can be continuously maintained as the optimal value under the corresponding working conditions, so as to realize the optimal control of the seeding performance. The results of the bench test showed that the qualified index of the pneumatic adaptive seeding system was greater than 92% and the missing index was less than 6 % under different operating speeds and seed sizes. Compared with the fixed air pressure setting and the open-loop control air pressure adjustment method, the qualified index of seeding was increased by 9.02 and 3.84 percentage points respectively, the multiple index was decreased by 8.44 and 1.99 percentage points respectively, and the missing index was decreased by 0.58 and 1.86 percentage points respectively. Field test showed that the stability coefficient of plant spacing of the seeder equipped with a pneumatic adaptive seeding system was 14.27%, and the consistent coefficient of variation of the number of seedlings in each row was 7.03%. The findings can provide a technical reference for the improvement of the continuous and stable single-grain precision seeding ability of the pneumatic seeder.

    • Design and Experiment of Rapeseed Wide-width Folding Shallow-rotation Combined Precision Direct Seeder

      2023, 54(8):42-52,109. DOI: 10.6041/j.issn.1000-1298.2023.08.004

      Abstract (926) HTML (0) PDF 7.73 M (640) Comment (0) Favorites

      Abstract:To solve the problems of complex process and low efficiency in rape seeding operation in the rice-oil rotation cropping area in mid-lower Yangtze River, a wide-width folding shallow-rotation combined precision direct seeder for rapeseed was designed, which can realize the functions of opening furrows, shallow rotation, precision seeding of rapeseed, covering soil. The basic structure and working process of the machine were analyzed and determined, and the kinematics and the dynamics analysis on the hydraulic folding mechanism were carried out. The Matlab software was used to determine the structural parameters and the maximum load of the hydraulic cylinder, and the hydraulic folding control system was designed based on the hydraulic oil circuit of the tractor. According to the operational requirements of ditch opening depth, width, plowing depth, and uniformity of soil cover, the speed range of the cutter shaft was 360~480r/min, and the rotation radii of the ditching cutter and shallow rotary cutter roller were determined to be 320mm and 175mm, respectively, the number of ditching cutters was 8. The value range of the structural parameters of the soil dividing deflector was analyzed, the orthogonal test of the uniformity of the soil covering under different structural parameters of the soil dividing deflector was carried out by using EDEM software, and the regression mathematical model of the uniformity of covering soil on the installation distance of the soil dividing deflector, the length of the deflector and the angle of soil dividing plate was established. The simulation test results showed that when the installation distance of the soil dividing guide plate was 200mm, the length of the guide plate was 600mm, and the angle of the soil dividing plate was 60°, the uniformity of the covering soil can reach 93.33%. The field test results showed that when the forward speed of the unit was 3.6km/h, the depth of the furrow was 150mm, and the rotational speed of the cutter shaft was 480r/min, the seed bed crushing rate after operation of the rapeseed wide-width folding shallow-rotating precision combined direct seeding machine was 91.62%, the straw burial rate was 90.72%, the box surface flatness was 13.17mm, and the seedling formation rate was 73.89%. The operation effect of the wide-width folding shallow-rotation combined precision direct seeder can meet the requirements of rapeseed direct seeding operation. The research result can provide a approach for the design of wide efficient seed drill for rapeseed.

    • Design and Experiment of Seed Disperser for Ning-guo Radix peucedani Based on Rocky Dem

      2023, 54(8):53-64. DOI: 10.6041/j.issn.1000-1298.2023.08.005

      Abstract (898) HTML (0) PDF 9.78 M (626) Comment (0) Favorites

      Abstract:The seeds of Ning-guo Radix peucedani are light, heterogeneous and irregular with problems of poor mobility and easy breakage. Based on the seed physical parameters and agronomic requirements of Ning-guo Radix peucedani seeds, a horseshoe wheel strip planter was designed. Analysis of the seed filling process showed that horseshoe holes can improve seed mobility and reduce seed damage. Single factor test was done by using Rocky Dem discrete element simulation software. Analysis of collision energy between seeds and seed dispenser wheels was carried out by using the Particle Energy Spectra module to predict seed breakage. A quadratic regression orthogonal rotational combination test was carried out with seed discharge wheel speed and seed guide tilt as test factors. Parameters were optimized by using regression models. The results showed that when the seed discharge wheel speed was 31.75r/min and the seed guide tilt was 31.05°, the seed discharge performance was optimal with a coefficient of variation of 11.37% for seed discharge uniformity and 1.02% for discharge stability. Bench experiments were conducted to verify the effect of different rounding radii of the type hole on seed breakage. The results were in agreement with the simulation test results, which proved the feasibility of the method. The results of the field test of the seed disperser were consistent with the bench tests and met the agronomic requirements for growing Ning-guo Radix peucedani. A prediction method was proposed for the effect of different factors on seed breakage.

    • Design and Experiment of Slotted-tooth Spoon Hole and Air-assisted Precision Centralized Metering Device for Sesame

      2023, 54(8):65-76. DOI: 10.6041/j.issn.1000-1298.2023.08.006

      Abstract (893) HTML (0) PDF 6.79 M (587) Comment (0) Favorites

      Abstract:Considering the practical problem that the poor mobility and low sphericity of sesame seeds make it difficult to fill seeds during seeding process and to achieve precision seeding, based on the mechanical and physical properties and parameters and the demand of planting agronomy for sesame, a precision metering device for sesame seeds was designed, which used slotted-tooth spoon holes to fill seeds and air delivery to assist seed feeding. The key structural parameters of seed metering device were determined, and the mechanical model of seed particle group during seed filling, seed carrying and seed supplying was established. The performance of seed metering device was simulated and optimized by using discrete element software EDEM. The influence of the hole depth, the angle of right wall of the shaped hole and the angle of slotted-tooth spoon hole on variation coefficient of seeding amount uniformity in each row and average sowing amount per minute were studied by Box-Behnken response surface optimization method and three-factor and three-level orthogonal simulation experiment. The variation coefficient of seeding amount uniformity in each row and average sowing amount per minute were 1.69% and 3.7g/min, respectively, when the hole depth was 1.92mm, the angle of the right wall of the shaped hole was 8.4°, and the angle of slotted-tooth spoon was 28.6°. A two-factor and three-level bench test of seed metering device performance was carried out. The test factors were the rotation speed of seed metering shaft and the filling height of the seed layer. The variation coefficient of total seeding stability and the variation coefficient of seeding amount uniformity in each row were taken as the test evaluations. The results showed that seed metering device had the best performance when the rotation speed of seed metering shaft was 15r/min and the filling height of the seed layer was 10mm. And variation coefficient of total seeding stability, the variation coefficient of seeding amount uniformity in each row were 1.62% and 0.40%, respectively, which met the agronomic requirements of sesame planting. The field experiment demonstrated that the uniformity coefficient of variation of the number of seedlings in each row was lower than 4% and the average planting density was 36 plants/m2, when the forward speed of seed metering device was 2.9km/h. The research result can provide a reference to improve the structure of metering device for sesame seeds.

    • Design and Experiment of Seedling Picking Mechanism for Helical Gear-Non Circular Gear Planetary Gear System

      2023, 54(8):77-86. DOI: 10.6041/j.issn.1000-1298.2023.08.007

      Abstract (811) HTML (0) PDF 8.91 M (563) Comment (0) Favorites

      Abstract:There is a problem of insufficient pushing angle in the seedling picking mechanism of the complete non circular gear planetary gear system, while there is an impact on the seedling picking mechanism of the incomplete non circular gear system. A non circular complete gear planetary gear system seedling picking mechanism was designed with a large pushing angle that met the requirements of vegetable seedling picking. Based on Fourier function, a quadratic unequal amplitude transmission ratio curve was designed, and the influence of Fourier function coefficient on the seedling path was analyzed. The change relationship of Fourier function coefficient on the transmission ratio curve and the angular displacement of the driven gear was studied. The change law of Fourier coefficient on the dynamic parameters of the seedling picking mechanism was revealed. The change relationship of Fourier function coefficient on the seedling picking angle and the seedling pushing mechanism was deduced. Manufacturing and assembling the seedling picking mechanism. Based on the virtual prototype and high-speed camera technology, the rotation test of the seedling picking mechanism was carried out. The feasibility of the design of seedling experimental values of the seedling picking trajectory was done. The seedling picking mechanism was tested on the platform. The success rates of the seedling picking mechanism at different rotational speeds (40r/min, 50r/min, 60r/min) were 94%, 90% and 88%, respectively. The feasibility of the design of the seedling picking mechanism was further verified by the seedling picking experiment.

    • Construction and Experiment of White Box Model for Energy Consumption of Agricultural Multi-rotor UAV Operation

      2023, 54(8):87-96. DOI: 10.6041/j.issn.1000-1298.2023.08.008

      Abstract (982) HTML (0) PDF 3.83 M (564) Comment (0) Favorites

      Abstract:In order to reduce the problem of limited flight time of UAVs due to limited energy, it is necessary to study the operational energy consumption of agricultural UAVs during flight. Taking agricultural multi-rotor UAV as the research object, the white-box modeling method was used to construct the total flight efficiency model of agricultural UAV according to the principle of each component of the power system, and then an operational energy consumption model was established for agricultural UAV according to the flight characteristics of agricultural UAV, and the data obtained were verified by grouping tests of three dynamic parameters, namely speed, load and range of agricultural UAV. The results showed that the model had a high accuracy, with a maximum average error of about 6.582% and a median maximum absolute error of about 7.654%. Finally, each parameter of the model was analyzed and the model correction coefficient was introduced to correct the model, and the accuracy of the corrected model was reduced by about 3.092 percentage points of the maximum mean error and about 3.612 percentage points of the median error compared with the maximum mean error before the correction, which was significant after the correction. The theoretical model constructed can be used for the calculation and prediction of agricultural UAV operation energy consumption, and the corresponding operation energy consumption can be obtained and optimized before planning the UAV mission, and it can also be adapted to other rotor models with different controllers, which had certain application value.

    • Autonomous Basket Searching Method for Orchards Transporter Based on VINS-MONO and Improved YOLO v4-Tiny

      2023, 54(8):97-109. DOI: 10.6041/j.issn.1000-1298.2023.08.009

      Abstract (1001) HTML (0) PDF 10.76 M (721) Comment (0) Favorites

      Abstract:A method for orchard autonomous basket searching based on VINS-MONO and improved YOLO v4-Tiny was proposed for the scenario of orchard transporter fruit harvesting and autonomous transportation operations. Firstly, the position of the orchard transporter was estimated in real time based on the VINS-MONO visual inertial odometry calculation method. Then based on the improved YOLO v4-Tiny target detection algorithm, real-time target detection of the fruit basket was performed on the image data, and its depth information was obtained. Nextly, the position of the identified fruit basket was estimated based on the current position pose of the transporter, the depth information of the fruit basket and the parameters of the depth camera. Finally, based on the principle of cubic B spline curve fitting, the path of the identified fruit basket was fitted in real time, using the position of the identified fruit basket as the control point, to provide route guidance for the autonomous fruit basket search of the orchard transporter. The test results showed that the average recognition accuracy of the improved YOLO v4-Tiny fruit basket recognition model was 93.96%, the average inference time was 14.7ms, the measurement error of the fruit basket distance within 4m was less than 4.02%, the measurement error of the fruit basket angle was less than 3°, the measured driving speed of the orchard transporter was 3.3km/h,the average update time of the fruit basket search route was 0.092s, and the transporter could stably achieve autonomous basket searching in two operating environments: fruit tree rows and orchard roads. This method could provide autonomous basket finding path guidance for orchard transporter and provide research reference for visual navigation of orchard transporter.

    • Real-time Estimation Method of Tire Dynamics Parameters for Sliding Steering Robots in Orchards

      2023, 54(8):110-121,192. DOI: 10.6041/j.issn.1000-1298.2023.08.010

      Abstract (896) HTML (0) PDF 5.07 M (521) Comment (0) Favorites

      Abstract:The vertical load and lateral force parameters of sliding steering wheeled robot tires vary greatly and are difficult to estimate in real time due to the influence of orchard road surface undulations and tire adhesion capacity changes. The existing sliding steering controller is designed to simplify the tire dynamics parameters, which leads to the problem of low stability of robot attitude control. A real-time estimation method for the vertical load of sliding steering wheeled robot tires on unpaved roads and an algorithm for real-time estimation and optimal distribution of tire driving force were proposed. Firstly, an ideal plane for the static calculation of the sliding steering process and a four-wheel vertical load estimation method based on this plane were proposed; secondly, a small lateral deflection angle lateral force estimation method based on the Fiala wheel-tire dynamics model was proposed; and the steady-state dynamics equations of the sliding steering wheeled robot ramp and the real-time tire drive force estimation method were established; finally, the optimal real-time distribution model of the driving force was constructed based on the tire utilization rate. In order to verify the method, an ADAMS-based sliding steering wheeled robot dynamics model was developed for comparison and a testing device was built to verify the vertical load and lateral force estimation methods. The results showed that the accuracy of the real-time tire vertical load estimation method was more than 95% and the accuracy of the real-time lateral force estimation method was more than 85%, and the tire drive force optimization method based on the tire vertical load and lateral force reduced the tire utilization rate from 96.25% to 93.75%, which improved the tire adhesion margin and attitude control stability.

    • Design and Experiment of Cutting Threshing Integrated Type Header for Harvesting of Edible Sunflower

      2023, 54(8):122-131. DOI: 10.6041/j.issn.1000-1298.2023.08.011

      Abstract (1011) HTML (0) PDF 7.11 M (595) Comment (0) Favorites

      Abstract:In view of the problems such as large loss of mechanical harvesting of edible sunflowers, seeds skin easy scratching in transporting of sunflower discs and seeds seriously broken in threshing, a threshing device was added to the traditional cutting header, and a combined harvesting cutting header device was designed which integrated the functions of dividing, lifting grain, reel, cutting, transporting and threshing by the biomechanical characteristics of edible sunflower, planting mode and requirements of mechanical harvesting of edible sunflowers. The edible sunflower discs were threshed on the cutting header, which effectively shortened path of sunflower discs transport and laid the foundation for the subsequent improvement of cleaning quality. In order to reduce the loss of cutting header, a no-row reel was designed according to posture of edible sunflower plant during the maturity period. A divider with a side inclination angle of 30° was designed, while the soft brushes were added between adjacent divider to collect the collision splashed seeds. To reduce seed breaking in threshing, an axial flow spiral drum type threshing device was designed. Based on the kinetic and kinematic analysis of material throwing process, it was concluded that the sunflower discs entered threshing device more smoothly when the inclination angle of the screw conveyor switch-plate was determined to be 18°. In order to verify the feasibility of the design of cutting header structure, field experiment was conducted. The results showed that the combined harvester could meet the requirements of sunflower harvesting with a stubble height of 700mm and five different speed conditions in the range of 1.21~2.11m/s. The loss rate was no more than 3%, the un-threshing rate was no more than 2% and the breaking rate was no more than 3%. The research result can provide technical reference for the research and development of combined sunflower harvesting machinery and equipment.

    • Design and Experiment of Pneumatic-Mechanical Combined Leaves Removing Machine for Artemisia selengensis

      2023, 54(8):132-142. DOI: 10.6041/j.issn.1000-1298.2023.08.012

      Abstract (841) HTML (0) PDF 7.55 M (571) Comment (0) Favorites

      Abstract:Artemisia selengensis, whose edible part is stem and several fresh leaves at the top, is a characteristic vegetable in China. Most of the leaves need to be removed before the sale. However, it is hard to remove the easy folding leaves without damaging the fresh stem. Existing leaves removing operation of the Artemisia selengensis is still rely on the hand labor with high cost and labor consumption. To improve the mechanization level of leaves removing operation, a pneumatic-mechanical combined leaves removing machine for the Artemisia selengensis was designed. The effective removing of leaves from the stem was realized through the pneumatic adsorption guidance of leaves suction drum and the mechanical pulling of leaves pulling roller. Characteristics based on the defoliation machine was designed. The geometric parameters of Artemisia selengensis were statistically analyzed while the pull resistance of leaves in forward, normal, and reverse pulling were tested. It was indicated that the reverse pulling method was better to remove the leaves. The analysis of the structural parameters and operating parameters of the key components such as the leaves suction drum and pulling roller was carried out. The air flow field of the leaves suction drum was simulated based on CFD. Combined with the simulation orthogonal test, the axial spacing of the suction hole was determined to be 10mm, the circumferential distribution angle was 10°, the number of effective holes was 121, the diameter of the suction hole was 4mm with the depth of 4mm, and the relative height of the leaves pulling roller was 30mm. By taking the leaves suction drum speed, the leaves pulling roller speed and feeding rate as experimental factors, taking the removal rate and breaking rate of leaves as evaluation indexes, the quadratic regression orthogonal experiment was conducted. The regression mathematical model was established. The optimal parameter combination was obtained as leaves suction drum speed of 77r/min, leaves pulling roller speed of 65r/min,and feeding rate of 40mm/s. Under the optimal parameter combination condition, the leaves removal rate and breaking rate were 94.32% and 12.93%, respectively. The operation efficiency could reach 12.3kg/h, which met the production of the Artemisia selengensis. The research result could provide a reference for the structure improvement and optimization of leaves removing machine for Artemisia selengensis.

    • Design and Experiment of Electrostatic Impurity Removal Device for Honeysuckle

      2023, 54(8):143-154. DOI: 10.6041/j.issn.1000-1298.2023.08.013

      Abstract (761) HTML (0) PDF 6.32 M (607) Comment (0) Favorites

      Abstract:Based on electrostatic separation technology, an electrostatic removal device for honeysuckle was designed to solve the problem of poor removal of woven bag filaments in the removal process. Through theoretical analysis, the critical conditions for the trajectory separation of honeysuckle and woven bag filaments in the electrostatic field were deduced, and the feasibility of electrostatic separation technology for honeysuckle impurity removal was verified. Single-factor experiments and COMSOL simulations were used to investigate the effects of electrostatic electrode shape, output voltage U of the high voltage electrostatic generator, electrostatic electrode angle α, the distance L between the electrode and the roller, and roller speed N on the removal performance. The electrode shape was determined as a circular arc, and the αwas set to be 45°. The quadratic regression equations for the removal rate and the false removal rate were established by the Box-Behnken experiment, respectively. Response surface analysis was used to explore the influence of each experiment factor on the experiment index. The optimum operating parameters of the device were determined to be U=11.9kV, N=28r/min, and L=60mm. The results of the bench experiment showed that the impurity and false removal rates were 94.47% and 0.89% respectively, which met the requirements for removing impurities from honeysuckle. The device proposed effectively removed woven bag filaments from honeysuckle and may provide a reference for the design of similar herb removal devices.

    • Design and Test of Flapping Hydrofoil Bionic Water Pumping Device

      2023, 54(8):155-162. DOI: 10.6041/j.issn.1000-1298.2023.08.014

      Abstract (842) HTML (0) PDF 4.10 M (494) Comment (0) Favorites

      Abstract:Aiming at the problem of insufficient hydrodynamic force in the small branching river in the plain river network, a flapping-wing bionic water pumping device was designed, by controlling flapping wings to complete the two degree of freedom coupling motion of heave and pitch, the water in the closed channel was mechanically pressurized, achieving one-way pumping of water, to meet the demand for large flow and high efficiency water transmission under very low head conditions. A flapping-wing model was established based on the tuna tail fin and rectangular flat plate. The finite volume method (FVM) and overlapping grid technology were used to carry out three-dimensional numerical simulation of flapping hydrofoil with different characteristic chord lengths and contours, and the pump water test of tail fin and rectangular flapping hydrofoil was compared. The results showed that with the increase of the characteristic chord length of the flapping hydrofoil, the average thrust coefficient in the cycle was increased, corresponding to an increase in the vortex strength of the wake region vortex ring. However, its pumping efficiency was slightly decreased. Under the same area constraint, the flapping hydrofoil with the characteristic profile of the tail fin improved the pumping flow and efficiency of the device compared with the rectangular flapping hydrofoil. When the test flapping frequency was 0.7Hz, the stable average flow rate of the tail fin flapping hydrofoil flow field was 28.44cm/s, which was 13.6% higher than 25.13cm/s of the rectangular flapping hydrofoil.

    • Solid-liquid Two-phase Flow of Mixed Particles in Vortex Pump Based on CFD-DEM

      2023, 54(8):163-170,248. DOI: 10.6041/j.issn.1000-1298.2023.08.015

      Abstract (1225) HTML (0) PDF 8.99 M (594) Comment (0) Favorites

      Abstract:In order to explore the mechanism of solidliquid twophase flow in the folded-blade vortex pump, based on the computational fluid dynamics-discrete element method (CFD-DEM) coupling algorithm, the rapeseed and soybean particles were mixed in equal proportion, and the solid-liquid two-phase flow numerical simulation and experimental research of the vortex pump were carried out under different flow conditions and volume concentrations. The internal flow law and particle distribution characteristics of the folded blade vortex pump were also studied. Under the condition of small flow rate, the rotating reflux length in the inlet pipe was longer, and the disturbance to the inlet flow was greater. As the flow rate was increased, the reflux length of the inlet pipe was decreased gradually. With the increase of flow rate, the number of vortices on the front surface of the impeller was increased first and then decreased, and gradually gathered towards the turning point. The particles in the pump were affected by the combined action of circulating flow and through flow. The particles in the center of the inlet pipe were mainly affected by the through flow, directly passing through the vaneless cavity and impacting the impeller inlet. The particles near the pipe wall were greatly affected by the circulating flow. The particle distribution in the leafless cavity showed that the concentration in the center was the highest, the concentration in the middle was decreased gradually with the increase of the outer diameter, and the concentration in the outer edge was increased slightly. The number of particles in the front half of the impeller was significantly less than that in the rear half of the impeller. The particles moved along the folding edge of the first section of blade, and began to separate at the folding point, and no longer followed the folding edge of the second section. Under different working conditions, the pump inlet had different degrees of rotational reflux, resulting in a decrease in the inlet flow area. The existence of circulating flow made the particles in the vaneless cavity and the inlet pipe fully rotated, the pumping capacity was enhanced, and the blockage was not easy to occur.

    • >农业信息化工程
    • Land Use Differentiation in Typical Main Grain Producing Areas along Yellow River Based on Time Series Processes

      2023, 54(8):171-179. DOI: 10.6041/j.issn.1000-1298.2023.08.016

      Abstract (652) HTML (0) PDF 6.15 M (494) Comment (0) Favorites

      Abstract:By exploring the laws of land use changes in the main grain producing areas, the abnormal land use behaviors can be identified and the allocation of grain production can be optimized. However, current research primarily focuses on patterns rather than processes, and simulations rather than quantitative analyses, resulting in insufficient data. Multi-period land use sequence data was used to quantitatively reveal the characteristics of land use change processes in the main grain producing areas along the Yellow River in Henan Province since 1980. Time-series processes, time-space grid modeling, cumulative dynamic degree models, spatial point pattern analyses, and other methods were employed to deepen understanding of the internal laws and multi-dimensional expressions of land use change. The results showed that since 1980, there was significant temporal and spatial heterogeneity in land use along the Yellow River. The area of cultivated land was decreased slowly, urban construction land was expanded, rural residential areas were grown slowly, the land for water areas was firstly decreased and then increased, and the forest land was increased first and then decreased. The land development activities along the Yellow River and around the county built-up areas were intensified and become more frequent. The time sequence process was greatly affected by the distance from roads and rivers, but the impact types and scope were different. The land dynamic change types Ⅰ, Ⅱ, and Ⅲ, located close to the linear elements, were in the aggregation distribution state. With the expansion of the buffer zone, the aggregation degree of type Ⅰ was firstly increased and then decreased, while types Ⅱ and Ⅲ continued to be weaken. The temporal process was greatly affected by the spatial scale. The stronger the change was, the weaker the influence of the spatial scale was. All types were in a discrete state at 1km spatial scale, but the aggregation was increased gradually with the increase of spatial scale. The timeseries process research method based on cumulative dynamic degree could better reveal the information of long-time series land use change, thus deepening the understanding of land use changes.

    • Plastic-mulched Farmland Recognition in Loess Plateau Based on Sentinel-2 Remote-sensing Images

      2023, 54(8):180-192. DOI: 10.6041/j.issn.1000-1298.2023.08.017

      Abstract (1030) HTML (0) PDF 9.68 M (567) Comment (0) Favorites

      Abstract:Plastic film mulching has greatly increased crop yields in arid and semi-arid regions of China, but also caused a lot of environmental problems. Thus, timely and accurate mapping of plastic-mulched farmlands through remote sensing technology is helpful for governments to plan agricultural production and deal with micro-plastic pollutions. However, the existing recognition methods based on single-temporal remote-sensing images with low and medium resolutions are unable to accurately recognize the plastic-mulched farmlands in the Loess Plateau due to its complex terrain and fragmented agricultural landscapes. In order to accurately recognize plastic-mulched farmlands in the Loess Plateau, different feature set combination schemes and multi-temporal image combination schemes applicable to recognize plastic-mulched farmlands in the Loess Plateau were constructed based on Sentinel-2 remote-sensing images and random forest algorithm. Three testing areas were selected for constructing recognition schemes mentioned above, including Linxia County in Gansu Province, Pengyang County in Ningxia Hui Autonomous Region, and Shanyin County in Shanxi Province, and one validation area of Xunyi County in Shaanxi Province were chosen as the scheme validation area. Firstly, based on the random forest algorithm, the optimal feature set combination scheme with the highest recognition accuracy was selected from seven different feature set combination schemes for each growth stage (sowing stage, flourishing stage, and harvesting stage). Then, based on the remotesensing images of the three different crop growth stages and their corresponding optimal feature set combination schemes, different multi-temporal image combination schemes were constructed to recognize the plastic-mulched farmlands, and then the optimal multi-temporal image combination scheme was selected. Finally, the effectiveness of the optimal feature set combination scheme and multi-temporal image combination sheme for recognizing plastic-mulched farmlands was verified in Xunyi County, and the spatial distribution maps of plastic-mulched farmland in each research area were drawn. The results showed that the visible bands (B2, B3, and B4) and the short-wave infrared bands (B11 and B12) in the spectral feature set of Sentinel-2 remote-sensing images, the normalized difference bareness and built-up index (NDBBI), normalized difference water index (NDWI), bare soil index (BSI), normalized difference built-up index (NDBI), and modified normalized difference water index (MNDWI) in the index feature set, and the sum average (savg) and correlation (corr) in the textural feature set can be used as optimal input feature variables for recognizing plastic-mulched farmlands. Among the seven different feature set combination schemes, the “spectum + index” scheme was the optimal scheme for recognizing plastic-mulched farmlands during the sowing and harvesting stages. The F1-score for plastic-mulched farmland recognition in these two stages in the four study areas was greater than 87% and 57%, respectively. The “spctrum + index + texture” scheme was the optimal scheme for recognizing plastic-mulched farmlands during the flourishing stage with F1-score greater than 71% in the four study areas. Generally, the plastic-mulched farmland recognition accuracy based on multi-temporal remote-sensing images was higher than that based on single-temporal remote-sensing images. Among different multi-temporal image combination schemes, “sowing stage + flourishing stage + harvesting stage” can be used as the optimal scheme for plasticmulched farmland recognition, and the F1-score for recognizing plastic-mulched farmlands in the four study areas was greater than 92%. In general, plastic-mulched farmlands in the Loess Plateau can be accurately recognized based on random forest algorithm and the optimal feature set combination schemes and multi-temporal image combination scheme.

    • Crop Identification in Mature Stage with Remote Sensing Based on NDVI-NSSI Space and HSV Transformation

      2023, 54(8):193-200. DOI: 10.6041/j.issn.1000-1298.2023.08.018

      Abstract (758) HTML (0) PDF 4.63 M (495) Comment (0) Favorites

      Abstract:Identification of mature crops plays an important role in crop area estimation, agricultural production, and yield statistics. To provide a simple method for identification of crop at mature stage with remote sensing, the method based on normalized difference vegetation index (NDVI)-normalized spectral separation index (NSSI) space and Hue saturation value (HSV) transformation was proposed by using Sentinel-2A data. Fengyang County located in Chuzhou City, Anhui Province, was selected as study area. The pure pixel of photosynthetic vegetation, non-phototrophic vegetation and bare soil were estimated by using the NDVI-NSSI space firstly. Coverage of non-phototrophic vegetation and the distribution of mature crops were estimated by using spectral mixture analysis method. As wheat and rape had the same maturity period in the study area, HSV transformation was used to estimate the distribution of rape by using the Sentinel-2A data at the flowering stage of rape, and the mature wheat and rape was identified. The results were compared with ground observation data and auxiliary data, the accuracy of wheat and rape was 95.34%, and the Kappa coefficient was 0.904, which was higher than that of support vector machine method (accuracy was 91.66%, Kappa coefficient was 0.813) and the decision tree classification method (accuracy was 92.39%, Kappa coefficient was 0.838). The results indicated that non photosynthetic vegetation could be separated from soil background areas by using the NDVI-NSSI space and HSV transformation, and mature wheat and rape could be identified. The method can be used with less data demand and easy operated, which can provide idea and method for extracting bare soil during crop maturity and features with similar spectra to bare soil.

    • Inversion of Soil Salt Content Based on Texture Feature and Vegetation Index of UAV Remote Sensing Images

      2023, 54(8):201-210. DOI: 10.6041/j.issn.1000-1298.2023.08.019

      Abstract (850) HTML (0) PDF 3.98 M (515) Comment (0) Favorites

      Abstract:The acquisition of farmland soil salt information based on UAV remote sensing technology provides a rapid, accurate and reliable theoretical basis for salinization management. The soil salt content of 0~20cm from the sampling point was collected on the test ground of Shahao canal irrigation field in Hetao Irrigation District, Inner Mongolia, and the images were collected by M600 hexarotor UAV platform equipped with Micro-MCA multispectral camera. Otsu algorithm was used to classify the multi-spectral images (soil background and vegetation canopy). Based on the classification results, the spectral index and image texture features before and after removing the soil background were extracted respectively. The soil salt content monitoring model was constructed by support vector machine (SVM) and extreme learning machine (ELM). The four modeling strategies were as follows: spectral index of the soil background was not removed (strategy 1); spectral index of the soil background was removed (strategy 2); spectral index of the soil background was not removed + image texture features (strategy 3); spectral index of the soil background was removed + image texture features (strategy 4). The optimal variable combination was selected by comparing the model accuracy of the four modeling strategies. The results showed that the inversion accuracy of soil salt content calculated by strategy 3 and strategy 4 was higher than that of strategy 1 and strategy 2, and their validation sets R2v were 0.614, 0.640, 0.657 and 0.681, respectively. Therefore, it was of great significance to use image texture feature and vegetation index to improve the inversion accuracy of soil salt content. By comparing strategies 3 and 4, the image texture feature + vegetation index was affected by soil background. The accuracy of the strategy 4 was lower than that of the strategy 3, whose R2v was 0.614 and 0.657, respectively. The optimal model for each variable processing was ELM model, and the modeling sets R2c were 0.625, 0.644, 0.618, 0.683, and the standard root mean square errors were 0.152, 0.134, 0.206 and 0.155, respectively. Compared with the SVM model, the ELM model improved the inversion accuracy of soil salt content.

    • Production Method of Land Cover Data Based on GEE Cloud Platform and Data Fusion

      2023, 54(8):211-217. DOI: 10.6041/j.issn.1000-1298.2023.08.020

      Abstract (800) HTML (0) PDF 4.68 M (491) Comment (0) Favorites

      Abstract:Land cover data are important basic data for activities such as geographic monitoring of national condition, ecosystem assessment, and land spatial planning. Remote sensing computing cloud platforms such as GEE, PIE, and Microsoft Planetary Cloud have rich data sources and powerful computing power. Using the GEE cloud platform to integrate multiple sets of public products to produce training samples can significantly reduce the cost and cycle of product updates, which has important research value. The Huaihe River Basin was taken as a research area. The 2020 10m resolution land cover data stored on the GEE platform by European Space Agency (ESA) and Environmental Systems Research Institute (ESRI) were used as training sample data sources. Sentinel-1 radar and Sentinel-2 multispectral images were selected to construct the feature space, and random forest classification method was used to generate a 10m resolution land cover data. To validate the effectiveness of the method, two sets of comparative experiments were conducted. In experiment 1, totally 1116 randomly selected sample points with consistent categories from ESA and ESRI products were used as training samples, and the accuracy of the product and multiple sets of public products were verified through visual interpretation. The results showed an overall accuracy of 80.35% for the product, with an improvement of 2.89~8.94 percentage points compared with the overall accuracy of the public products. It also provided a more detailed depiction of partial characteristics. By incorporating radar imagery with Sentinel-2, the overall accuracy was improved by 3.52 percentage points, indicating the clear benefits of radar imagery as an auxiliary data source. Experiment 2 set up eight sets of training samples with different numbers, and used manual interpretation, ESA, ESRI, DW, and GlobeLand30 as reference data sources to study the impact of different training sample sizes and reference data sources on the overall accuracy of classification products. The results showed that as the training sample size was increased, the improvement in overall accuracy based on the five different reference data sources gradually was decreased and reached a relatively stable level. The research results indicated that by utilizing public land cover data and massive remote sensing images on the GEE platform, high-quality training samples can be quickly extracted to produce higher quality 10m resolution land cover data. The method had significant practical and promotional value.

    • Estimation of Winter Rapeseed Above-ground Biomass Based on UAV Multi-spectral Remote Sensing

      2023, 54(8):218-229. DOI: 10.6041/j.issn.1000-1298.2023.08.021

      Abstract (857) HTML (0) PDF 8.65 M (625) Comment (0) Favorites

      Abstract:Above-ground biomass (AGB) is an important index to judge the growth and development of crops. Rapid, accurate and non-destructive remote sensing monitoring of AGB at different growth stages of crops is of great significance to precision agricultural production. A field experiment was carried out in Guanzhong area of Northwest China. Winter rapeseed under different water and nitrogen treatments was used as the research object. The multi-spectral images of winter rapeseed in vegetative and reproductive growth periods were obtained by UAV, and the AGB measured data of winter rapeseed were obtained by field experiment. The shadow and soil background in multi-spectral image were masked by threshold method, and the reflectance of each band was extracted to construct vegetation index. The correlation analysis between the measured data of winter rapeseed AGB and spectral variables was carried out, and the top eight spectral variables with the absolute value of correlation coefficient in each growth stage were selected as input variables. The AGB estimation model of winter rapeseed at different growth stages was constructed by random forest (RF), support vector machine (SVM), genetic algorithm optimized support vector machine (GA-SVM) and particle swarm optimization support vector machine (PSO-SVM) to determine the best estimation model. The results showed that the red band reflectance in the whole growth stage and reproductive growth stage was the most significant and stable, and the correlation coefficients were 0.835 and 0.754, respectively. The NBI in the vegetative growth stage was the most significant and stable, and the correlation coefficient was 0.846. The PSO-SVM was more suitable for the inversion of AGB at different growth stages of winter oilseed. The validation set R2 of the whole growth period, vegetative growth period and reproductive growth period were 0.866, 0.962 and 0.789, respectively.

    • Soybean Growth Parameters and Yield Estimation Based on UAV Multispectral Remote Sensing

      2023, 54(8):230-239. DOI: 10.6041/j.issn.1000-1298.2023.08.022

      Abstract (865) HTML (0) PDF 1.62 M (575) Comment (0) Favorites

      Abstract:In order to meet the requirements of modern agriculture for dynamic, continuous, and rapid monitoring of crop growth, soybean was used as the research object based on UAV multispectral remote sensing technology in northwest China, and five vegetation indices were selected with the best correlation to soybean leaf area index (LAI), above-ground biomass and yield, and support vector machine (SVM), random forest (RF) and back propagation neural network (BPNN) were used to construct models for estimating soybean LAI, above-ground biomass and yield, respectively. RF and BPNN were used to construct and validate the models for estimating soybean LAI, aboveground biomass and yield, respectively. The results showed that the accuracy of soybean LAI and aboveground biomass prediction models constructed based on the RF model was significantly higher than that of SVM and BP models, with R2 of 0.801, RMSE of 0.675m2/m2, and MRE of 18.684% for the validation set of LAI estimation model; R2 of 0.745, RMSE of 1548.140kg/hm2, and MRE of 18.770. In the estimation model construction of yield, the soybean yield prediction model constructed based on RF model in soybean flowering period (R4) had the highest accuracy with R2 of 0.818, RMSE of 287.539kg/hm2 and MRE of 7.128 in the validation set. The research results can provide a theoretical basis for the application of UAV multispectral remote sensing in crop monitoring and provide a rapid estimation of crop yield application reference.

    • Estimation of Potato Chlorophyll Content Based on UAV Multi-source Sensor

      2023, 54(8):240-248. DOI: 10.6041/j.issn.1000-1298.2023.08.023

      Abstract (803) HTML (0) PDF 1.22 M (520) Comment (0) Favorites

      Abstract:Chlorophyll is an important indicator for measuring crop photosynthesis, and monitoring leaf chlorophyll content (LCC) of potatoes during critical growth stages. UAV RGB and multispectral images were obtained during the potato tuber formation, tuber growth, and starch accumulation periods. Vegetation indices (VIs) were extracted from UAV multispectral images, and texture information (TIs) was extracted from RGB images by using Gabor filters. Then, the SVR-REF method was used for data dimensionality reduction to obtain the importance ranking of vegetation indices and texture features, and an iterative approach was used to add texture information to the best vegetation index model and observe the dynamic effect of each added texture information on the model. Finally, support vector machine (SVR) and K-nearest neighbor (KNN) algorithms were used for modeling. The results showed that the accuracy and stability of the two models were improved after adding texture features during the critical growth stages of potatoes, and the SVR model performed better than the KNN model. During the tuber formation period, the SVR modeling R2 was increased from 0.61 to 0.71, and RMSE was decreased from 0.20mg/g to 0.17mg/g, with an accuracy improvement of 14.2%. The validation R2 was increased from 0.58 to 0.66, and RMSE was decreased from 0.19mg/g to 0.17mg/g, with an accuracy improvement of 10.5%. During the tuber growth period, the SVR modeling R2 was increased from 0.59 to 0.67, and RMSE was decreased from 0.16mg/g to 0.14mg/g, with an accuracy improvement of 13.3%. The validation R2 was increased from 0.71 to 0.79, and RMSE was decreased from 0.15mg/g to 0.13mg/g, with an accuracy improvement of 13.3%. During the starch accumulation period, the SVR modeling R2 was increased from 0.62 to 0.69, and RMSE was decreased from 0.17mg/g to 0.14mg/g, with an accuracy improvement of 17.6%. The validation R2 was increased from 0.47 to 0.63, and RMSE was decreased from 0.17mg/g to 0.14mg/g, with an accuracy improvement of 17.6%. In addition, the number of vegetation indices involved in SVR modeling during the three periods were 19, 16, and 3, respectively, and the number of texture features were 4, 2, and 9, respectively. When vegetation indices were unable to respond adequately to chlorophyll content, more texture information was involved in modeling, and the model accuracy was improved significantly, further demonstrating the importance of texture features in chlorophyll content inversion in potatoes.

    • Real-time Navigation Method of Orchard Mobile Robot Based on Laser Radar Dual Source Information Fusion

      2023, 54(8):249-258. DOI: 10.6041/j.issn.1000-1298.2023.08.024

      Abstract (826) HTML (0) PDF 6.36 M (630) Comment (0) Favorites

      Abstract:In order to improve the accuracy and robustness of the navigation system of forest orchard mobile robot, a real-time navigation method was proposed based on high and low frequency dual source information fusion between orchard rows based on laser radar three-dimensional point cloud. Firstly, the spray robot carried a 3D laser radar to collect the point cloud information of the fruit trees on both sides, and the original point cloud data were preprocessed such as through filtering, down sampling, and statistical filtering, so as to retain the point cloud of the fruit tree canopy in the region of interest. Then the inter row navigation lines fitted by the Newton interpolation algorithm based on high-frequency update and the non-linear support vector machine (NSVM) algorithm based on low-frequency update were complementary fused. Finally, when the navigation line was switched, the stability of the merged navigation line was optimized, and a cubic B-spline algorithm was used to smooth the navigation line. The experimental results showed that the maximum curvature of the fusion optimized navigation line was 0.048m-1, and the average curvature was 0.018m-1. The fusion optimized navigation line was tracked at the speed of 0.5m/s and 1.0m/s, respectively, and the maximum absolute lateral deviation was 0.104m and 0.130m, and the average value was 0.053m and 0.049m, respectively, which showed that this navigation method can meet the requirements of autonomous navigation of operating equipment between rows in the orchard, which provided a technical reference for autonomous navigation of spray robots in the orchard environment.

    • Design and Experiment of Monocular SLAM Augmented Reality Tree Measurement System

      2023, 54(8):259-266. DOI: 10.6041/j.issn.1000-1298.2023.08.025

      Abstract (684) HTML (0) PDF 1.54 M (497) Comment (0) Favorites

      Abstract:A monocular SLAM forest test system was constructed, which used an ordinary smart phone embedded with an area array camera and an IMU as the hardware system, and used monocular SLAM technology to obtain depth maps, poses, etc. as data source. A method was designed based on smoothness and high robustness to filter the point cloud and tangent on the surface of the chest height cylinder; then based on the distance from the point to the surface of the cylinder and the distance from the tangent of the cylinder to the surface of the cylinder, an accurate estimation algorithm for the diameter at breast height and the standing tree position was constructed. Finally, based on the algorithm, an augmented reality tree measurement system was developed on the smart phone side, that was, real-time tree measurement by smartphones, and real-time manual supervision of the measurement results through augmented reality scenes. A highly robust method for filtering the point cloud and tangent on the surface of the breast height cylinder through smoothness was designed; then an accurate estimation algorithm for DBH and standing tree position was constructed based on the distance from the point and tangent to the surface of the cylinder. Finally, an augmented reality tree measurement system was developed on the smart phone end, which used the smartphone to measure trees in real time, and real-time manual supervision of the measurement results through the augmented reality scene. The tree measurement system was tested in five 32m×32m square plots to evaluate the usability of the tree measurement system at the same time; more importantly, each sample plot was investigated through single observation, orthogonal observation, symmetrical observation and surrounding observations in order to evaluate the impact of different observation methods on the accuracy of tree measurement. The results show that the deviation of the estimated standing tree position in the X and Y axes directions was -0.014~0.020m, and the root mean square error range was 0.04~0.08m; the deviation of the estimated DBH of standing tree was -0.85~-0.03cm (-3.60%~-0.04%), the root mean square error was 1.32~2.51cm (6.41%~12.33%). Compared with the single observation method, other observation methods can obtain higher accuracy estimation (especially for standing tree trunks that cannot be approximated as cylinders), orthogonal observation and symmetric observation were the best observation methods from the perspective of accuracy and efficiency. The results showed that the monocular SLAM augmented reality tree measurement system was a potential solution for accurate forest plot survey. 

    • Lightweight Plant Recognition Model Based on Improved YOLO v5s

      2023, 54(8):267-276. DOI: 10.6041/j.issn.1000-1298.2023.08.026

      Abstract (1416) HTML (0) PDF 18.63 M (828) Comment (0) Favorites

      Abstract:In ordered to facilitate the investigation of desert grassland plant species and their distribution in the whole Ningxia region, plant identification methods need to be studied. To address the problems of large number of parameters in YOLO v5s model, it is not easy to recognize plants in complex backgrounds, and a lightweight model of plant target recognition in complex backgrounds, YOLO v5s-CBD, was proposed. The improved model YOLO v5s-CBD introduced the BoTNet with Transformer module into the feature extraction network, to combine convolution and self-attention to improve the feeling field of the model. At the same time, coordinate attention was incorporated into the feature extraction network to effectively capture the relationship between channel and position and improve the feature extraction ability of the model. In terms of loss calculation, the SIoU function was introduced to calculate the regression loss to solve the problem of mismatch between the prediction box and the real box. Using depthwise separable convolution to reduce model volume. The experimental results showed that the model YOLO v5s-CBD infers a single image in only 8ms, a model volume of 8.9MB, a precision of 95.1%, a recall of 92.9%, a F1 value of 94.0%, and a mean average precision of 95.7% in a single Nvidia GTX A5000 GPU, and a mean average precision of 80.09% in the VOC dataset. Compared with YOLO v3-tiny, YOLO v4-tiny and YOLO v5s, the improved models reduced model volume and improved mean average precision. The model YOLO v5s-CBD had good robustness in both public dataset and Ningxia desert grassland plant dataset, faster inference speed and easy to deploy. It was applied in Ningxia desert grassland mobile plant image recognition APP and fixed ecological information observation platform, which can be used to investigate the species and distribution of desert grassland plants in the whole region of Ningxia, and long-term observation and tracking of Dashuikeng, Huangjichang, Mahuangshan and other places, Yanchi County, Ningxia.

    • Non-contact Predicting Method of Dairy Cow Weight Based on Cow-DETR and Deep Image

      2023, 54(8):277-285. DOI: 10.6041/j.issn.1000-1298.2023.08.027

      Abstract (991) HTML (0) PDF 3.21 M (504) Comment (0) Favorites

      Abstract:In order to solve the existence of some problems such as the low weighing efficiency of dairy cows in the current pasture, and being easy to cause the stress of dairy cows by manual participation, an end-to-end method of dairy cow weight estimation (Cow-DETR) based on improved detection transformer (DETR) network was proposed. The non-contact estimation on the dairy cow weight was carried out by using the depth image of dairy cow back. Firstly, a data acquisition device was designed and built, with which the cows back depth image and weight data were collected by using the Intel RealSense D435 depth camera and the weight scale. Then, deep image data was filled by using the edge flat filter and hole filling filter to reduce the impact of deep data loss on weight estimation. Finally, by adding the weight prediction unit with an alternate fully connection layer (AFC) to the prediction module of DETR to establish a cow weight estimation model. AFC was added to improve the ability of dairy cow weight-related feature extracting. It implemented the end-to-end dairy cow back positioning while performing a non-contact estimation of dairy cow weight by Cow-DETR model. The data of 139 cows were used to evaluate the model, and the results through 5-fold cross validation showed that the weight estimation method proposed can achieve a high accuracy in dairy cow weight estimation. The average absolute error of weight estimation was below 17.21kg, the average relative error was less than 3.71%. The average recognition time was 0.026s per image. Compared with the existing weight estimation methods, the results showed that Cow-DETR got lower average absolute error and average relative error than the other six methods in more dairy cow data. In the meantime, the method proposed had less requirements on the posture of dairy cow, which can more comply with the actual production demand of ranch and provide a solution for the weight estimation of dairy cow.

    • Automatic Measurement Method of Goat Body Size Based on Double Vision Angle Camera Image

      2023, 54(8):286-295. DOI: 10.6041/j.issn.1000-1298.2023.08.028

      Abstract (810) HTML (0) PDF 5.40 M (480) Comment (0) Favorites

      Abstract:The body size of farm animal is an important criterion for selection and appraising of variety resources, and body size is also employed to estimate animal body weight in many existing studies. In order to meet the requirement of measuring goat body size in a non-contact manner, a double view goat body images acquisition system was designed and the corresponding algorithm for goat body size calculating was developed. The double view images acquisition system was set up by using PLC controller, photoelectric sensors, limit switches, reducer motors, and industrial cameras. Goat's top view binary image was obtained by using background subtraction. The simple linear iterative clustering algorithm (SLIC) was introduced to construct the texture and color feature vectors of the superpixel of the side view goat body image. Each superpixel of a side view image was classified as foreground and background part by using a support vector machine (SVM) based classifier. The confidence and the region adjacent graph (RAG) of each superpixel were comprehensively used to binarize the side view goat body image. A set of methods for the body size feature points locating in the side and top view binary images of goat body was proposed. These feature points were further employed to calculate the goat body size parameters such as body height, body slant length, chest depth, chest width, and pipe diameter. Then, chest girth was fitted by using chest depth and chest width, circumference of cannon bone was fitted by using pipe diameter. The developed method was tested by using the double view images of Haimen goat collected in a breeding farm. The test results indicated that SLIC, SVM and RAG can segment the goat side view foreground with an accuracy of 94%. The intersection of union (IoU) of the side and top view foreground obtained by the algorithm and the manually labeled one were respectively 96.1% and 97.5%. The goat body size parameters calculated by using the developed algorithm were compared with those measured manually. The comparison results indicated that the average errors of the circumference of cannon bone, body height, chest depth, chest width, chest girth and body slant length were 5.5%,3.7%,2.6%, 5.2%,4.1% and 3.9%, respectively. Therefore, the image acquisition device developed can obtain the goat body double view images efficiently, and the proposed methods for goat image foreground segmentation and the feature points locating. Comprehensive utilization of the image acquisition device and the corresponding image processing algorithm developed provided a solution to the problem of measuring goat body size in an automatic manner.

    • Classification Method of Heartbeat Confusion Signals of Hatching Eggs Based on TCN and Transformer

      2023, 54(8):296-308. DOI: 10.6041/j.issn.1000-1298.2023.08.029

      Abstract (684) HTML (0) PDF 5.39 M (465) Comment (0) Favorites

      Abstract:The egg embryo culture method is commonly used for the preparation of avian influenza vaccines. The rapid and accurate classification of hatching eggs into active and early removal of dead embryos from live embryos can effectively avoid bacterial or mycobacterial contamination due to embryo death and it is of great importance for the improvement of hatching efficiency. Currently, the heartbeat signal of chicken embryos is mainly used as the basis for distinguishing dead embryos from live embryos. However, after 96 h of avian influenza virus injection, the heartbeat signal of live egg embryos is between that of ordinary live embryos and dead embryos, which is easily confused with dead embryos. This type of data is called chicken embryo heartbeat confusion signal, and is added to the data set as a separate category. The original dual classification of dead embryos and live embryos was changed to a triple classification of dead embryos, ordinary live embryos and 96 hour live embryos. An absolute average value normalization preprocessing method was proposed based on confusing heartbeat signals of hatching eggs, to enhance the original data features and improve the classifiability of the data. A shallow dual branch network structure residual fully temporal convolutional with transformer network (RFTNet) with residual structure was proposed based on temporal convolutional network (TCN) and transformer for global features and detail features. The experimental results showed that the three-classification absolute average value normalization preprocessing method and RFTNet two-branch network proposed demonstrated good performance in the classification task of hatching eggs confusion dataset with a detection accuracy of 99.75%. In addition, the three evaluation indexes of detection accuracy, recall rate and F1 score reached 99.75%, 99.74% and 99.7%, respectively, further verifying the effectiveness of the method.

    • >农业水土工程
    • Marginal Effects of Photosynthetic Characteristics and Yield in Maize and Soybean Intercropping Systems

      2023, 54(8):309-319. DOI: 10.6041/j.issn.1000-1298.2023.08.030

      Abstract (701) HTML (0) PDF 1018.36 K (500) Comment (0) Favorites

      Abstract:In order to clarify the marginal effect of intercropping patterns and the localized maize and soybean intercropping technical patterns in Hetao Irrigation Area of Inner Mongolia, four intercropping technical patterns (row ratio: 2∶3, 2∶4, 4∶3, 4∶4(T2∶3, T2∶4, T4∶3, T4∶4)) were set under the condition of trickle irrigation. The changes of photosynthetic characteristics, interspecific competitiveness and marginal effect were analyzed with maize and soybean as control. The results showed that the overall chlorophyll SPAD and nitrogen content of maize leaves in monocropping and intercropping reached peak at the large trumpet stage, and then decreased gradually, and then appeared a small peak at the filling stage. At this time, the chlorophyll SPAD and nitrogen contents in the T2〖DK〗∶3 mode were not significantly different from those in mono-cropping stage, and the chlorophyll SPAD and nitrogen contents in the large trumpet stage were decreased by 0.91% and 5.07% compared with that in mono-cropping stage, respectively. Compared with monocropping, the net photosynthetic rate was increased by 5.09% and 5.17%, respectively, and reached the peak at the spinneret stage, but T2∶3 decreased slowly compared with monocropping. Other modes were characterized by low peak, early appearance (large trumpet stage), and rapid decline. The contents of chlorophyll SPAD and nitrogen in the leaves of T2∶3 mode and monocropping soybean reached a peak at the flowering stage, and then decreased gradually, and a small peak appeared at the drum grain stage. At pod stage and drum grain stage, the SPAD value and nitrogen content of T2∶3 mode were increased by 2.32% and 5.11%, respectively, compared with that of monocropping. The peak value of net photosynthetic rate appeared late (bulging stage), while the peak value of other models appeared early and decreased rapidly, especially in the middle line of models T2∶4, T4∶3 and T4∶4. Therefore, the long post-anthesis photosynthetic stability period of intercropping populationwas the key, which was an important reason to exert the advantage of intercropping. Only T2∶3 model land equivalent ratio was greater than 1, reaching 1.38, and the relative crowding coefficient of soybean was greater than that of maize, and the encroachment power and competition ratio of intercropping soybean were greater than that of maize. T2∶3 had obvious intercropping advantage and competitiveness, and the relative yield growth of soybean was greater than that of maize, so it was a competitive dominant species. The maize and soybean yields of T2∶3 mode were the highest, which were 9705kg/hm2 and 2265kg/hm2,respectively, accounting for 81.08% and 18.92% of the system yield. Maize yield, chlorophyll SPAD and net photosynthetic rate in T4∶4 mode had significant marginal advantage, while soybean only showed marginal advantage in photosynthetic rate, and middle-line soybean in T2∶3 mode had photosynthetic advantage. In conclusion, T2∶3 model was the appropriate intercropping technology model in Hetao Irrigation Area of Inner Mongolia.

    • Regulation of Border Irrigation Technical Elements Considering Condition of Uneven Initial Soil Moisture Content along Border

      2023, 54(8):320-329,370. DOI: 10.6041/j.issn.1000-1298.2023.08.031

      Abstract (757) HTML (0) PDF 3.22 M (496) Comment (0) Favorites

      Abstract:Soil initial moisture content is one of the important factors affecting border irrigation quality. The uneven distribution of soil moisture content caused by runoff is a common phenomenon in the farmland of North China Plain. In order to explore the influence of spatial variability of initial soil moisture content on flow movement and irrigation quality of border irrigation, one-dimensional soil column infiltration test and two-dimensional soil tank irrigation test were carried out in this study. Combined with WinSRFR surface irrigation simulation model, the technical factors of border irrigation under the condition of uneven initial moisture content were optimized and solved. The results showed that the greater the increase of initial soil moisture content along the border, the faster the surface water flow of border irrigation, and the slower the surface water flow of border irrigation. Compared with the uniform distribution of initial moisture content, under the condition of uneven distribution of initial moisture content along the border soil, the irrigation efficiency and irrigation uniformity will decrease, and the water storage efficiency will not change significantly. When the initial soil moisture content increased along the border, the irrigation efficiency and water storage efficiency were affected by the length of the border, the flow rate per unit width of the border and the number of water improvement, while the soil moisture uniformity after irrigation was only affected by the length of the border and the flow rate per unit width. When the initial moisture content of the border soil increases uniformly from 0.1890m3/3 to 0.4643m3/m3, the optimal border irrigation quality can be obtained when the border length L=85m, the number of water change G=6.0, and the unit width flow q=7.0L/(m·s). The results of this study can provide a scientific basis for the regulation of irrigation technology elements under the initial moisture content of border soil caused by rainfall runoff.

    • Effect of Water and Nitrogen Coupling on Carbon Source and Sink of Paddy Ecosystem in Black Soil Area

      2023, 54(8):330-338. DOI: 10.6041/j.issn.1000-1298.2023.08.032

      Abstract (677) HTML (0) PDF 1.10 M (495) Comment (0) Favorites

      Abstract:A field experiment was conducted to explore the effects of different water and nitrogen coupling methods on the carbon balance of paddy ecosystem in 2022. Two irrigation modes (conventional flooding irrigation (F) and rice-controlled irrigation (C)) and three nitrogen application levels (conventional nitrogen application-level (N, 110kg/hm2), 10% nitrogen reduction-level (N1, 99kg/hm2) and 20% nitrogen reduction-level (N2, 88kg/hm2)) were set up in the experiment. The effects of different water and nitrogen coupling on dry matter weight, carbon content, soil respiration CO2 emission flux, CH4 emission flux, and total emissions of both were analyzed. The net ecosystem carbon budget (NECB) evaluation system was used to analyze the carbon source and sink effect of ecosystem in black soil paddy fields. The results showed that under different water and nitrogen coupling modes, the carbon sequestration of rice panicles and roots accounted for 26.61%~40.92% and 24.63%~31.95% of the total carbon sequestration, respectively. Under the same nitrogen application rate, C can improve the carbon content and dry matter weight of rice organs compared with F. During the whole growth period of rice, the CH4emission flux of each treatment showed a trend of increasing first, then decreasing before increasing, and peaked at tillering stage and jointing-booting stage. The soil respiration CO2 emission flux of each treatment showed a single peak variation, and the peak appeared at the tillering stage. Under the same irrigation mode, except for the regreening period, the CH4 emission flux and soil respiration CO2 emission flux of each treatment was decreased with the decrease of nitrogen application rate. Under the same nitrogen application rate, compared with rice control irrigation, F reduced soil respiration CO2 emission flux and total emission, but increased CH4 emission flux and total emission. Under different water and nitrogen coupling modes, the net primary productivity of rice was 4245.82~6958.19kg/m2, the net primary productivity of panicle was the highest, and the net primary productivity of litter was the lowest, accounting for 42.88%~51.82% and 3.19%~3.90% in the net primary productivity of rice, respectively. Under the same nitrogen application rate, the net primary productivity of rice in each treatment of C mode was higher than that of conventional irrigation mode. Compared with FN, FN1 and FN2 treatments, the net primary productivity of CN, CN1 and CN2 treatments was increased by 11.17%, 31.92% and 2.98%, respectively. In addition, the NECB of different water and nitrogen coupling modes was positive, which indicated that the paddy ecosystem in the black soil area was a net carbon “sink”. The net carbon budget of CN1 treatment (1082.87kg/hm2) was significantly higher than that of other treatments (P<0.05), which indicated that the carbon “sink” intensity of paddy ecosystem with 10% nitrogen reduction under controlled irrigation mode was the largest.

    • >农业生物环境与能源工程
    • Solar Greenhouse Temperature Prediction Model Based on 1D CNN-GRU

      2023, 54(8):339-346. DOI: 10.6041/j.issn.1000-1298.2023.08.033

      Abstract (698) HTML (0) PDF 1.31 M (502) Comment (0) Favorites

      Abstract:Accurate prediction of heliostat temperature was the key to achieve efficient greenhouse regulation, which was of great importance to crop growth and development, but it was difficult to achieve continuous and accurate prediction due to the characteristics of time series, nonlinearity and multi coupling of temperature. At the same time, the current production regulation of greenhouse mostly depended on the relevant experience of producers. This method had caused the lag of feedback control and affected the growth of crops.A temperature prediction model of solar greenhouse based on 1D CNN-GRU was proposed. The internal and external environmental factors were obtained through the monitoring platform inside and outside the greenhouse, and the strong correlation features and structural features were obtained by Spearman correlation coefficient and the two-dimensional matrix input network with time step, which was used for temperature prediction. The determination coefficient of the model after 1~4h prediction on the test set was 0.970~0.994, the root mean square error was 0.612~1.358℃, the average error was 0.428~0.854℃,and the maximum absolute error after the absolute value was 0.856~1.959℃. The model was verified under different KT and the results showed that the model had the best prediction effect when KT≥0.5(sunny), and the model also achieved ideal prediction accuracy under other KT, indicating that the model was universal and provided an important basis for accurate and efficient temperature control of solar greenhouse.

    • Positioning Method of Greenhouse Plant Protection Robot Based on Distance Measurement Value Correction

      2023, 54(8):347-358. DOI: 10.6041/j.issn.1000-1298.2023.08.034

      Abstract (699) HTML (0) PDF 3.49 M (525) Comment (0) Favorites

      Abstract:A fusion positioning method was proposed based on the correction of UWB distance values to address the problem of low positioning accuracy and poor stability of UWB systems caused by frequent non-visual communication between UWB nodes during the operation of greenhouse plant protection robots. Firstly, a method to identify the communication type between UWB nodes was designed based on the distance residuals; secondly, it analyzed the causes of UWB distance errors under line-of-sight and non-line-of-sight communication and established a distance correction model under the two communication conditions; finally, it designed a method to fuse UWB distance correction values and IMU data based on the extended Kalman filter, and achieved reliable positioning during the operation of greenhouse robots. Finally, the UWB distance correction and IMU data fusion method were designed based on the extended Kalman filter, which finally realized the reliable positioning during the operation of greenhouse robot. The actual validation results showed that the positioning error of the fusion method with UWB range correction was 11.95cm under the non-line-of-sight communication conditions, which was 83.11% lower than that of the fusion method without UWB range correction, and it can provide stable and high-precision positioning information for the greenhouse plant protection robot.

    • Fertilizer Efficiency and Heavy Metal Risk Analysis of Continuous Application of Biogas Fertilizer in Vegetable Cultivation

      2023, 54(8):359-370. DOI: 10.6041/j.issn.1000-1298.2023.08.035

      Abstract (602) HTML (0) PDF 4.88 M (483) Comment (0) Favorites

      Abstract:In order to explore the fertilizer effect of biogas fertilizer (BF) in vegetable planting, three rounds of Shanghai cabbage-eggplant rotation planting experiments were carried out in the greenhouse, and the application rates of low (BF-L), medium (BF-M) and high (BF-H) biogas fertilizer were set up. The effect of BF replacing chemical fertilizer (CF) and the threshold value of highload land consumption of BF were discussed from the perspectives of yield, soil characteristics and heavy metal risk. The results showed that the yield of BF groups was 6% lower than that of CF group in Shanghai cabbage planting, and the average yield of BF-M group was the highest in BF groups (39.7t/hm2). In eggplant planting, the yield of BF groups was higher than that of CF group, and the average yield of BF-H group was the highest, reaching 58.3t/hm2, which was 27% higher than that of CF group. After two years of continuous application of BF, the total nitrogen (TN) and total phosphorus (TP) contents of soil were increased significantly, and the increase was much higher than that of CF group. The TN content of soil in BF-M and BF-H groups was increased by 84% and 85% compared with that of the original soil, and the TP content of soil was increased by 3.4 times and 3.2 times. However, the effect of BF application on soil total potassium (TK) content was not obvious, which was only about 17% higher than that of the original soil. In addition, the soil pH value of continuous application of BF was more stable, which can effectively alleviate the problem of soil acidification caused by nitrogen fertilizer application. However, like CF, BF application had a greater impact on soil electric conductivity (EC). The soil EC value of BF-M and BF-H groups showed an increasing trend year by year, with an increase of more than 70% compared with that of the original soil. Furthermore, there was no risk of excessive heavy metals and heavy metal intake in the three seasons of vegetables harvested, and there was no phenomenon that the heavy metal content of vegetables increased year by year. Moreover, the continuous application of BF only caused the accumulation of Cu and Zn in soil, but it was still within the standard limit, and had no significant effect on the content of Pb, Cr, Cd, As and Hg in soil, and there was no heavy metal pollution caused by BF application. The research result can provide a reference for the evaluation of fertilizer efficiency and safety of continuous rounds of high-load BF application in facility vegetable cultivation.

    • >农产品加工工程
    • Impact Breakage Characteristics and Discrete Element Simulation of Extruded Pellet Feed

      2023, 54(8):371-380. DOI: 10.6041/j.issn.1000-1298.2023.08.036

      Abstract (797) HTML (0) PDF 4.80 M (558) Comment (0) Favorites

      Abstract:With the aim to explore the influence of collision on extruded pellet feed during air delivery, perch extruded pellet feed was taken as the research object to simulate the collision and breakage of extruded pellet feed through experiments and simulations, exploring the breakage mechanism and law. The horizontal collision test platform was used to explore the influence of different collision speeds on the breakage of extruded pellet feed, and the breakage function was used to establish the fitting relationship between breakage size and collision speed. The determination coefficient of parameters fitting was greater than 0.99. The breakage state of extruded pellet feed was divided into four states, unbroken, partially broken, broken, and disintegrated. The critical collision velocity was 25.60m/s, and the corresponding airflow velocity was 56.29m/s. The discrete element model of extruded pellet feed was established by discrete element method (DEM) and the parameters were calibrated. Based on EDEM software the critical breakage speed of 25.20m/s was obtained by simulating the collision breakage process, and the difference between the critical speed obtained by experiment and simulation was 1.6%. In the EDEM post-processing, the relationships between the collision speed and the breakage rate and the maximum size ratio were obtained. As the speed increased, the breakage rate was also increased. However, the maximum size ratio was decreased. The relationship between the breakage rate and the energy loss was also obtained. The figure of breakage rate showed linear change first, and then exponential change. But the maximum size rate was the exponential change. And in the intersection of the two lines at about 25.20m/s cliff-like declined. When the collision speed was less than 25.20m/s, the breakage rate was linearly related to the loss energy. After reaching the critical breakage speed, the loss energy was changed exponentially. The results provided data support and theoretical reference for explaining the breakage mechanism of extruded pellet feed.

    • >车辆与动力工程
    • Dynamic Change Direction of Tractor Based on Oil Filling Flow and Aeration Degree

      2023, 54(8):381-393. DOI: 10.6041/j.issn.1000-1298.2023.08.037

      Abstract (800) HTML (0) PDF 2.60 M (483) Comment (0) Favorites

      Abstract:The effects of different oil flow rates and aeration degree on the performance of power reversing were studied. The oil flow rate of tractor power reversing clutch is easily affected by temperature, return spring stiffness and preload force, and the air content of hydraulic oil is easily polluted during filling and working. The reversing performance was evaluated by using reversing time, impact, slip work and wear to improve the quality of the tractors power reversing, working efficiency and service life of the drive train. Taking the TX4A drive train of Dongfanghong LF2204 tractor as the research object, the mathematical model of the dynamic reversing process considering the oil filling flow and aeration degree was established. The mechanical model, control model and hydraulic model of the reversing clutch were established based on ADAMS, Matlab/Simulink and AMESim. Simulation analysis and bench test were carried out under the condition that the forward gear changed to the backward gear when the tractor was working in I gear. The simulation results showed that when the hydraulic oil aeration degree was 0.1% and the oil filling flow rate was 16L/min, and 14L/min, compared with the flow rate of 20L/min, the commutation time was increased by 20% and 43%, the transmission minimum output torque was decreased by 26% and 52%, the slip work was increased by 33% and 78%, the maximum impact degree was decreased by 11% and 18%, maximum wear was increased by 24% and 44%, respectively. When the oil flow rate was 20L/min and the aeration degree was 1% and 5%, compared with the aeration degree of 0.1%, the commutation time was increased by 26% and 85%, the minimum output torque of the transmission was decreased by 0.4% and 0.8%, the slip work was increased by 38% and 163%, the maximum impact degree was decreased by 57% and 50%, and maximum wear was increased by 47% and 163%, respectively. The bench test results showed that the variation trend of the test data was basically consistent with that of the simulation test data, and the error was within 5%. The maximum error occurred when the oil filling flow rate was 20L/min and the aeration degree was 5%. The main reason was that the oil pulsation itself had impact on the sensor, and the proportional valve was affected by oil bubbles, which reduced the output accuracy.

    • Design and Test of Agricultural Vehicle Traction Load Vehicle Based on Electric Drive System

      2023, 54(8):394-401,410. DOI: 10.6041/j.issn.1000-1298.2023.08.038

      Abstract (839) HTML (0) PDF 3.68 M (533) Comment (0) Favorites

      Abstract:In response to the problems of complex mechanical structures and dead zones in loading, as well as a single-function collection system that cannot evaluate traction performance in real-time for traditional agricultural vehicles, an electric-driven agricultural vehicle traction load vehicle was developed. Combining the targeted design of a maximum loading traction force of 150kN with a force analysis of the driving wheel, key components of the load vehicle were selected and designed. An integrated engine-electric bridge electric drive system was used as the core unit, and a steering traction frame was innovatively used to achieve automatic steering of the front platform. Based on the LabVIEW RIO architecture, a high-performance measurement and control system was built using FPGA, enabling the collection, wireless transmission, and storage of multiple information, such as electric current, voltage, traction force, and fuel consumption. The fuzzy adaptive PID control algorithm was used for closed-loop control of traction force loading. Finally, the load vehicle was subjected to performance verification testing, achieving a range of 0~150kN load loading, with maximum response time of 3.6s, maximum overshoot of 1.61%, and maximum error of 4.5% between actual and targeted traction forces. The test results showed that the load vehicle had good traction load performance and the measurement and control system can accurately monitor multiple parameters of traction performance in real-time, providing comprehensive evaluation of agricultural vehicle traction performance.

    • >机械设计制造及其自动化
    • Type Synthesis of Weakly-coupled Three-rotational Parallel Mechanisms Based on Inverse Jacobian Matrix

      2023, 54(8):402-410. DOI: 10.6041/j.issn.1000-1298.2023.08.039

      Abstract (687) HTML (0) PDF 885.52 K (454) Comment (0) Favorites

      Abstract:To obtain the three-rotational parallel mechanism with large bearing capacity and easy control, the connection between the motion coupling of the parallel mechanism and the spatial geometric conditions of the transmission wrench screws was established by analyzing the meaning of the singular vectors in the inverse Jacobian matrix, and then a configuration synthesis method for the weakly-coupled three-rotational parallel mechanisms was proposed. Firstly, according to the motion coupling requirements of the parallel mechanism in different directions,the inverse Jacobian matrix was constructed, and the spatial geometric conditions of all transmission wrench screws were derived based on the inverse Jacobian matrix. Secondly, according to the relationship between the transmission wrench screws and the twist screws of the passive joints and the relationship between the constraint screws and twist screws of the active and passive joints, the types and arrangement conditions of the joints in each branch chain were obtained. On this basis, many branch chains whose active joints were mounted on the fixed platform were synthesized. Furthermore, the principles of selection and combination of branch chains were formulated, and based on the above principles, the configuration synthesis of the weakly-coupled three-rotational parallel mechanism was completed. Finally, the correctness of the proposed method was verified by the analysis of the motion coupling of three examples.

    • Design and Characteristics Study of Variable-stiffness Joint Based on Principle of Magnetic Flux Superposition

      2023, 54(8):411-417. DOI: 10.6041/j.issn.1000-1298.2023.08.040

      Abstract (518) HTML (0) PDF 1.39 M (451) Comment (0) Favorites

      Abstract:The variable permanent magnet spring joint made up of the permanent magnet spring has good nonlinear stiffness change performance, which can improve the safety of human and robot interaction. To further improve the range of motion and stiffness performance of the robot, based on the principle of magnetic flux superposition, a type of robot variablestiffness joint was proposed, which increased the adjustment speed of the joint stiffness and motion range of the joint, while reducing the joint mass. The variable stiffness working principle of adjustment of magnetic flux in permanent magnet-electromagnetic hybrid variable stiffness device by electrical signal was elaborated, and the overall mechanism of the joint was designed based on this principle. The joint stiffness model was established according to the magnetic flux continuity principle and the virtual displacement method. And the relationship between the joint stiffness with the current and the joint position was given. Based on the variable-stiffness joint stiffness model, the position and stiffness coordination controller of the variable-stiffness joint was designed, and the principle prototype of the variable-stiffness joint was built. The proposed variable stiffness robot joint based on the magnetic flux superposition principle had lighter weight and better structural stiffness change performance and motion accuracy. The overall joint mass was 1.1kg and the joint can rotate from -180° to 180°. The experimental test results showed that the variable stiffness robot joint based on the superposition principle of magnetic flux can realize rapid adjustment of joint stiffness, and the adjustment time was only 0.133s. The position and trajectory tracking accuracy of the joint was increased with the increase of stiffness and decreased with the increase of frequency.

    • Influence of Slope-diverge-shaped Throttling Grooves on Micro-motion Characteristics of Proportional Valve

      2023, 54(8):418-426. DOI: 10.6041/j.issn.1000-1298.2023.08.041

      Abstract (770) HTML (0) PDF 3.25 M (491) Comment (0) Favorites

      Abstract:For the existing proportional valve with the U-shaped throttling grooves of the main spool, the discharge area change gradient of the valve port is more severe and the flow gain is large in the small opening, resulting in poor micro-motion characteristics such as unstable start, slower response and low flow control accuracy of the proportional valve in the small opening. A throttling grooves with slope-diverge-shaped was proposed. The discharge area change gradient of U-shaped throttling grooves and slope-diverge-shaped throttling grooves were compared and analyzed by theoretical calculation and simulation methods, as well as the displacement characteristics, flow characteristics and valve port flow characteristics under different valve port openings. It can be seen from the simulation results that compared with the U-shaped throttling grooves, the response time of the slope-diverge-shaped throttling grooves was shortened by 0.04s when the opening of the valve port was 1mm. When the opening of the valve port was 2mm, the displacement response time was shortened by 0.07s. And when the slope-diverge-shaped throttling grooves valve was ported at the small opening, its steady-state hydraulic power was smaller, the flow state was more stable, and the flow loss was smaller. And the experimental results showed that the displacement response time of the spool of the slope-diverge-shaped throttling grooves was shortened by 0.08s, and the linearity of the flow response characteristic curve was better. Finally, through the comparative analysis of the simulation and experimental results, it can be seen that slope-diverge-shaped throttling grooves, the discharge area change gradient of the main valve core was smoothly in the small opening, and the flow gain was relatively stable, which improved the smoothness of valve start-up, speed of response and flow control accuracy. In summary, the slope-diverge-shaped throttling grooves realized the improvement of the micro-motion characteristics of the proportional valve.

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