LIU Xuemei , LIU Xinghua , CUI Huiyuan , YUAN Jin
2021, 52(11):1-20. DOI: 10.6041/j.issn.1000-1298.2021.11.001
Abstract:The goal of precise application is to achieve full coverage and uniform deposition of droplets in the canopy. However, the characteristics of crop canopy morphology, canopy closure and mechanical parameters of branches and leaves are different. It is necessary to integrate target characteristic parameters, equipment application ability, spraying environment and operating conditions to achieve the minimum dosage and optimal fogging, which can increase the utilization rate of the chemical solution, ensure the prevention and control effect, and reduce environmental pollution. The droplet deposition mechanism, detection and analysis are the decision-making basis for the optimization and control of precise application parameters, which have become a research hotspot in the development of digital and intelligent crop protection. Firstly, the droplets deposition process in canopy and its influencing factors by different application methods was analyzed. Secondly, the various research perspectives, methods and levels of droplet deposition were introduced from four directions: empirical research on deposition performance, analysis and modeling of deposition mechanism, detection and evaluation of droplet deposition, and operating parameters optimization of pesticide application. The common key issues in recent study of the interaction of droplets, branches and leaves, and airflow in canopy droplet deposition were analyzed, and the open problems in this field research were proposed. Finally, the challenges and opportunities faced by the crop canopy droplet deposition research in precision application were summarized. And it was suggested to integrate multi-source sensing technology, big data analysis and deep learning and other artificial intelligence technologies to build a digital twin of crop canopy droplet transport and deposition, so as to realize the digital description and analysis of canopy droplet transport and deposition process.
BAI Xiaoping , MENG Peng , WANG Zhuo , SHI Jia
2021, 52(11):21-27. DOI: 10.6041/j.issn.1000-1298.2021.11.002
Abstract:The accuracy of the kinematics model of agricultural machinery affects the accuracy and stability of navigation control. In order to improve the accuracy of the path tracking controller of agricultural machinery, a design method of navigation controller based on the motion characteristics of agricultural machinery was proposed. The method was mainly an improvement of the traditional two-wheeled vehicle kinematics modeling method. Aiming at the shortcomings of the small-angle approximation replacement (the direction angle was equal to yaw angle) of the traditional two-wheeled vehicle model, the method of adding the slip angle was used to optimize the kinematics modeling process of agricultural machinery. The same control method (state feedback control) and different kinematics models were used to design controllers for control experiments. When tracking a straight path, the slip angle had little effect on the model accuracy, and the introduction of slip angle can affect the tracking accuracy of agricultural machinery to a certain extent. When tracking a curved path, the slip angle had a great impact on the change of the direction angle, which can greatly affect the path tracking accuracy. Using a tractor equipped with automatic navigation equipment as an experimental platform for field experiments. The experimental results showed that the maximum lateral error of straight driving was 0.0454m, the absolute average error was 0.0149m and the standard deviation was 0.0119m. The maximum lateral error of curve driving was 0.1613m, the absolute average error was 0.0688m and the standard deviation was 0.0434m. The data showed that the path tracking controller designed based on the proposed kinematics model optimization method can improve the linear path tracking to a certain extent, and can greatly improve the curve tracking accuracy.
WANG Jinfeng , ZHANG Xin , TANG Han , WANG Jinwu , WENG Wuxiong , YANG Dongze
2021, 52(11):28-39. DOI: 10.6041/j.issn.1000-1298.2021.11.003
Abstract:Aiming at the problems of high power consumption and straw entanglement of rice straw returning to the field, combined with the operation process of the straw returning machine, the reasons of high power consumption and straw entanglement of the straw returning blade before optimization were analyzed, and a kind of reverse rotating deep-buried sliding cutting returning blade was designed. The Archimedes spiral was used to design the side cutting edge of the straw returning blade to improve the sliding cutting performance of the straw returning blade and the dynamic sliding cutting angle of the side cutting edge curve was calculated and verified to meet the condition that the soil and straw slipped out of the straw returning blade. The arc curve was used to design the tangent section of the straw returning blade and the radius of circular arc was determined to be 60mm on the basis of ploughing width and installation angle of tangent section. The EDEM simulation software was used to simulate and compare the straw returning blade with the straw returning blade before optimization. The results showed that the straw returning rate and throwing performance of the reverse rotating sliding cutting returning cutter were basically the same as those of the optimized previous straw returning blade, and the working power consumption was reduced by 18.19%. The stubble height, cutter roll speed and machine forward speed were selected as three factors, and the working power consumption was selected as the evaluation index to carry out the orthogonal test design. Finally, the factors affecting the working power consumption of the straw returning blade from big to small were determined as follows: cutter roll speed, machine forward speed and stubble height. The field test results showed that when the field soil moisture content was 20%~30%, the surface straw coverage rate was 336~353g/m2, the tractor operating speed was 1.5km/h, and the blade roller rotating speed was 250r/min, the operation effect of straw deep-buried sliding cutting returning blade was that the average tillage depth was about 18cm, the returning rate was 87.9%~89.7%, and the surface flatness was 2.1~3.7cm. All the operation indexes met the agronomic requirements of straw returning, and the rationality of simulation test was verified.
LIU Hai , ZHANG Qingsong , LIAO Yitao , WEI Guoliang , DU Zheng , LIAO Qingxi
2021, 52(11):40-48,77. DOI: 10.6041/j.issn.1000-1298.2021.11.004
Abstract:In order to solve the problem of uneven seedbed surface caused by the fluctuation of soil moisture content during Brassica chinensis direct seeding in the Mid-lower Yangtze River, a combined soil preparation of plowing, rotary tillage, ridging and compaction was proposed to adapt to the growth of Brassica chinensis. By combining the cultivation technology of Brassica chinensis seedbed and field tillage operation requirements, a plow-rotary and roll-forming revetment style seed bed ridging device of combined precision seeder for Brassica chinensis was designed. According to the principle of soil compaction and ridge surface forming, the dynamics of seedbed roll forming was analyzed to determine the main structure and working parameters of the ridging roll. The results showed that the qualified rate of ridge height, ridge top width and ridge spacing were 90.00%, 93.33% and 96.67%, respectively, when the operating speed of the machine was 2.0~5.0km/h. And the stability coefficient of soil firmness at the tops and sides of the double ridges were no less than 92.36% and 92.53%. The maximum difference in surface roughness of the ridge top surface was 2.19mm. The variation coefficient single row seedling number and variation coefficient of each row seeding number were both less than 10% when the device was used to achieve precision sowing of Brassica chinensis. The operating effects met the agronomic requirements of Brassica chinensis direct seeding and provided reference for Brassica chinensis sowing mechanization on ridge.
WANG Yecheng , GAO Yunpeng , TAI Wenshuo , WANG Yu , Lü Jinqing , YANG Deqiu
2021, 52(11):49-58. DOI: 10.6041/j.issn.1000-1298.2021.11.005
Abstract:A pickup finger potato precision seed metering device was designed, because of that the traditional cup-belt potato seed metering device had some shortcoming on the seed clamping and seed transport process, and based on the opening, closing, swinging of splint in each process to control the position and movement of seed to achieve five processes of seed filling, seed clamping, seed clearing, seed transport and seed dropping, meeting the requirement of precision planting technology. The structural parameters of key components such as clamping fixture and slideway were designed and the change rule of limiting speed of seed filling and limiting position of seed cleaning was gotten by illustrating and analyzing the overall structure and working principle of each working process of the seed metering device. In order to prove the performance of pickup finger potato seed metering device, the experiment was employed through the method of quadratic orthogonal rotating center combination of three factors and five levels according to national standard (GB/T 6973—2005). In test, potato seed Dongnong 311 was selected as experimental material. Combining with extensive pre-experiment and theoretical analysis, the working speed, seed clearing shifting, length of splint were taken as the main influencing factors, and seed qualified index, multiple index, missing index were taken as the response index, the experimental research was carried out. The optimal combination of parameters were working speed of 6.0km/h, seed clearing shifting of 9.5mm, length of splint of 72mm, and under the optimal combinations, the qualified index was 90.3%, the multiple index was 6.1%, and the missing index was 3.6%, the verification test was repeated five times, the results indicated that the actual test results were in agreement with the optimization results.
WANG Jiayi , ZHAO Shuhong , GAO Lianlong , YUAN Yiwen , YANG Yueqian
2021, 52(11):59-67. DOI: 10.6041/j.issn.1000-1298.2021.11.006
Abstract:A kind of stubble cutter was designed for cutting stubble and soil by ploughing machinery and no-tillage planter, which had the disadvantages of high resistance, high oil consumption and the impact of soil block on the cutting tool during the operation of stubble cutter. The self-regulating stubble cutter was provided with a buffer mechanism, which could adjust the cutting edge angle according to different depths of the stubble and soil characteristics to achieve low resistance and deep feed cutting. By measuring the penetration resistance of multi-point soil (soil and root soil) and the friction angle of soil and stubble, and combining with theoretical analysis and computer aided design, it was determined that the stiffness coefficient of spring of buffer mechanism of the self-regulating stubble cutter was 42N/mm. Then taking this as the main parameter and the self-regulating stubble cutter was designed. When the depth of the self-regulating stubble cutter was 25mm, the difference between the spring variable and the theoretical design value was 6.9%, and when the depth was 75mm, the difference between spring variable and theoretical design value was 7.3%. And the high speed camera showed that the performance of cutting stubble and soil of the self-regulating stubble cutter were good and the buffer mechanism was feasible, so the rationality and feasibility of the design idea were verified by both. Compared with disc cutter and notch cutter, the tillage resistance of the self-regulating stubble cutter was decreased by 13.3% and 20.6%, the oil consumption of the self-regulating stubble cutter was decreased by 19.3% and 35.3%, and the stubble breaking ratio of the self-regulating stubble cutter was increased by 16.1% and 4.6%, respectively. Therefore, the performance and work effect of the designed self-regulating stubble cutter were good.
XIAO Wenli , LIAO Yitao , SHAN Yiyin , LI Mengliang , WANG Lei , LIAO Qingxi
2021, 52(11):68-77. DOI: 10.6041/j.issn.1000-1298.2021.11.007
Abstract:The outer grooved wheel fertilizer apparatus commonly used in rape direct seeding machine, has problems of inadequate fertilizer stability and low consistency coefficient of each row. Therefore, a quad-screw double-row fertilizer discharging device was designed. The movement of fertilizer particles in the device was analyzed. The range of the screw pitch and the speed of screw rotation were studied. The discharging device was best performed when the number of discharging screw was four and the screw pitch was 24mm, which was analyzed by EDEM simulations. The bench tests studied the discharging affection for the speed of screw rotation and adaptability with different fertilizers. The results showed that the discharging rate was increased while the speed of screw rotation was added from 20r/min to 60r/min;the discharging rate of single-row was raised from 461.19g/min to 1328.57g/min as well. The coefficient of variation (CV) of discharging rate was dropped with the increment of the screw rotation speed. When the screw rotation speed was over 30r/min, the CV of discharging rate was less than 6.5%. The CV of the total discharge rate and the CV between two single-row were both less than 2.2%. Also the results showed that the quad-screw double-row fertilizer discharging device was compatible with different types of fertilizers commonly used for rapeseed direct-seeding in Hubei Province. The CV of three kinds of fertilizers were all in keeping with the fertilization standards, and the CV of the total discharge rate and the CV between two single-row was less than 3.3%. Field test results showed that when the actual discharging amount was set as 28.87kg, the error of the discharging device between the actual discharging amount and the theoretical amount was 2.33%, the CV of discharging was 6.73%, and the CV between two single-row were both 1.98%. The results showed that the quad-screw double-row fertilizer discharging device met the demand of fertilization for rapeseed direct-seeding. The research result may provide a reference for the structural improvement of fertilizer discharging device for rapeseed direct-seeding.
WANG Jinwu , YAN Dongwei , WANG Qi , TANG Han , WANG Jinfeng , ZHOU Wenqi
2021, 52(11):78-85,94. DOI: 10.6041/j.issn.1000-1298.2021.11.008
Abstract:Aiming at the problems of high labor intensity of weeding operations, the low weeding rate inter-plants and the seedling damage in transplanting rice field, a new method of weeding by water jet between plants in complex paddy filed environment was proposed. Based on the water jet weeding method and the mechanical structure design, a jet type inter-plant weeding device was designed. Firstly, by analyzing the structural characteristics of rice seedings, weed roots and submerged water jet, the injector angle was determined to be 31°and the diameter parameters of the injector was determined to be 0.004mm through theoretical analysis and parameter calculation. Combined with the momentum conservation theorem, the viscous fluid mechanics, and the soil mechanics analysis, the critical failure condition model of soil was established, and the critical pressure of earth breaking of the injector was obtained to be 0.53MPa. The extreme water pressure test of rice root system anti-breaking was carried out, and the maximum pressure limit of injector outlet was determined to be 1.5MPa. Besides, the bench test was carried out, the forward speed of the device and the pressure of the injector outlet were selected as the test factors, the weeding rate was used as the test index. Both the test index and the influencing factor regression model were established by using the method of secondary orthogonal rotation combination design. The Design-Expert 8.0.6 software was used to analyze and verify the test data, the results showed that when the forward speed of the device was 0.3m/s and the pressure was 1.5MPa, the weeding rate was 90.62%. The device can meet the agronomic and technical requirements of paddy field mechanical weeding operations.
WANG Shengsheng , LU Mengqing , HU Jinpeng , CHEN Pan , JI Jiangtao , WANG Fumin
2021, 52(11):86-94. DOI: 10.6041/j.issn.1000-1298.2021.11.009
Abstract:The Chinese cabbage seed market is developing rapidly, and the demand for mechanized harvest is increasing day by day due to the large area and industrial planting. Aiming at the technical problems of low efficiency of artificial harvest and high seed breaking rate by conventional threshing method, a threshing device for Chinese cabbage seed was designed, which was composed of threshing elements such as elastic short-rasp-bar tooth, flexible round head spike tooth and circular tube concave plate. The finite element modal analysis of threshing cylinder was carried out with ANSYS Workbench, and the rationality of structure of threshing cylinder was verified. The feeding amount, cylinder speed and threshing clearance were selected as experimental factors, and the response surface optimization and field comparison experiments were carried out based on the experimental indicators of seed loss rate and breaking rate. Through experiments, the mathematical model between each experiment factor and experiment index was established, the influence of each factor on the index was analyzed, and the structure and working parameters of the device were optimized. The experimental results showed that when the cylinder speed was 726r/min, the threshing clearance was 22.3mm, and the feeding amount was 1.73kg/s, the seed loss rate was 0.68% and the breaking rate was 0.39%.The experimental results met the design requirements, and it can realize the mechanized threshing operation of Chinese cabbage seeds with a low breaking rate during the harvest period.
TANG Qing , WU Jun , JIANG Lan , WU Chongyou , XIAO Tiqiong , JIANG Tao
2021, 52(11):95-102. DOI: 10.6041/j.issn.1000-1298.2021.11.010
Abstract:Planting depth consistency of rape is an important index to evaluate the transplanting quality, which directly affects the slow seedling period and the roots regeneration, and even the rapeseed yield. In order to improve the planting depth consistency of rape seedling combined transplanter, a hydraulic profiling system based on the profiling wheel height induction was designed. The simulated ground test in laboratory were conducted, and the test results showed that the track of the profiling wheel was consistent with the planter at different speeds. At the speed of 0.3m/s, 0.6m/s, 0.9m/s and 1.2m/s, respectively, the track change trend of copying wheel and planter was consistent with that of road surface, and the phase was delayed, the amplitude was decreased by 5.8%, 15.2%, 17.7%, 33.8% and 14.9%, 21.5%, 41.5% and 54.6%, respectively, and the phase difference was 0.0267s, 0.0119s, 0.0225s, 0.0366s and 0.182s, 0.1264s, 0.1278s and 0.1489s, respectively. Taking three factors of forward speed, planting unit weight and height difference value of ground as influencing factors, and the qualification rate of planting depth as the test index, the second orthogonal rotation combination design test of three factors and five level was conducted. The test results showed that the influence degree from strong to weak was: the planting unit weight, the height difference value of ground and the forward speed. The optimal parameter combination was modified. When the planting unit weight was 30kg, the height difference value of ground was 20mm and the forward speed was 1m/s, the qualification rate of planting depth was 90.27%. It was better than the standard value, indicating that the hydraulic profiling system can effectively control the planting depth and improve the consistency of planting depth.
WANG Bokai , YU Zhaoyang , HU Zhichao , CAO Mingzhu , ZHANG Peng , WANG Bing
2021, 52(11):103-114. DOI: 10.6041/j.issn.1000-1298.2021.11.011
Abstract:There were some problems during peanut picking and harvesting, such as high loss rate and high impurity rate, which affected the harvest quality and increased the harvest cost. In view of the problems of high loss rate and high impurity content in process of axial peanut harvester, according to the physical characteristics and air flow characteristics of various types of particles in peanut pod mixture, a winnowing system was designed. The motion state of four kinds of particles in air separation space were simulated and analyzed by Fluent-EDEM coupling analysis. Through numerical simulation experiments under different conditions, the working parameters and scope of winnowing system were established. Based on Box-Behnken’s central combination design theory, response surface experiment was carried out to analyze the influence of various factors on winnowing loss rate and impurity rate and influencing factors. The experimental results showed that the significant order of influence of air separation loss rate was impurity suction height, cross-flow fan speed and seedling suction height. The remarkable order of impurity content was cross-flow fan speed, impurity suction height and seedling suction height. The optimal parameter combination was as follows: cross-flow fan speed of 1508r/min, seedling suction height of 181mm and impurity suction height of 211mm, and the corresponding air separation loss rate and impurity content were 1.52% and 1.01%. Compared with that before optimization, it was decreased by 1.42 percentage points and 1.26 percentage points, respectively. The research results could provide reference for the research of air separation system of peanut picking and harvesting machine. This experiment was based on the air separation system of axial-flow peanut full-feeding harvester, and the experiment object was only “Shanhua 9”. It was suggested that the performance of different peanut varieties and harvesting equipment with different structures should be discussed in depth.
GENG Lingxin , LU Fuyun , ZHANG Lijuan , LI Yang , WANG Hengyi
2021, 52(11):115-124. DOI: 10.6041/j.issn.1000-1298.2021.11.012
Abstract:In view of the problem of low mechanization of garlic bolts harvesting in China, a garlic bolt picking machine was designed based on the traditional manual picking principle, which completed the process of scratching the stem of garlic plants and clipping the garlic bolt from the bottom through the scratch of stem and clip garlic bolt device, and completed the process of pulling out and transporting garlic bolt through the garlic bolt extraction device. According to the physical characteristic parameters of garlic bolt and garlic plant, the structure design of key components was carried out. Through theoretical analysis, the relationship between the forward speed of the machine and the speed of key components was determined. ANSYS simulation analysis of the garlic bolt clamping process of silicone rubber sheet was carried out to determine the garlic bolt clamping gap of 2mm. Needle chain gap, drum speed and gripper closure start angle were selected as the test factors, successful garlic bolt pulling rate, garlic bolt pulling damage rate and leaf retention rate were selected as the test indexes, the ternary quadratic orthogonal rotation combined test was carried out. The results showed that when the needle chain gap was 3.92mm, the drum speed was 48.32r/min and the gripper closure starting angle was 78.53°, the successful garlic bolt pulling rate, garlic bolt pulling damage rate and leaf retention rate were 89.10%, 20.55% and 77.34%, respectively.
PENG Caiwang , ZHOU Ting , SONG Shisheng , FANG Qin , ZHU Haiying , SUN Songlin
2021, 52(11):125-134. DOI: 10.6041/j.issn.1000-1298.2021.11.013
Abstract:In order to build a collision model between black soldier fly larvae and key parts of collecting, transporting or separating equipment, a restitution coefficient measuring device based on biological nature of black soldier fly larvae and kinematics was designed, and the restitution coefficient of black soldier fly larvae was measured and analyzed by experiment.Research on the collision materials, the thickness of collision materials, falling height, collision angle, drop direction and moisture content of black soldier fly larvae’s effect on the restitution coefficient of the ‘the fifth age’ black soldier fly larvae was conducted by a mixed orthogonal experiment based on the scheme of L16(44×23). Then, single factor experiments for factors, including the collision materials, thickness of collision materials, falling height, collision angle, drop direction were carried out and the corresponding regression equations were obtained by analysis.Results of orthogonal experiments showed that the order of significance of restitution coefficient influencing factors was as follows: collision material, falling height, collision angle, drop direction, material thickness and moisture content. The influence of falling height and drop direction were extremely significant (P<0.01), and the influence of material thickness, material thickness and collision angle were significant (P<0.05), and the moisture content was not significant.Single-factor experiments were carried out for the following factors: collision material, material thickness, falling height, collision angle and drop direction. Regression equations were established between restitution coefficient and collision material, material thickness, falling height, collision angle and drop direction, with all the regression coefficients no less than 0.9427. Results of single-factor experiments of collision materials showed that restitution coefficient was decreased in the order as follows: Q235 steel, aluminum alloy, acrylic glass and rubber.From collision experiments of black soldier fly larvae with Q235 steel, restitution coefficient was decreased with the increase of falling height, increased with the increase of steel thicknesses and collision angle, and restitution coefficient was larger when the lateral fall of black soldier fly larvae collided with the steel than the vertical drop. Those results above can be an important reference in the designing and developing of collecting, transporting or separating equipment for black soldier fly larvae.
QIU Ning , ZHU Han , ZHOU Wenjie , PAN Zhongyong , YUAN Shouqi , LIU Xiang
2021, 52(11):135-143. DOI: 10.6041/j.issn.1000-1298.2021.11.014
Abstract:Cavitation is a complex phenomenon, and the generation of shock waves is closely associated with cavitation compressibility. With the aim to explain the mechanism of cloud cavitation shedding and shock wave propagation, experiments were carried out in a cavitation tunnel. Pressure pulsation was recorded by pressure sensors and cavity structures were captured by high-speed cameras. The filter-based density correction (FBM-DCM) method was used to modify the shear stress transfer (SST) turbulence model. The unsteady cavitation feature was obtained by simulation. It was found that numerical calculation was highly consistent with the experiment results. Moreover, the shock wave formed by the collapse of the large cloud cavity and the pressure pulsation were captured. During the process of cavity structure evolution, the vorticity was relatively low and uniform in the area covered by attached cavity. It was unstable for the flow in the region filled with cavitation clouds. After the cavitation clouds were pulled away from the wall, they would be transported downstream pushed by the mainstream. When large-scale cavitation clouds collapsed to a minimum volume at the vast room behind the trailing edge of hydrofoil, they released pressure pulse of high amplitude. Overall, in the attached cavitation area, the pressure value was at a low level and rose when the shock wave arrived. When the water temperature was 33℃, the angle of attack was 12°and the cavitation number was 1.4, the propagation velocity of the shock wave between 46% and 32% of chord length was about 11.53m/s in the simulation, and it was similar to 11.31m/s obtained by experiment.
NIU Wenquan , ZHANG Erxin , Lü Chang , SUN Jun , DONG Aihong , WU Menglong
2021, 52(11):144-152,169. DOI: 10.6041/j.issn.1000-1298.2021.11.015
Abstract:Underground drip irrigation is the best way of aerated irrigation, but the narrow channel of the dripper is easy to be clogged by particles in the water. It is of great significance to improve the operation efficiency of aerated drip irrigation system if the law of fine sediment transport and deposition under aerated conditions can be found out and reasonable control measures can be taken to alleviate dripper clogging. In order to explore the influence of aeration on the dripper clogging, five kinds of sediment graded muddy water (0~0.100mm, 0.075~0.100mm, 0.050~0.075mm, 0.031~0.050mm and 0~0.031mm) with sediment concentration of 1g/L were disposed and the effect of aeration in water on the toothed labyrinth channel dripper clogging was studied by periodic intermittent irrigation test. The deposited sediment was observed and analyzed by laser particle size analyzer and field emission scanning electron microscope. The results showed that aeration and sediment particle size had significant effect on dripper clogging (P<0.01). Aeration improved the sediment transport capability in the laterals, promoted the discharge of large particle sediment, reduced the median particle size of depositing sediment and the effect of aeration on sediment transport was decreased with the decrease of the maximum particle size of sediment. The mass of depositing sediment and the median particle size of depositing sediment in the laterals were 8.75%~31.92% and 8.59%~35.64% lower than those without aerated treatment. When the particle size was 0.075~0.100mm, the relative flow rate of the dripper was decreased the fastest and the relative flow rate of the dripper was decreased the slowest when the particle size was 0~0.100mm. Aeration enhanced the degree of flow turbulence and promoted the transport of large-particle sediment in the flow channel. Aeration promoted the adhesion of small-particle sediment at the entrance of the flow channel and accelerated the clogging of the flow channel entrance. The Dra and Cu of dripper were 9.0~18.7 percentage points and 16.2~36.4 percentage points lower than those without aerated treatment. The above were the main reasons for aeration aggravates the clogging of the dripper. It was suggested that lateral flushing should be carried out to reduce the risk of channel entrance clogging and improve the anti-clogging capability of aeration drip irrigation dripper.
ZHANG Xu , WANG Pengfei , RUAN Xiaodong
2021, 52(11):153-160. DOI: 10.6041/j.issn.1000-1298.2021.11.016
Abstract:In order to study the influence of splitter blades on the performance of mixed-flow pumps with the effects of fluid-solid interaction, a certain type of mixed-flow pump with large flow was used as the research object, and the two-way fluid-solid interaction coupling method with dynamic mesh deformation was used. The influence of the presence of splitter blades on the unsteady pressure fluctuations and the resulting structural dynamic characteristics of the mixed-flow pump were studied. It was found that the presence of splitter blades greatly reduced the maximum value of pressure fluctuation amplitude which was induced by rotor stator interaction. However, the presence of splitter blades had an effect of reducing the rate of fluctuation dissipation. The splitter blades had little influence on the average value of the axial force. When the effects of fluid-solid interaction were considered, the average value of axial force was reduced and there were fluctuations. Besides, the presence of splitter blades had an effect of reducing the fluctuation amplitude of total stress and deformation. The maximum stress area occurred in the intersection of the blade and the hub/shroud. The maximum stress of the blade was reduced by the presence of splitter blades, and the stress gradient was reduced, resulting a more uniform stress distribution. The blade deformation was more uniform in the circumferential direction due to the presence of splitter blades, and the eccentricity of the deformation distribution was reduced. The research results could provide some references for the optimal design of the mixed-flow pump.
WANG Qi , CHANG Qingrui , HUANG Yong , SHI Botai , LUO Lili
2021, 52(11):161-169. DOI: 10.6041/j.issn.1000-1298.2021.11.017
Abstract:The relationship between the spatial variation of soil total nitrogen (STN) and the natural and human environment in different climatic regions was revealed by using geographic detector model,a method of spatial counting to detect spatial variation and identify the driving factors, in Shaanxi Province. The results showed that the STN content was generally high in the south and low in the north, and presented a moderate intensity of variation in the 2020s, with an average content of 0.91g/kg. The average STN content in Qinba District was the highest (1.40g/kg), and the lowest (0.37g/kg) in Central Mongolia. On the whole, STN variation was more affected by natural factors than human factors, and influenced by the single factor of soil organic matter content (q value of 0.63~0.86) mainly, and secondly the county-level administrative divisions (q value of 0.13~0.67). Among other factors, the city-level administrative division and the duration of sunshine were more influential in Shaanxi Province, q-value both reached more than 0.50;in Qinba District and Central Mongolia District, the higher driving factor was the soil subtypes (q value of 0.22~0.30);the degree of influence of municipal administrative division was the highest (q value of 0.31) in Weihe District;the fertilizer application in Shanxi-Shaanxi-Gansu had the greatest influence (q value of 0.47);and the available phosphorus content (q value of 0.26) in the eastern Inner Mongolia was the higher driving factor on STN variation. The influence of factors was interactive on the variation of STN, the synergistic effect of the STN showed mutual enhancement or non-linear enhancement and the interaction of the two factors enhanced the influence of the single factor on STN.
YANG Xinting , WANG Jiewei , XING Bin , LUO Na , YU Huajing , SUN Chuanheng
2021, 52(11):170-180. DOI: 10.6041/j.issn.1000-1298.2021.11.018
Abstract:In order to solve the problems of distrust source of animal husbandry supervision data, complicated identification of livestock, and poor confidentiality of sensitive breeding data, an identity authentication scheme based on blockchain technology and aggregated signature algorithm was proposed to ensure the authenticity of the data source and the transmission safety. The identity authentication trust between blockchain nodes and sensing devices was realized, and the fine-grained identity examination from the blockchain network to the nodes and downstream access devices was guaranteed, so as to complete the traceability of identity of access devices on and off the chain of blockchain system. This scheme can complete the identity verification of the equipment and solve the problems of complex individual identification of equipment and difficulty in the asset supervision. The security of the authentication scheme was analyzed. The results showed that the average change rate of the diffusion test ciphertext was 93.61%, and the average change rate of the correlation test ciphertext was 93.28%. In addition, the scheme had efficient batch authentication performance. By dynamically aggregating and forwarding the signature data, the traffic was reduced from linear level to constant level, and the signature verification time was saved by 40.01% on average. It can effectively reduce the data transmission traffic and system verification overhead, and meet the needs of equipment authentication in the process of animal husbandry supervision.
FENG Quanlong , CHEN Boan , NIU Bowen , REN Yan , WANG Ying , LIU Jiantao
2021, 52(11):181-189,218. DOI: 10.6041/j.issn.1000-1298.2021.11.019
Abstract:Urban villages (UVs) belong to a special product of China’s rapid urbanization process, which have similar properties to the informal settlements abroad. Specifically, UVs in China usually have a high population density due to the reconstruction of buildings, making it a big challenge in China’s urban and rural sustainable development. Especially under the background of “promoting the newtype urbanization” issued by the government, timely and accurate identification of UVs is of great significance to both urbanrural planning and urban fine management. Researchers usually obtain the spatial information of UVs by field research in traditional studies, which is both laboursome and tedious. Remote sensing, on the other hand, has the merits of synoptic view, dynamic and fast screening of the earth surface, which has been recently applied in the recognition of UVs. Meanwhile, deep learning has shed new light on UVs’identification due to its capability in learning high-level abstract image features, however, it has been rarely documented in the mapping of UVs. Therefore, the objective was to propose a deep learning model for UVs’recognition from very high resolution (VHR) remote sensing images. In specific, the proposed model was a multi-scale dilated convolutional neural network (MD-CNN), which included a series of multi-scale dilated convolutions and a non-local feature extraction module. The former can aggregate multi-level spatial features to adapt to the variability of UVs’shapes and scales, while the latter extracted global semantic features to improve the inter-class divisibility. The experimental results in Beijing City showed that the proposed model achieved good performance with an overall accuracy of 94.27% and a Kappa coefficient of 0.8839, which was better than that of several previous deep learning models such as VGG, ResNet and DenseNet. The research result demonstrated that by using the deep learning model, it was feasible and effective to accurately identify UVs from VHR remote sensing images, which could provide useful geo-spatial distribution of UVs for urban-rural planning.
ZHAO Qingzhan , JIANG Ping , WANG Xuewen , ZHANG Lihong , ZHANG Jianxin
2021, 52(11):190-199. DOI: 10.6041/j.issn.1000-1298.2021.11.020
Abstract:Tree species information is of great significance to forestry resource monitoring and management, timely and accurate control of tree species and growth status is the basis for protection forest project construction and benefit evaluation. In order to study the effect of using UAV hyperspectral images to classify protection forest tree species, the advantages of UAV hyperspectral images high-resolution, multi-band, and short-period were used, taking the “Three North” protection forest which on the northern edge of the 150th Regiment of the Eighth Division of Xinjiang Production and Construction Corps as the research area, typical areas were selected and Matrice600 hexarotor drones equipped with Rikola hyperspectral imaging senstor was used to obtain hyperspectral images. Firstly, spectral features, textural features, vegetation indices (VIs) and characteristics of mathematical statics were extracted from the UAV hyperspectral image, the support vector machine-recusive feature elimination (SVM-RFE) algorithm were used selection bands. Through the random forest algorithm to evaluate the importance of all features and combination with the overall classification accuracies was employed for feature reduction, and then four classification schemes of hyperspectral image full band, the best combination of original band, all feature variables, and feature variables based on random forest (RF) feature reduction were constructed. The classification results showed that the original band combination selected by the SVM-RFE algorithm based on crossvalidation proposed can better restore the original spectral features;when considering the four features (spectral features, textural features, hyperspectral Vis and mathematical statistics features) and after feature reduction, the three classifiers used, random forest (RF), maximum likehood classification (MLC) and support vector machine (SVM), the overall classification accuracies of RF was the highest, which were 95.93%, respectively. These results also suggested that vegetation indices were effective for discriminating tree species with similar spectral signatures. The overall results provided evidence for the effectiveness and potential of UAV hyperspectral data for protection forest tree species identification.
WEI Hongbin , LUO Ming , WU Kening , CHEN Tingyong
2021, 52(11):200-209,332. DOI: 10.6041/j.issn.1000-1298.2021.11.021
Abstract:For a comprehensive understanding of the pollution characteristics and ecological risk of heavy metals of farmland soil in Yingxing County of Yangtze River Delta,China,the cadmium (Cd),arsenic (As),copper (Cu),zinc (Zn),mercury(Hg) and lead (Pb) pollution situations were evaluated by using the single factor index,Nemerow pollution index and Hakanson potential ecological risk index,and the theoretical basis was provided for the safe use of regional cultivated land. The results showed that the heavy metal pollution of cultivated soil in Yixing County was generally light, and 10.27% of the soil samples had heavy metals concentrations higher than the risk screening values for soil contamination of agricultural land. The over standard rates of Cd, Cu, As, Hg, Pb and Zn were 10.11%, 0.88%, 0.44%, 1.49%, 0.10% and 0.35%,respectively.Cd and Hg were the main contaminants in Yixing County,the over standard rate of Cd was higher than that of cultivated land in China.In terms of the ecological risk,heavy metals of farmland soil in Yixing County showed a “light” ecological risk,with Cd accounting for 57.46% of the total ecological risk.The north-east of Dingshu Town, Xushe Town and the south-east of Zhangzhu Town were three areas with high ecological risk in Yixing County.The contamination of farmland soils in Yixing County may mainly come from man-made chemical production activities. Based on the ecological risk assessment of heavy metal pollution in cultivated soil of counties in the Yangtze River Delta region, the research result can provide the basis for the prevention and control of heavy metal pollution in cultivated soil, and improve the level of safe utilization of cultivated land resources.
CAO Shouqi , GE Zhaorui , ZHANG Zheng
2021, 52(11):210-218. DOI: 10.6041/j.issn.1000-1298.2021.11.022
Abstract:In order to promote the informatization development of offshore aquaculture, realize the monitoring of offshore aquaculture environment more accurately and conveniently, and solve the problems of poor prediction accuracy and robustness of traditional offshore aquaculture water quality prediction methods, an environmental monitoring system was designed based on buoy platform, which realized the remote collection and data storage functions of multi-regional environmental information monitoring data. On this basis, an improved genetic algorithm was proposed to optimize the offshore dissolved oxygen prediction model of BP neural network to realize the prediction of offshore aquaculture environment. The STM32L475 microcontroller was used to collect information such as illumination, temperature, pH value, dissolved oxygen and so on with the help of sensor network, and transmitted the data to the cloud monitoring platform through the Internet of things technology, thus realizing remote monitoring of multi-regional environmental information and multiterminal access. Through the analysis and research of classical prediction algorithms, a dissolved oxygen prediction model based on traditional algorithm optimization was proposed to realize the accurate prediction of offshore aquaculture water quality environment. According to the collected data of aquaculture environment, the initial weights and thresholds were optimized by improved genetic algorithm to obtain the optimal parameters, and then the BP neural network dissolved oxygen prediction model was constructed. Through experiments, the accuracy and reliability of marine environmental information collection and the effectiveness of dissolved oxygen prediction model were verified. Compared with the traditional neural network prediction model, the average error was reduced from 0.0778mg/L to 0.0178mg/L, which can meet the actual needs of offshore aquaculture.
LI Li , LAN Tian , ZHAO Qihui , MENG Fanjia
2021, 52(11):219-225,262. DOI: 10.6041/j.issn.1000-1298.2021.11.023
Abstract:Determining and classifying nitrogen deficiency is important for tomato planting. A nitrogen deficiency classification model based on the leaf color features of tomato was proposed. The accuracy of the proposed model can reach over 0.80. The leaf surface of tomatoes planted in summer were covered with glandular hairs. The glandular hairs were conducive to the absorption of water and nutrient elements in a tomato leaf. Under the same concentration of a nutrient solution, the yellowing process of these leaves was different from that of leaves without glandular hairs. Therefore, the accuracy of the classification model based only on leaf color features was reduced to 0.65. The two shape features, namely, the circumference and area of the hair-covered tomato leaves, were both smaller than those of the hairless tomato leaves. Thus, the two shape features of tomato leaf combined with the original leaf color features were used as model inputs to build a new nitrogen deficiency classification model for tomato. The image acquisition unit was constructed using Raspberry Pi and its camera module. Wireless data transmission among smartphones, image acquisition units and local computers was completed using WiFi or a 4G network. Smartphones remotely controlled the acquisition of images and transferred the obtained images through the Web interface to a cloud platform for storage. The local computer preprocessed the images to extract the leaf shape and color features, input the model for prediction, and output the prediction result. The test results showed that the image acquisition system worked properly with temperature ranging from 19.7℃ to 28.3℃ in spring and summer, and the illumination was in the range of 1.125~9.543lx. Preprocessing and segmentation of the acquired images removed any influence of the environment. Using the optimized weighted random forest model, the accuracy of the leaf nitrogen classification model based on shape and color features reached 0.83.
SU Baofeng , SHEN Lei , CHEN Shan , MI Zhiwen , SONG Yuyang , LU Nan
2021, 52(11):226-233,252. DOI: 10.6041/j.issn.1000-1298.2021.11.024
Abstract:In view of the lack of effective identification methods for grape cultivars identification under the field natural background, a residual network ResNet50-SE based on attention fusion mechanism was proposed to classify and identify grape varieties in different growth periods under natural background, and the identification effect of the network was analyzed and verified. The SE attention module was introduced into ResNet-50 network, and the recognition of grape shoots, young leaves and mature leaves in different periods was realized through transfer learning. Besides, in order to reveal the attention mechanism, the grape characteristics of different growth stages extracted from each layer of ResNet50-SE model were visualized and explained by the Grad-CAM visualization method. The t-SNE algorithm was applied to cluster the multi-features of different grape varieties extracted by the model, and then the performance of multi-features extraction of the model was intuitively evaluated. The results indicated that the ResNet50-SE network had a high recognition rate and strong robustness for grape multi-features recognition in different periods under the complex background conditions in the field. The accuracy rate of the model test set reached 88.75%, and the average recall rate reached 89.17%. Compared with AlexNet, GoogLeNet, ResNet-50 and VGG-16, the accuracy of the test set was improved by 13.61, 7.64, 0.70 and 6.53 percentage points. The attention mechanism can significantly reduce the influence of the background and strengthen the effective features. The model had a strong clustering effect on the features of different growth periods extracted from the training set. Therefore, the SE module can obviously improve the effect of ResNet-50 model in the feature extraction process, and effectively reduce the impact of field complex background on the classification results. The research result can provide a reference for the classification and recognition of grape cultivars multi-features under field complex background.
2021, 52(11):234-243. DOI: 10.6041/j.issn.1000-1298.2021.11.025
Abstract:LiDAR was one of the basic sensors for agricultural robot navigation in forests. However, due to the interference of the outdoor environment, obvious noise appeared in the LiDAR data, which reduced the navigation performance. To solve the problem that point cloud details are easily lost in point cloud denoising, an denoising algorithm was proposed based on dynamic filter radiu,and the denoising parameters were automatically determined. Besides, a convolutional neural network classifier was proposed, which was used to identify the planting pattern. By way of preset denoising parameters, it avoided the cumbersome parameter adjustment process and could be directly applied to dense planting and sparse planting scenarios. These approaches reduced the impact of point cloud density differences on noise removal, thereby achieving efficient denoising in large scenes. The denoising experiments in apple plantations, poplar forests and dry willow forests were completed. The results showed that the proposed method effectively removed multi-scale point cloud noise, and significantly reduced sparse outliers, dense noise, and noise around the target. It took 43.2ms to remove the noise of a single frame point cloud (6400 points). After denoising by the method, the accuracy rate of density clustering was 94.3%, and the recall rate was 78.9%. Compared with the original data, they were improved by 40.4% and 33.9%, respectively. The method had high real-time, versatility and robustness, and significantly improved the clustering effect.
QIN Lifeng , ZHANG Xiaoqian , DONG Mingxing , YUE Shuai
2021, 52(11):244-252. DOI: 10.6041/j.issn.1000-1298.2021.11.026
Abstract:The accurate extraction of cow targets serves as the basis for the behavior analysis such as lameness detection, ruminate and estrus. In order to realize the automatic tracking and monitoring of dairy cows in large-scale farms, the correlation filtering algorithm was integrated into the basic framework of target extraction, and a cow target extraction algorithm (CFED) that combined correlation filtering and edge detection to extract the cow target was proposed. Firstly, the correlation filters constructed by the color names and the Histogram of oriented gradient were applied to obtain the cow target range box. Then 13 edge filter templates in different directions convolved the target image box to get the edge image. Finally, the edge information and color feature were combined to extract the cow target. In order to verify the effectiveness of CFED algorithm, experiments were conducted on nine pieces of video samples of moving cows under different environments and interferences. The results showed that the average overlap rate between the CFED results and the manually marked results reached 92.93%, which was 35.63 percentage points, 32.84 percentage points, 20.28 percentage points and 14.35 percentage points higher than that of Otsu, K-means clustering, frame difference method and Gaussian mixture model method, respectively. The false positive rate and false negative rate of CFED were 5.07% and 5.08%, respectively. The average time cost was 0.70s per frame. This result showed that the proposed CFED algorithm had good target detection ability in complex environments such as weather, scale and occlusion, which can provide an effective method for accurate and rapid extraction of dairy cow targets.
ZHANG Quanbing , HU Shanshan , SHU Wencan , CHENG Hong
2021, 52(11):253-262. DOI: 10.6041/j.issn.1000-1298.2021.11.027
Abstract:With the aim to predict the wheat yield accurately, an improved wheat spikes detection method based on feature pyramid network was proposed. In order to solve the problem of misdiagnosis or omission in the detection results, channel attention mechanism and spatial attention mechanism were introduced into the coding and decoding regions of the original feature extraction network, which increased the extraction of spatial information and semantic information on the wheat spikes and effectively improved the detection performance of the network for obscured wheat spikes. At the same time, a weighted-region proposal network was designed to improve the input of the original region proposal network, in which several low-resolution feature maps with strong semantic information characteristics were fused together on channel levels. After a series of full connection layers and activation functions, the fused feature map was converted to probability of the corresponding channels, which were used to weight the underlying high-resolution feature maps to enhance useful information channels. Thus, a more accurately detection frame was generated for smaller spikes which were difficult to detect. The experimental results of the collected wheat spikes images showed that the method could significantly improve the detection effect of the shaded and smaller wheat spikes, where the precision of recognition, recall rate and average precision were 80.53%, 87.12% and 88.53%, respectively. Through the comparative analysis of wheat spikes detection results in different periods on the public ACID data set, the validity of the proposed method was further verified.
WANG Ruirui , LI Yiran , SHI Wei , DUAN Yunshan , CHEN Xingwang
2021, 52(11):263-270. DOI: 10.6041/j.issn.1000-1298.2021.11.028
Abstract:Mikania micrantha has strong climbing ability and amazing growth speed, which poses a serious threat to the surrounding ecological environment and biodiversity. Satellite remote sensing data is the main data source for identification and prediction of Mikania micrantha. However, the existing data have limitations such as low resolution, long transit time and cloud shielding, and the accuracy of identification and prediction of Mikania micrantha is low. In view of this, a method for automatic identification of Mikania micrantha outbreak area and invasion probability prediction based on airborne laser data and aerial multispectral data was proposed.Object-oriented multi-scale segmentation method was used to automatically identify the outbreak points of Mikania micrantha in the study area, and Logistic regression method was used to predict the invasion distribution probability of Mikania micrantha by using canopy height model, vegetation coverage, slope and slope aspect data in the forest farm. The results showed that the object-oriented multi-scale segmentation method could extract the Mikania micrantha outbreak area in the study area, and the identification accuracy was high, the misclassification rate was 4.66%, and the missed detection rate was 0.41%.Logistic regression model had a good prediction effect on the invasion distribution probability of Mikania micrantha, and the correct rate was 88.46%.This method can realize accurate identification and prediction of Mikania micrantha in a wide range, and can serve for comprehensive prevention and control and monitoring of Mikania micrantha, providing strong support for invasion monitoring of Mikania micrantha.
XU Jinghui , SHAO Mingye , LI Xiaobin , LIN Lei
2021, 52(11):271-277. DOI: 10.6041/j.issn.1000-1298.2021.11.029
Abstract:The determination of soil moisture content is of great significance for agricultural irrigation decision-making, crop yield improvement, effective management of water resources, and the study of soil mechanical properties. The open-ended coaxial probe method measuring the dielectric of soil was used to characterize the moisture content of soil, which is simple and accurate. Based on the open-end coaxial probe method, a quasi-static mathematical model was established for the measurement system with a short-circuit board. The appropriate thickness to be measured was selected to make the model suitable for the dielectric measurement of semi-infinite soil. Through the comparison of the full-wave simulation and model calculation results, the average absolute error of the real and imaginary parts were 0.001 and 0.022 respectively. Comparing the measured and theoretical values of the absolute ethanol dielectric, the average absolute errors of the real and imaginary parts were 0.375 and 0.279 respectively to verify the accuracy of the model. The model was used to measure and calculate loess soils with different moisture contents. The second-order polynomial fitting determination coefficient of real part of the obtained complex permittivity and the measured soil moisture content was greater than 0.965, indicating that the soil dielectric measurement model proposed was suitable for soil dielectric measurement of electrical value and moisture content.
GU Chenchen , ZHAI Changyuan , CHEN Liping , LI Qi , HU Li’na , YANG Fuzeng
2021, 52(11):278-286. DOI: 10.6041/j.issn.1000-1298.2021.11.030
Abstract:The effective detection of leaf area of target canopy in the orchard is the basic for the online calculation of the pesticide application rate. A three-dimensional test platform for leaf area measurement and a light detection and ranging (LiDAR) detection mobile test platform were built. Tree targets of different thickness and density were constructed for the two canopy types of dense and sparse tree targets. Partial least squares regression (PLSR) algorithm and back propagation (BP) neural network algorithm were used for canopy leaf area detection model among the number of LiDAR point clouds data, canopy thickness and canopy leaf area. The experimental results showed that the coefficients of determination (R2) of the equations of dense thick canopy, sparse thick canopy, dense thin canopy and sparse thin canopy obtained by PLSR algorithm were 0.9626, 0.4130, 0.8896 and 0.2699, and the R2 obtained by BP neural network of the canopies were 0.9727, 0.5302, 0.8993 and 0.4290, respectively. Based on the LiDAR canopy leaf area detection model, the detection accuracy of the dense canopy was high, the value of R2 was not less than 0.8896, and the detection accuracy of the sparse canopy was relatively poor, which was not higher than 0.5302. Comparing the PLSR algorithm and the BP neural network algorithm, the latter can significantly improve the accuracy of the model, and the R2 value can be increased by 0.1591. The proposed three-dimensional space tree target canopy leaf area detection method can be used to calculate dense canopy leaf area online to guide orchard accurate variable spraying.
LIU Hui , WEN Xiaoyan , LI Yutao , ZHANG Xinxin , FAN Yadong
2021, 52(11):287-296. DOI: 10.6041/j.issn.1000-1298.2021.11.031
Abstract:In order to explore the ecological benefits, economic benefits, and their coupling coordination degree of different biochar application modes on sloping farmland in the black soil area, an experimental study was carried out from 2015 to 2018, the 3° slope farmland runoff plot in the northeast black soil area was taken as the research object. Five treatments were set up in the experiment: conventional treatment without biochar (C0) and biochar application rates were 25t/hm2 (C25), 50t/hm2 (C50), 75t/hm2 (C75) and 100t/hm2 (C100). The entropy method and the coupling coordination degree model were used to measure the ecological, economic benefits and their coupling coordination degree of different biochar application modes. The results showed that biochar can effectively improve soil structure, enhance soil fertility, and improve soil water and soil conservation capacity. The ecological benefit of biochar was the best when biochar application rate was 50t/hm2 for two consecutive years. Meanwhile, biochar can effectively improve crop water-saving and yield-increasing performance, and increase the income and utilization efficiency of biochar. The economic benefit of biochar was the best when biochar application rate was 75t/hm2 for one year. The results of the coupling coordination degree calculation showed that the application of biochar can effectively reduce the inhibition degree of ecological and economic benefits. The best biochar application mode was to apply 50t/hm2 biochar for three consecutive years in the black soil area. The ecological and economic benefits of biochar were both high, and their coordination was optimal, which was 0.6849, 0.6345 and 0.5741, respectively. The research results can provide a theoretical basis for the efficient use of black soil resources and the actual production in black soil areas.
ZHANG Fan , REN Chongfeng , CAI Yanpeng , YANG Zhifeng , WANG Xuan
2021, 52(11):297-304. DOI: 10.6041/j.issn.1000-1298.2021.11.032
Abstract:The optimal allocation of agricultural water resources is an effective way to improve the utilization efficiency of agricultural water resources. The formulation of agricultural water resources allocation scheme needs to consider multiple conflicting objectives, which can be solved by building a multiobjective optimal allocation model. When solving such multiobjective models, the multiobjective model is often transformed as a single objective model with the goal of maximizing target achievement. However, such method can hardly reflect other aspects that the decision-makers are concerned about, such as the synergy degree of different goals and the impact of the scheme on the sustainable development ability. Moreover, setting only one index as the objective function cannot fully reflect the comprehensive impact of multidimensional optimization needs on the optimization scheme. Therefore, a composite multiobjective method was proposed to optimally allocate agricultural water resources based on the three indicators, including coordination degree of multiple objectives, sustainable development index, and target realization degree. In order to verify the effectiveness of the method, composite multiobjective method was applied to a real-world case in the middle reaches of Heihe River in Gansu Province for optimally allocating agricultural water resources among 17 irrigation districts. A multiobjective optimization model with objective functions of economic, social and ecological benefits was developed, and different solving methods were employed to solve the model. The optimization results showed that the agricultural water resources utilization coefficient can be increased by 5.42%~7.57% by using the composite multiobjective method. The results of single objective model were too extreme to be applied to practical water resources allocation comparing with results of multiobjective model. Compared with the multiobjective models which only used one index as the transformation objective function, the optimization scheme obtained by the composite multiobjective method can well reflect the multiple requirements of decision-makers for regional agricultural development and agricultural water resources allocation.
WEI Yongxia , JI Junchao , LIU Hui , GUO Yanjun , ZHENG Yanbo , SHI Yun
2021, 52(11):305-314. DOI: 10.6041/j.issn.1000-1298.2021.11.033
Abstract:In order to explore the effects of different water management schemes on greenhouse gas emission and soil inorganic nitrogen of dry direct seeding rice in the cold black soil region, micro-area test pits were used in the experiment. The effects of dry direct seeding rice on methane (CH4) and nitrous oxide (N2O) emission fluxes, global warming potential (GWP), global warming potential based on yield (GWPy), the contents of ammonium nitrogen (NH+4N) and nitrate nitrogen (NO-3N) in 0~60cm soil profile were studied. The relationships among soil temperature in 0~20cm soil layer, CH4 and N2O emission fluxes and content of NH+4N and NO-3N in 0~20cm soil layer were analyzed. Four treatments were set: flooded irrigation dry direct seeding rice (YH), wet irrigation dry direct seeding rice (SH), arid irrigation dry direct seeding rice (HH) and transplanting flooded rice (CK), and CK as the control. Results showed that the CH4 and N2O emission fluxes in four treatments showed the trend from increasing to decreasing, the CH4 emission peak appeared in the jointing and booting stage, and N2O emission peak appeared in the heading and flowering stage. The cumulative emission of CH4, GWP and GWPy in four treatments from big to small were as follows: CK, YH, SH and HH, the cumulative emission of N2O in four treatments from big to small were as follows: HH, SH, YH and CK. The changes of NH+4N and NO-3N contents in CK, YH and SH were basically consistent in time and profile. In terms of time, the peak of NH+4N content appeared in the middle tillering and the heading and flowering stages, while the peak of NO-3N content appeared in the early tillering stage. In terms of soil profile, the NH+4N and NO-3N content of CK, YH and SH were the highest in 20~40cm and 40~60cm soil layers, respectively. The contents of NH+4N and NO-3N of HH were the highest in 40~60cm and 0~20cm soil layers, respectively. The NH+4N was the most important nitrogen source for CK and YH, and NO-3N was the most important nitrogen source for SH and HH. The soil temperature of 5cm, 10cm, 15cm and 20cm soil layers (T5, T10, T15 and T20) of four treatments showed the tendency that firstly increased and then decreased. The T5, T10, T15 and T20 of CK, YH, SH and HH were positively correlated with CH4 emission flux and NH+4N content. In YH, the T15 and T20 were positively correlated with N2O emission flux and negatively correlated with NO-3N content. In SH and HH, the T5, T10 and T15 were negatively correlated with N2O emission flux and positively correlated with NO-3N content. In YH, SH and HH, the content of NH+4N was negatively correlated with the content of NO-3N. The research results can provide theoretical basis for the mitigation of greenhouse effect and efficient use of soil nitrogen in dry direct seeding paddy field in the black soil region of northeast China.
DOU Xu , SHI Haibin , LI Ruiping , MIAO Qingfeng , TIAN Feng , YU Dandan
2021, 52(11):315-322,420. DOI: 10.6041/j.issn.1000-1298.2021.11.034
Abstract:To explore the effect of controlling drainage on soil nitrogen loss, nitrogen fertilizer use efficiency and yield in oil sunflower farmland, the growth period control drainage depth was set to be 40cm (K1), 70cm (K2), and 100cm (K3), open ditch drainage was chosen as the control treatment (CK), and field trials were carried out. The results showed that the soil NH+4N content of K1 treatment was the highest, with an average value of 20.17mg/kg, which was significantly higher than that of other treatments(P<0.05), and was 31.36%, 46.16%, 15.22% higher than that of K2, K3 and CK treatments. The NO-3N content of 0~40cm soil after irrigation during the growth period showed the trend from large to small as K1, CK, K2 and K3. The loss of NO-3N in different treatments was greater than that of NH+4N. The loss of NO-3N in K1, K2, K3 and CK treatments was 60%, 52.63%, 30.77% and 58.82% higher than NH+4N, respectively. For the subsurface drainage treatment, the smaller the outlet depth was, the smaller the drainage and the nitrogen loss were, and the control of drainage stabilized the change of groundwater depth. The controlled drainage treatment (K1, K2) increased the partial productivity of nitrogen fertilizer by 3.04% ~ 11.15%, and increased nutrient absorption. The partial productivity of nitrogen fertilizer in K1 treatment was the largest, which was increased by 4.54%, 7.72% and 11.15% compared with K2, K3 and CK treatments respectively(P<0.05). K1 treatment can significantly increase corn yield(P<0.05), which was 4.52%, 7.69% and 11.14% higher than that of K2, K3 and CK treatments, respectively. After the oil sunflower was harvested, the NH+4N content of 0~100 cm soil in each treatment was 0.98~8.13mg/kg, and the soil NH+4N content was decreased with the increase of soil depth, the soil NH+4N content in 0~40cm soil layer of CK treatment was the largest, which was 11.65%, 14.55% and 18.19% larger than that of K1, K2 and K3, respectively(P<0.05). The NO-3N content in the same soil layer under the same treatment was significantly higher than the NH+4N content. After irrigation during the growth period, the NO-3N in the 0~10 cm soil would flow to the deep soil with water, while most of the NO-3N in the K1 treatment would be accumulated in the 20~40cm soil layer. In the middle and late stages of growth, the 20~40cm soil layer was the vigorous oil sunflower root layer, and the K1 treatment had relatively high nitrogen utilization in the soil. Considering oil sunflower yield, soil nitrogen change law, nitrogen fertilizer use efficiency and nitrogen loss, the suitable drainage method was to control the drainage depth of 40cm during the growth period (K1).
ZHANG Zuohe , ZHANG Zhongxue , LI Tiecheng , QI Zhijuan , ZHENG Meiyu , ZHENG Liying
2021, 52(11):323-332. DOI: 10.6041/j.issn.1000-1298.2021.11.035
Abstract:In order to reveal the rule of N2O emission from paddy fields under water and biochar management and the effects of nitrogen use and loss in different stages on N2O emission, two water management modes (dry-wet-shallow, conventional flooding irrigation) and four straw biochar application levels (0t/hm2, 2.5t/hm2, 12.5t/hm2 and 25t/hm2) were set up. The N2O emission from paddy fields, as well as the absorption and utilization efficiency and loss rate of basal fertilizer, tiller fertilizer and panicle fertilizer, were studied by combining field plot and 15N tracer micro plot. The relationship between N2O emission and the use and loss of nitrogen fertilizer in each stage was analyzed. The results showed that the N2O emission patterns of the two irrigation modes were different. The cumulative N2O emissions of the dry-wet-shallow irrigation mode were significantly higher than that of the conventional flooding irrigation mode (P<0.05). The cumulative N2O emissions of the two irrigation modes were larger at tillering stage and jointing booting stage. The cumulative N2O emission of dry-wet-shallow irrigation mode was higher than that of conventional flooding irrigation. The application of biochar reduced the cumulative N2O emission in each growth stage. The absorption and utilization efficiency of basic fertilizer was lower in dry-wet-shallow irrigation mode than that in conventional flooding irrigation mode, but the absorption and utilization efficiency of tiller and panicle fertilizer was significantly higher than that of conventional flooding irrigation (P<0.05). The application of appropriate amount of biochar could increase the absorption and utilization efficiency of nitrogen fertilizer applied in each stage. The correlation analysis showed that the total N2O emission was significantly and negatively correlated with the absorption and utilization efficiency of tiller and panicle fertilizer (P<0.05), and significantly and negatively correlated with the absorption and utilization rate of base fertilizer (P<0.01), and significantly and negatively correlated with the absorption and utilization efficiency of base fertilizer, tiller fertilizer and ear fertilizer under the conventional flooding irrigation mode (P<0.01);the total N2O emission under the two irrigation modes was significantly and negatively correlated with the loss of base fertilizer and tiller fertilizer. The loss rates were significantly and positively correlated (P<0.05).
PANG Guibin , ZHANG Lizhi , CONG Xin , PAN Weiyan , XU Zhenghe , XU Junzeng
2021, 52(11):333-342. DOI: 10.6041/j.issn.1000-1298.2021.11.036
Abstract:In order to reveal the photosynthetic physiological response mechanism for winter wheat under brackish water irrigation, a two-year field test was conducted in Yellow River Delta(2015—2016 and 2016—2017), Shandong Province, North China. Two irrigation treatments (irrigating 80mm with fresh water each at jointing, heading and milking stages, and irrigating 80mm with fresh (0g/L)- saline (3g/L)-saline(3g/L) water each at jointing, heading and milking stages) were designed. Test items included transpiration rate, net photosynthetic rate and stomatal conductance at the heading and flowering stages of winter wheat. Stomatal limitation and non-stomatal limitation values of leaf photosynthesis were calculated, meanwhile, changes of winter wheat leaf photosynthetic parameters of light response curve were observed. The results showed that in comparison with fresh water irrigation (CK), brackish water irrigation resulted in a significant increase of 37.8% and 64.3% of salt content in shallow soil layer (0~40cm) in 2016 and 2017, respectively, inhibited the transpiration at heading and flowering stages of winter wheat. Transpiration rate was decreased by 19.1% and 31.4% at heading stage, and by 11.6% and 11.0% at flowering stage in 2016 and 2017, respectively, the net photosynthetic rate was decreased before noon in the day, in which stomatal factors and non-stomatal factors inhibited leaf photosynthesis of winter wheat, but it can increase net photosynthetic rate in the afternoon, with a higher stomatal limitation value indicated that the non-stomatal factors were improved. The modified rectangular hyperbolic model of light response were introduced to obtain the photosynthesis parameters, the maximum net photosynthetic rate (Pnmax) of winter wheat under brackish water irrigation in 2015—2016 were increased by 2.27μmol/(m2·s) and 1.58μmol/(m2·s) at the heading and flowering stages, respectively, light saturation point (LSP) were increased by 29.27μmol/(m2·s) and 70.11μmol/(m2·s), light compensation point (LCP) was decreased by 19.38μmol/(m2·s) and 4.63μmol/(m2·s), dark respiration rate (Rd) was decreased by 0.96μmol/(m2·s) and 1.53μmol/(m2·s) compared with fresh water irrigation, while in 2016—2017, the maximum net photosynthetic rate (Pnmax) under brackish water irrigation were increased by 1.12μmol/(m2·s) and 1.83μmol/(m2·s) at the heading and flowering stages respectively, light saturation point (LSP) were increased by 15.07μmol/(m2·s) and 19.9μmol/(m2·s), light compensation point (LCP) was decreased by 7.87μmol/(m2·s) and 18.8μmol/(m2·s), dark respiration rate (Rd) was decreased by 3.33μmol/(m2·s) and 5.17μmol/(m2·s) compared with fresh water irrigation, it was showed that the saline water treatment enhanced the adaptability against strong light and high temperature conditions at the heading and flowering stages, promoted the ability using weak light of winter wheat. Therefore, brackish water irrigation did not negatively affect leaf photosynthesis in heading and flowering stage of winter wheat, but promoted the potential of utilizing light energy of winter wheat to some extent.
LI Kangji , ZHANG Shitong , MENG Fanyue , MAO Hanping
2021, 52(11):343-350. DOI: 10.6041/j.issn.1000-1298.2021.11.037
Abstract:Considering the temporal and spatial variation characteristics of greenhouse environment, the C++-Fluent joint optimization framework was established by constructing the greenhouse building computational fluid dynamics (CFD) model and combining the non dominated genetic algorithm with elite strategy (NSGA-Ⅱ), so as to realize the multi-objective and high-resolution optimization of greenhouse environmental factors. The CFD greenhouse model was verified by a greenhouse in Zhenjiang City, Jiangsu Province. The iterative optimization algorithm was implemented in C++ and the computing efficiency was improved by supercomputer. The optimization objectives included crop regional temperature field, carbon dioxide distribution and control of greenhouse fan energy consumption. The results showed that the CFD temperature field and velocity field were in good agreement with the experimental values at the monitoring points, and the average relative errors were 4.9% and 7.05% respectively. In order to obtain the optimal value of crop growth temperature field and carbon dioxide distribution in a certain scene and maintain low energy consumption of greenhouse fan, the greenhouse wet curtain temperature was [296.6K, 302K], and the fan outlet wind speed was [2.9m/s, 5.5m/s]. At this time, the temperature field, carbon dioxide distribution and fan energy consumption in the crop area were in the optimal range, which helped to improve crop yield and reduce greenhouse energy consumption. The computing efficiency of the optimization scheme developed under the supercomputer Linux system was significantly higher than that of the personal computer, and the computing time was shortened by about 88.09%. The strategy proposed fully considered the temporal and spatial variation characteristics of greenhouse environment and realized high-resolution and high-efficiency optimization of multiple environmental factors in greenhouse, which can provide a basis for the selection of greenhouse environmental parameters suitable for crop growth.
LIANG Feihong , SUN Dou , TU Te , JI Long , HE Qingyao , YAN Shuiping
2021, 52(11):351-357. DOI: 10.6041/j.issn.1000-1298.2021.11.038
Abstract:The combination of CO2 regeneration from CO2-rich solvent and atmospheric CO2 content increment in the agricultural greenhouse was explored when the membrane-based air stripping technology and CO2-rich potassium glycinate (PG) were adopted. Additionally, the method of CO2 content increase for tomato growth in the greenhouse was also put forward. Results showed that an increase of the initial CO2 loading of CO2-rich PG solution straight forwardly increased the CO2 regeneration efficiency and then the released CO2 amount under the conditions of 40~80℃ reaction temperature. A regeneration equilibrium can be obtained within 60minutes. Under the optimal operating conditions of 6L/min air stripping flow rate, 0.75mol/mol initial CO2 loading and 60minutes regeneration time, the released CO2 amount can be easily controlled only by regulating the rich PG solvent flow rate and regeneration temperature. Two approaches for increasing the atmospheric CO2 content in a standard greenhouse (600m3) were provided for improving the growth of tomato. Firstly, the atmospheric CO2 content was rapidly increased to the maximum value through CO2 regeneration from rich PG solvent, and then the required CO2 amount during tomato growth was supplemented according to the plant photosynthesis. Secondly, based on the calculation of total CO2 amount required for tomato growth in some times, CO2 form rich solvent regeneration was supplemented into the greenhouse at a fixed speed. Compared with the traditional method, this method using CO2 released from CO2-rich solvent as CO2 gas-fertilizer can obtain a lower cost and environmental sensitivity. For example, the CO2 generation cost can reduce by up to about 58.00%. For a bio-natural gas plant with 1000m3/d biogas yield, the released CO2 during biogas upgrading can be completely absorbed and fixed by the plants cultivated in the three multi-span greenhouses when the developed technology was used.
MA Benxue , LI Cong , LI Yujie , YU Guowei , LI Xiaozhan , ZHANG Yuanjia
2021, 52(11):358-366. DOI: 10.6041/j.issn.1000-1298.2021.11.039
Abstract:In view of the current single detection index of the jujube grading device, and it is difficult to realize comprehensive judgement of external quality, thus a dry Hami jujube external quality detection system based on deep learning and image processing was developed. Firstly, crack, bird peck and mildew defects were detected by deep learning image classification. To overcome the problems of large computation, high complexity and information loss of current residual network, an improved image classification method based on deep residual network was proposed. Secondly, according to the grade difference between size and texture quantity, a threshold detection method was proposed, which can realize the detection of size and fold by extracting the features of area, perimeter, fitting circle radius and texture quantity of dried Hami jujube image. The test results showed that the accuracy of models for detecting defect, size and fold were 97.25%, 93.75% and 93.75%, respectively. Combining three external quality indexes, the detection performance of the system was verified by online image acquisition. After testing, the comprehensive accuracy for detecting external quality was 93.13%, which can initially meet the production requirements of online detection equipment for dried Hami jujube quality. The reearch result can provide theoretical basis and technical reference for the development of rapid nondestructive detection system of dried fruit quality.
MA Huiling , CAO Mengke , WANG Dong , QIU Lingyu , REN Xiaolin
2021, 52(11):367-375. DOI: 10.6041/j.issn.1000-1298.2021.11.040
Abstract:Accurately predict the shelf-life of apple is urgently needed in practice. A feasible and non-equipment-depended data collection and model construction method was explored for shelf-life prediction of apple based on quality attributes observations and storage temperature. ‘Fuji’ apples were stored at four different temperatures of 0℃, 5℃, 15℃ and 25℃, respectively. The firmness, soluble solids content, titratable acid, SSC-TA rate, reducing ascorbic acid, starch content, weight loss and color values (L, a, b, ΔE, C) were measured periodically to obtain data set of 12 quality features at each storage stage and temperature. Feature selection method of SPCA and ReliefF was used to rank the quality attributes, respectively. Generative adversarial networks (GAN)-back propagation artificial neural network (BP-ANN), and BP-ANN were used to construct regression models between quality feature, storage temperature and shelf-life. Ratio of training set to test set was 3∶1. Totally 12 quality attributes were ranked in different orders by different feature selection methods. Using each accumulative combination of 1~12th quality attributes and storage temperature as input variables of GAN-BP-ANN and BP-ANN respectively, error rate of the validation set as evaluation criterion of prediction model. The accuracy of the models constructed by feature selection methods of SPCA were higher than that of ReliefF. The accuracy of the models established by GAN-BP-ANN were generally higher than that of the BP-ANN. It showed that GAN can effectively reduce the overfitting of BP-ANN model. Using three selected feature combinations as input variables, respectively, BP-ANN reached an accuracy above 0.930. GAN added BP-ANN can be a novel approach for accurately predict the shelf-life of postharvest “Fuji” apples by using the selected quality attributes and temperature.
2021, 52(11):376-383. DOI: 10.6041/j.issn.1000-1298.2021.11.041
Abstract:Machine vision has developed into a mainstream testing method in the field of nondestructive testing of poultry eggs due to its advantages such as high detection speed, high stability and low cost. A large-number of egg images are often used as data support to achieve better detection results. However, the collection cost of egg image data is relatively high,and it costs a lot of manpower and material resources. Therefore, it is hoped to find a method similar to face recognition for small sample egg image detection. To solve this problem, a prototypical network suitable for the detection of small sample egg images was proposed. The network used the inverse residual structure of attention-introducing mechanism to build a convolutional neural network to map different types of egg images to the embedded space, and Euclidean distance measurement was used to test the types of egg images in the embedded space, so as to complete the classification of egg images. The network was used to verify the classification detection effect of fertilized egg and unfertilized egg, double yolk egg and single yolk egg, cracked egg and normal egg under the condition of small sample. Its detection accuracy was 95%, 98%, 88%, respectively. The test results showed that the method effectively solved the problem of insufficient samples in the detection of poultry egg image, and provided an idea for the research of nondestructive detection of poultry egg image. In future nondestructive testing of poultry egg images, a small amount of poultry egg images can be collected to achieve better detection results.
LI Shangping , YAN Yuxiao , XU Bing , LI Kaihua , LI Wei , PENG Zhuo
2021, 52(11):384-393. DOI: 10.6041/j.issn.1000-1298.2021.11.042
Abstract:Aiming at the problems of difficult operation of sugarcane transporter in the hilly area and easy rollover accidents during the transfer process, a leveling control system for the scissor sugarcane transporter was designed. By building a sugarcane transporter test platform, the automatic leveling function of the body attitude was realized before sugarcane transfer based on the state measurement unit, single-chip embedded system, and hydraulic system. The function kept the body state within a safe range, and controlled the lifting and turning of the carriage to complete the actions required for the sugarcane transfer process. In order to study the factors affecting the stability of the car body, a critical operation test was carried out on the test platform with load of 120kg. The state parameters were selected as the lateral angle of the vehicle body as 0°, 2°, 4°, 6° and 8°, and the lateral span of the supporting structure as 490mm, 650mm, and 730mm, respectively. And the automatic leveling test was carried to verify the reliability of the stable control of the system using the “chasing” leveling strategy. The results showed that the lateral angle of the vehicle body and the span of the chassis support structure had a significant impact on its stability, and 730mm was the best lateral span of the support structure;when the lateral span of the supporting structure was 490mm and the initial lateral angle of the body was 6°, it was a critical state, and the sugarcane transportation process had safety risks. The designed system can level the transporter within 20s, and the accuracy can reach 0.3°;when the car body passed the leveling safety test, the vehicle can complete unloading operations such as car lift and transfer within 35s, satisfying the safety transfer and unloading within 60s. The control system improved the safety and work efficiency of sugarcane transporter in hilly areas.
ZHAO Bo , ZHAO Shimeng , MA Ming , CUI Baohui , WEI Liguo , WANG Hui
2021, 52(11):394-401. DOI: 10.6041/j.issn.1000-1298.2021.11.043
Abstract:Aiming at the problems of traditional laser elevation control technology, low control accuracy and poor adaptability of farmland pipe laying equipment, an elevation control system of trenchless pipe installation machine based on RTK-BDS was designed. The system was mainly composed of elevation detection system and elevation control system. The elevation detection system took RTK-BDS as the core, combined with the middle frame structure, used acceleration sensor, pulled wire sensor and other sensors, and adopted the multi-sensor information fusion algorithm of multi-model UKF to obtain high-precision altitude information;the elevation control system mainly controlled the height of the plow through the proportional valve control oil cylinder, and through the analysis of the mathematical model of the elevation oil cylinder control, the design was completed. The multi-mode fuzzy PID control algorithm was used to control the expansion and contraction of the oil cylinder, so as to realize the working requirements of the plow according to the specified slope index. Through the static test, UKF, particle filter and multi-model UKF algorithm were used to detect the elevation information. The test showed that the filtering effect of multi model UKF algorithm was better, and the maximum relative detection error was 0.181cm, and the average relative error was 0.051cm. In the dynamic situation, the tracking effect was better and the relative error was smaller. Through the field test, the elevation control experiment without slope, the elevation control experiment with slope and the comprehensive experiment were carried out. The results showed that the elevation control error can be kept within ±2cm, which can meet the requirements of pipe laying by trenchless pipe laying machine.
RAO Chenyang , XU Lingmin , CHEN Qiaohong
2021, 52(11):402-410. DOI: 10.6041/j.issn.1000-1298.2021.11.044
Abstract:Parallel manipulators with two rotations and one translation have been attracted the interest from both academic and industry. They can be selected as parallel modules and used in the workpieces machining. A systemic stiffness modeling and performance analysis of a 2-UPR-PRU three degrees of freedom parallel manipulator was presented based on the screw theory and strain energy, where U, P and R denoted universal, prismatic and revolute joint, respectively. Firstly, the inverse kinematics of the 2-UPR-PRU parallel manipulator was presented by using the closed-loop method. Next, considering the compliances of limbs, the stiffness matrices of limbs in the 2-UPR-PRU parallel manipulator were derived through the screw theory and strain energy, and the overall stiffness matrix of the parallel manipulator was obtained by combining the deformation compatibility equations. Under the external wrench, the deformations and overall compliance matrix of the 2-UPR-PRU parallel manipulator in different configurations were obtained, and a numerical simulation based on the ANSYS software was used to verify the correctness of the theoretical result. Finally, the distributions of virtual-work stiffness index were used to evaluate and discuss the stiffness performances of the 2-UPR-PRU parallel manipulator in different external wrenches and operational heights. The stiffness modeling and performance analysis of the 2-UPR-PRU parallel manipulator can provide an important reference for the design of prototype and the high precise control of system.
ZHAO Lei , YAN Zhaofang , LUAN Qianqian , ZHAO Xinhua , LI Bin
2021, 52(11):411-420. DOI: 10.6041/j.issn.1000-1298.2021.11.045
Abstract:Parallel robot is a kind of nonlinear strong coupling system with many branches and joints. It has obvious advantages of high speed, high stiffness and large load. With the number of joints increasing, its control accuracy is generally not high. In order to improve the accuracy of 3-RRRU parallel robot, kinematic modeling and error calibration method were systematically researched. Firstly, the kinematic equation and error model were derived by DH theory and space vector method. On this basis, the error model of the robot was derived and established with the partial differential theory. Secondly, position data were collected by using laser tracker for straight line and curve path. Lastly, genetic algorithm was optimized and used to complete calculation. The experiment result showed that the tracking error was controlled between 0.14mm and 1.34mm based on the linear trajectory calibration, and the maximum error was greatly reduced from 9.36mm to 1.34mm. But this calibration mode was not suitable for curve path compensation. Its maximum error of curve compensation reached 5.08mm. The linear calibration was just suitable for straight path, and its compensation accuracy was also lower than that of curve calibration mode. After compensation, the maximum error of line trajectory and curve trajectory was respectively reduced to 1.18mm and 1.56mm. According to the experimental data, 3-RRRU robot had better accuracy in the central area of workspace. In summary, the proposed method owned high automation and its feasibility of the method was verified by experiments.
YE Wei , HU Lihuan , XIA Dongxin , ZHOU Zhejia
2021, 52(11):421-430. DOI: 10.6041/j.issn.1000-1298.2021.11.046
Abstract:A novel redundantly actuated parallel mechanism with three translational motion was proposed. It had four kinematic limbs that connected the moving platform to the fixed base. The output degrees of freedom of the mechanism was analyzed by using Lie Group theory and the modified Grübler-Kutzbach criterion. The parallel mechanism had three translational degrees of freedom, four actuated prismatic joints, and thus was redundantly actuated. Position model of the parallel mechanism was established. Inverse position solutions and direct position solutions with analytical expressions were derived. The partially decoupled motion feature of the mechanism was studied. Singularity analysis was conducted based on the derived Jacobian matrix. Workspace of the mechanism was analyzed. Velocity and acceleration of each joint and each part of the parallel mechanism were derived through screw theory. Dynamic model was established by using virtual work approach, through which the optimal joint torques were obtained. A numerical simulation based on the ADAMS software was carried out. The maximum deviation between the theoretical and simulation results was 0.6%, which verified the correctness of the theoretical model. Dexterity index and dynamic manipulability ellipsoid index were used to evaluate the kinematic and dynamic performances of the mechanism. Mapping relationship between the performance and dimensions were investigated. Dimensional optimization was conducted based on the performance atlas, which improved the performance of the mechanism. The proposed parallel mechanism can be used to construct a five axis grinding machine.
WANG Fenghua , LIU Zhiying , LAI Qinghui , XIONG Haihui , CHEN Kefan , LU Chaoyu
2021, 52(11):431-442. DOI: 10.6041/j.issn.1000-1298.2021.11.047
Abstract:Aiming at the problems of difficult parameter transfer, poor relevance and high requirements for designers in the process of parametric design of agricultural machinery models, a set of interactive creation system for model parametric design was constructed. The system used the concept of knowledge element design to create design knowledge through a man-machine interactive method to realize the personalized design and parametric modeling of the model. Combining the secondary development technology of SolidWorks and MySQL database management to realize the resource encapsulation of model parametric design, in order to weaken the limitation of professional background knowledge. Taking the grain harvester cutting device as the test object, the parameter relationship between the parts was analyzed, the parameter design rules were clarified, the design parameters were marked through the model preprocessing, and the model data set was looped to extract the basic information of the parameters, a human-computer interaction interface was established, and following the classification requirement of parameters, the quantitative and qualitative knowledge and information expression of design parameters were completed. The case analysis proved the feasibility and effectiveness of the system,and it was easy to understand and apply. At the same time, it can also provide technical support for the design and reuse technology of agricultural machinery and equipment.
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