Abstract:Digital design of modern agricultural equipment, which is one of the pillars of digital agriculture, is important for achieving a fully mechanized crop production system. Understanding how agricultural equipment interacts with agricultural materials is a prerequisite for designing superior agricultural equipment. Discrete element method (DEM) is a discontinuum-based numerical analysis and simulation method. Recent studies have shown that DEM is a promising method of addressing engineering problems in granular and discontinuous agricultural materials. The concept, development stages, and common software packages of the DEM were introduced. The determination of DEM contact models used in modeling agricultural soil and agricultural materials, including seed, biomass, feed, fertilizer, fruit and vegetables, were summarized and their parameter calibration processes were highlighted. It provided a state-of-the-art review of various DEM applications to improve crop farming systems such as soil tillage, seeding and planting, fertilizing and harvesting. The challenges faced by modeling and design engineers using DEM in modern agricultural equipment research and development were discussed and possibilities for improvements were proposed. The limiting factors of using DEM for wider and broader applications were computational intensity and the lack of an effective parameter determination method. Further fundamental studies on contact model and parameter calibration as well as the development of standardized simulation packages and methods needed to be prioritized. With advances in computing power and numerical algorithms for efficient computation, the DEM would emerge from the development stage and became a robust and cost-effective tool of equipment and process design and optimization in the agri-food industry.

Abstract:In order to solve the problems of low net recovery rate and large bud damage rate during the picking process of camellia fruit, by studying the binding force and branch characteristics of different varieties of camellia fruit, a twist-comb type camellia fruit picking end effector was designed. It produced a variety of forces on the camellia fruit during operation. The structure and working principle of the end effector were described, the key components were designed, the operation process of the end effector was analyzed, and the factors that affected the shedding of the camellia fruit were obtained. By measuring the binding force of different varieties of camellia fruit, it was concluded that the tensile force was mainly concentrated between 10N and 25N, the shear resistance was mainly concentrated between 5N and 15N, and the torsion moment was mainly concentrated between 0.015N ·m and 0.030N ·m. The measured torsional modulus of different varieties of camellia branches was between 2MPa and 7MPa. The results of single factor test showed that the performance was better when the rotating speed of the torsion component was 25~35r/min, the rotating speed of the comb roller was 75~85r/min, and the working time was 8~12s. The results of test showed that the optimal working parameter combination was 35r/min of torsion component, 85r/min of comb roller, and 12s of operation time. Under this working condition, the average net recovery rate of camellia fruit was 93.37%, the average damage rate was 13.16%.

Abstract:In order to improve the applicability of the orchard operation platform, the target workspace according to the planting mode was determined. The kinematics model established based on D-H method was derived on the basis of prototype development. The dimension deviation, volume and average operability of the platform were calculated as the indexes to evaluate the performance of the reachable workspace simulated by Monte Carlo method. The influence of the platform structure parameter rod length and joint variables (joint angle and link offset) on these three indexes were analyzed. The optimization function established by taking the performance of reachable workspace and compact structure as the optimization index was transformed into a single objective optimization function by analytic hierarchy process. The optimal parameters obtained by genetic algorithm were as follows: the length of rod 2 was 988mm, the length of rod 4 was 879mm, the range of joint angle 1 was [107°, 256°], the range of joint angle 3 was [-118°, -76°], and the maximum value of link offset 5 and 6 was 720mm and 340mm, respectively. Compared with the prototype, the dimension deviation of reachable workspace was decreased by 96.09% and 95.60%, volume was decreased by 4.69%, average operability was increased by 1.43%, sum of rod length was increased by 4.85%, and sum of joint variables was decreased by 3.11%. A three-factor three-level test with the platform load, cross slope angle and longitudinal slope angle as factors was designed. After the field test of the prototype workspace at orchard, the test results showed that when the load was 65kg, the cross slope was 15° and the longitudinal slope was 15°, the deviation between the actual reachable workspace and the target workspace was 16.2mm and 16.7mm, which were reduced by 93.89% and 93.76%, respectively. The research result can provide a reference for the structural parameter optimization of similar agricultural machinery.

Abstract:Considering the problem that in the broad width and high speed planting operation, there is a lack of distributor device of air-assisted centralized metering device which can match the planter to realize the stable seeding for rapeseed and wheat, a prototype of dome shaped distributor device that could achieve 24 rows seeding was developed. The working principle of the dome shaped distributor device was elaborated. The equation of the dome shaped surface of the distributor device and the relationship among the key parameters were determined. The influence of the conveying airflow and the structure of the distributor device on the seed delivery velocity were analyzed. The influence of the sphere radius of dome shaped upper arc plate, length of diversion baffle, and height of guiding seed outlet was tested with the quadratic rotation orthogonal combination experiment by DEM-CFD gas and solid coupling simulation. The experiment results indicated that when the sphere radius of dome shaped upper arc plate was 245mm, the length of diversion baffle was 20mm, and the height of guiding seed outlet was 20.5mm, the uniformity variation coefficient of seeding quality was better. Under the optimal parameters combination, the secondary mixing of seeds and conveying airflow could be realized effectively in the dome shaped distributor device, and the uniformity variation coefficient of seeding quality of rapeseed and wheat was 4.96% and 3.82%, respectively. The intelligent test platform for planting machines was used to carry out the seeding performance verification test of dome shaped distributor device under the better parameter combination. The bench test results showed that when the rotating speed of seed feeding device of air-assisted centralized metering device was 20~50r/min, the uniformity variation coefficient of seeding quality of the rapeseed was less than 5%, the variation coefficient of single row seeding stability of rapeseed was lower than 5.3%, the uniformity variation coefficient of seeding quality of the wheat was less than 3.9%, the variation coefficient of single row seeding stability of wheat was lower than 4.9%, and the damage rate was no higher than 0.05%, which met the performance requirements of rapeseed and wheat seeding.

Abstract:For the design of the pneumatic conveyor type metering system, wheat seeds were taken as test object to provide a reference basis, and through the calculation on the fluid dynamics and the coupling of the discrete element method to make numerical simulation. The standard k-εmodel of unsteady coupling Lagrangian algorithm coupling simulation was used to simulate the gas-solid two-phase flow. The high-speed camera technology was used to capture images of the seed movement process in the seed tube for the experiment. The collected image was processed by binaryzation, color inversion, differential and corrosion and processing. The seed movement distance was extracted according to the characteristics of the seed area and the position of the center of mass, and the actual movement speed of the seed was calculated. The simulation and test results showed that the seed velocity in the seed tube was mainly affected by the wind speed, but the seed application rate had little influence. The relative error range between the simulated and experimental values of seed velocity at different wind speeds was 4.28%~6.06%, and the ratio of simulation test results to real test results was approximately constant, which was supposed to be due to the influence of seed sphericity on movement speed. The results showed that the correction coefficient of the seed velocity in the seed tube was 0.95. Therefore, the simulation test of seed velocity through fluid solid coupling simulation had a high accuracy，which verified the feasibility of the method of measuring the seed velocity of the seed tube based on EDEM-Fluent gas-solid two-phase flow coupling simulation. The research can provide a new method for measuring the seed velocity in the seed tube.

Abstract:In order to meet the requirements of plant material bowl seeding agronomy on the seeder, a reasonable structure of air suction cylinder type precise seeding device for maize with plant material bowl tray has been designed. The structural parameters of key components are determined by theoretical analysis. The dynamic model of seed suction process is established. The main factors affecting the suction performance indicators are the negative pressure, the forward speed and the suction angle. The simulation design was carried out to determine the influencing factors further. Finally, the performance test of the seeding device was carried out. The orthogonal test of three factors and four levels was adopted taking the qualified rate, missing seeding rate and the repetition rate as the performance indexes. The results showed that the main factors affecting the qualified index were negative pressure, forward speed and seed suction angle. The primary and secondary factors affecting the missing seeding index were negative pressure, suction angle and forward speed; the primary and secondary factors affecting the replay index were ngative pressure, forward speed and seed suction angle. The optimal parameter combination is that the forward speed is 0.22m/s, the negative pressure is 1200Pa and the suction angle is 20°. Under this condition, the qualified index is 90.48%, the missing sowing index is 4.24% and the replaying index is 5.28%, which meet the design requirements.The average performance index in this paper is different from the national standard. After many experiments, it is found that the population flow characteristics in the seed box have certain influence on the seed filling performance, and then affect the seeding performance of the device. The impact of liquidity needs to be further studied in the future.

Abstract:In view of the high cost of vegetable mechanized sowing and the problem that the sowing quality needs to be improved, an electric control cone disc vegetable planter was developed based on the characteristics of small size of vegetable seeds, small spacing of sowing plants and shallow sowing depth. The seeding principle and seed movement process of the metering device, the force and edge curve of the opener were studied, and the structure of the key components such as the cone disc metering device and the opener were determined. The machine was mainly composed of chassis, frame, seed metering device, closed-loop control system, trencher and pressing wheel. Through the closed-loop control system, the speed of seed metering plate and the forward speed of the machine were matched. With the help of the electric control system, the machine can control the sowing speed in real time to ensure the precision and quality of sowing; with the way of continuous seed supply, cone disc seed separation and rolling wheel seed pushing, it can ensure the quantity and precision of sowing; with the help of the construction of the slide knife curve and the stress analysis of the covering mechanism, it can realize the low resistance ditch opening and covering the soil on the ground. The force and movement of seed in the process of seed arrangement were analyzed, and the conditions of seed movement and smooth seed filling were determined. The height of cone h was 55mm, the base angle θ was 30°, the width W of seed groove ring was 2.5mm, the depth T1 was 2mm, the radius of hole was 1.25mm, and the number of holes Z2 was 28. The key structure and motion parameters of the seed pusher were determined by the seed metering process and the matching relationship of the seed pusher structure. The diameter of the roller was 25mm, the radian was 0.8rad, and the structure size was the same. Based on the analysis of seed characteristics and seed quantity requirements, the primary and normal seed quantity of the seed feeder were determined. The effective length of the seed wheel groove lg was 9mm. The problems of seed blocking and damage were solved by means of continuous seed supply, cone plate seed arrangement and rolling wheel seed pushing, and the resistance of trench opening was reduced by means of sliding knife and covering soil on the ground. According to the requirements of trenching and covering soil, the edge of exponential curve and covering soil mechanism were determined to simplify the structure and improve the performance. The angle of penetration α was 120°. With spinach, leek and cabbage as the representative vegetable seeds, the experiment of sowing different types of seeds was carried out. The test results showed that the machine had high sowing quality and stable performance. The qualified index was more than 90%, the replaying index was less than 5%, and the missed sowing index was less than 5%, which met the national standard and the agricultural requirements of vegetable planting in the field. The research results provided a technology, equipment and method for mechanized precision planting of vegetables.

Abstract:It is well known that mulch technology can effectively improve crop yield, but residual mulch will also damage soil structure and cause agricultural pollution. At present, China has developed a variety of residual film recycling machine to solve this problem. Aiming at the problem of impurities congestion in the process of picking up plastic film with the following film recycling machine, a new film picking up mechanism was designed based on the existing types of film recycling machine. The main structural parameters of the height of the working rod of wheel to remove impurities and the spacing of wheel to remove impurities were determined by analyzing the separation process of membrane soil in the mechanism，and through the analysis of the process of picking up the mulch film, the travel speed of the machine and the rotation speed of wheel to remove impurities were determined. The rotating speed of the wheel to remove impurities, the moving speed of the machine and the spacing of the wheel to remove impurities were determined as the main factors of the test. The ratio of membrane to soil separation and the ratio of impurities removal were taken as the response values. Design-Expert 8.0.5 was used for regression analysis and response surface analysis, and the influence of various factors on the membrane soil separation ratio and the impurity removal ratio was determined by using this method. The results showed that the degree of influence on the separation ratio of mulched soil and the ratio of impurities discharged both were the rotating speed of the wheel to remove impurities, the moving speed of the machine and the spacing of the wheel to remove impurities. Moreover, a ternary quadratic regression model was established, which contained these factors. The nonlinear optimization method was used to optimize the parameters of the mechanism, the results showed that when the rotating speed of the wheel to remove impurities was 26.2r/min, the moving speed of the machine was 1.23m/s and the spacing of the wheel to remove impurities was 139.95mm that the maximum theoretical value of membrane soil separation ratio was 91.49%, and the maximum theoretical value of impurity removal ratio was 92.92%.

Abstract:Aiming at the problems of low weeding rate, easy damage to seedlings during operation of paddy field weeding devices in Northeast China, a curved-tooth oblique type inter-row weeding device was designed. Through the mechanical analysis of the buried ability of the wheel tooth entering the soil and the process of unearthed desorption during the operation of the weeding wheel, the corresponding mechanical model of the soil particles on the weeding wheel teeth was established, and the influence of the tooth structure on the operating performance was explored. The main structural parameters affected the weeding effect and the range of the parameters were determined through theoretical analysis, and a single-hinge structure profiling mechanism was designed. Combining with LS-DYNA simulation of display dynamics and rotating orthogonal experiment design, the optimal structure parameter combination of the curved-tooth oblique inter-row weeding wheel was obtained. The operation performance of the device was verified by field experiments. The research results showed that the weed burying effect and removal effect of the curved-tooth surface was better than that of the straight surface and the main structural parameters affected the performance of the curved-tooth oblique type inter-row weeding device were the curvature radius and the eccentricity of the weeding wheel. The simulation test showed that the optimal parameter combination was 65.86mm and 113.27mm, respectively. Field test results showed that the average weeding rate and average seedling damage rate of the device were 89.66% and 2.1%, respectively. The operation performance was stable, which can meet the agronomic and technical requirements of paddy field mechanical weeding operations.

Abstract:The setting of contact parameters and contact model parameters between materials would directly affect the reliability of discrete element simulation test results. In order to determine the parameters of discrete element simulation of bulk manure in Xinjiang orchard, simplify the crushed irregular bulk manure into spherical particles, considering the cohesion characteristics between particles of organic fertilizer, the contact model of Hertz-Mindlin with Johnson-Kendall-Roberts was used in simulation modeling. The method of combining simulation and physical test was used to calibrate the discrete element parameters of bulk manure. Through the simulation of the combination of different parameters, with the accumulation angle as the response value, the Plackett-Burman test was used to screen the discrete element simulation parameters of bulk manure, and the parameters that had a significant effect on the stacking angle were obtained, that was, the restoration coefficient of manure and manure, the restoration coefficient of manure and steel plates, and JKR; the Box-Behnken design methods was employed to establish and optimize the second-order regression model of repose angle and significance parameter, in order to obtaine these optimal values such as the recovery coefficient between manure and manure, the recovery coefficient between manure and steel plate and the JKR were calculated as 0.49, 0.34, 0.02J/m2, respectively. Comparing the accumulation angle obtained from the simulation with the optimal parameter combination and the physical test value, the relative error was 2.73%. The results showed that the calibrated parameters were reliable, which provided a basis for the optimization of simulation parameters of the mechanization process of orchard bulk manure.

Abstract:Aiming at the problems of low shelling rate and high breakage rate in the process of shelling ripe fresh Camellia oleifera fruits, a four-channel fully automatic shelling machine was designed. The shelling machine classified the Camellia oleifera fruit through four channels, so that the Camellia oleifera fruit within a certain size range entered the corresponding shelling drum. In the shelling drum, Camellia oleifera fruit was shelled through the comprehensive action of mutual impact with the shelling sleeve and collision, extrusion and rubbing between Camellia oleifera fruit. By selecting the ripe fresh Camellia oleifera fruit as the research object, the shelling rate of Camellia oleifera fruit and the breakage rate of Camellia oleifera seeds were used as the evaluation indicators, and the feed amount of camellia oleifera fruit, the twisting rate of the shelling bar and the diameter of the shelling rod was the experimental factor. The L9 (34) orthogonal test, analysis of variance and weighted comprehensive scoring method were used to analyze the shelling effect of the ripe fresh Camellia oleifera fruit shelling machine. The test result showed that the feeding amount of Camellia oleifera fruit was 1500kg/h, the twisting degree of the shelling rod was 30°, and the diameter of the shelling rod was 23mm, the shelling machine achieved the best shelling effect. The shelling machine was tested three times with the best combination of parameters, and the average value of the three tests was taken as the final shelling rate and breakage rate. After calculation and analysis, the shelling rate of the ripe fresh Camellia oleifera fruit shelling machine was 98.85%, and the seed breakage rate was 3.24%, the test results showed that the four-channel fully automatic Camellia oleifera ripe fresh fruit shelling machine reached the expected design goal and can well complete the Camellia oleifera fruit shelling operation.

Abstract:Flax is one of the important oil crops in Northwest China, and Gansu Province is one of the main producing areas of flax. To enhance the mechanization level of separating and cleaning of flax threshing materials, according to the different components types of flax materials, the operation mode of “air cleaning first, and then air-screen separating” was put forward, the separation-cleaning technological process of flax threshing materials was developed, and a double duct system of air-screen separating and cleaning machine for flax threshing material was designed. Through design selection and parameter calculation of key operating components of the prototype, the important working parameters of the three stage vibrating screen, double duct impurities aggregate device and dust suction device were determined. The working conditions for the parameters of the crank connecting rod of the vibrating screen obtained with different components of flax material were in different motion states on three-stage screen surface. For the relevant work performance test of prototype, when the electromagnetic exciter amplitude of the vibration feeding system was controlled at 14~18mm, the front duct air volume control handle in 2~4 gear, the rear duct air volume control handle in 4~6 gear, the vibration frequency of three-stage vibrating screen was 2~6Hz, the operating machine had a strong adaptability to flax threshing material. After the operation of the double duct system of air-screen separating and cleaning machine for flax threshing material, the cleaning rate of grains was 97.16%, the entrained loss rate of was 1.12%, the experimental results met the design requirements of operation machine. The research results can provide an important reference for small grain crop threshing material separating and cleaning equipment development.

Abstract:Planting grass under forest is an under-forest economic model commonly used in plantations in recent years. In the forest and grass planting model, it is difficult to harvest forages and labor intensity caused by narrow tree spacing, lush vegetation, uneven ground, and limited visibility. A crawler-type forest grass belt harvester was developed. Its main features were small width, flexible turning, strong ground surface adaptability and low ground pressure. It was suitable for harvesting forest grass and cutting hard weeds and sparse shrubs. Through literature analysis and field investigation, four design requirements based on the working environment in the forest was put forward, so as to analyze the walking system, cutting system and supporting frame of the harvester. The specific ground pressure of the harvester was calculated, the cutting trajectory of the cutter and the motion state of the forage after being cut was analyzed, and the force state and deformation of the frame under special working conditions was analyzed through a combination of theoretical calculation and simulation analysis. And the dangerous section of the frame was found and the structure of the frame was strengthened to ensure the safety and reliability of the harvester. According to the standard arrangement test of the forage harvester, the operating speed of the harvester was 0.42m/s, the cutting height was 7.6cm, and the cutting width utilization factor was 0.94. The results show that the crawler-type inter-forest grass belt harvester can adapt to the operating environment under the artificial forest, and it can be used for forage harvesting in the small-distance forest and grass planting mode, which can reduce the labor intensity of artificially harvesting forage.

Abstract:King grass has strong tiller ability, with high stalk fiber content and high moisture content. Based on the crushing device of forage harvester, a roller crushing device suitable for harvesting king grass was designed according to the demand of harvesting. The main structure and parameters were determined through theoretical analysis. The crushing knife of the device adopted a four-row symmetrical arrangement, which could effectively reduce the fatigue damage caused by the alternating introduction. A single factor test and a combined quadratic orthogonal rotation test were designed to explore the influence of rotating speed of feeding roller and the crushing roller on the evaluation indicators: stalk crushing pass rate and average length. Response surface analysis, regression analysis and target optimization were carried out on the results by Design-Expert. Regression equations and optimal combinations of parameters between the test factors and evaluation indicators were obtained. The results of single factor test revealed that the rotating speed ranges of the feeding roller and the crushing roller were 380~480r/min and 750~950r/min, respectively. Quadratic rotation orthogonal test and target optimization obtained the optimal combination as follows: the feed roller rotating speed was 416.5r/min, the crushing roller rotating speed was 950r/min, the qualified rate of stalk crushing was 98.30%, and the average length of broken stalks was 29.04mm. The bench test verification and the field test revealed that it had a uniform crushing effect, a high pass rate of stalk crushing and the average length met the requirements, which met the design requirements of the roller crushing device.

Abstract:In order to analyze the transient characteristics of tubular pump during non-regulative operating condition, a shaft-extension tubular pump with rapid-drop gate and slap doors attached was established, and a 3D numerical simulation for start-up process was investigated numerically. The rational speed was deduced by utilizing the moment balance equation. The movement of the gate with additional slap doors was specified based on the laying mesh and dynamic mesh technology. The simulation results showed good agreements with the test results. The result showed that the starting speed and the change of flow rate had obvious influence on the pressure gradient in the impeller section. The pump head was increased firstly and then decreased to the rated head during the start-up process. The maximum start head was 6.38m at the time of 2.25s, and the maximum pressure difference between front and rear of the slap door was 2.61m. As a result, the outlet gate with additional slap doors could effectively reduce the maximum start head and improve the safety factor of the pump unit. Meanwhile, the additional slap doors on the gate played a good role in the shunt during the start-up process, which can avoid the system instability caused by excessive water pressure in the outlet passage when the impeller speed rose fast and the gate was not fully opened.

Abstract:The Bayi District of Tibet is rich in rainfall and frequent geological disasters. The water conservation function of the forest ecosystem is vital to regional ecological stability. The stable performance of its functions depends on the spatial structure of the forest landscape. Therefore, the forest landscape should be studied accurately. The characteristics of the spatial structure are of great significance to the subsequent optimization of the layout. Taking Bayi District of Tibet as the research area, based on complex network theory and landscape ecology analysis methods, the forest ecological corridor was extracted through the least cumulative resistance model, and then the fragile ecological nodes on the forest ecological corridor were identified. It constituted a forest ecological network intertwined with “point-line-surface”. And the complex network static characteristic index and robustness analysis method were used to analyze the topological structure characteristics and anti-destructive ability of the forest landscape spatial network. The results showed that the degree distribution of the forest landscape spatial network in Bayi District of Tibet presented a power-law distribution and had the characteristics of non-scaling. The network had non-uniform characteristics, the network structure was less stable, and under random attacks, the edge and node recovery robustness was better than malicious attacks.

Abstract:Through GIS technology, using the MCR-FLUS-Markov model, and the urban agglomeration in central Yunnan was taken as an example investigation of the optimized allocation of a territory spatial pattern to put forward a method of optimization of territory spatial patterns based on an ecological security patterns. The layout of the territory spatial pattern in 2030 was studied under the following four modes: the expansion of the living space, development of the production space, protection of ecological space and comprehensive optimization scenario, and finally an optimization of the territorial spatial pattern of the study area was formed as coordinated living-production-ecological space. The results revealed that: using the MCR and the cumulative cost distance model to construct the ecological security pattern of urban agglomeration, five functional zones of ecological security patterns were formed, which were as follows: the core area of ecological space protection, edge area of ecological space protection, key area of production space development, edge area of production space development and concentration area of living space expansion. Coupled with MCR-FLUS-Markov model, optimal allocation results for living-production-ecological space were obtained for four scenarios in 2030, and the focus of the various scenario simulations set by the research were different. According to their dominant functions and multi-functional natures of the territory space, the optimized layout of the living-production-ecological space under the comprehensive scenario plan for the urban agglomeration in central Yunnan in 2030 were divided into living, production, ecological, living-production, living-ecological, production-ecological, living-production-ecological spaces, with the area of the production-ecological and ecological space as the smallest and largest, respectively. It was believed that a comprehensive scenario plan based on the coordination of the living-production-ecological space would be more reasonable, and the other three scenarios can be used to supplement and adjust the implementation of the fundamental, comprehensive scenario plan.

Abstract:In order to quickly, nondestructively and efficiently monitor the diseases and insect pests of red mite in chestnut trees, the hyperspectral images and RGB images of each leaf were collected from locally infected leaves, unevenly infected leaves, recovered infected leaves and infected leaves with different degrees of infection by using UHD185 hyperspectral camera and digital camera. The RGB images were used as reference to select the regions of interest (ROI) of each leaf. The spectral curves of ROI were extracted from the hyperspectral images, and six spectral features and characteristic wavelengths of green peak, red valley, low position, red edge, high position and high shoulder of the spectral curves were extracted by differential operation. A large number of measured data were used to analyze the leaf-level variation of the spectral characteristics and characteristic wavelengths of chestnut leaves with the damage degree of red mite pests and diseases, so as to obtain the best spectral characteristics for identifyingred mite pests. After that, the hyperspectral image of the experimental area was obtained by using the UHD185 camera carried by the unmanned aerial vehicle (UAV). The results showed that the best spectral characteristics of monitoring the harm degree of Chinese chestnut red mite were low position and red edge, and the coefficient of determination between red mite and disease and pest exceeded 0.6. The blue shift of characteristic wavelength could be found in mild red mite pest by using these two characteristics, which proved that the red mite pest could be found in 14～21d before the large-scale occurrence of red mite in chestnut tree by UAV hyperspectral remote sensing. The research result can provide a scientific basis for the timely management of diseases and insect pests.

Abstract:The visible-near infrared spectra and leaf copper ion concentration data of maize leaves under different concentration gradient of Cu2+ stress were collected. Then through the short-time Fourier transform (STFT) time-frequency analysis technology，the energy amplitude response of the corn leaf spectrum under different concentrations of Cu2+ stress was studied. Furthermore，the amplitude parameters of the characteristic bands were extracted，and the partial least squares regression (PLSR) method was used to invert the leaf copper ion concentration. It was found that the peak of energy amplitude obtained by STFT transform of the corn leaf spectrum showed a decrease trend first and then increase trend with the increase of Cu2+ stress concentration gradient，and it continued to move to the short wave direction with the increase of Cu2+ concentration gradient. The peak bands of energy amplitude of different concentration gradients were selected as the characteristic bands，and the energy amplitude of the characteristic bands that varied with the frequency domain were used as parameters to establish a partial least square regression model of leaf copper ion concentration inversion. The PLSR model accuracy performed good，and the determination coefficient of R2 was 0.9863. The other two sets of plant data in the same cultivation period were selected as the verification data，and the same STFT transformation for the verification data. The established partial least square regression model was used to invert the leaf copper ion concentration of the two sets of verification data，and correlation analysis with the measured leaf copper ion concentration of the verification group was conducted. The leaf copper ion inversion accuracy R2 was 0.8806 and 0.7331，RMSE was 1.563μg/g and 2.619μg/g，respectively. The research result showed that the spectral time-frequency analysis method can be used for rapid and efficient detection of corn leaves under Cu2+ stress, and provided ideas for the monitoring of heavy metal stress in crops.

Abstract:Leaf area index (LAI) is of great significance for crop growth monitoring, agricultural disaster stress monitoring and yield prediction. There are three red-edge bands (705nm, 740nm, 783nm) for Sentinel-2 satellite images, which are very sensitive to vegetation growth. Unfortunately, the spatial resolution of these three red-edge bands (20m) is inconsistent with that of visible and near infrared bands (10m), which limits the application of Sentinel-2 images. For solving this problem, the six bands with spatial resolution of 20m was reconstructed into the spatial resolution of 10m by using super-resolution for multispectral multiresolution estimation (SupReMe) algorithm. Using the reconstructed Sentinel-2 image, the corn canopy LAI was retrieved by using the PROSAIL radiative transfer model and the random forest machine learning method. The results showed that the space details of Sentinel-2 image were improved while the spectral invariance was maintained after reconstruction by using SupReMe algorithm. The determination coefficients (R2) of LAI retrieving using reconstructed image was improved from 0.70 to 0.68 compared with resampling Sentinel-2 image, and the root mean square error (RSME) was improved from 0.240 to 0.262. The results showed that the SupReMe method can be used to reconstruct the spatial resolution of Sentinel-2 image and the reconstructed image can be used to improve corn canopy LAI retrieving accuracy.

Abstract:Eliminating the soil background in multispectral images with unmanned aerial vehicles (UAV) to improve the inversion accuracy of soil water content (SWC) in crop root zone is an effective method. The winter wheat (in the jointing stage) under different water treatments was used as the research object. Firstly, the UAV-borne multispectral cameras was used to obtain the high-resolution multispectral images at five moments (09:00, 11:00, 13:00, 15:00 and 17:00). Secondly, the improved vegetation index threshold method was used to determine the classification threshold to divide vegetation pixels and soil pixels quickly, and the soil background was eliminated with the classification threshold. According to the threshold changes of the vegetation index threshold method, the effect of soil background on the canopy reflectance was studied. Finally, the inversion models of SWC with vegetation indices were established before and after eliminating the soil background. The research results showed that the improved vegetation index threshold method could eliminate the soil background in multispectral images effectively, and the elimination accuracy of vegetation index RDVI was the highest (the overall accuracy was above 91.32%); the effect of soil background on the canopy reflectance in the near-infrared band was the biggest, followed by it in the red edge band and the effect in the visible light band was the lowest; there was a linear relationship between the vegetation index and SWC before and after eliminating the soil background, and the inversion accuracy of SWC in winter wheat root zone was improved significantly after eliminating the soil background. The performance of NGRDI at the depth of 10~20cm was the best with R2 and RMSE of calibration dataset of 0.739 and 2.0%, and these of validation dataset were 0.787 and 2.1%, respectively.

Abstract:In order to meet the requirements of autonomous navigation and walking in field management such as intertillage and topdressing in maize seedling stage, the real-time detection technology of multiple crop row lines based on machine vision was studied. First of all, based on green component enhancement method, improved Otsu algorithm of segmentation threshold optimization, variable threshold denoising method and morphological denoising method, pre-processing such as grayscale, binarization and denoising was carried out. The pre-processing was not affected by natural light changes, shadows, precipitation/ponding and planting pattern, which had a better cleaning effect on the inter-row space of crops under the condition of plant canopy overlap or the interference of finely fragmentary weeds, and a better removal effect on the noise of small size, round leaf weed with scattered distribution between crop rows and weed in the form of transverse growth or aggregation. And then, the binary image was divided into 20 horizontal bars along the ordinate direction. The characteristic parameters of horizontal spacing and horizontal span were established for target areas inside each horizontal bar, and the characteristic parameters of vertical spacing, trend angle and coverage width were established between target areas across horizontal bars. Based on the distribution difference of the above parameters between target areas within crop rows and ones across crop rows, the localization and segmentation of target areas belonging to different crop rows in each horizontal bar and the clustering of target areas belonging to the same crop row in different horizontal bars were completed, and good segmentation and clustering results was obtained. Finally, the centerlines of each crop row in current frame were obtained by linear fitting based on the least square method after removing outlier feature points. The test results showed that the overall detection accuracy was no less than 91.2%, and the single-frame image processing time was no more than 368ms, which can quickly realize the synchronous detection of multiple crop row lines under the interference of different environmental factors.

Abstract:The number of maize seedlings is the essential information for sowing quality assessment. It is important to obtain the number of maize seedlings quickly and precisely for investigation and filling the gaps with seedlings. To improve the real time and precision of the acquisition of maize seedling number, the YOLO model (FE-YOLO) was improved, and the detection and acquisition of maize seedling number were realized. Firstly, dynamic ReLU was used to improve the bottleneck layer of MobileNet and the feature extraction performance of MobileNet was increased. Then, according to the target size and spatial texture characteristics of maize seedlings, the multi-receptive field fusion and spatial attention mechanism were used to enhance the feature expression. The experimental results showed that the FE-YOLO model enhanced the spatial texture characteristics of the seedlings, reduced the complexity of the model, made the mAP and recall rates reach 87.22% and 91.54%, respectively, and the floating-point operations per second and detection consumption time were only 7.91% and 33.76% of YOLO v3. FE-YOLO can detect the maize seedlings in the UAV orthoimage, and then Equation (13) was used to estimate the planting density. FE-YOLO had low complexity and high recognition accuracy, which can provide support for maize seedling management.

Abstract:In order to solve the shortcomings that the existing methods of measuring the area of plant leaves, for example, the traditional direct contact measurement can cause damage to the plant, and the laser scanner or structured light to reconstruct the 3D model is expensive and complicated. A non-destructive and multi-category measurement method of irregular leaf area was proposed. Firstly, smart phone was used to get images of plants, based on these images, the three-dimensional point cloud of plants was reconstructed by using structure from motion, and the noise of the leaf point cloud was removed by using threshold segmentation algorithm with HSV color space as features. Secondly,the three-dimensional point cloud was classified by using the fuzzy C-means clustering algorithm to segment the single leaf point cloud, and then, the surface mesh model of the single leaf was reconstructed by using the Delaunay triangular meshing algorithm. Finally, the leaf area was obtained by calculating the mesh area. To prove the proposed method, five different types of plant leaves with different shapes were measured, and it was compared with the real leaf area. The average error of the calculation result of the proposed method was 6.25% in terms of leaf overlap data, and from the perspective of the complexity of the blade shape, the average error was 4.81%. In addition, the samples had been added that actually overlap each other between the leaves for experiments, which increased the reliability of the experiment.The results showed that the method was stable and had high precision, meeting the needs of measuring the leaf area of irregular plants in multiple categories.

Abstract:Agricultural production is a significant part of Chinese economic development. The prevention and control of crop pests and diseases are critical measures to ensure crop yield. In order to improve the accuracy of the crop pests and diseases identification model, a new attention module I_CBAM improved from CBAM was proposed. By adopting a parallel connection structure of channel attention and spatial attention, the problem of interference caused by cascade of channel attention and spatial attention module was solved. By adding I_CBAM, the prediction accuracy of the model can be steadily improved. By adding I_CBAM to the five convolutional neural network models of InRes-v2, MobileNet-v2, LeNet, AlexNet, and improved AlexNet, the accuracy of Top-1 (61 types) reached 86.98%, 86.50%, 80.97%, 84.47% and 84.96%, respectively. Compared with the original model, it was improved by 0.51, 0.62, 1.74, 0.53 and 0.55 percentage points, respectively. The final results showed that the parallel mixed attention module I_CBAM proposed had better recognition effect on fine-grained classification of crop pests and diseases. And it also had good generalization in different other convolutional neural network models. Furthermore, by adjusting the channel attention ratio in I_CBAM to 32, the memory size of the MobileNet-v2 transfer learning model with I_CBAM was further reduced to 28.3MB. Meanwhile, the average time the model used to predict a picture was only 7.19ms, which made a good balance between the prediction cost and the prediction accuracy. Finally, the model was deployed on the mobile terminal mini application, which had a good visual application effect.

Abstract:The behavior of beef cattle reflects its health status. How to recognize and track beef cattle in a real breeding environment is very important to perceive the behavior of beef cattle. Wearable devices have limited accuracy in sensing motion behavior and are easily damaged,while monitoring devices are widely used in farms and have a long lifespan. Based on the improved YOLO v3 algorithm (LSRCEM-YOLO),surveillance video was used to achieve real-time tracking of beef cattle in a real breeding environment. MobileNet v2 was used as the object detection backbone network. According to the uneven distribution of beef cattle and the large change of target scale, long-short range context enhancement module (LSRCEM) was proposed for multi-scale fusion, combined with the Mudeep ReID model to achieve multiple targets for beef cattle track. The experimental results showed that in beef cattle object detection, the mAP index of LSRCEM-YOLO reached 92.3%, and the model parameter amount was only 10% of YOLO v3, which was also reduced by 31.34% compared with YOLO v3-tiny; in terms of beef cattle re-identification (ReID), based on adjusting the Mudeep model of the receptive field obtained more multi-scale features, and its Rank-1 index reached 96.5%. Compared with the original DeepSORT algorithm, the MOTA index of multi-target tracking was increased from 32.3% to 45.2%, and the number of ID switch was decreased by 69.2%. This method can provide technical reference for real-time tracking and behavior perception of beef cattle in real environment.

Abstract:Segmentation and extraction of birds contour is the premise of precision livestock farming management, such as behavior, health, welfare status monitoring based on machine vision technology. The precision and accuracy of image segmentation directly affect the reliability of relevant monitoring technology and decision-making. An instance segmentation approach based on Mask R-CNN deep learning framework was proposed to solve broiler instance segmentation and contour extraction problems in stacked-cage henhouse. Furthermore, a broiler image segmentation and contour extraction network was constructed to segment broiler images and realize birds individual contour extraction. In this network, totally 41 layers deep residual network (ResNet) based on attention mechanism and deformable convolution was integrated with feature pyramid networks (FPN) as the backbone network to extract the image features, and regions of interest were extracted by region proposal networks. Finally, target classification, segmentation and box regression were realized through network heads. Broiler image segmentation experiment showed that compared with Mask R-CNN network, the average precision and mean accuracy of the optimized network were improved from 78.23% and 84.48% to 88.60% and 90.37%, respectively, and the recall rate of the model was 77.48%, which can realize the pixel level segmentation of chicken contour. The research result can provide technical support for the real-time monitoring of birds welfare and health status.

Abstract:With the low-automation and stress problem of breeding white feather broiler, a non-contact weight estimation method combined with deep learning was proposed to estimate the weight of breeding white feather broilers quickly and accurately. Mask R-CNN and YOLACT (You only look at coefficients) was used to obtain the target mask and locate the target with position coordinate. The breeding white feather broilers can be completely stripped out from complex background. Then, the edge points of body were extracted for ellipse fitting, and the pixel body area can be obtained. Bivariate correlation analysis was used to show the significant correlation between body weight and body area which was linearly proportional to the pixel body area. The linear regression model between target pixel body area and body weight was established based on the least-square principle. The experimental results showed that the proposed method had a good effect. This method can accurately estimate the body weight of 28-week-old and 48-week-old breeding white feather broilers with different occasion, such as the ideal posture, the head extension, the head turning and partial occlusion. The average accuracy based on Mask R-CNN feature extraction was 97.23%, and the average accuracy based on YOLACT feature extraction was 97.49%. The lowest accuracy for single broiler in the group was 90.50%. The weight of breeding white feather broilers can be estimated quickly and accurately.

Abstract:Aiming at the problems of complex process, long processing cycle and low working efficiency existing in traditional artificial soil detection, a novel design method of pretreatment platform was proposed for detecting organic matter, which can accurately detect soil organic matter content by uniform and stable machine operation. Based on this method, a set of automatic pretreatment platform for soil organic matter detection was constructed. The platform was mainly composed of handling manipulator, temperature control digestion unit, nondestructive transfer unit and electrical control system. At the same time, the configuration software scheduling system was built to realize the collaborative work of each unit, and the automatic pretreatment of soil organic matter was achieved with the way of assembly line operation. Standard soil samples were selected to test the repeatability and suitability of the platform. The experimental results showed that the standard deviation of repeated tests was no more than 0.56g/kg, the relative standard deviation was no more than 2.30%, and the relative difference was no more than 2.21%. All the test results were within the error range required by the standard value, which met the index requirements of the Ministry of Agriculture and Rural Affairs of China for soil testing indicators. The automatic pretreatment platform proposed had high stability, which greatly improved the detection efficiency of soil organic matter detection without reducing the detection accuracy. The platform could replace the cumbersome process in traditional artificial soil detection, and it had a wide range of systemic applicability.

Abstract:For evapotranspiration (ETa) estimation, the solar radiation measurement equipment is expensive, it is hardly to deploy a large number of measurements, and the unit regression algorithm has low accuracy and poor generalization performance. An integrated algorithm based on illuminance was proposed to estimate ETa. Firstly, the illuminance instead of solar radiation was used as the input of the model, and a sunny index based on illuminance was proposed to improve the estimation effect. Secondly, an integrated algorithm that fused extreme gradient boosting model (XGBoost), light gradient boosting machine (LightGBM), random forest regression (RFR), support vector regression (SVR) was used to estimate the farmland actual evapotranspiration. The results showed that the illuminance could replace the solar radiation in the estimation of the actual evapotranspiration of farmland. The unit model and the integrated model were used to compare the ETa estimation results based on the illuminance and solar radiation, respectively. The maximum difference of root mean square error (RMSE) between the two methods was 0.031mm/h. The maximum difference of determination coefficient (R2) was 0.053. The sunny index helped the model better learn the distribution characteristics of evapotranspiration data under different weather conditions. Compared with the estimation result of the integrated model without adding sunny index, the RMSE was reduced by 0.028mm/h, and R2 was increased by 0.03. The performance of the integrated algorithm was significantly improved than that of the unit model algorithm. The optimal RMSE was 0.037mm/h and R2 was 0.985. The research explored the data sources, characteristic quantities and estimation algorithms required for estimating evapotranspiration, and provided a new idea for estimating farmland evapotranspiration.

Abstract:To investigate the applicability of the AquaCrop model to drip-irrigated cotton without plastic film in South Xinjiang, and develop the optimal irrigation scheduling, the AquaCrop model was calibrated and validated by using the dataset collected in 2018 and 2019 seasons, then the model was used to simulate canopy cover (CC), plant biomass, and cotton yield under two different irrigation scenarios. The results showed that the root mean square error (RMSE), the fit index (d), the standard root mean square error (NRMSE) and the determination coefficient (R2) between the simulated and measured values of CC were 6.03%, 0.12, 13.08% and 0.97, and the corresponding values for plant biomass and cotton yield were 810kg/hm2, 0.93, 6.41% and 0.80, and 751kg/hm2, 0.84, 14.02% and 0.87, respectively, indicating that the AquaCrop model could be used as a feasible tool to predict cotton growth and yield response to irrigation under drip irrigation without plastic film in this region. The scenario simulation was carried out by using the AquaCrop model with the meteorological data from 1960 to 2019. The scenario simulation results indicated that under the condition of the same irrigation frequency, the cotton yield was increased first and then decreased with the increase of the irrigation quota, 〖JP3〗and the maximum yield of 5398kg/hm2 was obtained with the total irrigation amount of 7200m3/hm2, and the water use efficiency (WUE) was 0.75kg/m3. While under the condition of the same irrigation quota, the cotton yield was increased with the increase of irrigation frequency, and the maximum yield of 5315kg/hm2 was achieved with the irrigation frequency of 5d and the total irrigation amount of 5400m3/hm2, and WUE was 0.98kg/m3. It could be concluded that the high yield and WUE of drip-irrigated cotton without plastic film could be ensured by the irrigation scheduling with the irrigation frequency of 5d and the total irrigation amount of 5400m3/hm2, which could be used as a reference irrigation scheduling for application of drip-irrigated cotton without plastic film in South Xinjiang.

Abstract:In order to study the effects of different nitrogen fertilizer synergist and water and nitrogen amount on the yield of winter wheat, a field experiment was carried out by using a split zone design. The main area had three water levels (W1:30mm, W2:60mm and W3:90mm), and subplot had three nitrogen levels (N1:75kg/hm2, N2:150kg/hm2 and N3:225kg/hm2). A non-nitrogen control was set under each main area (CK), and deputy vice district was treated with two kinds of nitrogen fertilizer synergists with urease inhibitor (NBPT) and double inhibitors (NBPT+DCD), using traditional fertilization (CO) as the control. The results showed that the yield of winter wheat was significantly affected by irrigation level, nitrogen application level and type of nitrogen synergist (P<0.01). The yield of winter wheat under three nitrogen fertilizer synergist was increased at first, and then decreased with the increase of irrigation water/nitrogen application rate. Compared with CO, the yield of NBPT and NBPT+DCD reached the maximum at 60mm of irrigation and 75kg/hm2 of nitrogen, which were 20.23% and 38.96%, respectively. Regression analysis and frequency analysis showed that NBPT could achieve higher yield of winter wheat in the range of 139~183kg/hm2 nitrogen application and 47~67mm irrigation. The yield reached the theoretical maximum of 7409kg/hm2 when nitrogen application was 162kg/hm2 and irrigation was 48mm. Under the treatment of NBPT+DCD, the yield of winter wheat was higher when nitrogen was applied at 149~185kg/hm2 and irrigation water was 50~65mm. Among them, the theoretical maximum yield was 8329kg/hm2 when nitrogen was applied at 158kg/hm2 and irrigation water was 51mm. When the maximum yield was obtained by CO treatment, the nitrogen application interval was 143~247kg/hm2, and the irrigation interval was 49~63mm, and the corresponding yield within this interval was 5912~6443kg/hm2. It can be seen that both NBPT and NBPT+DCD had obvious effect of increasing yield and saving fertilizer, and NBPT+DCD was better.

Abstract:Through the field plot experiment design control group (CK), organic fertilizer combined with desulfurized gypsum (T1), biochar (T2) and desulfurized gypsum (T3) four treatments, the effects of different improvers on the quantity of soil microorganism, physical and chemical properties and the yield of processing tomatoes were analyzed, and the best improver was determined. The results showed that all amendments could reduce soil EC and pH value, increase soil organic matter, hydrolyzed nitrogen, available phosphorus and available potassium and increase the yield of processing tomatoes. Among them, biochar treatment had the most significant effect on improving the yield of processing tomatoes, which increased by 55.96% compared with CK treatment. The number of bacteria and actinomycetes in the soil of each treatment showed a parabolic change, the maximum values appeared in the flowering and fruiting period, and the number of soil fungi showed a downward trend in the whole growth period. The application of biochar, desulfurized gypsum and organic fertilizer compound with desulfurized gypsum can increase the number of bacteria, actinomycetes and fungi in soil, among which the increase of bacteria and actinomycetes in biochar treatment was the largest, which was 1.6~7.8 times and 2.0~6.1 times higher than that of CK treatment, respectively. The number of bacteria and actinomycetes in topsoil was negatively correlated with soil EC and pH value, and positively correlated with soil organic matter, hydrolyzed nitrogen, available phosphorus and available potassium. The above results showed that the number of soil microorganisms was decreased with the increase of soil salinization degree, which had good positive correlation with most soil nutrients. In addition, the soil with a large number of bacteria and actinomycetes had better physical and chemical properties and higher crop yield, so the number of soil bacteria and actinomycetes can be regarded as an important biological index for evaluating soil health. To sum up, biochar treatment (T2, 22.5t/hm2) was the most beneficial to reduce the EC and pH value of moderate saline alkali soil, promote the growth and reproduction of soil microorganisms, improve soil nutrients and the yield of processing tomatoes.

Abstract:The critical nitrogen dilution curve can be used to diagnose crop nitrogen nutrition. In order to construct the leaf critical nitrogen concentration dilution curve of summer maize based on LAI, the field experiments with different water and nitrogen applications were carried out in Guanzhong Plain from 2018 to 2019. Three water levels (rain fed (RF), deficit irrigation (DI) and full irrigation (FI)) and four nitrogen levels (0kg/hm2, 90kg/hm2, 150kg/hm2 and 210kg/hm2) were set to study the response of leaf critical nitrogen dilution curve based on LAI to different water levels. The quantitative relationship between nitrogen nutrition index (NNI) and relative yield was analyzed. The results showed that the relationship between LAI and leaf nitrogen concentration was power function. The leaf critical nitrogen dilution curve based on LAI under RF was significantly affected by the interannual variation (P<0.05), while the leaf critical nitrogen dilution curve based on LAI under DI and FI was not significantly affected by the interannual variation (P>0.05). The dilution rate of leaf critical nitrogen dilution curve based on LAI under RF was significantly higher than that under DI and FI (P<0.05), but there were no significant difference between DI and FI (P>0.05). The critical nitrogen dilution curves of DI and FI treatments were fitted, and a unified critical nitrogen dilution curve was obtained (R2=0.90, P<0.01). In the range of nitrogen application, NNI was increased with the increase of nitrogen application, and the range was 0.62~1.16. The relative yield of RF treatment was 85% of the maximum yield, and that of DI and FI treatment was over 99% of the maximum yield. Therefore, 75% ETc (ETc is the water demand of summer maize) and 150kg/hm2 of nitrogen were recommended for fertigation in Guanzhong Plain. This results can provide reference for the precise management of water and nitrogen of summer maize in Guanzhong Plain.

Abstract:In order to monitor the concentration and improve the accuracy of harmful gases during layer breeding, the monitoring system based on improved particle swarm optimization back propagation (BP) algorithm was developed. Wireless ZigBee module, sensor module and STM32 module were used to construct the data collection hardware platform at each point of the layer house, the general packet radio service remote communication module was used to transmit the data to the server, the mobile application (APP) software platform was developed to monitor the layer house in real-time. Based on the linearly decreasing weight and the improved learning factor strategy, the particle swarm optimization BP pattern recognition algorithm was used to process the data. Because of the cross-sensitivity caused by common gas sensors in complex environments, the data was not accurate, to improve the accuracy of harmful gas, improved particle swarm optimization optimized BP neural network model was developed. The environmental monitoring data of a chicken house in Baoding, Hebei Province was analyzed, and the effectiveness of the improved particle swarm optimization BP neural network model algorithm was verified by comparing the measured value with the real value of the sensor. The measurement accuracy of the SGP30 carbon dioxide was increased from 81.75% to 94.69%, the measurement accuracy of the MQ135 ammonia was increased from 61.83% to 91.23%, that of the MQ137 ammonia was increased from 70.18% to 91.23%, that of the MQ136 hydrogen sulfide was increased from 62.35% to 92.80%, and that of TGS2602 hydrogen sulfide was increased from 62.97% to 92.80%. The design process of terminal collection node, server and mobile phone APP in layer house environment was given. The functions of the system were verified by experiments.

Abstract:Hydrochar from hydrothermal carbonization of biomass are regarded as one of the most promising electrode materials for supercapacitors owing to its low-cost, high carbon content and porosity. However, there were few studies on durian shell hydrochar via hydrothermal carbonization as a high-value porous carbon material. In order to explore the performance of durian shell hydrochar as electrode material, the hydrochar was prepared from durian shell via one-step hydrothermal carbonzation process at 250℃, 10h and liquid-solid ratio of 10g/g. The elemental composition, structural characteristics and electrochemical properties of the hydrochar were analyzed. The results showed that the C content of the hydrochar was 70.29% and its O content was 16.96%. There were abundant oxygen-containing functional groups on the surface of durian shell hydrochar. The prepared hydrochar contained appreciable amount of amorphous carbon, and some were close to graphitization. Moreover, the hydrochar exhibited a BET specific surface area of 38.74m2/g and an average pore size of 4.67nm. In a three electrode system with 6mol/L KOH as electrolyte, the cyclic voltammetry curve of the hydrochar prepared as working electrode presented a symmetrical rectangular shape. The partial pseudo capacitance was provided by the functional groups containing heteroatoms. The galvanostatic charge-discharge curve approximately presented triangle shape. Durian shell hydrochar exhibited a high specific capacitance of 344.83F/g at 1A/g and good rate performance. The electrochemical impedance curve showed a steep slope in the low frequency region, which showed good electrical properties and certain cycle stability. The achieved electrochemical performance demonstrated that durian shell hydrochar could be used as electrode materials for supercapacitors and low-cost energy storage materials.

Abstract:In order to reveal the optical properties of carrot slices during infrared drying, the appearance quality of carrot slices during infrared drying was analyzed. The content of soluble solids in pulp and cortex of carrot slices, the texture of pulp and cortex of carrot slices during drying were determined. The surface reflectance spectrum, absorption spectrum and ultrastructure were analyzed. It was found that the energy consumption per unit of material had linear negative correlation with the 5th power of absolute temperature. The browning occurred when the moisture content was decreased to 20%, and the browning degree of the infrared drying material was higher than that of the hot air drying material at the same temperature. When it was dried at 60℃ for 1.5h, the hardness of the upper surface of the pulp was higher than that of the lower surface, and the hardness of the lower surface of the cortex was higher than that of the upper surface, which indicated that the moisture content of the upper surface of the cortex was lower than that of the lower surface, and the moisture content of the upper surface of the pulp was higher than that of the lower surface. The spectral curve of 350~2500nm showed that the reflectance of cortex was higher than that of medulla in any wave band, and the difference was more obvious in the short wave band. Scanning electron microscope images showed that the diameter of the pores in the medulla was larger and the tortuosity was lower than that in the cortex, which was conducive to the transmission of infrared rays to the deep layer. Transmission electron microscope images showed that the number of particles in cortex was more than that in medulla. According to the scattering theory, short wave light had Mie scattering, and long wave light had Rayleigh scattering in the cortex, short wave light had Rayleigh scattering, and there was no Mie scattering in the medulla. The reflectance of the cross section with porous surface was lower than that of the longitudinal section with dense surface.

Abstract:To investigate the effect of high-pressure homogenization on the structure and emulsification of soybean protein, high-pressure homogenization (HPH) treatment at 20min and 100℃ were applied to the soybean protein thermal aggregates (HSPIs). The changes of HSPIs structure characteristics (particle size distribution, turbidity, skeleton structure, secondary and tertiary structure, hydrophobicity, potential, sulfhydryl) and emulsification characteristics (rheological characterization, emulsification and emulsification temperature) were assayed. The results showed that compared with the heat soluble aggregates degree, the lower pressure of HPH can promote the re-aggregation of the thermal induced HSPIs, which resulted in the increase of particle size and turbidity, the densification of HSPIs skeleton structure. Along with the re-aggregation, the HSPIs disordered structure, particle ζ-potential and protein peptide chains disulfide bond content were increased, and resulted in the increase of emulsifying activity and decrease of hydrophobicity. While on HPH, strong strength homogenization can lead the disulfide bond and skeleton structure of HSPIs broken, the protein spatial structure was opened, and the hydrophobic sites were exposed, which resulted in enhancement of hydrophobicity, shortening of protein peptide chain, decrease of particle size and the increase of ζ-potential, and then the decrease of emulsifying activity of HSPIs. The results for the modification of soybean protein functional properties and the application by high-pressure homogenization changed HSPIs.

Abstract:Aiming at the problems of low power matching degree and poor fuel economy of the existing agricultural machinery speed regulation strategy, taking hydrostatic tractor as the platform, the cruise control system of the tractor was designed based on CAN bus. The system was composed of a tractor working condition acquisition module, a throttle control module, a variable pump displacement adjustment module, a work tool lifting control module, and a communication module. Devices of throttle adjustment and load adjustment were developed. Tractor working condition data was analyzed. Mathematical model of throttle opening, variable pump displacement and tractor speed was established. A strategy for cooperative control of engine speed and variable pump displacement was developed. The cooperative control strategy experiments on empty cement roads, empty farmland and flat working conditions were conducted; and the experiment of the fixed throttle control strategy, the throttle displacement coupling control strategy and the throttle displacement cooperative control strategy was carried out under the flat operation conditions. The test results showed that the absolute error of speed control of the cooperative control strategy was 0.005m/s, 0.007m/s and 0.012m/s under the three working conditions of cement pavement, field no-load and flat land operation; the cooperative control strategy reduced the engine speed under the premise of achieving the target speed. The control system can reduce fuel consumption while ensuring the accuracy of speed control.

Abstract:The hand-eye calibration and inverse kinematics solution of the 6-degree-of-freedom robot based on visual servo control has always been the core problem in this field. With the application scene becoming more complex, the traditional hand-eye calibration method cannot meet requirements. At the same time, based on the single BP neural network inverse kinematics algorithm, the error tends to be saturated or even larger, which cannot further improve the network performance with the increase of network depth to a certain extent. In order to solve the above problems, the problem of hand-eye calibration and inverse kinematics was integrated into the problem of fitting the mapping relationship between the coordinates of the target image and the joint angles of the 6-degree-of-freedom series robot, and a residual BP neural network algorithm was proposed，the multiple residual network modules were used to deepen the depth of the BP neural network, and the input information of the residual module can be transmitted across layers in the network. It solved the problem that the gradient of the network model was easy to disappear and cannot improve the network performance with the increase of depth. In addition, the space of the inverse kinematics solutions was divided into eight unique regions by the six-degree-of-freedom robot Jacobi equation, and the training data were processed based on this way, the influence of multi-solution of inverse kinematics of multi-degree-of-freedom robot on network learning was avoided, and the accuracy of network training results was improved by two orders of magnitude, and the training speed was increased by two times. Finally, two-dimensional plane grasping and three-dimensional physical grasping experiments were carried out in the REBot-V-6R 6 degree of freedom robot conveyor line sorting system, and the experimental results verified the accuracy of the method. Compared with single-layer BP neural network, three-layer BP neural network and five-layer BP neural network, the training accuracy was improved by four orders of magnitude, two orders of magnitude and five orders of magnitude, respectively, and the testing accuracy was improved by two orders of magnitude，and the computational cost of inverse kinematics was saved and the accuracy was improved by one order of magnitude.

Abstract:According to the complexity of motion modeling and low control accuracy of the continuum robot due to its flexibility and redundancy of freedom, a dynamic modeling method of the cable-driven continuum robot with nonlinear friction was proposed. Firstly, the kinematics model of the continuum robot was derived to analyze the relationship between the end pose and joint parameters, and the velocity kinematics model was presented for the convenience of mechanical analysis. Then, a dynamic model with considering of the inertial force, elastic force, gravity force and driving force, was established based on the Kane’s method to analyze the mapping relationship between its motion and the force applied to the robot. Moreover, the force transmission characteristics of the cable-pulley system were analyzed by the improved Capstan equation, and a feedforward control strategy based on the established motion model and the nonlinear friction was presented to compensate the loss of the transmission force. Finally, the simulations and motion experiments were carried out to verify the established model and the proposed control method of the continuum robot. The results showed that the established dynamic model with nonlinear friction can well reflect the deformation characteristics of the continuum robot, which can be used as a reference for the shape reconstruction of the robot in future research.

Abstract:Based on the finite position method, a zero coupling planar high-speed stamping mechanism with two end effectors was designed and analyzed for complete shaking force balance. Firstly, the mechanism was divided into three sub-kinematic chains (SKC) by topological analysis, and the number of connecting branches and branches in each sub-kinematic chain was determined according to the principle of tree system division. Then, the position of the mechanism was analyzed. The mass moment of each sub chain was solved in turn, and the relationship between the total mass moment and the angular position of each component was obtained. By calculating the total mass moment of the mechanism at five different positions, multiple linear equations were established, and the balance weight parameters m*i and p*i of each branch member were obtained. Finally, the influence trend of m*i and p*i on the total center of mass track fluctuation and the total inertial force after balancing was analyzed. It was found that the change of m*i had a greater impact on the final balance effect. When m*i was 0.002kg, compared with that before balancing, the components of the total mass center trajectory fluctuation and the total inertial force in the x and y directions were decreased by 44.44%, 59.78%, 72.94% and 5.40%, respectively, which verified the validity of the condition of complete balance of the pendulum force. The finite position method was simple, effective and easy to program by computer. The research result provided an idea for solving the condition of complete balance of mechanism shaking force.

Abstract:In order to study influence of flexible rod on the dynamic characteristics of the spatial parallel mechanism, the 3-RRPaR spatial parallel mechanism with structural redundancy was taken as the research object, and a general method for establishing rigid flexible coupling dynamic model of redundant spatial parallel mechanism was proposed. A three-dimensional two node beam element model was established based on the absolute node coordinate method. The structural characteristics of the mechanism were studied, and the rigid flexible coupling dynamical equation of the mechanism was derived by Lagrange multiplier method. The generalized α method was used to solve the dynamic equation in Matlab, and the dynamical responses curves of the mechanism under different elastic modulus were obtained. It can be concluded that the flexible rod had an important influence on the output characteristics of the mechanism. The smaller the elastic modulus was, the greater the influence on the mechanism was, and the impact on the acceleration of the moving platform was the most significant. The research can provide a modeling method and idea for other rigid flexible coupling dynamics of other spatial parallel mechanisms, and also can lay a foundation for the dynamic modeling of the mechanism considering joint clearance and flexible rod at the same time.

Abstract:An experiment setup for the contraction force measurements of pneumatic muscles was developed for sake of the pneumatic muscle’s dynamic characteristics. The pneumatic muscle force-displacement hysteresis characteristics were found to be asymmetry, with nonlocal memory, weak correlation of high internal pressure, and quasi rate-independent by investigating the influence of the internal pressure, stroke, contraction velocity, contraction frequency on the pneumatic muscle’s force-displacement. Aiming at the problem that the existing Prandtl-Ishlinskii (PI) model cannot predict force-displacement hysteresis much well, a modified PI+Dead-zone hysteresis model was developed by incorporating a modified dead-zone operator with the classical PI model. The model’s parameters were further estimated by the least square method and the model precision was compared with the classical PI model, the classical Bouc-Wen (BW) model, PI+Polynomial model, Wang-Wen model and BW+Polynomial model. Comparative experiment results showed that the PI type models performed much better than BW model, and the modified PI+Dead-zone model can predict force-displacement hysteresis best with the absolute mean error less than 1N and the mean variance less than 1.5N under each contraction condition. Furthermore, the classical PI model which possessed fewer model parameters can also estimate the force-displacement hysteresis accurately during a short contraction. Above experimental results provided a valid reference for nonlinear control of the PAM actuated servo system.

Abstract:Aiming to meet the energy demand of agriculture micro-type sensor and real-time condition monitoring system, and reduce the pollution of chemical batteries to water and soil, a vortex induced vibration piezoelectric wind harvester was proposed and researched in theory and experiment. The theoretical model of the vortex induced vibration piezoelectric wind harvester was established and the simulation analysis was carried out. The influence of the angle of attack, length of piezoelectric cantilever and wind speed on deformation of piezoelectric cantilever was studied. A prototype of the energy harvester was made and the output voltage of the energy harvester was investigated. The results showed that there were two angles of attack that made the output voltage of the energy harvester larger at each wind speed. The two optimal angles of attack for piezoelectric cantilever lengths of 60mm and 78mm and wind speeds of 7.6m/s, 11.6m/s, and 12.4m/s were (35°,135°), (45°,125°) and (50°,120°) and (35°,120°), (40°,115°) and (45°,110°), respectively. When the angle of attack was 120°, there was an optimal wind speed to maximize the output voltage of the energy harvester. With the increase of length of piezoelectric cantilever, the optimal wind speed was decreased from 12.4m/s to 8.4m/s, and the corresponding maximum output voltage of the energy harvester was increased from 16.6V to 16.8V. When the external resistance was 150kΩ and the wind angle was 30°, the measured maximum output power of the energy harvester was 1mW. Therefore, according to the range of the actual wind speed to determine the reasonable angle of attack and the length of piezoelectric harvester can be helpful for a wind energy harvester to generate more energy.

Abstract:Precision optical mechanical systems are the core component in maneuver detection on land, air and sea as well as in the guidance equipment. The precision assembly of its sensitive axes, such as optical axis, inertial navigation axis and mechanical axis, is one of the key factors affecting the final performance. In order to improve the assembly efficiency and assembly performance, the precision assembly problem of multi-sensitive axes was transformed into the problem of angle variation in the process of cabin assembly by taking a certain type of equipment as a research object and analyzing its assembly characteristics of multi-sensitive axes. The definition and process were introduced detailly, and based on those, the accumulation model of angle variation was established and the relation between machining error and distribution of angle variation was derived, which can be used to analyze the assembly accuracy in the process of assembling the multi-sensitive axes. Finally, based on the established model, the direct docking method, which was mostly used in the assembly of cabin nowadays, was simulated and analyzed, and the simulation results revealed the reason of the one-time qualified rate was very low in the assembly of the certain object. It was that the assembly direction of the cabin was completely random and there was no optimization in the assembly process. Inspired by this, a kind of process optimization assembly method by adjusting the matching direction was proposed, and the precision assembly process of multi-sensitive axes was optimized. The simulation results show that comparing with the direct docking method, the proposed method can effectively ensure the assembly accuracy between the sensitive axes.