Design and experiment of corn low damage threshing device based on DEM

Kernel broken rate is an important index to evaluate the maize kernel direct harvesting quality.In view of the problem of the high kernel broken rate in the present maize harvester,a new threshing cylinder was designed in this study.This device utilized rasp bar to achieve low damaged maize ears threshing.In order to determine the structure and working parameters of threshing device,the“crop-crop”contact model and the“crop-mechanical”interaction system were established and analyzed based on the discrete element method first,and the mathematical expressions of the related kinematic response of maize kernel under the external force were obtained.Then,the structure parameters of rasp bar were studied through EDEM simulation experiment,and the working parameters were determined through test-bed experiment.Finally,the simulation experiment results and test-bed experiment results were verified through field experiment.The results showed that when the threshing cylinder speed was 356 r/min,the concave clearance was 40 mm,the installation distance of rasp bar was 250 mm with 50Mn steel,and the feeding amount was 8 kg/s,the kernel broken rate was 1.93%,which satisfied the requirements of maize harvest standard.This study proved that the DEM(Discrete Element Method)can be adopted to guide the optimization design of mechanical structure,and it has certain value for the research and development of operation equipment of other agricultural crops.

Image moments-based visual servoing control of bagged agricultural materials handling robot

Manual handling is less efficient and sometimes even hazardous to humans in many areas,for example,agriculture.Using robots in those areas not only avoids human contact with such dangerous agricultural materials but also improves working efficiency.The motion of a robot is controlled using a technique called visual servoing that uses feedback information extracted from a vision sensor.In this study,a visual servoing method was proposed based on learning features and image moments for 3D targets to solve the problem of image moment-based visual servoing.A Gaussian process regression model was used to map the relationship between the image moment invariants and the rotational angles around the X-and Y-axes of the camera frame(denoted asγandβ).To obtain maximal decoupled structure and minimal nonlinearities of the image Jacobian matrix,it was assumed two image moment features,which are linearly proportional toγandβ.In addition to the other four standardized image moment features,a 6-DOF image moment-based visual servoing controller for the agricultural material handling robot was designed.Using this method,the problem of visual servoing task failure due to the singularity of the Jacobian matrix was solved,and it also had a better convergence effect for the part of the target image beyond the field of view and large displacement visual servoing system.The proposed algorithm was validated by carrying out experiments tracking bagged flour in a six-degree-of-freedom robotic system.The final displacement positioning accuracy reached the millimeter level and the direction angle positioning accuracy reached the level of 0.1°.The method still has a certain convergence effect when the target image is beyond the field of view.The experimental results have been presented to show the adequate behavior of the presented approach in robot handling operations.It provides reference for the application of visual servoing technology in the field of agricultural robots and has important theoretical significance and practical value.

Powertrain parameter matching and optimal design of dual-motor driven electric tractor

The rationality of powertrain parameter design has a significant influence on the traction performance and economic performance of electric tractor.At present,researches on powertrain parameter design mainly focus on electric vehicles,and electric agricultural machinery draw much less attention.Therefore,a method of powertrain parameter matching and optimization design for electric tractor was proposed in this paper,which was based on dual-motor coupling drive mode.The particle swarm optimization(PSO)algorithm based on mixed penalty function was used for parameter optimization.Parameter optimization design was programmed using MATLAB.A simulation dynamic model with optimization design variables of electric tractor powertrain was established based on MATLAB/Simulink.Compared with the simulation results before optimization,the objective functions were optimized and the traction performance of electric tractor was improved,which indicated the effectiveness of the proposed method.

Height stability control of a large sprayer body based on air suspension using the sliding mode approach

When a high clearance self-propelled sprayer sprays,the sprung mass varies with the amount of liquid in the tank,which causes a change in the height of the sprayer body.This change not only is harmful to the sprayer ride comfort,but also has a greater impact on the sprayer application quality.In this paper,a large-scale high clearance self-propelled sprayer with air suspension was taken as the research object.Based on vehicle dynamics and air thermodynamics theory,a mathematical model of air spring inflation/deflation was established,then a 3 degree of freedom(3-dof)vertical dynamics model of sprayer air suspension was built.On this basis,the height control strategy of the sprayer body was formulated.Due to the nonlinear characteristics of air suspension,two control algorithms,namely sliding mode control and the on-off control,were used to design the suspension height stability controller,respectively.A simulation experiment was carried out by using the sprayer spraying crops as an example.The simulation experiment results showed that sliding mode control and on-off control could track and stabilize the height of the sprayer body when it changed under no excitation and D-grade road random excitation.However,due to strong nonlinearity and hysteresis of the pneumatic system,on-off control precision was poor.With the on-off control method,further reduction of the sprung mass would change the internal parameters of the pneumatic system,cause the air spring over deflation,even worse,the over deflation phenomenon presented a serious trend and cause system instability under random road excitation.Compared with on-off control method,sliding mode control approach had good control ability and precision due to its robustness to change in model parameters.The research will provide a reference for the height stability adjustment of large high clearance self-propelled sprayers during spraying and dosing operations.

Design and experiment of a high-clearance self-propelled sprayer chassis

A large high-clearance self-propelled sprayer chassis was designed according to the requirements of the sprayer’s driving operation and the overall goal.The structural characteristics and working principle of the chassis drive system,suspension system,track adjustment system,and frame were analyzed.A finite element analysis of the frame was carried out under four extreme conditions:full load bending,full load torsion,full load emergency braking and full load emergency turning.Under these four conditions,the maximum stress values of the frame were 149.45 MPa,219 MPa,151.44 MPa,and 123.27 MPa respectively,and the maximum strain values were 1.12 mm,2.22 mm,0.95 mm,and 1.16 mm respectively.A theoretical analysis of the stability,steering ability,and obstacle navigation of the sprayer chassis was conducted.The results showed that the upper angleθlim,lower angleθ׳lim and lateral limit tumbling angleφlim of the sprayer chassis were 50.1°,30.0°and 35.3°respectively.The minimum turning radius of the chassis was 5816 mm,and the minimum turning width was 4113 mm.The maximum obstacle crossing heights of the front and rear wheels were 466 mm and 457 mm.The theoretical analysis showed that the designed chassis met the field management operations of large plots.A field experiment of the high-clearance self-propelled sprayer chassis at full load was conducted.The experimental results were consistent with the theoretical analysis results.The sprayer chassis not only good handling stability but also good ride comfort.The results of this study provide references for the design of high-clearance self-propelled sprayer chassis.

Tractor path tracking control based on binocular vision

In the process of field operation management,determining how to accurately realize crop row identification and path tracking control is an essential part of tractor automatic navigation.According to the linear operation in the process of cotton field management,the tractor path tracking control system was designed based on binocular vision and the pure pursuit model.A new crop row detection method based on the Census transform and the PID control algorithm with dead zone were used.First,the upper computer software was developed by C++with the functions of parameter setting and image acquisition and processing.Second,an automatic steering controller was developed based on microprocessor MC9S12XS128 of Freescale.The control program was developed based on modular design using CodeWarrior during development of the PID-based automatic steering control strategy.Finally,a field experiment platform of tractor path tracking control was built,and field experiments under the actual cotton were conducted.The optimal visibility distance was determined by several previous experiments.When the tractor tracks the path with the optimal visibility distance in the growth environment of actual cotton crops,the mean absolute deviation of course angle was 0.95°,and the standard deviation was 1.26°;the mean absolute deviation of lateral position was 4.00 cm,and the standard deviation was 4.97 cm;the mean absolute deviation of front wheel angle was 2.99°,and the standard deviation was 3.67°.The experimental results show that(1)the crop row detection method based on Census transform can identify the crop line and plan the navigation path well,and(2)the tractor path tracking control system based on binocular vision has good stability and high control precision;thus,the control systemcan realize the automatic path tracking control of cotton line operation and meets the agricultural requirements of cotton field operation management.

Effect of nitrogen and extraction method on algae lipid yield

Effects of nitrogen source and concentration as well as lipid extraction method on the lipid yield of autotrophic Scenedesmus dimorphus and heterotrophic Chlorella protothecoides were studied.Three concentration levels of nitrate,urea and glycine/yeast extract as the nitrogen source were investigated.The highest lipid yield of S.dimorphus in the 17-d autotrophic culture was 0.40 g/L from the 1.8 g/L urea medium,and the maximum lipid yield of C.protothecoides in the nine-day heterotrophic culture was 5.89 g/L from the 2.4 g/L nitrate medium.Four different cell disruption methods-bead-beater,French press,sonication and wet milling-were studied for their effectiveness in solvent extraction of algal lipids from S.dimorphus and C.protothecoides.Wet milling followed by hexane extraction was most effective for S.dimorphus lipid extraction,whereas bead-beater disruption followed by hexane extraction was best for C.protothecoides.

Factorial significance on tractor stability under variation of terrain roughness employing the Taguchi method

Tractor rollover accidents remain an issue with the development of agricultural mechanization.Adopting the scale-model-based experimental approach,this study investigated the three most influential geometric factors of tractor in various agricultural ground conditions with improved configuration of force sensing system.The initiation of tractor rollover,associated with the tire-ground contact status,was investigated for various front tire types,ballast weights,and rear track widths.Employing the Taguchi method,the ground reaction forces applied to the tractor’s uphill wheels were measured and evaluated using stability indicators.By taking this approach,the effects and statistical significance of the three factors and their interactions were examined under various agricultural ground conditions.Results showed that the ballast weight significantly affected the ground contact status of the uphill front tire.The significance of the front tire type gradually increased as the road roughness increased,but dramatically decreased for an extremely rough road surface.Furthermore,none of the factors or interactions,except the factor of the rear track width for relatively rough roads,was statistically significant.The study revealed that not all commonly discussed factors consistently affect tractor stability.The results of the present study are thus expected to provide a reference explaining how to explore the necessity and feasibility of parameter adjustment before reconfiguring a tractor for higher stability.