Design And Experiment Of Fruit Picking Robot Mobile Platform

Fruit and its products is a key coponent of China's agricultural export products,With the optimization of the cultivation process and improving of mechanization degree,the fruit production increased year by year,variety structure and continue to improve,it is expected in 2016 will reach 270 million tons.Many countries have increased the research of intelligent machinery,Agricultural machinery with traditional impression of being plain,large,and different,it is moving towards the direction of intelligent,industrial development.As the foundation of the picking robot,the structure intensity and motion precision of the mobile platform directly determine whether the robot can work smoothly,and the research of the mobile platform is more and more important.This project aims to develop and design a compact structure,rational layout,economic security mobile platform on the basis of the domestic and foreign related research and practical orchard working environment to establish foundation for the autonomous navigation,intelligent picking and online grading.The main contents include the following aspects:1.The design of the mechanical body of the mobile platform was completed,the design targets and requirements was formulated.The wheel configuration scheme,the type and the driving mode of the wheel were determined,the steering mechanism and the anti-collision beam mechanism were also designed.2.The analysis of finite element statics of mobile platform was achieved by three kinds of deformation of frame under different working conditions being analyzed.The simplified frame model was imported into ANSYS software,after pretreatment process about the setting of material parameters,selection of unit type and grid division.Equivalent stress nephogram and the equivalent displacement nephogram of mobile platform in the pure bending?combined bending and torsion?picking motion conditions were obtained.The results showed that in the three conditions,the maximum deformation of the frame was 44.0 mm,the maximum stress was 209 MPa,it was less than the yield limit of material at 510 MPa and there were a lot of optimization space to structural strength.Stress concentrated in the edge angle of the frame and mechanical arm connection point.In the actual processing,these regional should be reinforced to ensure the overall bending and twisting resistant capability.3.The inherent mode of the mobile platform frame was solved to avoid the resonance caused by the sensitive external excitation.The first to twelve order vibration frequencies and the mode shapes of the frame were obtained after the treatment,such as modeling?external pre-stress loading,solving,and so on.According to the frequency distribution of external incentives that the mobile platform in the actual work acted could draw the final conclusion:the frame structure design was reasonable,bypassing the sensitivity interval,the resonance would not happen in the actual work.4.The selection of motors and its transient process simulation in the MATLAB/Simulink module was completed and compared with the most common two method that maximum torque current ratio vector control(MPTA)and Id=0 control.The results showed that:In fruit picking robot mobile platform special working environment,the way that under the MTPA control was better than Id=0 control,it's output torque was bigger,the response was faster and the current was smaller in the condition of same output torque,power consumption was smaller.The comparison of the two typical control methods was simple and intuitive,it's had a certain reference value for the future work.5.The control system of the mobile platform was studied,the hardware block diagram and motion control program of the control system were designed.Based on CAN bus technology to design the open control scheme,selected the suitable position,angle,speed,GPS module and other sensors.According to the mechanical design of the mobile platform,the steering performance test,the sliding rate test and the linear tracking test were designed.Results showed that the sensor acquisition angle and tire actual corner were highly linear relationship with less fluctuation;mobile platform sliding rate were a little large,the optimization work need extra attention in the later period;linear tracking error was 0.41 m,meeting the needs of actual work.