Design And Study On Control Strategy Of Cotton-picking Machine Hydro-mechanical CVT

The hydro-mechanical CVT(HMCVT)is a new type of compound stepless speed changer,which combines the advantages of hydraulic transmission and mechanical transmission.It can realize the continuous adjustment of the speed ratio according to the load and driving speed requirements,and can improve the speed ratio by matching with the engine speed ratio.The fuel economy of the cotton machine.In order to improve the comprehensive performance of the cotton picker walking harvesting transmission system,this paper studies the HMCVT from four aspects: design scheme,changing section strategy,test bench and measurement and control system.For the picking machine,it is easy to appear during the picking operation: the walking speed during the operation of the cotton picker cannot adapt to the change of working conditions,environment,cotton density and driving resistance;the match between the engine of the cotton picker and the gearbox is unreasonable,the shifting process is not stable,the blunt blunt is obvious,and the gearbox cannot run smoothly and reliably at the changing point.Comprehensive analysis of the self-propelled cotton picker on the market,combined with the principle of HMCVT,designed a transmission scheme of HMCVT based on cotton picker.Based on the combination of theoretical analysis,simulation test and test bench research,the transmission characteristics of the hydraulic continuously variable transmission are studied.The simulation model of the transmission transmission system is constructed.The control strategy of the variable speed control process is developed.The software optimizes the segmentation process,builds the hydraulic stepless transmission test bench and the measurement and control system,and carries out the adaptive test of the transmission.The test results show that the working performance meets the requirements of the driving adaptor of the cotton picker.The main contents are as follows:1.Study the transmission speed ratio and torque transmission law of hydro-mechanical continuously variable transmission;combine the characteristics of the engine and the working condition of the cotton picker,design the hmcvt transmission scheme,establish the mathematical model of the hmcvt transmission system,and design its structure and optimization.2.Based on the mathematical model of hmcvt transmission,establish multi-section hmcvt dynamics simulation model(engine,load characteristics,planetary gear train,pump control motor system,clutch and other models),compare fuzzy pid control,gray scale prediction control and neural network Controlling the principle of the three,selecting the current control algorithm suitable for the transmission,verifying the fuzzy pid controller designed in the conditional speed adaptive test,transport speed adaptive test and load adaptive test by hmcvt simulation test Have better adaptability and robustness.3.Based on the HMCVT transmission segmentation characteristics,using MATLAB/simulink dynamic simulation software,through the combination of theory and experiment,the simulation model of the hydraulic continuously variable transmission system is built,and the test bench including the engine,the transmission and the magnetic powder brake is built.Simulate the working conditions of the cotton picker.For the transmission power distribution,working conditions and related hydraulic system parameters,the STM32F407 single-chip microcomputer is used as the HMCVT controller lower-level machine(TCU)processor to provide control signals for the variable pump,clutch and brake action switching,and the HMCVT measurement and control system is designed.Through HMCVT test research,verify the rationality of control strategy and test bed and measurement and control system,analyze the robustness of HMCVT load adaptive control strategy under load change under target speed,and find the optimal combination of controllable parameters.