Design And Research On Hydraulic Chassis Transmission System Of Orchard Picking Platform

Currently,the orchard planting industry is developing rapidly,and the efficiency of mechanized orchard harvesting operations needs to be improved urgently.The existing orchard harvesting platforms in China generally use mechanical and hydraulic transmission,which has problems such as low energy utilization,high prices,and inconvenience in maintenance.In order to solve the above problems,it is of great significance to develop and design a hydraulic transmission orchard picking operation platform.The fully hydraulic self-propelled orchard picking operation platform is mainly designed for all-round fruit picking in orchards,which can better assist fruit farmers in completing the picking and collection work.According to the technical indicators of the orchard picking operation platform,this paper designs a hydraulic transmission system,establishes mathematical models of the walking system and steering system,builds a simulation model,and verifies its rationality.Considering the possibility of wheel slip,a fuzzy auto disturbance rejection control is designed to adjust the motor displacement,control the wheel speed,and achieve anti-skid effect.The main research contents are as follows:(1)The hydraulic transmission system of the orchard picking platform chassis was designed.The traveling circuit,cooling circuit,and steering circuit are designed respectively,and constitute the overall circuit of the hydraulic transmission system;Calculate the parameters of the hydraulic pump,hydraulic motor,and steering hydraulic cylinder based on the mechanical meter to ensure the rationality of the design;Design a walking hydraulic transmission scheme with a single quantitative pump and a four variable motor,a closed volume speed regulating circuit,and a steering system with two wheel steering and four wheel steering switchable,and arrange the overall transmission system.(2)Build a hydraulic transmission system model of the orchard picking platform chassis.Mathematical modeling was conducted for the hydraulic pump,hydraulic motor,diverter and collector valve,flushing valve,and steering hydraulic cylinder in the steering system.Then,a complete hydraulic transmission system was built based on AMESim,and the built transmission system was verified.Simulation was conducted for the starting,climbing,steering,and straight travel conditions on hard soil and gravel roads,and it was obtained that the walking system can smoothly travel on these two types of roads,The maximum gradient for two wheel drive is 24 °,and the maximum gradient for four wheel drive is 33 °.The maximum steering angle for the steering system for two wheel steering is 36 °,and the minimum turning radius is 3.5m.The maximum steering angle for four wheel steering is 43 °,and the minimum turning radius is 3m,which can assist the walking system in driving through the S-shaped curve normally.(3)A fuzzy auto disturbance rejection control strategy for wheel anti skid of orchard picking platform was designed.The transfer function of a walking hydraulic system composed of a fixed displacement pump and a variable displacement motor is derived,and the disturbance is analyzed as an internal variable of the variable displacement motor.An expanded state observer is designed to observe the motor speed and rotational speed error;Designing nonlinear feedback to compensate for system disturbances;A differential tracker was designed to solve the problem of overshoot and rapid response of the walking system during motor speed adjustment.Three modules were connected to form a complete auto disturbance rejection controller.Combined with the operation of the orchard picking platform on different roads,joint simulations were conducted to verify the road surface adhesion coefficient of 0.4,0.2,and wheel suspension conditions,with the motor speed and wheel slip rate as evaluation indicators,Analysis shows that the auto disturbance rejection controller has a poor control effect on the motor speed when the coefficient of adhesion is 0.2 and the wheels are in suspension,and the slip rate after control is still 0.2 when the wheels are in suspension,which does not provide effective anti-skid control.Therefore,fuzzy control is added to the original controller to achieve dynamic adjustment in the expanded state observer,forming a fuzzy auto disturbance rejection controller,The simulation of 0.2 and wheel suspension conditions is conducted again and compared with the auto disturbance rejection controller.The results show that the fuzzy auto disturbance rejection controller can improve the control speed and stably control the wheel slip rate within 0.05.