Research On Slip Ratio Control For Electric High-clearance Vehicle

Compared with the automobile,the working environment of the agricultural operation wheeled machinery is more complicated and the road parameters are changed.So the drive and control is more complicated.The working environment is cultivating for high-clearance vehicle.The wheels walk among rows of plants.To ensure its ability to be protected against excessive slip.The slip rate must be controlled.As far as the current research is concerned,the four wheel independent drive vehicles generally use the threshold control method.Rough classification of the road surface,however,it will lead to the vehicle cannot ensure the best control effect of slip in a variety of conditions.Aiming at the problem,the peak adhesion coefficient of road surface is estimated by experiments in this paper.The estimated peak adhesion coefficient is used to estimate the target slip rate of the wheel to ensure the stability of the high ground clearance vehicle during operation.The main research results and conclusions of this paper are as follows:(1)Adhesion coefficient estimation theory.It based on theoretical analysis.The tire elasticity and dynamics of ground are analyzed.It is assumed to be rigid tire tires and wheels and the establishment of a road by the force model.According to the model,through the sliding mode algorithm tire force were observed.Obtained observation tire force model,we propose two options:the recursive least squares method and the simplified formula,adhesion coefficient were estimate respectively to obtain road peak adhesion coefficient and the corresponding slip rate.(2)Hardware circuit and software design.It introduces the hardware and circuitry,including a controller circuit,actuator circuit and sensor circuit.Furthermore,the PLC programming,GPS acquisition programming and configuration program were introduced.To make sure that hardware can transmit data to each other via software.(3)Designed to drive the control strategy.First,it begin the control of global design.According to the second chapter adhesion coefficient estimated by threshold control the road condition of the vehicle,respectively,and upon reaching the drive control request.It start using the drive control program.Wherein the drive control program mainly includes based on variable structure control and control based on incremental PI.It improves vehicle stability on the homogenous pavement and separation pavement.(4)Actual road driving control tests.The actual road surface including:homogenous road surface,the separation surface.Actual road tests include:Unused control strategies,using sliding mode control strategy,the use of incremental PI control strategy.By using the estimated road friction coefficient,respectively,using three control methods on two kinds of road test.In order to test of its slip rate,the driving force,the vehicle speed,straight running ability.As can be seen from the results of that control strategy can effectively stabilize the wheel slip rate.Sliding mode control takes the effect of volatile while approaches to the target value.The incremental PI control is stable but 1-3%deviation from the target value.On separation pavement,sliding mode control is superior to incremental PI control.