Research On Path Tracking Control Of Differential Steering Unmanned Vehicle

At present,research on autonomous driving of unmanned vehicles is mostly based on active steering technology,and there is less research in the field of differential steering.Differential steering unmanned vehicles mainly rely on hub motors to provide driving force,and their transmission system structure is simpler than traditional mechanical transmission.The torque of each driving wheel can be controlled separately,and the transmission efficiency is also higher.Due to the independent control of each wheel hub motor,the difference in output torque between the two wheel hub motors can be utilized to generate a torque difference.At this point,the unmanned vehicle will turn towards the side with less torque,which is called differential steering.Therefore,this article focuses on the research of autonomous driving path tracking control for differential steering unmanned vehicles.The main work content and conclusions of the paper are as follows:(1)In the Vehicle dynamics simulation software Carsim,set the vehicle body model,power system,suspension system and input/output interface,extract relevant vehicle parameters,and establish a linear two degree of freedom vehicle model to verify the correctness of parameter extraction.After selecting and verifying the hub motor,a simulation model of the hub motor and a speed control simulation module were built in Matlab/Simulink.At this point,the establishment of a simulation model for the autonomous vehicle driven by a hub motor has been completed.(2)Introducing the fractional calculus theory,based on the single point preview driver model,the fractional order single point preview driver model was established by simulating the driver’s driving behavior through the inherent weight characteristics and memory characteristics of the fractional order integration.The path tracking effect of the fractional order single point preview driver model was verified through the comparison of logistic single shift route path and single point preview driver model,Obtained the required front wheel angle and vehicle dynamic response for unmanned vehicle tracking path.(3)A dynamic model of the entire vehicle driven by a hub motor and a dynamic model of the front wheel differential steering system have been established.Taking the established linear two degree of freedom vehicle model as the reference model,a front wheel differential steering control strategy was designed using sliding mode control method based on the difference between the actual yaw rate of the differential steering vehicle and the reference model yaw rate.Finally,simulation verification was conducted through single and double lane changing paths,and the results showed that the front wheel differential steering controller can achieve the steering function of unmanned vehicles.(4)The dynamic and Kinematics models of the differential steering unmanned vehicle are established and linearized and Discretization.By setting the objective function and constraint conditions,the optimization problem of the objective function is transformed into a Quadratic programming problem.The calculation of the optimal control quantity and control increment is completed in each control cycle,and the design of the model predictive controller is completed.Finally,simulation verification was conducted through single and double line shifting paths,and the results showed that the control strategy proposed in this paper can enable unmanned vehicles to achieve path tracking through differential steering.