Study On Control Strategy Of Steering Stability For An Eight In-Wheel Motor Drive Vehicle

In this paper,taken an eight in-wheel-motor drive vehicle with eight independently controllable in-wheel motors and eight independently active steering system as the object of study,a hierarchical adaptive reconfiguration coordinated and integrated stability control(RCSC)is proposed to improve the vehicle steering stability,to achieve the purpose of energy saving under certain conditions.Based on the vehicle dynamics theory and hierarchical control structure theory,coordinated and integrated control of subsystems such as independent drive/brake and independent steering subsystem is carried out.Based on multi-objective function and stability judgement,a self-adaptive strategy of mode switching strategy is proposed.In the hardware in the loop simulation platform,the effectiveness and real-time performance of the steering stability control strategy proposed in this paper are analyzed and verified.Firstly,a dynamic model that reflects the nonlinear characteristics of vehicle is established.The model considers the coupling/nonlinear saturation of tire force and static and dynamic characteristics of suspension.Based on the structure parameters of the original vehicle and the experimental data of the vehicle,the validity and accuracy of the model of the vehicle built by Matlab/Simulink is verified.The vehicle semi-physical hardware in loop real-time simulation platform is built based on the vehicle controller and d SPACE Auto Box real-time simulation system developed by Freescale Carle MC9S12 microcontroller.It provides powerful conditions for verifying the vehicle’s adaptive hierarchical coordination and integration stability control strategy.According to over-driving,nonlinear and constrained characteristics of the eight in-wheel-motor drive vehicle,this paper uses a hierarchical modular structure to solve the nonlinear tire force saturation,execution system of constraint and constraint conditions of ground adhesion.The transient response,steady state response and stability condition of four axle vehicle are analyzed.The dynamic response of three steering mode under zero sideslip angle is analyzed,and the vehicle reference motion state controller is designed based on the all wheel steering with zero side slip angle.The eight in-wheel motor vehicle has characteristics of over-drive,multi-constraints and nonlinearity.In this paper,a hierarchical adaptive reconfiguration coordination integrated stability control strategy is proposed.Aiming at the uncertain and nonlinear characteristics of vehicle motion,a vehicle upper controller is designed based on nonlinear sliding mode control theory to track vehicle reference motion state and obtain vehicle target force/torque.The vehicle has over-drive,multi-constraint features,effective control set algorithm to realize optimal allocation of tire longitudinal force and tire lateral force distribution based on the theory of control allocation,and a multi-objective-function is proposed based on reconfigurable mode switching strategy,improve vehicle stability.Finally,the hardware in the loop hardware simulation test platform is used to verify the effectiveness and real-time performance of the vehicle steering stability control strategy.the hierarchical adaptive reconfiguration coordinated and integrated stability control(RCSC)proposed in this paper show that this control strategy in critical conditions to improve the vehicle steering stability compared with hierarchical control allocation strategy.Based on the stability judgement,the driving mode switching is realized,and the driving motor works in the efficient area to achieve the effect of energy saving.The simulation results also verify the stability of vehicle when the vehicle actuator fails.