Research On Active Suspension System Control Of Hub Driven Electric Vehicle

Electric vehicles(VEs)provide many advantages over the fuel vehicle in terms of energy efficiency and environmental friendliness.They play a key role in improving air quality and reducing CO₂ emission.Hub-driven electric vehicles,in which the driving motors are integrated into the wheels directly,have attracted the increasing research interest in recent years due to their high efficiency in power transmission,fast and precise torque control as well as easy integration with traction control systems.However,due to the increase of unsprung mass and the unbalanced force of the motor,the ride comfort and road holding capability of suspension are seriously affected.The unbalanced electromagnetic force,road interference and their coupling effect strengthen the unbalanced electromagnetic force interference,aggravating the coupling effect in the hub motor,deteriorating the NVH performance.The active suspension has excellent damping performance,which can effectively suppress the combined action of the road roughness and unbalanced electromagnetic.It has a great application prospect in electric vehicles.However,in the research of active suspension control for hub-driven electric vehicles,the dynamic interference of unbalanced electromagnetic force and the negative coupling effect caused by it are not considered.This thesis takes the active suspension control of hub drive electric vehicle based on permanent magnet synchronous motor as the research object and investigates the control strategy of active suspension and its influence on the electric vehicle performance.The main works are given as follows:(1)The coupling quarter suspension model of the hub-driven electric vehicle reflecting the dynamic coupling between the hub motor electromagnetic excitation and the electric vehicle vertical vibration is proposed.The influence of the road surface roughness,phases current of IWM,vehicle speed and the airgap eccentricity on the unbalanced electromagnetic force is analyzed and the mechanism of coupling effect is investigated.In order to restrain the coupling negative effect and improve the comfort,the H₂/H_?controller of the active suspension of the hub-driven electric vehicle is designed.The intelligent optimization algorithm is used to optimize it,which balances the ride comfort and the coupling effect in the hub motor,improving the performance of the whole vehicle.(2)Based on the Lyapunov stability theory,a fault-tolerant control controller of the active suspension system for the hub-driven electric vehicle is designed considering the actutor fault system,parameter perturbation and the five aspects of the active suspension system performance.The influence of actuator failure and model uncertainty on the electromagnetic coupling effect of the hub motor,ride comfort and road holding ability is explored.Through the comparative analysis,it is verified that the controller has good control performance under the system parameter perturbation,the actuator force failure and serious electromagnetic force interference.(3)Considering the ride comfort,road holding capability,electromagnetic coupling effect of hub motor and other suspension performance requirements,using delay-dependent Lyapunov function,the existence conditions of delay-dependent robust controllers are derived.Then,by the hybrid algorithm of particle swarm optimization algorithm and linear matrix inequality optimization algorithm,the bilinear matrix inequality constrained optimization problem of the delay-dependent controller is solved.The influence of time delay on the ride comfort of EV and the coupling effect of the hub motor is analyzed.The superiority of the delay-dependent controller for the active suspension system of the hub-driven electric vehicle is verified.(4)The electromagnetic active suspension actuator model and its vector control model are established.Combined with the multi-field coupling suspension model and outer loop robust suspension controller,the double closed loop control model of the active suspension system of the hub-driven electric vehicle is designed.The influence of the electromagnetic actuator control algorithm and the actuator nonlinear friction on the suspension performance and the hub motor multi-field coupling effect is studied.(5)In order to comprehensively reflect the hub motor coupling characteristics and the vehicle vibration characteristics under the active suspension control,the half vehicle suspension model with six-degree freedom of the hub-driven electric vehicle is established.Combined with the multi-field coupling suspension model and the electromagnetic actuator control model,a half-vehicle electromagnetic active suspension coupling system of the hub-driven electric vehicle is established.On this basis,the robust preview control strategy of the suspension of the wheel drive electric vehicle is designed,and its effectiveness is verified.