Research On Coordinated Control Of Vehicle Active Steering And Electric Power Steering System

With the mature and widespread use of the Electric Power Steering System(EPS)system,Active Steering System has gradually entered the public view.Active steering provides better control methods and performance for vehicle control and stability control,and provides possibilities for the development and realization of automatic driving,automatic obstacle avoidance and automatic navigation technologies in the future.The EPS system is used to change the torque transmission characteristics of the steering system,but it cannot change the angular displacement characteristics of the steering system.The Active Front Steering(AFS)system uses a set of planetary gear change ratio devices based on the steering angle input from the driver's steering wheel to apply additional steering intervention,which not only optimizes vehicle response to driver input.,And can improve the stability of the vehicle in emergency conditions.The EPS and AFS combined steering system can effectively change the angular displacement and force transmission characteristics of the steering system,and better realize the coordinated control of the "light" and "spirit" of the car steering.It is the development direction of the future automobile steering system.In a vehicle equipped with an EPS and AFS combined steering system,when the AFS system is in operation,the variable transmission ratio actuator will change the transmission ratio of the steering system.At this time,the auxiliary rotation angle motor needs to overcome the steering resistance torque change caused by the additional rotation angle intervention.Due to the torque transmission characteristics of the planetary gear train,the amount of change in the steering resistance torque overcome by the assisting angle motor is transmitted to the steering wheel,which is perceived by the driver and is characterized by a steering wheel sudden change torque.The steering wheel abrupt moment caused by AFS additional corner intervention will aggravate the driver's nervousness,and it is easy for the driver to produce misoperation,which is not conducive to driving safety.In this paper,EPS and AFS system models are established based on Simulink.CarSim commercial software is selected for the vehicle model to build a Simulink and CarSim co-simulation platform.In terms of EPS control strategies,the research group has studied for many years and achieved certain research results.For the AFS system,this paper will estimate the road surface adhesion coefficient based on the positive tire returning moment,and adopt the model predictive control theory to realize the tracking control of the yaw rate of different surface adhesion coefficients.In the research of coordinated control of EPS and AFS,an active steering actuator based on the output of the ring gear is designed to analyze the causes of the abrupt moment of the steering wheel,and an abrupt torque compensation controller for the steering wheel is designed using the EPS system.Finally,through the built Simulink and CarSim co-simulation platform,the control strategy of the design is verified by simulation test.