Research On Active Rear Steering Control Strategy And Its Test

Active steering is an effective means to effectively improve vehicle handling stability and active safety,and is a trend in the future.This paper focuses on the active rear steering control strategy and testing,mainly aimed at the urgent needs of the automotive industry,breaking through the foreign technology blockade,and further promoting and popularizing the active rear wheel steering system.Firstly,the 2DOF dynamics liner models of FWS vehicles and 4WS vehicles are established respectively.The transfer functions of yaw angular velocity and lateral acceleration are deduced.The steady-state characteristics of 4WS vehicles are theoretically analyzed and the basic nature of vehicle movement is understood.Then through analysis,it is determined that the control target of the system is “the sideslip angle is zero”,and the characteristics of the control target are explained from the geometric point of view around the steering process of the vehicle.At the same time,an LQR optimal control method based on variable weight coefficient is proposed.Simulation experiments were designed and compared with FWS vehicles and 4WS proportional steering vehicles.The simulation results show that 4WS improves the stability and active safety of the vehicle,but it also has the problem of reducing the yaw rate and the lateral acceleration gain during the steering process.In addition,the results show that the optimal control method based on LQR has a significant control effect on the target,and can achieve the control target well under different working conditions.Secondly,the commonly used methods for estimating the sideslip angle are studied.Then,based on the Uni-Tire tire model and the nonlinear vehicle dynamics model,a method for estimating the sideslip angle using a nonlinear full-dimensional state observer is proposed.At the same time,combined with the tire data provided in Carsim,the unknown parameters in the tire model were identified by the ‘curve fitting' tool in the Matlab optimization toolbox.Finally,the effectiveness of the estimation method is verified by simulation experiments.The results show that the control method has high estimation accuracy and has practical value.Then,the hardware and software involved in the system development process are introduced.The rear wheel steering system actuator uses the rear wheel steering gear of the Cadillac CT6.In order to control the actuator,the stroke sensor on the steering gear and the controller of the permanent magnet synchronous motor were redesigned.The article introduced the design process in detail,and explained the drawing requirements of the PCB board.Secondly,the task design method based on infinite loop is introduced,and the specific architecture of the system software is explained,as well as the model-based automatic code generation technology and the single-chip related block development technology.In addition,the entire set of debugging tools for system development is explained,including code generation,program compilation,program download,and signal monitoring.In addition,the experimental gantry of the steering gear motor was designed,and the three-closed-loop motor position following control method was developed,and the control of the actuator was successfully realized.At the same time,the actual effect of the motor control method was verified by sending a sinusoidal position command and a given constant load on the steering gantry of an enterprise.Finally,the hardware-in-the-loop experimental bench was built,and the hardware composition of the experimental bench,joint simulation setup for SCANeR,Carsim,Matlab/Simulink software and communication mechanism were explained.At the same time,the relevant experimental conditions were designed,and the system control strategy was verified.The experimental results were consistent with the simulation results.The experimental results are in agreement with the simulation results.Due to the communication delay in the lab bench,the motor control did not perform joint testing.Meanwhile,the advantages and disadvantages of the control strategy proposed in this paper,as well as the direction of improvement,are explained.