Semi-active Suspension Control Under The Consideration Of The Vehicle Body Pitch Dynamics

People often encounter discrete impacts on the pavement,such as pit collapse caused by road damage and speed bumps specially placed in front of some important places,when traveling by c ar.For the discrete impact driving condition,the paper takes the magnetorheological semi-active suspension with larger force adjustment range and higher practical value as the controlled object and construct the controlled model of dynamic coupling between the front and rear axles of the automobile.A control strategy is proposed,which can effectively restrain the vertical and pitch motion of the vehicle and improve the performance of the vehicle under the discrete impact driving condition.This paper establishes a time-domain description model of the discrete shock road profile that can contain both the information space state and the vehicle driving state and analyzes its incentive features,builds the automobile dynamics model with four degrees of freedom that considers the vehicle body pitch dynamics and checks its accuracy of the model.After the above works,the forward and inverse mapping model of the Magnetorheological Damper(MRD)was established based on the hyperbolic tangent reduction function and the dynamic model of the vehicle MRD semi-active suspension system is completed.For the phenomenon that the vehicle has poor ride performance due to the vertical and pitching motion of the vehicle under the discrete impact driving conditions,the research on the control strategy of the LQR semi-active suspension is carried out,and the objective function that can characterize the overall performance of the vehicle is proposed,and the specific mathematical description form of the objective function of the controller is determined according to the control objective to be achieved by the controller,the specific mathematical description form of the performance evaluation method is determined,and then based on the established vehicle suspension dynamics model,the optimal full-states feedback controller that can effectively restrain the vertical and pitching motion of the vehicle under this driving condition is designed.In order to further improve the control performance of the controller by adjusting the control weight,the particle swarm mathematical optimization algorithm(PSO)is used to optimize the control weight in the performance evaluation mathematical model,which reduces the repeated adjustment of the control weight and completes the adjustment.The controller is further optimized,and then the control performance of the controller before and after the optimization is compared and analyzed by simulation,and the optimization effect is evaluated.The optimal full-states feedback suspension controller requires relatively high measurement technology and needs to observe all the response states of the vehicle.According to the current vehicle-mounted sensor measurement technology,it is impossible to observe the vertical speed of the vehicle body and the wheels and the dynamic displacement of the tires.Therefore,it has great limitations in practical engineering applications.In response to this problem,this paper designs the optimal output feedback suspension controller that takes the vehicle-mounted sensor observable measurement as the output variable based on the optimal full-states feedback suspension controller.The results show that the control performance of the optimal output feedback suspension controller is very close to the optimal full-state feedback controller,but it is greatly expanded the engineering application of the control algorithm.