Research On Active Suspension Control Of Three-axle Vehicle Based On Nonlinear Decoupling

The emergency rescue vehicle needs a higher driving maneuver to perform the task of rescuing the wounded,and the actuators of its suspension system are coupled multi-input multi-output nonlinear systems.Any one of the actuator actions may cause the body attitude to change.Affect the ride comfort and handling stability of the vehicle.Therefore,the decoupling control of the suspension system is needed to make the vertical,roll and pitch movements of the vehicle independent of each other,so as to achieve a reasonable distribution of the suspension control force.This article combines the national key research and development plan project "Research on the Key Technology of Special Chassis and Suspension for High Mobility Emergency Rescue Vehicles(including Fire Fighting Vehicles)"(Subject No.2016YFC0802902),with a view to improving vehicle ride comfort and handling stability.The decoupling control of active suspension was studied.Establish the mathematical model of the electro-hydraulic servo control suspension unit,design the PID controller and sliding mode controller of the valve-controlled asymmetric cylinder,and use MATLAB for simulation to improve the dynamic response speed and control accuracy of the actuator.Establish a nine-degree-of-freedom nonlinear dynamic model of the vehicle,and use differential geometry theory to decouple the suspension system to make the vertical,roll,and pitch movements of the vehicle independent,and achieve a reasonable distribution of suspension control force.The control of vehicle suspension system lays a theoretical foundation.The fuzzy PID controller and LQR controller of the vehicle suspension system are designed to control the posture of the decoupled vehicle suspension system.The simulation model of fuzzy PID controller and LQR controller is established in MATLAB to verify the effectiveness of decoupling control and control strategy.A suspension unit tracking experiment was conducted to verify that the designed sliding mode controller has good fast response performance.In order to further verify the rationality and effectiveness of the active suspension decoupling control and control strategy,a prototype unilateral bridge test was carried out.The results show that the vertical vibration acceleration,pitch angle acceleration and active body acceleration of the active suspension before decoupling based on LQR control compared with the passive suspension,the root mean square value were reduced by 22.23%,19.28%,and 24.74%,and after decoupling,they were reduced by 30.3%,26.13%,and 36.17%,respectively.It shows that decoupling control and LQR controller have a significant effect on improving vehicle ride comfort and handling stability.