Study On The Stability Of Heavy Vehicles Based On Active Suspension And Multi-Axle Steering

Three-axle heavy rescue vehicles are the main rescue vehicles in response to sudden land disasters.In order to ensure the safety of vehicles on complex road sections,vehicles have higher requirements in vehicle stability.Therefore,it is of great significance and practical application value to study improving the driving stability of three-axle heavy rescue vehicles with active suspension.In this paper,LQR optimal control is adopted for active suspension and model predictive control is adopted for steering system,which is combined with the trajectory manifold to carry out coordinated control based on stability margin to improve vehicle driving stability.Firstly,the pavement frequency domain model and pavement time domain model are analyzed respectively.Considering the delay and delay of the three-axle heavy vehicle tire,the stochastic pavement time domain model is established to provide the simulation conditions of the vehicle driving on the pavement under various working conditions.Based on the motion equation of the vehicle,a nine-degree of freedom model of the active suspension of the three-axis vehicle is established considering pitch,roll and vertical center of mass,and the LQR optimal controller of the active suspension system is designed.Secondly,a two-degree-of-freedom linear model of the vehicle is established,and its transient response and steady-state response are obtained through simulation and analysis,so that the all-wheel steering could better control the motion attitude,and the steering proportional coefficient of the three-axis vehicle is derived.The semi-empirical model of tire is established to build a more accurate nonlinear vehicle model.Thirdly,according to the established vehicle model combined with the tire force formula,the lateral declination Angle of the vehicle centroid-lateral declination velocity phase plane is drawn,and the stability region of the phase plane was analyzed according to the phase trajectory manifold of the phase diagram surface.Next,the MATLAB/Simulink model of fuzzy control and model predictive control of vehicle steering is established to simulate the steering conditions.Through the simulation,it is found that the model predictive control improved the dynamic performance of the vehicle,and the coordination controller based on variable margin is designed.Finally,the test results show that the root-mean-square of yaw velocity decreases 11.90% and 13.42% when the vehicle is under left and right steering under coordinated control alone.Body side Angle root mean square decreases 19.85% and 14.74%;The root mean square of the lateral Angle acceleration decreases 21.37% and 15.16%.It is obvious that the phase diagram curve under coordinated control is more convergent to the origin than the phase diagram curve under separate control,indicating that the stability of heavy vehicles with three axes in the driving process has been effectively improved.