Research On Cooperative Control Of Ride Comfort And Handling Stability For Three-axle Heavy Vehicle

With the development of highway freight industry,the number of heavy trucks are increasing,and the requirements for its overall quality are also increasing.Ride comfort and handling stability are two important vehicle dynamic property,thus it is necessary to control them for improving the overall quality of vehicle.Semi-active suspension can control vehicle vibration and improve its ride comfort.Steering control and direct yaw moment control can restrain vehicle yaw and rollover and improve its handling stability.However,due to the coupling relationship among suspension system,steering system and drive / brake system,the cooperative control between ride comfort and handling stability should be researched to improve the comprehensive performance of vehicle,which will have important theoretical significance and application prospect.A LQG controller of semi-active suspension is designed based on two degrees of freedom(2-DOF)quarter vehicle model,and the weight coefficients of each indexes in the controller are calculated by Analytic Hierarchy Process(AHP).The superiority of LQG control semi-active suspension is analyzed by comparing with passive suspension and On-Off semi-active suspension.A semi-active suspension model with 8-DOF is established for studying ride comfort control of three-axle heavy vehicle,and its accuracy is verified by comparing with the experimental data.A multiobjective LQG controller is designed by AHP,and some simulation tests have been carried out in MATLAB/ Simulink software.The dynamic characteristics of the front wheel steering vehicle and the all-wheel steering vehicle are compared and analyzed using a linear handling stability model with 2-DOF.The existence condition of the critical speed of the zero centroid side angle for the front wheel steering vehicle is derived and verified.The rollover prediction model,the limit speed prediction model and the limit angle prediction model of the all-wheel steering vehicle are proposed and verified based on the quasi static rollover theory.An all-wheel steering nonlinear vehicle model with 10-DOF is established to study the stability control.The influence of vertical load transfer and wheel slip rate change on tire lateral force are considered.And the tire cornering stiffness of reference model is dynamic reverse estimated by brush tire model.An integrated control strategy of proportional steering control and direct yaw moment control is proposed,and an integrated controller is designed based on Ackerman principle and fuzzy PID control technology,then its effectivness is verified by simulation tests.The relationship between the suspension system and the steering system is analyzed for studying the cooperative control of vehicle ride comfort and handling stability.A cooperative model of ride comfort and handling stability is established by considering the influence of tire dynamic load on vehicle handling stability.The necessity of cooperative control is proved by analysing the difference between cooperative model and handling stability model in complicated random road conditions.Then a comprehensive control strategy of vehicle system is proposed by cooperative principle,and a collaborative controller is designed with the combination between suspension control and stability control,then its effectivness is verified by simulation tests.Research results show that the semi-active suspension has good effectiveness and adaptability due to the LQG controller based on AHP;the integrated controller based on proportional steering control and direct yaw moment control can avoid steering instability of vehicle under different working conditions;the cooperative control between ride comfort and stability makes the vehicle more robust.The model and control strategy presented in this dissertation can provide a theoretical basis for the research of ride comfort and stability control of multi-axle heavy vehicles.