Research On Vehicle Chassis Coordinated Control For Safety And Comfort

Vehicle chassis control presents a profound significance on ensuring the vehicle safe-ty and comfort performance.This dissertation has focused on a series of researches from single systems,to their coordinated control,then to the integrated control for the vehicle chassis systems.The detailed research contents are as follows:In the braking process of a vehicle,the wheel lock could elongate the braking dis-tance and even disable the vehicle steering ability,which creates an extremely dangerous working condition.Therefore,it is vital to analysis the anti-lock braking system(AB-S)system.But,the currently tough issues in the ABS research are:1)the necessity of introducing an extremely complex tire-road friction model(?-?curve),2)the priori knowledge of road friction conditions,which make the designed ABS controller rather complex.In chapter 2 of this thesis,the two-time-scale ABS control method is proposed,in which the tire-road friction model is quickly estimated through the two-time-scale re-design,avoiding the introduction of the complex?-?model,and finally realizing the high-precision tracking to the reference slip ratio,consequently ensure the adhesion per-formance between tire and road in a vehicle braking process.The proposed two-time-scale ABS controller is simple in structure,only needs to adjust 2 controller parameters,and does not need the prior knowledge of road conditions,making it easy to apply in engi-neering.The Car Sim simulation verifies the proposed two-time scale ABS control method can prevent the wheel from locking and achieve better braking safety performance.ABS system could shorten the braking distance and hold the vehicle'steering sta-bility,thus improving the longitudinal active safety performance of vehicles.However the majority of traffic accidents occur due to the loss of lateral stability of vehicles dur-ing steering.In chapter 3,the research work on lateral stability system is carried out.The vehicle yaw stability control(YSC)based on?_?gain scheduling is proposed to solve the vehicle lateral stability control problem under the vehicle parameter perturba-tions resulting from the fuel consumption and load variation,and accordingly enhance the adaptability of the vehicle lateral stability control system.The Car Sim simulation verifies the proposed yaw stability control can ensure the vehicle lateral stability and achieve a preferable path tracking results on the circumstance of parameter perturbation.Apart from the basic guarantee of safety performance,the ride comfort of a vehicle is also of significance.However,the safety performance and ride comfort performance of a vehicle are affected and conflicted with each other to some extent.In order to balance the safety performance and the ride comfort performance,chapter 4 focuses on the coor-dinated control between active suspension system(ASS)and ABS.Through the analysis of the coupling relationship between vehicle longitudinal movement and vertical move-ment,the coordinated control method between ASS and ABS based on backstepping is established to improve the longitudinal braking performance and vertical ride comfort performance at the same time.Chapter 5 focuses on the coordinated control of ASS and YSC system.Based on the established vehicle dynamics model containing the coupling of yaw motion and vertical motion,the coordinated method between ASS and YSC is pro-posed,and thereby simultaneously improve the lateral stability and vertical ride comfort performance.The coordinated control of vehicle chassis systems can balance the conflict between safety and comfort performance.However,in order to realize the performance optimiza-tion and global regulation,the integrated control strategy is feasible.Aiming at the active safety of vehicles under critical working conditions,chapter 6 has designed the integrated control scheme of four-wheel independent X-by-wire vehicles.Different from the bottom-to-top control strategy of traditional vehicles,the integrated control for X-by-wire vehicles realizes the top-to-bottom control by directly controlling the wheel effectors according to the reference signal,and accordingly eliminates the conflict between active safety sys-tems.Different simulation working conditions verifies that the integrated control strategy could simultaneously regulate the vehicle longitudinal,lateral,and yaw motion,and ac-cordingly ensure the safety performance in a vehicle motion.