Study On Vehicle Chassis Key Subsystems And Its Integrated Control Strategy

In order to realize more comfortable, convenient manipulation, safe, reliable and human constant pursuit of perfect performance, vehicle has been changed from the early stage of complete mechanical to the current stage of combining variety of disciplines and many new technologies, such as machinery, electronics, materials and control. Its function becomes more and more powerful, and has much higher reliability. Now, it is developing towards comprehensive of multi-objective and direction of intelligent control. The chassis key subsystems such as suspension, braking and steering which related to the ride comfort, safety, handling and stability and its integrated control are become the research hot topic in the field of automobile engineering. Combing with the current research status and the exist problems of vehicle chassis dynamics control, center around the Magnetorheological semi-active suspension, from the view point of theory analysis of vehicle system dynamics in and abroad, this dissertation researched the modeling and integrated control of Magneto-Rheological (MR) semi-active suspension, suspension and braking system, suspension and steering system, suspension integrated with braking and steering respectively, based on the internal coupling forces in different direction of tire. The main work of this dissertation including the following aspects:(1) The relevant theoretical and experimental studies about MR controllable suspension system have been carried out. A quarter-car suspension model which featuring the MR damper has been established and a grey fuzzy control strategy has been proposed by introducing the predictive theory of grey system on the base of fuzzy control. Then, the comparative simulation and experimental study among the proposed strategy, traditional skyhook and fuzzy control have been carried out.(2) Based on the study of MR controllable suspension and analysis of the dynamic relationship between suspension and braking systems, a coupling half vehicle model integrated MR semi-active suspension and braking system has been established, and the interaction between the performance of longitudinal and lateral has been quantitative analyzed under special longitudinal/vertical input. In order to reduce the brake distance and brake time without lowering the ride comfort greatly, a cooperative controller which based on dynamic surface control theory has been designed for suspension and braking system and the simulation contrast between cooperative control and non-cooperative control was made.(3) The lateral/vertical vehicle dynamic model integrated suspension and steering system has been established; Then, the effect of variable damping parameters to the lateral dynamics and the relationship of frequency response between lateral and vertical under different road excitation have been quantitative analyzed. After that an integrated grey fuzzy control strategy of suspension and steering system has been proposed base upon the integrated vehicle model. And the number of original data has been studied based on the ideal of equal dimension new information model.(4) The relationship of different full vehicle attitudes and their effect to vehicle performance have been analyzed. The modified Magic Formula tire model has been chosen, a nonlinear coupling full vehicle model which including suspension, braking and steering systems has been established, and its simulation model was built in the environment of Matlab/Simulink. Finally, the simulation model has been verified by real vehicle test.(5) To better understand the function and effective working area of controllable subsystems, the function range and control authority of chassis key subsystems have been analyzed by means of three-dimensional graphics. Then, a main objective-oriented hierarchical control strategy was proposed, and the system supervision and task assignment logic in the upper layer and the subsystem controllers in the lower layer were designed. Computer simulations have been conducted under three typical conditions.In the end, the study work of the whole paper was concluded. The characteristics and the innovation of the whole paper were introduced. Besides, the problems that need deep study recently were pointed out.