Vehicle Chassis Integrated Control Based On Magnetorheological Semi-Active Suspension

With the rapid development of national economy and the great improvement of people's living standard, automobile has come into people's life and work, and become an indispensable means of transportation. Meanwhile, the high running velocity and road traveling consistency make people have more demands on the comfort, handling stability and security of automobile. More and more control systems are used in automobile with the improvement of electron and automatization technique. As a bridge connecting between vehicle body and chassis, electronic control suspension has become an important part in automobile chassis control systems. Because of its rapid response, wide bandwidth, low consumption of energy and simple structure, the magnetorheological (MR.) semi-active suspension has attracted much more attention in the research domain of electronic control suspension. In recent years, due to the inherent hysteresis and nonlinear nature of magnetorheological(MR) fluid dampers, most researches on the MR. semi-active suspension were still in theory and lab, and few control system was used in the whole vehicle. Though some semi-active control algorithms can achieve some control performances for particular characteristics, there are still some limitations that the coupling and harmony of full car suspension model are scarcely considered. Therefore, considering the influence among multi-systems of the full vehicle, it is valuable to research the coordinated control aim to the general performance of the full vehicle based on MR. semi-active suspension. From the middle of the 1980s, most researches have been made on the coordinated control of the whole vehicle multi-systems both in the theory and the application in the enterprise and academia. However, most researches on integrated control are about two systems, and just have single controller. Few researches contain the influence of the vehicle chassis systems and coordinated control. A mixed model MR and the controller are designed in this dissertation. After installing on a mini car, the road test is carried out for the semi-active suspension. Based on the MR suspension system, this dissertation analyzes the coupling relations and mutual influence among the motion relations of suspension, steering and braking system, and designs an integrated controller of active suspension and active steering system. In addition, the coordinated controller of semi-active suspension, ABS and direct yaw moment control system is designed. The research contents of this dissertation are listed as follow:(1) Firstly, the research progress of vehicle dynamic and vehicle chassis active control are introduced. Secondly, the research actuality and the problems of vehicle chassis integrated control are analyzed. Finally, the contents and innovation points of this dissertation are put forward briefly. (2) The mathematical models of suspension, steering system, braking system and the tire of the vehicle chassis are established. The simulation in MATLAB/SIMULINK is carried out on different condition, and the interconnections and confinements among the three systems are analyzed and calculated.(3) A magnetorheological fluid damper based on mixed mode is designed, and a mathematical model of MR fluid damper is built. The damper is installed on a refitted car designed after a bench test. A PID controller whose parameters can be adjusted is designed. Based on characteristics such as high uncertainty and time delay of magnetorheological semi-active suspension, the full vehicle simulation test on different work conditions is carried out. Based on ARM Microcontroller Unit LPC2292, this dissertation designs the charge amplifier circuit, the condition circuit of vehicle speed signal, the drive circuit of constant-current source and the fault diagnosis circuit of the system. Real-time embedded operating systemμC / OS- II is introduced, and control algorithms are successfully ported. Bench test and road test are taken for the vehicle test with the semi-active suspensions.(4) After setting up seven degrees of freedom of the vehicle model, the optimal controller is designed for semi-active suspension system, and the optimal control rate of the stochastic state feedback regulator is obtained by using the separation theorem. The slide mode controller (SMC) which can track the target yaw rate is designed. In order to improve the vehicle ride comfort on steering condition, an upper coordinated controller is designed. Based on the vehicle sensors, the upper coordinated controller real-timely adapts different tracking targets and control parameters of the steering and suspension system. The simulation results showed that the controller can improve the ride comfort and the handling stability of the vehicle significantly.(5) In order to improve the vehicle ride comfort and handling stability, the PID, slide mode control and logic threshold controllers are designed for suspension, steering and braking systems. Based on state identification, the simulation of the whole vehicle control systems is carried out on different conditions.(6) The coordinated controller of ABS and semi-active suspension system is designed based on ARM7, and then the vehicle road test is made.(7) The study work of the whole dissertation is concluded, and then the advice is given for the next step work.