| The ride comfort, active safety and handling stability of automobile have been effectively improved by the application of electronic technology and control theories, but as concerned to the combintion with these electronic control systems and their integrated control are becoming one research hot issue in the field of active control for vehicle dynamics. Combining with current research achievements and existing problems of vehicle chassis dynamics control, from the view of coupling mechanism and nonlinear tire force characteristics, the dissertation author investigates some key issues of chassis integrated control, such as nonlinear dynamics modeling, integrated system decoupling control methods and time-delay control of the key subsystems. The main work of the dissertation includes the following aspects:(1)The coupling mechanism of the automobile chassis control system has been analyzed. One coupled nonlinear dynamic model of the vehicle has been established through Newton-Euler method, based on the analysis of nonlinear tire force characteristics. The coupling relationship among braking, steering and suspension assembly, and other subsystems can be described in the specific mathematical model, and their simulation models are built in the environment of Matlab/Simulink.(2)The integrated control system model of electronic stability program (ESP) and active suspension system (ASS) is established. According to nonlinear decoupling control theory, an input-output decoupling controller and a disturbance decoupling controller of the integrated system are designed. In addition, setting up a closed-loop controller and combining it with the original system, a compound controller is obtained to improve ride comfort and handling stability. Under a variety of conditions, a computer simulation of Matlab/Simulink and a hardware-in-the-loop test of LabVIEW have been carried up to verify the effectiveness and robustness of the nonlinear decoupling control strategy.(3) According to the disadvantages of the nonlinear decoupling control, an integrated decoupling control approach based on neural network inverse method is proposed, and the integration of active front steering (AFS), direct yaw moment control (DYC) and active suspension system (ASS) is studied. The computer simulation of Matlab/Simulink has been carried up under change lane and step steering conditions.(4) The sources of time-delay in automobile chassis control system have been analyzed. The signal detection, the disturbance and the control channel time-delay and their effects to output signals real-time and the stability of closed-loop control systems have also been analyzed.(5) A quarter-car magneto-rheological semi-active suspension model with time-delay is built. With respect to the time-delay differential equations, a delay-dependent sliding model controller with less conservatism is proposed. The problems of solving the maximum system margin time-delay and the factors of the system time-delay stability have been researched by linear matrix inequality (LMI). In order to verify the effectiveness of the delay-dependent sliding model control law for the magneto-rheological semi-active suspension system, the simulations of Matlab/Simulink and rig tests have been conducted under two typical conditions.(6) For the aim of improving the performance of the magneto-rheological semi-active suspension control system, a delay-dependent H2/H∞method is proposed by formulating the optimization and constraint objective respectively. According to LMI method, the sufficient condition for the asymptotic stability and existence of delay-dependent H2/H∞controller are obtained. The computer simulations of Matlab/Simulink and real vehicle rig tests comparision between the ordinary H2/H∞control and delay-dependent H2/H∞control system is made.(7) In the end, the research work of the whole dissertation is concluded. Besides, the problems that need detailed research are pointed out. |
PDF Full Text Request