| Construction vehicle driving dynamics step into a new stage--hydraulic driving dynamics. The research is going to improve vehicles'adaptability under dynamic condition, thus optimize vehicle's performance and achieve good maneuverability and intellectualization. The key content is variable pump-variable motor system's structure and control theory.The hydraulic differential lock, according two sides motors'speed difference, simulate the differential lock of drive axis to self-acting divergence, to prevent the vehicle skidding or stalling. The paper analyses show that the common flow divider has not adaptation of the vehicle's requirement, when it is swerving. Consequently, to adapt the vehicle's requirement, the common flow divider has been altered to reduce divergence precision. However, one pump-two motors hydraulic driving system of vehicle is a multi-input, multi-output system and nonlinear and time-varying plants. When put the hydraulic differential lock in this system, the traditional control theory can not work. Aiming at complex nonlinear and variable structure factors, starting from the theory study, the paper simplifies the system to a single-input, double-output system. Combines constant-power control method and ideal hydraulic driving control structure, to control of flow difference on the vehicle driving system.According to the analysis of the running straightly and swerving conditions of the towing vehicle in this paper. The paper analyses the kinematics and kinetics of the differential. The mathematical model is established according to the analysis of static and dynamic on flow divider. Further, the hydraulic differential lock is presented, and put it into the nonlinear model of one pump-two motors flow coupling system. The paper introduces Fuzzy-PID theory to system, and presents a new control structure which uses Fuzzy-PID as control method. A Simulink model was built in the paper and was running to prove the system's well performance. At last, the paper analyses the coupling parameters in system, and gives the rules of selecting parameters. |
