Research On Automatic Leveling Control Technology Of Active Hydro-pneumatic Suspension

Due to its excellent non-linear and high bearing capacity, the hydro-pneumatic suspension is more and more equipped with military vehicles, heavy duty vehicles, high-grade off-road vehicles and a small number of passenger cars. Another major advantage of the hydro-pneumatic suspension for the use of hydraulic cylinders and ancillary equipment, to achieve the purpose of adjust body attitude and control body height.Based on the theory of adaptive backstepping control and sliding mode control, to achieve automatic regulation body attitude. The control strategy is designed to meet the control target, which is based on the traditional single wheel suspension system, the single wheel hydro-pneumatic suspension system and the full vehicle suspension system. The control strategy to meet the different road disturbance and control system internal parameters of the case, to achieve automatic leveling control of the body, and through digital simulation, analysis of internal variables in the process of detailed changes, finally come to the merits of the control strategy.The model of the single suspension system is established, and the control algorithm of backstepping is used to control the height of the vehicle. In the control strategy, the adaptive law is combined, to self-turn uncertain perturbation and non-modeling dynamic characteristics of internal parameters of control system. Through the simulation, a detailed analysis of the changes of variables in the regulation process, prove the validity of this control strategy.The model of single wheel hydro-pneumatic suspension system is established, and the inner and outer loop control strategy is adopted. The outer loop uses the adaptive backstepping control to adjust the height of the vehicle body. Inner loop using sliding mode control algorithm, tracking the desired tracking force of the outer loop, and to achieve the compensation of the nonlinear. A special switching function is proposed to replace the sign function switching law in the traditional sliding mode control, which solves the problem of chatter. Through the simulation analysis, the control strategy can be realized on the body height control, and has been the role of inhibition road disturbance.The model of full vehicle hydro-pneumatic suspension system is established, and the control strategy of double closed loop is used for reference. The outer loop adaptive control strategy solves the influence of vehicle body mass and moment of inertia change caused by load variation. In the same, the improved sliding mode control strategy is also used to improve the sliding mode chatter problem. The effectiveness of the control strategy is verified by the simulation, and the effect of inhibition different road disturbance is also proved.The hardware circuit and the software realization of the vehicle body leveling control are designed. The hardware circuit adopts the control mode of double control chip, which avoids the problem that the program is bloated and the logic is not clear, and the energy saving target and the voltage protection function of the main control board are realized.