Modeling Of Continuously Adjustable Shock Absorber And Research Of Semi-active Suspension Control Algorithm

Suspension system is an important vehicular sub-system which determines ride comfort ability and handling stability. Semi-active suspension has solved the contradiction between ride comfort ability and handling stability of passive suspension, and it can give considerations to both sides in any road conditions. The control quality of semi-active suspension and active suspension is close, but semi-active suspension’s structure is simple and its price is cheap. In this paper, the continuously adjustable shock absorber which is the core of semi-active suspension is studied. The mathematic model and the AMESim model of the continuously adjustable shock absorber were established. Then the damping control algorithm based on the model is bulited. This paper provides theoretical reference for the application of the continuously adjustable shock absorber on the vehicle. The main research work and conclusions are as follows:(1) The main external input of the suspension system is the road roughness. The random road model was established based on MATLAB, and then the model was verified by simulation. The matching damping to vehicle suspension was studied, to verify the established continuously adjustable shock absorber meets the demands of vehicle in different road roughness.(2) Based on the analysis of the structure and principle of double-tube shock absorber, the structure and principle of continuously adjustable shock absorber was also analyzed. Its mathmatic model of rebounce stoke and compress stoke was established, and then the AMESim model of continuously adjustable shock absorber was built. The continuously adjustable shock absorber was tested on the dynamic servo suspension tester to verify the correctness of established model, to lay the foundation of control algorithm research of semi-active suspension.(3) Based on the established model of continuously adjustable shock absorber, the damping characteristic was obtained by the cosimulation of MATLAB and AMESim. The main structure parameters to the damping characteristic were analyzed by changing the main structure parameters in the model, the theoretical reference is provided for the design and engineering of the continuously adjustable shock absorber.(4) Aiming at the nonlinearity of the semi-active suspension, a model reference sliding mode controller was designed. A skyhook model was adopted as the reference model, and the response error between the reference model and the controlled object was used to design the sliding surface. By controlling the damping force, the response of the controlled object would follow that of the reference model as much as possible. The damping characteristic curve of the continuously adjustable shock absorber is analyzed. By dealing with the data, the electromagnetic valve variable orifice diameter at a certain speed of piston rod and expected damping force, which provides effective data source for shock absorber control.The effectiveness of the model reference sliding model control and passive suspension with large damping, middle damping and small damping was compared by cosimulation. The results show that the comprehensive performance of model reference sliding mode control is better than these of passive suspension with large damping, middle damping and small damping. And the model reference sliding mode control is more suitable for the damping control of the semi-active suspension.