Hybrid Vibration Control Adapting to State Variation of Suspension System

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In order to verify variation of suspension stiffness by considering its geometry, the suspension was analyzed using multi-body dynamics theory. It was verified from the simulation results that the stiffness at around its stroke end becomes higher than that in the nominal state. Also, the amount of shock at the stroke end was estimated and the method to suppress the shock was examined. The switching control from nominal damping to higher damping may make the acceleration response worse. It was found out that it is important to activate the actuator before the suspension approaches to its stroke end.By using sliding-mode control method, the control system was designed in order to improve the nominal performance and maintain it even when the stiffness changes in the stroke end. VSS (variable structural system) observer was designed to estimate the state of the quarter-car suspension system and the experiments are performed. A linear motor was used as the actuator in the experimental setup and the AC servo motor was used as the shaker to generate the road disturbance. VSS observer utilized the acceleration of the vehicle and did not need the stiffness force varying as the stroke approaches the end. The nonlinear force of the suspension stiffness was simulated by the linear motor. By carrying out simulations and experiments it was verified that the experimental results coincide with the simulation results and the controller designed was adaptable to the state varying according to the nonlinearity of the suspension system.