Abstract
In this study, in order to improve the riding comfort and unsprung mass control of a semi-active suspension, we develop a new control system design method introducing unsprung mass control into gain-scheduled H_∞ control that changes the controller gain by the sprung mass vibration frequency. The proposed unsprung mass controller is a modified Ground-hook damper. By including the modified Ground-Hook damper control in the controlled object in the controller design, the gain-scheduled H_∞ control system reducing the vibration of the unsprung mass can be designed, without increasing the dimension of the controller. Thus, because of only the sprung mass vibration reduction, weighting functions can be briefly chosen. Here, the scheduling parameter of gain-scheduled H_∞ controller is included in weighting functions for controller output. Then, the controlled object with the modified Ground-Hook damper is a Linear-Time-Invariant system, The generalized plant including the weighting functions is a Linear-Parameter-Varying system. Furthermore, because of our control performance realization, we develop a design method of Kalman filter which can estimate the vehicle motion with high accuracy. In our study, by considering disturbances for all state values of the observer, we design the Kalman filter which can estimate states accurately. Here, observation signals are sprung mass accelerations and unsprung mass accelerations of semi-active dampers for each wheels. The estimated piston velocity is used to adjust the damping of semi-active suspension. Also, the unsprung mass velocity is used for unsprung mass control. The effectiveness of our control method is verified by carrying out simulations and experiments.
