Narrow-Band Disturbance Rejection Using Semi-Active Control

Abstract

Abstract The present study examines the potential of using a semi-active controllable damper, whose damping coefficient can be modulated in real-time, for narrow-band disturbance rejection applications. A frequency-domain optimal control algorithm is developed for determining the controllable damper input (of twice the disturbance frequency) that minimizes the force transmitted to the support at the disturbance frequency. The effectiveness of both open-loop and closed-loop controllers in rejecting the transmitted disturbances are evaluated. The results of the study indicate that for physically achievable damping coefficient variations, the support force could be reduced by about an additional 30%, beyond the levels due to the passive isolation characteristics (no damping coefficient variation). When the disturbance phase changed during the simulation, the effectiveness of the open-loop controller reduced, while the closed-loop controller was still able to generally reduce vibrations to levels lower than those due to pure passive isolation. Even so, closed-loop control of the semi-active damper was not able to completely maintain the level of reduction in vibration when the disturbance phase changed, suggesting that an adaptive controller may be necessary.