Semi active Internal Model Control for passive disturbance rejection1

This paper presents novel results on the asymptotic rejection of periodic disturbances utilizing no external power sources. The exposition is done for Single Input Single Output linear time invariant systems that have a passive characteristic; representative of many vibration control schemes. The Internal Model Control approach is utilized to develop a controller that will asymptotically track reference commands or reject disturbances. The passivity of the open loop system is then utilized to determine a controller that acts in a semi-active fashion for the disturbance rejection case only. Two issues are addressed: overall closed loop stability and asymptotic rejection of the disturbance. The resulting controller leads to a discontinuous dynamic system and methods are given for handling this. Experimental results on a Single Degree of Freedom electromechanical testbed verify the performance and advantages of the Semi Active Internal Model (SAIM) method. By carefully modulating the rate of energy dissipation, performance levels akin to fully active vibration control can be achieved without utilizing external power.