IRFM control with application to HDD servo system

Summary form only given. In Moore et al (Automatica, vol. 29, no. 4, pp. 941-951, 1993), by changing the control input N times faster than the system output is sampled, it was shown that both the closed loop poles and zeros can be arbitrarily assigned. However, the multirate strategy produces a degradation in the intersample behavior, namely, intersample ripples appear. In Chen et al (Proc. IECON, pp. 1171-1176, 1999), a multirate control scheme was proposed to attack the intersample chattering. However, the method is only applicable to a control plant which has at least one integrator in its model. Here we present a new intersample ripple free multirate (IRFM) control scheme for general LTI systems. A constraint on the controller parameters is introduced in the scheme to force the multirate control inputs to converge to the same constant level in order to eliminate the intersample ripple.