Ripple Rejection for a Multirate Control System Including an Integrator

In the present paper, we discuss a design method for a multirate system, in which the update interval of the control input is shorter than the sampling interval of the plant output. In this multirate system, the intersample output may oscillate between sampled outputs even if the sampled output converges to the reference input because the control input can be changed between sampled outputs. In the conventional method, intersample ripples can be eliminated independently of the sampled response. However, this method is not valid when a controlled plant has an integrator. In the present study, we discuss this problem and propose a method by which to relax the problem constraints.