Adaptive design method of multirate PD controller

This paper discusses a design method for a sampled-data control system, in which the sampling interval of the plant output is an integer multiple of the hold interval of the control input. To control such a control system, an adaptive multirate Proportional-Derivative(PD) control method is proposed. It is assumed that the sample response can stably follow its reference input by a multirate PD control law without the steady-state error, and the multirate PD control law is extended independently of the sample response such that intersample ripples are eliminated in the steady state. Furthermore, the extended multirate PD control system is enhanced with an adaptive law in order to achieve the control objective even if plant parameters are unknown or changed. In the proposed method, the transient response is not deteriorated by the integral compensation because the steady-state error and intersample ripples can be eliminated without the integral compensation.