Multirate controllers design by rate decomposition

In many industrial control applications the control action updating can be faster than the output measurement, leading to multirate controllers. In this paper, the controller design is approached based on the characteristics of each available sampling rate. The controller is split into two parts acting at different sampling rates. With the lowest rate sub-controller the main points of the desired response are determined while the response envelope, approaching the continuous time response of the controlled system, is completed by the action of the fast rate control part. Cancellation controllers, three-term controllers and PID controllers are designed using this approach and promising results are obtained.