CACSD tools for tuning Multi-Rate PID controllers in time and frequency domains

Usually constrains on the sensors are such that the control action could be updated N times faster than the output measurement. In order to generate the control signal, a digital PID controller with different internal rates (MRPID) is considered in this paper. Then, a CACSD tool implemented both for Matlab and Sysquake is presented. The tool calculates the gains of the controller for a generalisation to MR systems of Ziegler-Nichols frequency response method. Besides, using Sysquake, a tuning rule in the time domain is also found empirically thank to the huge number of experiments that can be done fast and easily.