Controller order reduction by simulated data
After designing a digital controller R/S based on a discrete time model of plant, the controller order may be reduced either by an open loop type identification or by closed loop identification. In the closed loop identification we suppose that the plant model is known, so a closed loop system with the plant model and the designed controller can be simulated and excited with a reference signal r(t)(see: controller identification scheme). This signal together with the output of the controller u(t) may be used for identification of a reduced order controller based on closed loop output error algorithm conid. In order to compare the robustness and the performances of this reduced order controller and the nominal designed controller different criteria can be considered:
If the order of the numerator R and the denominator S of the nominal controller are decreases step by step and the above criteria are computed, we obtain an interesting table which significantly help us to choose a reduced order controller for the plant.
For a more detailed comparison, the frequency responses of the controllers and the magnitude of the sensitivity functions may be compared using compcon function.
The real time acquired data in closed loop operation of the system with the nominal controller can also be used to perform the controller order reduction by cortr function.
See: Controller order reduction module .
(file cor.htm)