Partial internal model control

Internal model control (IMC) is a well-known and effective control scheme. However, when unstable processes are concerned, the original IMC structure cannot be directly used for control system implementation. In this paper, a new scheme called partial internal model control (PIMC) is proposed, which is capable of controlling both stable and unstable processes. In PIMC, a p rocess model is expressed as the sum of the stable and antistable parts and only the stable part of the process model is used as the internal model. T he process stable part is canceled by the internal model and the remaining antistable part is stabilized and controlled with a primary controller, whi ch is usually a PID-type regulator when the antistable part is of a low ord er. Various properties of a PIMC system such as internal stability and robu st stability are analyzed. The design of PIMC is discussed in detail. Vario us simulation examples are included for illustration and a real-time implem entation on a motor system is presented.