Decentralized PID control systems design on frequency domain and their stability

This paper deals with the design problem of decentralized PID control syste ms. An automatic tuning algorithm based on the partial model matching on th e frequency domain for the decentralized PID controller is presented. In th e tuning scheme, the partial model marching between the loop transfer funct ion of the control system and a desired open-loop model at some frequency p oints is considered. The introduction of compensators, a parallel feedforwa rd compensator (PFC) and a pre-compensator, is also considered in order to guarantee the stability of the decentralized control system. It is shown th at the diagonal-dominance, which is necessary to realize a stable decentral ized control system, can be relaxed by introducing a PFC. Further, robust s tability of the resulting control system is analyzed and a guiding principl e for the design of the decentralized PID control system will be provided.