An evolutionary design of robust PID controllers

PID control schemes have been widely used in most process control systems represented by chemical processes for a long time. However, it is still a very important problem how to determine or tune the PID parameters, because these parameters have a great influence on the stability and the performance of the control system. In this paper, a new robust tuning algorithm of PID parameters using an evolutionary computation is proposed. A suitable set of PID parameters is calculated based on the relationship between the generalized predictive control (GPC) and the PID control. However, the proposed scheme has important user-specified parameters. Moreover, the control performance depends on the nominal model. So, the nominal model is determined by examining the control performance in all set up end-point models. These parameters are suitably determined using a real-coded genetic algorithm (GA) in consideration of the robust stability and tracking property. According to the proposed scheme, the robust stability is not only guaranteed, but the tracking property can be also improved.