Approximation grid evaluation-based PID control in cascade with nonlinear gain

The main disadvantage of standard PID type controllers is the absence of self-tuning features. The PID parameters are expected to vary either as operating condition or dynamics of the system vary or at different phases of control process with intent to develop an optimal strategy. The purpose of this study is to overcome the existing disadvantage by using a cunningly chosen nonlinear gain. The novelty of the study associates with a sound choice of the best form of nonlinear gains to impact the performance of a PID controller when being coupled with the cascade nonlinear gain (known as NPID). An approximation grid evaluation of NPID controller used in a feedback control problem is proposed. This eliminates a technical restriction when using previous nonlinear variation evaluation. The evaluated forms cover a broad range of popular variants. To the practicing control engineers who prefer to realize an effective NPID control, the proposed approach highlights the potential to make a reasonable selection of the nonlinear gain functions without requiring any additional process information.