Nonlinear PID controller design using fuzzy logic

An algorithm for designing a nonlinear PID controller is presented. The essential idea is to combine linear controllers using fuzzy reasoning to produce a nonlinear PID controller. The resulting controller enjoys several interesting properties: It has the limiting structure of a PD controller for maximum error and becomes a PI controller, as the error tends to zero. Large control effort is produced for large error and small control effort for small error. This makes a very fast response without overshoot an attainable goal. Also. the simple structure and stability properties of the conventional PID controller are preserved. Numerical simulation results demonstrate the effectiveness of the proposed algorithm in handling nonlinear systems and systems with time delay.