Automatic tuning of nonlinear PID controllers for unsymmetrical processes

Relay auto-tuning of linear PID regulators is now a proven technology in the process control industry. In this paper it is extended to auto-tune nonlinear PID controllers for unsymmetrical processes. Two sets of PID parameters, each for one operating mode, are obtained with a single relay experiment. Excellent performance of the auto-tuned nonlinear control system is substantiated by simulations.