Model-free PID Controller Autotuning Directly Applicable to Real Control Loops

Many PID controller tuning methods have been presented since Ziegler and Nichols published their method in 1942, but none of those methods were used widely. The Ziegler and Nichols method has several advantages over newer methods: it is easy to conduct, the relations for controller parameter computation are simple, the method relies on experiment, and it does not require any model. Newer tuning methods are usually model-based, but the model-free methods are preferred in common industrial practice. This paper presents a model-free tuning method that respects the “restrictions” given by the easy usage of the Ziegler and Nichols method. The method is model-free, and new controller parameter computation is based on evaluation of control quality indicators. The evaluation is done without disconnection of the controller and with no other control restrictions during control.