Output-Error Criteria in Multi-Model Adaptive Control with Experimental Application to pH Control

The use of output-error criteria in a multi-model adaptive PID controller is developed and evaluated in an experimental study using a nonlinear pH neutralization process. Variable hysteresis depending on model distance is included in the model switching. The performance and robustness characteristics of the multi-model controller are compared to those of a conventional PID controller, conventional self-tuning controller, and a multi-model adaptive KID controller using a prediction-error criterion. Both the output-error criterion and especially the variable hysteresis were found to be significant factors in the performance of the multi-model adaptive controller.