A Self-Tuning Controller for Systems with Unknown or Varying Time Delays

A SISO self-tuning controller with a Smith-predictor type time delay compensator (STC-TDC) is proposed to handle processes with unknown or varying time delays. Two numerical examples comparing PI control, the standard STC of Clarke and Gawthrop, the self-tuning Dahlin algorithm of Vogel and Edgar, and the STC-TDC show that the new approach performs best for both setpoint and load changes when process time delay changes occur. A third example shows that the STC-TDC matches the extended stability characteristics of the alternative approach due to Kurz and Goedecke but is computationally much simpler.