ROBUST DIGITAL CONTROLLER-DESIGN FOR PROCESSES WITH DEAD TIMES - NEW RESULTS

The Dahlin controller is studied in the complex-frequency domain in te rms of performance and robust stability. Several well known digital co ntrol algorithms are compared with the Dahlin controller and found to be equivalent to it. The possibility of extending the Dahlin controlle r to the control of plants with zeros outside the unit circle and unst able plants is discussed. The essential cause of ringing is investigat ed and some ambiguous formulation is clarified. A new procedure is dev eloped for digital controller design. Compared with conventional metho ds, it provides a more effective method of eliminating ringing. Finall y, numerical examples are given to illustrate the new approach.