VRFT-BASED CONTROLLERS DESIGN FOR NON-MINIMUM PHASE PLANTS

Abstract

THE MODEL-BASED CONTROLLER DESIGN METHODS ARE COMMONLY USED TO DESIGN PID CONTROLLERS, WHICH ARE WIDELY USED IN REFINING, CHEMICAL, AND PHARMACEUTICAL INDUSTRIES. THESE CONTROLLER DESIGN METHODS CAN BE BROADLY CLASSIFIED INTO TWO CATEGORIES DEPENDING ON WHETHER THE PID TUNING ALGORITHM HAS A TUNABLE PARAMETER OR NOT. FOR THE DIRECT MODEL-BASED PID DESIGN METHODS WITHOUT RESORTING TO A TUNABLE PARAMETER, THE RESULTING CONTROL PERFORMANCE IS USUALLY NOT SATISFACTORY FOR HIGHER-ORDER PROCESS DYNAMICS OWING TO THE INEVITABLE MODELING ERROR. ON THE OTHER END, WHILE BETTER CONTROL PERFORMANCE CAN BE ACHIEVED WHEN A TUNABLE PARAMETER IS INCLUDED TO DESIGN PID CONTROLLERS, THE OPTIMAL TUNABLE PARAMETER IS NORMALLY DETERMINED BY TRIAL AND ERROR PROCEDURE FROM EITHER THE PLANT TESTS OR SIMULATION STUDIES ASSUMING THE AVAILABILITY OF A PRECISELY KNOWN PROCESS MODEL, RESULTING IN AN ITERATIVE TUNING PROCEDURE AND THE EXPENSE OF CONSIDERABLE ENGINEERING EFFORTS. SIMILAR TO THE MODEL-BASED PID DESIG