Self-Tuning Type-2 PID control system and its application

This study proposes an adaptive control method of a weigh feeder. A weigh feeder dispenses material into a process at a precise rate, and it has been employed in industries, e.g., process control, cement manufacturing plants, food industry equipment, and so on. To introduce advanced control into industries, self-tuning controllers are designed for controlling a weigh feeder. Three difference controllers are designed; one degree-of-freedom (1DOF) PID, 1DOF PD, and two degree-of-freedom (2DOF) PD controllers, and these control methods are compared through experimental results. Because discharged mass is measured by employing loss-in-weight method, a reference input followed by a plant output is ramp-type, and a type-2 control system has to be designed. Since the controlled object includes an integrator, a type-2 control system can be obtained by using 1DOF PID controller. In design of 2DOF PD control, a pre-compensator is designed to eliminate steady-state velocity error. Further, to be compared with 1DOF PID and 2DOF PD control, a 1DOF PD controller is designed. In this paper, PID and PD controllers are designed on the basis of generalized minimum variance control (GMVC) to obtain useful control methods adopted in industries. In design of the proposed control methods, GMVC can be replaced precisely with a simple PID or PD controller, and advanced control performance can be obtained. Experimental results are shown and compared, and the effectiveness of the proposed design method is shown.