Design of PI fuzzy logic controller to overcome belt weigh feeder system nonlinearity

A belt weigh feeder system is an electro-mechanical system consisting of variable speed flat belt conveyor designed for feeding bulk material in the process in a controlled fashion. The dynamic weight of bulk material on the belt is measured with a belt weigh bridge and the belt speed is controlled to compensate for the variation in weight so that the feed rate is maintained constant. The problem of belt speed control is challenging as the dynamic response of system is nonlinear and there are frequent changes in belt load due to variation in bulk material characteristics. The control accuracy of belt weigh feeder is fully dependent on the controller performance in providing precise control of speed of motor/belt. Any delay in achieving the set feed rate or frequent deviation between set and actual feed rate affects the quality and efficiency of downstream process. Conventional PI controller is unable to provide optimum control due to system nonlinearity. To tackle these problems, first the system is modeled and rigorously simulated in open and closed loop to have a better insight into its nonlinear response. Subsequently, PI Fuzzy Logic controller is designed for control of belt weigh feeder. The results indicate substantial improvement in control accuracy of the system with PI Fuzzy Logic controller.