Optimizing weigh feeder performance using modeling and simulation

A weigh feeder system is a small conveyor integrated with a belt weigh bridge and speed sensor and driven by a variable speed Motor. These are widely used in Mineral/Ore and chemical industry where a measured rate of solid raw material is fed to Reactors and furnaces. In order to accurately control solid flow rate, the speed of motor/ belt is varied to compensate for the variation of quantity of solid being fed on the belt. Traditionally, such electro-mechanical systems are modeled as IInd order system which ignores the non-linearity due to dead zone and frictions in the geared motor. However, as the weigh feeder is slow speed machine, the non-linearity exhibited by the machine has a bearing on fine speed control therefore the accuracy especially at low speeds. Any inaccuracy in solid feed rate affects quality and efficiency of downstream process. In order to study the effects of friction, this paper develops the model of the electro-mechanical system of an industrial weigh feeder system and studies the dynamic response of the system using MATALB SIMULINK. The results of the simulation are used to propose an innovative calculation based self-tuning discreet time PI controller to improve the control performance of the machine.