Event-based PID control in a flexible manufacturing process

In the flexible manufacturing environment some processes that until now did not need a close loop control need to be controlled so that the precision of the task permits the continuing of the manufacturing. As the processes are optimized and the manufacturing consists of multiple parallel processes, there is a need of assuring that a product is at a certain location at a certain time. In the control of a task, usually, the output of the system is measured in a timely manner at a certain sampling time. This is usually not possible in the manufacturing processes as a product position is given based on events, by sensors placed at certain locations. Certain event-based PID controllers were proposed and implemented in other control areas but in this controllers the event triggering is given by the error passing a certain level. This kind of controller cannot be implemented given the necessity of high frequency measurement of product position. In this paper we propose an PID event-base controller that uses as triggering event the activation of one of the manufacturing process sensors by the product. As the sensors are placed only in key positions the number of activations is limited. Based on these sensors the PID controller determines the necessary control signals between the key locations.