Operation of manufacturing systems with work-in-process inventory and production control

The operation of large manufacturing systems with buffers has two goals: to meet production target and minimize the work-in-process (WIP) inventory. This paper introduces a novel approach, based on optimal control theory, to achieve both goals simultaneously by on-line adjustment of the production rate of each machine. In this method the state variables are the buffer levels, the control variables are the machine production rates, and the output variable is the target production (the demand). The method is evaluated through simulations under various conditions, and compared with other methods in the literature. The results demonstrate that the proposed method can successfully produce low WIP inventory than other methods, while the required production demand is still fulfilled. It is also shown that the method is capable of providing feasible solutions for large manufacturing systems - a goal that is harder to achieve with the current known method.