Simulation Study of Robust Dispatching Algorithm for Mixed VLSl Manufacturing

Abstract

The paper describes a new dispatching algorithm for dynamic allocation of works-in-process (WIP), named pseudo periodical priority dispatching (PID), The algorithm is developed to manage WIP at a processing step in an autonomous distributed manufacturing system. The priority of dispatching is examined when each quantum starts, by considering both the amount WIP in the input buffer of the processing station and the arrival rate of WIP. During the quantum, only one type of WIP is assigned to a particular machine. Performance parameters i.e., adjustment rate, throughput, response time, and tardiness when applying (P3D) are compared with the results of the first come first serve (FCFS) and the shortest processing time (SPT) in simulations assuming Poisson arrival. A fluctuation in arrival rate causes large inventories at the processing station The adjustment rate is the lowest and the availability of machines is the highest with P3D, therefore P3D can quickly dissolve a bottleneck. Both P3D and SPT produced shorter response times than FCFS and hath P3D and FCFS produced shorter tardiness than SPT. The small quantum size helps to shorten the response time in P3D. P3D with the minimized quantum size gives a good estimation when setting the due date. P3D achieves a very far dispatching even though the arrival rate differs by 40 times among works in a product-mix. The author concludes from the above results that P3D has a robust dispatching algorithm tit the case of a broad product-mix