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I have some interest on this topic, as it is demands efficient scheduling strategies to be designed to optimize the performance of a manufacturing system. A manufacturing system has several components and to optimize the performance of the entire system one needs to perform a careful planning, right from the factory plan design stage to minimizing the operating costs. Often times these problems have conflicting objectives, in the sense that one needs to minimize the expenditure levels and at the same time keeping the efficiency/utilization of the system components to a maximum.

A Flexible Manufacturing System (FMS) has emerged as a highly competitive manufacturing strategy in the late twentieth century and has been a subject of intense research and exploration. It utilizes computer controlled automation systems to integrate the machine centres (MCs) with the material handling system (MHS). Such a system is capable of scheduling the production of a specific part at any of the available MCs, as well as efficient routing of the raw material on shop floor to minimize the idle time of resources and to maximize the overall efficiency. Manufacturing lead time (MLT) is the total time required to process the product in the manufacturing plant. In a typical manufacturing environment, MLT is much greater than the Actual Processing Time (APT). The APT which comprises of the set-up time and prcessing time, could be a small fraction of the MLT. Loading & unloading, transport, waiting and queueing times constitute the rest of the MLT, which we will refer to as overheads. Significant improvements in manufacturing efficiency can be achieved by utilizing automated MHSs which help in minimizing the idle time of MCs and waiting (queueing) times for transport resources. Material handling techniques have improved significantly over the last several decades.

The intelligent techniques have made the most significant impact on material handling schemes, as these techniques rely on integrated planning in the FMS decision making processes. Also, the overall plan of manufacturing, referred to as Integrated Manufacturing Planning Problem (IMPP) in literature, determines the subsequent scheduling, routing and dispatching decisions. Research presented in provides a planning model by decomposing the integrated plan into sub-plans for machine selection and operations sequence.

Automated Guided Vehicle (AGV) system is an intelligent and versatile MHS to transport materials to various locations in a FMS. AGVs are self-propelled driver-less vehicles that travel along a passive guidepath, connecting remote locations typically the Warehouse, to the MCs. Interchangeable trolleys are also available to transport a variety of payloads and a computer control mechanism allows for maximum flexibility and the ability to interface with other building systems such as elevators and automatic doors. These vehicles range from small mail deliverers to large transporters, capable of delivering hundreds of tons of material. Centralized computers control AGV movements and co-ordinate the deliveries with other material handling devices. The operation of AGV requires controlled material loading and unloading, determination of AGV path on the shop floor and guidance mechanism. The AGV controller makes several decisions on the use and control of the AGVs. These include, (1) Dispatching decisions to decide which of the several AGVs to be used to transport raw material to the MCs, (2) sequencing decisions to decide the order of use of AGVs, if several AGVs are used, (3) Routing decisions to decide the route to be taken to reach the machines, (4) scheduling decisions to decide the start, wait and finish times to avoid collision and shop locking (deadlock or stalemate), and finally, (5) loading decisions to decide on how much material per trip is to be carried for each of the machines.

My focus is geared towards designing efficient strategies that can minimize the overall processing time of the entire material submitted to the system. We have successfully demonstrated two efficient strategies for a small-scale factory plan that uses a single AGV to deliver the raw material to the respective machine centers. Currently, we are focussing on a large-scale factory plant aided with robot facilities. Wanna talk about this Eh?