Manufacturing Scheduling Problems Research Articles

A Discrete Time Average Cost Flexible Manufacturing and Operator Scheduling Model Solved by Deconvexification Over Time

A flexible manufacturing and operator scheduling problem is introduced and solved. The principal concern is to schedule operators over time to various activities of a manufacturing system for the purpose of optimizing some steady-state criteria. In mathematical terms, the problem is modeled as a deterministic, infinite horizon, discrete dynamic program. Our solution procedure is to convexify the problem to obtain a linear program, and then to deconvexify the solution of the linear program over time to arrive at an optimal solution. Apparent loss in objective value due to the deconvexifications is circumvented with buffer inventories. The procedure is reduced to solving a sequence of linear programs and the complexity is stated in these terms.

Multi-pass expert control system - a control/scheduling structure for flexible manufacturing cells

Abstract Expert systems are currently being touted as a means to resolve manufacturing scheduling problems. Unfortunately, the expert systems developed to date are neither generic nor are they responsive enough to be used for on-line system control. In this paper, a control structure is outline which takes advantage of both expert system technology and discrete event stimulation. The simulation is used as a prediction mechanism to evaluate several possible control alternatives provided by the expert system. A performance measure is obtained from the simulation for each of the suggested alternatives. A control effector is then employed to affect the physical control of the cell based on the measured. This performance measure is worth a great deal of domain-specific knowledge that otherwise would have to be included in the expert system knowledge base. The integration of the expert control system, the simulation, and the control effectorsform a system called a multipass expert control system (MPECS). MPECS is designed for the control and scheduling of flexible manufacturing cells. Experiments to evaluate the performance of MPECS have yielded advantages of between 2.3% to 29.3% compared to single-pass, single-rule priority dispatching and multipass, multirule dispatching procedures.