Analytical performance models for closed-loop flexible assembly systems

Flexible Assembly Systems (FASs), which form an important subset of modern manufacturing systems, are finding increasing use in today's industry. In the planning and design phase of these systems, it is useful to have tools that predict system performance for various operating conditions. In this article, we present such a performance analysis tool based on queueing approximation for a class of FASs, namely, closed-loop flexible assembly systems (CL-FASs). For CL-FASs, we describe iterative algorithms for computing steady-state performance measures, including production rate and station utilizations. These algorithms are computationally simple and have a fast convergence rate. We derive a new approximation to correct the mean delay at each queue. This improves the accuracy of performance prediction, especially in the case of small CL-FASs. Comparisons with simulation results indicate that the approximation technique is reasonably accurate for a broad range of parameter values and system sizes. This makes possible efficient (fast and computationally inexpensive) analysis of CL-FASs under various conditions.