Schedule Execution using Perturbation Analysis

Abstract

In a holonic shop floor control (SFC) architecture, a reactive scheduler co-operates with an autonomous on-line SFC system to combine high performance with reactivity against disturbances. To take its decisions, the on-line SFC system uses the existing schedule as advice. This "schedule execution" problem (SE) is not trivial, because the decisions taken by the on-line SFC system are local decisions in a combinatorial optimisation problem. By representing the schedule as a graph, this paper presents an algorithm for SE, based on perturbation analysis. It tackles the non-linearities in the production system by a combination of linearisation and feedback control. 1. Introduction In industry, high performance schedulers currently are hardly used, due to the lack of schedule robustness [14]. While a near-optimal schedule is executed on the shop floor, several disturbances occur: rush orders, machine breakdowns, etc. It turns out that the performance of a schedule is very sensible to these..