Identification of Minimally Restrictive Assembly Sequences using Supervisory Control Theory

TL;DR

The paper tackles the need for flexible assembly sequence planning under multiple constraints in modern manufacturing. It adopts Supervisory Control Theory to model tasks and constraints as finite automata and to synthesize a controllable, non-blocking, and minimally restrictive supervisor $S$ such that the plant $P$ satisfies the closed behavior $P||S$ with the specification $K$. A case study with tasks $A$–$E$ and a repeatable task $F$ demonstrates the approach, producing a minimized supervisor and showing removal of a blocking state to guarantee completion. The work provides a framework for generating all feasible sequences for subsequent optimization or disruption handling, and discusses scalability and extensions to multi-agent coordination.

Abstract

Modern assembly processes require flexibility and adaptability to handle increasing product variety and customization. Traditional assembly planning methods often prioritize finding an optimal assembly sequence, overlooking the requirements of contemporary manufacturing. This work uses Supervisory Control Theory to systematically generate all feasible assembly sequences while ensuring compliance with precedence and process constraints. By synthesizing a controllable, non-blocking, and minimally restrictive supervisor, the proposed method guarantees that only valid sequences are allowed, balancing flexibility and constraint enforcement. The obtained sequences can serve as a basis for further optimization or exception management, improving responsiveness to disruptions.

Figures (5)

• Figure 1: FAs of a generic task X: (a) single-execution task with states Non-completed, Executing, and Completed; (b) repetitive task with states Available and Executing.
• Figure 2: Digraph of precedence constraints among tasks.
• Figure 4: FA representation of the second dynamic constraint.
• Figure 5: Synchronized system automaton.
• Figure 6: Minimized supervisor automaton.