# A Swarm Intelligence Method Applied to Manufacturing Scheduling

**Topics:**Ant colony optimization, Particle swarm optimization, Optimization

**Pages:**16 (5478 words)

**Published:**January 23, 2011

Abstract—In this paper we present a multi-agent search technique to face the NP-hard single machine total weighted tardiness scheduling problem in presence of sequence-dependent setup times. The search technique is called Discrete Particle Swarm Optimization (DPSO): differently from previous approaches the proposed DPSO uses a discrete model both for particle position and velocity and a coherent sequence metric. We tested the proposed DPSO over a benchmark available online. The results obtained show the competitiveness of our DPSO, which is able to outperform the best known results for the benchmark, and the effectiveness of the DPSO swarm intelligence mechanisms. Index Terms—Particle Intelligence, Scheduling Swarm Optimization, Swarm

I. INTRODUCTION In this paper we propose a new DPSO approach to face the single machine total weighted tardiness scheduling with sequence-dependent setup times (STWTSDS) problem. Scheduling with performance criteria involving due dates, such as (weighted) total tardiness or total earliness and tardiness (E-T), and that takes into account sequencedependent setups, is a reference problem in many real industrial contexts. Meeting due dates is in fact recognized as the most important objective in surveys on manufacturing practise, e.g., in [1]. The objective of minimizing the total weighted tardiness has been the subject of a very large amount of literature on scheduling even if sequence-dependent setups have not been so frequently considered. Setups usually correspond to preparing the production resources (e.g., the machines) for the execution of the next job, and when the duration of such operations depends on the type of last completed job, the setups are called sequence-dependent. The presence of sequence-dependent setups greatly increases the problem difficulty, since it prevents the application of dominance conditions used for simpler tardiness problems [2]. The choice of the STWTSDS problem as reference application for the proposed DPSO approach has then two main motivations: first the fact that the solution of single machine problems is often required even in more complex environments [3], and second the...

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