A new ILP Model for a Line Balancing Problem with Minimization of Power Peak
Abstract
Encouraged by the growing concern of industry for energy efficiency, several recent research works have emerged that focus on energy constraints and/or optimization criteria (mostly in relation to energy consumption, energy cost and power peak) in production systems. However, as far as we are aware of, very few works exist that consider energy at the design stage of a production system, e.g. for the Simple Assembly Line Balancing Problem (SALBP). SALBP is a classical NP-hard problem in which tasks with given execution times and precedence relations must be assigned to the workstations of a paced assembly line so as to minimize either the cycle time or the number of workstations. In this work we study the recently introduced SALBP with Power Peak Minimization (SALB3PM), where tasks also feature a constant power consumption: to smoothen the power consumption profile, the minimization of the overall power peak over a production cycle is sought for. SALB3PM generalizes SALBP since scheduling decisions add to the core balancing decisions, and is hence NP-hard as well. We propose a novel 0-1 Linear Programming formulation for SALB3PM based on three sets of binary two-index variables that respectively: represent the assignment of a task to a workstation; assert whether two tasks are assigned to the same workstation; model the trigger of task at a given date. Problem-specific valid inequalities and some additional preprocessing are presented, and numerical results are discussed.