Evolving Allocation Rules for Beam Search Heuristics in Assembly Line Balancing

Abstract

AbstractWe study the evolution of rules that define how to assign tasks to workstations in heuristic procedures for assembly line balancing. In assembly line balancing, a set of partially ordered tasks has to be assigned to workstations. The variant we consider, known as the assembly line worker assignment and balancing problem (ALWABP), has a fixed number of machines and workers, and different workers need different times to execute the tasks. A solution is an assignment of tasks and workers to workstations satisfying the partial order of the tasks, and the problem is to find a solution that maximizes the production rate of the assembly line. These problems are often solved by station-based assignment procedures, which use heuristic rules to select the tasks to be assigned to stations. There are many selection rules available in the literature. We show how efficient rules can be evolved, and demonstrate that rules evolved for simple assignment procedures are also effective in stochastic heuristic procedures using beam search, leading to improved heuristics.KeywordsCombinatorial optimizationGenetic programmingAllocation rulesStation-based allocation proceduresAssembly line balancing