Sequencing algorithms for multiple arc-welding robots considering thermal distortion

This paper focuses on sequencing welding lines in multiple arc-welding robot systems, which is the problem of assigning individual welding operations to robots as well as determining their sequences with the objective of minimizing the maximum completion time. Each welding operation is denoted by a weld line with two end-points, each of which can be a possible starting point for the welding operation. Thermal distortion is explicitly considered by introducing a delay between welding operations associated with weld lines near each other. Due to the complexity of the problem, this paper suggests three types of search heuristics, genetic algorithms, simulated annealing and tabu search, each of which incorporates new methods to generate neighbourhood solutions. To show the performances of the heuristics, computational experiments are performed on a number of randomly generated test problems, and the results are reported. In particular, some of the search heuristics outperform the exiting method.