A hybrid algorithm for the cyclic hoist scheduling problem with two transportation resources

• We propose a hybrid algorithm to solve the two-hoist cyclic scheduling problem.
• This algorithm searches the best hoists’ assignment.
• Also, the best sequence for each hoist.
• All sequences generated avoid collision between hoists.
• Optimal solutions are found in many benchmarks.

In automated electroplating lines, computer-controlled hoists are used to transfer parts from a processing resource to another one. Products are mounted into carriers and immersed sequentially in a series of tanks following a given sequence.The aim of this study is to propose an algorithm to solve the two-hoist cyclic scheduling problem. This problem consists in finding a repetitive sequence of hoists’ moves, while avoiding collision between the hoists which share a common track. The objective is to minimize the period of this repetitive cycle.First, a set of sequences is generated. After that, for each sequence, an algorithm is applied to assign moves to hoists. Finally, a mixed integer linear programming model is formulated by taking into account the two sequences of hoists moves. Then it is solved to give the starting times of moves.