A procedure based on branch-and-bound for the Cyclic Hoist Scheduling Problem

Abstract

When various kinds of products must receive the same treatments in a production line of tanks and the size of batches is high, a cyclic manufacturing composed of a job from each batch can be scheduled. A hoist ensures the auto- mated transfer of the jobs between tanks. The probl em consists in the scheduling of repetitive hoist movements, which is known as CHSP (Cyclic Hoist Scheduling Problem). The objective is to find a sequence which minimizes the cycle time for jobs from different products. We consider the problem where types of products must be treated and we search an n-cyclic schedule. The algorithm is based on the resolution of different sequences of products. For each one, a branch-and-bound is solved which considers only coherent subsequences. It enables to reduce the com- putational times most of the time for instances with 5 tanks and 4 product types