MINIMIZING THE FLEET SIZE WITH DEPENDENT TIME-WINDOW AND SINGLE-TRACK CONSTRAINTS

This paper considers the problem of determining a cyclic schedule that minimizes the number of material handling transporters required to perform a given set of operations in a production cycle. Each operation moves a job (i.e., a piece of work-in-process) from one location to another, and the starting time of an operation must fall within a time window. The transporters performing the operations share a single-track during their movement and must be scheduled to avoid traffic collisions. A cyclic schedule specifies, for each operation in a cycle, the starting time and the transporter that performs the operation. An algorithm is proposed that derives heuristic cyclic schedules and is able to find the optimal schedule under certain conditions. Results evaluating the effectiveness of the heuristic under general conditions are given.