Scheduling automated, unmanned manufacturing systems is significantly different from traditional job shops where human presence is implicitly assumed. Deadlocking has been identified as one of the critical problem in the control of automated manufacturing systems. Past approaches have been myopic in the sense that deadlock avoidance and recovery have been treated as run time problems of the system. In this paper, formulations for deadlock-free schedules are proposed and the importance of considering both material handling and buffer space availability while scheduling such an automated workstation are discussed. Extensions to the basic model and solution methods are also presented.

The author states that, in the original paper (D.L. Hoitomt and P.B. Luh ibid., vol. 9, no. 1, p. 1-13, 1993), the model formulation of the scheduling problem is highly irregular. If one were to consider the formulation by itself it would seem that since neither the precedence nor processing time constraints are linked to time, we could set all /spl delta//sub ijkh/=0 and obtain a feasible solution with jobs overlapping on machines. It is noted that in the subsequent relaxation of the capacity constraint, the binary variables have been set to 1 from start to finish time of the corresponding operation to account for capacity. The need for the model formulation to include such constraints explicitly is discussed, and the original authors discuss the relevance of the comments. The existence of related and similar results in previous works is also considered.>

Scheduling automated, unmanned manufacturing systems is significantly different from traditional job shops where human presence is implicitly assumed. Deadlocking has been identified as one of the critical problem in the control of automated manufacturing systems. In this paper, formulations for deadlock-free schedules are proposed and the importance of considering both material handling and buffer space availability while scheduling such an automated workstation are discussed.>