Petri net-based real-time scheduling of time-constrained single-arm cluster tools with activity time variation

It is challenging to schedule time-constrained cluster tools subject to activity time variation. With the help of their Petri net model, a real-time control policy is used to offset the activity time variation. Based on it, the schedulability conditions and scheduling algorithms are presented for single-arm cluster tools. The schedulability conditions can be analytically checked. Algorithms are developed based on analytical expressions such that it is also computationally efficient. The schedule obtained by the scheduling algorithms together with a real-time control policy forms the real-time schedule. It is optimal in terms of cycle time.