Calculating Restart States for Systems Modeled by Operations Using Supervisory Control Theory

Abstract

This paper presents a supervisory control theory based offline method for calculating restart states in a manufacturing control system. Given these precalculated restart states, an operator can be given correct instructions for how to resynchronize the control system and the manufacturing resources during the online restart process. The proposed method enables restart after unforeseen errors. It is assumed that the control system is modeled by operations and that possible operation sequences emerge through dependencies between the operations. The paper shows how reexecution requirements may be included in the calculation to obtain a correct behavior for the restarted system. In addition, it is shown how to filter out restart states that require less effort for the operator during the online restart, and how to adapt the nominal production to always enable restart in desired restart states

Supremica–An Efficient Tool for Large-Scale Discrete Event Systems

“…This is further complicated by a need to use the devices to help remove heavy work pieces. Bergagård and Fabian (2013) describe an approach based on the supervisory control theory to calculate restart states in a manufacturing control system. This supports the operator to position the devices in a state from where it is guaranteed that nominal production can continue.…”

“…This supports the operator to position the devices in a state from where it is guaranteed that nominal production can continue. As shown by Bergagård and Fabian (2013), this can be formulated as a supervisor synthesis problem, solved offline, where re-execution specifications can be included in the calculation to obtain a correct behaviour for the restarted system.…”

Calculating restart states using reset transitions

“…In earlier work, [9] and [10], an offline restart method has been proposed that handles reexecution requirements and unforeseen errors. The method is a generalization of the work presented in [3] and [6].…”

“…In [9], [10], an automata model of the control system is used during the beforehand calculation. Restart in the states that are to be evaluated as restart states are modeled by transitions from the potential error states, that is, the states where it is assumed that an error can be detected.…”

Fault Handling in PLC-Based Industry 4.0 Automated Production Systems as a Basis for Restart and Self-Configuration and Its Evaluation

“…controller synthesis) for deriving a desired restart strategy. Nevertheless, flexible manufacturing systems facilitate the production according to multiple operation sequences [25]. Therefore, Bengtsson et al [26] [27] extended the modeling concept to multiple operation sequences.…”