Generation of restart states for manufacturing cell controllers

A method for restart of manufacturing systems has recently been introduced. After correction of a fault, the system resumes normal production by returning to a certain restart state in the control function, and from there reexecuting parts of the work schedule. The current paper concerns automatic generation of the restart states, using discrete event systems theory. The generation process finds all possible restart states that guarantee that the execution restrictions are fulfilled during a restart, and that the production goals can be maintained. The number of restart states is minimized to reduce the number of necessary extensions to the control program.

► The paper formalizes the notion of restart states for manufacturing systems.
► Restart states guarantee all execution restrictions during and after restart.
► A novel algorithm for automatic calculation of restart states is given.
► Minimized number of restart states reduces the extensions to the control program.