Reentrant FMS scheduling in loop layout with consideration of multi loading-unloading stations and shortcuts

The scheduling problem in flexible manufacturing
systems (FMS) environment with loop layout configuration
has been shown to be a NP-hard problem. Moreover, the improvement
and modification of the loop layout add to the
difficulties in the production planning stage. The introduction
of multi loading-unloading points and turntable shortcut resulted
on more possible routes, thus increasing the complexity.
This research addressed the reentrant FMS scheduling
problem where jobs are allowed to reenter the system and
revisit particular machines. The problem is to determine the
optimal sequence of the jobs as well as the routing options. A
modified genetic algorithm (GA) was proposed to generate
the feasible solutions. The crowding distance-based substitution
was incorporated to maintain the diversity of the population.
A set of test was applied to compare the performance of
the proposed approach with other methods. Further computational
experiments were conducted to assess the significance
of multi loading-unloading and shortcuts in reducing the
makespan, mean flow time, and tardiness. The results
highlighted that the proposed model was robust and effective
in the scheduling problem for both small and large size
problems