Zone-Control-Based Traffic Control of Automated Guided Vehicles

A Control of Collision and Deadlock Avoidance for Automated Guided Vehicles with a Fault-Tolerance Capability

“…However, for large-scale AGV systems, the potential room for performance improvement using bidirectional guide-path systems shrinks with increasing vehicle interferences ( [39,29]) and comes with a sharp rise of complexity of traffic management. Furthermore, one also notes that the traffic control with bidirectional guide-path in general depends on the scheduling and routing of the vehicles, whereas the traffic control algorithm proposed in our previous work [2] has been proven able to avoid deadlocks with no restrictions to routing of the vehicles, as long as each vehicle visits a finite sequence of zones from its initial location to a depot (where it can stay without blocking other vehicles). This free-routing property is definitely a big advantage in achieving high system performance.…”

“…This free-routing property is definitely a big advantage in achieving high system performance. Note also that among the algorithms proposed in [35,36,2], only the one in [2] is provably correct in guaranteeing the absence of deadlocks with the help of a formal event-based modelling. (The problems with the algorithms in [35] have been pointed out in [21]; in [36] the authors did not obtain a complete solution for what they call "multi-cycle deadlocks".…”

“…However, it seems that there is still quite some distance from the current status of the development to the practical applications of these optimal algorithms for large-scale AGV systems (with tens or even hundreds of vehicles). To the authors' best knowledge, the deadlock avoidance algorithms proposed in [35,36,1,2] have the smallest computational complexities, which only quadratically increase with the number of vehicles. Note that the small complexities of these algorithms partially come from their limited applicability to guide-path systems with only unidirectional lanes.…”

“…[34] suggested a traffic control approach based on the concept of "semaphore" borrowed from computer science. In addition, inspired by [35], the work of [36] and later [1] (with core models and algorithms reformed in [2]) showed deadlock detection and avoidance schemes involving some online cyclic deadlock checking procedures for a unidirectional guide-path system.…”

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AbstractBased on a novel discrete-event zone-control model, in our previous papers [1,2], we presented a time-efficient traffic control for automated guided vehicle (AGV) systems to exclude inter-vehicle collisions and system deadlocks, together with a case study on container terminals. The traffic control allows each vehicle in an AGV system to freely choose its routes for any finite sequence of zone-tozone transportation tasks and the routes can be constructed in an online fashion.

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