String algebra-based approach to dynamic routing in multi-LGV automated warehouse systems

This paper presents a dynamic routing method for supervisory control of multiple laser guided vehicles (LGVs) that are traveling within a layout of a given warehouse. In dynamic routing a calculated path particularly depends on the number of currently active LGVs´ missions and their priorities. In order to solve the shortest path problem dynamically, the proposed routing method uses the string matrix composition and time windows in a vector form. For each mission requested by the supervisor, the string composition algorithm first finds the candidate paths and then checks if they are feasible. The feasibility of a particular path is evaluated by insertion of appropriate time windows and by performing the windows overlapping tests. The algorithm resolves the time windows conflicts iteratively by inserting new time windows until the conflicts disappear or remain present only on the path´s origin arc, which means that the found candidate paths are not feasible. The use of time windows makes the algorithm apt for other scheduling and routing problems. The proposed method has been successfully tested in the industrial environment and the results are presented