Cycle time optimization of a reversible A/DML served by a mobile robotic system

Abstract

This paper presents a new cycle time optimization (CTO) approach for an assembly/disassembly mechatronics line (A/DML) served by a wheeled mobile robot (WMR) equipped with a robotic manipulator (RM). The mobile robot serves A/DML during disassembling for transporting carry the disassembled components from disassembling locations to the corresponding storage warehouse in order to be reused. Disassembling starts if the final product fails the quality test. The cycle time results from adding up the durations of A/D sequences. Since the elementary assembly operations have constant durations (determined by the duration of the each assembly operation and the displacement duration of transporting line at constant speed, between successive workstations), the problem of cycle time optimization concerns only disassembling. During the disassembly, a repetitive sequence can be identified with a single disassembling stage served by WMR equipped with RM. In this case, an elementary cycle time (ECT) optimization is the maximum value between the following time durations: a) time duration of disassembling and transporting remaining piece towards next station; b) time duration of the RM for gripping and storage disassembled part and WMR's displacement. For the events synchronization are inserted the time intervals between: the displacement with constant speed within/between work stations and the manipulations/displacements of the robotic system. For setting time durations and joining the discrete dynamics of the mechatronics line with the continuous dynamics of the robotic system, a Synchronized Hybrid Petri Nets (SHPN) model running autonomously has been used.