Dynamically stable motion planning of wheeled robots for heavy object manipulation

Abstract

Heavy object manipulation by wheeled mobile manipulators (WMM) may lead to serious consequences such as postural instability, and this necessitates dynamically stable planning based on systematic analysis to better predict and eliminate the possibility of toppling down. Although the problem of stable planning has been extensively examined in the context of humanoid robotics, fewer research has been devoted to that in the field of WMMs. In the present study, this challenging issue is investigated for WMMs during heavy object manipulation tasks. It is assumed that the initial and final poses of a heavy payload are specified. Based on these known postures of the payload, two proper configurations for robotic system are defined. Then, between these two initial and final poses, appropriate trajectories for multiple robotic arms relative to the moving base are planned without considering the postural stability of the system. Next, motion of the moving base is planned so that the stability of the overall system is guaranteed while its predetermined initial and final positions and velocities are fulfilled. To this end, the problem of stable planning is solved as an optimization problem. The obtained results reveal the merits of the proposed approach.