Shuffle motion for humanoid robot by sole load distribution and foot force control

Abstract

In situations where humanoid robots with constrained posture walk through a narrow space (e.g. manufacturing plants and kitchens), shuffling motions that are stepless and possess wide foot supporting area are effective. One of the difficulties of humanoid's shuffle translations is the load distribution between both feet. If sole loads are not distributed appropriately, the humanoid robot cannot maintain target contact states of each foot, and it will result in slipping both feet or falling down. In this paper, we propose Slide Friction Control (S.F.C.): offline pattern generator and Slide Contact Stabilizer (S.C.S.): online controller. First, Slide Friction Control determines reference foot forces and COM trajectories by adjusting sole loads and considering kinematic friction. The appropriate load distribution of S.F.C. enables humanoid robots to maintain target foot contact states. Second, Slide Contact Stabilizer controls each foot by using damping control to realize reference foot forces determined by S.F.C. S.C.S. enables humanoid robots to slide foot smoothly by suppressing friction vibrations. We also take into consideration the dynamic balance of humanoid robots such as previous waking stabilizers. Finally, we demonstrate that the proposed system enables humanoid robot to slide their feet smoothly using a life-sized humanoid robot, HRP-2.