Rotational Sliding Motion Generation for Humanoid Robot by Force Distribution in Each Contact Face

Abstract

Recent studies have explored humanoid robots in contact with the environment in various ways. However, many of them assumed static rather than sliding contacts. Studies on humanoid shuffle motion planning have realized sliding motions, such as turning, but relied on quasi-static balance control. In this letter, we propose a dynamic balance control method for sliding contact motions. The proposed method consists of the distributed force contact constraint (D.F.C.C.), which describes rotational sliding contact constraints, and the slide friction control (S.F.C.), which controls humanoid dynamic balance based on the model predictive control by using the D.F.C.C. The D.F.C.C. segments a contact face into a grid of contact points and optimize the vertical component of the contact forces. This enables us to calculate the sliding friction forces at each contact point. The S.F.C. is the model predictive control for distributing contact forces to each contact face considering sliding frictional dynamics. The D.F.C.C. is simple and easy to apply to the S.F.C. In our online stabilizer, we control not only a ZMP, but also contact forces for realizing the contact force distributions planned in the S.F.C. Finally, we show our method's validity through the experiment using life-sized humanoid robot JAXON.