Multi-Contact Locomotion Planning With Bilateral Contact Forces Considering Kinematics and Statics During Contact Transition

Abstract

In this letter, we propose a multi-contact locomotion planning framework for a humanoid robot to traverse complex environments utilizing bilateral contact forces with reasonable computational time. We hypothesize that a bilateral contact can be approximated by a pair of surface contacts, and expand the static CoM feasible region by this assumption, which we define as bSCFR. This assumption enables us to project centroidal statics with bilateral contact forces to a constraint on whole-body kinematics. Then, we formulate the whole-body inverse kinematics problem for all the discretized frames in the target contact transition as one optimization problem with bSCFR and CoM regularization, which can find feasible whole-body configurations while considering both kinematics and statics. After solving whole-body inverse kinematics, the contact forces are computed based on the centroidal statics, where appropriate bilateral contact forces are automatically generated according to the resulting CoM positions. We experimentally confirm that our proposed framework enabled HRP-5P to traverse steep stairs utilizing bilateral contact forces in the real world, and conclude that it expands the multi-contact locomotion capability of a humanoid robot.