A Whole-Body Model Predictive Control Scheme Including External Contact Forces and CoM Height Variations
This work addresses the challenge of enabling humanoid robots to perform complex tasks involving external contacts, representing an incremental improvement over existing methods for walking on flat terrain.
The paper tackles the problem of generating diverse whole-body motions for humanoid robots by extending Model Predictive Control to plan for vertical Center of Mass motion and external contact forces, enabling automated contact selection and timing in multi-contact scenarios, with validation through simulations and experiments.
In this paper, we present an approach for generating a variety of whole-body motions for a humanoid robot. We extend the available Model Predictive Control (MPC) approaches for walking on flat terrain to plan for both vertical motion of the Center of Mass (CoM) and external contact forces consistent with a given task. The optimization problem is comprised of three stages, i. e. the CoM vertical motion, joint angles, and contact forces planning. The choice of external contact (e. g. hand contact with the object or environment) among all available locations and the appropriate time to reach and maintain a contact are all computed automatically within the algorithm. The presented algorithm benefits from the simplicity of the Linear Inverted Pendulum Model (LIPM), while it overcomes the common limitations of this model and enables us to generate a variety of whole-body motions through external contacts. Simulation and experimental implementation of several whole-body actions in multi-contact scenarios on a humanoid robot show the capability of the proposed algorithm.