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Publication Details

Reference TypeJournal Article
Author(s)Righetti, L. and Buchli, J. and Mistry, M. and Kalakrishnan, M. and Schaal, S.
TitleOptimal distribution of contact forces with inverse dynamics control
Journal/Conference/Book TitleInternational Journal of Robotics Research
Keywordsinverse dynamics; floating base; nonlinear control; legged robot
AbstractThe development of legged robots for complex environments requires controllers that guarantee both high tracking performance and compliance with the environment. More specifically the control of the contact interaction with the environment is of crucial importance to ensure stable, robust and safe motions. In this contribution we develop an inverse-dynamics controller for floating-base robots under contact constraints that can minimize any combination of linear and quadratic costs in the contact constraints and the commands. Our main result is the exact analytical derivation of the controller. Such a result is particularly relevant for legged robots as it allows us to use torque redundancy to directly optimize contact interactions. For example, given a desired locomotion behavior, we can guarantee the minimization of contact forces to reduce slipping on difficult terrains while ensuring high tracking performance of the desired motion. The main advantages of the controller are its simplicity, computational efficiency and robustness to model inaccuracies. We present detailed experimental results on simulated humanoid and quadruped robots as well as a real quadruped robot. The experiments demonstrate that the controller can greatly improve the robustness of locomotion of the robots.
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