VIDEO: Robot does Tai Chi better than most humans - Can stay balanced when pushed upon

08/11/2016 - 22:45

iCub HumanoidRobot

This video shows the latest results on the whole-body control of humanoid robots achieved by the Dynamic Interaction Control Lab at the Italian Institute of Technology.

The control of the robot is achieved by regulating the interaction forces between the robot and its surrounding environment. The force and torque exchanged between the robot's feet and the floor is regulated so that the robot keeps its balance even when strongly perturbed.

In particular, the control architecture is composed of two nested control loops. The internal loop, which runs at 1 KHz, is in charge of stabilizing any desired joint torque. This task is achieved thanks to an off-line identification procedure providing us with a reliable model of friction and motor constants. The outer loop, which generates desired joint torques at 100 Hz, is a momentum based control algorithm with the formalism of free-floating systems subject to constraints (i.e. Differential Algebraic Equation frameworks). More precisely, the control objective for the outer loop is the stabilization of the robot’s linear and angular momentum and the associated zero dynamics. The latter objective can be used to stabilize a desired joint configuration. The stability of the control framework is shown to be in the sense of Lyapunov. The contact forces and torques at the contacts are regulated so as to break the contact only at desired configurations. Switching between several contacts is taken into account thanks to a finite-state-machine that dictates the constraints acting on the system. The control framework is implemented on the iCub humanoid robot.

Related scientific publications:

Pucci, D.; Nava, G.; Nori F.;
"An Automatic Gain Tuning Method of a Momentum Based Balancing Controller for Humanoid Robots"
Submitted to IEEE International Conference on Humanoid Robots (Humanoids). 2016

Nava, G.; Romano F.; Nori F.; Pucci, D.; 
"Stability Analysis and Design of Momentum-based Controllers for Humanoid Robots"
IEEE International Conference on Intelligent Robots and Systems (IROS). 2016

F.Nori, S. Traversaro, J. Eljaik, F. Romano, A. Del Prete, and D. Pucci
"iCub Whole-body Control through Force Regulation on Rigid Noncoplanar Contacts" 
Frontiers in Robotics and AI, 2:6 (2015)

S. Traversaro, D. Pucci, F.Nori
"On the Base Frame Choice in Free-Floating Mechanical Systems and its Connection to “Centroidal” Dynamics" 
Submitted to IEEE International Conference on Humanoid Robots (Humanoids). 2016

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