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http://dx.doi.org/10.5302/J.ICROS.2008.14.9.886

On the Estimation of the Center of Mass of an Autonomous Bipedal Robot  

Kwon, Sang-Joo (한국항공대학교 항공우주기계공학부)
Oh, Yong-Hwan (한국과학기술연구원 인지로봇연구센터)
Publication Information
Journal of Institute of Control, Robotics and Systems / v.14, no.9, 2008 , pp. 886-892 More about this Journal
Abstract
In this paper, a closed-loop observer to extract the center of mass (CoM) of a bipedal robot is suggested. Comparing with the simple conversion method of just using joint angle measurements, it enables to get more reliable estimates by fusing both joint angle measurements and F/T sensor outputs at ankle joints. First, a nonlinear-type observer is constructed to estimate the flexible rotational motion of the biped in the extended Kalman filter framework. It adopts the flexible inverted pendulum model which is appropriate to address the flexible motion of bipeds, specifically in the single support phase. The predicted estimates of CoM in terms of the flexible motion observer are combined with measurements (that is, output of the CoM conversion equation with joint angles). Then, we have final CoM estimates depending on the weighting values which penalize the flexible motion model and the CoM conversion equation. Simulation results show the effectiveness of the proposed algorithm.
Keywords
biped; humanoid; CoM(Center of Mass); ZMP; observer; Kalman filter;
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