Center-of-Mass Estimation for a Polyarticulated System in Contact—A Spectral Approach

Abstract

This paper deals with the problem of estimating the position of center of mass for a polyarticulated system (e.g. a humanoid robot or a human body), which makes contact with its environment. The only sensors providing measurements on this point are either interaction force sensors or kinematic reconstruction applied to a dynamic model of the system. We first study the observability of the center of mass position using these sensors and we show that the accuracy domain of each measurement can be easily described through a spectral analysis. We finally introduce an original approach based on the theory of complementary filtering to efficiently merge these input measurements and obtain an estimation of the center of mass position. This approach is extensively validated in simulation using a model of humanoid robot where (i) we confirm the spectral analysis of the signal errors and (ii) we show that the complementary filter offers a lower average reconstruction error than the classical Kalman filter. Some experimental applications of this filter on real signals are also presented.

The Yoyo-Man

“…Indeed, while it is likely not the optimal control of the neck regarding balance, it is a very simple control that produces a complex behavior with significant benefits. Additional explanations for the origin of this effect, including its impact on energy consumption can be found in (Benallegue et al 2015). Figure 13.…”

On the centre of mass motion in human walking

“…To fully reconstruct the center of mass position, we used an accurate estimator recently introduced in [17]. Improving CoM reconstruction methods currently used in biomechanics [18,19] , this approach efficiently merges three different inputs: the external forces, external wrenches and the center of mass position computed from the marker positions and anthropomorphic tables [20] .…”

“…In other words, it is not possible to go beyond this quality of fitting for this state-of-theart measurement system. Moreover, even using force and moment sensors, the observability conditions of the center of mass are very weak along the direction of the contact forces [17] , which leads mostly to CoM height misestimation.…”

“…It remains that both kinematics-based and dynamicsbased approaches of CoM estimation are subject to a lot of inaccuracy sources. In [17], we recently proposed a theoretical study about the observability of the center of mass position using motion capture and force platforms. We showed that the accuracy domain of each measurement can be Fig.…”

Model-Based External Force/Moment Estimation for Humanoid Robots with no Torque Measurement

“…The reconstruction of forces and moments allows building a straight line in the Cartesian space along which the moment and the force are aligned. This axis has the minimum moment and is sometimes called the wrench central axis [7], which approximates the direction of the contact and the application point. We can compute the distance between the central axis and the real point of application p e .…”