Estimating Human Wrist Stiffness during a Tooling Task

Abstract

In this work, we propose a practical approach to estimate human joint stiffness during tooling tasks for the purpose of programming a robot by demonstration. More specifically, we estimate the stiffness along the wrist radial-ulnar deviation while a human operator performs flexion-extension movements during a polishing task. The joint stiffness information allows to transfer skills from expert human operators to industrial robots. A typical hand-held, abrasive tool used by humans during finishing tasks was instrumented at the handle (through which both robots and humans are attached to the tool) to assess the 3D force/torque interactions between operator and tool during finishing task, as well as the 3D kinematics of the tool itself. Building upon stochastic methods for human arm impedance estimation, the novelty of our approach is that we rely on the natural variability taking place during the multi-passes task itself to estimate (neuro-)mechanical impedance during motion. Our apparatus (hand-held, finishing tool instrumented with motion capture and multi-axis force/torque sensors) and algorithms (for filtering and impedance estimation) were first tested on an impedance-controlled industrial robot carrying out the finishing task of interest, where the impedance could be pre-programmed. We were able to accurately estimate impedance in this case. The same apparatus and algorithms were then applied to the same task performed by a human operators. The stiffness values of the human operator, at different force level, correlated positively with the muscular activity, measured during the same task.

A Complementary Filter Design on SE(3) to Identify Micro-Motions during 3D Motion Tracking

“…Potential applications of the proposed approach include clinical movement analysis to identify micro-motions that are clinically relevant [ 30 ] as well as tooling task, i.e., capturing kinematics of instrumented tools during manual operations then transferring human skills data to robot [ 9 , 31 , 32 ].…”

“…A variety of research has been conducted to report characteristics of selected sensor systems and/or to validate new technical devices. In industrial applications such as tooling, specific motion paths are important and unforeseen or unpredictable perturbations influence the final results [ 9 ]. Quantifying small motions is a challenging task especially in tooling tasks where vibrations or micro-motions regularly occur and affect the movement itself.…”

Human and Animal Motion Tracking Using Inertial Sensors

“…Finally, the last set of two research papers concerns industry applications [12,13]. The first one is focused on the benefit of the use of a virtual reality system to practice and improve the postural stability of workers working at height [12].…”

“…The second research paper proposed investigating the estimation of the wrist stiffness during tooling [13]. The goal of the paper is to present a model of a human manipulator performing a polishing task.…”

An Intuitive Formulation of the Human Arm Active Endpoint Stiffness

“…In that direction, the first problem to address was the estimation of the human arm endpoint stiffness or joint stiffness, so that either the real-time stiffness profiles or the underlying impedance-regulation principles can be transferred to robotic manipulators. In [ 17 ], a practical approach to estimating human wrist stiffness during tooling tasks was proposed, and the joint stiffness information was pre-programmed to allow transferring skills from expert human operators to an impedance-controlled industrial robot. Instead of only modeling the wrist stiffness, modeling human arm endpoint stiffness based on a complete arm skeleton model is more useful in practice.…”