On Inverse Inertia Matrix and Contact-Force Model for Robotic Manipulators at Normal Impacts

TL;DR

This paper develops impact dynamics models tailored for fixed-base robotic manipulators during orthogonal impacts, incorporating experimental data to improve contact-force modeling and inverse inertia matrix computation.

Contribution

It introduces a viscoelastic contact-force model and a method for computing the inverse inertia matrix specific to fixed-base manipulators during impacts.

Findings

Viscoelastic contact-force model best fits experimental data.

Inverse inertia matrix computed assuming the robot as a composite-rigid body.

Experimental validation with 150 impact trials.

Abstract

State-of-the-art impact dynamics models either apply for free-flying objects or do not account that a robotic manipulator is commonly high-stiffness controlled. Thus, we lack tailor-made models for manipulators mounted on a fixed base. Focusing on orthogonal point-to-surface impacts (no tangential velocities), we revisit two main elements of an impact dynamics model: the contact-force model and the inverse inertia matrix. We collect contact-force measurements by impacting a 7 DOF Panda robot against a sensorized rigid environment with various joint configurations and velocities. Evaluating the measurements from 150 trials, the best model-to-data matching suggests a viscoelastic contact-force model and computing the inverse inertia matrix assuming the robot is a composite-rigid body.