Experimental Validation of Contact Dynamics for In-Hand Manipulation

TL;DR

This study rigorously tests contact models used in in-hand robotic manipulation, revealing their strengths and limitations in predicting forces and motions during primitive contact actions.

Contribution

It provides a comprehensive experimental validation of contact models, highlighting their effectiveness and key limitations in complex contact scenarios.

Findings

Contact models based on Coulomb's law are effective for first-order predictions.

Major limitations include non-uniqueness of force resolution and unmodeled contact compliance.

Experimental data exposes the gap between model predictions and real-world contact behavior.

Abstract

This paper evaluates state-of-the-art contact models at predicting the motions and forces involved in simple in-hand robotic manipulations. In particular it focuses on three primitive actions --linear sliding, pivoting, and rolling-- that involve contacts between a gripper, a rigid object, and their environment. The evaluation is done through thousands of controlled experiments designed to capture the motion of object and gripper, and all contact forces and torques at 250Hz. We demonstrate that a contact modeling approach based on Coulomb's friction law and maximum energy principle is effective at reasoning about interaction to first order, but limited for making accurate predictions. We attribute the major limitations to 1) the non-uniqueness of force resolution inherent to grasps with multiple hard contacts of complex geometries, 2) unmodeled dynamics due to contact compliance, and 3) unmodeled geometries dueto manufacturing defects.