Zero Wrench Control via Wrench Disturbance Observer for Learning-free Peg-in-hole Assembly

TL;DR

This paper introduces a Dynamic Wrench Disturbance Observer (DW-DOB) that enables highly sensitive, stable, and robust zero-wrench control in contact-rich robotic manipulation, validated through industrial peg-in-hole experiments.

Contribution

The paper presents a novel DW-DOB that incorporates task-space inertia for improved sensitivity and stability in zero-wrench control, outperforming conventional observers in precision tasks.

Findings

Deeper, more compliant peg insertions achieved.

Minimal residual wrenches during contact.

Outperforms conventional disturbance observers.

Abstract

This paper proposes a Dynamic Wrench Disturbance Observer (DW-DOB) designed to achieve highly sensitive zero-wrench control in contact-rich manipulation. By embedding task-space inertia into the observer nominal model, DW-DOB cleanly separates intrinsic dynamic reactions from true external wrenches. This preserves sensitivity to small forces and moments while ensuring robust regulation of contact wrenches. A passivity-based analysis further demonstrates that DW-DOB guarantees stable interactions under dynamic conditions, addressing the shortcomings of conventional observers that fail to compensate for inertial effects. Peg-in-hole experiments at industrial tolerances (H7/h6) validate the approach, yielding deeper and more compliant insertions with minimal residual wrenches and outperforming a conventional wrench disturbance observer and a PD baseline. These results highlight DW-DOB as a practical learning-free solution for high-precision zero-wrench control in contact-rich tasks.