Keeping Contact: Task-Adaptive Friction Margins for Bimanual Non-Prehensile Manipulation

Qian Ying Lee, Lin Yang, and Domenico Campolo

Nanyang Technological University

Accepted at IEEE RA-L

PDF arXiv Overview

Task-adaptive margin

No margin

Abstract

Abstract

Maintaining contact in non-prehensile manipulation requires more than nominal friction cone feasibility: a force barely inside the cone and one well inside it are both feasible, but they provide different margins against slip and contact loss.

This paper uses signed friction distance to measure friction margin in force space and derives a task-adaptive margin from the force correction needed to balance pivot moment deviations in bimanual tilting. The resulting contact margins are embedded in a sequence of second-order cone programs (SOCPs), each giving a globally optimal contact force solution at a tilt angle. The optimizer balances the object about an environmental pivot while keeping robot and pivot contact forces away from the nominal friction boundary. Optimizer-level results show interpretable force redistribution and adaptation to object property changes. Real-world experiments demonstrate successful execution under object property variations and model mismatch, while fixed margin and no-margin comparisons illustrate the importance of adapting the margin to task demand. These results support signed friction distance margins as a force planning mechanism for maintaining contact in bimanual non-prehensile manipulation.

Method

Method

The planner maps the force correction required by the task to contact-specific friction margins in force space, then optimizes contact forces that retain a finite friction margin.

Planned force marginRequired margin

Left-contact friction cone The nominal friction boundary, required margin, and optimized planned force update with tilt angle. Tangential force Normal force
Friction limit Required margin
Interactive bimanual tilting model A proportionally scaled 0.3-meter by 0.2-meter box rotates from zero to ninety degrees about an environmental pivot, with robot contacts and gravity shown. Gravity

Planned force marginRequired margin

Right-contact friction cone The nominal friction boundary, required margin, and optimized planned force update with tilt angle. Tangential force Normal force
Task force demand by tilt angle The curve shows the minimum robot contact force needed to balance the pivot moment; a marker follows the selected tilt angle. 0° 45° 90° Task demand

Results

Real Robot Experiments

Object property variation

Changes in object mass and center of mass alter the task demand; the friction margin adapts accordingly, supporting task success.

Model mismatch

Friction margin supports task success under the tested model mismatches.

Fixed margin study

To test whether a fixed margin can achieve the same outcome, we apply a matched-effort fixed margin under the CoM-mismatch condition.

Friction margin should adapt as task demand changes across the motion.

Experimental summary

Task-adaptive margin

ConditionSuccessful trials
Nominal5/5
Light object5/5
Heavy object5/5
CoM toward pivot5/5
CoM away from pivot5/5
Assumed mass −10%5/5
Assumed CoM 10% toward pivot5/5
Assumed friction +10%5/5

Fixed margin

ConditionSuccessful trials
Nominal5/5
Assumed CoM 10% toward pivot0/5

No margin

ConditionSuccessful trials
Nominal0/5

A successful trial completes the tilt while maintaining both robot contacts.

Conclusion

Task-adaptive friction margins provide a physically interpretable way to move contact force planning beyond nominal feasibility by allocating friction reserve as task demand changes.

Cite This Work

@article{lee2026keeping,
  title={Keeping Contact: Task-Adaptive Friction Margins for Bimanual Non-Prehensile Manipulation},
  author={Lee, Qian Ying and Yang, Lin and Campolo, Domenico},
  journal={arXiv preprint arXiv:2610.36961},
  year={2026}
}