# Static Stability of Robotic Fabric Strip Folding

## TL;DR

This paper investigates the static stability of fabric strip folding by robots, identifying instabilities that affect manipulation accuracy, and evaluates different folding methods considering these stability issues.

## Contribution

It introduces the concept of static instability in robotic fabric folding, verified through simulation and experiments, and assesses existing folding methods under these stability constraints.

## Key findings

- Static instability occurs during fabric folding.
- One folding path is suitable for fabrics with internal friction.
- A dynamic folding path exists for ideal elastic materials.

## Abstract

Planning accurate manipulation for deformable objects requires prediction of their state. The prediction is often complicated by a loss of stability that may result in collapse of the deformable object. In this work, stability of a fabric strip folding performed by a robot is studied. We show that there is a static instability in the folding process. This instability is detected in a physics-based simulation and the position of the instability is verified experimentally by real robotic manipulation. Three state-of-the-art methods for folding are assessed in the presence of static instability. It is shown that one of the existing folding paths is suitable for folding of materials with internal friction such as fabrics. Another folding path that utilizes dynamic motion exists for ideal elastic materials without internal friction. Our results show that instability needs to be considered in planning to obtain accurate manipulation of deformable objects.