Simple gripper model helps robots fold cloth realistically
A Simple Gripper Interface for Simulator-Agnostic Cloth Manipulation
Robotics
Summary
Robots have trouble grasping and folding cloth because cloth moves in complex ways. The authors created a simple model for robot grippers that picks up cloth by selecting cloth points inside a virtual grasping area without worrying about friction or contact details. This model works in lots of simulation systems and can also control a real robot to fold cloth, making it easier to test and deploy cloth manipulation methods.
What this means in practice
- •For robotics engineers: Control robot arms to pick and fold cloth in simulation and real-world tasks using an easy-to-implement gripper model.
- •For virtual environment developers: Add realistic cloth grasping interactions in different simulators without detailed friction models by using a simple positional constraint approach.
Authors
Abhilash Nayak, Franco Coltraro, Maria Alberich-Carramiñana, Carme Torras
Abstract
This paper presents a grasping model for cloth manipulation specifically tailored to ease the deployment of robotic control methods. The model is robust, fast and easy to implement avoiding at the same time contact and friction considerations between the gripper and the cloth in favor of simple positional constraints. The gripper is described by its pose, jaw state, and an attached grasping volume. Two kinds of grasping volumes are considered: an axis-aligned box to simulate a pinch grasping and a square pyramidal volume to simulate point grasping. When the gripper closes, the discrete cloth positions lying inside this volume are selected, stored in the local gripper frame, and then transported with the gripper motion. A simple squeezing step is also included to progressively move the selected cloth positions toward the center of the grasping region, avoiding an instantaneous displacement at closure. The model can be used in any simulator as it only requires access to discrete cloth positions and a mechanism for imposing target positions as constraints. We implement our grasping model in conjunction with a constraint-based inextensible cloth simulator, where grasping is implemented as moving positional equality constraints coupled with stretch, shear, collision, and table contact projection steps. The same gripper trajectory is applied on a robot arm to fold a real piece of cloth, serving as a simple bridge between simulation and physical cloth manipulation and showcasing the realism and practicality of our idealized grasping model.