Estimating Force Interactions of Deformable Linear Objects from Their Shapes
Qi Jing Chen, Shilin Shan, Timothy Bretl, Quang-Cuong Pham
AI summary
Problem
Existing force estimation for robot-wire interactions relies on expensive external sensors or assumes contacts only occur at the end-effector, leaving indirect or distributed interactions unaddressed.
Approach
The algorithm classifies wire segments into disturbed and undisturbed sections using geometric consistency conditions, then solves a linear system derived from force-torque balance and discrete elastic rod theory to recover external forces.
Key results
- Novel consistency conditions for classifying undisturbed versus disturbed wire sections
- Analytical linear system for estimating external force positions and magnitudes
- High estimation accuracy validated in simulation with linear computational scaling
- Successful real-world force estimation in selected robot-wire interaction scenarios
Why it matters
Enables safe, sensor-free trajectory planning and collision avoidance for robots manipulating wires or navigating wire-rich environments.
Abstract
This work introduces an analytical approach for detecting and estimating external forces acting on deformable linear objects (DLOs) using only their observed shapes. In many robot-wire interaction tasks, contact occurs not at the end-effector but at other points along the robot’s body. Such scenarios arise when robots manipulate wires indirectly (e.g., by nudging) or when wires act as passive obstacles in the environment. Accurately identifying these interactions is crucial for safe and efficient trajectory planning, helping to prevent wire damage, avoid restricted robot motions, and mitigate potential hazards. Existing approaches often rely on expensive external force-torque sensors or that contacts occur at the end-effector for accurate force estimation. Using wire shape information acquired from a depth camera and under the assumption that the wire is in or near its static equilibrium, our method estimates both the location and magnitude of external forces without additional prior knowledge. This is achieved by exploiting derived consistency conditions and solving a system of linear equations based on force-torque balance along the wire. The approach was validated through simulation, where it achieved high accuracy, and through real-world experiments, where accurate estimation was demonstrated in selected inter- action scenarios.