Backdrivable Redundantly Actuated Parallel Robot for Sensorless Physical Human-Robot Interaction
Arda Yigit, Simon Foucault, Clement Gosselin
AI summary
Problem
Serial collaborative robots suffer from high reflected inertia and loss of backdrivability due to gearboxes, while traditional parallel robots are limited by workspace singularities and require complex force/torque sensing to manage internal forces.
Approach
The authors propose a three-legged redundantly actuated parallel mechanism with base-fixed direct-drive motors, using impedance control to regulate end-effector motion and internal antagonistic forces without external sensors.
Key results
- Achieves a large, singularity-free workspace with 90° tilt and 75° torsion capabilities
- Enables sensorless control of internal antagonistic forces through actuation redundancy and low-reduction-ratio actuation
- Demonstrates high-bandwidth physical interaction with low reflected impedance and >2g accelerations in all directions
- Validates safe collaborative operation and virtual wall haptic rendering on a physical prototype
Why it matters
Simplifies collaborative robot hardware by eliminating fragile force/torque sensors while preserving safety, large workspaces, and high dynamic performance for human-robot interaction and haptics.
Abstract
This paper introduces a new redundantly ac- tuated parallel robot capable of sensorless physical human- robot interaction. Three 3-DoF legs are attached to an end- effector platform through spherical joints. This architecture alleviates most parallel singularities, thus enabling a very large workspace. The use of quasi-direct-drive actuators yields a backdrivable robot with very low impedance, since all actuators are fixed to the base. Furthermore, since the actuators are force/torque controlled, internal antagonistic forces can be controlled without additional sensing devices. Experiments are carried out on a physical prototype and validate the large workspace and physical interaction capabilities of the robot.