CoPaRo: A Compact, Backdrivable 6-DOF Hybrid Parallel Robot with Serial-Like Form Factor and Large Workspace
Samuel Verret, Clement Gosselin
AI summary
Problem
Parallel robots typically suffer from limited workspaces and large footprints, while serial robots struggle with backdrivability and high inertia, creating a trade-off that hinders safe physical human-robot interaction.
Approach
The authors propose a two-leg hybrid parallel architecture with coaxial base joints to generate an axisymmetric workspace, combined with base-mounted actuators and direct-drive joints to minimize inertia and enable backdrivability.
Key results
- Novel 6-DOF hybrid parallel robot architecture with a compact footprint and large axisymmetric workspace
- Complete analytical solutions for forward and inverse kinematics
- Comprehensive singularity analysis identifying all type I, II, and III conditions
- Demonstration of a workspace-to-footprint ratio comparable to serial robots
Why it matters
Provides a practical robotic platform that combines the speed and rigidity of parallel mechanisms with the safety and fluidity required for direct human interaction.
Abstract
A novel, compact, backdrivable 6-degree-of- freedom (DOF) hybrid parallel robot with a large axisymmetric workspace is proposed, referred to as CoPaRo, short for Compact Parallel Robot. The architecture achieves a high workspace-to-footprint ratio comparable to that of serial robots. The proposed robot is well suited for physical human-robot interaction (pHRI) due to its low inertia, backdrivability, and large workspace. A complete kinematic analysis is provided, including forward and inverse kinematics and velocity equa- tions. All singularity conditions of the proposed architecture are identified, and the complete usable workspace is presented, accounting for singularities, mechanical interferences, and nu- merical stability. A CAD model and computer animations of the robot are provided to illustrate its motion, highlighting both the compact footprint and the large workspace. The actuators are positioned close to the base and transmit motion to distal joints via pulleys to reduce the robot’s inertia. Direct-drive or quasi- direct-drive actuators can be used to enable backdrivability.