Pose-robust design improves force and speed in human-sized robot hands
PACT: Pose-Robust Actuation Co-Design for Tendon-Driven Robotic Hands
Robotics
Summary
Robot hands that mimic human hands need to be strong, quick, and responsive, but creating such hands is challenging because moving parts must work together perfectly. The authors developed a method called PACT that plans how tendons and motors inside a robot hand should be arranged to keep performance consistent across different hand positions. Their approach balances force and speed needs simultaneously, rather than one after the other, resulting in a robot hand design that works well in many poses and fits human hand size. Tests on a prototype showed results close to their predictions, indicating this method can help build more capable robotic hands.
What this means in practice
- •For robotics engineers: Design human-sized robotic hands with consistent force and speed across various hand poses using optimized tendon and actuator layouts.
- •For prosthetics developers: Create more natural-feeling and responsive prosthetic hands by co-optimizing tendon routing and actuator parameters to meet force and speed needs in different hand configurations.
Authors
Prashant Kumar, Rachael Granberry, Taylor Niehues, Andrew A. Stanley, Gabe Pirie
Abstract
Humanoid robotic hands must provide sufficient force, speed, and backdrivability within a human-scale envelope. Tendon-driven transmissions address this challenge by relocating actuators to the palm and forearm, but routing paths, moment arms, and capstan dimensions jointly determine both force capability and joint speed, so selecting them sequentially satisfies one requirement at the expense of the other. This paper presents a pose-robust actuation co-design for tendon-driven robot hands (PACT) framework that optimizes tendon routing, moment arms, and capstan dimensions under pose-dependent force requirements and drivetrain-bandwidth constraints. A feasible-force formulation enforces actuator bounds and equilibrium at all joints, while a max-min objective maximizes task-force coverage at the weakest pose. Applied to a four-degree-of-freedom finger, the framework produces an asymmetric N + 1 tendon topology using quasi-direct-drive actuators. Across eight poses, the design achieves task-force coverage of 0.88-1.00 and a predicted 5 Hz minimum isolated-joint flexion/extension bandwidth within a 70th-percentile human-size envelope. Prototype measurements deviate from predictions by up to 24.5%, primarily due to unmodeled transmission losses. These results indicate that co-designing routing with the drivetrain can meet pose-dependent force requirements without relaxing the bandwidth constraint, paving the way for human-sized robotic hands with human-level performance.