A Lightweight and Versatile Prosthetic Hand for Daily Grasping

Area of Science:

• Robotics
• Biomedical Engineering
• Mechanical Engineering

Background:

• Developing lightweight, low-complexity prosthetic hands is crucial for meeting daily grasping needs.
• Existing prosthetics often face challenges with limited actuation, tendon slack, and inconsistent stroke length.

Purpose of the Study:

• To propose an underactuated multi-finger prosthetic hand with transmission-control co-design.
• To achieve predictable multi-joint synergies and stable grasps under lightweight and low-complexity wearable constraints.

Main Methods:

• The prototype features six miniature motors driving 14 DOFs, with tendon-driven underactuated joints and independently controlled thumb DOFs.
• Active/passive tendon-length constraints and chord-to-arc mapping address tendon inconsistencies.
• A layered controller with rotation limits and speed-decay detection provides per-finger termination and overdrive protection without sensors.

Main Results:

• The prosthetic hand has a total mass of 176.6 g and a peak driving force of approximately 2.8 N per finger.
• It successfully reproduces 24 out of 33 grasp types (72.7%) according to the Feix GRASP taxonomy.
• Stable grasp formation was achieved across objects with varying geometries, including power, pinch, and precision grasps.

Conclusions:

• The proposed underactuated prosthetic hand offers a viable solution for daily grasping needs within wearable constraints.
• The transmission-control co-design enables predictable synergies and stable grasps, demonstrating high functional coverage.
• This design advances prosthetic hand technology by achieving significant grasp capabilities with reduced complexity and weight.