Chris A. Ihrke

The Robonaut 2 hand - designed to do work with tools

The second generation Robonaut hand has many advantages over its predecessor. This mechatronic device is more dexterous and has improved force control and sensing giving it the capability to grasp and actuate a wider range of tools. It can achieve higher peak forces at higher speeds than the original. Developed as part of a partnership between General Motors and NASA, the hand is designed to more closely approximate a human hand. Having a more anthropomorphic design allows the hand to attain a larger set of useful grasps for working with human interfaces. Key to the hands improved performance is the use of lower friction drive elements and a redistribution of components from the hand to the forearm, permitting more sensing in the fingers and palm where it is most important. The following describes the design, mechanical/electrical integration, and control features of the hand. Lessons learned during the development and initial operations along with planned refinements to make it more effective are presented.

A miniature load cell suitable for mounting on the phalanges of human-sized robot fingers

It is frequently accepted that tactile sensing must play a key role in robust manipulation and assembly. The potential exists to complement the gross shape information that vision or range sensors can provide with fine-scale information about the texture, stiffness, and shape of the object grasped. Nevertheless, no widely accepted tactile sensing technology currently exists for robot hands. Furthermore, while several proposals exist in the robotics literature regarding how to use tactile sensors to improve manipulation, there is little consensus. This paper describes the electro-mechanical design of the Robonaut 2 phalange load cell. This is a miniature load cell suitable for mounting on the phalanges of humanoid robot fingers. The important design characteristics of these load cells are the shape of the load cell spring element and the routing of small-gauge wires from the sensor onto a circuit board. The paper reports results from a stress analysis of the spring element and establishes the theoretical sensitivity of the device to loads in different directions. The paper also compares calibrated load cell data to ground truth load measurements for four different manufactured sensors. Finally, the paper analyzes the response of the load cells in the context of a flexible materials localization task.