Morphological design methodology of rugged underactuated gripper

Abstract

The purpose of this research is to extend the design tools for robust underactuated hand design. Disaster response robots operate in highly unstructured environments where they need to dynamically move and interface to successfully fulfill their task. Historically robotic hands have been optimized for grasp strength, robustness, lightness, but not a combination of all of these factors. This thesis proposes key design requirements for disaster response robot hands and explains the design of the HERMES humanoid robotic system hand that balances these factors for versatility. Not only is it used for grasping, but a unique metal backbone allows it to be used as a foot also. Additionally, base modeling is presented for predicting the finger contact forces based on geometry of the grasp object and input tension to the hand. Trends in the number of fingers for practical disaster tasks are explored. The major purpose in the design of this hand is to be able to perform dynamic tasks such as swinging an ax which induces a moment reaction within the hand. For this loading condition, the maximum allowable reaction force scales quadratically with number of fingers, whereas tasks that only apply normal or shear forces to the hand scale linearly. The model shows that the HERMES hand can handle a 0.75 kg ax and door with 512 N of dynamic pull force. These models and design can be used for optimizing characteristics of future robotic hands, especially in the disaster response realm.