Flexinol as Actuator for a Humanoid Finger - Possibilities and Challenges

Abstract

Robots become more and more common in our every day lives as technology develops. Robots are normally actuated by pneumatics, hydraulics or servo motors. These technologies are mature and widely used, but other less commonly used actuators are also available. Among these we find the artificial muscle fiber Flexinol which belongs to a class of materials known as Shape Memory Alloys.

This thesis aims to implement the artificial muscle fiber Flexinol as actuator for a humanoid finger. The first part of the thesis focuses on testing of single Flexinol wires to determine in what degree these are suitable for long term use as actuators. A test frame is built to investigate contraction speed, force and displacement for wires in different setups. Among these are tests with a small dead weight, a large dead weight, an antagonistic setup and a setup with a spring working as a passive antagonistic force.

The second part of the thesis makes use of Flexinol as actuator when designing and prototyping a humanoid finger. The human finger is used as inspiration in this part, applying tendons and muscles in a human-like way. The finger is designed with CAD-software and then printed in plastic. It is then assembled with tendons and actuated with three Flexinol wires. Finally, an attempt to control the humanoid finger is done.

Specially designed software and hardware is developed through the thesis to implement working experiments. Software for both a laboratory computer and a microcontroller is written to control the system and to collect sensory data respectively.