For my midterm project in Physical Computing I decided to get, well, a little physical. In collaboration with my partners Chris and Marie, I made a robotic hand and arm that responded to the movement of an operator's hand, finger, and arm movements.This was easily the largest mechanical (see moving parts) project that I have ever worked on and presented a number of design challenges.
My responsibility was the design and build out of the mechanism that would control the hand and arm. On numerous occasions this project resulted in me starting endlessly at my hand as it grasped something or my arm as it rotated. This turned into a full fledged study of the mechanics of the hand and arm of the human body.
I started out prototyping the servo motors we used in an isolated finger system.
It was important to me that our entire system, especially the hand and fingers, were as realistic and representative as possible. I knew the prototype was not going to cut it and so started looking for alternative solutions for the fingers and hand. I knew the key would be creating an antagonistic system (similar to the one that exists in your arm) to control the fingers. Below is a video that documents a bit of the journey from one wooden finger to a system that contained 4 moveable fingers (thumb and index interacted together) and a moveable "forearm" with 2 degrees of freedom.
We eventually settled on a design that would utilize the flexibility of plastic to "passively" restore the fingers to their locked out position. The servomotors would shorten the string attached to the tip of the finger when we wanted a flexion out of a particular finger. This is extremely similar to the system and operation of the human fingers. Below is our finished product. As can be seen, we control the hand with a glove that utilizes 4 flex sensors to move the fingers and a stretch sensor to sense when the forearm is moved and Processing to sense when the entire arm is moved on the X axis.
