Balsa Wood Hand
The first iteration of the robotic hand was constructed from pins, sticks of balsa wood, thread, and rubber bands. This iteration was inspired directly from the anatomy of a real hand.
EMG Sensor Retrofit
The following video is of the first balsa wood hand I build. In the video I've retrofitted it with EMG muscle sensors.
Robotic Hand iterations
Iteration One (Balsa Wood)
I started my hand iterations when I was in thirteen. What first inspired me to start building hand models was a mix of a few different experiences. In San Francisco at a wax museum, I got a replica of my hand made. The detail amazed me, but I just wanted it to move. The muscle actuation in the movie iRobot inspired the finger articulation, which I eventually constructed from thread to resemble tendons. I built the hand initially from balsa wood, pins, and glue. The pulley system that moved the fingers was modeled off of the tendon structure found in a human anatomy book. I decided to use a Servomotor as a source of automated motion, because I could change the speed and position at which the hand would operate. To operate the Servomotor, I programmed a parallax micro-controller to move to specific coordinates, thereby simulating the opening and closing of the hand. I attached the instructions to its construction online, which you can see here.
Iteration Two ABS (3D Printed)
I was able to improve upon the old design by applying the coding principles of my computer science class and the 3D design concepts of my computer aided design class to create a new model. After designing the 3D files for the hand using Autodesk Inventor, I was able to use the school's resources to 3D print the hand in the physical world. The new model consists of a completely redesigned hand structure that holds two micro Servomotors in the palm of the hand to reduce clutter. The Servomotors close the hand when the reading off of Arduino based EMG sensors surpasses a preset trigger value. The Servomotors release, and the hand reopens after the user relaxes the forearm or bicep. I released the designs on thingeverse.com as open source so that others can build, improve upon, and benefit from my work.
Open Source Finger Model
This iteration of the animatronic hand was centered on the idea of assembly. There are only three parts made to assemble each finger. By mixing long, medium, and short lengths, I was able to create the specific length of each finger. After assembling each finger, the user is able to snap it onto the palm of the hand. Three different motor mounts provide differentiated actuation for the pointer and middle finger, middle and ring finger, and thumb. The EMG muscle control interface (Prosthetic Hand i2) would be used in a full production model of this hand. This model is focused more on the reproduction and open source construction of the design rather than functionality.
Iteration Three (Single print finger assembly execution)
The fourth iteration of the animatronic hand project is
focused on finger function. With access to a 3D printer that uses PVA water-soluble supports, I was able to circumvent designing for ease of assembly. Because I was able to produce fully functional moving parts directly out of the printer, the parts were designed only for functionality rather than assembly. With half a millimeter of clearance between parts, the joints of the fingers moved smoothly after a lye and warm water solvent bath. This design is focused more on maximizing utility of the industrial printer at our school. A standard consumer printer would have difficulty printing two materials with such definition and accuracy.