D.O.M.

Project

As part of the interdiscplinary senior project, my team designed a weight lifting prosthetic for a Cal Poly wrestler named Dom Mendez. He was involved in an accident that resulted in a transhumeral amputation. He wanted a prosthetic to help workout in the gym and fill in some of the gaps left by his daily prosthetic. Specifically, he wanted to be able to do workouts that require both arms while targeting the back and shoulder muscles.

The Design

For elbow rotation, we used a linear actuator in a 3-bar expanding linkage. This was mounted to the middle of the bicep and front of the forearm. This designed sacrificed speed for a ton of strength. It also made it so that the arm was not back driveable with or without power. This makes the arm much safer and able to hold static poses for specific lifts up to more weight than the rating of the motor. We tested up to 83 lbs in a pure curling set up.

The weightlifting arm is designed to mimic Dom’s other arm. To achieve this, we used a spring-loaded potentiometer integrated into a elastic sleeve. This allowed accurate and simple mimicry of his other arm.

Somewhat last minute, we realized that we did not have enough funding to purchase the hand we wanted. We designed our own simplified version of the one we wanted to purchase. This has a spring-loaded thumb that can be opened while sliding the hand onto a bar or handle.

I was in charge of the mechanical design of the overall structure, electronics case, hand, and bicep shell.