R2T2 | Devpost

Inspiration

Towards the end of school we were invited to check out the surgical arm utilized by Saint Johns hospital in Santa Monica, California. We were already deeply intrigued by new technological innovations and being able to see as well as use such an advanced piece of hardware inspired us to create a replica. Our creation, though crude compared to the real deal is intended to be a prototype to hopefully lead to a more affordable, but just as accurate version as those that exist among us already.

What it does

The arm consists of 3 joints: the shoulder, the elbow, and the wrist which all sits on a rotating turret for more coverage. The shoulder and elbow work synonymously with the use of inverse kinematics to have precise and human like movement in order to reach objects in front of it without having to meticulously adjust each joint. The wrist is able to rotate without having to make any unnecessary movements which give it an edge against its human counterpart. All these systems work to perform accurate movements based on the inputs from a gamepad

How we built it

To save money we used pre-manufactured parts in order to construct this arm. We primarily used parts from tetrix as it was readily available and cheap relative to ordering custom cnced parts. Through several iterations we finally settled on a variation we were content with and went from there.

Challenges we ran into

A few challenges we ran into which we had to solve include stability, torque, and just simple mechanical errors. Out of all these issues, the simple mechanical errors were the easiest to solve. Initially, we used a chain to move our shoulder joint, but we observed chain slippage which led to the shoulder falling randomly and not being able to hold its position which is a huge hazard in the likes of surgery. We were able to resolve this by getting rid of the whole chain system and directly attaching the gear to a motor to reduce the error margin to zero. The stability of the turret was also a huge issue. Although there is still a slight wobble, for the most part, it is extremely stable. We were able to do this by reinforcing the axle which connects to the turret gear as well as the arm. This increased stability allowed for much more precision than before. Now, for possibly the most annoying problem we had to deal with during this entire project was the torque we needed to move the elbow. Unlike the shoulder where we used a motor to move up and down, for the elbow we opted on using two servos as it was more aesthetically pleasing and lighter than a motor, however, a servo lacks strength and we had to use a huge gear ratio in order to give it the needed torque (1:16). This extremely high gear ratio was more than enough to lift what we needed, but we only had 10 degrees of movement which was not nearly enough. Through multiple tests and tweaks, we landed on a 1:8 gear ratio which was still strong enough and gave us 22 degrees of movement. Of course, we would be happier with a little more freedom, but we were content with this.

Accomplishments that we're proud of

Successfully implementing inverse kinematics.

What we learned

During this hackathon, we were able to learn the functionalities of inverse kinematics, gear ratios, and the importance of balance of torque and speed.