4.7 Conclusions & Future Work
Reflections & Takeaways
We overall accomplished our objectives of designing a robot that can play rock, paper, scissors autonomously with minimal actuation (1 motor for arm, 1 motor for fingers). Most importantly, we were able to link two slider crank systems in each finger and a specific gear ratio to create three separate position states, only using one motor.
The final demonstration went smoothly. We were able to demonstrate the full motion (arm pumping and then random state generation) as well as individually actuating all three distinct states of the palm. The states were very distinguishable, proving that we were able to create precise motion through our linkage systems. The motion was mostly realistic and recognizable as a forearm and wrist moving up and down.
To improve the design, we would make the arm linkages out of thicker acrylic or decrease the overall size of the arm 4-bar. This would increase the stability of the arm, as it tended to move side to side, while still maintaining the realism of the arm pumping motion. Additionally, we would experiment more with the motor speeds and timing so that it more closely mimicked the “rock, paper, scissors, shoot” timing. It was quite a bit slower and it would be more realistic if it changed states on the path down during the last arm pump.
Future Work
Our project could be extended by having our mechanism play rock paper scissors with a human autonomously. We would do this by including a computer vision portion that uses a camera to identify which position the human chose. It would then compare it to its own chosen position and keep score. This mechanism can also be extended to other useful applications. Finger actuation can be used to autonomously speak sign language as a translator in the future or to help operate technological devices for senior citizens.
Lessons Learned
We learned to design for assembly, considering offsets and bolt clearances, which was especially important for the moving links.
Go to the root of the design statement. For us, it was that we wanted different finger configurations. This was ultimately a phase difference problem so instead of brainstorming “how can we get these fingers to be in this position?” the question should have been phrased as “what can make a phase difference between parts?”
When working with gears, we learned the difficulty of maintaining alignment in the height of the gears and in the centers. To make this easier, we should have integrated slots in our 3D printed parts to allow for small adjustments
Tips for Future Students
Start final build as early as possible! This includes integrating with your motors to make sure the torque is sufficient. Motors do not provide as much torque as we think and when they do, they create larger deflections in cantilevered parts than we imagine.
Start testing the code early! Even if the final build is not complete, individual components can be tested separately. This can also help catch mechanical issues that might appear to work when testing manually.
Think critically about all the joints you plan to include and how they will physically fit with the rest of the mechanism.
Acknowledgements
Thank you to Dr. Symmank, and our TA’s Connor and Mila for organizing this course and coordinating build times and parts for the semester. Thank you to Connor as well for taking the time to help us develop and simplify our design!