19.6 -> Conclusions & Future Work

Results

Our team successfully created a testbench for a compliant finger mechanism capable of grasping multiple objects of varying sizes and shapes. Using the torsional spring, it successfully could transition between the two four-bar configurations, creating the effect of sequential finger bending. The gripper assembly effectively demonstrated the under-actuated, compliant nature of our design and its importance for generalizability.

Future Work

Future work can include adding sensing into the loop to determine the force imparted on objects without needing to rely on feed-forward calculations based on theory. This would also allow for more advanced and autonomous control when grasping. Another step forward on the hardware end would be to add more fingers and shape the entire design like a hand. This would better satisfy the goal of demonstrating grasping patterns and capabilities to patients rehabilitating from hand injuries.

Additionally, having a “thumb” actuate through a separate motor than the other fingers may make for a more realistic hand and better serve a goal of helping rehabilitate hand-injury patients.

Lessons Learned & Tips for Future Groups

Simulating the entire system as an assembly in CAD proved extremely important to minimize redesigns and waste, but even with this help, those steps are unavoidable. Therefore, teams should prioritize getting a working version quickly and physically iterating on details as opposed to large design overhauls closer to deadlines.

Additionally, while we were able to get a belt-driven mechanism to work without idler pulleys, it proved challenging to get the spacing between the pulleys precise enough to have tension on the belts without flexing the axles and breaking the hardware. Many of our reprints centered around tuning this distance, so adjustable idler pulleys or ditching the belt-driven design may have been a wiser move in hindsight.

We also think it would be wise to carefully consider each item purchased. In our case, we purchased some stainless steel round shafts (when we should have ordered d-shafts) which ended up causing us some slippage issues as it was difficult for the set-screws on our belt pulleys. Luckily, we were able to remedy this because another team had run into the same issue and were machining their shafts. This problem would have likely been prevented if we had consulted the TAs or machine shop staff prior to purchasing everything.

Acknowledgements

We would like to thank the professor, Dr. Symmank, and the TAs, Min-Geun Park and David Gutierrez Moreno, for their amazing support and advice during the project and mechanism design instruction prior to the project.

We would also love to shoutout the amazing people in team 6 that machined a D-shaft for us. Their help and time allowed us to resolve our slippage issue without hassle.