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Current testing standards for prosthetic feet fail to consider how well prosthetic feet mimic the biomechanics found in anatomical human ankles in a natural walking cycle. To account for this, our client, Dr. Mark Pitkin, seeks to establish a measurable standard known as the Index of Anthropomorphicity(IA). For prosthetic feet, the IA quantifies the concavity or convexity of the moment-angle relationship in a prosthetic foot. This has to do with the moments required to deflect a prosthetic leg to a corresponding angle of deflection.
In order to establish this standard, a means to reliably and accurately measure moment-angle data in a prosthetic foot during a walking cycle is necessary. Our goal for this project was to develop a testing rig for prosthetic feet that applied axial and tangential forces to simulate the dynamic loading seen on a foot during a walking or gait cycle and measure the moment generated at the ankle at a corresponding angle of deflection to characterize the IA for a range of prosthetic feet.
We went through a lot of iteration for this design. There were 4 main concepts that we designed for:
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These are some initial results from our test rig. We tested the Willowwood Meta Flow foot which was designed to have a more compliant behavior that mimics the behavior seen in anatomical ankles. As can be seen in the figures, a normal anatomical ankle exhibits a concave curvature, similarly to the MF foot.
Looking further into our results specifically, we recorded the axial forces that we applied and the bending perpendicular force at a corresponding angle of deflection. From this we were able to calculate the moment generated about the ankle and normalize based on a simulated human body weight that we input in our program.
The only real noninvasive treatment for CTS is wrist splinting, where the idea is that studies have shown that internal pressure of the median nerve is at its lowest when the wrist is maintained in a neutral position. That being said, studies have also shown that the effectiveness of using a wrist splint as a treatment for CTS is unclear.
Knowing this, we considered the idea that wrapping a splint around the wrist leads to external compression of the Carpal Tunnel and negating effects of holding the wrist neutral. We also consider the impact of different rigid splint insert designs on pressure on the Carpal Tunnel relative to other proints around the wrist.
There were two main components to this experiment that we developed. The different rigid splint insert designs we were testing, and the wrist splint that we modified to record pressure at points on the wrist. For this we used a commercially available wrist splint marketed for CTS treatment.
For my Computer Aided Product Design final project I was tasked to make a model and assembly of anything I wanted in Solidworks. I decided to be a bit ambitious for this project, but these were the few requirements:
The system works as follows:
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I worked on the lid team because I thought the mechanical challenge of the force necessary to puncture the pod was be interesting. We initially considered a linkage system and a gear train to achieve the necessary force, but we ended on a much more elegant design, using a strong linear actuator in a simple linkage to open and close the lid.
To fix the end of the linear actuator onto the tip of the lid and since the lid itself was a solid metal material we needed to develop a strong connection link. After much iteration we landed on a custom clevis mad up of two pieces of waterjet cut aluminum sheet bent around the lid and held in place by a notch sawed out of the lid. The linear actuator is attached with a threaded rod fed through the holes and held in place with nuts.
Since this was a pretty load heavy process, it was important to fix everything in place firmly. We also developed a lofted base to prop up the espresso machine to an operational height for Transport Team. We used a series of 80-20s to mount the linear actuator and then bolted the whole system to the plywood base we were working on.
We were able to successfully make a latte for a customer, though not without a few issues. Button team ended up having some last minute issues with relays which resulted in some manual value updating during the demo. We also intended to be able to make 3 lattes in sequence for the demo, but after the first successful cup, the pods in the espresso machine jammed, leading to the hinge of the lid failing under the force of the linear actuator. This was the unfortunate end to the Robot Cafe, since there was no easy fix.
I do think there were a couple of things that we could have done to prevent this. While working on this, my sub-team and I debated implementing limit switches to ensure that the lid was being opened and closed all the way. Since we felt like we were constantly dealing with different issues, this ended up not being prioritized as it should have. The pods in the machine ended up getting jammed because the lid did not open far enough to drop the used pod from the first latte and I do think limit switches would have prevented.
That being said I am still very proud of the results of this project. I think the team coordination of this project was very impressive given the scope and I'm very proud of my team and how it came together.
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For my final prototype, I decided to try a couple of things a little differently.
In order to not rely on solely the programming for the speed reduction, I also used a 1:4 ratio bevel gear tat I 3D printed. This meant that the motor would not need a helping hand to start, and that the housing box could be much more slim. I took this opportunity to laser cut it out of a matte black acrylic with spots for more LEDs, a start button, and a buzzer.
I also tried using the capacitive touch pins on the microcontroller I was using. This meant that the wire would not just be an open circuit, and instead would be sensing for an electric field, much like a phone screen. This meant that as long as the loop of the wand was conducting with the electricity running through the players' hand, the game would operate as normal, without the wand needing to be attached by a wire. This meant that any kind of nudge on the wire from the players' hand or from the wand would trigger a game over sequence.
I added a start button that would initiate the game, so that it is not constantly running and it can sit idle so long as the microcontroller has power and the motor is connected to a 12V power source. I also added a buzzer that added a bit more drama when a player loses the game and so that it lives up to its namesake.
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My name is Marinez Jose, but you can call me Nezy, and I'm a Senior studying my Undergrad in Mechanical Engineering at Tufts University. The core of my motivation stems from my sheer love of creating. For much of my life this fostered into a passion for the fine arts and has shifted gears to engineering. This continues to drive my engineering work and I feel is apparent in many of my designs. Right now I'm very interested in working in robotics, medical devices, and consumer electronics.
