Projects
UW BioMechatronics Exoskeleton Team (Exo)
UW Biotron's newest team is Exo, a team building a soft lower body exoskeleton, meaning the exoskeleton supports the legs without touching the ground and taking weight itself. The exoskeleton is competing in the Applied Collegiate Exoskeleton (ACE) competition in May. In Exo, I'm on the Electrical, Mechanical, and Operations subteams. In Operations I've made promotional material, merchandise, and kept the minutes and notes of my other subteam meetings, but in electrical and mechanical, I've done a few projects.
Battery Pack
My first and still ongoing project is a battery pack, which involves both the Mechanical and Electrical teams. This is a component that sits on the lower back, and it must have enough space for the batteries, battery management system (BMS), circuit boards, and fans. This means the batteries need to be configured so that they can be easily accessed while taking as little space as possible. So, in the final CAD model, the battery block is on rails. Above them is the BMS. There is also plenty of space to add fans or circuits in front of the batteries.
The batteries themselves have recently changed, and the new ones have different dimensions. So, the pack needs to be slightly redesigned, and then it can be manufactured and assembled.
Power Electronics
Since the start of the winter semester, I've been working on the power electronics for the exoskeleton, making multiple PCB schematics and layouts that will eventually be coalesced into one power board, that all the sensors, motors, and microcontrollers of the skeleton will be connected to.
My first PCB was a 5V to 3V3 LDO. It's a relatively simple circuit, but it's needed to power the IMUs and microcontroller board. I had also never used Altium or LTSpice before, so it was a good opportunity to learn the software I would be using for the rest of the boards. I found the components on Digikey, researched how to connect them together, and then made a schematic. After testing it in LTSpice, I made the layout in Altium.
Once the LDO was finished and validated, I started working on my current project, which is a 28V to 5V buck converter. This is needed to take the very large voltage from the batteries and make it usable for a raspberry pi. Finding the correct components took much longer for the buck, but since Texas Instruments has sample schematics on most of their datasheets, the schematic was simple to make and test. I'm currently in the process of making and routing the layout.
Once the power board is done, I'm going to move onto the microcontroller board, and get hands-on experience with the electrical systems that can run software, as well as distribute power.
Air Hockey Defense Robot
The Air Hockey Defense Robot was built to sit at one end of an air hockey table and deflect incoming shots. It did this by detecting the puck's initial and final distance from the side of the board as it crossed the midpoint of the table. It measured both the distance and time between the two measurements, which gave it the puck's direction and speed. Then it moved a mallet to intercept it as it passed the robot's side of the table.
I was my team's mechanical lead, so I had to create a system that would move the mallet to the puck's calculated position. This was a significant task, since I was limited to exclusively VEX IQ parts. After several revisions, I ultimately designed a two-axis gantry system, with a belt attached to the mallet in order to move it along the widthwise direction and a linear actuator for the lengthwise direction to strike the puck quickly. The widthwise motor was also geared down at a 9:1 ratio so it would be fast enough to catch the puck, being able to cross the table in a single rotation of the motor.
However, since my wires weren't long enough to cross the entire table, I could only put motors on one side of the table. This made the linear actuator difficult, since it required an equal push from both sides to evenly shoot the puck forward. So, I had to run rotating beams along the full length of the gantry, and recreate the same actuator mechanism on the opposite side. Without this, the mallet would've been angled instead of pushed, and the puck would've been shot back either unpredictably or not at all.
The Air Hockey Defense Robot achieved a 76% deflection rate, despite the very strict material constraints.
Distortion Guitar Pedal
A distortion pedal based on the old Fuzz Face guitar pedal, which uses transistor clipping to produce 'fuzz' in the signal transmitted to the amplifier.
First, I found a schematic for one online and modified it for the components I had available. Then, I calculated the resistances that would be required to complete the circuit and properly bias the transistors for stable clipping. Then I soldered my available resistors in series until they reached the correct calculated resistance I needed to complete the circuit.
Once I had all the correct components, I soldered them together point-to-point, following the schematic. All the components worked properly, except for the LED indicating the pedal was on, which had to be replaced after I calculated the wrong resistance and burnt it out. Afterwards, the finished pedal achieved stable distortion and clipping, without any components overheating.
Side Projects
While mechatronics is my passion and field of interest, I've also had a few woodworking side projects, made in a machine shop or with hand tools.
Ebony Ring
This was made with an ebony ring blank and a ring core. First, I drilled out the right ring size with a drill press. Then I spun the blank on a lathe, removing material until it was the correct shape and thickness. Then I adhered it to the ring core and polished it.
Pens
These were two ballpoint pens made from exotic wood blanks. One was made from pine and agate, and the other was ancient bog oak. The centers of the blanks were drilled out with a drill press, they were spun on a lathe until they were the right shape, and then they were pressed and adhered to the metal mechanics of the pens.
Portable Workbench
Since I'm now living in Waterloo, I needed a workbench that could travel with me, so I could continue working on projects away from home. So, I made this portable workbench out of a 2x12 from home depot. It has two layers glued together, with dog holes and a twin screw vise. I didn't have any power tools when I made this however, so all of it had to be done by hand; the sawing and drilling included.
