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Junior Mechatronics Engineer at OffWorld, Inc.

I was originally set to graduate Caltech in June 2021, but as the summer of 2020 continued with no end in sight to the pandemic, I decided to take a year off from school and find an internship rather than do senior year online. For me, this turned out to be a great choice: I had an amazing experience working at OffWorld, a space robotics startup in Pasadena, and am now able to finish my coursework in person. I mostly worked in-person, safely masked, except when when COVID cases got really bad after Thanksgiving 2020 and we went as remote until things settled down. 

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My first internship at Auris was a great experience at a medium-sized company; at OffWorld, I got to experience life at a rapidly-growing startup. On the Mechatronics team I worked closely with the other engineers on simulation, design, fab and assembly, testing, and documentation. I developed great relationships with the team and owned many of my own projects, as well as helping review others' work. I loved the company culture - friendly, supportive, smart, and dedicated - and would very likely have returned if I weren't so set on getting out of Los Angeles post-graduation.

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Here are some of my projects that I can share:

Terramechanics Simulations in MATLAB

When driving over terrain with loose rubble, what mobility system is best? What if you have to a steep slope to navigate? What if you periodically have to stop and exert forces on your surroundings without slipping?

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I led a project to simulate the effectiveness of various configurations of tank tracks and wheels on sloped zero-cohesion terrain. This involved researching academic papers on terramechanics to find and in some cases derive the necessary equations for simulations. I then wrote MATLAB scripts to produce insightful plots comparing different robot designs and inform the company's decisions.

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Key references were:

  1. T. Guo. “Power Consumption Models for Tracked and Wheeled Small Unmanned Ground Vehicles on Deformable Terrains.” Dissertation. University of Michigan. 2016

  2. G. Ishigami, A. Miwa, K. Nagatani, and K. Yoshida. “Terramechanics-based analysis on slope traversibility for a planetary exploration rover.” Article. January 2006.

  3. M. Islam, A. Siddika, B. Hossain, A. Rahman, and A. Asad. “Effect of Particle Size on the Shear Strength Behaviour of Sands.” Australian Geomechanics, Vol 46, No. 3. September 2011.

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Four questions to answer: can an uphill-facing robot (1) gain enough traction to drive forward up a slope, and (2) enough traction to avoid slipping down the slope? Can a sideways-facing robot (3) gain enough traction to drive forward at a constant elevation, and (4) enough traction to avoid slipping sideways down the slope?

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This figure illustrates the key variables in calculations. Key constants included numerous terrain parameters, and robot design measurements. Ultimately, my results suggested that tracks outperformed wheels while driving in the given conditions. While static, wheels outperformed tracks - which makes intuitive sense: the wheels sunk further into the ground, inhibiting slippage.

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OffWorld Gym Robot Upgrade

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OffWorld Gym is a project to test algorithms on a real mini robot. Because the robot drives around in an environment of "little" rocks that were relatively large compared to its wheels, the bot was frequently high-centering.

 

I was tasked with designing and fabricating an easy-to-switch-in modification to the robot that would improve its ground clearance. I settled on increasing the wheel size as a relatively simple fix, which required the following adjustments:

  • Ordering motors with a higher gear ratio to offset the torque requirements of a larger wheel diameter

  • Designing a lower chassis that would attach to the current robot body to accommodate the larger wheels, as the current motor placement would cause front and back wheels to touch. This was designed as bent sheet metal, and fabricated by a local machine shop.

  • CAD-ing and 3D printing glue-in plastic inserts to the tires to eliminate gaps where small rocks could be wedged

  • Changing the dimensions of anti-tip wings mounted on front an back of the bot to prevent it from toppling

Maintenance Manual and Power Apps

Documentation and procedures! These are critical to running smoothly and staying organized, and I worked a lot on both writing documentation and designing tools to manage it.

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Maintenance Manual

I helped write the maintenance manual detailing the assembly and functionality of one of OffWorld's main robots. This involved:

  • Creating exploded views in SolidWorks, labeling parts, and writing detailed assembly instructions

  • Performing key maintenance tasks on the robot and photographing each step, then annotating these photographs and writing clear maintenance instructions

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Power Apps

Our team in Pasadena was coordinating with another team thousands of miles away to test our robot in the field. This required the teams writing up many procedures, organizing them, and recording when those procedures were performed. Using Microsoft Power Apps, I designed an application to retrieve the procedures the team had written in SharePoint Excel documents and automatically format each one into a step-by-step procedure. The test team could then use the app to run through procedure checklists and submit records of those checklists into a database.

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Designing this application in Power Apps was an insightful experience in the complexities of data management, user experience, and frequently changing procedures as the company learned more about our robot and best operational practices. It was also a lesson in the benefits and limits of so-called "low-code" tools like Microsoft Power Apps: while features of the app were very easy to make thanks to Microsoft's interfaces, others became frustratingly convoluted. 

Additional Contributions

OffWorld's Fabrication Capabilities​

  • Managing and repairing OffWorld's FDM printers:

    • Repairing snapped belts

    • Unclogging and replacing faulty nozzles

    • Scheduling print jobs to optimize printer time usage

  • Helping clean, repaint, and restore a Bridgeport mill​

  • Starting to learn to weld! Did not get very far (certainly not far enough I would say I know how), but it was a great experience and awesome to have a team member so excited to teach people

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Design Brainstorms

  • Participating in the brainstorming and preliminary design process for new OffWorld robot species

  • Creating diagrams to illustrate concepts for new mechanisms​

  • Understanding and recording design requirements

  • Writing SWOT (strengths, weaknesses, opportunities, and threats) analyses for design decisions

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Other

  • Proofreading electrical schematics by cross-referencing with other documentation

  • Assisting with assembly and quality control of M12 connectors

  • Helping design a camera case to withstand IP requirements

  • Researching resources to transition the team into usage of a proper PLM/PDM system

  • Packing assemblies and spare parts for shipments to teams across the world

  • And more!

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