The Mini Cheetah Robot

Back during my second year of undergrad I started scheming about building legged robots out of cheap hobby brushless motors.  Two years later as a senior, I finally made a first-pass at building some of the hardware - motor controllers, gearboxes, and a two-degree of freedom leg.  Things look promising, so I stayed at MIT to do a masters in Sangbae's lab continuing the project.  The Mini Cheetah robot is the result of that work:

Photo: Bryce Vickmark

First quadruped robot to do a backflip!

The first version of the robot was put together in March 2018.  I spent the summer after finishing my Masters helping get the robot fully up and running (literally).  When we saw how well everything worked, we decided to build a handful more of the robots, both for our lab and to loan out to other research groups to experiment on.  I spent about a year doing some design revisions and building 10 more of the robots.

The robot is probably best documented in my masters thesis, but there are also several blog-posts as well.

Here are several papers (in no particular order) published about the robot or  using it.  I'll keep updating this list as I hear about more publications using the robot

• Mini cheetah: A platform for pushing the limits of dynamic quadruped control
• Benjamin Katz, Jared Di Carlo, Sangbae Kim
• Highly Dynamic Quadruped Locomotion via Whole-Body Impulse Control and Model Predictive Control
• Donghyun Kim, Jared Di Carlo, Benjamin Katz, Gerardo Bledt, Sangbae Kim
• Vision aided dynamic exploration of unstructured terrain with a small-scale quadruped robot
• D Kim, D Carballo, J Di Carlo, B Katz, G Bledt, B Lim, S Kim
• Hybrid Systems Differential Dynamic Programming for Whole-Body Motion Planning of Legged Robots
• He Li, Patrick M. Wensing
• Model Hierarchy Predictive Control of Robotic Systems
• He Li, Robert J. Frei, Patrick M. Wensing
• Regularized predictive control framework for robust dynamic legged locomotion
• Bledt, Gerardo.
• Extracting Legged Locomotion Heuristics with Regularized Predictive Control
• Gerardo Bledt; Sangbae Kim
• Variational-Based Optimal Control of Underactuated Balancing for Dynamic Quadrupeds
• M Chignoli, PM Wensing 
•  Robust Autonomous Navigation of a Small-Scale Quadruped Robot in Real-World Environments. 
• Dudzik, Thomas & Chignoli, Matthew & Bledt, Gerardo & Lim, Bryan & Miller, Adam & Kim, Donghyun & Kim, Sangbae. 
• Concurrent Training of a Control Policy and a State Estimator for Dynamic and Robust Legged Locomotion
• Gwanghyeon Ji, Juhyeok Mun, Hyeongjun Kim, Jemin Hwangbo
• Learning to Jump from Pixels
• Gabriel B. Margolis, Tao Chen, Kartik Paigwar, Xiang Fu, Donghyun Kim, Sangbae Kim, Pulkit Agrawa
• Agile Locomotion via Model-free Learning
• Gabriel Margolis*, Ge Yang*, Kartik Paigwar, Tao Chen, Pulkit Agrawal

The Rubik's Contraption

Jared Di Carlo and I built a machine that can solve a Rubik's cube really fast, and it became kind of internet-famous:

See my hardware and low-level control build-log here

and Jared's software blog here

Planar Magnetic Headphones

I built a pair of planar magnetic headphones - basically just because I though the operating principle was interesting.  After several catastrophically bad-sounding attempts, I eventually built a version that sounded decent and looks pretty good:



The drivers are meticulously hand-etched from the thinnest flex-pcb material I could find.  The driver membrane is sandwiched between an arrangement of magnets embedded in the aluminum grill that makes up most of the structure of the headphones.

See the build-log here for details

Furuta Pendulums

In the summer of 2016 I built a desktop furuta pendulum out of random parts I had lying around:

Recently, I redesigned it to not be built out of scraps, sent out for all the machined parts, and assembled a handful more:

See the build logs here

Motor Dynamometer

In 2016 I built an electric motor dynamometer - a device for characterizing the performance of electric motors and motor controllers



The dynamometer is controlled by a Python and QT-based interface which provides manual control of the torque, speed, voltage, and current, simulates loads, or runs through sequences of test points.
The dyno lets me characterize electric motors to generate useful data like efficiency maps:



See the build log here:

Machined Electric Travel Ukulele

In December 2015 (4 whole years ago!)  I machined an electric ukulele out of some aluminum, stainless steel, and brass.  The whole thing was built over the course of less than a week, with no computer aided design save for the fret-board.

It's a headless design with the tuners built into the body.  Under the carbon fiber cover at the center is a home-made low profile pickup.  The body was hand-shaped using a combination of a bandsaw, manual milling machine, and hand-filing.

See here for the build-log

Benchtop Lathe

After stumbling upon the bed, carriage, and tailstock from a Taig lathe, I rebuilt the lathe, making all the parts I didn't have already.  This includes new cross slide and compound slide, a new headstock and spindle with integrated taper for ER32 collets, and brushless spindle motor with a DC custom power supply.

Here's the build log (and many more pictures), which will be occasionally updated as I add features like auto feed and chucks.