Home on Robot Daycare

Until Google axe-murdered it recently, I used Google Play Music to store my music collection and stream it to my various devices.

 I did another batch of Furuta pendulums and took a timelapse of the assembly: These were done in a bit of a hurry, and nothing was changed from last time.

This was inevitable, but the pandemic has accelerated my home-shop setup.

I put together a mostly-3D-printed prototype of the variable-pitch screw idea.

I just noticed that as of this month, I've had build-its.blogspot.com for 10 years.

An idea I've had in the back of my head for a while now is using varying transmission ratios to transfer kinetic energy between bodies.

A month or two back I tried out anodizing a titanium bicycle fork.

I've been working on a large robot-size motor drive, with a design target of 75V, >70A (peak phase) continuous with heatsinking, and >150A peak.

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

Back during my second year of undergrad I started scheming about building legged robots out of cheap hobby brushless motors.

I built a pair of planar magnetic headphones - basically just because I though the operating principle was interesting.

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, volta…

In December 2015 (4 whole years ago!)

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

I built 6 furuta pendulums for a university controls class: Since the original furuta pendulum was all built out of scrap I had lying around, I had to redesign pretty much everything from scratch.

Here's a photo-dump of some pictures from assembling the herd of Mini Cheetahs. 150 Stators: 150 Front actuator housings with output bearing installed: 50 upper legs.

The last few months have been very busy.

I just finished building a bunch of Mini Cheetahs which the lab  is loaning out to other research groups.

I was just at ICRA 2019 with the robot, to present a paper and demo the robot: Not my picture.

Now that this is officially out I can finally put up something about what I've been doing for the past 2 years.

A long overdue progress update on the big dyno.

Over a year later, I've finally finished up the planar magnetic headphones.

A company called Core makes some unusual electric lawn tools based on axial flux PCB motors.

I was playing with my thermal test motor, and noticed that at high speeds, some pretty significant harmonics showed up in the phase currents.

I made a cover for the small motor controller, which serves as both a top-side heatsink for the MOSFETS and gate driver, and (more importantly) as a clamping mechanism to keep the PCB flat and evenly pressed against the heatspreader beneath it.

With the various layout errors on the last set of boards fixed, the controller seems to work as expected, so I've been doing some thermal testing.

Remember how I said I was going to re-do the integrated motor controller using the new TI DRV8323 chip?

Bayley and I have been thinking about building a bigger motor dyno for a while now, based off the same power system as the Big Kart.

A collaboration with Jared.

A while ago I added the hall effect encoder IC I've been using directly to the motor controller PCB.

In an out-of-character move for me, this post has no actual hardware in it.

To better characterize the big kart motor, I threw together a stall torque test stand.

Brief Introduction: Go read Bayley's introduction.

I did some data-gathering for Dane on a generic looking 48V 1800W brushless electric scooter motor widely available on ebay and aliexpress, paired with a 1500W E-bike controller.

I finished putting together a housing for a single driver.

Now that I have a good process for collecting data on the motor dynamometer, and the appropriate scripts for quickly processing the data, I put up a page dedicated to motor dyno data.

A brief break from 3-phase electric motors, for a different kind of electromagnetic actuator.

In the near future I'll need to make a bunch of things with tight-tolerance 22 mm bores, so instead of buying a 22 mm reamer, or just boring the holes like a normal person, I tried out re-grinding a 7/8" reamer (22.225 mm) reamer down to 20 mm by setting…

Here's round 3 of wrapping up draft blog posts I've been sitting on for a while.

I've mostly finished the toolpost spindle.

I finished up the code for automatically generating and post-processing efficiency maps on the motor dyno.

** 12/5/2017 Update ** A number of people noticed that this post disappeared for a while.

I finally got around to writing a position sensor auto-calibration procedure, for measuring the orientation of the position sensor relative to the stator.

I've been thinking for a while it would be nice to have live tooling for the MITERSlathe, for things like grinding and indexed drilling parts like hubs.

Bayley has a pretty cool Sinar view camera.

A quick build which is incredibly useful.

Here's the Talk-To-Everything Board.

It snowed rather a lot last Saturday, so I was finally motivated to get the snow bike up and running again.

While waiting for boards and parts for the motor dyno to show up, I got distracted by doing some motor modeling and simulation.

A few minor differences on this revision: Switched to lower-ESR through-hole electrolytic capacitors, from surface mount ones Added a MCP 2562 CAN transceiver, to make it more straightforward to build robots with lots of motors on them.