The moteus controller, communicates exclusively over CAN-FD for command, telemetry, and diagnostics. It will accept either standard or extended frames, and until now, the ID format in terms of bits looked like the following:

33333222222221111111100000000
43210765432107654321076543210
XXXXXXXXXXXXXQSSSSSSSDDDDDDDD

Where:

• X: Don’t care
• Q: 1 for query, 0 for no query
• S: source ID
• D: destination ID

If the lower 8 bits matched the configured ID, all the X bits would be completely ignored and moteus would accept the CAN message as if it were destined for itself. This may not be super desirable, as it consumes nearly all of the available CAN-FD addressing space.

I and the quad A1 had a great time at the FAB16 festival in Somerville this past weekend. The robot got to do a lot of running around, it and I got to meet a lot of new people, and two bands showed up!

Here’s a video of the quad A1 and Spot hanging out trying tricks:

And here’s another one of a “dance off” (kinda) with the School of Honk band. Note that although both robots collapsed at the end of this video, the quad A1 got back up and kept dancing. (Spot wasn’t broken, they just didn’t want to right it when close-ish to people). Thanks to Kathleen and Josh from BD for inviting me into their area and for being such good sports!

The title says it all! Check out the quad A1 and friends there!

Check out the quad A1 and all the mjbots products at the FAB16 festival in Somerville, MA this Saturday August 14th from 10am to 4pm (with a rain date on Sunday).

I’m going to try something new for this effort, and instead of making a bunch of blog posts culminating in a video, I’m going to make a bunch of intermediate progress videos. They may, but may not, culminate in an overview blog post. Here’s the first!

The qdd100 servo uses a planetary geartrain as the transmission reducer. This consists of an outer ring gear, an inner sun gear connected to the rotor as the input, and 3 planets connected to the output. The tolerances of these gears directly impacts the performance of the servo, namely the backlash and noise.

To date, I’ve been hand-binning these and testing each servo for noise at the end of production. To make that process a bit more deterministic, and with less fallout, I’ve built up a series of manual and semi-automated gear metrology fixtures to measure various properties of the gears.

I’ve been doing some machining on the Pocket NC lately to prototype some “design for manfacturing” improvements. Some time ago Q at Pocket NC posted that early versions of the v2-50 had a spindle power limit that they later decided wasn’t necessary. My v2-50 was pre-ordered at the launch, so had said limit. There was a procedure for removing it in later versions, which just required removing a single SMT resistor.

For most of mjbots’ existence, all of our products were labeled with a dependable, if lackluster, Brother P-Touch label maker. In line with other packaging improvements, I recently upgraded that labeling setup to bigger, higher resolution, and full color!

This is using an Epson TM-C3500, which I had expected to operate directly from my Linux based test fixtures. However, upon receiving it, discovered that alas only Windows drivers were available. Thankfully, it wasn’t too bad to print from python in a simple way as long as you manually select the media type from the Windows dialogs. Thus I made up a simple Flask app to receive label images over HTTP and print them. That runs on a Windows computer, and the test fixture applications just POST their label images to it.

The pi3hat, among other things has 5 CAN-FD ports. You can use them to drive a lot of moteus servos, but they are perfectly fine CAN-FD ports generally. The C++ library has always been able to send and receive arbitrary frames (and recently at arbitrary bitrates), but the python interface was lacking, only exposing a portion of this functionality.

As of version 0.3.11, the python library (pip3 install moteus-pi3hat) now exposes everything you need to be able to send and receive arbitrary CAN frames from any of the ports, as well as configure all the timing options for waiting for responses from slave devices.

This is somewhat belated, but only recently have I actually gotten them all set up in the desired configuration. Welcome to the newest members of the mjbots factory line, another 2 Prusa MK3Ss! That makes 4 total, now all neatly lined up in a row:

The first two have had a greater than 60% duty cycle over the 3 years I’ve had them, and situations kept coming up where I was blocked on 3d printer bandwidth. For now at least that need is sated.