• Testing torque

    Josh Pieper3 days ago 0 comments

    I wanted to measure the realized torque from the qdd100 servos, so built up a simple fixture that let me attach a 1m long pole:

    I used that to push down on a digital scale and figure out the actual torque mapping.   The plot of phase current vs torque looks like:

    I've got some more learning to do to fully understand why the torque constant is lower than I expected, why it drops off as much as it does at higher currents, and why I have the variability I have between devices.

    Here's a video showing the testing:

  • And it walks!

    Josh Pieper03/20/2020 at 13:25 0 comments

    I ported my simple walking gait into the full rate 3D force controlled framework and ran it on the quad A1.  That alone made the walking work much better than before.

    Also, I have a limited number of the qdd100 servos available for beta testing: https://shop.mjbots.com/product/qdd100-beta-developer-kit/

  • It moves!

    Josh Pieper03/18/2020 at 12:38 0 comments

  • Introducing the mjbots quad A1

    Josh Pieper03/16/2020 at 11:02 0 comments

    Here's a quick video showing rebuilding the legs on the mjbots quad A1.  Everything is upgraded from the A0, including 12 qdd100 servos, a new body, new legs, and a new power distribution board, and a new raspberry pi daughterboard.

    and a pic of the final result:

  • mjbots quad A1 - teaser!

    Josh Pieper03/05/2020 at 16:38 0 comments

    Just a quick video teaser:

  • Pre-production mk2 servos

    Josh Pieper02/26/2020 at 12:42 0 comments

    I've got a lot of parts in house now, and have built up a fraction of my pre-production mk2 servos!  So far all good!  Here's some pictures of the parts and build:

    Planet Outputs
    Planet Inputs
    Bearings installed
    Front housings with internal gear and planet output
    Rotors with sun gear and bearings
    Brushed back covers
    Finish test of outer housing
    Stators installed
    Planet input assemblies
    Planet inputs installed
    Back covers installed
    Controllers soldered
    All buttoned up!

  • moteus r4 controller devkit coming soon

    Josh Pieper01/15/2020 at 11:47 0 comments

    Update: All the beta slots are full, thanks for your interest!

    The r4.x series of the moteus controller is coming along nicely.  I now have enough boards in house to build a quadruped and am making some development kits for others to experiment with.

    That's a prototype of the development kit, which also comes with a power supply and all the cables and adapters you need.

    There's a whole bunch of controllers!

    And a quick video showing it spinning on the devkit stand.

    If you're interested in purchasing a devkit later this month for $199, you can fill out this google form to get a spot in the beta program: https://forms.gle/aevTe66QnPjB8NPC7

  • moteus controller r4.x

    Josh Pieper12/20/2019 at 14:20 1 comment

    I'm making progress bringing up the "production" version of the moteus controller, the r4.x series.  This version is designed to be produced in medium volumes, and also resolves some of the annoyances I had in the r3.x series.  Features:

    • 3 phase brushless FOC based control
    • Input: 12-34V
    • Connectors: Daisy chainable power (XT30) and data (JST PH3)
    • Communication: Up to 8Mbps FD-CAN
    • Output: With proper heatsinking, 30A continuous phase current, 100A peak
    • Form factor: 45x54mm w/ M2.5 mounting pattern
    • Mass: 14.5g
    • Integrated AS5047 magnetic encoder

    So far things are looking good.  I ran some endurance testing using a juggling ball as a test mass and a prototype mk2 moteus servo.

  • Pronking!

    Josh Pieper11/07/2019 at 11:38 0 comments

    Another short video update:

  • Belly Flop!

    Josh Pieper11/01/2019 at 10:32 1 comment

    Another mini-video update: