The moteus line of brushless motor controllers currently require a CAN-FD host to send commands in order to actually execute a motion profile. moteus has long provided a python library that can be used on desktop operating systems to send commands and parse responses, and recently added a C++ one as well. Next up, and described in this post, is a library for Arduino which provides the ability to command and monitor brushless motors using moteus motor controllers.

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.

On the mjbots discord, people are often looking for the cheapest possible way to command and monitor a moteus controller. One possible solution that comes up over and over again is the CANBed-FD board, as sold by Seeed Studio (and others). I decided to get one of these in house to see if I could make it work:

The first thing I figured out was that the DB-9 connector used a non-standard pinout for CAN_L and CAN_H. I just switched to the terminal block connections instead of the DB-9 to get around that. For the software, I decided to use the acan2517FD Arduino library, as it was quite a bit more robust and featureful than the one provided by Longan Labs.