For those who have been annoyed by the misplaced I2C connector on the r4.3 moteus model, I’ve finally updated the 2D and 3D mechanical drawings for the moteus controller in github:
https://github.com/mjbots/moteus/tree/main/hw/controller/r4.5
And in the same vein, we received a great user contribution from Rüdiger Koch-Kukies in the form of a solid model of the mj5208 motor!
Sometimes you find bugs, and sometimes the bugs find you! While getting ready to release some updated qdd100 beta servos, I was investigating speed control in the moteus firmware and discovered an unwelcome surprise!
To improve dynamic response under high accelerations, moteus uses a voltage feedforward term as part of its control loop. When trying to command a specific current, it normally applies a PI controller to determine the resulting D and Q phase voltages to apply. The feedforward component of this looks at the phase resistance and the current rotor velocity, and determines a zeroth order estimate of what voltage would be required to achieve that current under a no-load condition, only using the PI controller to determine the difference.
While testing some variants and new versions of the power_dist board, I wanted to be able to simulate the types of loads that it experiences with a fully loaded robot. Some things are easy, like this capacitor attached to an XT30 connector:
I also have giant power resistors in a similar form factor:
However, a dumb load resistor isn’t a particularly representative load. Most likely, the loads that a power_dist will drive are active loads with switching regulators. When the output voltage is lower, the current will be correspondingly higher. That is especially important when validating pre-charge behavior, because it means that the current is much higher during the initial pre-charge window than it would be for a pure resistive load.
I’ve been using a relatively inexpensive microscope for SMD soldering work for some time, connected via HDMI to a 24" monitor.
For the price, I’m definitely happy with it, but as I’ve been doing more soldering work, I’ve become less happy with the mounting stand. The arm it mounts to often does not reach far enough to get the optics over the part of the board in question, or the base is too tall or wide to fit under it. If you want to examine something from the side, you have to tip the entire base over. I have resorted to spinning the microscope around and counterbalancing the base with a large weight, which works for some definition of “works” but only improves the reach by a little bit.
With new python based moteus tview and moteus_tool available, and the new mj5208 motor being included in all the moteus devkits, I figured it was time to update the moteus getting started video. Here it is!
