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First change the `id.id` configuration for each servo using tview. Following the procedure here: github.com/mjbots/moteus/blob/main/docs/reference.md#idid you first change it, then immediately restart tview with the new id in order to issue the `conf write`. Note, this must be done with a CAN-FD interface that is compatible with tview, just like for calibration. Then, in your Arduino script, just assign unique IDs to each of the devices like in the BasicControl example: github.com/mjbots/moteus-arduino/blob/121db53dd9ff38d493652082b6ad0dd8edc963aa/examples/BasicControl/BasicControl.ino#L33

While you could for a low power skateboard, something like a VESC would be a more appropriate option.

All the information that is public is on the product page: mjbots.com/products/mj5208

Nope, I am not selling them. You can get the non off the shelf parts at mjbots.com, including the 12x qdd100 servos needed.

A lot? You can get most of the not off the shelf parts now at mjbots.com

When you command motion or run the GUI? "terrible" audible noise is likely a result of inappropriate PID tuning. devkits should come decently well tuned out of the box. Are you using a devkit or some other motor?

@@awesjosh devkit! maybe 'terrible' is pretty subjective, I ended up recording it ruclips.net/video/HQof8PDN030/видео.html, does this seem normal? maybe a bit hard to tell. Anyhow, I am using the stop function so I can work without being irritated, but I hope I'm not running this thing at too high of voltage and increasing the chances of a problem.

That seems like a normal volume level for the tuning that comes with devkits by default. What voltage are you operating at? There are several knobs you can use to decrease audible noise. 1. lower the `servo.pid_position.kd` gain 2. calibrate with a lower bandwidth 3. set a non-zero `servo.velocity_threshold` While I'm happy to support here, YT comments are relatively high latency. If you would like quicker turn around, hop into the mjbots Discord: discord.gg/W4hUpBb

@@awesjosh ok glad to hear it sounds about right. I haven't touched the default voltage or calibration values. I'm considering this issue closed, thanks for your help!

I largely only work in 6061. There, 0.005" is pretty easy. Tighter is possible, but requires patience and sometimes creativity. I've done plenty of features that are toleranced to 0.001", but you can't do that with every possible feature.

@@awesjosh Awesome, thank you for the reply!

moteus only supports rotating PMSM motors. It supports a wide range of them that have compatible current limits and voltage limits, so there is not a recommended motor list. If you would like some help seeing if something would work, you can email info@mjbots.com, or join the mjbots Discord and ask in the #moteus channel: discord.gg/W4hUpBb

You may be able to use the CAN-FD controller built in to the teensy, but it still requires an external transceiver as the system in the teensy only operates at logic levels. Also, the moteus Arduino library will only work currently with the MCP2517FD and you would have to modify it to work with the teensy's built in controller.

@@awesjosh It was very helpful!! Thank you.

It doesn't work well enough yet for me to have published anything!

The business end of this: mjbots.com/products/moteus-r4-11-developer-kit

One observed failure mode is the CAN PH3 connector having one or more pins not soldered. You could imagine switching to a vertical PH3 connector, however part of the advantage of this specific board is the low profile when assembled.

@@awesjosh good point! that is a failure you hope the fab house would detect for you 😅 but that seems like a other fun project to create a visual inspection with the pi and chatgpt vision API!?!

Yeah, the AOI can only do so much! (And a homebrew one is unlikely to be better than the commercial offering the fab house uses)

I don't have much to offer you on that front. For robotics, I was largely self taught, and just kept grabbing projects that were a little bit harder than what I had done before.

Being self taught, i think you accomplished quite a feat. I'm currently in high school so I'll probably learn via youtube as well.

Thank you.

The sensor in this video is the iC-PZ from IC-Haus. www.ichaus.de/product/ic-pz-series/

Quite a lot! You can build it for a fair amount less now, buying the components from mjbots.com, although it is still not a cheap project.

mjbots.com

info@mjbots.com

@@awesjoshthanks for the response. Let’s discuss on the email thread. Best Shomu

I'm not sure exactly what you are referring to. What current pulse are you trying to measure and why would you be wearing straps to do it?

@@awesjosh I need to measure the current pulse on the oscillocope, what should I do? Can you guide me?

Is this something to do with moteus, or just how to measure current with an oscilloscope generally?

@@awesjosh yesssss. Can you help me?

Unfortunately, I'm not really set up to give that kind of tutorial. If you google for "how to measure current with an oscilloscope", you can find many resources, including this article from tektronix: www.tek.com/en/blog/how-can-an-oscilloscope-measure-current

Are you using an Arduino? If so, just print the current value to the serial console!

Thanks! You called it, it really just does pre-charging and over-current faulting: mjbots.com/products/mjbots-power-dist-r4-5b

@@awesjosh I end up building something like that into almost every board I make, so it makes a lot of sense to have that as a stand-alone unit 🙂 Those who haven't struggled with power management might wonder why they'd need to spend money on a glorified power switch; I think it's up to us who have stubbed our toes to explain why ...

moteus uses a pll filter on the hall effect sensors for commutation purposes, and that is the reported velocity that was used for the outer velocity control loop. The bandwidth of that filter was somewhere between 50-100Hz, so it doesn't do much at low speed with the coarse resolution of the hall encoders.

Thank you! I do similar project and for now use the similar control approach but with some differences ruclips.net/video/LMvEsF9Y2AY/видео.htmlsi=PAa4gED8A2Uu-Ezu In the future I'm going to ustilize mpc for increasing the stability and the robot's speed

Cool! Thanks for sharing! As you can see from my video, you don't need to go to MPC to get significantly improved results. Probably the easiest ways to improve your system would be to see if the structure of your control laws can be improved (or perhaps copy the ones here), and the second would be to ensure your attitude and attitude rate solution are operating well and with a sufficiently high bandwidth. It could also be that your tuning is just sub-optimal. Are you using integrative terms anywhere (you probably shouldn't)?

Thank you for recommendations! Yes, I use integrative terms both in attitude loop and in velocity control loop. I have some suspicious about imu. It outputs data only with 100hz. Probably if I replace IMU to better one, the whole system will be more stable.

I'm not sure an integrative term for attitude is useful, certainly this robot does not use one. A feedforward term is probably a lot more valuable there if a plain PD is insufficient. While a 100Hz IMU update rate is borderline feasible, there are lots of things that could potentially make it problematic. That could be if you are just using pitch and not pitch rate, or if the IMU has a software configured low-pass filter, or if it is poorly mounted, or a host of other things. This robot uses a 400Hz update IMU for instance with a 200Hz onboard filter, uses the pitch rate in addition to the pitch, and is known to work well at up to that rate.

Thanks!

Unfortunately no, it can't be used with a raspberry pi 5. It only works with a pi3 or pi4.

Opps checked the manual and it clearly states it isn't.

I'm working to keep them coming!

Nice to hear from you Karl! This was one of those projects where making the video and explaining it was 4x the work of actually building the thing, so it is great to see it appreciated!

Faults are cleared by sending a stop command, in tview that would be: d stop Power cycling will also work, but with the devkit you will need to remove power from the PSU for some time before it discharges completely. Also, don't hesitate to join and ask questions in the mjbots Discord, it is a lot easier to get support there than in youtube comments! discord.gg/W4hUpBb

Sadly no. You can get cheap options with more capabilities from Unitree now for instance.

Thanks! Not much other info or video yet, but @mjbotsrs on x/twitter does have a video with a few new cuts. The control is just an inner pitch PID loop using the pi3hat ARS, and then an outer PID loop that controls velocity through selecting pitch.

Thank you!

Yeah, standard ethernet connectors are very large for many of the applications moteus is used in, besides that since the micro mjbots has standardized on doesn't have an ethernet controller it would require either an external controller or a switch to a different micro. ethersweep is looking cool, keep up the good work! If you ever need performance beyond what steppers can provide, moteus is there for you!

The smallest driver mjbots offers currently is this moteus-c1, which is 38mm x 38mm.

C++, although it would likely be just as possible with python.

@@awesjosh Will wait the code for building

Heh, I guess that will severely limit your choices!

@@awesjosh Absolutely. We are memory safety first. Security is our highest priority. We just ended up designing our own Rust based ESC!

Yep, it is the way of things! In any event, bindings are not really a big effort and I would expect writing the rust code to generate and parse frames for the things you are using would not be a significant fraction of your integration effort.

Yep, you can.