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High Power Motor Tuning Guide

Hi there,

We have a mitochondrik design in the realm of the Komar ESC. We are having trouble getting a much larger motor to start reliably, and the myxa quickstart guide does not seem to cater to this sort of use case.

The motor is consuming an average of ~1kW of power

I took reference from this topic here, which had a large number of non-documented parameters changed which made a massive difference, to the point the motor will start as smooth as butter, and seems to smoothly operate throughout the throttle range. I am aware of the context of the post and am wondering if there is more guidance on tuning higher power motors, or if there is any obvious post/documentation that I am missing?

Unrelated to this post, the parameter: vsi.tr_rds_on has a minimum value of 0.001Ohm, in our design we have two paralleled up, each with a 0.0017Ohm Rds - which gives an effective Rds on of 0.00085Ohm. Is this an issue if this is simply set as 0.001?

Best Regards,

There are no specific guidelines for tuning larger motors. The instructions are the same for all motors. The larger motors usually have the larger propellers. More torque may be required to spin such a propeller. Therefore, you will need to set higher more m.spup_curr_begn current value.
What kind of issues do you observe? If the motor spinning up well and then stops, it means that there is not enough current to maintain rotation. Set the higher m.min_current value. You can also adjust m.min_eangvel to achieve reliable and smooth switching from the start to the run mode.

The Rds_on value affects the accuracy and quality of control at high motor speeds. Resistance is variable depending on temperature, current and current distribution between transistors. Usually the resistance of parallel transistors is always higher than just Rds_on / 2. So if the power rating is lower than 7-8 kW (Mitochondrik LV is designed for the power rating lower than this value) the effective Rds_on in the model is not lower than 0.001 Ohm. You can set it to this value.

Thanks Dmitry,

Essentially what it looks like is a a quarter of a turn, then a loud “thunk” and the CAN GUI tool reports “HARD STOP” the error reported is:

00000010_01100001 Run 2 Hardware fault Refer to the Hardware fault of the Idle task.

Setting a zero set-point resets the driver and all seems good after that.

What would a sane m.spup_curr_begn, and m.min_current be? I had the former set up at 40A, and the latter at 2A region, but that made no discernible difference. The max current currently set is 60A. When the motor starts up, the current draw is close to 0.5A at idle. The propellers are reasonably big (32") and heavy, but I tried some smaller and lighter propellers (27") and it seemed to have much the same issues.

Reducing m.min_eangvel may have been the key to getting it to start, however any large variation in the low RPM state will still cause the motor to have the behavior as indicated at the start of this post. Manual throttle control (i.e. reasonably slow transitions -> keyboard up + down) can go through the entire throttle range as expected.

Hi Anton,

Please write a message to support@zubax.com? Specify the firmware version on your Mitochondrik. We’ll try to resolve your issue.