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Dual VESC sync problem

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Svenska Svenson
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Dual VESC sync problem

This is a copy from here (With a few amendments):

http://vedder.se/forums/viewtopic.php?f=7&t=873

I don't seem to get much feedback, so trying it here.

 

Hey guys,

I got a setup with 2 VESC driving independent motors but are powered by the same battery. They are on motorholders that are electrically insulated from the truck by design.
Sadly under load the trucks are sliding outwards towards the wheels. To prevent that I made up an aluminum bracket to go in between the motorholders.
Once I connect it the VESCs completely loose it and can't spin the motors anymore.
Has anybody seen that problem before?
Both power on, I can control them individually, can control them with the tool. They do everything they are supposed to do but loose complete track of the rotor position as soon as I try and run both at the same time.
I think the BEMF from one gets transferred to the other? But I have seen that precise setup work before. So not sure what I'm missing here.

Cheers, Svenska

benjamin
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VESC FreeVESC OriginalVESC Platinum
Joined: 2016-12-26 15:20
Posts: 485

can you post a photo or a video? It sounds quite strange.

Svenska Svenson
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Last seen: 3 years 10 months ago
Joined: 2017-10-18 18:22
Posts: 6

Hmmm, how does one post pics here? Doesn't seem to work for me?

Until I figure it out, here the links.

Overview:

https://imgur.com/9CNPvz1

Detail:

https://imgur.com/GYT6dHL

Shorted:

https://imgur.com/KUaaK1t

Hello,

here are a couple pics:

Overview
Here is an overview of the system

Detail
The black insert in the center of the motorholder is plastic. No electrical contact between holder/motor and truck.

Shorted
If I short it like so, both VESC loose any capability to spin the motors.

 

 

 

 

benjamin
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Joined: 2016-12-26 15:20
Posts: 485

It sounds like one of the windings in each motor is shorted to the motor case. Can you measure the resistance between the motor cables and the motor can or holder?

If this is the case the motors are defect or have a design flaw. To deal with that you can take the motors apart and fix the short, or keep them isolated.

Svenska Svenson
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Last seen: 3 years 10 months ago
Joined: 2017-10-18 18:22
Posts: 6

You were right Benjamin. The windings were shorted. Turns out I sucked in some aluminium swarf at one stage. I guess that is what you get for ridding your board around the local hackerspace...

All fixed now. Thank you heaps for your help!

 

-Sven