Oscillating Motor Speed/Power delivery induced wobbles

[Athrx]

To be clear, i am talking about this:

[itsrow]

Oh I okay I’ll try messing with this then.

[Athrx]

Just set it at 85% on all sides, with the other changes you made before reversed to default and it’s very likely to solve every issue you have, minus a few km off your top speed

[ShutterShock]

Good lord that sounds dangerous… Happy to be using FW 3.62 lmao

[fessyfoo]

@Athrx talking the same thing in the crashes thread:

You got crash videos? We got crash videos

Component tolerances? My trampa vescs read .2~.3v different voltage and cut out at speed at slightly different points. Back starts sliding and i either slow down or fall at top speed. Duty cycle current limit start seems to fix that if set at 85% for me. Lower top speed slightly but i don’t meat crayon with my face at least

and @CiscoV seem to be suggesting the same type of problem in unity setup?

[Athrx]

Caps and bold that current limit start shit for me please. Seems most stop reading right before that and reduce max duty cycle.

[fessyfoo]

If that’s to me. i just pasted a url. I think the original post needs the caps and bold.

[fessyfoo]

So has this issue always been there? or did some particular firmware version introduce the behavior?

[itsrow]

It’s been around since acks 3.103 so I imagine it’s always been a problem just more noticeable since we’re pushing our boards harder than what was possible with reference 4.12s.

[fessyfoo]

So I ran two boards for a while and I geared for torque with top speeds of 28mph - 32mph which I also regularly hit and pegged.

fw 3.65
sensored FOC mode
dual vesc over CAN
PPM control
switching frequency 20kHz
duty cycle current limit start 100%
max duty cycle 95%
Traction Control disabled.
190kv motors
10s battery
16:62 gear ratio
150mm and 145mm wheels.

I never noticed these issues. and I’m wondering what conditions lead to that differentiation. it seems like I should have triggered the issue.

[fessyfoo]

cross linking post seems relevant:

@Venom121212

I’ve been bumping the duty cycle current limit start up from 85% by 1% each ride. 90% has given me no issues and I think I’m going to call it quits there since I have to be going ~45mph to hit that.

Every board is different, I had one that was having weird issues at 90%. Be careful and pad up when changing settings

[fessyfoo]

@NuRxG

As for the the duty cycle cutoff, it is not a bug. It is a setting for which the default value is not the preferred value on a skateboard. But guess what, the default value IS the preferred value on a balancing vehicle, and in many other applications.

[careful not to slide off into the trampa part of that thread]

Should look up when this default value changed (if ever)

I’m still confused why this problem gets associated more with fw5.1 when this thread seems to suggest it’s been around for some time. (all time? )

@NuRxG

@Darkie02

What’s the dangers default?

On previous versions there were power losses near max speed which worked out well as hitting top speed felt smooth, this was fixed and now it performs well till full speed when you get an abrupt power loss, for skaters this can throw people off balance, i think there is also some interplay with 2 motors where it may happen slightly out of sync. Setting the power to taper off as it approaches 95% duty cycle seems to make skateboarders happy.

[fessyfoo]

The “duty cycle current limit start” setting was introduced in fw5.0

vedderb/bldc/blob/80fffde/CHANGELOG#L31

Not sure when the alluded to fixes to max speed performance happened that made that setting necessary.

[kook]

I only jumped back into VESC proper at FW5.01… I got sucked in by the lure of HFI, and I was too stubborn to back out and admit I’d made a grievous error…

but honestly Unity FW 23.46 had a highspeed wobble coefficient that we never figgered out

so there’s that

wher is ackamanic?

[fessyfoo]

@kook

wher is ackamanic?

@itsrow

This happens across all dual motor I have built across Ackmaniacs 3.103, Vedder 3.62/65 and 5.1

[kook]

@fessyfoo

when I was riding ACK FW I was riding slower…

remember the heinous truck walk I had last ride?
tuning traction control (in my mind helped)

[symo]

MountainBiking has taken off over here in my life, but still E boarding every other day on the DIY job.

I have got a problem with the board though - every now and then (when I hit a bump) the drive to the back wheels seems to fluctuate (less power) which is never a good thing.

I was wondering which part of the machine this may be attributed to?

Cheers, Mick

[itsrow]

Could be a loose phase/bad solder joint on the questionable motor / vesc side. Otherwise its going to be hella tricky to track down, what firmware version are you using and which VESC?

[symo]

Yes thankyou, that’s where I’m going to start looking tonight

[itsrow]

Never got to thank you for crosslinking the relevant BEEF, I appreciate it and it didn’t go unnoticed.

@symo ever get your cutouts over bumps figured out?