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Oscillation and cut out problem with Gotway MSuper V3, ACM, maybe Monster shipped from May 2017 onwards

271 posts in this topic

12 hours ago, esaj said:

It's clear that at least one (I think those were low-side on Rehab's board) mosfet on the two phases has been destroyed, can't see if the parallel ones are fried too. There must have a been a lot of heat to burn a hole in the casing, might even be a shoot through? I'd expect that if the mosfet "just" overheats and turns the junctions inside the mosfet into jello, it would just die somewhere around 125-150C junction temperature or whatever, which likely wouldn't be enough to melt the plastic around it, so there'd be no outside signs. Those look more like they exploded, so a very high current spike would seem more likely, but of course I can't say for sure. The large caps in the mainboard can give a very high current spike for a brief moment, depending on capacitor make and model, the internal ESR can be as low as <10 milliohms, if you'd short those at 84V over fully open mosfets with a few milliohms of Rds(on), the momentary spike could easily be several kiloamperes (1000's of amperes), probably the fets would die before they can fully turn on?

 

Sorry, I'm not sure what you're asking here? Maybe turn off auto-correct? ;)

lol. Funny auto. 

I was asking. I believe to do sensorless commutation (no hall sensors) the circuit board has to have some electronic circuit added to trigger at the zero-crossing on the floating phase. is there another way to sense without sensor? Lol. That last sentence just read weird!

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Posted (edited)

2 hours ago, Carlos E Rodriguez said:

lol. Funny auto. 

I was asking. I believe to do sensorless commutation (no hall sensors) the circuit board has to have some electronic circuit added to trigger at the zero-crossing on the floating phase. is there another way to sense without sensor? Lol. That last sentence just read weird!

There are, the current sensors. In FOC, actually at most times, ALL the phases are powered (well,  connected) at varying duty cycles. There's probably a brief period where one of the phases is not connected either on the high or low-side (0% duty cycle). Inspect this animation, the smaller arrows are the duty cycles of different phases over one "electrical revolution", ie. when the poles of all phases are passing the magnets for a one full commutation cycle, and when a phase is passing through the "zero" it switches from high to low-side (or vice versa), at that point a phase is probably floating for a brief bit:

vecmovieslow.gif

I can't claim to fully understand FOC yet, for example I'm not sure how the estimation of the position & speed is done for sensorless algorithm. The best I can describe my understanding of it so far is that the duty cycles are used to "mimic" the sinusoidal (the motors are apparently PMSMs, Permanent Magnet Synchronous Motors, and not BLDCs, so the back-EMF is not trapezoidal like in the BLDC commutation) waveform, except it's phase-shifted (the duty cycles move "ahead" of the actual rotation). There are only two current sensors, because the sum of the phase-currents equals zero, so the last phase current can be calculated from the two other phases, and there are a couple of matrix transformations done to get the values... But you should probably look up some application notes and articles if you're interested in the subject, they explain it much better than I ever could, plus I would probably just make mistakes trying to explain it (or might even have understood some things totally wrong).

 

Edited by esaj
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Strangely hypnotic, the resultant stays the same and the other three rise and fall.:mellow:

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1 hour ago, esaj said:

 

vecmovieslow.gif

This kept me wondering for a while, why it looked so strangely familiar. Then I found out:

Never mind the apparently erratic back and forth movements. When you observe the vertical carriages, their hight is a direct mechanical representation of the currents driving our motors, isn't it?

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Posted (edited)

12 minutes ago, Tilmann said:

Never mind the apparently erratic back and forth movements. When you observe the vertical carriages, their hight is a direct mechanical representation of the currents driving our motors, isn't it?

Yeah, that seems like a good analogy. :) 

 

Edited by esaj
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15 hours ago, dalewalker said:

It was sent before the serious injurys happened but it was the same problem and that was there fix.

He was one of the 1st few that experienced the problem and I got straight onto it because im a good dealer :-p

Its possible all they did was sent another board thinking "hope this one works ok" because before the many and some serious accidents they didnt take it as serious. There was a few around that time and it was a couple weeks before the bad accidents so those bad accidents probably could have been avoided if it was taken seriously 

yeah. Its a good thing we spread the word. now that everyone knows, its not as easy to ignore it :)

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On 6/13/2017 at 10:57 PM, meepmeepmayer said:

Has anybody of the affected riders had a look at their motor cables?

Usually I'd think this is a very far fetched theory, but with @Hunka Hunka Burning Love's psychic abilities maybe this is it.

I will be doing that tomorrow on 2 wheels

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You have two affected wheels? Poor guy:cry2:

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Posted (edited)

:o Oh man, are you okay?  Good thing you were wearing safety gear.   That was painful even to watch!  Sounds like a bad connection somewhere that breaks contact intermittantly with vibration or maybe control board fault with a bad gyro sensor?  Have you opened up the wheel yet?  Please post photos up if you do.

Edited by Hunka Hunka Burning Love
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6 hours ago, WaveCut said:

Multiple wobble cutouts on new Msuper v3s+ (7 occasions, 4 on video). Wheel gets wobble after some obstacle and cuts off.

 

Wow. I would not ride that wheel at all. Seems like a faulty connection somewhere. Glad you didn't get hurt.

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6 hours ago, WaveCut said:

Multiple wobble cutouts on new Msuper v3s+ (7 occasions, 4 on video). Wheel gets wobble after some obstacle and cuts off.

 

First off, I hope you are OK.  Seems like you are padded up well, but I hope you have held off on any more riding of that wheel...I'm pretty sure after the 3rd or 4th one I would have said, "enough is enough"!  I am praying that my new ACM does not have this type of issue...I just don't think that my body can take too many of these cutouts :blink:...

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6 hours ago, WaveCut said:

Multiple wobble cutouts on new Msuper v3s+ (7 occasions, 4 on video). Wheel gets wobble after some obstacle and cuts off.

 

This definitly is the "new Firmware feature" Gotway implemented on their Batch from 1.May to 15. May.....

Acts exactly like all other "Faceplanters" described it....wheel got over a hubble, small obstacle, or bump and  then started oscillating, wheeling like wild and then cut out....

 

Thank God, These wheels have been ---Quote of Linnea- "mainly shipped to China Mainland, where nobody reported Problems" and to some Little resellers, but These did not receive their wheels yet.

 

Tsss....seams like a real lot of those "new Firmware boards" made their way in the wild, where more and more People Report of this issue.....

Sorry, if this sounds a bit sarcastic, but comeone: Doing such a Firmware tweak-saying nothing?, and while testing nobody drives over a bump??? Was there even a testing done?

And when i hear/read that the reason for the Firmware "worsening" was meant for "high-speed related" cases...i am just near to vomiting, Sorry!

 

 

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Posted (edited)

Seems almost like a numerical error - due to bumps the balance algorithm (or something else?) starts oscillating and being amplified (till it's too much) instead of being dampened (into a stable state).

Edited by meepmeepmayer
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31 minutes ago, KingSong69 said:

This definitly is the "new Firmware feature" Gotway implemented on their Batch from 1.May to 15. May.....

Acts exactly like all other "Faceplanters" described it....wheel got over a hubble, small obstacle, or bump and  then started oscillating, wheeling like wild and then cut out....

 

Thank God, These wheels have been ---Quote of Linnea- "mainly shipped to China Mainland, where nobody reported Problems" and to some Little resellers, but These did not receive their wheels yet.

 

Tsss....seams like a real lot of those "new Firmware boards" made their way in the wild, where more and more People Report of this issue.....

Sorry, if this sounds a bit sarcastic, but comeone: Doing such a Firmware tweak-saying nothing?, and while testing nobody drives over a bump??? Was there even a testing done?

And when i hear/read that the reason for the Firmware "worsening" was meant for "high-speed related" cases...i am just near to vomiting, Sorry!

 

 

I agree so much. If the Gotway software people are as concerned about quality as their packaging engineers I would be very frightful to hear that they've tweaked the firmware. I would think once they have their magic sauce (the firmware) working that's the last thing I'd be changing. But I don't work at Gotway.

That whole description that they gave about what they were trying to do doesn't pass the smell test with me.

This episode reaffirms my belief in buying wheels from a well known dealer instead of trying to save some money by buying direct from China.

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Just now, meepmeepmayer said:

Seems almost like a numerical error - due to bumps the balance algorithm (or something else?) starts oscillating and being amplified (till it's too much) instead of bein dampened (into a stable state).

It sounds to me still the PID controller routine and the values of the P and D used.. 

As the bump in the road gives a short increase in the output, then due to the shooting forward the bodyposition slightly changes and breaks again.. I think D should dampen this out.. So my guess would be a bit lower P value and a touch of D...

 

 

 

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So has the source of the issue revealed yet?  Has anyone have actual information on what is broken?

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17 hours ago, Marty Backe said:

Glad you didn't get hurt.

23 hours ago, Hunka Hunka Burning Love said:

:o Oh man, are you okay?

17 hours ago, Maximus said:

First off, I hope you are OK.

That's not my wheel, but person is OK, littlle scratches only. Hes wearing an fullface helmet and elbow/knees protection.
It's sad, that he decided to travel around the country with the wheel and faced this bug during his journey.

Edited by WaveCut
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4 hours ago, WaveCut said:

That's not my wheel, but person is OK, littlle scratches only. Hes wearing an fullface helmet and elbow/knees protection.
It's sad, that he decided to travel around the country with the wheel and faced this bug during his journey.

Damn, so true...didn't realize that he was on such an awesome journey and stuck to a wheel with this problem, really sad and disappointing for him, I'm sure. 

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7 hours ago, Carlos E Rodriguez said:

So has the source of the issue revealed yet?  Has anyone have actual information on what is broken?

It sounds like there are a lot of very intelligent engineer types on this forum that would be an amazing asset for Gotway to utilize. You guys sound like you could not only diagnose the problems, but figure out the cause and work on solutions. As a typical pleb, all your engineering talk goes way over my head, but damn, I'd love to know the wheel companies are putting as much thought and passion into the wheel engineering as I see here, haha.

Hell, if they even read this forum (hello Gotway, if not, why not?) they would benefit I think.

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On 6/19/2017 at 4:06 AM, WaveCut said:

Multiple wobble cutouts on new Msuper v3s+ (7 occasions, 4 on video). Wheel gets wobble after some obstacle and cuts off.

 

this video is terrifying! i feel sorry for dude

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6 minutes ago, kour said:

this video is terrifying! i feel sorry for dude

You're not kidding. I hadn't watched it till now.  What a crummy feeling, I'm sure.

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1 minute ago, Dingfelder said:

You're not kidding. I hadn't watched it till now.  What a crummy feeling, I'm sure.

 

9 minutes ago, kour said:

this video is terrifying! i feel sorry for dude

Yeah, I saw this on Facebook I think. What was impressive was that he never gave up - gong-ho attitude :D  I would never ride that wheel again until I got a new control board. Impressive video footage.

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On 20.6.2017 at 7:05 AM, Carlos E Rodriguez said:

So has the source of the issue revealed yet?  Has anyone have actual information on what is broken?

gotway gave out a information that on a batch delivered from 1. may to 15. may, they changed something in the firmware....

As you can see....the Tests for that change are done by us delta-users ;-)

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