Vibration in All axle motor in the 17km/h to 20 km/h range weird problem

[edben05]

Hi everyone,

I'm facing a rather unusual issue with one of my two Grin All Axle motors. It vibrates when I apply power or use regenerative braking, but only at speeds between 17-20 km/h. Outside of this range, everything works perfectly.

Here's what I've tried so far:

• Checked the wheel balance
• Ensured the tire is properly fitted
• Inspected all bolts and screws
• Adjusted PLL bandwidth and damping settings (although I'm not entirely sure about these adjustments)

I'm at a bit of a loss now—does anyone have any ideas or suggestions?
Before someone says contact Grin, I did and Justin is helping me out but I'm reaching here in case someone stumble upon a similar issue and as a fix.

NB: This is one of 2 motor; the other one, witch is identical, doesn't do this weird vibration, other then being annoying, its doesn't do any error code in Phase-runner suite and doesn't affect performance what so ever.

Thanks in advance!

 

[neptronix]

First time i've heard of it on this forum. Crossing my fingers you get a solution!

 

[edben05]

First time i've heard of it on this forum. Crossing my fingers you get a solution!

I know it sounds really strange, but the vibration from the motor is pretty intense—it travels through the suspension fork and into the handlebars. It’s not just a minor vibration; it’s quite strong. The good news is that it disappears quickly as the speed either increases or decreases. Of course, this only happens when power is applied; when coasting, there’s absolutely no vibration at any speed.

 

[neptronix]

Is that a non-suspension aluminum fork?

These kinds of motors have a certain kind of resonance at various speeds. On an aluminum fork, you will hear it; they're great amplifiers! But this resonance won't produce a ton of physical vibration unless something else is going on.

What kind of battery / phase current are you running and on what winding of all axle?

 

[amberwolf]

I"ve seen vibrations at specific speeds with various motors over the years. Some of them respond differently to different controllers, even with non programmable trapezoid types. I've only tried out three FOC controllers (the SFOC5 and two Phaserunner versions) and those with only a couple of motor types, so haven't dealt with the vibrations and trying to tune them out with the FOCs.


Some thoughts: despite the statement that they're identical:

If they're different winding versions, they'll respond differently to the same drive signals / etc at the same speeds.

If they're being used sensorless, they'll also behave differently than if using sensored.

Are they being used on different bikes? Perhaps there is a slight mechanical difference between the forks, or the headset tightness, etc.


AFAICT it's some form of resonance between the parts of the motor (stator, windings, bearings, covers, rotor), conducted thru the axle into the frame which can then amplify it. Some frames (or forks) amplify things more than others. Some poeple have used sprayfoam inside the frame tubing to dampen it when it isn't possible to tune it out. Others have wrapped old innertubes around the frame tubing and tied them down securely against the frame tubing surface to dampen it.

 

[edben05]

Is that a non-suspension aluminum fork?

These kinds of motors have a certain kind of resonance at various speeds. On an aluminum fork, you will hear it; they're great amplifiers! But this resonance won't produce a ton of physical vibration unless something else is going on.

What kind of battery / phase current are you running and on what winding of all axle?

Nope it's a aluminum suspension 120mm fork and I added photo both escooter I'm building are using allaxle SLW wind v3 with statorade and both scooter have identical forks, wheel and tire are both using a v6 phaserunner and both are using a 48volt 19amp battery with GA cell (just my white doctape to keep them cool in the sun makes them look weird)

 

[neptronix]

Okay.. you don't have the problem of putting too little power into the motor i imagine. ( this could intensify the vibration )

 

[edben05]

I"ve seen vibrations at specific speeds with various motors over the years. Some of them respond differently to different controllers, even with non programmable trapezoid types. I've only tried out three FOC controllers (the SFOC5 and two Phaserunner versions) and those with only a couple of motor types, so haven't dealt with the vibrations and trying to tune them out with the FOCs.


Some thoughts: despite the statement that they're identical:

If they're different winding versions, they'll respond differently to the same drive signals / etc at the same speeds.

If they're being used sensorless, they'll also behave differently than if using sensored.

Are they being used on different bikes? Perhaps there is a slight mechanical difference between the forks, or the headset tightness, etc.


AFAICT it's some form of resonance between the parts of the motor (stator, windings, bearings, covers, rotor), conducted thru the axle into the frame which can then amplify it. Some frames (or forks) amplify things more than others. Some poeple have used sprayfoam inside the frame tubing to dampen it when it isn't possible to tune it out. Others have wrapped old innertubes around the frame tubing and tied them down securely against the frame tubing surface to dampen it.

It's running in hall sensor mode, I didn't check headset tightness it's a good ideal, I will try your ideal for sure and see what happens

 

[edben05]

Okay.. you don't have the problem of putting too little power into the motor i imagine. ( this could intensify the vibration )

I'm outputting about 900watt in front and 500 watt in the back, now the more power gets in the more vibration in this specific speed range, 900watts at 15km/h even on steep hill with the 50 pound trailer doesn't vibrate at all if I hit 17 ... vibration begins until I reach 21...
Btw back motor is a saw20 on a baserunner z9 it's there for and extra push up those hills with the trailer, when I refer to both motor it's both front motor on each scooter if that helps clarify the post

 

[edben05]

Is that a non-suspension aluminum fork?

These kinds of motors have a certain kind of resonance at various speeds. On an aluminum fork, you will hear it; they're great amplifiers! But this resonance won't produce a ton of physical vibration unless something else is going on.

What kind of battery / phase current are you running and on what winding of all axle?

It's not about hearing it as the sound doesn't border, its more that it can be felt in the handlebars and in your feet thru the steel frame of the bike into the wood feet rest, only the fork is aluminum, the annoyance is not the sound but really the vibration in the feets and hands

 

[edben05]

I’ve settled on a PLL Bandwidth of 4, a PLL Damping of 6.5, and a Current Regulator of 1500. I also lowered the motor resistance from 123 to 119 and reduced the phase current from 90 to 85. The vibrations are much better now—still noticeable, but nowhere near what they were before.

Regarding the Statiator charger 48volt model I noticed something odd. Two new batteries I ordered start with force charge (as all my batteries do, they don't start automatically when plug in), then show as “charge complete” (expected voltage: 54.4 volts). However, when I disconnect and reconnect them to the bike, they’re at 53.4 volts—missing that 1 volt. For the older batteries, I assumed they had lost a bit of charge over time, but this issue with the new ones has me puzzled. Additionally, the older batteries never display the “charge complete” screen. They simply cut out, and the Statiator returns to the “connect battery” screen. Any one as and ideal? (cable resistance maybe)

 

[neptronix]

Batteries typically drop voltage a bit after being charged.
Battery voltage also rises during charging due to internal resistance. ( reverse voltage sag )

 

[amberwolf]

Regarding the Statiator charger 48volt model I noticed something odd. Two new batteries I ordered start with force charge (as all my batteries do, they don't start automatically when plug in),

If the satiator doesn't start at connection, it means it doesn't detect a voltage within the range of the profile you've chosen. Assuming the satiator does start correctly when connected to a known good and working battery other than these, that means either:
-- the profile is setup wrong for your batteries (expects a voltage either higher or lower than your batteries are at),
or
-- the batteries are not enabling their charge ports properly, either
-- because the BMS detects a fault with a cell or cells and is trying to prevent charge
or
-- because the BMS itself is defective or damaged****

etc.



****I have an old Luna pack that has some sort of firmware bug in the BMS where sometimes, for no detectable reason, it disables the charge port; this can happen at any point during charge or discharge. The discahrge port is still enabled in this situation, which it shouldn't be if the charge port was disabled for a real reason other than HVC (full battery). No wiring or cell faults, no connection issues from cells to BMS, etc. This problem never occurs to the discharge port (which does work properly to cutoff discharge if current or low voltage limits are exceeded).

then show as “charge complete” (expected voltage: 54.4 volts). However, when I disconnect and reconnect them to the bike, they’re at 53.4 volts—missing that 1 volt.

Are they measured with the same voltmeter? If not, different meters could easily read a volt difference if not calibrated to match throughout their ranges.

For the older batteries, I assumed they had lost a bit of charge over time, but this issue with the new ones has me puzzled. Additionally, the older batteries never display the “charge complete” screen. They simply cut out, and the Statiator returns to the “connect battery” screen. Any one as and ideal? (cable resistance maybe)

No "ideal" but some thoughts or ideas:

The way the satiator (and any other charger) determines end of charge for a lithium pack is normally that current drops below some threshold (a few mA).

If that current never drops low enough, either
-- the pack is still drawing more current, such as during balancing (common with aging packs whose cells are different properties and always end up at different voltages after usage and during charge),
or
--the limit in the satiator profile is too low for that pack (either because of parasitic draw by the BMS or any power meter, LEDs, etc, or because of cells with internal leakage defects) so the pack never drops below that.

 

[edben05]

If the satiator doesn't start at connection, it means it doesn't detect a voltage within the range of the profile you've chosen. Assuming the satiator does start correctly when connected to a known good and working battery other than these, that means either:
-- the profile is setup wrong for your batteries (expects a voltage either higher or lower than your batteries are at),
or
-- the batteries are not enabling their charge ports properly, either
-- because the BMS detects a fault with a cell or cells and is trying to prevent charge
or
-- because the BMS itself is defective or damaged****

I've just receive 2 new batteries out of my 4, and Grin always test them and send the results, I would be surprise to have something defective, my profile is pretty straightforward; full volt 54.4, bulk min start 27.2, bulk 38.1, complete charge current 0.15 amp (3amp speed) other is the same at 6 amp speed (fast charge)

Are they measured with the same voltmeter? If not, different meters could easily read a volt difference if not calibrated to match throughout their ranges.

I have two voltage reader on the bike the CA3 and a other one that's directly connected to the battery, they have a 0.3 volt difference.

The way the satiator (and any other charger) determines end of charge for a lithium pack is normally that current drops below some threshold (a few mA).

If that current never drops low enough, either
-- the pack is still drawing more current, such as during balancing (common with aging packs whose cells are different properties and always end up at different voltages after usage and during charge),
or
--the limit in the satiator profile is too low for that pack (either because of parasitic draw by the BMS or any power meter, LEDs, etc, or because of cells with internal leakage defects) so the pack never drops below that.

Would my profile explain something here? 2 out of 4 are brand new GA cell 21700 48 volt 14.5 amp pack, the other 2 are not that old by any mean they have about 5k KM, are the GA Cell 21700 48 volt 19 amp (from grin to) 2 years old.

the limit in the satiator profile is too low

What is the limit? Do you refer to the max voltage or full charge voltage ?

Thanks for your help BTW

 

[edben05]

Batteries typically drop voltage a bit after being charged.
Battery voltage also rises during charging due to internal resistance. ( reverse voltage sag )

Maybe it just that.. don't know never got to charge them to full since i got the statiator... still get good range but with my scooter build, i would love to have them to at least 54 volt so i can maximize range while not the best for the batteries, those GA Cell are tough and can take it, i don't mind having to replace the batteries after 80k-KM, I have to charge them every 100kM so that 800 charge cycle of full charge.