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Roo Williams

Gotway Tesla Issue - Diagnosis Requested

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Posted (edited)
11 hours ago, FlyingRat said:

..guys this is the inherent of the “super hard “ pedal ride algorithm breakthrough that Gotway somehow unfold last year and It all begin with the Luffy ! There is nothing to worry about. Try this experiment! Switch to soft mode and do the test with your slanted leg rolling up and down! On your return leg you will find the oscillation highest! Now switch to mid mode and you will notice that the “vibration” become reduce and when switched to sport mode u will find that the “vibration” almost disappear or has been reduced much!!! The oscillation fm the electronics vibrate the pedal rod. I have just been reading and alerted to this tread because my client link me here to read of this “sensational finding” which actually is an inherent trait of the “new” Gotway firmware breakthrough success that begin it all with Marty fall that Gotway engineer “pay” the underworld to get those “code” fixed and later go on to overdrive to try make a different to its brand. Today everyone is shouting how great the new ride is? and the birth of this “vibration” fm the initial trial. Ask Marty to test it on the new X and surely you will find it there too if you keep trying to find the perfect Gotway! There is nothing wrong with the mechanics of thing and it is the “Code” or the Gene that you must be eventually get accepted it being Gotway.  And with further opinion coming onboard the “vibration” issue  gets overblown with some fiddling fixed, it seem an inherent gene have been fixed in lieu instead of just switching mode!

i just found that with the latest Apps update the inherent oscillation has almost gone away with my new testing and now only more pronounce on my MSV3SX!

In due process and time..the Codes will get more refine to the point that it will take a lot of computer energy to write to remove that vibration.

try it on KS or Inmotion and if u focus it long enough u will spot that vibration too!

this is just like music to audiophile! Instead of listening to the beautiful tunes you go searching for noises?

 

When you change modes the length of the feedback loop between motor and gyro is lengthened either through response time or increasing the number of gyro readings used to produce a value that alters the motor position (averaging/smoothing). If it doesn’t match the frequency of the board’s vibration, affected by the space in which it has to move, then it won’t oscillate.

The vibration is a symptom of a mechanical design oversight, not like we’re not used to them on Gotway. :) you can see it yourself if you open one up. It’s clear that the mechanical intention is that the washer clamps the alu plate the board is mounted on and holds it fast in the slot. If the alu plate is too short for the slot, potentially because it’s not cut as squarely as intended, the material removal caused by the cutting method isn’t accounted for, or because of expansion in the shell during injection molding it doesn’t quite work as intended. There’s no buffer material between the connection of washer/shell and alu plate to allow for any tolerances to measurements of the hard materials in manufacturing and that’s the oversight.

It seems that design pattern is being repeated across models, just a theory, but maybe the designer has the slot and plate measured perfectly in their CAD app, but when it comes to cutting, 1mm of material gets removed from the alu plate because of the blade, making it 2mm shorter than the slot overall.

Personally my issue didn’t happen at first I think because some stray silicone was helping to hold the board in place, but one day it suddenly started happening and made me start to wonder what was going on beneath my feet! Pretty unnerving if you don’t know why.

Either way, it’s an easy fix and I don’t mind that for the chance to ride the fastest machines out there! It’s just unfortunate that this can result in queries to resellers who have to try and deal with it. Not exactly the thing you want to tell your new buyers ‘oh yeah.. about that... do you have a screwdriver?’

 

Edited by Roo Williams

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Posted (edited)

A bit late to the game, but just had to mention one thing: the wheels do NOT use stepper-motors, but 3-phase BLDC's/PMSM's (brushless DC / Permanent Magnet Synchronous Motors). The driving "mechanism" is entirely different to steppers, and if you look at the motor, motor connector or the cabling, you'll see 3 phase-wires + 5 wires (Vcc, gnd, 3 signal wires) for hall-sensors going into the motor.

Edited by esaj
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Posted (edited)
32 minutes ago, esaj said:

A bit late to the game, but just had to mention one thing: the wheels do NOT use stepper-motors, but 3-phase BLDC's/PMSM's (brushless DC / Permanent Magnet Synchronous Motors). The driving "mechanism" is entirely different to steppers, and if you look at the motor, motor connector or the cabling, you'll see 3 phase-wires + 5 wires (Vcc, gnd, 3 signal wires) for hall-sensors going into the motor.

Good to know as a side note! In support of the theory behind this vibration effect, it's more about the movement of the motor (any type of motor) creating that feedback loop between the gyro/motor, causing the motor to move and the motor causing the gyro to move, repeated over and over until the buzzing sound is heard. The stepper example is my only frame of reference from past experience.

You've peaked my curiosity now though. Just had a quick skim about the 3phase motors here. Seems there's a feedback mechanism to absolutely index the motor (from the hall sensors) and the motor's electromagnetic coils are fired in sequence to pull the armature around, so aren't the basic principles for driving the same, the different being in the feedback of armature position with steppers only knowing their position relative to the number of steps pulsed since their start position, if that was saved in the control logic memory and the stepper hasn't slipped? I must read more and hope that this knowledge converges with some opportunity in the future haha!
 

Edited by Roo Williams
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24 minutes ago, Roo Williams said:

Good to know as a side note! In support of the theory behind this vibration effect, it's more about the movement of the motor (any type of motor) creating that feedback loop between the gyro/motor, causing the motor to move and the motor causing the gyro to move, repeated over and over until the buzzing sound is heard. The stepper example is my only frame of reference from past experience.

You've peaked my curiosity now though. Just had a quick skim about the 3phase motors here. Seems there's a feedback mechanism to absolutely index the motor (from the hall sensors) and the motor's electromagnetic coils are fired in sequence to pull the armature around, so aren't the basic principles for driving the same, the different being in the feedback of armature position with steppers only knowing their position relative to the number of steps pulsed since their start position, if that was saved in the control logic memory and the stepper hasn't slipped? I must read more and hope that this knowledge converges with some opportunity in the future haha!
 

Yes, the principle of operation is similar (permanent magnets and coils acting as electromagnets), and a BLDC can be run similarly in "steps" with the 6-step trapezoidal control. This produces a somewhat "jerky" and imprecise movement though, so what the wheels use (to my knowledge) is "Field-Oriented Control" (FOC). Instead of just turning on and off the coils, they are pulsed with varying pulse lengths to form a more sine-wave like signal in the coils. There are numerous application notes about the maths and software behind it, just Google for it if you're more interested.

A stepper is run, unsurprisingly in steps. Also, the steppers are physically larger size as they must withstand the full "zero-speed/full torque" -current when they hold the motor in place. They're "aimed" more at precise position control, rather than speed/torque control, where as BLDC's are generally used for the opposite. No feedback for stepper motor position is needed (although sometimes is used, with separate encoders), as long as the steps aren't being run too fast (ie. pulsing so fast that the motor hasn't actually turned to next step), but 3-phase BLDCs need to know the position so that correct phases can be energized, so they use hall-sensors (there are "sensorless" software designs also). Things get more wacky with regenerative braking, as the steppers are stopped just by energizing single coil at full current constantly (which heats it up a lot, as all the energy is burned up in the motor coils / driver transistors), but since it wastes a lot of power and the wheel motors aren't designed for that (the mosfets or the motor coils would likely overheat), they actually use the battery as a place to "dump" the braking energy. For more technical explanation, the best source I've found (not that I've looked for any others since finding this) has been here: https://electronics.stackexchange.com/questions/56186/how-can-i-implement-regenerative-braking-of-a-dc-motor   Although it speaks of single-phase DC-motor, the principle (to my knowledge) applies similarly to 3 phases, of course it becomes more complex because it has to be done with multiple phases. 

A long time ago I wrote a piece about the basics of BLDC's, but I'm hardly an expert in the field:

I think there are people in the forums that know a hell lot more about this than I.

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