Strange cogging behaviour when rolling forward.

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Ev8
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Strange cogging behaviour when rolling forward.

Post by Ev8 »

Ok bit of an odd one here, on my tuning test drive route around the block I end up costing down a hill. At the bottom of the hill Is a T junction, I start braking and using regen as I approach the junction and all is good now if the junction is clear I let go of the brake and the car roles into the junction with the transmission winding the slack back the other way and pushing the motor, the road is steep enough to overcome the 10% off pedal regen I have (or maybe this isn’t active as motor speed is low) Now when this happens I get a cogging type noise like motor tuning being slightly out of alignment, when I accelerate up the road the motor remains noisy and I have to stop and restart then all is fine,

If I come to a complete stop at the bottom of this hill apply the handbrake enough to hold the car then pull away overpowering the handbrake and quickly releasing it as I start moving all is fine,

It’s like when the transmission winds everything back the other way things go out of sync, however it’s not an issue when regening at speed, just it would seem when rolling forward below the speed at which off pedal regen is active,


I can learn to drive around it, just wondered if anyone else had encountered similar
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Re: Strange cogging behaviour when rolling forward.

Post by johu »

Not happening here. Just a bit of vibration when rolling backwards in forward gear. But never had to restart.
Which SW version, settings, hardware? (I don't know all setups off the top of my head ;) )
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Re: Strange cogging behaviour when rolling forward.

Post by Ev8 »

SW 5.17
Prius gen2 inverter, 2 control boards to drive mg1 and mg2 separately, rx400h transaxle with modified case - diff and gear reduction removed, motors internally coupled and motor output via the transaxle input shaft, coupled to RX8 manual gearbox,

Will download the parameters to each controller tomorrow
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Re: Strange cogging behaviour when rolling forward.

Post by Ev8 »

MG1 parameters

{
"curkp": 32,
"curki": 20000,
"curkifrqgain": 100,
"fwkp": 0,
"ffwstart": 200,
"syncofs": 11975,
"syncadv": 6,
"polepairs": 4,
"respolepairs": 2,
"sincosofs": 2048,
"encmode": 4,
"fmax": 280,
"numimp": 400,
"dirchrpm": 100,
"dirmode": 1,
"snsm": 21,
"pwmfrq": 2,
"il1gain": 6.37,
"il2gain": 6.37,
"udcgain": 3.78,
"udcofs": 327,
"udclim": 540,
"snshs": 0,
"pinswap": 5,
"potmin": 1400,
"potmax": 4000,
"pot2min": 1500,
"pot2max": 4095,
"potmode": 2,
"throtramp": 2.5,
"throtramprpm": 20000,
"throtcur": 2.18,
"brknompedal": -50,
"regenramp": 0.18,
"brknom": 10,
"brkmax": -5,
"brkcruise": -30,
"brkrampstr": 20,
"brkout": -50,
"bmslimhigh": 100,
"bmslimlow": -1,
"udcmin": 270,
"udcmax": 316,
"idcmax": 600,
"idcmin": -100,
"idckp": 2,
"idcflt": 9,
"tmphsmax": 85,
"tmpmmax": 85,
"throtmax": 100,
"throtmin": -100,
"chargemode": 0,
"chargecur": 0,
"chargekp": 80,
"chargeki": 10,
"chargeflt": 8,
"chargepwmin": 0,
"chargepwmax": 90,
"idlespeed": -100,
"idlethrotlim": 10,
"idlemode": 3,
"holdkp": -0.25,
"speedkp": 0.25,
"speedflt": 5,
"cruisemode": 0,
"udcsw": 240,
"udcswbuck": 540,
"tripmode": 3,
"bootprec": 0,
"pwmfunc": 0,
"pwmgain": 100,
"pwmofs": 0,
"canspeed": 1,
"canperiod": 0,
"nodeid": 1,
"manualiq": 0,
"manualid": 0
}
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Re: Strange cogging behaviour when rolling forward.

Post by Ev8 »

mg2 parameters

{
"curkp": 32,
"curki": 20000,
"curkifrqgain": 100,
"fwkp": 0,
"ffwstart": 200,
"syncofs": 11975,
"syncadv": 6,
"polepairs": 4,
"respolepairs": 2,
"sincosofs": 2048,
"encmode": 4,
"fmax": 280,
"numimp": 400,
"dirchrpm": 100,
"dirmode": 1,
"snsm": 21,
"pwmfrq": 2,
"il1gain": 3.18,
"il2gain": 3.18,
"udcgain": 3.78,
"udcofs": 327,
"udclim": 540,
"snshs": 0,
"pinswap": 5,
"potmin": 1400,
"potmax": 4000,
"pot2min": 1500,
"pot2max": 4095,
"potmode": 0,
"throtramp": 3,
"throtramprpm": 20000,
"throtcur": 3.5,
"brknompedal": -50,
"regenramp": 0.18,
"brknom": 10,
"brkmax": -5,
"brkcruise": -30,
"brkrampstr": 20,
"brkout": -50,
"bmslimhigh": 100,
"bmslimlow": -1,
"udcmin": 270,
"udcmax": 316,
"idcmax": 800,
"idcmin": -100,
"idckp": 2,
"idcflt": 9,
"tmphsmax": 85,
"tmpmmax": 85,
"throtmax": 100,
"throtmin": -100,
"chargemode": 0,
"chargecur": 0,
"chargekp": 80,
"chargeki": 10,
"chargeflt": 8,
"chargepwmin": 0,
"chargepwmax": 90,
"idlespeed": 0,
"idlethrotlim": 10,
"idlemode": 3,
"holdkp": -0.25,
"speedkp": 0.25,
"speedflt": 5,
"cruisemode": 2,
"udcsw": 240,
"udcswbuck": 540,
"tripmode": 0,
"bootprec": 0,
"pwmfunc": 0,
"pwmgain": 100,
"pwmofs": 0,
"canspeed": 1,
"canperiod": 0,
"nodeid": 1,
"manualiq": 0,
"manualid": 0
}
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Re: Strange cogging behaviour when rolling forward.

Post by Ev8 »

Ok, car is on the road and MOTed so now I can do some further tuning and testing.

Firstly I’m going to lower the hz that regen is disabled below, as I’ve been testing rolling forward on a slope and it seems this issue appears when rolling forward with gravity at a motor speed that starts lower than regen threshold and then increases to be fast enough to start regeneration, at this point the regen is louder than normal and once I transition into positive torque I don’t get the normal smooth drive, something is not quite in sync, it almost feels like one motor is still in regen.. not sure on this I will do some further logging to try and see if this is the case, either way I’m hoping reducing the speed where the motor effectively freewheels might help here.

Im also wondering if this rolling forward whilst no pwm is being generated and it starting whilst motor is in motion is somehow is an issue?


In all instances stopping the car restarting makes everything normal again,


I’d also like to try and make some adjustments to help with very light throttle torque oscillation which has to be due to bouncing slack in the driveline

Can anyone briefly describe what the expected results of changes to these parameters might be before I mess to much!


"curkp": 32,
"curki": 20000,
"curkifrqgain": 100,

I get that they are adjustments to the current pi controller, but don’t understand enough about exactly what they do
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Re: Strange cogging behaviour when rolling forward.

Post by Ev8 »

Ok looks like the 2 issues where linked and related to me playing with the pi controller settings previously, I can’t even remember when I did but I must have changed curpk to 32, changed back to 64 and all seams well, also throttle response seems smoother
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Re: Strange cogging behaviour when rolling forward.

Post by Ev8 »

I haven’t actually got on top of this seems like the previous test was a fluke helped by raising the regen start point, it only happens when I start rolling forward from a standstill with no throttle applied, when starting to roll you feel the resistance of the magnets until the motor gets up to a certain speed where there’s a bit of a jolt and then I get this odd out of sync drive, almost like a fast torque oscillation that creates lots of cog like motor noise ( similar to the noise of having regen at too low rpm with the Prius inverter where it employs a 50/50 split at low amplitudes)

However just braking the car to a stop and pulling away again cures all.

When I’ve tried to log this it appears that motor rpm jumps straight from 0 to about 250rpm
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Re: Strange cogging behaviour when rolling forward.

Post by johu »

Will start testing this with the Audi soon. I've got the driveshaft adapters now
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Re: Strange cogging behaviour when rolling forward.

Post by Ev8 »

Awesome, I still can’t help but feel it’ll be something to do with the current control feedback fighting the small amounts of slack in each splined coupling and setting up some kind of sustained oscillation, probably unique to my build and the fact mg2 transmits it’s torque via mg1. Possibly won’t be an issue with the standard transaxle configuration.. time will tell, some kind of hill hold function that stops roll forward maybe might help, but I might have to implement this the abs system or go electric handbrake controlled with some simple wheel speed, throttle and motor rpm logic.
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