Suzuki Cappuccino

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tom3141
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Re: Suzuki Cappuccino

Post by tom3141 »

celeron55 wrote: Wed Dec 30, 2020 11:11 pm Can you collect a plot of fstat, id, iq, ud, uq of an acceleration from 0 to 40mph all the way to where the speed has plateaued so that we can see what FOC is doing when the car doesn't accelerate anymore?
I did this test today and have attached a plot. This was 0 to around 50mph on a fairly flat road with full throttle (once I'd begun moving). Contrary to what I said before, it would continue to accelerate, I just ran out of road. It just accelerates very slowly after the initial nice strong acceleration, any kind of incline limits the top speed massively.
plot3.JPG
I have also attached the current parameters I'm using. One thing I don't really understand is the throtcur parameter. I found last time that when I increased this to the maximum value of 10 it helped a lot. However, in theory I guess this means that at 100% of throttle it should be demanding 1000A. I'm obviously not getting anywhere near this so what is limiting the current? Is this all back EMF/field weakening related? Just seems that I should be supplying more current (at least during the first section of the plot) with 100% throttle acceleration.

I'm still having some overcurrent errors (even with the fault signal line from the Prius disconnected) when under load at low speeds or when releasing the throttle too quickly. It is also still jerky and very difficult to control at very low speeds. It's almost impossible to start from a standstill on a hill.

Any suggestions or advice much appreciated!
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tom3141
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Re: Suzuki Cappuccino

Post by tom3141 »

I’ve just noticed that Johannes released a firmware update last week that may help with the low speed jitter. I will try this and report back.

I’ve also been comparing my plot to Bexander’s. They appear to show exactly the same behaviour with mine just being at a higher frequency due to the higher pack voltage. Is there anything I can try with parameters to see if the performance in the field weakening region can be improved? Or does it look like this is just a characteristic of this motor and higher voltages will be needed?
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Re: Suzuki Cappuccino

Post by celeron55 »

As johu said in Bexander's thread (viewtopic.php?p=18453#p18453), uq and ud are maxing out, meaning the inverter is putting out maximum PWM, meaning the motor won't take more current without more battery voltage. The only thing that can be adjusted at that point is the Iq to Id ratio, but I'm thinking there's probably not much to gain there as this motor is fairly similar to what the FOC code has already been tuned for.

Increasing throtcur will help in the lower rpms where the motor is willing to take more current but 1000A should probably trigger an overcurrent event. Is your potnom reaching 100%?
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Re: Suzuki Cappuccino

Post by tom3141 »

I thought that might be the conclusion :(
celeron55 wrote: Sat Jan 16, 2021 11:25 pm Increasing throtcur will help in the lower rpms where the motor is willing to take more current but 1000A should probably trigger an overcurrent event. Is your potnom reaching 100%?
I think that maybe my idcmax value of 200A is limiting the input power so that even though my potnom is reaching 100%, the inverter is never supplying 1000A.

I guess it’s looking like I’m going to need to boost the voltage then. I could probably live with the top speed of around 50mph but my area is hilly and it just has no torque to maintain that speed uphill.

I believe the Prius Gen2 boost converter is limited to 30kW. Is this a rating from the components used or some kind of cut off from the Toyota control side? I’m actually wondering if 30kW might be enough for me anyway, at the moment, during the period where it’s maxed out, my DC current meter is indicating about 40A so around 13kW. During acceleration at lower speeds I’m not sure that I’ve ever seen the DC current exceed 100A.

What are the options in terms of using the Prius boost converter? I’ve had a quick skim through the forum to see if anyone has used one in this application but could only find references to using them for charging. Is there a simple way that I could just connect it up so that is constantly boosting the voltage to 650V or does it need control software etc?
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celeron55
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Re: Suzuki Cappuccino

Post by celeron55 »

What speed can it maintain uphill, and what's the slope percentage? Also, weight of the vehicle? This is very useful information for anyone considering the MGR for their application.

Didn't Bexander succesfully use some piece of code to run the boost converter? EDIT: Answer: He's using gen3 so it's not directly applicable here. It must be in gen2 you just need to feed it a PWM externally in some pin?

I guess everyone has their favourite sources for the converter power ratings but for example this publication https://info.ornl.gov/sites/publication ... b26762.pdf says 20kW for gen2 and 27kW for gen3. This random reseach paper http://web.eecs.utk.edu/~tolbert/public ... 2_qian.pdf says the gen2 converter is rated for 20kW peak but only 10kW continuous.

Based on this upgrading to gen3 would probably be a good idea altough again it's Toyota and nobody has tested it for this application. Maybe one could even parallel some of the MG1 phases with the boost converter to get more current capacity, or additionally even modify the case and parallel more inductors, aand maybe the battery side capacitor isn't beefy enough either, so more of those too. Frankly, seems like a task for myself if I decide to put my MGR in a vehicle.

EDIT: By the way, based on the first PDF the Lexus LS inverters would be quite interesting for boosted driving of small motors, as they say its boost converter is rated for 36.5kW. I do have a GS450H inverter laying around...
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Re: Suzuki Cappuccino

Post by tom3141 »

Thanks for the info Celeron, I will do some research.
celeron55 wrote: Sun Jan 17, 2021 11:34 am What speed can it maintain uphill, and what's the slope percentage? Also, weight of the vehicle? This is very useful information for anyone considering the MGR for their application.
I haven’t been able to do much testing on hills as due to the low speed jerkiness and occasional overcurrents. I struggle to start again if I stop on a hill so I think I need to figure out this problem first.

I don’t have an exact weight for the car. Stock it has a 725kg kerb weight. I think it will be around 800kg kerb weight now so let’s say 900kg on the road with a driver.

The way it currently feels I’d say the MGR could be used as it is (at 300V) for a city car if the vehicle weighs under 1000kg and you’re happy with a top speed of 40-50mph. I’ll post details on performance on hills when I am able to test properly.
tom3141
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Re: Suzuki Cappuccino

Post by tom3141 »

Updated to 4.97 firmware and also played around with some of the parameters. I've reduced the throtcur back down and increased the throtramp back up. This combined with the firmware update has made the low speed control much better.

I also did some testing on a hill. I started from a standstill on a hill (approx 500m long with a constant 7.5% incline). At full throttle I was able to accelerate up to a maximum of 20mph and maintain that. This is the plot:
plot4.JPG
This shows the phase current peaks at 250A (my throtcur was set at 3 so seems about right). Also that the peak DC current is 50A so I'm only ever using a max of ~15kW. It seems odd to me that it drops off at such a low speed and that I'm not able to push more power into the motor.

I did some more top speed testing on a flat road too. I hit a maximum of 56mph (GPS measured) on a slight downhill. On the flat it is able to maintain 50mph at full throttle.
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Re: Suzuki Cappuccino

Post by celeron55 »

Let's check the physics: It's going up a 7.5% slope at 20mph (8.9 m/s). Ignoring wind and rolling resistance that should require the same power as going straight up at 8.9 m/s * 0.075 = 0.668 m/s, and that power is 0.668 m/s * 800kg * 9.81 m/s^2 = 5.24kW.

On the electrical side, 20A * 300V = 6kW. Well, that's a match, and also a reasonable efficiency given the inaccuracy of these measurements.

It needs more voltage, but the question is how much. My guess would be the voltage has to be increased as much as you want to increase the speed it can do in a given situation. To make it do the slope at 30mph, you need 300V * 150% = 450V, or for 40mph that's 600V.

Going up the slope at 40mph requires 10.5kW plus wind resistance, I'd say a total between 15 and 20kW, which should be boostable by any prius converter. A 600V battery sounds rather scary, so boosting makes sense. Rewinding the motor could also make sense, altough probably not.

Definitely an interesting case study.
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Re: Suzuki Cappuccino

Post by johu »

Just to get a better grasp, can you play with dmargin in both directions to see what influence it has? In like 500 digit steps. And maybe fwkp in 10 or 20 digit steps.

dmargin sets how much amplitude is left over to generate magnetising (iq) current. When set to 0 all amplitude is allowed to be used for field weakening. Which doesn't make much sense, it's just an extreme.

fwkp sortof sets the strength of field weakening. Or aggressiveness. Lacking a better term... controller gain anyhow.
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tom3141
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Re: Suzuki Cappuccino

Post by tom3141 »

johu wrote: Sun Jan 17, 2021 6:07 pm Just to get a better grasp, can you play with dmargin in both directions to see what influence it has? In like 500 digit steps. And maybe fwkp in 10 or 20 digit steps.

dmargin sets how much amplitude is left over to generate magnetising (iq) current. When set to 0 all amplitude is allowed to be used for field weakening. Which doesn't make much sense, it's just an extreme.

fwkp sortof sets the strength of field weakening. Or aggressiveness. Lacking a better term... controller gain anyhow.
Yes, I’ll test this when I next have some time. Thanks for the explanations, useful to get my head around.
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Re: Suzuki Cappuccino

Post by ZooKeeper »

Not to snipe this thread, but I have a different experience. I had no problem obtaining about 6000 RPM even at 160vdc, granted at no load. My understanding is that higher load causes more current and some voltage drop, but is it really going to be 50% of the supplied DC?

In the interest of extreme danger and research, I think I will see what the HV bus voltage is for a given control input to the boost converter.
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Re: Suzuki Cappuccino

Post by tom3141 »

ZooKeeper wrote: Sun Jan 17, 2021 7:28 pm Not to snipe this thread, but I have a different experience. I had no problem obtaining about 6000 RPM even at 160vdc, granted at no load. My understanding is that higher load causes more current and some voltage drop, but is it really going to be 50% of the supplied DC?

In the interest of extreme danger and research, I think I will see what the HV bus voltage is for a given control input to the boost converter.
I can obtain over 6000rpm no problem with no load. I was even able to achieve a few thousand rpm at 30vdc on a bench. It’s only when under load that the torque limitations become apparent.

My max speed today of 56mph is actually around 6000rpm. The issue is the lack of the torque available above 2000rpm.
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Re: Suzuki Cappuccino

Post by tom3141 »

I removed the boost converter inductor and IGBT module from the inverter when I first installed it in the car. I’ve just dug them out to have a look at them. There’s no markings whatsoever on the inductor but this is the IGBT module:
CA482120-097E-4148-A8D4-86DF45A37D7E.jpeg
Going from the Mitsubishi naming convention this appears to be rated at 1200V and 400A. I guess the inductor could be unable to handle this much but would seem a bit strange to me to spec the IGBT so highly if it couldn’t...
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Re: Suzuki Cappuccino

Post by celeron55 »

The gen2 boost converter isn't known for failing in normal use like the gen3 is, so maybe it's "sufficiently" overkill. How much? Well, I'll keep reading this thread. :mrgreen:
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Re: Suzuki Cappuccino

Post by johu »

Maybe I should allow the Gen2 controller to run the boost converter while in motoring mode... The auxiliary PWM would lend itself well - just set it to speed mode so it starts boost above a given rpm. You can try botching that in, basically disconnect TIM1_CH2N from the ULN2003 driver and connect TIM4_CH4. Then play with pwmgain and pwmofs.
I will need to run PWM slower, it is currently running at 17.6 kHz.
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Re: Suzuki Cappuccino

Post by Jack Bauer »

Yeah it won't like that frequency:)
I'm going to need a hacksaw
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Re: Suzuki Cappuccino

Post by johu »

So this would be the wire to add in order to optionally run booster PWM off TIM4_CH4. It uses the remaining channel of the ULN2003 making it backward compatible. Outputs need to paralleled, making it a wired-OR.

Let me know if you want to try this and I can make the necessary software mods.

Nevermind, wasn't much to change so test firmware attached. When detecting a Prius2 hardware it will clock TIM4 down to 8.8 kHz.

Parametrization:
pwmfunc = speed (2)
pwmofs = -1500
pwmgain = 0.5

The timer top value is 8192, with that it would basically short out the battery input, with 0 it does not boost at all.

So per rpm it would increase the timer value by 0.5. So say at 4096 rpm timer is at 2048 so voltage would be 25% boosted. Since it is not desirable to boost at low rpm you use pwmofs=-1500. Then there will be no boosting until 3000 rpm and then 0.5 digit per rpm. At 10000 rpm booster dutycycle would be 0.5*10000-1500 = 3500. So voltage almost doubled.

Now you can play with booster settings
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tom3141
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Re: Suzuki Cappuccino

Post by tom3141 »

Brilliant, thanks! I'm excited to try this out. I won't have time until Friday or Saturday but I'll keep you updated.

Just to make sure, I need to add a wire between pin 6 of the UL2003 (currently connected to TIM1_CH2) and TIM4_CH4 (the third pin along on the STM32) as shown by the thin black line on your drawing? Do I need to disconnect anything in addition to this?

Thanks again.
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Re: Suzuki Cappuccino

Post by johu »

Pin 6, what? No! Pin 3. Pin 1 is the one adjacent to R30. And bridge pin 13 and 14.

Will also try to run some tests in the meanwhile.
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Re: Suzuki Cappuccino

Post by ZooKeeper »

DIY EVs are like Tennis....

I cannot get any better unless I play with who are better than I :D

Thanks Johu!!!
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Re: Suzuki Cappuccino

Post by tom3141 »

johu wrote: Mon Jan 18, 2021 9:50 pm Pin 6, what? No! Pin 3. Pin 1 is the one adjacent to R30. And bridge pin 13 and 14.

Will also try to run some tests in the meanwhile.
That’s clear. I started looking at the schematic and confused myself I think. Thanks!
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Re: Suzuki Cappuccino

Post by tom3141 »

I tried adjusting the dmargin and fkwp parameters today. I adjusted both ways and couldn’t notice any difference at all.

I then started to have a look at doing the boost converter modifications. I got stuck trying to add the wire onto the pin on the STM32 chip. I don’t seem to have the skill/tools to be able to do this. As far as I can tell there’s nothing else on the PCB connected to this pin that I can use to connect to it? Or is there a trick to doing to soldering a wire to the pin?
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Re: Suzuki Cappuccino

Post by johu »

Ok, so we know that. Maybe time to strip out parameters on next release. dmargin that is.

I don't know a special trick besides a steady hand and fine soldering iron. I use very fine enamelled copper wire. And no the pin just ends up on a pad...
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tom3141
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Re: Suzuki Cappuccino

Post by tom3141 »

johu wrote: Sat Jan 23, 2021 1:48 pm I don't know a special trick besides a steady hand and fine soldering iron. I use very fine enamelled copper wire. And no the pin just ends up on a pad...
Ok. I’m going to see if I can borrow a finer soldering iron and fine wire from work.
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Re: Suzuki Cappuccino

Post by celeron55 »

Wire wrapping wire should work fine for this case, it's about 0.25mm in diameter. One trick is applying soldering flux separately. It helps in long and annoying soldering attempts as you can add more flux without adding more solder to keep the surfaces from oxidizing.
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