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JeremyW
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Re: MiM: Tricking the inverter for better performance

Sat Oct 04, 2014 7:41 pm

I'm starting to think a simple multiplier on the torque message may work, and we don't really need complex control code.

Over on the Honda Insight forum there is a relatively easy "analog" mod for higher electrical performance by artificially decreasing the sense current in the phase current sensors. This mod tricks the controller into thinking it's not sourcing enough current to the motor and to increase output. Since ABS drops regen current to 0 in the motor, there's no change to the traction control system.

In the leaf, we'd modify the torque by multiplying by a scaler and sending the new message (with correct CRC) to the inverter. So it would be like receive 1 send 1.25. You'd still have a delay in power, but it would be less of a hit since you'd still be getting a substantial increase overall and the amount of time that the acceleration is limited is only like two seconds. I do like the linear pedal feel of eco mode in the 2011-2012 cars, and this would keep the linearity with a larger slope.

Thoughts?
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miscrms
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Re: MiM: Tricking the inverter for better performance

Mon Oct 06, 2014 1:34 pm

If you go this route, I would start with something as simple as possible. Like a two port board that just passes unmodified messages back and forth. This would also be a great way to log traffic on both ports and better understand exactly which controller is sending which commands and when. Then you can start experimenting with modifying commands. I would plan to pass all commands unmodified except under specific conditions, and focus first on identifying the operating conditions during which you want to modify the torque messages and cook that into a specific logical test in code. Once that's working, you can experiment with different ways of modifying the message to see what works best. This approach should limit the amount of algorithm development you have to do, since the stock controller code will still be governing the vast majority of operating conditions.

Just remember, when you break the bus any failure in your software or hardware can do a lot more than break axles. It can result in a loss of your ability to control the electric drive. The result of which can be uncontrolled acceleration and death. You need to be very methodical, and have a specific plan in place to deal with that eventuality. Using custom code and consumer grade hardware in an automotive application its less of a matter of "if" failures will happen as it is a matter of "when." IMHO that's the problem with breaking the bus vs. spoofing. Your HW/SW has to work 100% of the time, there is no way to disable the mod once the bus is cut.

I really hope you can pull this off! I'm fantasizing about building something like a LoCost 7 or Morgan 3-wheeler, putting a Leaf drive train in a 1200-1400 lb performance platform where this type of mod would have a huge benefit :)

Rob

camasleaf
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Re: MiM: Tricking the inverter for better performance

Mon Oct 06, 2014 2:47 pm

miscrms wrote:Just remember, when you break the bus any failure in your software or hardware can do a lot more than break axles. It can result in a loss of your ability to control the electric drive. The result of which can be uncontrolled acceleration and death.


The inverter has one (or two) 12V feeds, I imagine that turning of the 12V supply to the inverter should put the electric drive in a safe state. Just need a big red round switchin the cabin that can kill the inverter 12V supply.
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miscrms
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Re: MiM: Tricking the inverter for better performance

Mon Oct 06, 2014 3:34 pm

Yup, an emergency kill switch is a really good idea. Replicating a known fault condition that forces the inverter to go to 0 output is also probably a good approach too. EV conversions often use an emergency kill that drops the HV contactors directly, but this has its own issues. The contactors are generally not intended to break contact while current is flowing. They are usually designed to do this under rated load at least once, but the resulting arc can permanently damage the contactor. Doing this multiple times can result in a welded contactor that will not open again.

Ideally you would have both a "soft kill" that shuts down the inverter via a controlled method that does not rely on CAN com, and a "hard kill" that drops the contactor as a last resort. The contactors should probably be replaced as a precaution if this switch is ever used.

Rob

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JeremyW
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Re: MiM: Tricking the inverter for better performance

Tue Oct 07, 2014 12:58 pm

miscrms wrote:If you go this route, I would start with something as simple as possible. Like a two port board that just passes unmodified messages back and forth. This would also be a great way to log traffic on both ports and better understand exactly which controller is sending which commands and when.
Yes, that's the intention. In fact, a device was already built to do that for the RAV4EV to isolate the charger messages. I understand driving is going to be much much less fault tolerant.

miscrms wrote:Just remember, when you break the bus any failure in your software or hardware can do a lot more than break axles. It can result in a loss of your ability to control the electric drive. The result of which can be uncontrolled acceleration and death. You need to be very methodical, and have a specific plan in place to deal with that eventuality. Using custom code and consumer grade hardware in an automotive application its less of a matter of "if" failures will happen as it is a matter of "when." IMHO that's the problem with breaking the bus vs. spoofing. Your HW/SW has to work 100% of the time, there is no way to disable the mod once the bus is cut.
Yes, it is a bit scary to be relying on a piece of hardware like that. I think the best kill switch will be to cut the 12V going to the inverter. I definitly won't be doing this on public roads to start. Any experimentation will be done on a dyno, for sure. Again my goal is to get this working in time for REfuel (electric car races) in June 2015. So I have some time to be methodical. :)
Former 2012 SL leasee 6/23/12 - 9/23/15
Now driving Honda Fit EV, License plate: CHADEMO
2000 Honda Insight for long trips

miscrms
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Re: MiM: Tricking the inverter for better performance

Tue Oct 07, 2014 7:11 pm

Awesome! Really look forward to watching your progress!

kevinleaf
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Re: MiM: Tricking the inverter for better performance

Mon Nov 10, 2014 5:08 pm

Something occurred to me on this thread and I thought I would share. The reason that the output is artificially lower from a standing start is probably because this will break the drive shafts or gears. They are probably not rated for that much torque. It is not because Nissan were trying to be buzzkills. Of course they could have had larger, heavy-duty components to handle that torque but all that drives the sticker price up.

Also consider what the real 0-60 time gain will be for this change. Its probably 0.2 seconds.

Just my $0.02!

Flashman
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Re: MiM: Tricking the inverter for better performance

Tue Jan 20, 2015 11:41 am

Any updates or progress with this? :?: :mrgreen:
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miscrms
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Re: MiM: Tricking the inverter for better performance

Fri May 15, 2015 4:26 pm

My conversion is well under way, I'm counting on you to sort this out JeremyW ;)
http://www.diyelectriccar.com/forums/sh ... 48730.html

Seriously though, if I can help let me know. As I mentioned in the general CAN decoding thread I recently bought a cheap dual channel CAN USB interface, which if I can get it working might be useful for this investigation. My Leaf will be going offline in a few weeks though when I start pulling the drive system, and down until I get it operational in the host vehicle.

Rob

Flashman
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Re: MiM: Tricking the inverter for better performance

Wed May 17, 2017 7:02 pm

Ping.

Just thought I would check in again to see if there was any new progress on this? or did you guys give up?
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