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Old 12-09-2016, 10:07 AM   #2919 (permalink)
thingstodo
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Quote:
Originally Posted by MPaulHolmes View Post
The encoder signal breaking is pretty catastrophic.
Sounds like the Leaf has the encoder well protected. The Siemens motor I tested with has the encoder internal to the motor casing so I expect it is a bit more difficult to damage.

My external encoders are really easy to damage. Alignment, vibration, coupling ... my DIY stuff is much less robust!

Quote:
So maybe if that happens, the controller could go into a coast mode where all IGBTs go off. Then whether it's permanent magnet or induction, it would just be like you lost power in a normal car, and are coasting.
That sounds pretty good. You may need some extra code to figure out whether the motor has no encoder when it begins to move or perhaps you are on a hill and need a bit more throttle to get the motor to rotate?

Quote:
Maybe then you could assume the motor is about the same RPM as it was before "broken encoder" happened. Then you could set the frequency/voltage to match what the frequency was before, and officially be in V/Hz mode for the purpose of limping home.
The switch from Field Oriented Control to V/Hz is sounding like a risk. Coasting to a stop, then starting out in limp mode on V/Hz should be an acceptable solution for as often as this should happen.

I'm not sure what I was thinking .. switching control methods while the motor is still rotating ... !!! .. my normal paranoia seems to have taken a short vacation.

Quote:
The newest board has a variable brake input. Just like a throttle. I'm not sure how useful it is. Tesla, for example, uses normal brakes, and has the throttle in a wig wag, with programmable max regen, but just stops the regen once the car has stopped. I don't know if everybody does that or what. Arber, do you have reverse from the transmission? I wonder how standard it would be for people driving a car with no reverse except for a button on their dashboard.
There are a couple of things to watch for with regen. When you are doing regen from the throttle, and then press on the brake, the brake needs to ramp up the regen from that regen point you are already at, not release the regen to 0 and start ramping again. That feels like pressing the brake gives you acceleration ... very disturbing!

And the regen only pumps power back into the batteries to a certain speed. After that you are using battery power to slow down your car and would be better off letting the friction brakes heat up a bit instead. That may be a bit hard to determine by calculations ... perhaps experimentally would be best and just enter the low speed cutoff into the configuration?

That could be tricky, as you have no control on when the friction brakes engage ... how much HIP you need to put into the brake pedal before the friction brakes start helping to slow the car.

Maybe I'm getting carried away again? Heck, we KNOW I'm getting carried away! That's what I do.
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MPaulHolmes (12-09-2016)