Question and suggestion about ampmin

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catphish
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Question and suggestion about ampmin

Post by catphish »

Last week while tuning my car, I attempted to use ampmin to set a minimum amplitude to reduce throttle dead zone. With the car stationary, I increased ampmin to approx ampmin=35, not enough to move the vehicle, but enough to eliminate the throttle dead zone.

Unfortunately this has a side-effect that when the car is moving, you get positive torque at zero throttle. This isn't surprising. The wiki states that ampmin sets a *relative* minimum amplitude, and hence when the motor is moving, it applies a much larger minimum voltage.

It seems to me that the purpose of ampmin is to apply a minimum voltage to the motor, but in reality it seems the result is just a minimum throttle position.

My question is: could we have "absampmin" in addition to "ampmin" that specifies an absolute minimum amplitude? This would allow the throttle deadzone to be eliminated when stationary by setting a more aggressive absolute minimum amplitude, but without applying so much minimum throttle at higher speeds. :idea:
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Re: Question and suggestion about ampmin

Post by johu »

This brings me to an open task.

It would be really cool if someone with a matching motor could take over software maintenance for the sine variant.
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Re: Question and suggestion about ampmin

Post by catphish »

johu wrote: Fri Nov 11, 2022 5:03 pm It would be really cool if someone with a matching motor could take over software maintenance for the sine variant.
It would be great if someone could keep working on this. I'd be happy to help where I can with this, but I don't currently have any hardware that's not embedded in a car. I'm happy to write code, but I'm not really able to test it. I realize that's not very helpful :cry:
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Re: Question and suggestion about ampmin

Post by johu »

So it's good that you have hardware embedded in a car because that's what I lack :) (in terms of asynchronous motors)

If it helps I can send you some old dev board.
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Re: Question and suggestion about ampmin

Post by catphish »

johu wrote: Fri Nov 11, 2022 6:41 pm So it's good that you have hardware embedded in a car because that's what I lack :) (in terms of asynchronous motors)

If it helps I can send you some old dev board.
Do you not have your original Polo conversion any more? That's very sad!

I guess in order to be able to bench test the stm32-sine, I would need the following:

* An STM32 dev board with IGBT drivers and current sensors
* A hex IGBT and DC bus caps
* A 230V induction motor
* Rotary encoder
* 300V of batteries and charger
* A current limiting device like a heating element
* A couple of contactors

None of these parts need to be large. When I developed my VFD a few years ago I used a 250W motor and HobbyKing batteries. Unfortunately I didn't keep any of that hardware (apart from the rotary encoder).

Perhaps I'll price up a dev kit.
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Re: Question and suggestion about ampmin

Post by johu »

When working with a Toyota inverter (e.g. Gen2) you can run the synchronous buck/boost converter to boost, say, a 48V battery to 300V. Since it is synchronous it will buck down any regen current to 48V and boost battery voltage to 300V to have a realistic motor behaviour.

The Gen2 control board can constantly run the converter with a fixed duty cycle that can be configured on the web interface.

EDIT:
In addition you could even run two motors with two controller kits. One with positive, one with negative torque.
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