derate on reverse

[ManuFromParis]

Hello Johannes,

i've been using my freshly built 911 with a Tesla SDU and an i3 pack and I have a question :

- would it be possible to derate the POT when in reverse ?
Indeed, moving the car in reverse is quite tricky because it jumps more than expected and make reverse slow driving very tricky and almost dangerous (curb parking between cars is VERY tricky)

[jon volk]

I would argue your parameters need better tuning. Under no circumstances should throttle manipulation be tricky in low speed scenarios.

[arber333]

I would argue your parameters need better tuning. Under no circumstances should throttle manipulation be tricky in low speed scenarios.

With ACIM usually means too little boost or too much ampmin on start.

[arber333]

Hello Johannes,

i've been using my freshly built 911 with a Tesla SDU and an i3 pack and I have a question :

- would it be possible to derate the POT when in reverse ?
Indeed, moving the car in reverse is quite tricky because it jumps more than expected and make reverse slow driving very tricky and almost dangerous (curb parking between cars is VERY tricky)

You can setup derating in parameters and use a BMS pin to activate derate on demand. I use it to shift and i completely decouple regen and reduce torque to 70% for using transmission reverse.

[Isaac96]

I think the issue is that the SDU board doesn't have the BMS pin (it's used to control the temperature mux afaik). So maybe throtmax could be changed via CAN when in reverse? That would require an external microcontroller reading the reverse input.

[ManuFromParis]

With ACIM usually means too little boost or too much ampmin on start.

I am afraid you shall need to be a bit more specific, as I'm not yet totally familiar with every effect of parameters changes.
What is ACIM ?

[Isaac96]

ACIM referring to AC induction motor.
My induction motor sometimes jumps around at low speed (encoder noise) but it's generally very controllable. So hopefully you can reach the same or better level of tune.
Have you followed Arber's tuning guide? viewtopic.php?f=9&t=468&p=5187&hilit=fpconst#p5187

[ManuFromParis]

Ok, Thanks.
I think my issue is more about derating than artifacts at very low speed or low Pot position, even though that might be an issue as well on my car at the moment.

So I'll look into arber333's suggestion.

When you go forward, it's natural and you're used to it.
Going backward is alwasy tricky in a vehicule, plus you're twisted on your seat to look back, then I guess your feet movements aren't as precise.
Anyway you'll never want to go as fast on reverse as forward, that's why it seemed logic to me to derate the pot command when on reverse speed.

[Isaac96]

Absolutely. You can always edit the code to add a derating feature - Johannes might not want to add that to the general purpose firmware. Compiling instructions should be in Johannes' github repository (Linux is the easiest way).
-Isaac

[arber333]

ACIM referring to AC induction motor.
My induction motor sometimes jumps around at low speed (encoder noise) but it's generally very controllable. So hopefully you can reach the same or better level of tune.
Have you followed Arber's tuning guide? viewtopic.php?f=9&t=468&p=5187&hilit=fpconst#p5187

You could also try to further shield your encoder/resolver cable. Now with latest revision of sine code Johannes uses good filtering which can withstand a lot of hash in signal. However this means resolution can be coarse.
You definitely need to get a general parameters for your motor and start changing the key ones according to my procedure.

I think reverse should be derated too, but what is "reverse" in general? You need to set it up as such. Maybe you can use BMS pin if you want to also use turtle mode with your BMS. Then you need to setup your derating so that you will still be able to drive up some hill in reverse. Regen can be set to 0 with BMS pin. Those are two parameters in derating section:
bmslimhigh
bmslimlow

[johu]

Like said, no BMS pin on Tesla boards
Might introduce some throtmax for reverse when I feel like it. Still a bit surprised as in both my conversions throttle control is so precise that even in the low-geared reverse gear I can manouver much better than with any ICE car.

You could also wire up the cruise control switch and set "idlemode" to "cruise" and configure idle mode with low idlethrotlim and idlespeed to give you a bit of push once you enable the cruise control switch AND come off the brake pedal.