Off-throttle-regen and a clutchless Gearbox

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markrmarkr
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Off-throttle-regen and a clutchless Gearbox

Post by markrmarkr »

I've heard that it can be a pain in the a$$ using off-throttle-regen when you have a clutchless gear box, because your controller tries to slow down the motor and this makes it harder for the synchros when you try to select a gear.

Does anyone have experience with this, and if so how did you get around it.

I have thought of a couple of options:

1. A push-button on the gear stick which puts a small voltage on the throttle input to the controller, so that it doesn't think its off throttle - just very very light throttle.   This has the added advantage of effectively letting you turn off regen if you want to coast while still being in gear.

2. I was thinking of using an Arduino to take motor rpm (from the controller) and vehicle speed (from the gearbox) and to make a feedback loop to adjust motor throttle so that they match. Obviously it would need to be adjustable depending on which gear you want to go into.   So it will get a bit complicated.   I'll probably need 4 or 5 push-buttons on the gearstick.

This brings back memories of my miss-spent youth. I had a 3 stage nitrous oxide setup controlled by push-buttons on the gear stick (actually it was a T-bar automatic).   It worked quite well - but how I survived my youth I'll never know.
MarkR

Driving a 2012 Nissan Leaf, Red - they go faster.
Autumn

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woody
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Off-throttle-regen and a clutchless Gearbox

Post by woody »

markrmarkr wrote: I've heard that it can be a pain in the a$$ using off-throttle-regen when you have a clutchless gear box, because your controller tries to slow down the motor and this makes it harder for the synchros when you try to select a gear.

Does anyone have experience with this, and if so how did you get around it.

I have thought of a couple of options:

1. A push-button on the gear stick which puts a small voltage on the throttle input to the controller, so that it doesn't think its off throttle - just very very light throttle.   This has the added advantage of effectively letting you turn off regen if you want to coast while still being in gear.

2. I was thinking of using an Arduino to take motor rpm (from the controller) and vehicle speed (from the gearbox) and to make a feedback loop to adjust motor throttle so that they match. Obviously it would need to be adjustable depending on which gear you want to go into.   So it will get a bit complicated.   I'll probably need 4 or 5 push-buttons on the gearstick.
2b. You only need to tell if you are going down or up, have a throttle input, blip the throttle means you are changing down?

3. Keep the clutch pedal (not the clutch) and make it a freewheel switch - pedal down = freewheel, pedal up = nothing.
This brings back memories of my miss-spent youth. I had a 3 stage nitrous oxide setup controlled by push-buttons on the gear stick (actually it was a T-bar automatic).   It worked quite well - but how I survived my youth I'll never know.
All I ever did was wire a switch in parallel to the kickdown switch at the bottom of the accelerator travel. On = stay in low gear. But there's not much you can get away with in your mum's car.
Planned EV: '63 Cortina using AC and LiFePO4 Battery Pack

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Johny
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Off-throttle-regen and a clutchless Gearbox

Post by Johny »

A combination of a few of the ideas just expressed.
Woody's clutch switch tells you that a gear change is happening. Any throttle depression means changing down, no throttle means changing up. That way it kind of matches what you would be doing normally.

Assuming a reasonably fixed ratio between gears it is then a simple task to predict the next motor RPMs required.
Changing down, increase motor RPM at the moment of clutch switch by 1.4 times. Changing up, decrease motor RPM by 1/1.4 times.
The throttle controls which way the motor RPMs will go while the clutch switch is down - kind a training the driver - they'll get it right soon enough.

EClubman
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Off-throttle-regen and a clutchless Gearbox

Post by EClubman »

If you want to get really fancy, a pair of pots and some linkages can give you gear stick X-Y position. With a little bit of applied Arduino, you don't need any buttons.
Moving out of gear - back off the throttle.
Moving towards next gear - spin motor to appropriate RPM given wheel speed and gear ratio to slot straight in.
Firmly in gear zone - allow full throttle

You could add a bunch more heuristics to guess what gear you will pick next depending on how you are driving at that point in time and beginning to adjust RPM appropriately while moving the stick out of gear.

Mark

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markrmarkr
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Off-throttle-regen and a clutchless Gearbox

Post by markrmarkr »

Some good ideas there - but maybe I should just do something easy like use the neutral switch in the gearbox to tell the controller not to apply regen. I could even put a half second delay on it to give the synchros time to engage.

What am I saying! This is the perfect opportunity to make things MORE complicated!   

One Arduino is not enough. I need another to do cruise control and act as the interface to the throttle input to the controller.

MarkR

Driving a 2012 Nissan Leaf, Red - they go faster.
Autumn

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