Wheelie/Stability Control via E-Brake Circuit?

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fatty   10 kW

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Wheelie/Stability Control via E-Brake Circuit?

Post by fatty » May 06 2021 5:29pm

I've often written that it's trivial to inadvertently power-wheelie a short-wheelbase, upright ebike. The resulting loss of steering input and progressive decrease in counter torque (making it easier to loop) is dangerous.

Most controllers already provision for throttle cut via a normally-open e-brake switch that closes upon mechanical brake application.
Has anyone considered or implemented wheelie control via the e-brake circuit?

This could be implemented via a normally-open switch in parallel with the e-brake switch:
-a mercury tilt switch that closes upon the front end rising past an adjustable angle. This would be simple to implement, but imprecise and prone to acceleration/shock-induced activation. This would provide only gross wheelie control.
-a switch that closes upon full extension (topping out) of the front suspension. This would provide true stability control by ensuring the front tire maintains contact. Could be implemented with a pull switch mounted to the fork crown and connected to the bridge.

Thoughts?

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E-HP   10 MW

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Re: Wheelie/Stability Control via E-Brake Circuit?

Post by E-HP » May 06 2021 11:43pm

fatty wrote:
May 06 2021 5:29pm
Thoughts?
I'd rather stay in full control. For instance, if I'm trying to cross a busy street/intersection, I'd rather ride out the wheelie than have the motor stop in the middle of the road.

fatty   10 kW

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Re: Wheelie/Stability Control via E-Brake Circuit?

Post by fatty » May 07 2021 12:41am

E-HP wrote:
May 06 2021 11:43pm
I'd rather stay in full control. For instance, if I'm trying to cross a busy street/intersection, I'd rather ride out the wheelie than have the motor stop in the middle of the road.
Yeah, I thought of that, and much depends on how fast the controller recovers. Rather than strict interrupt, it would be better to modulate power, as in commercial and race vehicles. Or at least design/program in hysteresis.

Riding a wheelie is inherently slower though. As the front angle increases, the decrease in counter torque reduces how much wheel torque can be applied before flipping the bike. This is why actual drag race vehicles don't (or try not to) wheelie -- it's slow.

In any case, just as ABS can stop a vehicle faster, I actually expect that even strict interrupt --if it recovered quickly enough-- may well accelerate faster. You could pin the throttle just past lift, and let the interrupt hold the fork right at full extension to preserve steering input.

Jonno   100 W

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Re: Wheelie/Stability Control via E-Brake Circuit?

Post by Jonno » May 07 2021 3:51am

See here:
https://evnerds.com/electric-vehicles/e ... ng-skills/

Using arduino and a giro is the way to go.

Jonno
Modified EEB frame, 888 forks, 280mm DNM pit bike shock, QS273 40h V3 3.5t, Nucular Electronics 24F controller 300a, 92V @ 36ah 26650 cells, 300a BMS with bypass,
Hope V4 + Galfer 223mm discs + Variable regen braking.
and 5 x QS205s

fatty   10 kW

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Re: Wheelie/Stability Control via E-Brake Circuit?

Post by fatty » May 07 2021 12:54pm

Wow, cool find. It doesn't appear on the Hubsink site though, so I emailed them to ask if the LCM is still under development.
I do think the LCM (and any accelerometer/tilt system) is more useful as a wheelie controller though.

If the goal is to keep the front tire in contact, then using the front suspension directly is ideal.
If you wanted to get fancy, a linear variable inductive transducer travel sensor would give position and thus acceleration, and allow predictive throttle shaping. But I'm not sure it would be sufficiently superior to a strict cut to justify the cost and weight.

It seems a strict cut would work well if the controller does not apply a throttle delay. Then, it would work better on a powertrain with high angular momentum like a heavy direct-drive rather than a light direct-drive, and probably better still on an elastic powertrain like a belt drive. It probably wouldn't work well on a light direct-drive or geared hubmotor.

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