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Not responding to the throttle when moving backwards

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jprojpro
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Last seen: 6 months 3 weeks ago
Joined: 2021-05-20 23:00
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Not responding to the throttle when moving backwards

Hello, everyone. I build a small e-bike for my daughter. It is built around geared hub motor with a clutch(no motor braking is possible when moving forward) and flipsky 4.20 controller. I'm using FOC and current control, throttle is ADC (hall sensor type).

Everything works just amazing, except for one minor thing. I was trying to find out how to fix this for ages and finally decided to ask here.

The issue is: when you spin the motor backwards it stops responding to a throttle input, it effectively switches off. You can even apply full throttle and it will do nothing. But as soon as the wheel stops moving backwards the throttle is alive again. If at that moment the full throttle is still applied - the controller will send max allowed current, resulting in a wheelie or really harsh acceleration.

How does it affect real world riding: so lets say we need to climb to the top of a really steep hill. Sometimes my daughter may slow down considerably and if she stops just for a moment and let the motor to spin backward even the slightest - the bike will betray her immediately, it will stop responding to the throttle and let her roll downhill backwards freely. It is kind of scary for her, as you imagine.

I have tried switching form current control to "duty cycle" control. This sort of works but in a somewhat weird way. As soon as you try to spin the motor backwards, the controller will detect it and will resist that movement. This resistance is pretty strong, it allows just to barely creep backwards, the faster you try to go the higher the resistance. As soon as the throttle is applied, the controller will try to reverse direction and move the bike forward, with is a desired effect.  

The perfect behavior would be:

If there is no throttle input, the motor should spin freely, allowing you to go backward and forward freely, without any resistance.

When the wheel spins backwards the throttle should act as a brake, modulating the stopping power and at some point in time switching from braking to accelerating forward.

For example: if you moving downhill backwards, gradually applying the throttle should result in deceleration, then stopping and then acceleration uphill. As I've said if you let go the throttle, the bike should be able to go downhill backward freely.

Is there a way to achieve this with a "current" control option enabled?