VESC configuration for mid-drives

[pwd]

I'm playing with a Makerbase 75200 VESC based controller with a Cyclone 3000 motor on a normal 10 speed bicycle drivetrain and I cannot smooth initial acceleration with ADC current control. I've got throttle mapping adjusted how I like but when I engage the throttle I get an aggressive "clunk" in the drivetrain as the motor catches up to the rear hub's freewheel.

Running the ADC control type in "Duty Cycle" mode seems to solve the clunk problem and accelerates much smoother. The motor shaft starts spinning at a lower rpm compared to "Current" mode.

How can I improve the startup behavior while using "Current" for ADC control type?

 

[chuyskywalker]

You could play with that "Positive Ramping Time" setting there.

I've also sort of heard about similiar problems with geared hubs in which initial acceleration causes weirdness as the freewheel gets re-engaged. It's sometime solved by having the "off" position of the motor actually be sending a tiny amount of power (like .1A or something) so that the motor is always "engaged" but not enough to push the bike around. Maybe something like that could help here?

 

[scianiac]

Setting the throttle curve helps a bit, especially if the motor is powerful. The best solution I've found is setting the throttle range so that when the throttle is at rest it applies just a tiny bit of current to the motor (you have to disable the safe start), just enough so that the freehub is always engaged but it isn't enough to move the bike at all. When I stop for more than just a second I just have a kill switch on the bars. Honestly this feels way better than the alternative of having it ramp up slowly, the throttle lag from a slow ramp up sucks no matter what motor, driveline, controller, etc. And ramping up fast is violent both in experience and on the freewheel.

I'm trying to think of a better way to do this and so far I think either a system that turns off the motor after you come to a complete stop but then turns back on this idle power once you start moving would work. Or something like a throttle with a detent in it so if you turn the throttle backwards a little is clicks into a slightly lower position.

But if you don't want to do the motor always running setup I would change, the Positive Ramping, reduce the throttle deadzone if you can, and change the throttle curve to have a nice gradual start.

 

[Papa]

VESC Throttle Idle

Is there any way to make ADC throttle idle after release ? Thing is, I want to maintain constant tension on the drive chain in my mid-drive ebike. The way that I imagine it work is: when press throttle, accelerate, then release for few second, motor will maintain rotation on some low level...

endless-sphere.com

Delayed Startup with ADC Throttle | VESC Project

vesc-project.com

 

[pwd]

Great, I've got some reading/experimenting to do. Not sure how I missed that already existing VESC Throttle Idle thread in my searching but thank you for finding that.

I'm not keen on disabling safestart / having to use a killswitch when coming to a stop but all of your suggestions are pointing to the same idea; I will give it a try and see how it behaves.

Thanks for your input so far!

 

[scianiac]

I was pretty easily able to set the throttle up so it's consistently at the just barely any power level so I'm never worried about forgetting the killswitch or anything. Even just the lightest of braking will hold the bike while the idle power is on and my bike is geared absurdly low. Another option would be to wire the killswitch (which is just the other ADC port BTW) to a brake switch so when you stop it automatically cuts power and when you go to take off releasing the brake give the motor a half second of gentle power before you get to the throttle, then when you are moving power is nice and responsive but their will be a disengage and reengage if you tap the brakes but it should be pretty gentle as the current idle current is so low.

And if you don't like it I do think you can get the starting to be as smooth as you like with the ramp and throttle curve. The default minimum current is so low that if you command it accordingly it will go from driving not enough current to turn anything to barely enough pretty smoothly, you just have to give the motor enough time to spin up and engage everything and the controller can't do anything about that.

 

[bengxe]

I have no experience with VESCs or Cyclones, but it sounds to me like the problems you're describing here would be greatly reduced by zip tying the cassette to the spokes, unless your cyclone doesn't have a freewheel.