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Duty cycle mode with neutral

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titoxd10001
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Duty cycle mode with neutral

Hello, is it possible to get Duty Cycle control mode with neutral. Neutral so when you let go of the trigger it doesn't automatically try to brake for you. It's unusable for e-boarding at the moment.

Danny Bokma
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Yes this should be possible right out of the box (I use it), please take a close look at your configuration (or share yours with us so we can check). 

titoxd10001
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Under control type when I select : duty cycle it brakes when I let go of the throttle

When I select : duty cycle no reverse it doesn't seem to work and there is no motor movement

I'm using Focbox. Also when I changed to duty cycle my slave focbox was accelerating on its own while the master was stationary. When I change to "current no reverse with brake" it seems to be working fine. Didn't notice slave acting up last time not sure if made wrong setting after firmware update

benjamin
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Duty cycle mode should not be used for eboarding in general. Current control is probably what you want.

titoxd10001
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From what I understand every other esc uses Duty Cycle. For example I have experience with hobbywing escs. I much prefer the throttle curve of that esc vs current control. When I use current control I rarely use full throttle only on occasion when I want to go quick acceleration, but probably only use 1/4-1/2 throttle to get to 30mph speed. Even something as simple as going up a drive way is simpler for me with my single motor duty cycle equiped board vs my dual motor board with current mode equiped. It's just more intuitive for me. Im use to having to pull full tthrottle for full speed and having instant torque without having to jam the throttle. I would much appreciate duty cycle. Why wouldn't you recommend duty cycle?

benjamin
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Most hobby ESCs have duty cycle mode implemented without active freewheeling, so setting a lower duty cycle than the current motor back emf will not cause any braking (braking is actually not possible at all with that kind of modulation, so they use a completely different braking mode which makes terrible noise and is very inefficient). With BLDC and active freewheeling, or FOC which has a fundamentally different modulation technique altogether, duty cycle mode will always cause braking when setting a value lower than the back emf. There is support for running in BLDC mode without active freewheeling, which gives roughly the same behavior as crap ESCs without proper switching and current feedback, but it is less efficient and braking won't work properly.

Also, I can't imaging how duty cycle mode would feel better unless it is because you are used to it. Current is proportional to torque, and torque is what you feel. This gives the same feeling when using the throttle regardless of the speed you have, and you can always use the full throttle range. Duty cycle mode makes the acceleration you feel from a given throttle completely speed dependent and you have to be very gentle on the throttle at low speeds as you get full torque with a millimeter of throttle movement.

titoxd10001
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Yes that is exactly what I'm looking for actually, instant torque and speed based control. I find duty cycle more predictable when switching terrain or going up inclines or even just cruising around knowing I have all the throttle range to get to my top speed instead 1/2. It's personal preference. I think that's what evolve and boosted use. 

So it's difficult/not possible to implement due to hardware? How will braking suffer? Forum member said duty cycle is working for him but maybe it's not possible on Focbox?

RSR
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@titoxd10001:  You can try "Control type: PID Speed control" with only P-gain (set Speed PID Ki = 0).

titoxd10001
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I tried PID today. My slave just spins on its own while master is still. Strange this happens in duty cycle also but not in current mode. Forgot to do the (PID KI=0) so I wonder if that's the issue. After a bit though my master disconnected and couldn't connect until I disconnected my slave from it. A little frustrating so I'll give another shot in a few days. Might have to switch to y splitter to get it to work

titoxd10001
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With PID I get some weird noises coming from the motor. I wonder how Danny was able to get Duty Cycle to work with neutral

isabar
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I agree with the importance of this feature request.  I am the founder of Metroboard Electric Skateboard.  We are considering using the VESC in future Metroboard models, but the lack of Duty Cycle control with the ability to coast is currently a deal breaker.  In response to Benjamin's comment about "active freewheeling" above, I assume you mean "synchronous rectification" (SR for short).  Normally when driving a motor from a higher speed to a lower speed when using SR it will force the motor speed down which effectively brakes the motor which is undesirable on a skateboard where you really want it to coast or freewheel.  However, thermally it keeps the Mosfets cooler to run the motor with SR.  What we do to address this on the Metroboard Motor Controller: Normally we run with SR turned on, but we are constantly monitoring the battery current and if we ever sense the current goes negative (meaning the battery is being charged and regen braking is occurring, which will happen if you go from a higher to lower speed with SR turned on), we simply disable SR for that cycle, and this effectively allows the board to coast.  On the next cycle, we re-enable SR and again as needed disable based on polarity of battery current.  With all the sophistication of the VESC, I would imagine this should be a no-brainer to implement, unless I am missing something.  Would really like to see this implemented on future firmware versions (regardless of some people's preference of Current/Torque Control).

-ILAN SABAR

Metroboard Founder and Owner

Roger Wolff
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Pure dutycycle control mode is not nice to ride. But if you like it, be my guest. 

In FOC mode, as far as I can see dutycycle mode will command a current and try to reach the specified dutycylce. An optional "keep current positive" would allow the coasting that you want. 

benjamin
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One way would be to run duty cycle control as usual in the forwards direction with a braking current limit of 0, and then switching to current control with the normal braking current limit when the trigger is pulled towards braking. I will have a look the next time I work on the firmware.

Badkad
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Did this ever get implemented? I want to buy the new 75v Vesc but this is a concern of mine and holding me back.

Filcas
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Hello Guys, 



we are building a machine that need a bit more precise control and also to be able to "free spin" the motors. Duty cycle offer us the possibility to control better the position, specially if the machine have no load on it.



If we use current control, the "free spinning" is good, but if the machine is empty, we can't get control of the speed. It simply goes 100% speed. We had already two crashes of the carrier due to this issue.

Anyone can help us achieving to use duty cycle and still have "free spinning"? Thanks

TechAUmNu
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If you don't need to brake then you can just set the Motor Current Max Brake to 0. Then duty cycle will work for accelerating and it should freewheel as it won't be able to brake.

(There is probably a more elegant way to do this)

Filcas
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Thanks for feedback.

I had done it already, and I tried again when I read your reply, but it does not work. Motor starts to "whisper" and it's still locked. I also put battery current max regen to 0, Same results.

Are we missing something? It's very dangerous for us to use the current control, due to the sensibility in the throttle when our machine is unloaded. We just broke another carrier due to this current mode that is very sensitive to the throttle input when no load on the machine. But is actually the only mode we can use with "free wheel" :(



Will be very nice for our application to have this new mode of "current smart reverse" but "duty cycle smart reverse".

If someone could help us to achieve this behavior, it will be much appreciated.

Thank you. 

spacewalker
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Hi guys 

Seems like I am also interesting brake function but cant find it , maybe some1  can  explain ?

I want to use   bicycle   brake disc   and  handle  with sensor 

so  once  brake is apply , motor should not be control by ESC , otherwise will overload ESC , and is doesn't make any sense 

E-bike  use  a typical controller with function like  that , when brake is apply, throttle is disconnect , like  in gokart  (if you ever drive) they always said -  when press  brake, do not  accelerate 

 

any advice  welcome 

Martin

BDJ
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Hello! 

Exactly as Filcas, I'm looking for a way to use duty cycle control with freewheeling on zero throttle. Because in my application, I want to control the motor speed even without load.

Filcas, did you find a solution? 

I tried a lot of parameters on vesc tool but none of them seemed to allow free spinning. 

I tried to modify the firmware, but I couldn't find a  workflow guide to do this. Is there a tutorial available and up to date?

I work on a VESC 4.20 with ADC input

 

Many thanks!