Need technical advice on how throttle controls motor power.

[Offroader]

I had some arguments about a nuclear controller I am using on another discussion forum specific to that controller. I had issues with how it was controlling the bike. I was right in my arguments but almost everybody seemed to not like what I was saying. I just can not understand why they are not seeing what I'm seeing here. Only one other person noticed the same exact issue.


This makes me want to ask you guys how does most controllers control the motor.

The nuclear controller has a few ways to control the motor, but i will talk about the way mostly everyone is using it and recommending to use it. They use it in torque mode and how this mode works is it controls the Phase Amps of the bike.

So for example. If you set your controller to 500 max phase amps, your controller will work like this.
press 25% of your throttle your bike will allow up to 125 phase amps.
press 50% of your throttle your bike will allow up to 250 phase amps.
etc. to 100%

The controller also limits your maximum battery amps, which I have set at 100 battery amps. So if the bike reaches 100 battery amps, it will not allow any higher phase amps or battery amps.

This is the issue I am having. It seems that the bike uses maximum phase amps when first starting off, so lets say that on full throttle from a dead stop my bike will peak at 500 phase amps, but probably for only a second or so.

however, if I'm riding at speed, above say 15MPH or higher, my bike will only use maximum about 150 phase amps, even if I full throttle my bike it will only use 150 max phase amps at speed or most of the time.

So what I notice is that when cruising at speed, about 25-30% of my throttle movement will give me full power. This means that there will be no throttle range from 30% - 100% at cruising speed, which means after I move the throttle 30% the throttle will do nothing after that. The reason for this is at 30% of throttle my bike is calling to use 150 phase amps, but if I press my throttle down 50%, it will call for 250 phase amps, but my motor will not be able to use 250 phase amps at these higher speeds. The reason may be because my controller is also limited to 100 battery amps because my BMS would trip and I had to set it to 100 battery amps maximum.



I would like to know from you guys is why have I not noticed this issue on other bikes?

Do other bikes use phase amps in the same way the nuclear controller uses phase amps to control the motor?

Am I right in that a throttle controlling phase amps only will be a problem like I am experiencing?

Thanks, open to all points of view here.

 

[amberwolf]

It depends on how the specific controller firmware is designed, *and* what limits have been setup by the user (if it's programmable).

For the typical ebike controllers, the throttle doesn't control amps of either battery or phase--it controls PWM of the motor, or voltage, sometimes called a "speed" throttle but it's not really controlling the speed as a percentage of that available, it's controlling the amount of voltage fed to the motor.

How the motor behaves in that situation depends on the controller's limiting, etc. If your'e starting up from a stop, and feeding it full throttle, it'll simply give it all the voltage available, and then the controller will do whatever battery current limiting it is setup and designed to do (because this type doesnt' usually have any phase monitoring).

If you give it say, 10% throttle, it gives whatever proportion of voltage that is for that controller, probably a linear relationship. Battery current limiting probably won't even kick in if the bike starts up and rolls, because it probably wont' be drawing enough current to do so.

On both variations, as you get closer to the max speed that amount of throttle will allow, current would drop off because back EMF is going up inside the motor naturally, and so will cancel out more and more of the voltage the cotnroller is putting into the motor, allowing less and less current to flow. At some point there will be equilibrium between input and BEMF and motor loading, so that current stabilizes at whatever is necessary for that voltage to maintain that much load.



On controllers that use the throttle to control current (sometiems called torque throttle), most of them seem to use it to control phase current, rather than battery current, especially if they are FOC.

So in the case of the first variation, assuming a straightforward relationship between things, full throttle is going to try to give full phase currents, up to the limit you have setup. If battery current limiting engages because it's limit is lower than that needed to do this, then you will only get as much power as that allows, and that may reduce your phase current. If as you get faster the BEMF cancelling out input to the motor lowers the battery current below it's limit, then the only limit in play now is the phase current limit, so if you're below that, then you will simply get as much phase current as the system can create based on the difference between the input voltage to the motor and the BEMF voltage, and the motor's phase resistance, and any other resistances in the motor side of the system.

In the case of the second variation, you'll only get 10% (assuming a linear response) of the phase current limit. Battery current limit probably wouldn't come into play, unless even 10% of phase current under those startup conditions would cause a battery current greater than the limit setup in the controller.

AFAICR, this is how Incememed's SFOC5 is setup. And AFAIK, also how the Lebowski system is setup (though you can choose throttle curves, making for a nonlinear response, so it isn't as simple if you do that)--I'll know more about that once I finish this project:
https://endless-sphere.com/forums/viewtopic.php?f=30&t=105711
and start using them.


But if the controller software is not written for a straightforward relationship between throttle and phase currents, etc., then you would need to find out from that specific controller's manufacturer (if they'll even talk to you; most won't) about how exactly their controller is designed to respond. If it's user-selectable for the relationship, and the manuals (if any) don't explain, you'd again have to ask the manufacturer. Or determine it experimentally.



It's all nuanced more than this, but I don't pretend to understand the math behind the different control algorithms, and couldn't explain that even if I did. You'd need someone like Lebowski to put it into words that even people like me might understand.

 

[E-HP]

This is the issue I am having. It seems that the bike uses maximum phase amps when first starting off, so lets say that on full throttle from a dead stop my bike will peak at 500 phase amps, but probably for only a second or so.

however, if I'm riding at speed, above say 15MPH or higher, my bike will only use maximum about 150 phase amps, even if I full throttle my bike it will only use 150 max phase amps at speed or most of the time.

Sounds like the ESC controls speed rather than torque or power. Maybe throw a Cycle Analyst or Arduino circuit in front of it:

https://www.pedelecs.co.uk/forum/threads/making-a-torque-throttle-instead-of-a-speed-throttle-for-a-cheap-controller.34117/
https://evmc2.wordpress.com/2014/12/05/controllers-speed-vs-and-torque-control/
https://endless-sphere.com/forums/viewtopic.php?t=78882

 

[serious_sam]

So for example. If you set your controller to 500 max phase amps, your controller will work like this. press 25% of your throttle your bike will allow up to 125 phase amps. press 50% of your throttle your bike will allow up to 250 phase amps. etc. to 100%
...
however, if I'm riding at speed, above say 15MPH or higher, my bike will only use maximum about 150 phase amps, even if I full throttle my bike it will only use 150 max phase amps at speed or most of the time.
...
So what I notice is that when cruising at speed, about 25-30% of my throttle movement will give me full power.
...
The reason may be because my controller is also limited to 100 battery amps because my BMS would trip and I had to set it to 100 battery amps maximum.
...
Thanks, open to all points of view here.

I have a Nucular 12F, and I understand what you're saying. However, the operation you describe is exactly what is supposed to happen.

Take a look at the grin motor simulator for reference. As an example, this is my setup: https://www.ebikes.ca/tools/simulat...t_150_250_0.01_T&mass=150&hp=0&frame=mtn_tuck
- Notice how the available torque (motor current) decreases as speed increases.
- So with the torque based throttle, the higher throttle settings have no effect as you go faster. That's just the way it is. There is not enough phase current available to make the requested torque (throttle position).
- From 0km/h to about 10km/h, torque is limited by the phase amp limit of the controller.
- Between 10-30km/h, the torque is limited by the battery current (battery current stays at 150A in that zone).
- Above 30km/h, battery current starts to drop. That's because the rising back EMF from the motor reduces the deltaV that pushes current through the motor. So the battery and motor back EMF is limiting the amount of current in that zone.
- I have logs taken from my 12F which agrees with the motor simulator within reason. One point of difference being that the field weakening changes things above maybe 50 or 60km/h.

Bottom line, you can't push 500A for the full speed range of the bike, because physics.

The Nucular has a throttle control method called speed+torque. In my understanding this makes the throttle behave more like a regular IC engine, but I don't know exactly how the algorithm works to convert throttle position to power output. Have you tried that setting ? I had some funny glitches with it, so I've stuck with torque mode, which I'm happy with.

 

[john61ct]

VasiliSk responded with great contempt when I enquired about using CAv3 with Nucular, along the lines of "we don' need no stinkin' badges!"

Not saying it could not be made to work, but I wouldn't expect any support in figuring out how to do so.