patriots21

Good day to all, I'm having a hard time grasping the idea of how current/torque control is achieved in 3-phase BLDCmotors which are driven using PWM signals. You see, I plan to implement dual loop control for each of my quadcopter's BLDC motor. An outer loop is for the voltage (speed) and the inner loop is for the current (torque).

Considering that a quadcopter's load is pretty much constant (i.e. its weight), how exactly is the delivered torque controlled. I have an idea on how this is all works for my application but I need external opinions for verification, so that's why I'm here.

First off, let's take out the off-the-shelf ESCs out of the picture. So I will be making my own motor driver, this is required for my application. The way I view torque control is simply limiting the maximum current draw of a particular motor. This is the first thing I want to verify: is torque control = current limiting.

As far as my experience tells me,BLDC motors are typically controlled by PWM pulses and that the larger the duty cycle, the faster my propellers spins. But how about the torque, is it constant as my load is relatively contant? PWM controls the motor by adjusting the average power that is delivered to it, right? So the way I view it for my application, is that the my external speed controller outputs some sort of a current required value to the internal current controller which then figures out what duty cycle is required based on this current value outputted by the speed controller and the feedback from the current sensor. Effectively, I should be controlling average power to provide a certain speed given a certain torque output, is that it?

The last thing I want to know/verify is in what way does the torque affect the flight of a certain air vehicle say a helicopter or a quadcopter?

I hope my questions are stated clearly enough. Inputs would be really appreciated. I'm new here, so please let me know if I crossed any of the lines that have been set here. Thanks.

e123

You would probably be better off posting this in the heli section instead of offroad.

SyCo_VeNoM

well it wouldn't really matter cause all BL motors, and ESC's work the same
You will just need to hit someone with the exact knowledge. I'll be honest back when I was in school we graced over BL cause it was still relatively new, and not widespread(Plus all the teachers I had didn't work in the field for 15+ years so their knowledge was a tad out dated)

Not 100% sure but the torque I would think is related to the current you are pumping in

e123

They all work the same but I was thinking more people would have experience running them in a quadcopter in the heli forum. Still no answers yet posting it here.

Maj_Overdrive

My Feedback: (11)

I know you said forget current production controllers, but I think this thread is a good read on how a manufacturer did it with their controller. They don't tell you exactly how it was done, but if you read other users post and how they skirt around some of what is said you can get a pretty good idea. I'm not a heli expert, but I'd assume having some sort of torque limiting would make it more stable with sudden throttle changes or just a hard sustained climb.

http://www.rc-monster.com/forum/show...TORquE+Control