Replies to This Discussion

Permalink Reply by Lew Evans on July 28, 2011 at 6:34pm

By 330Hz and 490Hz , what do you mean?

Allen, where are you? I am in Sydney Australia.

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Permalink Reply by Allen Babb on July 28, 2011 at 6:44pm

I'm over in South Texas.

 

The 330 and 490 Hertz are the frame rates of the PWM signal sent to the ESC's. Hertz (Hz) is a number of "cycles per second" and can be equivalent to "revolutions per second" in certain applications, but Hz is usually applied to electromagnitic signals.

 

Put in some other terms, 330Hz means that for every second, 330 frames or pulses are sent to the ESC... for those not familar with PWM and R/C equipment, this is how the reciever communicates to servos and ESC's the desired angle or speed.

 

Having a high framerate is usually a good thing, because this means that whatever is hooked up to the reciever or whatever is generating the PWM can react at a quicker rate.

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Permalink Reply by Allen Babb on July 28, 2011 at 6:40pm

Oops! accendentally deleted a reply I didn't want to.

 

Original reply was to Lew... I did tests on a BP hobbies 18A ESC and came out with a frame rate of 330Hz. I heard that some had achieved a frame rate of 490Hz and I'm considering doing more tests to see if mine cane do that.

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Permalink Reply by Lew Evans on July 28, 2011 at 6:53pm

330Hz, frame rate or update rate ..... just checking.

Faster is always better.

What is the frame rate coming out of your controller? A faster ESC frame rate may not be worth looking into if it is already significantly faster than your controller.

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Permalink Reply by Allen Babb on July 28, 2011 at 7:15pm

I'm currently running the controller code at 50Hz, with my sensor code running at 110Hz. I'm using the ol' signals rule of thumb to use 2.2 times the desired signal (the same freq as the controller code) for the ATD.

 

It looks like the ESC's use the same rule of thumb, because it takes 110 frames in order for it to save a new maximum throttle frame width (PWM duty). As such, I think the ESC needs 2 or 3 frames before it will start to change the speed on the motor.

 

But, as far as I can tell, my "speed limit" is due to my sensors.

 

I'm looking at the datasheets for the sensors again, and see that the bandwidth for the accello's is 140Hz and the gyro's are 550Hz. The way that my sensor code is setup (simple complimentary filtering), I can't really combine the sensor data if they're operating at different freq's.

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Permalink Reply by Allen Babb on July 28, 2011 at 6:52pm

Hey Aldo, what kind of input membership functions did you use?

Trapazoidal, Triangle, or possibly Guassian?

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Permalink Reply by MHefny on November 18, 2012 at 7:37pm

Hello, 

I hope u completed your project.... I am also interested in quadcopter stabilization, I developed HefnyCopterFirmware it allows switching from X to Plus mode abd vice versa without board orientation or the need to install any new firmware as well as many features... 

I came out with a suggested framework for quad control system, it aims to sort different sensors by usage, and clear the gery areas between them. I hope you find it useful. 

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