DC Motor is ringing

Thread Starter

Padderick

Joined Jan 7, 2012
13
Hi all together,

I have programmed an ATMEGA 32 to control a DC motor by a buck converter.
I have calculated the parameters and simulated them, everything has been fine.
After programming I started the motor and it controls the speed, but the unregularly. First it accelerates the motor, then the pulse width is very low and when the speed has fallen below the reference the signal gets very bride pulse width and the motor is ringing!

Hope somebody can help me,

- I have attached the code, if somebody thinks it could be a hardware problem just send me an email and I can send you my EAGLE circuit.

Thanks,

Padderick
 

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Thread Starter

Padderick

Joined Jan 7, 2012
13
But when I drive it with a normal PWM signal without controlling there is no ringing and the motor is quiet!!! When I control it also the DC link voltage goes up and down...
 

tshuck

Joined Oct 18, 2012
3,534
But when I drive it with a normal PWM signal without controlling there is no ringing and the motor is quiet!!! When I control it also the DC link voltage goes up and down...
What is a normal PWM signal and how is the one you are trying to use different?:confused:
 

Thread Starter

Padderick

Joined Jan 7, 2012
13
Normal PWM is when I drive the buck converter with e.g. f=15 kHz and a duty cycle of D=0.5. when I control the Mosfet by my speed control, the duty cycle changes due to the control signal calculated by the controller.

P.S. : I have saved the problem with the ringing by reducing the proportional gain of the speed controller.

Padderick
 

crutschow

Joined Mar 14, 2008
34,283
It would appear you may not have proper (on no) loop compensation. You need a PID controller as noted by Austin and tshuck. Without that, due to the inertial lag of the motor, the loop will constantly overcorrect and the speed will tend to go rapidly up and down (oscillate).
 
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