bldc motor speed control

[Manchested]

Hi,
I have sometimes seen the speed of bldc motor is controlled by proportion integral derivative control using microcontroller?
what is the reason of using it? can't we just measure the speed and then decrease/increase the pwm?

 

[nandhu015]

I would like you read and understand what PID (proportion integral derivative) is.

Here is a link
PID controller - Wikipedia, the free encyclopedia

 

[Manchested]

so i guess i just mentioned about p control?

 

[FvM]

so i guess i just mentioned about p control?

No. You mentioned a broad idea of a controller without specifying it's behaviour. You'll stumple upon the necessity of defining it more exactly at latest when you implement it.

I guess, measuring the speed actually means comparing it with a setpoint and determining the error. But how do you decrease/increase the PWM? How much and how long? Correcting it as long a deviation exists refers to an integral acting controiler. But applying a pure I control has a problem. It typically causes oscillations.

In other words, when you start to think about the details, you are right in the middle of control theory. It's good to know that others have thought about it before and solved the problems, you don't have a clue of yet.