PWM or D/A for motor control??

[ahgu]

Any expert out there would know?
which one is preferred? what are the tradeoffs.

thanks
ahgu

 

[Stark]

You should be more practical;which kind of control do you wish to implement?
Everyway a PWM method is preferred.
Stark.

 

[ahgu]

I did some research:
PWM usually have 10bit resolution(1024) levels. 20Khz x 1k=20Mhz. if you goto 12bit resolution, you need 80Mhz clock.

But for DAC, 16bits is readily available. But it is a external component. Any uController that has 12bits DAC?

I need to do location position, My encoder has 512lines-->2k using quadrature encoding. How do I choose the PWM or DAC resolution??


thanks
ahgu

 

[johnyaya]

The resolution you speek of (10-bit PWM vs 16-bit DAC) isn't important for position resolution. The encoder resolution is very important. 10-bit PWM resolution (in my experience) has been good. Of course there are other factors to absolute position accuracy.

 

[Speedy]

On 2001-08-31 17:26, ahgu wrote:
I did some research:
PWM usually have 10bit resolution(1024) levels. 20Khz x 1k=20Mhz. if you goto 12bit resolution, you need 80Mhz clock.

But for DAC, 16bits is readily available. But it is a external component. Any uController that has 12bits DAC?

I need to do location position, My encoder has 512lines-->2k using quadrature encoding. How do I choose the PWM or DAC resolution??


thanks
ahgu

Aghu,

I am using a 750 count PWM (about 9.5 bit) with 4000 line encoders with a TMS320LF2407. It implements the S-curve velocity profile, as well as the PID. Soon, I will be interpolating with a 9000 line encoder for a total of 1.4 million counts. I can tell you that the PWM resolution is not of the utmost concern. What is important is the encoder count, and the dampening of the PID control. Contact me on ICQ for more info. 5796988.

Speedy

 

[bunalmis]

PWM or DAC resolution

" I need to do location position, My encoder has 512lines-->2k using quadrature encoding. How do I choose the PWM or DAC resolution? "

If you want to use DAC, you must use analog power amplifier for motor driver. But another choice, you can use voltage to PWM converter for Bridge motor power driver.

You can select any resolution for PWM or DAC. If you increase the resolutuion of PWM, voltage ripple of control voltage and acustic noise decrease. Your motor characterisric very importand for PWM resolution selection.

Try by 8 bit and if you dont like the system performans then increase 9 bit .. 10 bit ..