How to control duty cycle in PWM from signal control u to controlling dc motor

Hi friends...
I have a problem about PWM (Pulse Width Modulation) in MRAS design to controlling dc motor.

I have the algorithm to get control signal,
u(k)=c1(k-1)y(k-1)+c2(k-1)y'(k-1)+c3(k-1)r
e(k-1)=y(k-1)-ym(k-1)
c1(k-1)= - sigma from i=0 to i=k-1 {e(i)y(i)
c2(k-1)= - sigma from i=0 to i=k-1 {e(i)y'(i)
c3(k-1)= - sigma from i=0 to i=k-1 {e(i)r(i)

This Algorithm applied on PLC Siemens S7200 in STL. And this result giving U always decrease...
My problem is how to drive PWM from u (control signal). It means how to make the duty cycle value from u

More information :

>I have s Siemens PLC S7 200 series.
>I don't work in PWM mode, but I try with high speed counter
This program in STL:

Network 1
LDN M0.0
TON T32, +100

Network 2
LDW>= T32, VW50
= Q1.0

Network 3
LD T32
= M0.0

For example if the value of VD50 = +40, so PWM--> 60 on and 40 off.

>Base speed about 70% duty cycle.
>I have the algorithm to get control signal:
u(k)=c1(k-1)y(k-1)+c2(k-1)y'(k-1)+c3(k-1)r
e(k-1)=y(k-1)-ym(k-1)
c1(k-1)= - sigma from i=0 to i=k-1 {e(i)y(i)
c2(k-1)= - sigma from i=0 to i=k-1 {e(i)y'(i)
c3(k-1)= - sigma from i=0 to i=k-1 {e(i)r(i)

This Algorithm is applied on PLC Siemens S7200 in STL. And this result has U always decreasing...
My problem is how to drive PWM from U (control signal). It means how to make the duty cycle value from U.

You don't

zeta said:

My problem is how to drive PWM from U (control signal). It means how to make the duty cycle value from U.

Click to expand...

The timers are not fast enough, repeatable enough or have enough resolution. Real motion controllers use special chips to do this or at least the timers on the micro controller itself.

Look into something like this:

http://www.oesincorp.com/pwmmodule.htm

Control it with an analog output. As Peter said a PLC and it's output cards are not fast enough to do PWM directly.

Keith