hi, i have face some problem to connect the pid controller to a dc motor model in simulink2009a.. i have connect the dc motor model with H-bridge. the diagram is attached below.can somebody tell me how to connect PID controller to the DC motor with required 3 loop ( current loop, position loop, speed loop). thanks.

simulink.doc

 

You might want to watch this webinar which shows how to do this:
http://www.mathworks.com/company/events/webinars/wbnr39764.html?id=39764&p1=679944543&p2=679944555

Also, you can use new PID Controller block in Simulink (starting with R2009b) and automatically tune it like shown and described here:
http://www.mathworks.com/company/events/webinars/wbnr38619.html?id=38619&p1=636028070&p2=636028082

http://www.mathworks.com/products/simcontrol/description2.html

http://www.mathworks.com/company/newsletters/digest/2009/nov/pid-control-design.html