Hi Asaad,
You will want to use the MATLAB® support forums to get help designing DC Servo motors using Simulink®. If you would like learn how to design and tune a controller using a DC motor with LabVIEW, take a quick look at this excellent white-paper to help you get started.
Teach Tough Concepts: Closed-Loop Control with LabVIEW and a DC Motor
http://www.ni.com/white-paper/12944/en/
MATLAB® is a registered trademark of The MathWorks, Inc.
Aldo A
Applications Engineer
National Instruments