i plan to do my thesis of dc motor speed control by fuzzy logic in the phase locked loop. but i dunno how to design a phase-locked loop. can anyone help me?? thanks for ur kindly reply!!

 

Sounds like you chose the wrong topic for your thesis then.

Its not really the point of Control.com to do homework for you, but here is some links to get you started: (by the way, "PLL theory" in google turned up 21,000 links)
http://engineering-books-online.com/0070060517.html a book on pll theory
http://www.wavecrest.com/Japan/Advanced PLL_Asia03.pdf - brief intro on components flipchart style

Ya know.. honestly.. google it.. theres a boatload of info. If you are doing a thesis, I think you can afford to buy a book on the subject or hit the library. Not that I dont want to help or anything, but untill you have something working (or not working) we cant help you. Get to the point where you have a problem that you cant figure out, and have been scratching your head on, then ask again. The more specific to a particular problem you are, the more likely you will get a helpfull answer.

 

The basic principles of phase locked speed control you may find at Application Note U-113 from Unitrode, TI subdivision now.

BTW unlike Emery I think that you find right topic - phase locked speed control is needs for motor control application where very high precision speed is required.

Leonid

 

As your know in control theory you can you use the Phase margin to design a controller. Study up on it. Use the typical control theory with z transforms and s domain stuff to work out more then one solution to check that its working. And that step function stuff for stability.