Control Feedback Systems

Hey i have to do a report on control feed back systems and name a technology that uses this method. Im really new to the electronics world and would like to know of any suggestions. Does any one in here have any interesting articles on this subject that i can find online?

inverted pendulums are pretty sweet....but they arent a technology
CNC machining/milling are pretty cool too.

How about automatic HVAC building systems (heating/air conditioning)

Our school has it, it takes feedback from the different rooms and adjusts accordingly.

Good luck with your project.

-Infamous