George Ellis is Director of Technology Planning and Chief Engineer of Servo Systems at Kollmorgen Corporation, a leading provider of motion systems and components for original equipment manufacturers (OEMs) around the globe. He has designed an applied motion control systems professionally for over 20 years He has written two well-respected books with Academic Press, Observers in Control Systems and Control System Design Guide, now in its third edition. He has contributed articles on the application of controls to numerous magazines, including Machine Design, Control Engineering, Motion Systems Design, Power Control and Intelligent Motion, and Electronic Design News.