Most geometric control-design methods for nonlinear systems assume that all state variables are available for feedback in real time. Unfortunately, the entire state is usually too expensive or impossible to measure, and some form of estimation is necessary. Unlike linear timeinvariant systems, where the state-estimation problem is analogous to the control-design problem, the design of a stable observer is a significant and separate challenge in nonlinear systems.
Bibliographical noteFunding Information:
recipient of the CAREER Award from the National Science Foundation, the 2001 Outstanding Paper Award from IEEE Transactions on Control Systems Technology, the Ralph Teetor Award from the Society of Automotive Engineers, and the 2007 O. Hugo Schuck Award from the American Automatic Control Council. He can be contacted at the University of Minnesota, Department of Mechanical Engineering, 111 Church Street SE, Minneapolis, MN 55455 USA.
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