US Patent 7460916 Nonlinear system observation and control

An observation system configured to observe at least one known state variable of an observed system includes a plurality of filters that are configured to receive a system input, and generate the at least one unknown state variable. Generating the unknown state variable includes processing the system input, a plurality of known state variables, and a time varying mode vector. An inverse system configured to observe at least one inverse state variable of an original system includes a plurality of filters that are configured to receive a system input, and generate the at least one inverse state variable. Generating the inverse state variable includes processing the system input, a plurality of known state variables associated with the original system, and a time varying mode vector associated with the original system.