Design of nonlinear observer by a backstepping approach

A backstepping-like design approach for reduced-order nonlinear observers is proposed. The basic idea of this approach is as follows. First, an appropriate function of the state variables to be estimated is constructed. The next function of the state variables to be estimated is then derived by designing the previous nonlinear function observer. Finally the procedure terminates, resulting in a partial differential equation to be solved. If the resultant differential equation is solvable, then the observer can be calculated. The connection between observers with linear error dynamics and this approach is discussed. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 53–59, 1997