Nonlinear control design is appropriate when a control system's behavior is not well-modeled by linear ordinary differential equations. Nonlinear control can improve performance and robustness for systems that are described by nonlinear differential equations. Nonlinear control is useful in aerospace and ocean engineering because ocean, atmospheric, and space vehicles are expected to perform over large operating envelopes where dynamic models are nonlinear and uncertain. In general, nonlinear control design is quite challenging. However, mechanical systems (including vehicles) exhibit special structure that can be exploited in control design and performance analysis. Ongoing research focuses on the development of nonlinear control techniques for mechanical systems of practical importance, including ocean and atmospheric vehicles.
