Open-Loop Reference Systems for Nonlinear Control Applied to Unmanned Helicopters

Abstract

A novel way to design a nonlinear feedforward controller is presented. Contrary to input-output linearization and pseudo-control hedging techniques, the new formulation proposed is based on the states of the reference system instead of the plant’s states. By reshaping a commonly-used structure, the resulting scheme is used to produce a pure nonlinear feedforward system which is completely independent from system outputs. This permits the application of the presented control law when knowledge of the system states is not available. Due to the strict separation of plant and reference dynamics, stability of the reference system is no longer affected by the feedback of plant states. Results of flight tests of an unmanned helicopter, which are presented in this paper, demonstrate the applicability of this control concept.