Application of nonlinear inverse methods to the control of powered-lift aircraft over the low-speed flight envelope

Abstract

This paper presents a summary of experience in the design of velocity vector control systems for operation of short take-off and landing (STOL) and short take-off and vertical landing (STOVL) aircraft over their low-speed flight envelopes. A nonlinear inverse control method developed at NASA Ames Research Center was employed to deal with the highly nonlinear, multi-dimensional aerodynamic and propulsion system characteristics that are inherent in these aircraft. The method partitions the control system into a command element that is defined solely by the dynamic response to achieve good flying qualities, and a nonlinear inverse element that computes the aerodynamic and propulsion control effector positions required to satisfy the pilot's commands and to regulate against disturbances. Experience gained at flight evaluations with a powered-lift STOL aircraft and in piloted simulation with a STOVL aircraft design indicates that this system design approach produces the desired flying qualities over the low-sp...