APPLICATION OF NONLINEAR INVERSE METHODS TO THE CONTROL OF POWERED-LIFT AIRCRAFT OVER THE LOW-SPEED FLIGHT ENVELOPE

This paper presents a summary of experience in the design of velocity vector control systems for operation of short take-off and landing (ST OL) and short take-off and vertical landing (STOVL) aircraft over thei r low-speed flight envelopes. A nonlinear inverse control method devel oped at NASA Ames Research Center was employed to deal with the highly nonlinear, multi-dimensional aerodynamic and propulsion system charac teristics that are inherent in these aircraft. The method partitions t he control system into a command element that is defined solely by the dynamic response to achieve good flying qualities, and a nonlinear in verse element that computes the aerodynamic and propulsion control eff ector positions required to satisfy the pilot's commands and to regula te against disturbances. Experience gained at flight evaluations with a powered-lift STOL aircraft and in piloted simulation with a STOVL ai rcraft design indicates that this system design approach produces the desired flying qualities over the low-speed flight envelope in the pre sence of a wide range of wind and turbulence disturbances.