Enhanced NDI strategies for reconfigurable flight control

A recently proposed method of on-line control design for aircraft reconfiguration is modified to mitigate the effects of effector rate/position saturation and sensor noise in critical measurements while preserving some, perhaps reduced, level of flying qualities. The on-line control design, based on an incremental version of nonlinear dynamic inversion, does not require a complete aerodynamic model of the aircraft, but does require the local control derivatives along with feedback of accelerations and effector positions. Recovery from a variety of failure (stuck or missing effectors) is possible under the original design as long as the working effectors do not enter saturation for extended periods and critical measurements are relatively noise free - an unlikely situation. Here, an improved control allocator minimizes both effector rate and position, utilizing a multi-pass strategy to restore lost control power due to saturation using the remaining unsaturated controls. Command model flying parameters are adaptively manipulated online to comply with reduced levels of control power further reducing saturation. A classically designed compensator placed around each actuator underpins strategy to reduce jitter due to sensor noise in the control variable responses while preserving decoupling of original control. Improvements due to these modifications are demonstrated on an advanced tailless fighter.