Aircraft Longitudinal Control Using Normal Acceleration Cues
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Solution Overview
Problem
Scheduling and tuning control loop gains for aircraft longitudinal control across various flight conditions is complex and time-consuming, requiring efficient methods to manage pitch rate and normal acceleration cues effectively.
Innovation Solution
A method and system for computing a target pitch rate based on commanded normal acceleration, using a combination of feedforward and feedback controllers, and incorporating handling quality criteria like C* to control flight control surfaces, potentially with incremental nonlinear dynamics inversion, reducing dependency on aerodynamic models and enhancing robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If scheduling and tuning control loop gains for various flight conditions is performed using traditional methods, then handling quality can be maintained across different flight conditions, but the process becomes complex and time-consuming
Solution Approach 1:
The patent transforms the control approach by changing the fundamental parameter being controlled - instead of directly controlling pitch rate with scheduled gains, the system controls normal acceleration (a G-force measurement) which naturally adapts to flight conditions. This parameter change eliminates the need for complex gain scheduling while maintaining handling quality across the flight envelope.
Solution Approach 2:
The control system uses naturally occurring pilot cues (normal acceleration that the pilot can feel) as the primary control input. The system serves itself by utilizing the pilot's natural sensory feedback rather than requiring complex electronic sensing and processing, thereby simplifying the control architecture while improving reliability.
2Speed
If traditional pitch rate control is used, then control response can be achieved, but the system requires extensive gain scheduling to maintain performance across the flight envelope
Solution Approach 1:
The system pre-computes a lookup table of pitch rate commands corresponding to various normal acceleration targets across the flight envelope. During operation, the system simply queries this pre-computed table rather than performing real-time gain scheduling, eliminating time loss while maintaining fast control response.
3Reliability
If normal acceleration control is used at high velocities, then handling quality improves, but the control system becomes more sensitive to aerodynamic model variations
Solution Approach 1:
The system incorporates feedback from actual aircraft measurements (normal acceleration from accelerometers, pitch rate from rate gyros) to continuously adjust the control output. This feedback mechanism compensates for aerodynamic model variations and uncertainties, maintaining handling quality without requiring extensive tuning time.
Data Source
AI summary
Methods and systems for longitudinal control of aircraft during flight are disclosed. One method comprises receiving a commanded normal acceleration of the aircraft and computing a target pitch rate for the aircraft based on the commanded normal acceleration. The target pitch rate is used in a control technique for controlling one or more flight control surfaces of the aircraft to achieve the target pitch rate for the aircraft. The control technique can include (e.g., incremental) nonlinear dynamics inversion.