Aircraft Speed Control Saturation Module for Pitch Limiting
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Solution Overview
Problem
Conventional systems for controlling aircraft speed are complex and unreliable, as they require intricate limit prediction and avoidance methods to maintain airspeed within safe limits to prevent structural damage and stalling, which can be challenging to implement effectively.
Innovation Solution
A system comprising an outer-loop controller, an inner-loop controller, and a saturation module that limits the pitch target between upper and lower bounds based on the difference between the current airspeed and permitted airspeed limits, using airspeed filters to calculate these bounds, ensuring the aircraft operates within safe speed limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional limit prediction and avoidance methods are used to control aircraft speed, then airspeed limits can be maintained to prevent structural damage and stalling, but the system complexity increases and reliability decreases
Solution Approach 1:
The control system is segmented into distinct functional modules: outer-loop controllers for nominal pitch calculation, a saturation module for bound enforcement, and inner-loop controllers for actuator control. This modular segmentation simplifies the overall system architecture while maintaining reliable speed control through dedicated functional blocks.
Solution Approach 2:
The saturation module pre-calculates and enforces pitch bounds before the inner-loop controller generates actuator commands. By performing the limit avoidance action in advance at the pitch level rather than manipulating inputs or outputs of existing controllers, the system prevents limit violations proactively, improving reliability without adding complex real-time manipulation logic.
2Reliability
If conventional limit avoidance methods manipulate controller inputs or outputs, then airspeed limits can be maintained, but the control methodology becomes complex and difficult to implement
Solution Approach 1:
The saturation module acts as an intermediary between the outer-loop and inner-loop controllers. It receives the nominal pitch target, applies saturation logic to enforce pitch bounds based on current airspeed, and outputs the bounded pitch to the inner-loop controller. This intermediary approach maintains airspeed limits without requiring complex manipulation of controller inputs or outputs, simplifying implementation.
Solution Approach 2:
Instead of manipulating the traditional input-output dimensions of existing controllers, the invention introduces a new dimension by enforcing pitch bounds at the pitch level itself. The saturation module operates in the pitch domain, calculating and applying bounds before the pitch signal reaches the inner-loop controller, thereby avoiding complex input/output manipulation while maintaining limit avoidance.
Data Source
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AI summary
The invention relates to methods and systems for controlling the speed of an aircraft. The methods and systems disclosed herein are particularly advantageous for unmanned aerial vehicles. A system for controlling the speed of an aircraft, comprising: at least one outer-loop controller (21), wherein the/each outer-loop controller (21) is arranged to receive one or more target flight variables (11) and to output a nominal target pitch; an inner-loop controller (40) arranged to receive a target pitch and output a control signal (50) for controlling at least one aircraft control device; characterised by a saturation module (100) arranged to receive a nominal target pitch and to output a target pitch for the inner-loop controller (40), wherein the nominal target pitch is limited between an upper bound and a lower bound by the saturation module (100) to generate the target pitch.