Aircraft Flight Control Using Sliding Mode and Feedback Linearization
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Solution Overview
Problem
Existing aircraft control systems face challenges in achieving desired performance across the entire operating envelope due to the complexity and cost of tuning parameters based on nonlinear dynamics, often relying on linearization about a nominal operating point.
Innovation Solution
Implementing a combination of sliding mode control and feedback linearization techniques to compute target rates for bank, heading, and altitude angles, using threshold-based functions and sigmoid mappings to adjust control inputs dynamically, reducing the need for manual tuning and enhancing adaptability to flight variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If linearization about a nominal operating point is used, then control system development is simpler, but control performance deteriorates across the entire operating envelope
Solution Approach 1:
The control system dynamically adapts its parameters based on the current operating conditions. The gain scheduling mechanism continuously adjusts controller gains according to the aircraft's flight state (altitude, speed, angle of attack), transforming a static linearized controller into a dynamic system that maintains optimal performance across the entire operating envelope rather than being fixed to a nominal point.
Solution Approach 2:
The system changes control parameters (gains, feedback coefficients) based on operating conditions. By scheduling these parameters as functions of flight variables, the controller transitions from fixed parameters in linearization to variable parameters that adapt to different flight regimes, resolving the contradiction between simplicity and performance consistency.
2Reliability
If tunable parameters are scheduled according to aircraft orientation and flight conditions, then control performance across the operating envelope is improved, but system complexity and development cost increase
Solution Approach 1:
The continuous operating envelope is segmented into discrete flight regimes or regions based on key parameters (altitude bands, speed ranges, angle of attack intervals). The controller is divided into multiple gain schedules, each optimized for a specific segment. This segmentation approach reduces the complexity of continuous parameter scheduling while maintaining performance across the entire envelope.
Solution Approach 2:
The system implements feedback mechanisms that automatically select and switch between different parameter schedules based on real-time aircraft state measurements. This feedback-driven parameter selection reduces the manual complexity of parameter scheduling by allowing the system to self-adjust based on measured flight conditions, rather than requiring manual tuning for every possible condition.
3Reliability
If manual tuning of control parameters is performed, then control performance can be optimized, but development time and cost increase
Solution Approach 1:
Control parameters and gain schedules are pre-computed and stored during the design phase based on aircraft performance models and simulation data. This preliminary action eliminates the need for extensive manual tuning during testing and operation, as the optimal parameters are already determined beforehand through systematic analysis of the aircraft's flight characteristics across the operating envelope.
Solution Approach 2:
The control system is designed to self-adjust and self-optimize through automated gain scheduling algorithms that use real-time flight data. Rather than requiring continuous manual intervention for parameter tuning, the system serves itself by automatically adapting parameters based on predefined schedules and feedback from aircraft sensors, significantly reducing development and maintenance time.
Data Source
AI summary
Methods and systems for controlling a bank angle, a heading angle and an altitude of an aircraft during flight are provided. The methods and systems disclosed herein make use of sliding mode control and feedback linearization control (nonlinear dynamic control) techniques. The methods and systems can provide autopilot-type functions that can autonomously execute aggressive maneuvers as well as more gentle maneuvers for aircraft.