Aircraft Autopilot Control Using Sliding Mode and Feedback Linearization
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Solution Overview
Problem
Existing aircraft control systems face challenges in efficiently controlling bank angles, heading angles, and altitudes due to their complexity and reliance on linearization of aircraft dynamics, which are not tailored to nonlinear flight conditions, making them time-consuming and costly to schedule.
Innovation Solution
The method employs a combination of sliding mode control and feedback linearization techniques to compute target rates for bank angles, heading angles, and altitudes, using thresholds and sigmoid functions to adjust control inputs based on error values, allowing for precise control of aircraft actuators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If linearization of aircraft dynamics about a nominal operating point is used, then control system design is simplified, but the system is not tailored to nonlinear flight conditions and requires complex parameter scheduling
Solution Approach 1:
The patent uses feedback linearization to transform the nonlinear aircraft dynamics into a linear form through coordinate transformation and control law design. This allows the control system to maintain adaptability to nonlinear flight conditions without requiring complex parameter scheduling, as the transformation inherently adapts to the current operating point
Solution Approach 2:
The patent replaces traditional mechanical parameter scheduling approaches with a mathematical transformation approach using feedback linearization. Instead of manually adjusting controller parameters across different flight conditions, the system uses a nonlinear transformation that automatically adapts to varying flight conditions, reducing design complexity while maintaining versatility
2Reliability
If tunable parameters are scheduled according to aircraft orientation and flight conditions, then desired performance across the entire operating envelope is achieved, but the task is time-consuming and costly
Solution Approach 1:
The feedback linearization approach is self-adapting to the current flight conditions through the nonlinear transformation. The control law automatically adjusts to maintain desired performance across the operating envelope without requiring external parameter scheduling, making the system self-sufficient and eliminating time-consuming manual tuning
Solution Approach 2:
The patent creates a universal control framework using feedback linearization that works across the entire operating envelope without requiring condition-specific parameter sets. The nonlinear transformation approach provides a single unified solution that handles multiple flight conditions simultaneously, eliminating the need for separate parameter scheduling for different operating regimes
3Ease of operation
If linearization about a nominal operating point is used, then control system implementation is easier, but the system does not account for nonlinear dynamics throughout the flight envelope
Solution Approach 1:
The patent applies feedback linearization which transforms the nonlinear system parameters into an equivalent linear form through coordinate transformation. This maintains ease of implementation using standard linear control techniques while simultaneously achieving high accuracy under nonlinear conditions by continuously adapting to the actual flight state through the transformation
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.