Tiltrotor Flight Control System for Fuselage Attitude Stabilization
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Solution Overview
Problem
Current tiltrotor aircraft control methods experience undesirable pitch-attitude-to-vertical-velocity coupling, reduced controllability in gusty and windy environments, high response time, and passenger discomfort due to fuselage tilting during low-speed flight, especially when transitioning between helicopter and airplane modes.
Innovation Solution
A flight control system that commands nacelles to rotate for longitudinal and lateral thrust vector direction while maintaining desired pitch and roll attitudes using longitudinal and lateral cyclic swashplate controls, and differential nacelle rotation for yaw control, reducing the need for attitude changes and minimizing fuselage tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional flight control methods are used to change longitudinal velocity by pitching the fuselage, then thrust vectors can be directed forward or rearward, but pitch-attitude-to-vertical-velocity coupling occurs causing unwanted vertical motion
Solution Approach 1:
The control system segments the functions of longitudinal velocity control and pitch attitude control into separate control channels. Longitudinal velocity is controlled by nacelle rotation while pitch attitude is controlled by cyclic swashplate controls, eliminating the coupling between these functions that caused unwanted vertical motion.
Solution Approach 2:
The invention introduces nacelle rotation as an additional degree of freedom for controlling thrust vector direction. Instead of relying solely on fuselage pitch changes to control longitudinal velocity, the system uses nacelle rotation to independently direct thrust vectors, separating longitudinal control from pitch attitude control.
2Speed
If conventional flight control methods are used to change lateral velocity by rolling the fuselage, then thrust vectors can be directed left or right, but controllability is reduced in gusty and windy environments
Solution Approach 1:
The control system segments lateral velocity control from roll attitude control. Lateral velocity is controlled by differential nacelle rotation while roll attitude is maintained by differential collective blade pitch control, providing more reliable control in gusty environments by decoupling these functions.
Solution Approach 2:
The system dynamically adjusts control inputs based on flight conditions. In gusty environments, the control system uses differential collective controls to maintain stable roll attitude while using nacelle rotation for lateral velocity changes, adapting to external disturbances more effectively.
3Adaptability or versatility
If conventional flight control methods are used during mode transitions, then the aircraft can transition between helicopter and airplane modes, but response time is high and passenger comfort is reduced due to fuselage tilting
Solution Approach 1:
The control system segments the control functions to allow independent optimization during mode transitions. Nacelle rotation controls the transition of thrust vector orientation while swashplate controls maintain fuselage attitude, enabling faster response times and improved passenger comfort during transitions.
Solution Approach 2:
The control system prepares for mode transitions by pre-positioning nacelles and adjusting swashplate controls in anticipation of the transition. This preliminary action reduces the time required for mode transitions and minimizes fuselage tilting that would affect passenger comfort.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances control accuracy, reduces position displacements from wind gusts, decreases power requirements, and improves passenger comfort by maintaining desired attitudes during longitudinal and lateral movements, allowing for more precise and efficient flight operations.
Implementation Method 1
Each blade 15 has an airfoil cross-section, and lift is produced by moving blades 15 in a circular path as hub 17 rotates
Implementation Method 2
under the direction of the cyclic control, each swashplate assembly changes the angle of blades 15 on the corresponding rotor 13 individually as they move with hub 17, creating a moment in a generally horizontal direction
Implementation Method 3
lift is produced by moving blades 15 in a circular path as hub 17 rotates
Implementation Method 4
The unbalanced lift creates a moment that causes the pitch or roll attitude of aircraft 11 to change, which rotates the thrust vectors and causes aircraft 11 to move longitudinally or laterally
Data Source
AI summary
A method and apparatus provide for automatically controlling the flight of a tiltrotor aircraft while the aircraft is in flight that is at least partially rotor-borne. The method and apparatus provide for automatically tilting nacelles in response to a longitudinal-velocity control signal so as to produce a longitudinal thrust-vector component for controlling longitudinal velocity of the aircraft. Simultaneously, cyclic swashplate controls are automatically actuated so as to maintain the fuselage in a desired pitch attitude. The method and apparatus also provide for automatically actuating the cyclic swashplate controls for each rotor in response to a lateral-velocity control signal so as to produce a lateral thrust-vector component for controlling lateral velocity of the aircraft. Simultaneously, collective swashplate controls for each rotor are automatically actuated so as to maintain the fuselage in a desired roll attitude. The method and apparatus provide for yaw control through differential longitudinal thrust produced by tilting the nacelles.