Distributed Thrust Array for Redundant VTOL Directional Control
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Solution Overview
Problem
Current VTOL aircraft face challenges in directional control, particularly during hover and vertical takeoff/landing due to downwash inefficiencies and complexity in controlling large wing surfaces, which affects stability and requires additional thrust stations or cyclic rotor control.
Innovation Solution
Aircraft equipped with a two-dimensional distributed thrust array featuring independently controlled propulsion assemblies with gimbals that can tilt about two axes, allowing for redundant directional control through thrust vectoring, and a flight control system that can autonomously counteract thrust vector errors by commanding symmetrically disposed propulsion assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If VTOL aircraft use large wing surfaces for forward flight, then forward airspeed and range are improved, but directional control during hover and vertical flight becomes difficult and requires additional thrust stations
Solution Approach 1:
The aircraft divides the thrust generation function into multiple independent propulsion assemblies distributed across the airframe. Each assembly can be independently controlled to provide directional control moments, eliminating the need for additional dedicated thrust stations while maintaining the large wing surface for forward flight.
Solution Approach 2:
The propulsion assemblies serve multiple functions: they provide forward thrust during wing-borne flight, generate vertical lift during thrust-borne flight, and create directional control moments during hover and transition. This multi-functionality eliminates the need for separate cyclic rotor control or additional thrust stations.
2Speed
If tiltrotor aircraft use fixed wing for forward flight, then speed and range are improved, but downwash inefficiencies occur during vertical takeoff and landing
Solution Approach 1:
The propulsion system is segmented into multiple independent assemblies distributed across the airframe rather than concentrated at wingtips. This distribution allows the propulsion assemblies to be positioned to minimize downwash interference with the fixed wing during vertical takeoff and landing, improving thrust efficiency.
3Loss of energy
If tiltwing aircraft rotate wing to vertical orientation for VTOL, then vertical thrust efficiency is improved, but control during hover becomes more difficult requiring additional thrust stations
Solution Approach 1:
Instead of using a single large rotating wing, the aircraft uses multiple smaller propulsion assemblies distributed across the airframe. Each assembly can be independently tilted and controlled, providing both vertical thrust efficiency and directional control authority during hover without requiring the wing to rotate to vertical orientation.
Solution Approach 2:
The propulsion assemblies with gimbals provide multiple functions: they generate vertical thrust when tilted vertically for efficient VTOL, and can be independently actuated to provide directional control moments during hover and transition phases, eliminating the need for additional dedicated thrust stations.
4Reliability
If aircraft use distributed thrust array with independently controlled propulsion assemblies, then redundant directional control and stability are improved, but device complexity increases
Solution Approach 1:
The flight control system merges the control of multiple independently actuated propulsion assemblies into a unified control architecture. The system integrates control of thrust magnitude, gimbal angles, and rotor speed across all assemblies, managing the complexity through centralized coordination while maintaining redundant directional control capability.
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 solution provides enhanced stability and control during hover and vertical flight, enabling safe operation even with actuator faults, and allows for seamless transitions between thrust-borne and wing-borne flight modes, improving overall aircraft safety and versatility.
Implementation Method 1
The rotor assembly is rotatable with the output drive of the electric motor in a rotational plane to generate thrust having a thrust vector
Implementation Method 2
Each propulsion assembly includes a housing having a gimbal coupled thereto that is operable to tilt about first and second axes
Data Source
AI summary
An aircraft has an airframe with a two-dimensional distributed thrust array attached thereto having a plurality of propulsion assemblies that are independently controlled by a flight control system. Each propulsion assembly includes a housing with a gimbal coupled thereto that is operable to tilt about first and second axes responsive to first and second actuators. A propulsion system is coupled to and operable to tilt with the gimbal. The propulsion system includes an electric motor having an output drive and a rotor assembly having a plurality of rotor blades that rotate in a rotational plane to generate thrust having a thrust vector. Responsive to a thrust vector error of a first propulsion assembly, the flight control system commands at least a second propulsion assembly, that is symmetrically disposed relative to the first propulsion assembly, to counteract the thrust vector error, thereby providing redundant directional control for the aircraft.