Trim Stabiliser Actuator Layout With Harmonic Drive Fault Tolerance
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Solution Overview
Problem
Existing actuators in the aerospace industry require a smaller envelope, lighter weight, and higher reliability, particularly in applications where a single component failure could lead to catastrophic failures.
Innovation Solution
A trim horizontal stabiliser actuator design incorporating a harmonic drive gear arrangement and a fault-tolerant electric motor, with a passive brake and irreversible gear mechanism to prevent reverse rotation in case of failures, reducing the actuator's diameter and ensuring safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a conventional electromechanical actuator design is used, then the actuator can provide sufficient torque and linear motion, but the diameter of the actuator envelope becomes too large for aerospace applications
Solution Approach 1:
The patent implements nesting by placing the harmonic drive gear arrangement radially outwardly of the rotary shaft, with the electric motor positioned radially outwardly of the harmonic drive gear arrangement. This concentric, nested configuration allows all major components to share a common central axis, significantly reducing the overall actuator envelope diameter while maintaining sufficient torque output and reliability through the harmonic drive's inherent redundancy.
2Volume of moving object
If the actuator diameter is reduced to meet aerospace space constraints, then the envelope size becomes acceptable, but the risk of catastrophic failure from single component failure increases
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a passive brake configured to limit or stop rotation of the rotary shaft when engaged, and by designing the harmonic drive gear arrangement to inherently limit rotation when the electric motor is inactive. These preventive measures are built into the system architecture before failures occur, ensuring that single component failures cannot lead to catastrophic aircraft failures, thus providing fault tolerance without increasing actuator diameter.
3Volume of moving object
If a harmonic drive gear arrangement is used to reduce actuator diameter, then the envelope size becomes compact, but the complexity of the gear arrangement increases
Solution Approach 1:
The patent merges multiple functions into the harmonic drive gear arrangement by integrating it as a single component that simultaneously provides torque multiplication, limits rotation when the motor is inactive, and works concentrically with the rotary shaft and electric motor to minimize the actuator envelope. This consolidation reduces the number of separate components needed compared to conventional actuator designs, thereby reducing overall complexity despite the sophisticated nature of the harmonic drive itself.
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
The design achieves a compact, lightweight actuator with enhanced reliability and safety by minimizing the risk of catastrophic failures through dual redundancy and efficient power transmission, suitable for aerospace applications.
Implementation Method 1
a harmonic drive gear arrangement (106) extending radially outwardly of and coaxially with the rotary shaft (102) and an electric motor (104) positioned radially outwardly of the harmonic drive gear arrangement (106)
Implementation Method 2
the rotary shaft (102) may comprise a ball screw and the output component (108) may comprise a ball nut
Implementation Method 3
the trim horizontal stabiliser actuator (100) may further comprise a brake (116) configured to limit, or in some examples to stop, rotation of the rotary shaft (102) when the brake is engaged
Data Source
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AI summary
An electromechanical linear actuator (100) is provided. The electromechanical linear actuator comprises: a rotary shaft (102); a harmonic drive gear arrangement (106) extending radially outwardly of and coaxially with the rotary shaft; an electric motor (104) positioned radially outwardly of the harmonic drive gear arrangement, wherein the rotary shaft is configured to be driven by the electric motor via the harmonic drive gear arrangement; and an output component (108) configured to be driven along the rotary shaft in response to rotation thereof.