Duplex Rotary EMA Gearbox Layout for Jam-Tolerant Output Drive
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Solution Overview
Problem
Electromechanical actuators (EMAs) are prone to jamming, making them unsuitable for safety-critical applications in aircraft, and there is a need for a more reliable and fault-tolerant design to enable their use in primary flight control surfaces.
Innovation Solution
A duplex EMA architecture with a common gearbox and dual electric motors, incorporating brake assemblies and a unique gear structure that allows output control even in the event of partial jamming, ensuring continued operation and redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If EMAs are used to replace hydraulic actuators, then weight and cleanliness are improved, but reliability and suitability for safety-critical applications deteriorate due to jamming
Solution Approach 1:
The EMA is divided into two independent but coupled actuators (first and second EMA parts), each with its own motor and brake assembly. This segmentation allows one actuator to compensate for jamming in the other, maintaining reliability while keeping individual components lighter than a single redundant hydraulic system
Solution Approach 2:
The patent merges two separate EMA parts into a unified duplex architecture with a common second stage gearbox and shared output shaft. This combining allows torque and power to be aggregated from both motors while maintaining the ability to isolate and compensate for jamming in one component, resolving the reliability concern
2Reliability
If two separate actuators are provided per surface for redundancy, then reliability is improved, but weight and size increase
Solution Approach 1:
Two EMA parts are merged into a single integrated unit with shared components including the common second stage gearbox, output shaft, and housing. This merging provides redundancy through dual motors while significantly reducing weight compared to two completely separate actuator systems
Solution Approach 2:
The common second stage gearbox serves multiple functions: it transmits power from either motor independently, combines torque from both motors during normal operation, and provides a unified output interface. This multi-functionality reduces overall system weight while maintaining redundancy
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 ensures continued operation and redundancy, allowing EMAs to function at reduced speed and torque in the event of jamming, enabling their use in safety-critical applications.
Implementation Method 1
a first electric motor and a first rotary shaft extending along an axis and arranged to be rotated about the axis by the first electric motor
Implementation Method 2
a first brake assembly for applying a braking force to the first output shaft; a second brake assembly for applying a braking force to the second output shaft
Data Source
Figure 1~2
Figure 3
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AI summary
A rotary electromechanical actuator, EMA, comprising: a first EMA part (1) comprising a first electric motor (12) and a first rotary shaft (S1) extending along an axis and arranged to be rotated about the axis by the first electric motor, and a first 1st stage gearbox (10) providing a geared transmission from the first electric motor to the first output shaft, and a first brake assembly (14) for applying a braking force to the first output shaft; the EMA further comprising: a second EMA part (2) comprising a second electric motor (22) and a second rotary shaft (S2) extending along the axis and arranged to be rotated about the axis by the second electric motor, and a second 1st stage gearbox (20) providing a geared transmission from the second electric motor to the second output shaft, and a second brake assembly (24) for applying a braking force to the second output shaft; and the EMA further comprising an output (40) arranged to rotate with rotation of the first shaft and the second shaft; the EMA further comprising a common stage gearbox (30) providing a geared transmission between the first and second shafts and the output (40), the common stage gearbox being located between the first and second 1st stage gearboxes; wherein the common stage gearbox comprises: a first sun gear (32) in engagement with and driven by the first shaft (S1) and a second sun gear (34) in engagement with and driven by the second shaft (S1); a first intermediate gear (33) driven by the first sun gear; a second intermediate gear (35) driven by the second sun gear; and an outer gear structure (36) arranged to engage with the first and the second intermediate gears; wherein the outer gear structure comprises: a first outer gear part (37) that extends across and engages both the first intermediate gear and the second intermediate gear; and a second outer gear part (38) that meshes with the first intermediate gear and is engaged with and drives the output (40).