Dual Load Path Actuator With Failover Shaft Engagement
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Solution Overview
Problem
Existing flight control systems in aircraft face challenges in providing redundant actuators that are both cost-effective and ensure high performance and safety, particularly in distributed architectures where multiple actuators are used, to prevent catastrophic failures.
Innovation Solution
A dual load path actuator design with a first and second transmission shaft, each with engagement features that disengage and engage to maintain functionality in case of failure, utilizing a planetary gear assembly and electric motor assembly to ensure continuous operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant actuators are provided to prevent catastrophic failures, then safety and reliability are improved, but weight and space consumption increase
Solution Approach 1:
The patent combines two load paths (primary and secondary) into a single actuator unit. The first and second transmission shafts are integrated within the same actuator housing, sharing common components such as the driver, planetary gear assembly, and housing structure. This merging approach provides redundancy while avoiding the weight and space penalties of completely separate redundant actuators.
Solution Approach 2:
The actuator is designed with multi-functionality where a single unit can operate in multiple modes: normal operation through the primary load path, and fail-safe operation through the secondary load path. The engagement features allow the actuator to automatically switch between functions, making one actuator unit serve the dual purpose of both primary and backup actuation.
2Reliability
If redundant actuators are provided to prevent catastrophic failures, then safety and reliability are improved, but the actuator occupies more space
Solution Approach 1:
The patent combines two load paths (primary and secondary) into a single actuator unit. The first and second transmission shafts are integrated within the same actuator housing, sharing common components such as the driver, planetary gear assembly, and housing structure. This merging approach provides redundancy while avoiding the weight and space penalties of completely separate redundant actuators.
Solution Approach 2:
The actuator employs a nested configuration where the second transmission shaft is positioned concentrically within or adjacent to the first transmission shaft. The engagement features are arranged such that the second load path is nested within the overall actuator structure, allowing compact packaging of redundant components without increasing the external footprint of the actuator.
3Reliability
If a dual load path actuator design is used, then fail-safe operation is achieved, but device complexity increases
Solution Approach 1:
The actuator is segmented into distinct functional modules: the driver, the first transmission shaft with its engagement features, the second transmission shaft with its engagement features, and the planetary gear assembly. This segmentation allows for systematic design and assembly, where each module can be independently manufactured and tested, thereby managing complexity through modularity.
Solution Approach 2:
The actuator incorporates dynamic switching capability where the engagement features can transition between engaged and disengaged states. The second transmission shaft is arranged to rotate relative to the output shaft, allowing the engagement features to automatically engage or disengage based on operational conditions, providing adaptive fail-safe operation without requiring complex control systems.
Data Source
AI summary
An actuator includes a first transmission shaft mounted to a driver, a second transmission shaft mounted to the driver, and an output shaft. The output shaft includes a first engagement feature and the second transmission shaft comprises a second engagement feature for engaging with the first engagement feature. In a functioning condition, the first transmission shaft transmits drive from the driver to the output shaft, the second transmission shaft does not transmit drive from the driver to the output shaft, and the first engagement feature is rotationally separated from the second engagement feature by a predetermined angular gap. In a permitted failure condition, the first engagement feature engages the second engagement feature to transmit drive from the driver to the output shaft.