Dual Load Path Actuator With Failover Transmission Engagement
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Solution Overview
Problem
Existing flight control systems in aircraft face challenges in providing redundant actuators that are both safe and cost-effective, especially in distributed architectures, where a single actuator failure can lead to catastrophic events.
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 failure, then safety and reliability are improved, but weight and space requirements increase
Solution Approach 1:
The patent combines two transmission shafts (primary and secondary) into a single integrated actuator assembly sharing common components including the driver, housing, and engagement features. This merging approach provides redundant load paths while minimizing additional weight by reusing structural elements across both failure modes.
Solution Approach 2:
The engagement features are designed to serve dual purposes: during normal operation, the primary engagement feature transmits torque while the secondary remains disengaged; upon primary failure, the secondary engagement feature automatically engages to maintain actuator functionality. This multi-functionality ensures safety without requiring completely separate redundant actuators.
2Reliability
If redundant actuators are provided to prevent catastrophic failure, then safety and reliability are improved, but the actuator complexity increases
Solution Approach 1:
The actuator is segmented into distinct functional zones: the driver section, primary transmission path with first engagement feature, secondary transmission path with second engagement feature, and output section. This segmentation allows each component to be optimized independently while maintaining overall system simplicity through modular architecture.
Solution Approach 2:
Multiple transmission paths are merged into a single compact assembly sharing common components (driver, housing, bearings), reducing the overall complexity that would result from completely separate redundant actuators while maintaining the safety benefits of redundancy.
3Reliability
If multiple transmission shafts with engagement features are used, then fail-safe operation is improved, but the device complexity increases
Solution Approach 1:
The second engagement feature is pre-positioned and spring-loaded (or gravity-biased) to automatically engage with the second transmission shaft upon failure of the primary path, eliminating the need for complex detection and switching mechanisms. The system is prepared in advance to handle failure conditions.
Solution Approach 2:
The actuator automatically detects primary transmission failure through the disengagement of the first engagement feature and self-corrects by engaging the second engagement feature without external intervention or complex control systems, maintaining fail-safe operation through inherent mechanical design.
Data Source
Figure 1
Figure 2A~2B
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AI summary
An actuator comprising a first transmission shaft (25, 45) mounted to a driver (21, 42), a second transmission shaft (27, 47) mounted to the driver (21, 42), and an output shaft (18, 28, 48). The output shaft (18, 28, 48) comprises a first engagement feature (30, 50) and the second transmission shaft (27, 47) comprises a second engagement feature (29, 49) for engaging with the first engagement feature (30, 50). In a functioning condition, the first transmission shaft (25, 45) transmits drive from the driver (21, 42) to the output shaft (18, 28, 48), the second transmission shaft (27, 47) does not transmit drive from the driver (21, 42) to the output shaft (18, 28, 48), and the first engagement feature (30, 50) is rotationally separated from the second engagement feature (29, 49) by a predetermined angular gap (31, 51). In a permitted failure condition, the first engagement feature (30, 50) engages the second engagement feature (29, 49) to transmit drive from the driver (21, 42) to the output shaft (18, 28, 48).