Actuator Nut Assembly Failure Detection Using Piezoelectric Vibration Sensing
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Solution Overview
Problem
Existing actuators lack effective means to detect and identify the failure of the primary load path, which is critical for maintaining structural integrity and functionality, particularly in aerospace applications like trimmable horizontal stabiliser actuators.
Innovation Solution
Incorporation of a strain gauge, such as a piezoelectric strain gauge, to measure vibrations and a processor to identify the failure of the primary load path by detecting the engagement of a secondary load path, which engages upon primary path failure, using a nut assembly with a primary and secondary nut configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a secondary load path is provided for backup, then reliability is improved, but the ability to detect and identify primary load path failure is insufficient
Solution Approach 1:
The strain gauge is pre-installed on the actuator body to continuously monitor vibrations before actual failure occurs. This preliminary monitoring setup enables immediate detection when the primary load path fails and the secondary load path engages, resolving the contradiction by preparing the detection system in advance rather than adding complex real-time analysis mechanisms.
Solution Approach 2:
The invention utilizes mechanical vibration signals generated when the secondary load path engages after primary load path failure. The strain gauge detects these characteristic vibrations, transforming an otherwise invisible failure mode into a measurable physical phenomenon. This approach improves failure detection capability without compromising the reliability function of the secondary load path.
2Difficulty of detecting and measuring
If strain gauge is added to detect vibrations, then failure detection capability is improved, but device complexity increases
Solution Approach 1:
The actuator structure itself serves as the mounting platform for the strain gauge, utilizing existing structural components rather than requiring separate detection infrastructure. The system leverages the actuator's own operational vibrations as the detection signal, eliminating the need for additional excitation mechanisms or complex sensor arrays, thus improving detection capability while minimizing complexity increase.
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
Enables real-time detection and notification of primary load path failure, ensuring seamless transition to the secondary load path, enhancing safety and reliability in actuator systems.
Implementation Method 1
The strain gauge is a piezoelectric strain gauge
Data Source
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AI summary
There is provided a system for identifying a failure of the primary load path in an actuator (200). The actuator (200) comprises a screw shaft (210) and a nut assembly (400) moveable along the screw shaft (210). The nut assembly (400) comprises a primary nut (420) for transmitting load through the actuator (200) along a primary load path, and a secondary nut (440) for transmitting load through the actuator (200) along a secondary load path. The nut assembly (400) is configured such that, in normal operation, the secondary nut (440) is not engaged with the screw shaft (210) and load is transmitted through the actuator (200) along the primary load path, and such that, upon failure of the primary load path, the secondary nut (440) is configured to engage the screw shaft (210) and transmit load through the actuator (200) along the secondary load path. The system comprises a strain gauge (480) configured to be mounted to the actuator (200) and to measure vibrations of the actuator (200), and a processor (608) configured to identify a failure of the primary load path from the measured vibrations. The strain gauge is a piezoelectric strain gauge. There is also provided a method for identifying a failure of the primary load path in an actuator (200).