Segmented Drive Coupling for Fault-Tolerant Actuator Jamming
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Solution Overview
Problem
Electromechanical actuators face mechanical malfunctions such as jamming due to worn motor windings and bearings, leading to potential mechanical failures and the need for fault tolerance to maintain system functionality, especially in critical applications like aircraft and landing gear systems.
Innovation Solution
A segmented expandable drive coupling system that engages and disengages the actuating nut in response to a jam signal, allowing the actuator to free float or freefall, featuring a concentric drive housing with radially compressible and expandable segments, push plates, release pins, and springs to maintain or release torque transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a traditional electromechanical actuator uses a fixed drive coupling between the motor and ball screw, then the structure is simple and reliable, but the actuator cannot tolerate mechanical malfunctions such as jamming and requires complete replacement upon failure
Solution Approach 1:
The drive coupling is divided into multiple segments (at least two segments) that can independently move relative to each other along the screw axis. This segmentation allows the coupling to transition between engaged and disengaged states, enabling fault tolerance while maintaining a relatively simple overall structure that integrates with the existing actuator components.
Solution Approach 2:
The drive coupling transitions from a static fixed connection to a dynamic structure that can adjust its position along the screw axis. The segments are designed to move relative to each other, allowing the coupling to engage or disengage from the ball screw based on operational conditions, thereby providing adaptability and fault tolerance.
2Reliability
If the actuator maintains a rigid connection between motor and ball screw, then torque transmission is efficient, but the actuator cannot release the load during malfunction leading to potential damage
Solution Approach 1:
The drive coupling provides a dynamic connection that can transition between rigid engaged state for efficient torque transmission and a released state for safety. The segments are designed to move relative to each other, allowing the coupling to disengage from the ball screw when malfunction is detected, thus protecting the system while maintaining strength during normal operation.
Solution Approach 2:
The drive coupling acts as an intermediary element between the motor and the ball screw, providing a controlled connection that can be engaged or disengaged. This intermediary structure allows the system to maintain strong torque transmission when needed while providing a release mechanism for safety, resolving the contradiction between connection strength and safety.
3Reliability
If the actuator uses a segmented expandable drive coupling with release mechanism, then fault tolerance is improved allowing continued operation after malfunction, but the device complexity increases with additional components
Solution Approach 1:
The drive coupling is segmented into multiple independent parts that can move relative to each other, enabling the release mechanism to function with minimal additional components. The segmentation allows the coupling to disengage from the ball screw by moving segments along the screw axis, providing fault tolerance without requiring complex external release mechanisms.
Solution Approach 2:
The drive coupling segments serve multiple functions: they transmit torque during normal operation and provide the release mechanism for fault conditions. By integrating the release capability into the coupling structure itself rather than adding separate components, the invention achieves multi-functionality that reduces overall device complexity while maintaining fault tolerance.
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 controlled disengagement of the actuator from the load upon jam detection, ensuring continued functionality and safety in critical applications by allowing redundant actuators to manage the load effectively, preventing mechanical malfunctions and maintaining system integrity.
Implementation Method 1
a plurality of resilient expanding members positioned between adjacent segments to bias the segments into the expanded position
Implementation Method 2
a ball screw with a helical groove; a ball nut, also known as the outer race, with an internal groove; and one or more circuits of balls that recirculate in the grooves between the ball screw and the ball nut. This anti-friction design converts torque to linear force
Data Source
AI summary
An electromechanical actuator incorporates a drive housing connected to a motor for rotational motion. A screw is employed with an actuating nut having protruding engagement bosses and a drive coupling is concentrically received within the drive housing having segments equal to the number of engagement bosses. Each segment has a cavity to receive a respective one of the engagement bosses and the segments are cooperatively positionable from an active position radially compressed to engage the bosses within the cavities to a released position radially expanded to disengage the bosses from the cavities.