Fail-Safe Shaft Positioning for Electromechanical Actuators
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Solution Overview
Problem
Electromechanical actuator systems in aircraft designs lack fault-tolerance, leading to instability and potential failure in the event of power or mechanical failures, as they do not have hydraulic fluid for damping, necessitating alternative fail-safe systems to maintain control surface stability.
Innovation Solution
A secondary fail-safe shaft positioning system using electromagnetic and mechanical spring forces to automatically return and lock electromechanical actuators to a predetermined position in case of power or mechanical failures, ensuring stability and accuracy of flight control surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If electromechanical actuators are used to replace hydraulic actuators, then device complexity and weight are reduced, but fault-tolerance and stability during failures are worsened
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a secondary positioning system that is pre-configured to activate when the primary electromechanical actuator fails. This secondary system includes springs and positioning members that are ready to engage and maintain control surface stability without requiring active intervention after failure occurs.
Solution Approach 2:
The patent utilizes parameter changes by transitioning the control surface from active electromechanical control to passive spring-based positioning upon failure. The system changes its operational state from powered to unpowered, allowing the spring force to become the dominant parameter for maintaining stability.
2Weight of stationary object
If electromechanical actuators are used, then plumbing and weight are reduced, but damping capability and stability after failure are lost
Solution Approach 1:
The positioning system is pre-configured with springs that provide immediate stabilizing force upon actuator failure, cushioning the transition to a failed state and maintaining control surface stability without requiring heavy hydraulic damping systems.
3Reliability
If a secondary fail-safe system is added to electromechanical actuators, then fault-tolerance is improved, but device complexity increases
Solution Approach 1:
The patent extracts the fail-safe function into a separate, independent secondary positioning system that operates independently from the primary electromechanical actuator. This separation allows the fail-safe system to be added without fundamentally redesigning the primary system, thereby limiting the increase in overall complexity.
Solution Approach 2:
The secondary positioning system serves multiple functions: it provides fail-safe positioning, maintains control surface stability, and can potentially assist in normal operation. This multi-functionality reduces the need for additional dedicated components, thereby limiting 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
The system effectively stabilizes flight control surfaces by securing them in a predetermined position during failures, reducing the risk of instability and enabling continued aircraft functionality, and can be reset automatically once the failure is resolved.
Implementation Method 1
A secondary fail-safe shaft positioning system using electromagnetic and mechanical spring forces to automatically return and lock electromechanical actuators to a predetermined position
Implementation Method 2
A secondary fail-safe shaft positioning system using electromagnetic and mechanical spring forces to automatically return and lock electromechanical actuators to a predetermined position
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
Provided is a shaft positioning system for an electromechanical actuator. According to various examples, the positioning system includes a shaft coupled to an electromechanical actuator. The shaft moves along a linear axis and the electromechanical actuator is free to translate during normal operation. An electromagnetic coil positioned around at least a portion of the shaft. The electromagnetic coil produces a magnetic field when electrical current is applied. A metal housing surrounds at least a portion of the electromagnetic coil. The shaft is placed in a predetermined position when the metal housing is in contact with a first magnet and translational motion of the electromechanical actuator is restricted when the shaft is placed in the predetermined position.