Jam-Tolerant Electromechanical Actuator with Damper and Disconnect
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Solution Overview
Problem
Electromechanical actuators face mechanical jam issues that prevent their use in primary flight control applications, requiring a solution to ensure reliable operation and fail-safe positioning in aircraft and other vehicles.
Innovation Solution
The development of a jam-tolerant electromechanical actuator system with a damper system for controlled rate of return to a fail-safe position, a ball nut disconnect system for decoupling during power loss, and a dual ball nut disconnect system for shared components and weight savings, incorporating stored energy mechanisms for self-resetting and ground testing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If electromechanical actuators are used in primary flight control, then actuation capability is improved, but mechanical jam risk increases
Solution Approach 1:
The actuator is divided into independent functional modules: motor assembly, ball screw mechanism, output shaft, and damper assembly. This segmentation allows the jam-tolerant feature to be implemented as a discrete module that can isolate failures to specific segments, preventing complete system failure from mechanical jams.
Solution Approach 2:
A damper assembly is introduced as an intermediary component between the motor and output shaft. This damper acts as a mechanical mediator that provides controlled resistance to motion, enabling safe fail-safe positioning when electrical power is lost or mechanical jams occur, without compromising normal actuation capability.
2Reliability
If damper assembly is added for fail-safe positioning, then reliability is improved, but device complexity increases
Solution Approach 1:
The damper assembly is merged with the existing ball screw mechanism and output shaft assembly. The damper shares common structural elements and mounting points with other actuator components, allowing fail-safe functionality to be added without proportionally increasing overall device complexity.
Solution Approach 2:
The damper assembly serves multiple functions: it provides fail-safe positioning when power is lost, controls the rate of return to neutral position, and works cooperatively with the ball screw mechanism during normal operation. This multi-functionality justifies the added complexity by delivering multiple reliability benefits from a single added assembly.
3Reliability
If ball nut disconnect system is implemented, then jam tolerance is improved, but weight increases
Solution Approach 1:
The ball nut disconnect system extracts the ability to disengage the ball nut from the output shaft as a separate, controllable function. This extraction allows the ball nut to be deliberately disconnected during jams or power loss to isolate the failure, while the disconnect mechanism itself is designed to be lightweight compared to the benefits of jam tolerance.
4Adaptability or versatility
If dual ball nut disconnect system is used, then component sharing is improved, but manufacturing complexity increases
Solution Approach 1:
The dual ball nut disconnect system uses a single disconnect mechanism that can disengage either ball nut (front or rear) depending on which motor assembly requires isolation. This universal disconnect capability allows one mechanism to serve multiple functions, enabling component sharing between the two motor assemblies while managing manufacturing complexity through standardization.
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 solution enhances the reliability and safety of electromechanical actuators by ensuring controlled movement and fail-safe positioning, enabling their use in primary flight control applications while reducing weight and shielding requirements.
Implementation Method 1
a damper assembly coupled to the output rod and including a damper and a damper drive train, wherein, in a normal motor operating state, the output rod is coupled to the nut to thereby control movement of the movable surface with the motor; and in a motor malfunction mode, the damper assembly is engaged to the output rod to provide a controlled rate of return of the movable surface to a fail-safe position
Data Source
AI summary
Vehicles commonly include control-surfaces and other components that are selectively moved during operation among a plurality of positions. Movement of aircraft control-surface components is crucial in flight, and an actuating assembly must consistently and dependably perform during normal operation and be prepared to survive situations outside normal operation and/or to compensate for circumstances causing loss of actuator control. Jam tolerant electromechanically operated actuation systems, of both the rotary and linear types, together with their methods of operation are described herein. Specifically, electrical jam-detection and control systems and associated locking and damping devices can be electrically and mechanically engaged and disengaged, are automatically reversible, and are testable.