Harmonic Drive Selective Disconnect for Jammed Actuators
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Solution Overview
Problem
Aircraft flight control systems face challenges when the primary electro-mechanical actuators become stuck or jammed, making it difficult for backup systems to control flight control surfaces effectively, leading to potential loss of control during failures.
Innovation Solution
A harmonic drive assembly with a selective disconnect mechanism that allows the motor drive shaft and wave generator to be retracted, decoupling from the harmonic drive and flex gear, creating a clearance between the ring gear and flex gear teeth, enabling efficient disengagement and reengagement to prevent energy transfer and overcome jamming issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the primary electro-mechanical actuator is designed with a fixed connected harmonic drive, then the system structure is simple and reliable, but the backup system cannot effectively control flight control surfaces when the primary system jams
Solution Approach 1:
The patent applies the dynamics principle by making the harmonic drive connection adjustable rather than fixed. The actuator can dynamically switch between connected and disconnected states through the retracting mechanism, allowing the system to adapt its configuration based on operational needs - connected during normal operation and disconnected when backup control is required.
Solution Approach 2:
The patent segments the actuator system into separable components - the motor drive shaft assembly and the harmonic drive assembly can be independently positioned. The retracting mechanism enables axial separation between these segments, allowing the motor drive shaft to be pulled out from the harmonic drive, effectively dividing the system into controllable parts.
2Productivity
If the motor drive shaft remains continuously connected to the harmonic drive, then energy transfer is efficient, but the backup system experiences jamming and cannot overcome the stuck primary system
Solution Approach 1:
The system dynamically adjusts the connection state between motor drive shaft and harmonic drive. During normal operation, the connected state provides efficient energy transfer. When backup control is needed, the retracting mechanism disengages the connection, allowing the backup system to operate independently without being constrained by the jammed primary system.
Solution Approach 2:
The patent extracts the motor drive shaft from the harmonic drive connection through axial retraction. This separation removes the interfering influence of the primary system on the backup system, allowing the backup actuator to control flight surfaces without having to overcome the resistance of a jammed primary actuator.
3Reliability
If a disconnect mechanism is added to allow backup system operation, then backup system reliability improves, but the device complexity and potential for energy loss increase
Solution Approach 1:
The retracting mechanism is nested within the existing actuator structure, with the motor drive shaft assembly containing the retracting mechanism that can pull the wave generator and flex gear assembly axially. This nested arrangement integrates the disconnect function into the existing structure without requiring completely separate systems.
Solution Approach 2:
The retracting mechanism is designed to be actuated by the system itself - through motor control or mechanical actuation - rather than requiring external complex disconnection systems. The mechanism uses the existing components (motor drive shaft, wave generator, flex gear) to achieve self-disengagement and self-reengagement capabilities.
Data Source
AI summary
A harmonic drive assembly with selective disconnect includes a motor with a motor drive shaft, a harmonic drive operatively coupled to the motor drive shaft, and a wave generator operatively coupled to the motor drive shaft and a flex gear of the harmonic drive. Also included is a ring gear of the harmonic drive operatively coupled to the flex gear with a plurality of ring gear teeth configured to mesh with a plurality of flex gear teeth. Further included is an output shaft operatively coupled to the harmonic drive. Yet further included is a retracting mechanism configured to selectively retract the motor drive shaft and the wave generator to decouple the motor drive shaft and the wave generator from the harmonic drive, wherein a clearance between the ring gear teeth and the flex gear teeth is established upon retraction of the motor drive shaft and the wave generator.