Flight Control Rod Coupling for Backlash-Free Position Sensing
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Solution Overview
Problem
Existing flight control surface actuation systems face challenges in accurately measuring the angular displacement of connecting rods due to backlash and free play, which introduce measurement errors, particularly in aerospace applications where precise control is crucial.
Innovation Solution
A flight control surface actuation system with a connecting rod and position sensor arrangement that includes a connection mechanism with a conical friction surface to minimize backlash, using a rotary actuator and a position sensor mounted externally to the actuator, allowing for accurate measurement of angular displacement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a position sensor is mounted on the actuator output shaft to measure angular displacement, then the position of the flight control surface can be determined, but measurement errors occur due to backlash and free play in the connection mechanism
Solution Approach 1:
The patent introduces an intermediary element (the engagement part with conical friction surfaces) between the actuator output shaft and the connecting rod. This intermediary eliminates backlash and free play by maintaining constant contact through friction, thereby ensuring accurate position sensor readings without the measurement errors that would otherwise occur in direct mechanical connections
Solution Approach 2:
The patent replaces traditional mechanical connection methods (which inherently have backlash and play) with a friction-based engagement system. The conical friction surfaces create a non-mechanical coupling that eliminates clearance issues, allowing the position sensor to measure angular displacement accurately without the interference of mechanical clearance
2Measurement precision
If the position sensor is integrated into the connection mechanism, then measurement accuracy improves, but the device complexity increases
Solution Approach 1:
The engagement part serves multiple functions simultaneously: it transmits rotational motion from the actuator to the connecting rod, eliminates backlash through conical friction surfaces, and provides a mounting structure for the position sensor. This multi-functionality reduces overall device complexity while maintaining high measurement accuracy
3Measurement precision
If axial load is applied to the engagement part to minimize backlash, then measurement accuracy improves, but the force required to operate the system increases
Solution Approach 1:
The patent uses conical (curved) friction surfaces instead of flat surfaces. The conical geometry allows the engagement part to self-center and distribute axial loads more evenly, minimizing the peak forces required to maintain contact and eliminate backlash while still achieving high measurement accuracy
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 provides precise angular displacement measurements with reduced errors, enabling improved control of flight control surfaces by integrating a load sensor directly on the connecting rod, reducing actuator size and enhancing accessibility and accuracy.
Implementation Method 1
a first conical portion which tapers in a first axial direction, wherein the first conical portion may form a first friction surface engaged with a corresponding first connecting rod friction surface
Data Source
AI summary
A flight control surface actuation system includes a rotary actuator having an output part configured to rotate about an axis (R-R), a connecting rod for connecting a flight control surface to the rotary actuator, and a connection mechanism connecting a first end of the connecting rod to the output part such that rotation of the output part about the axis causes at least part of the connection rod to rotate about the axis. The connection mechanism comprises a connection structure fixed to the output part and an engagement part mounted for rotation about a longitudinal axis. The engagement part extends through the connecting rod and is fixed to it. A position sensor is arranged to measure the angular displacement of the first end of the connecting rod about the axis.