Preloaded Torque Shaft Assembly for Precise Flight Surface Actuation
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Solution Overview
Problem
Aircraft control surface actuation assemblies face challenges with limited envelope space for housing torque shafts, leading to axial, torsional, and lateral deflections under load, which affect position accuracy and control.
Innovation Solution
A torque shaft assembly comprising concentric tubes with axial and torsional preloads, and a composite torque shaft assembly with fiber wraps, to minimize deflections and enhance stability, is introduced. The assembly includes a gearbox and eccentric cam mechanism to efficiently actuate flight surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional torque shaft is used in a control surface actuation assembly, then the assembly can be housed within limited envelope space, but the torque shaft experiences axial, torsional, and lateral deflections under load that reduce position accuracy
Solution Approach 1:
The patent employs a telescoping torque shaft assembly where an inner torque shaft is nested within an outer torque shaft. The inner shaft can extend and retract relative to the outer shaft, allowing the assembly to accommodate variable length requirements while maintaining structural integrity. This nested configuration reduces lateral deflection by distributing mechanical loads across multiple concentric shafts rather than relying on a single rigid shaft, thereby improving position accuracy within limited envelope space.
Solution Approach 2:
The torque shaft is divided into multiple segmented sections (inner and outer shafts) that can move independently relative to each other. This segmentation allows each section to be optimized for specific functions: the inner shaft provides precise positional control while the outer shaft offers structural support and load bearing. The segmented design reduces overall deflection by breaking the continuous shaft into manageable sections that can flex and compensate for individual deformations.
2Volume of stationary object
If the envelope space for housing the actuation assembly is limited, then the aircraft wing structure is more efficient, but the torque shaft experiences increased deflection under load
Solution Approach 1:
The telescoping configuration allows the torque shaft assembly to collapse into a compact form when not in use, minimizing the envelope volume required within the aircraft wing. When actuation is needed, the inner shaft extends to provide the necessary operational length while maintaining structural rigidity. This nesting principle enables the system to achieve both compact storage and adequate operational length, preventing excessive deflection under load.
Solution Approach 2:
The torque shaft assembly transitions from a static, fixed-length shaft to a dynamic, variable-length configuration. The telescoping mechanism allows the shaft length to adjust based on operational requirements, optimizing the balance between compactness and structural rigidity. This dynamic adaptation enables the system to maintain reliability and control accuracy while accommodating limited envelope space constraints.
3Measurement precision
If a longer torque shaft is used to reduce deflection, then position accuracy improves, but the assembly requires more envelope space within the wing
Solution Approach 1:
The telescoping torque shaft assembly provides a long operational length when extended to minimize deflection and improve position accuracy, yet collapses to a compact nested configuration when retracted to reduce envelope volume. This dual-state capability allows the system to achieve the benefits of a long shaft during operation while requiring minimal space during storage or non-operational phases, effectively resolving the contradiction between length and volume.
Data Source
AI summary
Presented are a method and apparatus for an aircraft flight surface actuation system including a motor having an output shaft. A gearbox is coupled with the output shaft, whereby a first driving force output via the motor is converted to a second driving force. A torque shaft assembly is driveably coupled with the gearbox. The torque shaft assembly includes a first tube, a second tube located at least partially through the first tube and located coaxial therewith, wherein the first tube comprises an axial preload operable to mitigate lateral deflection, and wherein the first tube comprises a torsional preload operable to mitigate torsional deflection. In addition, the aircraft flight surface actuation system includes an eccentric cam mechanism driveably coupled with the torque shaft assembly, and a flight surface coupled with the eccentric cam mechanism.