Rotating Swashplate Segmentation for Tiltrotor Pitch Control
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Solution Overview
Problem
Existing rotor blade pitch control systems for rotary-wing aircraft face challenges in efficiently managing pitch angle adjustments, particularly in high collective configurations where pitch-flap coupling is significant, leading to reduced control precision and increased mechanical stress.
Innovation Solution
A blade-pitch control system utilizing a rotating swashplate assembly with a constant-velocity joint and gimbal mechanism, allowing for rotational indexing and reduced pitch-flap coupling, enables precise collective and cyclic pitch control through a combination of translational and tilting motions, minimizing mechanical stress and improving kinematic efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional swashplate assembly is used for pitch control, then collective and cyclic pitch control is achieved, but pitch-flap coupling increases in high collective configurations leading to reduced control precision
Solution Approach 1:
The swashplate assembly is divided into two separate swashplates: a first swashplate for collective pitch control and a second swashplate for cyclic pitch control. This segmentation allows independent control of collective and cyclic pitch, eliminating the pitch-flap coupling that occurs in conventional single-swashplate designs, particularly in high collective configurations.
Solution Approach 2:
A constant-velocity joint is introduced as an intermediary mechanism between the two swashplates and the rotor blades. This joint maintains a constant velocity ratio while allowing relative motion between the swashplates, thereby decoupling the pitch control functions and reducing mechanical stress transmission that causes pitch-flap coupling.
2Power
If pitch angle adjustments are made in high collective configurations, then thrust control is achieved, but mechanical stress on the swashplate assembly increases
Solution Approach 1:
By separating the swashplate assembly into two independent swashplates with separate control mechanisms, the mechanical load and stress are distributed and reduced on each individual swashplate. This segmentation allows the system to handle high collective pitch angles without excessive mechanical stress concentrating on a single swashplate structure.
Solution Approach 2:
The constant-velocity joint serves as a mechanical intermediary that reduces stress transmission between the swashplates and the rotor blades. It maintains the necessary power transmission for thrust control while filtering out harmful stress variations and mechanical coupling that would otherwise increase with high collective configurations.
3Device complexity
If a single swashplate assembly is used, then structure is simplified, but control precision is reduced due to pitch-flap coupling
Solution Approach 1:
The single swashplate assembly is segmented into two separate swashplates with distinct functions. While this increases the number of components, it enables independent control of collective and cyclic pitch, thereby improving control precision. The segmentation allows each swashplate to be optimized for its specific control function without the compromising pitch-flap coupling present in single-swashplate designs.
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 achieves reduced pitch-flap coupling in high collective configurations, enhanced control precision, and improved packaging by minimizing mechanical stress and optimizing kinematic efficiency, particularly beneficial for tiltrotor aircraft in both helicopter and airplane modes.
Implementation Method 1
a constant-velocity joint assembly, which allows yoke 23 to gimbal relative to mast 17 while mast 17 drives yoke 23 in rotation
Implementation Method 2
A blade-pitch control system is provided for a rotor having multiple blades that are each adjustable for pitch angle. Each blade is connected to a rotating swashplate of a swashplate assembly, and the rotating swashplate is configured for rotational indexing relative to the mast during rotation with the mast for collective pitch control of the blades
Data Source
AI summary
A blade-pitch control system has a swashplate configured for continuous rotation with an associated rotor and mast, and at least one link connects the swashplate to each blade of the rotor. The swashplate provides for collective control of the pitch angle of the blades through selective rotation of the swashplate about a swashplate axis while the swashplate is rotating with the rotor and mast. The system can be configured to provide for cyclic control of the pitch angle of the blades through planar translation of the swashplate or through tilting of the swashplate about axes generally perpendicular to the swashplate axis.