Nose-Wheel Steering Split Control for Faster Hydraulic Response
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Solution Overview
Problem
Conventional aircraft nose-wheel steering systems suffer from pressure drops and decreased frequency response due to large fluid volumes between hydraulic components, affecting controllability and response time.
Innovation Solution
A nose-wheel steering system with a mode selection valve positioned locally with the hydraulic actuator, reducing fluid volume and incorporating a servo valve separate from the main hydraulic line, enhancing frequency response and controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hydraulic components are positioned remotely with large fluid volumes between them, then system simplicity is maintained, but frequency response deteriorates and pressure drops increase
Solution Approach 1:
The hydraulic system is segmented into two independent circuits: a main hydraulic line for power transmission and a separate servo line for control. The servo valve is positioned locally with the actuator, creating a short local circuit for high-frequency response, while the main line handles bulk fluid transmission. This segmentation allows each circuit to be optimized for its specific function without compromising the other.
Solution Approach 2:
The servo valve acts as an intermediary control element positioned between the hydraulic pump and the actuator. It provides precise flow control for the servo line while allowing the main hydraulic line to maintain its simpler architecture. The intermediary servo line with local positioning enables high-frequency response without requiring the entire system to be reconfigured.
2Loss of energy
If hydraulic fluid volume between components is reduced, then pressure drops decrease and frequency response improves, but system compactness requirements increase
Solution Approach 1:
The hydraulic system is divided into a local servo circuit with minimal fluid volume for high-frequency control signals, and a separate main hydraulic circuit for power transmission. This segmentation confines the low-volume requirement to only the critical control path, allowing the main system to maintain adequate fluid volumes for power transmission without compromising pressure response or frequency characteristics.
Solution Approach 2:
The servo valve and actuator are positioned locally together, creating a compact control zone with minimal fluid volume between them. This local concentration of control components reduces pressure drops and improves frequency response in the critical control path, while the rest of the system can maintain standard component spacing and fluid volumes.
3Ease of operation
If mode selection valve is positioned locally with hydraulic actuator, then frequency response and controllability improve, but system complexity increases
Solution Approach 1:
The control system is segmented into a local servo circuit with the mode selection valve positioned with the actuator for precise control, and a separate main hydraulic line for power transmission. This segmentation isolates the complexity of the local control circuit from the main system, allowing the valve and actuator to be optimized for controllability without burdening the entire system with reconfiguration requirements.
Solution Approach 2:
The mode selection valve serves as an intermediary control element that locally manages fluid flow direction to the actuator. By positioning it with the actuator, it provides direct and responsive control over the servo line, enabling precise mode switching and controllability while the main hydraulic line continues to handle bulk fluid transmission independently.
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 improves frequency response, controllability, and reduces pressure drops, resulting in enhanced steering performance and reduced actuator size.
Implementation Method 1
a hydraulic actuator operatively coupled to the collar gear and configured to drive a rotation of the collar gear
Implementation Method 2
a steering rate servo valve configured to control a flow rate of a hydraulic fluid from a hydraulic fluid source through the hydraulic actuator
Implementation Method 3
a mode selection valve moveable between a steering off position, a steer left position, and a steer right position. In the steer right position, the mode selection valve directs the hydraulic fluid through the hydraulic actuator in a first direction. In the steer left position, the mode selection valve directs the hydraulic fluid through the hydraulic actuator in a second direction opposite the first direction
Implementation Method 4
a collar gear operatively coupled to a strut piston and configured to rotate the strut piston about a piston axis of rotation
Data Source
AI summary
A wheel steering system includes a hydraulic steering control system including a steering rate servo valve disposed in close proximity to a hydraulic pump and a mode selection valve disposed in close proximity to a hydraulic actuator. The steering rate servo valve is in a separate flow path from the primary flow path between the hydraulic pump and the mode selection valve. The mode selection valve is moveable between a steering off/free caster shimmy damper position, a steer left position, and a steer right position. The mode selection valve controls a hydraulic actuator. The hydraulic actuator can control rotation of a collar gear to thereby control steering of a wheel assembly.