Failsafe Valve for Geared Rotary Actuators With Adjustable Null Position
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Solution Overview
Problem
Existing rotary hydraulic actuators for aircraft control surfaces have a fixed null position and limited angular motion, making them unsuitable for applications requiring continuous revolutions and adjustable failsafe positioning, especially in thin-wing aircraft designs.
Innovation Solution
A failsafe valve mechanism is integrated with a hydraulic rotary motor, allowing the control surface to return to a neutral position in case of failure without a fixed port, and enabling continuous rotation by connecting one of the motor's hydraulic control lines to a case return line, with a metering spool adjusting based on the control surface's position to achieve adjustable failsafe positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed HITW port is provided in the hydraulic cylinder or stator, then the control surface can be centered in failsafe mode, but the null position cannot be adjusted and the range of rotary motion is limited to less than 360 degrees
Solution Approach 1:
The patent replaces the fixed HITW port with a dynamic valve mechanism that can adjust its position and timing. The valve is actuated by a sensor detecting the control surface position, allowing the system to adaptively determine and maintain the null position while enabling continuous rotation beyond the limitations of a fixed port configuration.
Solution Approach 2:
The patent introduces an intermediary valve mechanism between the hydraulic motor and the control surface. This valve acts as a mediator that can selectively connect or disconnect hydraulic lines based on the detected position of the control surface, thereby achieving adjustable failsafe positioning without requiring a fixed port in the motor or stator.
2Reliability
If a HITW port is provided through the stator, then return pressure can be provided to rotate the rotor toward null position in failsafe mode, but the location of the port determines a fixed null position that cannot be changed
Solution Approach 1:
The patent replaces the mechanical fixed port structure with a controllable valve mechanism. Instead of relying on the physical location of a port to determine null position, the system uses a sensor-actuated valve that can dynamically position the hydraulic connection, thereby maintaining failsafe functionality while eliminating the constraint of fixed null position.
Solution Approach 2:
The patent changes the parameter of port location from fixed to variable. By using a sensor to detect control surface position and actuating a valve accordingly, the system dynamically adjusts the hydraulic connection point, allowing the null position to be determined by the sensor detection rather than by a fixed physical port location.
3Reliability
If the range of rotary motion is limited to less than 360 degrees in a rotary hydraulic actuator, then the HITW concept can be implemented, but the actuator is unsuitable for thin-wing aircraft requiring continuous revolutions
Solution Approach 1:
The patent makes the valve timing and position dynamic rather than fixed. The valve is actuated based on real-time detection of the control surface position, allowing the system to provide failsafe functionality at any point in the rotation cycle. This enables continuous rotation capability while maintaining the ability to center the control surface in failsafe mode, regardless of the rotor's angular position.
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
Enables continuous rotation and adjustable failsafe positioning of aircraft control surfaces, enhancing the suitability for thin-wing applications by maintaining aerodynamic neutrality and reducing drag.
Implementation Method 1
pressurized fluid is delivered to the motor by way of the first control line P1 and fluid is permitted to leave the motor by way of the second control line P2
Implementation Method 2
Hydraulic pressure from the return line enables the hydraulic manifold to hydraulically fill the lower pressure side of the piston to force the piston of the linear hydraulic actuator toward a central null position
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A failsafe vale provides"Hole-In-The-Wall"failsafe functionality for thin- wing aircraft control surface actuation systems having a geared rotary actuator powered by a hydraulic rotary motor. The failsafe valve is associated with the hydraulic rotary motor and mechanically connected to the control surface, and enables the flight control surface to return to an aerodynamically neutral failsafe position if electrical control and/or hydraulic pressure is lost. When the failsafe valve receives a normal command pressure from the hydraulic system, the valve is inactive and the actuation system operates normally. However, if there is a loss of electrical command capacity to control hydraulic valves and/or a loss of hydraulic pressure, the failsafe valve is activated and connects one of the motor hydraulic control lines to the case return line for the motor if the control surface is away from its failsafe position. Consequently, the control surface will be hydraulically powered or aerodynamically ratcheted to its failsafe position in the failure event.