Horizontal Stabilizer Trim Actuation With Hydraulic Locking
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Solution Overview
Problem
Aircraft Horizontal Stabilizer Trim Actuators (HSTAs) face challenges in preventing un-commanded or unintended movement of horizontal control surfaces, which can be undesirable and affect the reliability, cost, and weight of the system.
Innovation Solution
A hydraulic stabilizer trim actuator system that includes a hydraulic inlet, a shutoff apparatus, a directional and rate control apparatus, and a hydraulic motor, configured to switch between positions to control the flow of pressurized hydraulic fluid and prevent unintended movement by locking the hydraulic motor when not commanded to actuate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hydraulic stabilizer trim actuator system is designed to prevent un-commanded movement by implementing multiple control apparatuses and locking mechanisms, then reliability is improved, but device complexity increases
Solution Approach 1:
The hydraulic control system is divided into distinct functional segments: a hydraulic shutoff apparatus that controls overall hydraulic flow, a directional and rate control apparatus that manages fluid direction and flow rate, and a hydraulic motor that converts hydraulic energy to mechanical motion. This segmentation allows each component to be optimized for its specific function while working together to prevent un-commanded movement through distributed control points.
Solution Approach 2:
The hydraulic shutoff apparatus is configured to prevent hydraulic fluid from reaching the directional and rate control apparatus unless commanded to do so. This preliminary blocking action ensures that the system remains in a safe, locked state by default, and only allows hydraulic flow when intentionally activated, thereby preventing un-commanded movement before it can occur.
2Measurement precision
If the hydraulic actuator system uses multiple control apparatuses and positioning mechanisms to ensure precise control, then control precision is improved, but manufacturing cost increases
Solution Approach 1:
The directional and rate control apparatus performs multiple functions: it directs hydraulic fluid to the appropriate side of the hydraulic motor, controls the rate of fluid flow to regulate actuator speed, and can prevent fluid flow to lock the actuator in position. This multi-functionality reduces the need for separate components, thereby lowering manufacturing costs while maintaining precise control capability.
Solution Approach 2:
The hydraulic fluid acts as an intermediary medium that transmits control commands from the control apparatus to the hydraulic motor. By using fluid pressure and flow rate as the intermediary, the system achieves precise control of the control surface position and movement rate without requiring direct mechanical linkages or complex electronic actuators, thereby reducing manufacturing complexity.
3Reliability
If the actuator system implements continuous monitoring and control mechanisms to prevent unintended movement, then safety is improved, but weight of the system increases
Solution Approach 1:
The hydraulic shutoff apparatus and directional control apparatus are configured to automatically maintain the hydraulic motor in a locked state by default, without requiring continuous active control signals. The system self-regulates by preventing hydraulic flow unless commanded, and the hydraulic motor inherently maintains position when hydraulic pressure is applied to both sides equally. This self-service mechanism provides safety without requiring additional active monitoring components.
Solution Approach 2:
The system uses hydraulic pressure and fluid flow as the primary control mechanism. By leveraging hydraulic principles, the system achieves precise control and locking functionality through fluid pressure balancing rather than requiring mechanical locks or electronic sensors. This hydraulic approach provides inherent safety through physics-based control while minimizing additional weighting components.
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 effectively minimizes un-commanded movement of horizontal control surfaces, improving reliability, reducing costs, and minimizing weight by ensuring the actuator is only active when commanded, thus enhancing aircraft control and safety.
Implementation Method 1
a hydraulic shutoff apparatus fluidically connected to the first hydraulic path and the second hydraulic path and configured to be switched between a plurality of hydraulic positions wherein at least one of the hydraulic positions allows for the pressurized hydraulic fluid to flow from the first hydraulic path through the hydraulic shutoff apparatus to the second hydraulic path
Implementation Method 2
a directional and rate control apparatus, a third hydraulic path fluidically connected to the directional and rate control apparatus
Implementation Method 3
a hydraulic motor fluidically connected to the directional and rate control apparatus via the third hydraulic path. The hydraulic motor may be configured to turn an output shaft to actuate a control surface of a vehicle responsive to receiving the pressurized hydraulic fluid from the directional and rate control apparatus and configured to be locked responsive to not receiving the pressurized hydraulic fluid
Data Source
AI summary
A vehicle control surface, such as an aircraft horizontal stabilizer, is hydraulically controlled using solenoid operated valves (SOVs) controlling directional control valves and/or rate control valves with small numbers of ports, e.g. a four port three position directional control value and/or a four port two position rate control valve.