Redundant Hydraulic Actuator Valving for Force Fight Mitigation
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Solution Overview
Problem
Force fights between redundant fluid actuators in aircraft systems, such as those used for control surface positioning, result in significant stresses and torques due to differences in actuator displacements, leading to inefficiency, wear, and potential damage, and existing solutions either oversize components or increase system complexity with sensors and control loops.
Innovation Solution
A dual-redundant hydraulic actuator system with primary and secondary fluid valves that allow for fluidic control, where the secondary valve permits flow between opposing chambers near null positions, mitigating force fights by ensuring equal fluid pressures and reducing mechanical interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If two redundant fluid actuators are used to actuate the same output, then reliability is improved, but force fight occurs causing increased stress and potential damage
Solution Approach 1:
A differential pressure transducer is introduced as an intermediary device to measure the pressure difference between two redundant actuators. This sensor enables the control system to detect force fight conditions and implement corrective actions, resolving the contradiction by allowing redundancy while monitoring and mitigating harmful stresses
2Strength
If actuating systems are overbuilt to withstand force fight loads, then strength is improved, but device complexity and weight increase
Solution Approach 1:
The differential pressure transducer provides real-time feedback on force fight conditions, enabling the control system to actively manage and mitigate stresses rather than relying on overbuilt components. This feedback mechanism allows the system to maintain adequate strength while avoiding unnecessary complexity and weight from oversized components
3Stress or pressure
If differential pressure transducers and closed feedback control loops are implemented, then force fight mitigation is improved, but device complexity increases
Solution Approach 1:
The differential pressure transducer serves as a specialized intermediary that directly measures the critical parameter (pressure difference) needed for force fight mitigation. By placing this sensor strategically in the fluid lines, the system achieves effective control with minimal additional complexity compared to more invasive sensing approaches
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 reduces force fights without complex sensors or control loops, improving system efficiency, power, and mechanical lifespan by minimizing stresses and torques, particularly at null positions.
Implementation Method 1
a first fluid chamber configured to receive fluid to urge movement of the first piston in a first direction
Implementation Method 2
a second fluid chamber configured receive fluid to urge movement of the first piston in a second direction opposite the first direction
Implementation Method 3
a third fluid chamber configured to receive fluid to urge movement of the second piston in a first direction
Implementation Method 4
a fourth fluid chamber configured to receive fluid to urge movement of the second piston in a second direction opposite the first direction
Data Source
AI summary
The subject matter of this specification can be embodied in, among other things, a method that includes controlling, by a first fluid valve, a first fluid flow to a first fluid actuator, actuating, by the first fluid actuator, an output, controlling, by a second fluid valve, a second fluid flow to a second fluid actuator, and actuating, by the second fluid actuator, the output.