Nested Hydraulic Actuator With Force-Balance Redundancy
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Solution Overview
Problem
Existing hydraulic actuators face challenges in providing redundancy and ballistic tolerance without increasing weight, and configurations with multiple pistons suffer from damage propagation and reduced stiffness.
Innovation Solution
A dual-system hydraulic actuator with separate primary and secondary cylinders and pistons, each controlled by independent fluid chambers, and a force-balance chamber to balance extension and retraction forces, ensuring redundancy and protection against damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple pistons are used to provide redundancy and increased force, then reliability and force output are improved, but device complexity and vulnerability to damage propagation increase
Solution Approach 1:
The actuator is divided into two independent hydraulic systems: a primary system with a primary piston and a secondary system with a secondary piston. Each system has its own fluid chambers (first chamber for primary extension, second chamber for primary retraction, third chamber for secondary extension, fourth chamber for secondary retraction) that can operate independently. This segmentation allows redundancy while containing damage within one system, resolving the contradiction between reliability and complexity.
2Reliability
If multiple pistons are used to provide redundancy, then reliability is improved, but weight increases
Solution Approach 1:
The secondary piston and its associated components are nested within the primary cylinder assembly. The secondary piston moves within the primary cylinder, and the force-balance chamber is integrated into the existing structure rather than adding separate external components. This nesting arrangement provides redundancy while minimizing weight increase compared to using two completely separate actuators.
3Stability of the object's composition
If extension and retraction fluid forces are made equal, then force balance is improved, but adaptability to different operational requirements is reduced
Solution Approach 1:
The force-balance chamber dynamically adjusts the fluid force on the secondary piston based on operational requirements. During normal operation, the force-balance chamber receives fluid from the third chamber to provide balancing force. When additional force is needed, the system can modify fluid flow to the force-balance chamber, allowing the force balance to adapt rather than being fixed, thus resolving the contradiction between stability and adaptability.
4Stability of the object's composition
If a force-balance chamber is added to compensate for force differences, then force balance is improved, but device complexity increases
Solution Approach 1:
The force-balance chamber serves multiple functions: it balances the extension and retraction forces on the secondary piston, provides additional force when needed, and can receive fluid from either the third or fourth chamber depending on operational requirements. This multi-functionality reduces the need for separate balancing mechanisms, resolving the contradiction between force balance and complexity.
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 actuator provides redundancy and ballistic tolerance, maintaining functionality even if one system fails, while minimizing weight and reducing vulnerability to damage and vibration.
Implementation Method 1
When pressurized fluid is provided to one chamber, the piston moves. A double acting actuator has a piston that can move in both directions. Any difference in fluid pressure between the two sides of the piston moves the piston inside the cylinder.
Implementation Method 2
an extension fluid force applied by fluid in the third chamber to extend the secondary piston is different from a retraction fluid force applied by fluid in the fourth chamber to retract the secondary piston
Implementation Method 3
a force-balance chamber configured to receive fluid from the third chamber or the fourth chamber to apply a balancing force on the secondary piston to either oppose fluid force acting on the secondary piston or add to the fluid force acting on the secondary piston
Data Source
AI summary
An actuator includes a primary piston and a secondary piston axially movable together in a cylinder assembly; a plurality of chambers comprising: a first chamber, a second chamber, a third chamber, and a fourth chamber, wherein when fluid flows into the first chamber the primary piston extends and when fluid flows into the second chamber the primary piston retracts, wherein an extension fluid force applied by fluid in the third chamber to extend the secondary piston is different from a retraction fluid force applied by fluid in the fourth chamber to retract the secondary piston; and a force-balance chamber configured to receive fluid from the third chamber or the fourth chamber to apply a balancing force on the secondary piston to either oppose fluid force acting on the secondary piston or add to the fluid force acting on the secondary piston, thereby compensating for a difference between the extension fluid force and the retraction fluid force.