Dual-Spool Piezo Servo Valve for Accurate Flow Control
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Solution Overview
Problem
Existing servo valves require precise tolerances for lands to block fluid flow and are prone to wear, and piezoelectric actuators with a single spool suffer from hysteresis and accuracy issues due to varying spool displacement based on voltage direction.
Innovation Solution
A servo valve design with two spools, each actuated by independent piezoelectric actuators and biasing elements, allowing precise control of fluid flow through multiple metering edges, eliminating the need for a separate pilot stage and reducing wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spool with piezoelectric actuator is used, then the device complexity is reduced, but hysteresis and accuracy issues occur due to varying spool displacement based on voltage direction
Solution Approach 1:
The single spool is divided into two separate spools (first spool and second spool), each with its own piezoelectric actuator. This segmentation eliminates the hysteresis issue by providing independent actuation for each spool, allowing precise control without the accuracy degradation that occurs in single-spool designs when voltage direction changes.
2Manufacturing precision
If multiple high-tolerance lands are used in the spool, then fluid flow control precision is improved, but the spool wears over time requiring replacement
Solution Approach 1:
The spool valve functionality is segmented across two spools, each with fewer lands (two lands per spool instead of four). This reduces the wear points on each individual spool while maintaining the overall fluid flow control precision through the coordinated operation of both spools.
Solution Approach 2:
The design changes the configuration parameters of the spool system by using two spools with two lands each, rather than one spool with four lands. This parameter change redistributes the wear across multiple components, improving the reliability and durability of the system while maintaining manufacturing precision for fluid flow control.
3Reliability
If a pilot stage is added to drive the spool valve, then the servo valve performance is improved, but extra weight and complexity are added to the system
Solution Approach 1:
The pilot stage, which adds weight and complexity to conventional systems, is completely extracted and removed from the design. The servo valve achieves its performance requirements through the direct piezoelectric actuation of the two spools, eliminating the need for the intermediate pilot stage mechanism.
Solution Approach 2:
The mechanical pilot stage system is replaced with a direct piezoelectric actuation system. The piezoelectric actuators provide the necessary force to move the spools directly, substituting the complex mechanical pilot stage with a more compact and lighter electrical-mechanical system that achieves the same or better performance.
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 dual spool design provides improved accuracy, reduces wear, and simplifies manufacturing, while achieving precise fluid control and reducing weight, thus enhancing the overall performance and reliability of the servo valve.
Implementation Method 1
a first piezoelectric actuator operatively connected to the first spool for translating the first spool in response to a voltage applied thereto
Implementation Method 2
The first and second biasing elements comprise piezoelectric discs. Compression or expansion of the first and second biasing elements creates a dimensional change in the piezoelectric discs that generates a voltage indicative of the amount of dimensional change.
Data Source
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AI summary
A servo valve (100) comprises a first spool (108a) extending along a first spool axis (110a), a second spool (108b) extending along a second spool axis (110b), a first piezoelectric actuator (112a), and a second piezoelectric actuator (112b). The first piezoelectric actuator (112a) is operatively connected to the first spool (108a) for translating the first spool (108a) in response to a voltage applied thereto. The second piezoelectric actuator (112b) is operatively connected to the second spool (108b) for translating the second spool (108b) in response to a voltage applied thereto.