Electro-Hydraulic Servovalve Digital Control Against EMI and Temperature Drift
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Solution Overview
Problem
Conventional hydraulic servo control systems are susceptible to temperature changes and require multiple power sources, leading to reduced accuracy and power efficiency, especially in harsh environments like aircraft applications.
Innovation Solution
The implementation of a digital control system for electro-hydraulic servo valves that operates in the digital domain, using position feedback systems resistant to temperature changes and electromagnetic interference, and employing differential analog control signals to improve immunity to noise and power efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional analog electronic devices are used to measure and control hydraulic servo systems, then the system can operate with simple circuitry, but the system becomes susceptible to temperature changes and electromagnetic interference, reducing accuracy and reliability
Solution Approach 1:
The patent replaces conventional analog electronic measurement and control devices with a digital system. A digital controller receives feedback signals from position sensors (LVDTs), processes them digitally, and generates digital control signals that are converted to analog signals for the electro-hydraulic servo valve. This digital substitution improves immunity to temperature changes and electromagnetic interference, enhancing system reliability in harsh environments.
Solution Approach 2:
The patent changes the signal domain from analog to digital for processing. Position feedback signals and control signals are processed in the digital domain using a digital controller, which is less susceptible to environmental factors. The system converts digital control signals to analog signals only at the interface with the electro-hydraulic servo valve, maintaining digital processing benefits while ensuring compatibility with analog actuation requirements.
2Reliability
If multiple power sources are used in hydraulic servo control systems, then the system can maintain operation under various conditions, but the power efficiency and system complexity increase
Solution Approach 1:
The digital controller serves multiple functions within a single integrated unit: it processes position feedback signals from LVDTs, implements control algorithms, generates control signals for the electro-hydraulic servo valve, and interfaces between digital and analog domains. This multi-functionality consolidates what would traditionally require multiple separate devices and power sources into a single power-efficient controller.
3Device complexity
If analog control signals are used throughout the system, then the system can be simpler in signal processing, but the system becomes more susceptible to noise and electromagnetic interference
Solution Approach 1:
The patent substitutes analog signal processing with digital signal processing in the control system. The digital controller processes position feedback signals and generates control commands in the digital domain, which is inherently more immune to electromagnetic interference and noise. A converter circuit interfaces between the digital controller and the analog electro-hydraulic servo valve, maintaining signal integrity while enabling digital processing benefits.
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AI summary
The subject matter of this specification can be embodied in, among other things, a controller apparatus that includes a digital controller configured to provide a digital position signal based on a setpoint and a differential analog feedback signal, and a converter circuit configured to provide a differential analog electrohydraulic servo valve position control signal based on the digital position signal, and provide the differential analog feedback signal based on the differential analog electrohydraulic servo valve position control signal.