Pneumatic Valve Position Control for Oscillation and Wear Adaptation
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Solution Overview
Problem
Control-related oscillations in valve positioners with pneumatic drives, particularly due to suboptimal settings of the integral component, lead to hysteresis and vibrations, which are difficult to detect and correct, affecting control quality.
Innovation Solution
A method that dynamically adjusts the dead zone and gain parameter of the integral component based on vibration detection and wear assessment, using thresholds for oscillation identification and parameter changes, without requiring a pressure sensor, to prevent oscillations caused by unfavorable parameter settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gain factor K i of the integral component is increased to reduce control deviation quickly, then the response speed improves, but the risk of oscillation increases
Solution Approach 1:
The patent implements dynamic adjustment of the dead band width based on the current operating state and detected oscillations. The dead band is continuously adapted during operation, being widened when oscillations are detected and narrowed when stable operation is confirmed, allowing the system to maintain optimal performance while preventing oscillations
Solution Approach 2:
The patent employs feedback mechanisms by monitoring the control deviation and detecting oscillations in real-time. Based on this feedback, the dead band parameters are automatically adjusted to prevent oscillations, creating a closed-loop control system that adapts to changing conditions
2Stability of the object's composition
If the dead band width is increased to suppress noise and prevent oscillation, then control stability improves, but control precision deteriorates
Solution Approach 1:
The dead band width is dynamically adjusted based on detected oscillations and operating conditions. During normal operation, a narrow dead band maintains control precision, while during oscillations, the dead band is automatically widened to suppress the oscillations, then narrowed again once stability is restored
Solution Approach 2:
The patent changes the dead band parameter dynamically during operation based on the detected system state. The dead band is increased when oscillations are detected and decreased when stable operation is confirmed, allowing the system to adapt to changing conditions and maintain both precision and stability as needed
3Speed
If friction compensation is increased to overcome static friction, then the valve response improves, but hysteresis and overshoot increase
Solution Approach 1:
The control parameters including friction compensation are dynamically adjusted based on the detected operating state and wear conditions. The system adapts the compensation level in real-time, increasing it when needed to overcome friction and decreasing it to minimize hysteresis and overshoot
Solution Approach 2:
The system automatically detects wear conditions and adjusts control parameters without external intervention. By monitoring oscillations and operating conditions, the system self-adjusts the friction compensation and dead band parameters to maintain optimal performance throughout the valve's operational life
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
Effectively minimizes control-related oscillations by adjusting control parameters in response to wear and friction changes, ensuring stable operation and maintaining control quality without excessive corrections.
Implementation Method 1
The direct cause of this is the compressibility of the air contained in the actuator
Implementation Method 2
especially in combination with seal types where the difference between static and sliding friction is particularly large
Data Source
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AI summary
A method is proposed for preventing control-induced oscillations in a valve with a pneumatic actuator and position control with an integrating component, comprising the following steps: First, check for valve element oscillations by counting zero crossings or extreme values of the control deviation. If oscillations are detected, it is verified whether they result from oscillations of the setpoint. If not, the dead zone is increased and/or the gain parameter is decreased. If no oscillations are detected, it is checked whether wear in the actuator has exceeded a predefined level. If so, the dead zone is reduced and/or the gain parameter is increased. This allows oscillations caused by the integral component of the control to be detected and eliminated. Further parameter changes are only made when a decrease in friction due to wear is expected.