Control Valve Friction Detection Through Hysteresis Comparison
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Solution Overview
Problem
Existing control valve positioners require manual and time-consuming processes to determine frictional characteristics and control step sizes, leading to potential inaccuracies and increased costs due to the variability of valve and actuator assemblies.
Innovation Solution
An automated method that measures average hysteresis and compares it to the operating range to determine frictional characteristics, allowing for the automatic selection of a control step size for the valve positioner, eliminating the need for user input and reducing errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual tuning processes are used to determine frictional characteristics and control step sizes, then user control and flexibility are maintained, but time consumption and potential inaccuracies increase
Solution Approach 1:
The valve positioner automatically determines its own frictional characteristics by performing hysteresis measurements and calculations without requiring manual intervention. The system self-configures by measuring pressures at different valve positions, calculating hysteresis values, and automatically selecting optimal control step sizes based on the determined friction characteristics.
Solution Approach 2:
The system performs preliminary hysteresis measurements and friction characterization during the tuning phase before actual operation. By pre-determining the frictional characteristics and selecting appropriate control step sizes in advance, the system eliminates the need for repeated manual adjustments during operation.
2Productivity
If automated determination methods are implemented, then tuning speed and consistency are improved, but system complexity increases
Solution Approach 1:
The valve positioner integrates multiple functions into a single device: it acts as both the actuator controller and the friction measurement instrument. The same controller that manages valve positioning also performs hysteresis measurements, calculates friction characteristics, and determines optimal control parameters, eliminating the need for separate tuning equipment.
Solution Approach 2:
The system uses pressure measurements as an intermediary to indirectly determine frictional characteristics. By measuring pressures at different valve positions during stroking operations, the system can calculate hysteresis values and friction properties without requiring direct measurement of friction forces.
3Reliability
If manual tuning processes are used, then equipment costs are reduced, but tuning accuracy and reliability decrease due to variability
Solution Approach 1:
The system uses feedback from pressure measurements at different valve positions to continuously refine the determination of frictional characteristics. By measuring pressures during forward and reverse stroking operations and comparing the results, the system accurately calculates hysteresis values and selects optimal control step sizes based on actual valve behavior.
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
This approach enables precise and efficient tuning of control valves by automatically determining frictional characteristics and selecting appropriate control step sizes, improving accuracy and stability while reducing the time and expense associated with manual tuning processes.
Implementation Method 1
determining an average hysteresis of the valve assembly based on the pressure measurements
Data Source
AI summary
Methods, apparatus, systems and articles of manufacture are disclosed for automatically determining friction of a control valve. An example apparatus includes a hysteresis measurement controller to determine an average control hysteresis value for a valve over a first range of travel of the valve, a comparator to compare the average control hysteresis value to a second value corresponding to a second range of travel of the valve encompassing the first range of travel of the valve, and a step size selector to select one of multiple control step sizes for the valve based on the comparison.