Control Valve Friction Measurement for Automatic Step Size Tuning
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Solution Overview
Problem
Existing methods for tuning control valves are time-consuming, expensive, and prone to error, as they require manual input of friction types and characteristics to determine appropriate control step sizes.
Innovation Solution
An automated method that measures the average hysteresis of a valve and actuator assembly, compares it to the operating range, and selects an appropriate control step size based on the comparison, eliminating the need for user input.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual tuning methods are used to determine control step sizes, then friction characteristics can be input, but the process is time-consuming and expensive
Solution Approach 1:
The valve positioner automatically measures its own friction characteristics by executing a tuning routine that strokes the valve and measures actuator pressure at different positions. This self-measurement eliminates the need for manual friction input and significantly reduces tuning time while maintaining accuracy.
Solution Approach 2:
The system performs preliminary friction measurement during the tuning routine before final control parameters are established. By measuring friction characteristics in advance through automated pressure measurements at multiple valve positions, the system prepares accurate data for subsequent control step size determination without delaying the overall tuning process.
2Ease of operation
If manual input of friction types is required, then control step size can be determined, but user error increases
Solution Approach 1:
The system replaces manual mechanical/friction classification input with automated electronic pressure measurement and computation. The valve positioner electronically measures actuator pressure at different valve positions and automatically computes friction characteristics, eliminating user subjectivity and input errors while improving both ease of operation and reliability.
Solution Approach 2:
The system uses feedback from actual actuator pressure measurements during valve stroking to automatically determine friction characteristics. By continuously monitoring pressure feedback at multiple positions and using this data to compute friction, the system eliminates the need for manual friction type selection while ensuring accurate, objective results.
3Productivity
If automated friction measurement is implemented, then tuning time is reduced, but measurement complexity increases
Solution Approach 1:
The valve positioner performs multiple functions using the same basic hardware: it controls valve positioning, measures actuator pressure, executes tuning routines, and computes friction characteristics. By making the positioner multi-functional, the system achieves automated friction measurement without adding separate dedicated measurement devices, thus reducing overall system complexity while maintaining high productivity.
Solution Approach 2:
The system merges the friction measurement function with the existing valve control and pressure measurement capabilities. By combining these functions into a single integrated tuning routine that uses the same actuators and sensors already present in the valve positioner, the system achieves automated measurement without increasing device 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
This approach enables automatic tuning of valve positioners, reducing the time and cost associated with manual tuning processes while minimizing errors and improving the accuracy and stability of control loops.
Implementation Method 1
determining an average control hysteresis value for a valve over a first range of travel of the valve
Data Source
AI summary
Methods, apparatus, systems and articles of manufacture are disclosed for automatically determining friction of a control valve. An example method includes measuring first and second pressures corresponding to respective first and second positions of a valve while stroking the valve in a first direction, measuring third and fourth pressures corresponding, respectively, to the second and first positions while stroking the valve in a second direction opposite the first direction, determining a first pressure difference between the second and third pressures, determining a second pressure difference between the first and fourth pressures, determining an average pressure based on the first and second pressure differences, comparing the average pressure to a third pressure difference corresponding to a range of travel of an actuator including the first and second positions, and determining a control step size for the valve based on the comparison.