Positioner Operation Time Correction for Valve Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The operation time of the setting/operating device in a regulating valve changes due to supply air pressure and sliding resistance, leading to incorrect determination of control parameters and issues like stabilization time, overshooting, and hunting in the dynamic characteristics of the positioner, especially when supply air pressure is high or hysteresis is large.
Innovation Solution
A positioner with a control parameter selecting and setting function that includes measurement and correction of operation time and sliding resistance, using stored corrected values to determine the correct size of the setting/operating device and select appropriate control parameters, accounting for supply air pressure and friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If the operation time of the setting/operating device is used to determine control parameters, then the control parameters can be set automatically, but the determination becomes incorrect when supply air pressure is high or sliding resistance is large
Solution Approach 1:
The patent applies parameter changes by introducing correction values that adjust the measured operation time based on supply air pressure and sliding resistance conditions. The controlling portion stores correction values corresponding to different operation time regions and sliding resistance levels, and applies the appropriate correction to obtain an accurate operation time for control parameter determination, thereby resolving the inaccuracy caused by varying operating conditions
Solution Approach 2:
The patent implements feedback by measuring the actual operation time of the setting/operating device, comparing it with expected values, and using correction values to adjust the measurement. The controlling portion continuously monitors the operation time and applies corrections based on feedback about supply air pressure and sliding resistance conditions, ensuring accurate control parameter selection under varying conditions
2Productivity
If supply air pressure increases, then the operation time of the setting/operating device decreases, but this causes incorrect control parameter selection and dynamic characteristic issues
Solution Approach 1:
The patent addresses this contradiction by introducing correction values that compensate for the effect of supply air pressure on operation time. The controlling portion stores correction values corresponding to different supply air pressure levels and operation time regions, and applies the appropriate correction to obtain an accurate operation time for control parameter determination, ensuring reliable control parameter selection even when response speed varies
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating and storing correction values that counteract the expected effects of varying supply air pressure and sliding resistance. Before control parameter selection, the system retrieves the appropriate correction value based on measured conditions and applies it to the operation time measurement, preventing incorrect parameter selection before it occurs
3Duration of action of moving object
If sliding resistance of the valve stem is large, then the operation time increases, but this leads to incorrect size determination of the setting/operating device
Solution Approach 1:
The patent resolves this contradiction by introducing correction values that adjust the measured operation time based on sliding resistance conditions. The controlling portion stores correction values corresponding to different operation time regions and sliding resistance levels, and applies the appropriate correction to obtain an accurate operation time for control parameter determination, thereby resolving the inaccuracy caused by varying friction conditions
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
Enables the selection and setting of optimal control parameters even when operation time changes due to supply air pressure or friction, ensuring accurate valve opening control and reducing issues like stabilization time and overshooting.
Implementation Method 1
an electric-pneumatic converter converting the control output from the controlling portion to an air pressure signal
Implementation Method 2
a pilot relay amplifying the air pressure signal converted by the electric-pneumatic converter and outputting the amplified signal
Implementation Method 3
The gland packing 2f includes a plurality of ring-shaped packings provided in close contact with each other in the shaft direction of the valve stem 2d so as to prevent fluid from leaking from the gap
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
[Problem] To enable the optimum control parameters to be selected and set even when the operation time of the setting/operating device changes due to a supply air pressure or friction. [Means for Resolution] The measured operation time S1 of a setting/operating device is corrected using a first corrected value table TC and a second corrected value table TD and the size of the setting/operating device is defined based on the corrected operation time S1. The first corrected value table TC defines, as a first corrected value α1, the corrected value corresponding to the operation time region defined so as to correspond to the size of the setting/operating device and the sliding resistance region defined by dividing the range taken by the sliding resistance (friction) of the valve stem of a regulating valve and the second corrected value table TD defines, as a second corrected value α2, the corrected value corresponding to the operation time region defined so as to correspond to the size of the setting/operating device and the supply air pressure region defined by dividing the range taken by a supply air pressure Ps.