Rotary Valve Setpoint Correction for Valve Rod Twist
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Solution Overview
Problem
Conventional rotary valves for controlling fluid flow rates in air conditioning systems suffer from accuracy issues due to twist in the valve rod caused by fluid pressure, leading to errors between measured and actual valve openings.
Innovation Solution
A rotary valve design that includes a valve opening setpoint correcting mechanism, which accounts for the twist in the valve rod by using correction values derived from the relationship between valve opening and differential pressure, allowing for precise control by adjusting the rotation of the valve rod to match the desired setpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a valve rod is rotated to control valve opening, then the valve opening can be adjusted, but the valve rod becomes twisted due to fluid pressure causing measurement errors
Solution Approach 1:
The patent implements a feedback mechanism where the actual valve opening is detected by a valve opening detector and fed back to the controller. The controller compares the detected opening with the target opening and adjusts the valve rod rotation accordingly, enabling closed-loop control that compensates for twist-induced measurement errors.
Solution Approach 2:
The patent changes the control parameter from direct valve rod rotation angle to a corrected opening value that accounts for twist. The controller calculates the twist amount based on the relationship between differential pressure and twist, then adjusts the target opening parameter to compensate for the expected measurement error, achieving accurate control despite rod twist.
2Device complexity
If the valve opening is controlled based on valve rod rotational position, then the control system is simple, but measurement errors occur due to valve rod twist
Solution Approach 1:
The patent introduces an intermediary calculation step where the controller computes the twist amount based on the relationship between differential pressure and valve rod twist. This intermediary parameter (twist amount) mediates between the simple rotational position detection and the accurate opening control, allowing the system to maintain simplicity while improving precision.
3Measurement precision
If additional sensors are added to compensate for measurement errors, then measurement accuracy improves, but device complexity and cost increase
Solution Approach 1:
The patent enables the existing valve opening detector to serve dual purposes: detecting both the valve opening position and providing information for twist compensation. The controller uses the detected opening value along with differential pressure information to calculate and compensate for twist effects, allowing the system to self-correct measurement errors without adding dedicated twist sensors or additional detection hardware.
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 solution enables high-precision control of valve openings by eliminating errors between actual and desired openings, improving the accuracy of fluid flow rate management in air conditioning systems without the need for additional sensors or increased hardware costs.
Implementation Method 1
when a front-back differential pressure (fluid pressure) is reduced, this pressure acts on the valve unit
Implementation Method 2
produces a frictional force between the valve rod and the bearing that supports the valve rod. This frictional force produces a torque in the valve rod
Data Source
AI summary
A valve opening setpoint corrector and a correction table storage are provided in a flow rate controlling valve. A correction table indicating valve opening correction values corresponding to combinations of amounts of opening of a valve and front-back differential pressures across the valve is stored in the correction table storage. In the valve opening setpoint corrector a correction value acquirer acquires, from the correction table, the valve opening correction value α that corresponds to the inputted measured value of the valve and front-back differential pressure across the valve and sends it to the setpoint corrector, as a correction value that takes into account the amount of twist in the valve rod. The setpoint corrector corrects, by the correction value taking into account the amount of twist in the valve rod, the valve opening setpoint from the air conditioning controller, sending this corrected valve opening setpoint to the valve opening controller.