Pressure-Based Flow Rate Control With Dynamic Downstream Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional flow rate controllers using pressure-type sensors experience decreased accuracy at small flow rates due to high noise amplitude, as the pressure on the downstream side of the fluid resistor increases, affecting the measurement and control of flow rates.
Innovation Solution
A flow rate controller design that maintains a constant low pressure on the downstream side of the fluid resistor by adjusting the upstream pressure, using a first valve and a second valve, along with pressure sensors, to calculate and control the flow rate accurately across varying set flow rates, ensuring high measurement and control accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pressure on the downstream side of the fluid resistor is kept high to reduce differential pressure, then the flow rate control range is improved, but the measurement accuracy deteriorates due to increased noise amplitude
Solution Approach 1:
The patent applies dynamics by making the downstream pressure dynamic rather than fixed. The downstream pressure is automatically adjusted based on the set flow rate: it is kept low for small flow rates to reduce noise and improve measurement accuracy, and allowed to increase for large flow rates to maintain adequate differential pressure across the fluid resistor. This dynamic pressure adjustment resolves the contradiction between measurement accuracy and control range adaptability.
Solution Approach 2:
The patent changes the pressure parameter dynamically based on the operating conditions. Specifically, the downstream pressure parameter is varied according to the set flow rate to optimize both measurement accuracy and control performance. For small flow rates, the downstream pressure is maintained at a low level to minimize noise in the pressure sensors, thereby improving flow rate measurement accuracy. For large flow rates, the downstream pressure can be higher to ensure sufficient differential pressure across the fluid resistor, maintaining the full control range.
2Adaptability or versatility
If the pressure on the downstream side of the fluid resistor increases, then the control range is extended, but the noise amplitude increases causing decreased control accuracy
Solution Approach 1:
The patent makes the downstream pressure dynamic, adjusting it based on the set flow rate requirements. For small flow rates, the downstream pressure is kept low to minimize noise amplitude in the pressure sensors, thereby reducing harmful noise effects on measurement accuracy. For large flow rates, the downstream pressure is allowed to increase to maintain adequate differential pressure across the fluid resistor, ensuring the control range is sufficient. This dynamic adjustment eliminates the need to maintain high downstream pressure in all operating conditions.
3Stability of the object's composition
If the first measured pressure is kept constant at high supply pressure, then the upstream pressure stability is improved, but the downstream pressure increases causing reduced measurement accuracy
Solution Approach 1:
The patent applies dynamics by making the downstream pressure dynamic rather than fixed. The downstream pressure is automatically adjusted based on the set flow rate: it is kept low for small flow rates to reduce noise and improve measurement accuracy, and allowed to increase for large flow rates to maintain adequate differential pressure across the fluid resistor. This dynamic pressure adjustment resolves the contradiction between measurement accuracy and control range adaptability.
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
The solution maintains high flow rate accuracy and control precision regardless of the set flow rate, reducing noise and improving responsiveness, especially in semiconductor manufacturing processes.
Implementation Method 1
a first pressure sensor provided between the first valve and the fluid resistor; a second pressure sensor provided between the fluid resistor and the second valve; a resistor flow rate calculator that calculates a resistor flow rate that is a flow rate of a fluid flowing through the fluid resistor, on a basis of a first measured pressure measured by the first pressure sensor and a second measured pressure measured by the second pressure sensor
Implementation Method 2
The pressure-type flow rate sensor includes a fluid resistor such as a laminar flow element
Data Source
AI summary
Provided is a flow rate controller. The flow rate controller calculates a resistor flow rate that is a flow rate of a fluid flowing through a fluid resistor, on the basis of a first measured pressure measured by a first pressure sensor and a second measured pressure measured by a second pressure sensor; controls a second valve on the basis of a deviation of the resistor flow rate from the set flow rate; outputs a first set pressure that is a target of a pressure upstream of the fluid resistor, on the basis of the set flow rate and a second set pressure which is a target of a pressure downstream of the fluid resistor and to which a constant value is set; and controls the first valve on the basis of a deviation of the first measured pressure from the first set pressure.