Dual-Valve Flow Rate Control for Sensor Sensitivity and High Flow
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Solution Overview
Problem
In semiconductor manufacturing, existing flow rate control apparatuses face challenges in maintaining high accuracy and sensitivity of pressure-type flow rate sensors while controlling fluid flow rates, as setting pressures too low restrict flow rates and varying set flow rates lead to inconsistent sensor characteristics.
Innovation Solution
The apparatus includes a first valve, a second valve, a fluid resistor, and pressure sensors to calculate and convert resistance flow rates into valve-specific flow rates, allowing for independent control of each valve to maintain low internal pressures and high sensitivity, enabling precise and rapid flow rate adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the set pressure is set low to improve sensor sensitivity, then the sensitivity of the pressure type flow rate sensor is improved, but the flow rate capability is reduced
Solution Approach 1:
The flow control system is divided into two independent control loops: a first control valve (V1) that controls upstream pressure to maintain sensor operating conditions, and a second control valve (V2) that controls downstream pressure to enable high flow rates. This segmentation allows each valve to optimize for its specific function, resolving the contradiction between low pressure for sensitivity and high flow rate capability.
2Productivity
If the set pressure is increased to enable high flow rates, then the flow rate capability is improved, but the sensor sensitivity deteriorates
Solution Approach 1:
The system separates pressure control functions into two independent zones: upstream of the sensor where low pressure is maintained for sensitivity, and downstream where higher pressure enables flow rate. The first valve controls the upstream zone while the second valve controls the downstream zone, allowing simultaneous optimization of both sensitivity and flow rate capability.
3Adaptability or versatility
If the set flow rate varies to meet different process requirements, then the adaptability is improved, but the control accuracy deteriorates due to changing sensor characteristics
Solution Approach 1:
The system employs feedback control in both loops: the first valve controller uses feedback from the pressure sensor to maintain constant upstream pressure, ensuring the sensor operates in its optimal sensitivity range regardless of flow rate changes. The second valve controller uses feedback from flow rate measurements to accurately control the final flow rate. This dual feedback mechanism maintains control accuracy across varying flow rate settings.
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 allows for accurate and high-speed flow rate control by maintaining low internal pressures and high sensitivity of the flow rate sensors, improving the overall precision and responsiveness of the flow rate control system.
Implementation Method 1
a first pressure sensor that measures a pressure in a first volume between the first valve and the fluid resistor
Implementation Method 2
a second pressure sensor that measures a pressure in a second volume between the fluid resistor and the second valve
Implementation Method 3
a fluid resistor arranged between the first valve and the second valve in the flow channel
Data Source
AI summary
A flow rate control apparatus calculates a resistance flow rate, which is a flow rate of a fluid flowing through the fluid resistor, based on a first pressure measured by a first pressure sensor and a second pressure measured by a second pressure sensor, converts the resistance flow rate to a first valve flow rate, which is the flow rate of the fluid passing through a first valve, based on the first pressure, converts the resistance flow rate to a second valve flow rate, which is the flow rate of the fluid passing through a second valve, based on the second pressure, controls the first valve so that the deviation between a first set flow rate and the first valve flow rate becomes small, and controls the second valve so that the deviation between a second set flow rate and the second valve flow rate becomes small.