Mass Flow Controller Valve Start Position Optimization
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Solution Overview
Problem
Mass flow controllers (MFCs) are not optimized for performance across various gases and operating conditions, leading to inconsistent responses and potential overshoot, as they are typically calibrated for N2 and may degrade when used with other gases, making calibration for multiple gases costly and impractical due to safety concerns and gas properties.
Innovation Solution
Performing calibration runs to determine optimal tuning parameters for each gas and operating condition, which are stored in the MFC memory for quick and accurate responses, including adjusting the initial valve start position to minimize delay and overshoot, and using a method to adapt to different gases and pressures by setting the valve to an initial position less than the typical opening position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If MFC is calibrated at manufacturer using N2 gas, then MFC performance is guaranteed for N2, but MFC performance significantly degrades when used with other gases
Solution Approach 1:
The patent changes the calibration parameters by determining optimal tuning parameters (valve start positions) for different gas types and operating conditions through calibration runs. The system stores multiple sets of tuning parameters corresponding to different gases and pressures, allowing the MFC to adapt its valve start position based on the specific gas and pressure conditions, thereby maintaining consistent performance across multiple gases without requiring separate manufacturer calibration for each gas.
2Reliability
If MFC is calibrated with each specific operating gas, then MFC performance is optimized for that gas, but calibration cost increases significantly
Solution Approach 1:
The patent implements self-service calibration by allowing the MFC to automatically determine optimal tuning parameters through calibration runs performed by the user. The system includes automated procedures where the MFC executes calibration sequences, collects data on flow rates and valve positions, calculates optimal tuning parameters, and stores them in memory without requiring manufacturer intervention or expensive external calibration services for each gas type.
3Speed
If MFC operates in quick-response mode, then response speed is improved, but overshoot of desired mass flow rate occurs
Solution Approach 1:
The patent applies preliminary action by determining and storing optimal valve start positions for different gas and pressure conditions before actual operation. During calibration runs, the system pre-calculates the optimal initial valve position that will achieve the desired flow rate without overshoot for each specific gas and pressure combination. When operating in quick-response mode, the MFC retrieves the appropriate pre-determined valve start position, enabling fast response while avoiding overshoot that would otherwise occur with standard valve start positions.
4Adaptability or versatility
If MFC needs to provide consistent response across varying pressures and gases, then multi-gas application capability is improved, but device complexity increases
Solution Approach 1:
The patent segments the calibration and operation process into distinct, manageable components. The system divides the calibration runs into separate tests for different pressure conditions and gas types, with each run determining specific tuning parameters for that condition. The MFC memory is segmented to store multiple sets of tuning parameters indexed by gas type and pressure. During operation, the system segments the decision-making by automatically selecting the appropriate parameter set based on detected gas and pressure conditions, simplifying the user interface while maintaining comprehensive multi-gas capability.
Data Source
AI summary
One method of obtaining an initial adjusted mass flow controller valve start position comprises obtaining a mass flow controller delay period and setting a mass flow controller valve to an initial valve opening position that is less than an expected optimal valve opening position. An initial desired flow rate and initial operating conditions are input into a control system that is in communication with the valve, and the control system is initiated. The control system is adapted to adjust the valve opening position to achieve the initial desired flow rate, while taking into account flow rate and valve position feedback to the control system. During operation of the MFC and control system, the valve position and the flow rate are recorded in one embodiment and a flow rate that one of meets and exceeds a threshold is detected. An initial-flow time-period extending from the time of control system initiation to detection of the threshold being one of met and exceeded is determined and the mass flow controller delay period from the initial flow time period is subtracted from the initial-flow time-period to obtain an adjusted start time. The valve opening position at the adjusted start time is set as the initial adjusted mass flow controller valve start position.