Adaptive Mass Flow Controller for Multi-Gas Pressure Transients
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Solution Overview
Problem
Existing fluid flow control systems face challenges in accurately maintaining fluid flow set points during rapid pressure changes, as sensing devices may saturate or produce unreliable feedback signals, leading to over- or under-compensation.
Innovation Solution
A multi-mode control system that switches from closed-loop to open-loop mode when a threshold pressure change is detected, using pressure measurements and characterization data to adjust valve positions, and re-engages the closed-loop mode once conditions stabilize, allowing for improved accuracy and reduced control errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a closed-loop control algorithm is used to adjust fluid flow in response to changes in fluid flow conditions, then the fluid flow set point can be maintained under normal conditions, but during rapid pressure changes the sensing devices saturate or produce unreliable feedback signals causing the flow controller to over-compensate or under-compensate
Solution Approach 1:
The control system dynamically switches between closed-loop and open-loop modes based on the reliability of feedback signals. When rapid pressure changes cause sensor saturation or unreliable readings, the system transitions to open-loop mode using pre-stored characterization data, and returns to closed-loop mode when conditions stabilize, thereby adapting to changing operational conditions to maintain both reliability and precision
Solution Approach 2:
The system performs preliminary characterization of the mass flow controller under various pressure conditions and stores this data in advance. During rapid pressure changes when feedback becomes unreliable, the controller uses these pre-stored characterization curves to determine appropriate valve positions, eliminating the need for real-time feedback during unstable conditions
2Manufacturing precision
If the feedback control loop continuously adjusts the valve based on flow measurements, then the fluid flow set point is maintained under stable conditions, but during rapid pressure changes the system over-compensates or under-compensates due to saturated or unreliable feedback signals
Solution Approach 1:
The system introduces an intermediary mechanism that detects the reliability of feedback signals and mediates between the feedback control loop and the valve actuation. When feedback reliability deteriorates during rapid pressure changes, the intermediary switches control to open-loop mode using characterization data, preventing over-compensation or under-compensation while maintaining precision
3Adaptability or versatility
If sensing devices are used to detect changes in fluid flow conditions, then feedback signals can be generated for control adjustments, but during rapid pressure changes the sensing devices saturate or produce unreliable feedback signals
Solution Approach 1:
The measurement system dynamically adapts its operation mode based on pressure change rates. During rapid pressure changes that cause sensor saturation, the system transitions from relying on real-time feedback measurements to using pre-stored characterization data, thereby maintaining measurement precision across varying pressure conditions
Data Source
AI summary
A system and method for controlling a flow of a fluid using a multi-mode control algorithm is described. The method includes disengaging and engaging a feedback control loop that controls a valve of the mass flow controller based upon a rate of pressure change of the fluid. The method also includes calculating a valve position of the valve based on pressure measurements when the feedback control loop has been disengaged and characterization data that characterizes the mass flow controller, and determining, when the feedback control loop is first re-engaged, a difference between a measured flow rate and a flow set point. An adjustment to the characterization data is applied based upon the difference to improve an accuracy of the calculation of the valve position when the feedback control loop is disengaged again.