Observer-Based Valve Flow Rate Control Without Delay Noise
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Solution Overview
Problem
Existing flow rate control apparatuses in semiconductor manufacturing suffer from time delays and noise in downstream-side valve flow rate measurements, affecting responsiveness and accuracy.
Innovation Solution
A flow rate control apparatus with a downstream-side valve flow rate meter and an observer that estimates the flow rate using a downstream-side valve flow rate estimation model, reducing noise and time delay by feeding back the deviation between measured and estimated values, and incorporating a PID controller for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a downstream-side valve flow rate meter is used to measure the actual flow rate passing through the downstream-side valve, then the measurement accuracy is improved, but the measured flow rate includes large noise that becomes problematic for flow rate control
Solution Approach 1:
The patent introduces an observer as an intermediary component that does not directly use the noisy measured flow rate signal. Instead, the observer estimates the downstream-side valve flow rate by processing the raw measurement through a mathematical model that filters out noise while preserving the actual flow rate information, thus mediating between the noisy sensor and the control system
Solution Approach 2:
The patent implements feedback by using the observer to continuously estimate the flow rate and compare it with the set flow rate. The estimated flow rate information is fed back to the downstream-side valve controller, which adjusts the valve opening degree to minimize the deviation between estimated and set flow rates, creating a closed-loop control system that reduces noise impact
2Object-affected harmful factors
If a low-pass filter is applied to remove noise from the downstream-side pressure signal, then the noise is reduced, but a time delay occurs that prevents obtaining the actual downstream-side valve flow rate without delay
Solution Approach 1:
The patent replaces the traditional mechanical low-pass filter approach with a mathematical estimation model (observer). Instead of physically filtering the pressure signal which introduces time delay, the system uses computational algorithms to estimate the flow rate from the pressure signal, achieving noise reduction without the temporal lag associated with physical filtering
Solution Approach 2:
The patent changes the parameter representation from directly using the noisy pressure signal to using an estimated flow rate parameter derived through mathematical transformation. By transforming the pressure signal through differential equations and estimation algorithms, the system obtains a new parameter (estimated flow rate) that has noise removed but maintains temporal responsiveness
3Device complexity
If the measured flow rate with time delay is used for control, then the control system is simpler, but the responsiveness of the flow rate control required in the semiconductor manufacturing process cannot be achieved
Solution Approach 1:
The patent applies preliminary action by estimating the current flow rate before it is actually measured by the downstream-side valve flow rate meter. The observer predicts what the flow rate should be based on the valve opening degree and system model, providing advance flow rate information that enables faster control response without waiting for the delayed physical measurement
Data Source
AI summary
A flow rate control apparatus can obtain a flow rate of a fluid passing through a downstream-side valve in a form in which noise is significantly reduced with little time delay, and has improved responsiveness. The flow rate control apparatus includes: a downstream-side valve flow rate meter that measures a downstream-side valve flow rate that is a flow rate of a fluid passing through a downstream-side valve; and an observer including a downstream-side valve flow rate estimation model that estimates the downstream-side valve flow rate on the basis of an input parameter that changes an opening degree of the downstream-side valve. The observer is configured so as to be fed back a deviation between the measured value of the downstream-side valve flow rate and the estimated value of the downstream-side valve flow rate.