Spool Valve Control with Nonlinear Flow Compensation
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Solution Overview
Problem
The spool type flow control valve experiences non-linearity in flow rate characteristics, particularly when the spool is near the neutral position, leading to deteriorated controllability of the control target.
Innovation Solution
A control device that includes a controller to generate a spool position command for the spool type flow control valve and a non-linear compensator that applies a correction to linearly compensate for the non-linear flow rate characteristics, thereby improving controllability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spool type flow control valve is used to control gas flow rate, then the flow rate can be controlled, but non-linear flow rate characteristics occur particularly when the spool is near the neutral position, leading to deteriorated controllability
Solution Approach 1:
The patent applies parameter changes by introducing a non-linear compensator that modifies the spool position command based on the spool position. The compensator changes the effective gain of the control system dynamically - increasing gain when the spool is near the neutral position and decreasing gain when the spool is away from neutral. This compensates for the non-linear flow rate characteristics and improves controllability throughout the entire operating range.
2Quantity of substance
If the spool is positioned near the neutral position, then small flow rate adjustments are achieved, but non-linear characteristics cause deteriorated controllability
Solution Approach 1:
The patent implements dynamics by making the control gain dynamic rather than fixed. The non-linear compensator continuously adjusts the effective gain based on the instantaneous spool position. When the spool is near neutral, the compensator increases the gain to enhance controllability for small flow rate adjustments. When the spool is away from neutral, the compensator decreases the gain to maintain stability for larger flow rate changes.
3Measurement precision
If a static pressure air bearing is used to support the spool, then sliding friction is eliminated and high positioning accuracy is achieved, but the non-linear flow rate characteristics remain
Solution Approach 1:
The patent applies feedback by using the detected spool position information to generate a compensated spool position command. The non-linear compensator receives the actual spool position as feedback and adjusts the command signal accordingly. This closed-loop compensation approach addresses the non-linear flow rate characteristics while preserving the benefits of high positioning accuracy achieved through the static pressure air bearing.
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 proposed solution effectively improves the controllability of the control target by linearizing the flow rate characteristics, enhancing the accuracy and responsiveness of the spool type flow control valve.
Implementation Method 1
a spool is supported by a sleeve via a static pressure air bearing in a non-contact manner
Data Source
AI summary
There is provided a control device that controls a controlled variable of a control target to a target value by controlling a flow rate of gas supplied to and discharged from the control target by a spool type flow control valve. The control device includes a controller that generates a spool position command of the spool type flow control valve, based on the target value, and a non-linear compensator that applies a correction for linearly compensating for non-linear flow rate characteristics of the spool type flow control valve to the generated spool position command, and outputs the command to the spool type flow control valve.