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Control method for gas path system of gas chromatograph

A gas chromatograph and gas path system technology, which is applied in the field of gas chromatograph gas path system control, can solve the problems of system stability and rapidity, the large difference from the optimal PID coefficient, etc., and achieve stable gas pressure and flow , The effect of fast closed-loop control

Active Publication Date: 2014-11-12
苏州冷杉精密仪器有限公司
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  • Summary
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  • Application Information

AI Technical Summary

Problems solved by technology

However, the transfer function of each closed-loop system is determined by multiple parameters. It is very preliminary to compensate the PID coefficient only through individual flow and pressure values. Although it is better than a system without any compensation, the distance is the best. PID coefficients are still quite different, and there are also problems with system stability and rapidity

Method used

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  • Control method for gas path system of gas chromatograph
  • Control method for gas path system of gas chromatograph
  • Control method for gas path system of gas chromatograph

Examples

Experimental program
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Embodiment

[0034] like Figure 1-2 As shown, the gas path system control method of the gas chromatograph:

[0035] (1) Pre-calibration of the open-loop transfer function of the proportional valve installed in the gas system:

[0036]Firstly, build a hardware platform for calibrating proportional valves. The hardware platform is composed of a host computer with a calibration program, a front-end pressure controller, a back-end pressure controller, and a flow controller. controller, back-end pressure controller and flow controller to stably control the current state of the air path until it meets the calibration requirements, and then send commands to the sinusoidal current generator through the host computer, and sweep the sinusoidal current with different frequencies to the proportional valve coil to obtain the proportional The amplitude and phase information of the valve open-loop transfer function at different frequencies, and then return the measurement results of the open-loop trans...

application example 1

[0043] like image 3 Shown is the working principle diagram of the closed-loop control loop for carrier gas inflow, which is used to control the total flow of carrier gas into the gas chromatograph. The head pressure in this circuit is the cylinder outlet pressure, which can be read from the pressure reducing valve. Backend pressure is the column head pressure, which can be read by a pressure sensor in the split loop in the gas chromatograph. The gas flow is measured by a flow sensor connected in series at the carrier gas inlet. Therefore, when the gas chromatograph is actually working, all the gas parameters of the proportional valve are known values. By querying the calibration table and performing interpolation, the amplitude and phase information of the current open-loop transfer function are obtained, and the PID parameters are corrected.

application example 2

[0045] like Figure 4 Shown is the working principle diagram of the closed-loop control circuit of the purge gas circuit. The front pressure in this circuit is the column head pressure of the gas chromatograph, which is measured by the pressure sensor in the split gas circuit. The back-end pressure is the purge gas pressure, which is measured by a pressure sensor connected in series behind the proportional valve. The gas flow through the proportional valve is the purge flow, which can be calculated from the characteristics of purge gas pressure, atmospheric pressure and air resistance. Therefore, when the gas chromatograph is actually working, all the gas parameters of the proportional valve are known values. By querying the calibration table and performing interpolation, the amplitude and phase information of the current open-loop transfer function can be obtained, and the PID parameters can be corrected.

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Abstract

The invention provides a control method for a gas path system of a gas chromatograph. The method includes the steps that an open-loop transfer function of a proportional valve arranged in the gas path system is pre-calibrated through an erected hardware platform for calibration, and a look-up table of amplitude and phase information at different frequencies of the open-loop transfer function of the proportional valve is made; an optimum PID parameter control value in a closed-loop system is set; finally, according to measured gas parameter values, the current gain and the current phase of the open-loop transfer function of the proportional valve are acquired through comparison with the look-up table, and PID parameter values in a control algorithm are corrected through the change of gains and phases. Through the open-loop characteristics of the pre-calibrated proportional valve, PID parameters of the closed-loop system are corrected according to currently-measured gas pressure and flow, and more stable and quicker closed-loop control over gas pressure and flow is achieved within a large application range.

Description

technical field [0001] The invention belongs to the fields of analytical chemistry and fluid control, in particular to a gas path system control method of a gas chromatograph. Background technique [0002] Gas chromatography is an important technique in analytical chemistry. A sample mixed with multiple compounds enters the gas chromatograph's inlet, mixes with the mobile phase (usually an inert gas) and enters the column. The sample follows the carrier gas along the column and is repeatedly partitioned between the mobile and stationary phases in the process, resulting in retention. Different samples have different retention levels, and they are gradually separated during the process of passing through the chromatographic column. The samples flowing out from the end of the chromatographic column are no longer mixed together, but flow out one by one. [0003] The time from when the sample enters the gas chromatograph to when the peak of the chromatogram emerges is called th...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N30/28G05B11/42G05D27/02G01N30/02
Inventor 余超宋新
Owner 苏州冷杉精密仪器有限公司
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