Multi-channel gas high-precision mixing control system and method

Abstract

The invention discloses a multi-channel gas high-precision mixing control system and method, which are suitable for the technical field including but not limited to welding and cutting shielding gas control. Aiming at the problems of pressure fluctuation, large flow measurement deviation, proportion misalignment and the like in the existing high-pressure gas mixing, the system comprises a high-pressure gas cylinder, a mixing control terminal and a gas mixing tank, a plurality of laminar flow gas paths are arranged in the mixing control terminal, pressure is stabilized through a pressure proportional valve, flow is controlled through a flow proportional valve MFC, and high-precision flow sampling is achieved; fitting the dynamic relationship between the driving current and the flow of the MFC under the specific input pressure through binary linear regression, and adjusting the MFC in a stepping manner by setting parameters; based on abnormal flow self-adaptive compensation and historical parameter storage and reuse, rapid and accurate mixing of multi-component gas under high pressure is realized; the mixing precision and stability are remarkably improved, the adjusting period is shortened, the operation and maintenance cost is reduced, and the method is suitable for industrial scenes such as welding and semiconductor manufacturing.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding and cutting protection gas control, and particularly relates to a multi-channel gas high-precision mixing control system and method. BACKGROUND

[0002] In the industrial fields of welding and cutting processing, semiconductor manufacturing, etc., the mixing precision of multi-component welding protection gas directly determines the product processing quality. Especially in the high-pressure gas mixing scene, the accurate control of gas proportion is a core technical requirement. The existing high-pressure gas mixing system mostly adopts a single-channel or simple multi-channel structure, and directly adjusts the flow through a conventional flow proportional valve (MFC), but has the following key technical defects: firstly, the gas flow state is complex under high-pressure conditions, the existing system lacks an effective pressure stabilization mechanism, which leads to severe fluctuations in the inlet gas pressure, and further causes difficulty in stable flow control; secondly, the flow measurement method is extensive, and mostly relies on the sensor module of the MFC, without setting an independent high-precision sampling unit, the measurement error is large, and the influence of temperature on flow detection is not considered, further exacerbating the measurement deviation; thirdly, the relationship between the driving current of the MFC and the actual flow is not dynamically fitted in combination with the real-time pressure, and only fixed parameter control is adopted, which leads to a significant deviation of the flow from the target value under high-pressure environment, and ultimately causes the proportion of each component gas to be inaccurate; fourthly, the adjustment response is lagging, and there is no self-adaptive adjustment mechanism for abnormal flow, which cannot quickly compensate when the flow of a single channel is abnormal, and is easy to cause the overall performance of the mixed gas to be substandard; fifthly, the parameters need to be recalibrated every time the mixing is performed, historical control data cannot be reused, and the operation is tedious and inefficient. The above defects seriously restrict the precision, stability and practicability of high-pressure gas mixing, and it is difficult to meet the demand of industrial production for high-precision mixed gas. SUMMARY

[0003] The application provides a multi-channel gas high-precision mixing control system and method, which collects the flow data of each laminar flow path, fits the relationship between the driving current of the control flow proportional valve MFC and the laminar flow path flow under different pressure states, adjusts the MFC through the target flow corresponding driving current, and obtains the stable flow rate of the laminar flow under the current pressure state, and outputs to the gas mixing tank for full mixing, to realize the high-precision mixing of high-pressure mixed gas.

[0004] Technical scheme: a multi-channel gas high-precision mixing control system, comprising a plurality of high-pressure gas cylinders, a mixing control terminal and a gas mixing tank; the mixing control terminal is internally provided with a plurality of laminar flow paths, each laminar flow path input end is connected to the high-pressure gas cylinder through a pressure proportional valve, and the output end is connected to the gas mixing tank through a flow proportional valve MFC; the mixing control terminal further comprises an MCU for collecting gas flow data, controlling the opening and closing degree of the pressure proportional valve and the MFC.

[0005] Further, each layer of the gas path side is respectively provided with a capillary measurement gas path; the capillary measurement gas path and the corresponding layer flow gas path have a fixed value of flow rate ratio; a sampling point is found on each capillary measurement gas path to place a sensor for measuring the flow rate of the gas path.

[0006] Further, the heating resistance wire is uniformly wound on the copper wire, and the copper wire is used to equidistantly wind the upstream temperature measuring resistance wire M1 and the downstream temperature measuring resistance wire M2; when gas flows, the temperature of the upstream resistance M1 is lower than that of the downstream resistance M2, and a pressure difference is generated; the MCU outputs a constant micro-current for constant-current heating of the heating resistance; after the micro pressure difference signal caused by the temperature difference at M1 and M2 is differentially amplified through a bridge circuit, the signal is input to the MCU for flow rate calculation.

[0007] Further, a reference resistance NTC is arranged away from M1 and M2 for measuring the current gas temperature and performing temperature compensation.

[0008] Further, the MCU communicates data with the pressure proportional valve and the MFC through the RS485 bus, and directly controls the opening and closing degree of the valve core of the pressure proportional valve and the MFC through the output driving current.

[0009] A method based on the above-mentioned multi-channel gas high-precision mixing control system, which realizes high-precision and rapid mixing of gas through a step-by-step MFC adjustment method; the method comprises the following steps: Step S1, the MCU sets the sensor sampling frequency Fs1, the concentration C1, C2,..., Cn of each gas in the mixed gas, and the pressure of the laminar flow gas path; the sum of the concentrations of the various gases is 100%; Step S2, the MCU controls the pressure proportional valve to adjust the pressure of the laminar flow gas path to the set value, collects and calculates the flow rate of each laminar flow gas path in real time through the sensor, and fits the function relationship between the driving current of the MFC proportional valve and the flow rate of the gas path at the set pressure through a binary linear regression; Step S3, during the formal gas mixing process, when the MCU obtains the effective sensor data and the concentration ratio of each gas in the mixed gas, the pressure proportional valve is opened, and high-pressure gas flows in; the MCU obtains the target flow rate corresponding to each gas path based on the preset gas concentration and the collected effective flow rate data, obtains the driving current corresponding to the target flow rate according to the function relationship obtained in step S2, and inputs the MFC to control the opening and closing degree of the valve core; at the same time, the flow rate and driving current data are continuously obtained, and the MFC is step-by-step adjusted based on the difference between the measured flow rate and the target flow rate; Step S4, when the flow rate of any gas path decreases, the driving current of the MFC is increased, if the flow rate cannot continue to increase, the flow rate of another gas path is decreased, the concentration ratio of the mixed gas is ensured to be correct, and an alarm is given at the same time; when the flow rate of any gas path increases, the driving current of the MFC is decreased, if the flow rate cannot be decreased, the flow rate of another gas path is increased, and an alarm is given. Step S5, when detecting that the actual flow reaches the target flow, the MCU collects the gas path pressure information, the corresponding pressure proportional valve driving current, the gas concentration and the MFC driving current and saves them; in subsequent control, the MFC driving current corresponding to the mixed gas proportion is automatically matched according to the mixed gas concentration; the actual pressure is substituted into the MFC driving current for quantitative fine adjustment, so that the flow is quickly controlled.

[0010] Compared with the prior art, the technical scheme adopted by the present application has the following beneficial effects: (1) The present application realizes the unified and stable control of the input pressure of multiple gas paths by the combination design of the pressure proportional valve and the laminar flow path, thereby suppressing the flow fluctuation under high pressure working condition from the source; the 1:100 ratio capillary measurement gas path and the double-path heating resistance wire temperature measurement structure are matched, the temperature compensation function of the NTC reference resistance is combined, the precision of the flow sampling is greatly improved, the small flow change can be accurately captured after the bridge-type circuit differential amplification; the dynamic relationship between the MFC driving current and the flow is fitted by the binary linear regression, the closed-loop accurate regulation and control of the flow under high pressure environment is realized, the proportion error of each component gas is greatly reduced, and the high-precision mixing requirement is met.

[0011] (2) By storing the historical mixing parameters, the subsequent similar mixing requirements can directly call and quantitatively fine-tune without re-fitting the parameters, so that the adjustment cycle is greatly shortened, the rapid switching of the mixing proportion is realized; the step-by-step adjustment mechanism and the abnormal flow alarm compensation function ensure that the flow deviation is corrected in time, avoid the proportion imbalance, and improve the reliability of the mixing process. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 A multi-channel gas high-precision mixing control system structure diagram is provided for the present application; Figure 2 A flow real-time sampling principle diagram is provided for the present application; Figure 3 A flow measurement principle diagram is provided for the present application. DETAILED DESCRIPTION

[0013] The present application provides a multi-channel gas high-precision mixing control system and method, aiming at the problem that the pressure of the welding protection gas is high, the flow is difficult to control smoothly, and the proportion of various types of gas is not accurate in the prior art, a multi-channel high-pressure gas mixing control system and control method are designed, the flow data of each laminar flow path is collected in real time through a high-precision flow measurement system, the relationship between the driving current of the control flow proportional valve MFC and the laminar flow path flow is fitted under different pressures, the driving current corresponding to the target flow is adjusted continuously, the MFC is adjusted until the stable flow rate of the laminar flow under the current pressure state is obtained, and then the laminar flow is output to the gas mixing tank for full mixing, so that the high-precision mixing of the high-pressure mixed gas is realized.

[0014] The application will be further explained in connection with the accompanying drawings.

[0015] As Figure 1 shown, the application provides a multi-channel gas high-precision mixing control system, which comprises external multi-input high-pressure gas cylinders, a mixing control terminal and a gas mixing tank. According to the actual high-pressure gas mixing needs, different types of protective gas are provided by separate external high-pressure gas cylinders and fixedly connected to the mixing control terminal. The mixing control terminal is internally provided with several laminar flow gas paths, and a double-channel laminar flow gas path structure is adopted in this embodiment. A self-locking joint is arranged at the input end of each laminar flow gas path, and the high-pressure gas cylinder and the internal pressure proportional valve are connected to the two sides, respectively. The pressure proportional valve is used to stabilize the gas flow pressure. The output end of each laminar flow gas path is further connected with a flow proportional valve MFC, and the other end of the MFC is connected to the gas mixing tank through a self-locking joint. The flow proportional valve is used to control the flow of the protective gas, thereby controlling the input proportion of each gas in the gas mixing tank. The mixing control terminal further comprises an MCU, which is used to complete the real-time acquisition of the flow data of each gas in the laminar flow gas path and the control of the pressure proportional valve and the flow proportional valve. The MCU controls the opening degree of the pressure proportional valve at the input end through the RS485 bus communication, so as to keep the input pressure of each type of protective gas stable at the set value.

[0016] In addition, a double-channel sensor sampling system is designed in this embodiment for real-time flow sampling. As Figure 2 shown, a capillary measurement gas path is arranged at the side of each laminar flow gas path. The flow rate of the capillary measurement gas path is set to be 1:100 of the gas volume of the laminar flow gas path. By measuring the flow rate of the capillary measurement gas path, the flow rate of the laminar flow gas path can be obtained. Sampling points A and B are sensor placement points, and the measurement method of point A is described below.

[0017] As Figure 3 shown, the heating resistance wire is uniformly wound on the copper wire, and the copper wire is equidistantly wound with the upstream temperature measuring resistance wire M1 and the downstream temperature measuring resistance wire M2. When there is no gas flow, the heating resistance wire is heated, the temperatures of M1 and M2 are the same, and the resistance values are also the same, and there is no voltage difference. When there is gas flow, the temperature of the upstream resistance M1 is lower than that of the downstream resistance M2, and a pressure difference is generated. The M1 and M2 resistances are selected to have constant current input, the MCU generates a 0-1V control signal through a D / A conversion chip, the signal realizes 0-20mA constant current output through a voltage / current conversion circuit, and is used for constant current heating of the heating resistance. The small pressure difference signal caused by the different temperatures at M1 and M2 is amplified by a bridge circuit and then input into the MCU for flow rate calculation. In addition, a reference resistance NTC is arranged away from M1 and M2 in this embodiment, which is used to measure the current gas temperature and perform temperature compensation.

[0018] The MCU directly controls the opening and closing degree of the valve core of the MFC in each layer flow gas path by driving current, realizes gas flow control, and ensures that the proportion of each protective gas entering the gas mixing tank is consistent with the target set value and mixed according to requirements.

[0019] On the basis of the above-mentioned multi-channel gas high-precision mixing control system, the application also provides a matching mixing gas proportion rapid adjustment method, which is as follows: Step S1, the MCU sets the sensor sampling frequency Fs1, the concentration C1, C2,..., Cn of each gas in the mixed gas, and the pressure of the laminar flow gas path. Step S2, the MCU controls the pressure proportional valve to adjust the pressure of the laminar flow gas path to the set value, collects and calculates the flow rate of each path in real time through the sensor, and fits the function relationship between the driving current of the MFC proportional valve and the gas path flow rate under the set pressure.

[0020] Step S3, in the formal gas mixing process, when the MCU obtains effective sensor data and the concentration proportion of each gas in the mixed gas, the pressure proportional valve is opened and high-pressure gas flows in. The MCU obtains the target flow rate corresponding to each gas path based on the preset gas concentration and the collected effective flow rate data, obtains the driving current corresponding to the target flow rate according to the function relationship obtained in step S2, and inputs the MFC to control the opening and closing degree of the valve core. At the same time, the gas path flow rate and driving current data are continuously collected, and the MFC is stepwise adjusted based on the difference between the measured flow rate and the target flow rate.

[0021] Step S4, when the flow rate of any gas path decreases, the driving current of the MFC is increased, and if the flow rate cannot continue to increase, the flow rate of another gas path is reduced to ensure that the concentration proportion of the mixed gas is correct, and an alarm is given at the same time; when the flow rate of any gas path increases, the driving current of the MFC is reduced, and if the flow rate cannot be reduced, the flow rate of another gas path is increased, and an alarm is given.

[0022] Step S5, when it is detected that the actual flow rate reaches the target flow rate, the MCU collects the pressure information of each gas path, the corresponding pressure proportional valve driving current, the gas concentration, and the MFC driving current and saves them. In subsequent control, the MFC driving current corresponding to the mixed gas proportion can be automatically matched according to the mixed gas concentration. The actual pressure is substituted to perform quantitative fine adjustment, so that the flow rate can be quickly controlled, and the mixed gas with rapid proportion control is achieved.

[0023] The above-mentioned is only the preferred embodiment of the application, and it should be pointed out that for ordinary skilled persons in the technical field, several improvements and refinements can be made without departing from the principles of the application, and these improvements and refinements should also be regarded as the protection scope of the application.

Claims

1. A multi-channel high-precision gas mixing control system, characterized in that, It includes several high-pressure gas cylinders, a mixing control terminal, and a mixing tank; the mixing control terminal has several laminar flow gas paths inside, the input end of each laminar flow gas path is connected to the high-pressure gas cylinder through a pressure proportional valve, and the output end is connected to the mixing tank through a flow proportional valve (MFC); the mixing control terminal also includes an MCU for collecting gas flow data and controlling the opening and closing degree of the pressure proportional valve and the MFC.

2. The multi-channel high-precision gas mixing control system according to claim 1, characterized in that, Each layer of gas path is provided with a capillary measuring gas path on its side; the flow rate ratio of the capillary measuring gas path to the corresponding laminar flow gas path is a fixed value; a sampling point is found on each capillary measuring gas path to place a sensor for measuring the gas path flow rate.

3. The multi-channel high-precision gas mixing control system according to claim 2, characterized in that, The heating resistance wire is uniformly wound on a copper wire, and the upstream temperature measuring resistance wire M1 and the downstream temperature measuring resistance wire M2 are wound at equal intervals using the copper wire. When there is gas flow, the temperature of the upstream resistance M1 is lower than that of the downstream resistance M2, resulting in a pressure difference. The MCU outputs a constant micro current for constant current heating of the heating resistance. The small pressure difference signal caused by the temperature difference between M1 and M2 is differentially amplified by a bridge circuit and then input to the MCU for flow calculation.

4. The multi-channel high-precision gas mixing control system according to claim 3, characterized in that, A reference resistor NTC is placed away from M1 and M2 to measure the current gas temperature and perform temperature compensation.

5. The multi-channel high-precision gas mixing control system according to claim 1, characterized in that, The MCU communicates with the pressure proportional valve and MFC via an RS485 bus and directly controls the opening degree of the valve core of the pressure proportional valve and MFC by outputting drive current.

6. A method for a multi-channel high-precision gas mixing and control system based on any one of claims 1-5, characterized in that, Achieving high-precision and rapid gas mixing through a step-by-step MFC control method includes the following steps: Step S1: The MCU sets the sensor sampling frequency Fs1, the concentrations of various gases C1, C2, ... Cn in the mixed gas, and the pressure of the laminar flow path, respectively; the sum of the concentrations of various gases is 100%. Step S2: The MCU controls the pressure proportional valve to adjust the laminar flow gas path pressure to the set value. The flow rate of each laminar flow gas path is collected and calculated in real time by the sensor. The functional relationship between the MFC proportional valve drive current and the gas path flow rate under the set pressure is fitted by binary linear regression. Step S3: During the formal gas mixing process, when the MCU acquires valid sensor data and the concentration ratio of various gases in the mixed gas, it opens the pressure proportional valve, allowing high-pressure gas to flow in. Based on the preset gas concentration and the collected valid flow data, the MCU obtains the target flow rate for each gas path. According to the functional relationship obtained in step S2, it obtains the drive current corresponding to the target flow rate and inputs it into the MFC to control the valve core opening degree. At the same time, it continuously acquires gas path flow and drive current data, and adjusts the MFC stepwise based on the difference between the measured flow rate and the target flow rate. Step S4: When the flow rate of any gas path decreases, increase the MFC drive current. If the flow rate cannot be increased further, decrease the flow rate of the other gas path to ensure the correct concentration ratio of the mixed gas and issue an alarm. When the flow rate of any gas path increases, decrease the MFC drive current. If the flow rate cannot be decreased, increase the flow rate of the other gas path and issue an alarm. Step S5: When the actual flow rate reaches the target flow rate, the MCU collects and saves the pressure information of each gas path, the corresponding pressure proportional valve drive current, the gas concentration, and the MFC drive current. In subsequent control, the MCU automatically matches the MFC drive current of the corresponding mixed gas ratio according to the mixed gas concentration. The actual pressure is substituted to make quantitative fine-tuning of the MFC drive current to achieve rapid flow control.

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