CN109470325B - Gas flow measuring method and device, control system and gas mass flowmeter - Google Patents
Gas flow measuring method and device, control system and gas mass flowmeter Download PDFInfo
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- CN109470325B CN109470325B CN201811117616.1A CN201811117616A CN109470325B CN 109470325 B CN109470325 B CN 109470325B CN 201811117616 A CN201811117616 A CN 201811117616A CN 109470325 B CN109470325 B CN 109470325B
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- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
Abstract
The invention discloses a gas flow measuring method, a device, a control system, a gas mass flowmeter and a storage medium, comprising: acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor; determining data of a current gas flow rate based on the second flow rate data if the change status is a slow change status; if the change state is a fast change state, obtaining data of the current gas flow based on the first flow data and the conversion coefficient function; the conversion coefficient function is subjected to correction processing based on the first flow volume data and the second flow volume data. The method, the device, the control system, the gas mass flowmeter and the storage medium can fully utilize the advantage of quick response of the MEMS sensor; long-term accuracy, linearity, repeatability and special gas applicability of the product can be guaranteed, and data cannot be mutated during correction; the flow testing precision is improved.
Description
Technical Field
The invention relates to the technical field of flow detection, in particular to a gas flow measuring method, a gas flow measuring device, a gas flow measuring control system, a gas mass flowmeter and a storage medium.
Background
Various fluids such as air, water and gas are very closely related to daily life and social activities of people, and when various fluids are used, the properties and the quantity of the fluids need to be measured. Thermal gas mass flowmeters (thermal gas mass flowmeters, thermal MFMs for short) are used for precisely measuring the mass flow of gas, and have important applications in scientific research and production in various fields such as semiconductor integrated circuit processes, special materials, chemical industry, petroleum industry, medicine, environmental protection, vacuum and the like. However, since the thermal MFM measures the flow rate by heat transfer, the response time of the thermal gas mass flowmeter is slow, generally 1 to 10 seconds, and when the flow rate changes greatly, the thermal gas mass flowmeter generates a large measurement error.
Disclosure of Invention
In view of the above, an object of the present invention is to provide a gas flow measuring method, a gas flow measuring apparatus, a gas mass flow meter, and a storage medium.
According to an aspect of the present invention, there is provided a gas flow measuring method including: acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor; determining a change state of the gas flow based on the first flow data and a preset state judgment rule; determining data of a current gas flow rate based on the second flow rate data if the change status is a slow change status; if the change state is a fast change state, obtaining data of the current gas flow based on the first flow data and a conversion coefficient function; and if the conversion coefficient function needs to be corrected, correcting the conversion coefficient function based on the first flow data and the second flow data, and replacing the current conversion coefficient function with the obtained new conversion coefficient function.
Optionally, sequentially obtaining N first flow data and N second flow data based on a preset time interval, and obtaining an MEMS sensor data array M and a thermal flow sensor data array T, respectively; obtaining a difference value between the maximum element value and the minimum element value in the M, taking the difference value as a flow change value, and judging whether the flow change value is larger than a preset first threshold value or not; if yes, determining the change state as a fast change state, and converting the initial conversion coefficient function f0(x) As a function f of the current conversion coefficient1(x) Taking the product of the last element value in the M and the current conversion coefficient function as the data of the current gas flow; if not, determining that the change state is a slow change state, and taking the last element value in the T as the data of the current gas flow.
Optionally, first flow calibration data acquired by the MEMS sensor and second flow calibration data acquired by the thermal flow sensor corresponding to the plurality of flow points are obtained in advance; calculating the ratio of the first flow calibration data to the corresponding second flow calibration data to obtain a plurality of calibration point data, wherein the abscissa of the calibration point is a flow point, and the ordinate is the ratio corresponding to the flow point; performing curve fitting on the plurality of calibration point data by adopting a polynomial fitting method to obtainF is0(x)。
Optionally, the correcting the conversion coefficient function according to the first flow data and the second flow data includes: judging whether the flow change value is smaller than or equal to a preset second threshold value or not; if yes, calculating the average value of all elements in the T
And the average of all elements in said M
And records the current flow point x1(ii) a Judgment of
And
whether the absolute value of the difference is less than or equal to a third threshold value, and if not, a new index point data (x) is used1，
) Replacing abscissa data and the x in the plurality of index point data1The closest index point data; performing curve fitting on the newly obtained calibration point data by adopting a polynomial fitting method to obtain a new conversion coefficient function f2(x)。
Optionally, f is periodically modified based on the correction interval duration1(x) Such that f1(x) Approach f2(x) And make a judgment on
Whether it is less than or equal to the first threshold value, and if so, stopping periodically modifying f1(x) And using the parameters of f2(x) Substitution f1(x)。
Optionally, assigning a subsequent element of the M and the T to a previous element, and performing a shift process; acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor based on a preset time interval; assigning the first traffic data and the second traffic data to the last element of said M and said T, respectively; and after assigning a value to the last element of M and T, executing the step of determining the change state of the gas flow based on the first flow data and a preset state judgment rule, and performing cyclic processing.
According to another aspect of the present invention, there is provided a gas flow measurement device including: the data acquisition module is used for acquiring first flow data acquired by the MEMS sensor and second flow data acquired by the thermal flow sensor; the state judgment module is used for determining the change state of the gas flow based on the first flow data and a preset state judgment rule; a data determination module for determining data of a current gas flow based on the second flow data if the change status is a slow change status; if the change state is a fast change state, obtaining data of the current gas flow based on the first flow data and a conversion coefficient function; a function correction module, configured to, if it is determined that the conversion coefficient function needs to be corrected, perform correction processing on the conversion coefficient function based on the first flow data and the second flow data; and the function replacing module is used for replacing the current conversion coefficient function with the obtained new conversion coefficient function.
Optionally, the data acquisition module is configured to sequentially obtain N first flow data and N second flow data based on a preset time interval, and obtain an MEMS sensor data array M and a thermal flow sensor data array T, respectively; the state judgment module is used for obtaining a difference value between the maximum element value and the minimum element value in the M, using the difference value as a flow change value, and judging whether the flow change value is larger than a preset first threshold value; if yes, determining that the change state is a fast change state, and if not, determining that the change state is a slow change state; the data determination module is used for determining the initial conversion coefficient function f if the change state is determined to be a fast change state0(x) As a function f of the current conversion coefficient1(x) Taking the product of the last element value in the M and the current conversion coefficient function as the data of the current gas flow; and if the change state is determined to be a slow change state, taking the last element value in the T as the data of the current gas flow.
Optionally, the function presetting module is configured to obtain in advance first flow calibration data acquired by the MEMS sensor and second flow calibration data acquired by the thermal flow sensor corresponding to the plurality of flow points; calculating the ratio of the first flow calibration data to the corresponding second flow calibration data to obtain a plurality of calibration point data, wherein the abscissa of the calibration point is a flow point, and the ordinate is the ratio corresponding to the flow point; performing curve fitting on the plurality of calibration point data by adopting a polynomial fitting method to obtain the f0(x)。
Optionally, the function correction module is configured to determine whether the flow rate variation value is smaller than or equal to a preset second threshold value; if yes, calculating the average value of all elements in the T
And the average of all elements in said M
And records the current flow point x1(ii) a Judgment of
And
whether the absolute value of the difference is less than or equal to a third threshold value, and if not, a new index point data (x) is used1，
) Replacing abscissa data and the x in the plurality of index point data1The closest index point data; by using a plurality of termsPerforming curve fitting on the newly obtained multiple calibration point data by the formula fitting method to obtain a new conversion coefficient function f2(x)。
Optionally, the function replacement module is configured to periodically modify f based on the correction interval duration1(x) Such that f1(x) Approach f2(x) And make a judgment on
Whether it is less than or equal to the first threshold value, and if so, stopping periodically modifying f1(x) And using the parameters of f2(x) Substitution f1(x)。
Optionally, the data assigning module is configured to assign a subsequent element of the M and the T to a previous element, and perform shift processing; acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor based on a preset time interval; assigning the first traffic data and the second traffic data to the last element of said M and said T, respectively;
after assigning a value to the last element of M and T, the state decision module performs the step of determining the change state of the gas flow based on the first flow data and a preset state decision rule, and performs a loop process.
According to still another aspect of the present invention, there is provided a control system comprising: the gas flow measuring device as above.
According to yet another aspect of the invention, there is provided a gas mass flow meter comprising: a control system as described above.
According to still another aspect of the present invention, there is provided a gas flow measurement device including: a memory; and a processor coupled to the memory, the processor configured to perform the method as described above based on instructions stored in the memory.
According to yet another aspect of the present invention, there is provided a computer readable storage medium having stored thereon computer instructions for execution by a processor to perform the method as described above.
According to the gas flow measuring method, the gas flow measuring device, the control system, the gas mass flowmeter and the storage medium, the thermal flow sensor and the MEMS flow sensor are configured on the flowmeter, the data of different sensors are switched by judging the speed of flow change, and the advantage of fast response of the MEMS sensors can be fully utilized; the accuracy of the MEMS is corrected by using the thermal sensor data through a self-correction method of the flowmeter, the long-term accuracy, the linearity, the repeatability and the special gas applicability of a product can be ensured, and the data cannot be mutated during correction; the flow testing precision is improved, and the working efficiency is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic flow chart diagram of one embodiment of a gas flow measurement method according to the present invention;
FIG. 2 is a schematic diagram of a control system for a gas mass flow meter;
FIG. 3 is a schematic structural diagram of a gas mass flow meter;
FIG. 4 is a schematic flow chart diagram of another embodiment of a gas flow measurement method according to the present invention;
FIG. 5 is a schematic flow chart of flow correction in another embodiment of a gas flow measurement method according to the present invention;
FIG. 6 is a schematic flow chart of a timer interrupt in another embodiment of a gas flow measurement method according to the present invention;
FIG. 7 is a block schematic diagram of one embodiment of a gas flow measurement device according to the present invention;
FIG. 8 is a block schematic diagram of another embodiment of a gas flow measurement device according to the present invention.
Detailed Description
Various exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise.
Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description.
The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.
Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.
The terms "first", "second", and the like are used hereinafter only for descriptive distinction and have no other special meaning.
MEMS (micro electro Mechanical systems) is a micro-electromechanical system, is a technology for designing, processing, manufacturing, measuring and controlling micro/nano materials by utilizing a micro/nano technology basis, relates to various subjects and technologies such as electronics, machinery, materials, physics, chemistry, biology, medicine and the like, and has wide application prospect.
MEMS-based gas mass flowmeters have the characteristics of miniaturization and integration, low energy consumption, low cost, and have the additional advantage of fast response times, typically up to within 100 milliseconds. MEMS flow meters also have significant disadvantages compared to thermal gas mass flow meters, above all in terms of their performance, which is inferior to thermal flow meters in terms of accuracy, linearity and repeatability. In addition, common gases such as nitrogen and oxygen can be tested, and when special gases (CH4, Ar, SF6 and He) are tested, the accuracy is greatly reduced.
The MFM adopts a thermal sensor, the thermal flow sensor is based on the capillary heat transfer temperature difference calorimetry principle, thermistors are arranged on the upper and lower streams of a bridge of the sensor, and the thermistors are formed by winding sensing wires. When no gas passes through the sensing tube of the sensor, the upstream and downstream resistors of the Wheatstone bridge are equal, the output voltage signal is zero, when gas passes through the sensing tube, the gas brings the heat at the upstream of the sensing tube to the downstream, and the resistance value of the thermistor at the upstream and downstream of the sensing tube is changed by the change of the temperature at the upstream and downstream, so that the bridge can output the voltage signal related to the flow. The thermal MFM has the advantages of high accuracy, linearity, repeatability and reliability, and can be used for testing various gases.
Fig. 1 is a schematic flow chart of an embodiment of a gas flow measuring method according to the present invention, as shown in fig. 1:
And 102, determining the change state of the gas flow based on the first flow data and a preset state judgment rule.
And 103, if the change state is a slow change state, determining the data of the current gas flow based on the second flow data, and if the change state is a fast change state, obtaining the data of the current gas flow based on the first flow data and the conversion coefficient function.
And 104, if the conversion coefficient function needs to be corrected, correcting the conversion coefficient function based on the first flow data and the second flow data, and replacing the current conversion coefficient function with the obtained new conversion coefficient function.
The gas flow measuring method of the invention is provided with two flow sensors, namely a thermal flow sensor and an MEMS flow sensor, and can enable the two sensors to output equivalent signals when the flow changes little through parameter configuration. When the MEMS sensor detects that the flow changes rapidly, the signal of the MEMS sensor is used, so that the rapid response time of a product can be ensured; when the MEMS sensor detects that the flow change is small, the signal of the thermal sensor is used for automatically correcting the signal of the MEMS, so that the long-term accuracy, linearity, repeatability and special gas applicability of the product are ensured.
As shown in fig. 2, after entering the flow meter, the gas to be measured passes through the MEMS sensor and the thermal sensor in sequence, the driving circuit provides driving signals for the MEMS sensor and the thermal sensor, respectively, collects output signals of the two sensors, and transmits a flow signal to a user in the form of an electrical signal or a digital communication signal after calculation and correction.
As shown in figure 3, the flowmeter mainly comprises a 6-channel, a 5-shunt, a 3-air inlet joint, a 4-air outlet joint, a 2-MEMS sensor, a 7-thermal sensor and a 1-circuit board, wherein the gas to be measured passes through the MEMS sensor and the thermal sensor from the air inlet end to the air outlet end of a product in sequence. The MEMS sensor has no shunt and is installed in an insertion mode. The thermal sensor has a shunt, and a constant shunt ratio between the shunt and the thermal sensor is ensured by a mechanical structure.
The flowmeter has two signals of an MEMS sensor and a thermal sensor, according to the characteristics of the two sensors, the precision, the repeatability, the special gas adaptability and the long-term stability of the thermal sensor are superior to those of the MEMS sensor, but the response time of the thermal sensor is much slower than that of the MEMS sensor, so that the thermal sensor compensates for the deficiency of the MEMS sensor by switching between the two sensor signals and correcting the precision of the MEMS sensor by the thermal sensor.
In one embodiment, first flow calibration data collected by a MEMS sensor and second flow calibration data collected by a thermal flow sensor corresponding to a plurality of flow points are obtained in advance. Calculating the ratio of the first flow calibration data to the corresponding second flow calibration data to obtain a plurality of calibration point data, wherein the abscissa of the calibration point is a flow point, and the ordinate is the ratio corresponding to the flow point; performing curve fitting on the data of the plurality of calibration points by adopting a polynomial fitting method to obtain f0(x)。
The method is characterized in that an output flow signal of an MEMS sensor is set to be M, an output flow signal of a thermal sensor is set to be T, T is approximately equal to f (x) M when a product leaves a factory through calibration, f (x) is a conversion coefficient function between the F (x) and the M, x represents the flow size and takes the value from 0 to Full-Scale flow, and in the variation range of x, the difference value between T and M is smaller than 0.1% FS (Full Scale, Full-Scale flow, FS for short), which is achieved through configuration and calibration of hardware circuits of two sensors. At this time, the f (x) function is approximated to a straight line having a slope of 1.
In the process of calibrating the flowmeter, gas with different sizes in the full range of the flowmeter is introduced, a plurality of points of x and f (x) can be obtained by reading the reading between a calibrated product and a standard device, and then the function of f (x) is worked out by fitting mathematical algorithms such as a least square method, an interpolation method and the like.
The form of the function is f (x) anxn+an-1xn-1+…+a2x2+a1x+a0The higher the precision required by the product, the higher the value of n, a0～anIs a constant obtained by calibration.
For example, when n is 5, f (x) is a5x5+a4x4+a3x3+a2x2+a1x+a0(ii) a This function has 6 unknowns a0～a5The (x, f (x)) data of 6 points of 5% FS, 20% FS, 40% FS, 60% FS, 80% FS and 95% FS can be calculated by reading the reading between the calibrated product and the standard device, and six data can be used for solving six unknowns a0～a5Thus, the f (x) function is obtained when n is 5.
In one embodiment, N first flow data and N second flow data are sequentially obtained based on a preset time interval, and the MEMS sensor data array M and the thermal flow sensor data array T are respectively obtained, where N may be 5, 6, 7, and the like, and the preset time interval may be 1, 2, 3 seconds, and the like. Obtaining a difference value between the maximum element value and the minimum element value in M as a flow change value, judging whether the flow change value is larger than a preset first threshold value, if not, determining that the change state is a slow change state, and converting T into TThe last element value in (1) is used as the data of the current gas flow; if yes, determining the change state as a fast change state, and converting the initial conversion coefficient function f0(x) As a function f of the current conversion coefficient1(x) And taking the product of the last element value in M and the current conversion coefficient function as the data of the current gas flow.
There are various methods for correcting the conversion coefficient function based on the first traffic data and the second traffic data. For example, it is determined whether the flow rate variation value is less than or equal to a preset second threshold value, and if so, the average value of all elements in T is calculated
And average of all elements in M
And records the current flow point x1. Judgment of
And
whether the absolute value of the difference is less than or equal to a third threshold value, and if not, a new index point data (x) is used1,
) Replacing abscissa data and x in a plurality of index point data1The closest index point data. Performing curve fitting on the newly obtained calibration point data by adopting a polynomial fitting method to obtain a new conversion coefficient function f2(x)。
F can be periodically modified based on the correction interval duration1(x) Such that f1(x) Approach f2(x) And make a judgment on
Whether it is less than or equal to the first threshold value, and if so, stopping periodically modifying f1(x) And using the parameters of f2(x) Substitution f1(x)。
After the operation of correcting the conversion coefficient function is performed, the latter element of M and T is assigned to the former element, and the shift processing is performed. Acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor based on a preset time interval, and assigning the first flow data and the second flow data to the last element of M and T respectively; and after assigning a value to the last element in M and T, executing the step of determining the change state of the gas flow based on the first flow data and a preset state judgment rule, and performing cyclic processing.
Fig. 4 is a schematic flow chart of another embodiment of the gas flow measuring method according to the present invention, as shown in fig. 4:
In step 403, the difference between the maximum value and the minimum value of the 10 data M0-M9 is obtained and is recorded as the flow rate variation value a.
A1 can be set according to the thermal sensor response time, typically 1 second for the faster thermal sensor, and 1 second for discernable 100% FS flow change, then 5 milliseconds for 0.5% FS change, i.e. if the 5 millisecond change exceeds 0.5% FS the thermal sensor will not track the recognition effectively, and if some margin is left, A1 may also take 0.4% FS.
And step 407, calling a DA function to output analog voltage, assigning the flow data to communication data, and sending the data to the upper computer if the upper computer has an instruction of acquiring the flow data.
In step 408, it is determined whether the traffic correction function enable bit b is 1, and if yes, the process proceeds to step 409. Whether to execute the traffic correction function is determined by judging the traffic correction function enable bit b (b is 1 initially).
Step 410 shifts the data of arrays T0-T9 and M0-M9, assigns the next element of the array to the previous element, T8 and M8 will be covered by T9 and M9, and so on, T0 and M0 will be covered by T1 and M1.
In step 411, data from both sensors is again collected at N intervals, and new data is assigned to T [9] and M [9 ]. Then, the process goes to step 403 to execute the program in a loop. The data of different sensors are switched by judging the speed of flow change, and the advantage of quick response of the MEMS sensor is fully utilized.
Fig. 5 is a schematic flow chart of flow correction in another embodiment of the gas flow measuring method according to the present invention, as shown in fig. 5:
For example, use (x)1，
) The point data is used as a new data point to replace the calculation f0(x) The flow point and x in the 6 points (x, f (x)) data of 5% FS, 20% FS, 40% FS, 60% FS, 80% FS, and 95% FS used in the above case was set to x1Calculating to obtain a new conversion coefficient function f at the closest point2(x)。
In step 505, the determination is made,
and if not, indicating that the sensor has larger drift compared with a product when leaving the factory, entering a step 506, determining that the sensor has a fault, and setting an alarm signal.
In step 507, a timer T1 is started to perform a specific calibration operation.
In one embodiment, if f is to be2(x) Direct assignment to f1(x) If the difference between the two is larger, the flow value measured by the client will generate obvious jump, and the solution is to adopt a gradual change mode to ensure that f is gradually changed1(x) Slowly changing, gradually approaching f2(x) In that respect The T1 timer period may be set to 10 minutes every 10 minutes f1(x) By varying one step S1, S1 may take 0.03%, etc., i.e., approach f2(x) And (5) one step. Fig. 6 is a schematic flow chart of a timer interrupt in another embodiment of the gas flow measuring method according to the present invention, as shown in fig. 6:
In step 606, the traffic correction function enable bit b is 0.
Continuing to turn on the T1 interrupt, the T1 interrupt will continue, approaching one step every 10 minutes, until
And (4) if the condition less than or equal to 0.1% FS is met, finishing the correction process, setting the enabling position b of the flow correction function to be 1, and starting a new round of correction. When the correction function is realized, the output flow can slowly and smoothly change, and the flow jump can not occur.
In one embodiment, as shown in FIG. 7, the present invention provides a gas flow measuring device 70 comprising: a data acquisition module 71, a state decision module 72, a data determination module 73, a function correction module 74, a function replacement module 75, a function presetting module 76, and a value assignment module 77.
The data acquisition module 71 acquires first flow data acquired by the MEMS sensor and second flow data acquired by the thermal flow sensor. The state decision module 72 determines a change state of the gas flow based on the first flow data and a preset state decision rule. If the change status is a slow change status, the data determination module 73 determines data of the current gas flow based on the second flow data; if the change status is a fast change status, the data determination module 73 obtains data of the current gas flow based on the first flow data and the conversion coefficient function. The function correction module 74 performs correction processing on the conversion coefficient function based on the first flow volume data and the second flow volume data if it is determined that correction of the conversion coefficient function is required. The function replacement module 75 replaces the current conversion coefficient function with the obtained new conversion coefficient function.
In one embodiment, the data acquisition module 71 sequentially obtains N first flow data and N second flow data based on a preset time interval, and obtains an MEMS sensor data array M and a thermal flow sensor data array T, respectively. The state decision module 72 obtains a difference value between the maximum element value and the minimum element value in M as a flow rate change value, and determines whether the flow rate change value is greater than a preset first threshold value, if so, the change state is determined to be a fast change state, and if not, the change state is determined to be a slow change state. The data determination module 73 takes the last element value in T as the data of the current gas flow if it is determined that the change state is the slow change state, and converts the initial conversion coefficient function f to the fast change state0(x) As a function f of the current conversion coefficient1(x) And taking the product of the last element value in M and the current conversion coefficient function as the data of the current gas flow.
The function presetting module 76 obtains in advance first flow calibration data collected by the MEMS sensor and second flow calibration data collected by the thermal flow sensor corresponding to a plurality of flow points. Function presettingThe module 76 calculates a ratio of the first flow calibration data to the corresponding second flow calibration data to obtain a plurality of calibration point data, wherein the abscissa of the calibration point is the flow point and the ordinate is the ratio corresponding to the flow point. The function presetting module 76 performs curve fitting on the plurality of calibration point data by adopting a polynomial fitting method to obtain f0(x)。
The function correction module 74 determines whether the flow variation value is less than or equal to a preset second threshold value, and if so, calculates the average value of all elements in T
And average of all elements in M
And records the current flow point x1. Function correction module 74 determines
And
whether the absolute value of the difference is less than or equal to a third threshold value, and if not, a new index point data (x) is used1，
) Replacing abscissa data and x in a plurality of index point data1The closest index point data. The function correction module 74 performs curve fitting on the newly obtained calibration point data by using a polynomial fitting method to obtain a new conversion coefficient function f2(x)。
Function replacement module 76 periodically modifies f based on the correction interval duration1(x) Such that f1(x) Approach f2(x) And make a judgment on
Whether it is less than or equal to the first threshold value, and if so, stopping periodically modifying f1(x) And using the parameters of f2(x) Substitution f1(x)。
The data assignment module 77 assigns the latter element of M and T to the former element, performs displacement processing, and acquires a first flow data acquired by the MEMS sensor and a second flow data acquired by the thermal flow sensor based on a preset time interval; assigning the first traffic data and the second traffic data to the last element of M and T, respectively; wherein, after assigning to the last element of M and T, the state decision module 72 performs a step of determining a change state of the gas flow based on the first flow data and a preset state decision rule, and performs a loop process.
In one embodiment, the present invention provides a control system comprising: a gas flow measuring device as in any one of the above embodiments.
In one embodiment, the invention provides a gas mass flow meter comprising a control system as above.
FIG. 8 is a block schematic diagram of another embodiment of a gas flow measurement device according to the present disclosure. As shown in fig. 8, the apparatus may include a memory 81, a processor 82, a communication interface 83, and a bus 84. The memory 81 is used for storing instructions, the processor 82 is coupled to the memory 81, and the processor 82 is configured to execute the gas flow measurement method described above based on the instructions stored by the memory 81.
The memory 81 may be a high-speed RAM memory, a non-volatile memory (non-volatile memory), or the like, and the memory 81 may be a memory array. The storage 81 may also be partitioned and the blocks may be combined into virtual volumes according to certain rules. The processor 82 may be a central processing unit CPU, or an application Specific Integrated circuit asic, or one or more Integrated circuits configured to implement the gas flow measurement method of the present disclosure.
In one embodiment, the present disclosure provides a computer readable storage medium storing computer instructions that, when executed by a processor, implement a gas flow measurement method as in any of the above embodiments.
According to the gas flow measuring method, the gas flow measuring device, the control system, the gas mass flowmeter and the storage medium, the thermal flow sensor and the MEMS flow sensor are configured on the flowmeter, data of different sensors are switched by judging the speed of flow change, and the advantage of fast response of the MEMS sensors can be fully utilized; the accuracy of the MEMS is corrected by using the thermal sensor data through a self-correction method of the flowmeter, the long-term accuracy, the linearity, the repeatability and the special gas applicability of a product can be ensured, and the data cannot be mutated during correction; the flow testing precision is improved, and the working efficiency is improved.
The method and system of the present invention may be implemented in a number of ways. For example, the methods and systems of the present invention may be implemented in software, hardware, firmware, or any combination of software, hardware, and firmware. The above-described order for the steps of the method is for illustrative purposes only, and the steps of the method of the present invention are not limited to the order specifically described above unless specifically indicated otherwise. Furthermore, in some embodiments, the present invention may also be embodied as a program recorded in a recording medium, the program including machine-readable instructions for implementing a method according to the present invention. Thus, the present invention also covers a recording medium storing a program for executing the method according to the present invention.
The description of the present invention has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to practitioners skilled in this art. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.
Claims (16)
1. A method of measuring a gas flow, comprising: acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor; determining a change state of the gas flow based on the first flow data and a preset state judgment rule; determining data of a current gas flow rate based on the second flow rate data if the change status is a slow change status; if the change state is a fast change state, obtaining data of the current gas flow based on the first flow data and a conversion coefficient function; and if the conversion coefficient function needs to be corrected, correcting the conversion coefficient function based on the first flow data and the second flow data, and replacing the current conversion coefficient function with the obtained new conversion coefficient function, wherein the preset state judgment rule is implemented to determine data of the current gas flow between the second flow and the data of the current gas flow obtained based on the first flow data and the conversion coefficient function based on the speed of the change state.
2. The method of claim 1, further comprising: sequentially obtaining N first flow data and N second flow data based on a preset time interval, and respectively obtaining an MEMS sensor data array M and a thermal flow sensor data array T; obtaining a difference value between the maximum element value and the minimum element value in the M, taking the difference value as a flow change value, and judging whether the flow change value is larger than a preset first threshold value or not; if yes, determining that the change state is a fast change state, taking an initial conversion coefficient function f0(x) as a current conversion coefficient function f1(x), and taking the product of the last element value in the M and the current conversion coefficient function as data of the current gas flow; if not, determining that the change state is a slow change state, and taking the last element value in the T as the data of the current gas flow.
3. The method of claim 2, further comprising: acquiring first flow calibration data acquired by an MEMS sensor and second flow calibration data acquired by a thermal flow sensor corresponding to a plurality of flow points in advance; calculating the ratio of the first flow calibration data to the corresponding second flow calibration data to obtain a plurality of calibration point data, wherein the abscissa of the calibration point is a flow point, and the ordinate is the ratio corresponding to the flow point; performing curve fitting on the plurality of calibration point data by using a polynomial fitting method to obtain the f0 (x).
4. The method of claim 3, wherein correcting the conversion coefficient function based on the first flow data and the second flow data comprises: judging whether the flow change value is smaller than or equal to a preset second threshold value or not; if yes, calculating the average value of all elements in the T and the average value of all elements in the M and recording the current flow point x 1; judging whether the absolute value of the difference between the two is less than or equal to a third threshold value, if not, replacing the index point data which is closest to the current flow point x1 by using a new index point data; and performing curve fitting on the newly obtained calibration point data by adopting a polynomial fitting method to obtain a new conversion coefficient function f2 (x).
5. The method of claim 4, further comprising: periodically modifying the parameter of f1(x) based on the correction interval duration to make f1(x) approach f2(x), and judging whether the parameter is less than or equal to a first threshold value, if so, stopping periodically modifying the parameter of f1(x), and replacing f1(x) with f2 (x).
6. The method of claim 4, wherein a subsequent element of said M and said T is assigned to a previous element for shift processing; acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor based on a preset time interval; assigning the first traffic data and the second traffic data to the last element of said M and said T, respectively; and after assigning a value to the last element of M and T, executing the step of determining the change state of the gas flow based on the first flow data and a preset state judgment rule, and performing cyclic processing.
7. A gas flow measuring device, comprising: the data acquisition module is used for acquiring first flow data acquired by the MEMS sensor and second flow data acquired by the thermal flow sensor; the state judgment module is used for determining the change state of the gas flow based on the first flow data and a preset state judgment rule; a data determination module for determining data of a current gas flow based on the second flow data if the change status is a slow change status; if the change state is a fast change state, obtaining data of the current gas flow based on the first flow data and a conversion coefficient function; a function correction module, configured to, if it is determined that the conversion coefficient function needs to be corrected, perform correction processing on the conversion coefficient function based on the first flow data and the second flow data; and a function replacement module for replacing the current conversion coefficient function with the obtained new conversion coefficient function, wherein the preset state decision rule is implemented to determine data of the current gas flow between the second flow and the data of the current gas flow obtained based on the first flow data and the conversion coefficient function based on the speed of the change state.
8. The apparatus of claim 7, wherein the data acquisition module is configured to sequentially obtain N first flow data and N second flow data based on a preset time interval, and obtain a MEMS sensor data array M and a thermal flow sensor data array T, respectively; the state judgment module is used for obtaining a difference value between the maximum element value and the minimum element value in the M, using the difference value as a flow change value, and judging whether the flow change value is larger than a preset first threshold value; if yes, determining that the change state is a fast change state, and if not, determining that the change state is a slow change state; the data determination module is used for taking an initial conversion coefficient function f0(x) as a current conversion coefficient function f1(x) and taking the product of the last element value in the M and the current conversion coefficient function as the data of the current gas flow if the change state is determined to be a fast change state; and if the change state is determined to be a slow change state, taking the last element value in the T as the data of the current gas flow.
9. The apparatus of claim 8, further comprising: the function presetting module is used for obtaining first flow calibration data collected by the MEMS sensor and second flow calibration data collected by the thermal type flow sensor corresponding to the plurality of flow points in advance; calculating the ratio of the first flow calibration data to the corresponding second flow calibration data to obtain a plurality of calibration point data, wherein the abscissa of the calibration point is a flow point, and the ordinate is the ratio corresponding to the flow point; performing curve fitting on the plurality of calibration point data by using a polynomial fitting method to obtain the f0 (x).
10. The apparatus of claim 9, wherein the function correction module is configured to determine whether the flow rate variation value is less than or equal to a preset second threshold value; if yes, calculating the average value of all elements in the T and the average value of all elements in the M and recording the current flow point x 1; judging whether the absolute value of the difference between the two is less than or equal to a third threshold value, if not, replacing the index point data which is closest to the current flow point x1 by using a new index point data; and performing curve fitting on the newly obtained calibration point data by adopting a polynomial fitting method to obtain a new conversion coefficient function f2 (x).
11. The apparatus of claim 10, wherein the function replacement module is configured to periodically modify the parameter of f1(x) based on a correction interval duration such that f1(x) approaches f2(x), and determine whether the parameter is less than or equal to a first threshold, and if so, stop periodically modifying the parameter of f1(x), and replace f1(x) with f2 (x).
12. The apparatus of claim 10, wherein the data assigning module is configured to assign a subsequent element of M and T to a previous element for shift processing; acquiring first flow data acquired by an MEMS sensor and second flow data acquired by a thermal flow sensor based on a preset time interval; assigning the first traffic data and the second traffic data to the last element of said M and said T, respectively; after assigning a value to the last element of M and T, the state decision module performs the step of determining the change state of the gas flow based on the first flow data and a preset state decision rule, and performs a loop process.
13. A control system, comprising: a gas flow measuring device according to any one of claims 7 to 12.
14. A gas mass flow meter, comprising: the control system of claim 13.
15. A gas flow measurement device comprising: a memory; and a processor coupled to the memory, the processor configured to perform the method of any of claims 1-6 based on instructions stored in the memory.
16. A computer-readable storage medium having stored thereon computer instructions for execution by a processor of the method of any one of claims 1 to 6.
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