Thermal distributed gas flow detection method and system based on CMOS sensor

Abstract

The application discloses a kind of heat distributed gas flow detection method and system based on CMOS sensor, method includes: real-time detection gas flow in gas passage based on CMOS sensor;Judge whether the gas flow of current time detected by CMOS sensor is greater than or equal to the gas flow detected at last time;If yes, then directly output the gas flow value detected at current time;Otherwise, calculate the average drop speed of gas flow from last time to current time;Based on the preset function, calculate the temperature distribution inertia factor corresponding to the average drop speed of gas flow, and output the difference between the gas flow value detected at current time and the temperature distribution inertia factor;Wherein, temperature distribution inertia factor is the difference between the gas flow detected by CMOS sensor at current time and the real gas flow in gas passage based on preset function calculation. Realize effectively improve the response speed when gas flow drops in CMOS sensor heat distributed measurement process.

Description

Technical Field

[0001] This invention relates to the field of flow detection technology, and more specifically, to a thermally distributed gas flow detection method and system based on a CMOS sensor. Background Technology

[0002] Since the continuous development of integrated circuit technology in the last century, CMOS (Complementary Metal Oxide Semiconductor) technology has also embarked on a path of rapid development. CMOS technology uses single-crystal silicon as a substrate to fabricate sensitive thin-film structures on it to achieve corresponding functions. The overall size is micro- and nano-sized, allowing for high integration, and it represents the future direction of sensor development. Compared with traditional flow sensors, CMOS flow sensors have advantages such as miniaturization, high precision, low power consumption, and fast response. Flow detection methods based on CMOS sensing technology mainly include three types: distributed, thermal pulse, and thermal loss. Among them, the thermal distributed detection method has the advantages of high sensitivity and wide measurement range, and is currently a key research direction in related industries, and is widely used in actual production.

[0003] A schematic diagram of an existing thermal distributed flow detection method based on CMOS sensing technology is shown below. Figure 1 As shown, the entire sensing structure includes upstream and downstream temperature-sensitive elements and a heating element. When the gas flow rate through the sensor is zero, the temperature field around the heating element is symmetrically distributed, and the signals from the upstream and downstream temperature-sensitive elements are equal. When a certain flow rate of gas passes through the sensor, the symmetry of the temperature field around the heating element is broken, the upstream temperature decreases, and the downstream temperature increases, creating a temperature difference between the upstream and downstream. The faster the gas flow rate, the greater the temperature difference, which is used to measure the current gas flow rate.

[0004] like Figure 2 As shown, existing technologies can quickly and accurately detect flow signals when the gas velocity increases in the positive direction. However, when the gas velocity decreases rapidly, the response time slows down due to the residual temperature in the surrounding medium material of the temperature-sensitive element. When a certain flow rate is continuously applied to the flow channel, the thermal distribution field changes, and the temperature at the downstream temperature-sensitive element rises. When the flow rate suddenly decreases, the thermal distribution field shrinks, but the temperature of the surrounding material downstream differs from the specific heat capacity of the gas. For a short period, the temperature of the surrounding material differs from the temperature of the gas flow, causing the detection signal to fail to quickly output the current true flow rate, thus slowing down the response time. Summary of the Invention

[0005] The purpose of this invention is to propose a thermally distributed gas flow detection method and system based on a CMOS sensor, which effectively improves the response speed when the gas flow rate decreases during the thermally distributed measurement process of the CMOS sensor.

[0006] To achieve the above objectives, this invention proposes a thermally distributed gas flow detection method based on a CMOS sensor. The CMOS sensor includes an upstream temperature-sensitive element, a heating element, and a downstream temperature-sensitive element sequentially disposed along the gas inlet direction within the gas channel. The detection method includes:

[0007] Gas flow rate in the gas channel is detected using a CMOS sensor;

[0008] Determine whether the gas flow rate detected by the CMOS sensor at the current moment is greater than or equal to the gas flow rate detected at the previous moment:

[0009] If so, the gas flow rate value detected at the current moment will be output directly;

[0010] Otherwise, calculate the average rate of decrease in gas flow from the previous moment to the current moment;

[0011] Based on a preset function, the temperature distribution inertia factor corresponding to the average decreasing rate of the gas flow rate is calculated, and the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor is output; wherein, the temperature distribution inertia factor is the difference between the gas flow rate detected by the CMOS sensor at the current moment and the actual gas flow rate in the gas channel, calculated based on the preset function.

[0012] Optionally, after calculating the average rate of decrease in gas flow rate from the previous moment to the current moment, the method further includes:

[0013] Determine whether the average rate of decrease in gas flow rate is greater than a set threshold:

[0014] If so, then execute the step of calculating the temperature distribution inertia factor corresponding to the average decrease rate of the gas flow rate based on the preset function, and outputting the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor;

[0015] Otherwise, directly output the gas flow rate value detected at the current moment.

[0016] Optionally, the set threshold is 5 slm / s.

[0017] Optionally, the average rate of decrease in gas flow rate is calculated using the following formula:

[0018] v (k-1)k =(q (k-1) -q k ) / t (k-1)k

[0019] Among them, v (k-1)k Let q be the average rate of decrease in gas flow rate from time k-1 to time k. (k-1)Let q be the gas flow rate detected by the CMOS sensor at time k-1. k Let t be the gas flow rate value detected by the CMOS sensor at time k. (k-1)k The interval between time k-1 and time k is given.

[0020] Optionally, the preset function is:

[0021] α k =f(v (k-1)k )

[0022] Among them, v (k-1)k Let α be the average rate of decrease in gas flow rate from time k-1 to time k. k For time k and v (k-1)k The corresponding temperature distribution inertia factor;

[0023] The preset function is based on least squares fitting (v) (k-1)k α k Experimental data were obtained.

[0024] The present invention also proposes a thermal distributed gas flow detection system based on a CMOS sensor, comprising: a CMOS sensor and a central processing unit connected to the CMOS sensor;

[0025] The CMOS sensor is used to detect the gas flow rate in the gas channel. The CMOS sensor includes an upstream temperature-sensitive element, a heating element, and a downstream temperature-sensitive element arranged sequentially in the gas channel along the gas inlet direction.

[0026] The central processing unit includes a data correction module, which is used for:

[0027] Determine whether the gas flow rate detected by the CMOS sensor at the current moment is greater than or equal to the gas flow rate detected at the previous moment:

[0028] If so, the gas flow rate value detected at the current moment will be output directly;

[0029] Otherwise, the average rate of decrease in gas flow rate from the previous moment to the current moment is calculated based on a preset function;

[0030] Calculate the temperature distribution inertia factor corresponding to the average decrease rate of the gas flow rate, and output the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor; wherein, the temperature distribution inertia factor is the difference between the gas flow rate detected by the CMOS sensor at the current moment and the actual gas flow rate in the gas channel, calculated based on the preset function.

[0031] Optionally, after calculating the average rate of decrease in gas flow from the previous moment to the current moment, the data correction module is further configured to:

[0032] Determine whether the average rate of decrease in gas flow rate is greater than a set threshold:

[0033] If so, the temperature distribution inertia factor corresponding to the average decrease rate of the gas flow rate is calculated based on the preset function, and the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor is output.

[0034] Otherwise, directly output the gas flow rate value detected at the current moment.

[0035] Optionally, the CMOS sensor further includes a constant power source, a signal differential module, and an A / D conversion module;

[0036] The constant power source is connected to the heating element and is used to control the heating power of the heating element;

[0037] The signal differential module is connected to the upstream temperature sensing element and the downstream temperature sensing element, and is used to obtain the voltage signal difference generated by the upstream temperature sensing element and the downstream temperature sensing element;

[0038] The A / D conversion module is connected to the signal differential module and is used to convert the voltage signal difference into a digital signal and send it to the central processing unit.

[0039] Optionally, the central processing unit further includes a data processing module, a clock interrupt module, a data storage module, and a control output module connected to the data correction module;

[0040] The data processing module is connected to the A / D conversion module and the data storage module. The data processing module is used to process the digital signal output by the A / D conversion module into gas flow information detected by the CMOS sensor, and send the gas flow information to the data storage module and the data correction module. The data storage module is used to store the gas flow information.

[0041] The clock interrupt module is used to send a clock signal to the data correction module. Whenever the clock signal is interrupted, the data correction module obtains the gas flow information detected at the current time from the data processing module, and at the same time obtains the gas flow information detected at the last clock signal interruption from the data storage module. After processing, the gas flow information is output through the control output module.

[0042] Optionally, it also includes a terminal display module and a terminal output interface, wherein the terminal display module and the terminal output interface are respectively connected to the control output module, the terminal display module is used to display the gas flow output result, and the terminal output interface is used to connect to external devices.

[0043] The beneficial effects of this invention are as follows:

[0044] This invention determines whether the gas flow rate detected by the CMOS sensor at the current moment is greater than or equal to the gas flow rate detected at the previous moment. If the gas flow rate has not decreased, the current gas flow rate value is directly output. If it has decreased, the average rate of decrease in gas flow rate from the previous moment to the current moment is calculated, and a temperature distribution inertia factor corresponding to the average rate of decrease in gas flow rate is calculated using a preset function. The difference between the current gas flow rate value and the temperature distribution inertia factor is output. This invention utilizes the temperature inertia characteristics of the medium material to introduce a temperature distribution inertia factor that represents the difference between the gas flow rate detected by the CMOS sensor at the current moment and the actual gas flow rate in the gas channel. When the gas flow rate decreases, the temperature distribution inertia factor corrects the current gas flow rate value monitored by the sensor, ensuring a fast response to output an accurate gas flow rate value. This effectively improves the problem of slow response time caused by temperature inertia factors when the flow rate changes from large to small during distributed measurement using traditional CMOS sensors.

[0045] The methods and systems of the present invention have other features and advantages that will be apparent from or will be set forth in detail in the accompanying drawings and following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0046] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally denote like parts.

[0047] Figure 1 A schematic diagram of an existing thermal distributed flow detection method based on CMOS sensing technology is shown.

[0048] Figure 2 A schematic diagram of temperature residue in an existing thermal distributed flow detection method based on CMOS sensing technology is shown.

[0049] Figure 3 A flowchart illustrating the steps of a thermally distributed gas flow detection method based on a CMOS sensor according to the present invention is shown.

[0050] Figure 4 A schematic diagram of the gas flow rate decrease process in a thermally distributed gas flow rate detection method based on a CMOS sensor according to an embodiment of the present invention is shown.

[0051] Figure 5 A flowchart illustrating the establishment of a functional model of temperature distribution inertia factor and average gas flow rate decrease rate in a thermally distributed gas flow detection method based on a CMOS sensor according to an embodiment of the present invention is shown.

[0052] Figure 6 A flowchart of a thermally distributed gas flow detection method based on a CMOS sensor, according to a specific example of the present invention, is shown.

[0053] Figure 7 A schematic diagram of a thermally distributed gas flow detection system based on a CMOS sensor according to an embodiment of the present invention is shown. Detailed Implementation

[0054] Existing technologies using distributed flow detection methods do not consider the impact of residual temperature distribution on sensor signals. When directly outputting the detection signal, the sensor's output flow rate may temporarily exceed the actual flow rate during a sharp drop, slowing down the response time. To further improve the sensor's response speed, the signal processing method for this scenario should be fully considered.

[0055] This invention provides a flow detection method and system based on a CMOS sensor. By utilizing the temperature inertia characteristics of the medium material and through software algorithms, it solves the problem of slow sensor response time caused by local temperature residue due to the rapid drop in gas flow rate in a short period of time in traditional CMOS sensor thermal distributed measurement methods.

[0056] The invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0057] Figure 3 A flowchart illustrating the steps of a thermally distributed gas flow detection method based on a CMOS sensor according to the present invention is shown. In this embodiment, the CMOS sensor includes an upstream temperature-sensitive element, a heating element, and a downstream temperature-sensitive element sequentially disposed in the gas channel along the gas inlet direction.

[0058] like Figure 3As shown, a thermally distributed gas flow detection method based on a CMOS sensor according to the present invention includes:

[0059] Step S101: Detect the gas flow rate in the gas channel based on a CMOS sensor (real-time or cyclic);

[0060] Step S102: Determine whether the gas flow rate detected by the CMOS sensor at the current moment is greater than or equal to the gas flow rate detected at the previous moment:

[0061] Step S103: If yes, then directly output the gas flow rate value detected by the sensor at the current moment;

[0062] Step S104: Otherwise, calculate the average rate of decrease in gas flow rate from the previous moment to the current moment;

[0063] Specifically, the average rate of decrease in gas flow can be calculated using the following formula:

[0064] v (k-1)k =(q (k-1) -q k ) / t (k-1)k

[0065] Among them, v (k-1)k Let q be the average rate of decrease in gas flow rate from time k-1 to time k. (k-1) Let q be the gas flow rate detected by the CMOS sensor at time k-1. k Let t be the gas flow rate value detected by the CMOS sensor at time k. (k-1)k The interval between time k-1 and time k is given.

[0066] Step S105: Calculate the temperature distribution inertia factor corresponding to the average decrease rate of gas flow rate based on a preset function, and output the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor; wherein, the temperature distribution inertia factor is the difference between the gas flow rate detected by the CMOS sensor at the current moment and the actual gas flow rate in the gas channel, calculated based on the preset function.

[0067] The preset function can be one of the following function models:

[0068] α k =f(v (k-1)k )

[0069] In the formula, v (k-1)k Let α be the average rate of decrease in gas flow rate from time k-1 to time k. k For time k and v (k-1)k The corresponding temperature distribution inertia factor;

[0070] The above function model can be based on least squares fitting (v(k-1)k α k The experimental data was obtained.

[0071] Specifically, the above function model can be established based on experimental test data. The establishment methods include:

[0072] The minimum time unit Δt is determined based on the gas flow experimental equipment, where Δt is the interval between adjacent moments;

[0073] The gas flow rate q corresponding to the starting time i of the selected gas flow rate decrease i And the gas flow rate q corresponding to the end time j of the gas flow rate decrease. j Let q j =0;

[0074] Select multiple different t ij , t ij Let t be the time from the start time i to the end time j of the process of decreasing gas flow rate. ij = (a+n)Δt, where n takes values ​​in the range [0-b], and a, n, b ∈ N+;

[0075] Based on the same initial gas flow rate, different t ij In an experiment where the gas flow rate decreases at a constant rate during the process, the difference between the gas flow rate value detected by the CMOS sensor and the actual value of the real gas flow rate is observed within each unit time Δt.

[0076] Find each distinct t ij The average difference between the gas flow rate value detected by the CMOS sensor and the actual gas flow rate value within each unit time Δt during the duration is denoted as the temperature distribution inertia factor α. Simultaneously, the average difference between the gas flow rate value detected by the CMOS sensor and the actual gas flow rate value within each unit time Δt during the duration is calculated. ij The average rate of decrease in flow rate v over a long period of time ij ;

[0077] Build v ij -α coordinate system, different t ij All (v) obtained from the experiment of uniformly decreasing gas flow rate over a long period of time ij , α) as coordinate point, with v ij Let α be the independent variable and α be the dependent variable. The function model is obtained by fitting the data using the least squares method.

[0078] In the experiment where the gas flow rate decreases at a constant rate, the gas flow rate is controlled by a flow control valve, and the actual gas flow rate value is obtained through the flow control valve.

[0079] Preferably, the method further includes the following step after step S104:

[0080] Step S106: Determine whether the average rate of decrease in gas flow rate is greater than a set threshold.

[0081] If so, proceed to step S105, calculate the temperature distribution inertia factor corresponding to the average decrease rate of gas flow rate based on the preset function, and output the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor.

[0082] Otherwise, proceed to step S103 and directly output the gas flow rate value detected at the current moment.

[0083] Preferably, the threshold is set to 5 slm / s.

[0084] By determining whether the average descent rate of the gas flow exceeds a set threshold, if it does, the temperature distribution inertia factor corresponding to the average descent rate of the gas flow is calculated, and the difference between the gas flow value detected at the current moment and the temperature distribution inertia factor is output. If it does not exceed the set threshold, the gas flow value detected at the current moment is directly output, which can save system expenses and improve system operating efficiency.

[0085] The method of the present invention will be further illustrated below with a specific example:

[0086] After a certain flow rate of gas passes through the gas channel, the material surrounding the downstream temperature-sensitive element and the sensor is simultaneously heated by the heating element. When the gas flow rate decreases rapidly for a short period, the material surrounding the heated temperature-sensitive element does not have time to cool down. At this point, the flow rate output by the sensor will be higher than the actual flow rate until the surrounding material cools down. The characteristic of a certain delay in the temperature change of the material surrounding the downstream temperature-sensitive element with the gas flow rate during this process is defined as the inertial characteristic of the temperature distribution. Due to the inertial characteristic of the temperature distribution, there is a certain difference between the measured flow rate and the actual flow rate at any given moment. The entire process of flow rate reduction involves two variables: the initial flow rate, the final flow rate, and the average rate of flow rate reduction from the beginning to the end.

[0087] A schematic diagram of flow measurement when flow rate decreases is shown below. Figure 4 As shown, the solid curve represents the flow rate measured by the sensor, and the dashed curve represents the actual flow rate. t i t represents the starting time of the flow decrease. j t represents the end of the flow rate decrease. i t j The flow rates at each time point are q i q j Traffic from t i The time starts to decrease, until t j The time interval ends, but due to the inertia of temperature distribution, the actual flow rate will be less than t. j The descent process has already ended at time t. ito t j At any given time k (k = i, i+1, i+2, ..., j-2, j-1, j), the measured flow rate q k Compared to real traffic q k There is a certain difference between them, which can be represented by the temperature distribution inertia factor α, and we can obtain:

[0088] α=q k ―q k ' (1)

[0089] Define t ij Let q be the time elapsed from time i to time j, and q i >q j Then the average descent rate from time i to time j is

[0090] v ij =(q i -q j ) / t ij (2)

[0091] According to the inertial characteristics of temperature distribution, (q i -q j The larger the value of ), the better. ij The smaller v is ij The larger the value of v, the larger the temperature distribution inertia factor α, which reflects the severity of the flow rate decrease. During the flow rate decrease, v is not a constant value; α also changes with v at each moment. Taking time k as an example, then...

[0092] v (k-1)k =(q (k-1) -q k ) / t (k-1)k (3)

[0093] Since α is closely related to many parameters such as the material and size of the specific sensor, it is necessary to establish a functional model f of α with respect to v through experimental and test data:

[0094] α k =f(v (k-1)k (4)

[0095] The model calculates α at time k. k , then q k '≈Final output flow rate = q k -α k .

[0096] like Figure 5 As shown, the specific implementation plan for establishing the model of function f is as follows:

[0097] The smallest unit of time, t, is determined based on the experimental equipment.(k-1)k Let the elapsed time be Δt; then select q. i With q j , generally q j Set to 0, q i Larger resolution is better; select multiple t ij That is, the time from the start to the end of the flow reduction process, t ij The length increases sequentially from a Δt units to a+b Δt units (a, b∈N+, b>a). The difference between the sensor measurement and the true value is observed within each unit time Δt, and the average value is recorded as α.

[0098] Through the above process, a set of (v) can be obtained. ij Let α be a point in a two-dimensional plane formed by coordinates v. ij With α as the independent variable and α as the dependent variable, the least squares method is used for fitting, ultimately yielding α = f(v). ij In actual measurement, real-time flow correction is implemented, and the output flow value at the current moment is only related to the average rate of decrease of the previous unit time Δt. Introducing the current time k, then α k =f(v (k-1)k ).

[0099] A specific implementation plan for establishing the model of function f is as follows:

[0100] The initial gas flow rate is controlled at 10 slm. The braking flow control valve is closed at a uniform speed. The braking start-to-close time is set to 50 ms, 100 ms, ..., 2000 ms, respectively. A reading is taken every 50 ms to obtain standard measurement data and sensor output data. After each braking process, the average difference α between the standard measurement data and the sensor output data, as well as the average rate of flow rate decrease v during the entire braking process, are output. ij For example, the average velocities are respectively: 10slm / 50ms, 10slm / 100ms, ..., 10slm / 2000ms, constructing coordinate points (v). ij Using the least squares method to fit the data, the final function model α=f(v) is obtained. ij ).

[0101] Furthermore, such as Figure 6 As shown, the specific method for thermally distributed gas flow monitoring based on a CMOS sensor in this example is as follows:

[0102] The gas flow rate in the gas channel is detected in real time using a CMOS sensor;

[0103] Determine the current flow rate q detected by the sensor at time k. k Is it greater than or equal to the gas flow rate q at the previous time k-1? (k-1)If so, then directly output the current gas flow rate value q. k Otherwise, calculate v using formula (3). (k-1)k ;

[0104] Determine v (k-1)k If the value is greater than the set threshold β, then calculate the value of v based on the function model f of formula (4). (k-1)k Corresponding α k And output q according to formula (1) k With α k The difference q k ', q k 'The output result is the gas flow rate value.'

[0105] In this example, the threshold β is set based on empirical values. Preferably, when β > 5 slm / s, a relatively obvious response lag will occur. Therefore, temperature inertia correlation correction is only initiated and the corrected gas flow rate is output when the flow rate decreases to β; otherwise, the measured value is output directly. Introducing the threshold β can save system operating costs and improve operating efficiency.

[0106] like Figure 7 As shown, this embodiment of the invention also proposes a thermal distributed gas flow detection system based on a CMOS sensor, including: a CMOS sensor 1 and a central processing unit 2 connected to the CMOS sensor 1;

[0107] The CMOS sensor 1 is used to detect the gas flow rate in the gas channel. The CMOS sensor 1 includes an upstream temperature sensing element 101, a heating element 102 and a downstream temperature sensing element 103 arranged sequentially in the gas channel along the gas inlet direction.

[0108] Central processing unit 2 includes a data correction module 201, which is used for:

[0109] Determine whether the gas flow rate detected by CMOS sensor 1 at the current moment is greater than or equal to the gas flow rate detected at the previous moment:

[0110] If so, the gas flow rate value detected at the current moment will be output directly;

[0111] Otherwise, calculate the average rate of decrease in gas flow from the previous moment to the current moment;

[0112] The temperature distribution inertia factor corresponding to the average decrease rate of gas flow is calculated based on a preset function (function model f), and the difference between the gas flow value detected at the current moment and the temperature distribution inertia factor is output; wherein, the temperature distribution inertia factor is the difference between the gas flow detected by CMOS sensor 1 at the current moment and the actual gas flow in the gas channel, calculated based on the preset function.

[0113] Preferably, after calculating the average rate of decrease in gas flow rate from the previous moment to the current moment, the data correction module 201 is further configured to:

[0114] Determine if the average rate of decrease in gas flow exceeds a set threshold:

[0115] If so, the temperature distribution inertia factor corresponding to the average decrease rate of gas flow is calculated based on a preset function, and the difference between the gas flow value detected at the current moment and the temperature distribution inertia factor is output.

[0116] Otherwise, directly output the gas flow rate value detected at the current moment.

[0117] In this embodiment, the CMOS sensor 1 also includes a constant power source 104, a signal differential module 105, and an A / D conversion module 106;

[0118] The constant power source 104 is connected to the heating element 102 and is used to control the heating power of the heating element 102;

[0119] The signal differential module 105 is connected to the upstream temperature sensing element 101 and the downstream temperature sensing element 103, and is used to obtain the voltage signal difference generated by the upstream temperature sensing element 101 and the downstream temperature sensing element 103. Preferably, the difference can also be amplified.

[0120] The A / D conversion module 106 is connected to the signal differential module 105 and is used to convert the (amplified) voltage signal difference into a digital signal and send it to the central processing unit 2.

[0121] In this embodiment, the central processing unit 2 further includes a data processing module 202, a clock interrupt module 203, a data storage module 204, and a control output module 205 connected to the data correction module 201;

[0122] The data processing module 202 is connected to the A / D conversion module 106 and the data storage module 204. The data processing module 202 is used to process the digital signal output by the A / D conversion module 106 into gas flow information detected by the CMOS sensor 1, and send the gas flow information to the data storage module 204 and the data correction module 201. The data storage module 204 is used to store the gas flow information.

[0123] The clock interrupt module 203 is used to send a clock signal to the data correction module. Whenever the clock signal is interrupted, the data correction module 201 obtains the gas flow information detected at the current time from the data processing module 202, and at the same time obtains the gas flow information detected when the clock signal was interrupted from the data storage module 204. After processing, the gas flow information is output through the control output module 205.

[0124] In this embodiment, a terminal display module 206 and a terminal output interface 207 may also be included. The terminal display module 206 and the terminal output interface 207 are respectively connected to the control output module 205. The terminal display module 206 is used to display the gas flow output result, and the terminal output interface 207 is used to connect to external devices.

[0125] Specifically, the sensor is installed in the gas channel and is in direct contact with the airflow. The sensor heating element 102 is connected to the constant power source 104, and the upstream and downstream temperature sensing elements 103 are connected to the signal differential module 105. The signal is input to the A / D conversion module 106 after differential operation. The A / D conversion module 106 converts the original analog voltage signal of the sensor into a digital signal and sends it to the central processing unit 2. The central processing unit 2 is responsible for the optimization processing of the data and performs terminal control and output in the control output module 205. The logic structure of the central processing unit 2 can be divided into five main parts: data processing module 202, data correction module 201, clock interrupt module 203, data storage module 204, and control output module 205. The data processing module 202 processes the raw digital signal from the A / D conversion into flow information, i.e., the flow measured by the sensor. The current flow measurement information is sent to the data storage module 204 for buffering and to the data correction module 201 at the same time. Every time the clock is interrupted, the data correction module 201 obtains the current flow information from the data processing module 202 and the flow information at the time of the last interrupt from the data storage module 204. After processing, it outputs the final optimized flow information.

[0126] The data correction module 201 in the detection system of this embodiment mainly executes the relevant algorithms in steps S102-S106 of the above embodiment.

[0127] The following specific example illustrates the operation flow of the entire detection system:

[0128] CMOS sensor 1 is installed at the gas channel to directly contact the gas and measure the current gas flow rate in the channel. The differential signal detected by the sensor is amplified by differential operation through signal differential module 105, and then converted from analog to digital by A / D conversion module 106 before being sent to central processing unit 2. Data processing module 202 in central processing unit 2 converts the voltage differential digital signal into the corresponding gas flow rate detection value, and sends the most recent flow rate detection value and the gas flow rate detection value of the previous moment in data storage module 204 to data correction module 201. The specific time interval of each moment is related to the time interrupt time set by clock interrupt module 203. After the most recent flow rate detection value, the gas flow rate detection value of the previous moment, and the time interval are sent to data correction module 201, the corresponding temperature distribution inertia factor α can be obtained according to the above formulas (2) and (4). The final output flow rate value q after correction is obtained according to the above formula (1). k '.

[0129] The system of the present invention, by adding a data correction module 201 based on temperature distribution inertia correction, can correct and output measurement results in real time, thereby improving the accuracy and response speed of the measurement system.

[0130] In summary, this invention is based on the distributed measurement principle of CMOS flow sensors. Based on the temperature inertia characteristics of the medium material, it proposes the concept of temperature distribution inertia factor. By defining the temperature distribution inertia factor, the error between the output flow value and the actual flow value is adjusted, thereby improving the response time. This solves the problem of slow sensor response time caused by local temperature residue due to the rapid drop in gas velocity in a short period of time in traditional thermal distributed flow detection methods.

[0131] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for detecting thermally distributed gas flow rate based on a CMOS sensor, wherein the CMOS sensor comprises an upstream temperature-sensitive element, a heating element, and a downstream temperature-sensitive element sequentially disposed in a gas channel along the gas inlet direction, characterized in that, The detection method includes: The gas flow rate within the gas channel is detected using the CMOS sensor. Determine whether the gas flow rate detected by the CMOS sensor at the current moment is greater than or equal to the gas flow rate detected at the previous moment: If so, the gas flow rate value detected at the current moment will be output directly; Otherwise, calculate the average rate of decrease in gas flow from the previous moment to the current moment; The temperature distribution inertia factor corresponding to the average decrease rate of the gas flow rate is calculated based on a preset function, and the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor is output; wherein, the temperature distribution inertia factor is the difference between the gas flow rate detected by the CMOS sensor at the current moment and the actual gas flow rate in the gas channel, calculated based on the preset function. The preset function is: α k =f ( v (k-1)k ) in, v (k-1)k for k-1 Time to k The average rate of decrease in gas flow rate at any given time. α k for k Time and v (k-1)k The corresponding temperature distribution inertia factor; The preset function is based on least squares fitting ( v (k-1)k , α k Experimental data were obtained.

2. The detection method according to claim 1, characterized in that, The calculation of the average rate of decrease in gas flow rate from the previous moment to the current moment also includes: Determine whether the average rate of decrease in gas flow rate is greater than a set threshold: If so, then execute the step of calculating the temperature distribution inertia factor corresponding to the average decrease rate of the gas flow rate based on the preset function, and outputting the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor; Otherwise, directly output the gas flow rate value detected at the current moment.

3. The detection method according to claim 2, characterized in that, The set threshold is 5 slm / s.

4. The detection method according to claim 1, characterized in that, The average rate of decrease in gas flow rate is calculated using the following formula: v (k-1)k =(q (k-1) -q k ) / t (k-1)k in, v (k-1)k for k-1 Time to k The average rate of decrease in gas flow rate at time t. q (k-1) for k-1 The gas flow rate value detected by the CMOS sensor at any time. q k for k The gas flow rate value detected by the CMOS sensor at any time. t (k-1)k for k-1 Time to k The time interval between moments.

5. A thermally distributed gas flow detection system based on a CMOS sensor, characterized in that, Includes: a CMOS sensor and a central processing unit connected to the CMOS sensor; The CMOS sensor is used to detect the gas flow rate in the gas channel. The CMOS sensor includes an upstream temperature-sensitive element, a heating element, and a downstream temperature-sensitive element arranged sequentially in the gas channel along the gas inlet direction. The central processing unit includes a data correction module, which is used for: Determine whether the gas flow rate detected by the CMOS sensor at the current moment is greater than or equal to the gas flow rate detected at the previous moment: If so, the gas flow rate value detected at the current moment will be output directly; Otherwise, calculate the average rate of decrease in gas flow from the previous moment to the current moment; The temperature distribution inertia factor corresponding to the average decrease rate of the gas flow rate is calculated based on a preset function, and the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor is output; wherein, the temperature distribution inertia factor is the difference between the gas flow rate detected by the CMOS sensor at the current moment and the actual gas flow rate in the gas channel, calculated based on the preset function. The preset function is: α k =f ( v (k-1)k ) in, v (k-1)k for k-1 Time to k The average rate of decrease in gas flow rate at any given time. α k for k Time and v (k-1)k The corresponding temperature distribution inertia factor; The preset function is based on least squares fitting ( v (k-1)k , α k Experimental data were obtained.

6. The detection system according to claim 5, characterized in that, After calculating the average rate of decrease in gas flow from the previous moment to the current moment, the data correction module is further used for: Determine whether the average rate of decrease in gas flow rate is greater than a set threshold: If so, the temperature distribution inertia factor corresponding to the average decrease rate of the gas flow rate is calculated based on the preset function, and the difference between the gas flow rate value detected at the current moment and the temperature distribution inertia factor is output. Otherwise, directly output the gas flow rate value detected at the current moment.

7. The detection system according to claim 5, characterized in that, The CMOS sensor also includes a constant power source, a signal differential module, and an A / D conversion module; The constant power source is connected to the heating element and is used to control the heating power of the heating element; The signal differential module is connected to the upstream temperature sensing element and the downstream temperature sensing element, and is used to obtain the voltage signal difference generated by the upstream temperature sensing element and the downstream temperature sensing element; The A / D conversion module is connected to the signal differential module and is used to convert the voltage signal difference into a digital signal and send it to the central processing unit.

8. The detection system according to claim 7, characterized in that, The central processing unit also includes a data processing module, a clock interrupt module, a data storage module, and a control output module connected to the data correction module; The data processing module is connected to the A / D conversion module and the data storage module. The data processing module is used to process the digital signal output by the A / D conversion module into gas flow information detected by the CMOS sensor, and send the gas flow information to the data storage module and the data correction module. The data storage module is used to store the gas flow information. The clock interrupt module is used to send a clock signal to the data correction module. Whenever the clock signal is interrupted, the data correction module obtains the gas flow information detected at the current time from the data processing module, and at the same time obtains the gas flow information detected at the last clock signal interruption from the data storage module. After processing, the gas flow information is output through the control output module.

9. The detection system according to claim 8, characterized in that, It also includes a terminal display module and a terminal output interface. The terminal display module and the terminal output interface are respectively connected to the control output module. The terminal display module is used to display the gas flow output result, and the terminal output interface is used to connect to external devices.

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