A self-cleaning and self-calibrating wind speed and direction sensor

Abstract

The application provides a self-cleaning and self-calibrating wind speed and direction sensor, a sensor chip is packaged in a central position of a central support, compressed air is sent to a surface of the sensor chip through setting of air inlet holes, air injection pipes and air injection ports and the like structures. The compressed air which is injected at a fixed time can clean the deposited particulate matters on the surface of the sensor chip, avoids the decrease of the measuring sensitivity of the sensor caused by the adhesion of the particulate matters, can continuously calibrate the output results of the sensor and eliminates the output drift of the sensor caused by the change of the ambient temperature. The ice and snow on the surface of the chip can be removed through blowing hot air, the abnormal work of the sensor caused by the ice and snow is solved and the environmental reliability of the work of the sensor is effectively improved.

Description

TECHNICAL FIELD

[0001] The present application is a self-cleaning and self-calibration wind speed and direction sensor structure, especially the compressed air sprayed through the air hole cleans the dust accumulated on the chip surface, and the compressed air flowing through the chip surface at a fixed flow rate can be used for sensor calibration. BACKGROUND

[0002] The measurement of wind speed and direction plays an important role in the fields of air transportation, energy conversion, meteorological research, construction and agriculture. Compared with the cup type and ultrasonic wind speed and direction sensor, the MEMS thermal type wind speed and direction sensor has no movable parts, has the advantages of small size and low power consumption, and has broad application prospects. The MEMS thermal type wind speed and direction sensor mainly measures the wind speed and direction through the convective heat transfer with the air. The sensor is affected by the air suspended particulate matter in the working environment, and dust accumulation phenomenon occurs on the chip surface, which affects the convective heat transfer between the chip and the air, and reduces the sensitivity of the sensor. With the change of the environmental temperature, the temperature gradient of heat transfer changes, which causes the drift of the zero point output of the sensor and also produces measurement error. In addition, the accumulated ice and snow on the chip surface in cold environment will make the sensor unable to work normally. Therefore, how to overcome the sensitivity reduction caused by dust, the abnormality of the sensor caused by ice and snow accumulation, and the zero point misalignment caused by temperature drift are the key problems to be solved. SUMMARY

[0003] The present application is a self-cleaning and self-calibration wind speed and direction sensor structure, especially the compressed air sprayed through the air hole cleans the dust accumulated on the chip surface, and the compressed air flowing through the chip surface at a fixed flow rate can be used for sensor calibration.

[0004] Technical scheme: The present application is a thermal type wind speed and direction sensor containing a jet port structure, which comprises an upper packaging plate, a lower packaging plate, a sensor chip, a central support, and a jet pipe. The upper packaging plate and the lower packaging plate are arranged in parallel. The central support is located between the upper packaging plate and the lower packaging plate and is arranged at the center of the lower packaging plate through support columns. The sensor chip is located on the upper surface of the central support. There is a gap between the sensor chip and the upper packaging plate. The jet pipe passes through the upper packaging plate, and the jet port of the jet pipe is located between the sensor chip and the upper packaging plate and faces the sensor chip. There are multiple jet pipes.

[0005] Further, the jet pipe comprises an air inlet section, a bending section, and an air outlet section connected in sequence. The air inlet section of the jet pipe passes through the upper and lower packaging plates, the air inlet port of the jet pipe is located below the lower packaging plate, the bending section of the jet pipe is located above the connection of the air outlet section, the air outlet section of the jet pipe passes through the upper packaging plate, and the air outlet port of the air outlet section faces the sensor chip.

[0006] The gas is sprayed to the center position of the sensor chip surface at a fixed angle, and all the air outlets are centrally symmetrically distributed; the compressed gas enters the air injection pipe through the air inlet, and is sprayed out through the air outlet after passing through the air inlet section, the bending section and the air outlet section of the air injection pipe.

[0007] Further, the distance between the sensor chip and the lower packaging plate is less than 1 / 2 of the distance between the upper packaging plate and the lower packaging plate.

[0008] Further, the sensor chip is a thermal type wind speed and direction sensor chip, comprising a heating resistor and four temperature measuring resistors; the four temperature measuring resistors are symmetrically distributed around the heating resistor.

[0009] The measurement value of the wind speed in the thermal temperature difference mode is calculated through the function relationship formula (1) .

[0010] (1)

[0011] Among them, is the temperature difference in the horizontal direction, is the temperature difference in the vertical direction .

[0012] The wind direction angle can be calculated through the inverse tangent function relationship formula (2) .

[0013] (2)

[0014] The self-calibration method of the wind speed and direction sensor of the application is based on the structure of the wind speed and direction sensor of the application, and the specific self-calibration method is as follows:

[0015] Step 1, set the flow rate of compressed air reaching the chip surface , the air outlets in each direction of the central symmetric distribution take turns to spray air to the chip surface, record the thermal loss mode measurement result output at this time and take as the calibration value to calibrate the wind speed measurement value of the thermal loss mode; record the thermal temperature difference mode measurement result at this time and substitute it into the relationship formula (1); similarly, take as the calibration value to calibrate the wind speed measurement value of the thermal temperature difference mode.

[0016] Step 2, record the temperature difference in the horizontal and vertical directions of the sensor at this time , and substitute it into the relationship formula (2), take the included angle between the current air outlet and the sensor direction as the wind direction calibration value, establish the corresponding relationship lookup table with the current wind direction calculation value, and realize the calibration of the wind direction measurement value.

[0017] Beneficial effects: 1) When the airflow with constant pressure is sprayed to the surface of the sensor chip, the particles adhered to the surface of the chip can be effectively removed, the formation of the particle thin layer is prevented, the influence of dust on the output of the sensor is eliminated, the self-cleaning of the sensor is realized, and the overall reliability of the sensor is improved; 2) The air jet port can be one or multiple and is centrally symmetrically distributed, the airflow is sprayed to the surface of the chip at a fixed flow rate in turn, according to the vector synthesis and decomposition, the flow rate error caused by air flow can be eliminated at the same time, the wind speed and direction measurement values are calibrated, and the self-calibration of the sensor is realized; 3) In the icing and snow environment, hot air can be blown to melt ice and snow, and the sensor can be accelerated to restore normal work; 4) In addition to conducting compressed air, the air jet pipe can also have the effect of air flow regulation, when the number of air jet pipes reaches a certain degree, the turbulent flow in the air can be converted into laminar flow, and the measurement result is more accurate and stable. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a side view of the sensor chip of the present application;

[0019] Figure 2 is a cross-sectional view of the axial position in the overall structure of the present application;

[0020] Figure 3 is a schematic view of the MEMS thermal wind speed and direction sensor chip structure adopted by the present application.

[0021] Among them, 1 is the upper plate of the package, 2 is the air jet port, 3 is the air jet pipe, 4 is the lower plate of the package, 5 is the air inlet, 6 is the sensor chip, and 7 is the central support. DETAILED DESCRIPTION

[0022] The technical scheme of the present application will be described below in combination with the drawings and examples.

[0023] As shown in Figure 1 and Figure 2 , a self-cleaning and self-calibration wind speed and direction sensor of the present application comprises an upper plate of a package 1, a lower plate of a package 4, a sensor chip 6, a central support 7, and an air jet pipe 3.

[0024] The upper plate of the package 1 and the lower plate of the package 4 are arranged in parallel; the central support 7 is located between the upper plate of the package 1 and the lower plate of the package 4, and is arranged at the central position of the lower plate of the package 4 through a support column; the sensor chip 6 is embedded in the central position of the upper surface of the central support 7 through an adhesive gel, and the upper surface of the central support 7 is horizontal.

[0025] The air jet pipe 3 has multiple air jet pipes 3, and the air jet pipe 3 comprises an air inlet section, a bending section and an air outlet section connected in sequence;

[0026] The air inlet section of the air jet pipe passes through the upper and lower packaging plates, the air inlet 5 of the air jet pipe is located below the lower packaging plate 4, the bending section of the air jet pipe is located above the connection of the air outlet section, the air outlet section of the air jet pipe passes through the upper packaging plate 1, the air outlet 2 of the air outlet section faces the sensor chip 6, and the gas is sprayed at a fixed angle to the center position of the surface of the sensor chip 6, and all the air outlets 2 are centrally symmetrically distributed; the compressed gas enters the air jet pipe 3 through the air inlet 5, and is sprayed out through the air outlet 2 after passing through the air inlet section, the bending section and the air outlet section of the air jet pipe. The angle between the air inlet section of the air jet pipe and the upper packaging plate and the lower packaging plate 4 can be any angle greater than 0° or less than or equal to 90°.

[0027] The air inlet section of the air jet pipe transmits compressed gas while fixing the upper packaging plate 1 and the lower packaging plate of the packaging plate 1. The suspended particulate matter in the working environment is brought to the surface of the sensor chip 6 by air flow, and accumulates on the surface of the chip over time to form a thin layer of particulate matter, reducing the convective heat transfer coefficient of the chip and air. The heat carried away by the air blowing over the chip surface is less, the wind speed measurement value is smaller, and the measurement error is introduced, reducing the measurement sensitivity. When the temperature of the working environment changes, due to the small difference between the resistance temperature coefficients of the heating resistor and the environment temperature measuring resistor in the thermal type wind speed and direction sensor, and the small error of the parameters of the driving circuit elements, the zero output of the sensor deviates. This phenomenon is called thermal wind speed and direction sensor temperature drift. The compressed air is sprayed to the surface of the sensor chip 6 at a certain flow rate, the output voltage of the sensor is recorded, and the wind speed and direction calibration table of the sensor is modified, so that the output calibration of the sensor can be realized. In addition, the sensor output is calibrated in different directions in a short time, which can solve the problem of sensor misalignment caused by temperature drift, and can eliminate the influence of air flow change in the working environment on the calibration result.

[0028] As shown in Figure 3 , the sensor chip 6 is a MEMS thermal type wind speed and direction sensor chip, which includes a heating resistor and four temperature measuring resistors; the four temperature measuring resistors are symmetrically distributed around the heating resistor; when the MEMS thermal type wind speed and direction sensor chip works, the heating resistor is heated, and the resistance values of the two groups of temperature measuring resistors respectively represent the temperature difference in the horizontal and vertical directions.

[0029] There are usually two ways to measure wind speed, thermal loss type measurement and thermal temperature difference type measurement.

[0030] In the thermal loss type measurement method of wind speed, the heat carried away by the wind blowing through the heating resistor represents the measurement value of the wind speed ; in the thermal temperature difference measurement method, the temperature difference in the horizontal direction , the temperature difference in the vertical direction respectively represent the wind speed in the horizontal direction , the wind speed in the vertical direction , the measured value of the wind speed in the thermal temperature difference mode is calculated by the function relation (1) .

[0031] (1)

[0032] The measurement of the wind direction is obtained by the horizontal temperature difference and the vertical temperature difference , and the wind direction angle is calculated by the arctangent function relation (2) .

[0033] (2)

[0034] When the diameter of the air jet 2 is constant, the greater the pressure of the compressed air, the greater the flow rate, and the self-calibration method of the wind speed and direction sensor of the application comprises the following steps:

[0035] Step 1, set the flow rate of the compressed air to the chip surface , the air jet 2 in each direction is distributed symmetrically and rotates to the chip surface, records the thermal loss mode measurement result output at this time and calibrates the wind speed measurement value of the thermal loss mode with as the calibration value; record the thermal temperature difference mode measurement result at this time and substitute it into relation (1); similarly, calibrate the wind speed measurement value of the thermal temperature difference mode with as the calibration value.

[0036] Step 2, record the temperature difference of the sensor in the horizontal and vertical directions at this time , and substitute it into relation (2), take the included angle between the current air jet 2 and the sensor direction as the wind direction calibration value, establish a corresponding relationship lookup table with the current wind direction calculation value, and realize the calibration of the wind direction measurement value.

[0037] Each air jet 2 is distributed symmetrically and rotates in sequence to spray air as a calibration cycle, and this method can eliminate the influence of air flow in the environment on the calibration result, and record the average value of each measurement result of the sensor in a calibration cycle as the calibration result, that is, complete the self-calibration of the sensor.

[0038] The working process of the sensor self-cleaning is as follows: the period of compressed air cleaning is set by timing. The period of compressed air cleaning can be adjusted according to the particle concentration of the working environment. The higher the particle concentration, the easier it is for dust to deposit on the chip surface, and the higher the required cleaning frequency.

[0039] The air inlet 5 can be connected to compressed air, hot air, and other gases or liquids that can remove special contaminants on the chip surface. When the sensor works in a cold environment, ice and snow may accumulate on the surface of the sensor chip 6, the heat exchange between the sensor chip 6 and the air in the environment is blocked, and most of the heat generated by the heating element in the chip is absorbed by the ice and snow, which will cause the sensor to always output full scale, resulting in abnormal operation of the sensor. Hot air is blown into the air inlet 5 to the chip surface, which can accelerate the melting and evaporation of ice and snow on the surface of the sensor chip 6, so that the sensor can quickly return to normal working state.

[0040] The wind speed and direction sensor usually works in an outdoor environment, and the ambient temperature will change with time. In some areas, the temperature difference between day and night can be as high as 20 ℃. This temperature change has an impact on the heat loss wind speed measurement value, the thermal temperature difference wind speed measurement value, and the wind speed measurement value of the sensor, and the measured values of wind speed and direction deviate from the calibrated values. The method of spraying compressed air can recalibrate the wind speed and direction measurement values of the sensor, which can calibrate the output of the sensor.

Claims

1. A self-cleaning and self-calibrating wind speed and direction sensor, characterized in that, Includes upper packaging board, lower packaging board, sensor chip, central support, and jet pipe; The upper and lower packaging plates are arranged in parallel; the central support is located between the upper and lower packaging plates and is positioned at the center of the lower packaging plate via a support column; the sensor chip is located on the upper surface of the central support. There is a gap between the sensor chip and the package plate; The jet pipe passes through the package top plate, and the jet nozzle of the jet pipe is located between the sensor chip and the package top plate, and faces the sensor chip. The jet pipe consists of an inlet section, a bend section, and an outlet section connected in sequence. The air inlet section of the jet pipe passes through the upper and lower plates of the package. The air inlet of the jet pipe is located below the lower plate of the package. The bend section of the jet pipe is located above the outlet section. The outlet section of the jet pipe passes through the upper plate of the package, and the jet nozzle of the outlet section faces the sensor chip. The gas is injected at a fixed angle to the center of the sensor chip surface. All jet nozzles are centrally symmetrically distributed. Compressed gas enters the jet pipe through the air inlet, passes through the air inlet section, bend section, and outlet section of the jet pipe, and is ejected from the jet nozzle. The angle between the air inlet section of the jet pipe and the upper and lower plates of the package is any angle greater than 0° or less than or equal to 90°. There are multiple jet pipes; The sensor chip is a thermal wind speed and direction sensor chip, which includes a heating resistor and four temperature measuring resistors; the four temperature measuring resistors are symmetrically distributed around the heating resistor. The measured value of the wind speed in the thermal temperature difference mode is calculated by the functional relationship (1) ; （1） wherein is the temperature difference in the horizontal direction, is the temperature difference in the vertical direction ; The wind direction angle can be calculated by the inverse tangent function relationship (2) ; （2） The self-calibration method for wind speed and direction sensors is as follows: Step 1, set the flow rate of compressed air to the chip surface , the jet holes in each direction of the central symmetric distribution take turns to spray air to the chip surface, record the thermal loss pattern measurement results at this time and calibrate the wind speed measurement value of the thermal loss pattern with as the calibration value; record the thermal temperature difference pattern measurement results at this time and substitute them into the relationship formula (1); similarly, calibrate the wind speed measurement value of the thermal temperature difference pattern with as the calibration value; Step 2, record the temperature difference between horizontal and vertical directions of the sensor at this time , Substitute into equation (2) and take the angle between the current jet and the sensor direction as the wind vane calibration value to establish a corresponding relationship lookup table with the current wind direction calculation value to achieve calibration of the wind direction measurement value; Each jet nozzle is centrally symmetrically distributed, and jets are sequentially sprayed in turn as a calibration cycle. This method can eliminate the influence of airflow in the environment on the calibration results. The average value of each measurement result of the sensor in one calibration cycle is recorded as the calibration result, thus completing the self-calibration of the sensor. The sensor self-cleaning process is as follows: the compressed air cleaning cycle is set at regular intervals; the compressed air cleaning cycle is adjusted according to the particulate matter concentration in the working environment. The higher the particulate matter concentration, the easier it is for dust to accumulate on the chip surface, and the higher the required cleaning frequency.

2. The self-cleaning and self-calibrating wind speed and direction sensor according to claim 1, characterized in that, The distance between the sensor chip and the lower package is less than half the distance between the upper and lower package.

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