A thermal desorption drive control method for space atmospheric density detector

Abstract

The present application relates to the field of space atmospheric detection technology, specifically, to a thermal desorption drive control method for a space atmospheric density detector, including initial preheating of the space atmospheric density detector; after the preheating is completed, the space atmospheric density detector enters the atmospheric adsorption process; during the atmospheric adsorption process, the difference frequency value between the measurement frequency signal and the reference frequency signal of the space atmospheric density detector is compared with a set first threshold parameter; during the heating and desorption process, the difference frequency value between the measurement frequency signal and the reference frequency signal of the space atmospheric density detector is compared with a set second threshold parameter; after the space atmospheric density detector turns on the thin film electric heater, it will perform real-time temperature judgment. The present application has the characteristics of autonomous control during long-life operation on orbit, and the detector automatically judges the completion of the adsorption and desorption process of the gas molecules of the atmospheric density detector through the threshold parameters.

Description

Technical Field

[0001] The present application relates to the field of space atmosphere detection technology, and in particular to a thermal desorption drive control method for a space atmosphere density detector. Background Art

[0002] Ultra-low Earth orbit (defined in this application as 120-300 km) refers to the region of space beyond the atmosphere but below the orbital altitude of typical spacecraft. With the advancement of space technology and the deepening of space applications, ultra-low Earth orbit flight technology will become an emerging development direction in the aerospace field. At this altitude, the atmosphere is very thin, but compared to outer space, it contains a large number of gas molecules. Therefore, it is necessary to develop ultra-low Earth orbit space atmospheric density detectors for gas detection.

[0003] The basic principle of atmospheric density detection is to form a sensor by coating a molecular sieve adsorption film on a quartz crystal microbalance. When the detector enters orbit, the sensor adsorbs gas molecules. When the adsorption amount increases, the oscillation frequency of the quartz crystal microbalance will change accordingly. The atmospheric density can be detected through measurement and collection of the back-end electrical part. However, this sensor has a disadvantage that it can only adsorb once, and the adsorbed gas molecules will reach a saturated state. Summary of the Invention

[0004] The thermal desorption drive control method for a space atmospheric density detector provided in the present application desorbs the gas adsorbed in the sensor by heating, thereby realizing cyclic detection.

[0005] In order to achieve the above-mentioned purpose, the present application provides a space atmospheric density detector thermal desorption drive control method, comprising the following steps: step 1: performing initial preheating on the space atmospheric density detector; step 2: after the preheating is completed, the space atmospheric density detector enters the atmospheric adsorption process; step 3: during the atmospheric adsorption process, comparing the difference frequency value between the measurement frequency signal of the space atmospheric density detector and the reference frequency signal with the set first threshold parameter; step 4: if the difference frequency value ≥ the first threshold parameter, then the space atmospheric density detector continues the atmospheric adsorption process; if the difference frequency value < the first threshold parameter, then the space atmospheric density detector enters the heating desorption process; step 5: during the heating desorption process, comparing the difference frequency value between the measurement frequency signal of the space atmospheric density detector and the reference frequency signal The value is compared with the set second threshold parameter; Step 6: If the difference frequency value ≤ the second threshold parameter, the space atmospheric density detector returns to step 2 and continues to enter the atmospheric adsorption process. If the difference frequency value is greater than the second threshold parameter, the thin film electric heater will be turned on during the heating and desorption process; Step 7: After the space atmospheric density detector turns on the thin film electric heater, it will make a real-time temperature judgment. If the real-time temperature is greater than 170°C, the space atmospheric density detector will turn off the thin film electric heater. If the real-time temperature is ≤170°C, the real-time temperature will continue to be judged; Step 8: If the real-time temperature is greater than 165°C, the space atmospheric density detector will turn off the thin film electric heater. If the real-time temperature is ≤165°C, it will return to step 5 and re-compare the difference frequency value with the second threshold parameter.

[0006] Furthermore, the space atmospheric density detector includes a quartz crystal microbalance sensor, an oscillation circuit, an FPGA digital signal operation circuit, a heating drive control circuit, a temperature sensor, a temperature measurement circuit and a thin film electric heater, wherein: the quartz crystal microbalance sensor includes a measuring quartz crystal microbalance sensor and a reference quartz crystal microbalance sensor; the oscillation circuit includes a measuring oscillation circuit and a reference oscillation circuit; the thin film electric heater is covered on the quartz crystal microbalance sensor; the measuring quartz crystal microbalance sensor is connected to the FPGA digital signal operation circuit through the measuring oscillation circuit to output a measuring frequency signal; the reference quartz crystal microbalance sensor is connected to the FPGA digital signal operation circuit through the reference oscillation circuit to output a measuring frequency signal The circuit is connected to the FPGA digital signal operation circuit to output a reference frequency signal; the temperature sensor is connected to the FPGA digital signal operation circuit through the temperature measurement circuit to output a real-time temperature signal; the FPGA digital signal operation circuit is connected to the thin film electric heater through the heating drive control circuit; the FPGA digital signal operation circuit is used to couple and transform the output measurement frequency signal and the output reference frequency signal, and perform a difference operation on the two signals to obtain a difference frequency value, and then judge and compare the difference frequency value, the set threshold parameter and the real-time temperature signal, and control the opening and closing of the thin film electric heater through the heating drive control circuit according to the comparison result.

[0007] Furthermore, the thin film electric heater is a polyimide thin film electric heater with a rated power of 15W, a rated temperature of 230°C, and a maximum heating temperature of 170°C.

[0008] Furthermore, the heating drive control circuit is directly connected to the thin film electric heater through the primary bus bar, and is used to control the opening and closing of the thin film electric heater.

[0009] Furthermore, in step 1, the heating time for the initial preheating of the space atmospheric density detector is fixed.

[0010] Furthermore, in step 3, the difference frequency value is an effective difference frequency value obtained after digital filtering and smoothing filtering by the FPGA digital signal operation circuit.

[0011] Furthermore, the first threshold parameter and the second threshold parameter are set in the FPGA digital signal operation circuit, and can be modified on-orbit by uploading them to the ground software.

[0012] The present invention provides a method for controlling thermal desorption of a space atmospheric density detector, which has the following beneficial effects:

[0013] The present application has the characteristics of autonomous control during long-life operation in orbit. The detector automatically judges the adsorption and desorption process of the atmospheric density detector gas molecules through threshold parameters. Temperature monitoring and judgment are added in the desorption mode, which can prevent the desorption time from being too long and causing the temperature to be too high and damage the polyimide film electric heater. The heating drive control circuit does not go through the secondary DC / DC circuit conversion, which can effectively reduce the power consumption, volume and weight of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings that constitute part of this application are used to provide a further understanding of this application and make other features, objects and advantages of this application more apparent. The illustrative embodiment drawings of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0015] Figure 1 1 is a flow chart of a thermal desorption drive control method for a space atmospheric density detector provided in an embodiment of the present application;

[0016] Figure 2 1 is a schematic structural diagram of a space atmospheric density detector provided according to an embodiment of the present application;

[0017] Figure 3 Schematic diagram of a heating drive control circuit provided according to an embodiment of the present application. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0019] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0020] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "center," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe this application and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0021] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in this application based on the specific circumstances.

[0022] Additionally, the term "plurality" shall mean two or more.

[0023] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0024] like Figure 1As shown, the present application provides a thermal desorption drive control method for a space atmospheric density detector, comprising the following steps: Step 1: performing initial preheating on the space atmospheric density detector; Step 2: after the preheating is completed, the space atmospheric density detector enters the atmospheric adsorption process; Step 3: during the atmospheric adsorption process, the difference frequency value Δf between the measurement frequency signal and the reference frequency signal of the space atmospheric density detector is compared with a set first threshold parameter fL; Step 4: if the difference frequency value Δf ≥ the first threshold parameter f L , then the space atmospheric density detector continues the atmospheric adsorption process, if the difference frequency value Δf < the first threshold parameter f L , then the space atmospheric density detector enters the heating and desorption process; Step 5: During the heating and desorption process, the difference frequency value Δf between the measurement frequency signal of the space atmospheric density detector and the reference frequency signal is compared with the set second threshold parameter f H Compare; Step 6: If the difference frequency value Δf ≤ the second threshold parameter f H , then the space atmospheric density detector returns to step 2 and continues to enter the atmospheric adsorption process. If the difference frequency value Δf> the second threshold parameter f H , then during the heating and desorption process, the thin film electric heater will be turned on; Step 7: After the space atmospheric density detector turns on the thin film electric heater, it will perform real-time temperature judgment. If the real-time temperature T t >170℃, the space atmospheric density detector will turn off the thin film electric heater. If the real-time temperature T t ≤170℃, then continue to judge the real-time temperature; Step 8: If the real-time temperature T t >165℃, the space atmospheric density detector will turn off the thin film electric heater. If the real-time temperature T t If the temperature is less than or equal to 165°C, the process returns to step 5 and compares the difference frequency value with the second threshold parameter again.

[0025] Specifically, the thermal desorption drive control method for a space-based atmospheric density detector provided in the present embodiment features autonomous control during long-life on-orbit operation. It primarily utilizes an optocoupler to isolate the primary bus power supply from the secondary power supply of the heating drive control circuit, achieving stable heating control of the polyimide thin film electric heater. The overall method utilizes a dual-threshold automatic control method based on frequency and temperature to achieve on-orbit adsorption and desorption of gas molecules by the atmospheric density detector, effectively addressing the long-life detection requirements of the space-based atmospheric density detector, improving the atmospheric density adsorption and desorption efficiency, and reducing system power consumption. In the present embodiment, the difference frequency between the measured frequency signal and the reference frequency signal of the space-based atmospheric density detector is compared with a preset threshold parameter, the real-time collected temperature value, and the set temperature range of the thin film electric heater. Based on the comparison results, a heating control instruction sequence is output. The sequence signal undergoes signal amplification and isolation conversion in the heating drive circuit to control the gate of the MOSFET, thereby turning the thin film electric heater circuit on or off. The entire process is an open-loop control process. The heating control logic method in the present embodiment is essentially a frequency threshold comparison method, but temperature monitoring is added during the heating and desorption process to prevent excessively high temperatures caused by prolonged desorption time, which could damage the thin film electric heater.

[0026] Further, such as Figure 2 As shown, the space atmospheric density detector includes a quartz crystal microbalance (QCM) sensor, an oscillation circuit, an FPGA digital signal operation circuit, a heating drive control circuit, a temperature sensor, a temperature measurement circuit and a thin film electric heater, wherein: the quartz crystal microbalance (QCM) sensor includes a measuring quartz crystal microbalance sensor and a reference quartz crystal microbalance sensor; the oscillation circuit includes a measuring oscillation circuit and a reference oscillation circuit; the thin film electric heater is covered on the quartz crystal microbalance sensor; the measuring quartz crystal microbalance sensor is connected to the FPGA digital signal operation circuit through the measuring oscillation circuit to output a measuring frequency signal fm; the reference .... The reference oscillator circuit is connected to the FPGA digital signal operation circuit to output a reference frequency signal fr; the temperature sensor is connected to the FPGA digital signal operation circuit through the temperature measurement circuit to output a real-time temperature signal; the FPGA digital signal operation circuit is connected to the thin-film electric heater through the heating drive control circuit; the FPGA digital signal operation circuit is used to couple and transform the output measurement frequency signal and the output reference frequency signal, and perform a difference operation on the two signals to obtain a difference frequency value, and then judge and compare the difference frequency value, the set threshold parameter, and the real-time temperature signal. Based on the comparison result, the heating drive control circuit controls the opening and closing of the thin-film electric heater. Based on the existing space atmospheric density detector, the embodiment of the present application uses the FPGA digital signal operation circuit to collect the frequency signal f output by the measurement oscillator circuit. m, reference oscillation circuit output frequency signal f r After the difference frequency operation and filtering, the effective difference frequency data Δf=f r -f m , then the effective difference frequency data Δf is combined with the first threshold parameter f L and the second threshold parameter f H A comparative judgment is made. According to the logic of the above comparative judgment, the space atmospheric density detector can enter the atmospheric adsorption mode or the heating desorption mode. In the heating desorption mode, the opening and closing of the thin film electric heater can be controlled by judging the real-time temperature, thereby realizing the open-loop control of the heating desorption of the space atmospheric density detector, and desorbing the gas adsorbed in the sensor in time by heating, thereby realizing the cyclic detection of the detector.

[0027] Furthermore, the thin film electric heater is a polyimide film electric heater with a rated power of 15W, a rated temperature of 230°C, and a maximum heating temperature of 170°C. The polyimide film electric heater is flexible and can be wrapped around the cylindrical sensor. The heating temperature is also sufficient. According to actual application conditions, the adsorption film sensor of the space atmospheric density detector generally requires a heating temperature greater than 150°C to more efficiently remove adsorbed gas molecules. The rated temperature of the polyimide film electric heater is 230°C, but rapid heating in a vacuum will produce overshoot. Moreover, it has been verified in vacuum tests that the actual heating temperature cannot reach 230°C. Therefore, in the embodiment of the present application, according to the 74% power derating design, the maximum heating temperature of the polyimide film electric heater should be controlled at about 170°C. When performing temperature judgment, 165°C and 170°C are preferably used as temperature reference nodes, mainly to protect the polyimide electric heater and improve the desorption efficiency. Of course, other temperatures within the temperature range can also be selected as temperature reference nodes according to actual conditions.

[0028] Further, such as Figure 3 As shown, the heating drive control circuit is directly connected to the thin film electric heater through the primary bus to control the opening and closing of the thin film electric heater. The heating drive control circuit of the embodiment of the present application uses the primary bus to directly supply power to the thin film heater without converting through the secondary DC / DC circuit. This design can reduce power consumption, volume and weight. Since the heating command signal output by the FPGA is relative to the secondary ground, and the heater is connected in series to the primary bus loop, an optocoupler U1 is added to the circuit to isolate the primary and secondary grounds, which can effectively drive the execution of the heating process. In the circuit, the resistor R 11 Used for heating feedback status detection. When MOSFET T1 is turned on, R 11 The voltage drop is amplified and fed back to the FPGA as an on-orbit monitoring parameter. 11One end is connected to the primary bus ground, so R 11 The voltage is inverted and amplified by the transistor and then isolated by optocoupler U2. This ensures that the heating monitoring status signal input to the FPGA is not affected by the primary ground crosstalk. A high level of the FPGA heating control command signal can start heating the heater, and the monitoring status is high; a low level stops heating the heater, and the monitoring status is also low.

[0029] More specifically, Figure 3 As shown, in the implementation of this application, the heating drive control circuit is connected in a manner that resistors R1 and R2 are connected in series to divide the voltage to obtain V mid However, due to the influence of printed circuit board and other impedances, the actual R1 and R2 are 43kΩ and 1MΩ respectively. mid =6.75V, the heating command signal output by FPGA is inverted and amplified by transistor (Q1) and then input to the first port of optocoupler (U1). The second port of U1 is connected to ground through a 10kΩ resistor, and the fifth port of U1 is pulled up to V mid , U1's 4th port is connected to the primary bus ground; the output signal of the optocoupler U1 is input to the gate of the N-channel field effect transistor T1 after passing through the resistor R9, the drain of T1 is connected to one end of the thin film heater, and the other end of the thin film heater is connected to a set of parallel fuse tubes, and the left side of the fuse tube is connected to the primary bus +42V; a 0.5Ω power resistor R is connected in series between the source of T1 and the ground. 11 , R 11 The voltage drop of the series resistor R 12 Then it is input to the base of transistor T2, and the drain output voltage of T2 is input to the photoelectric coupler U2 of the next stage. R is connected in series between the second port of U2 and the primary bus ground. 15 The resistor is 10kΩ, and the 5th port of U2 is connected through a 200kΩ resistor R 16 Then it is pulled up to the secondary power supply VCC5, the 4th port of U2 is connected to the secondary digital ground, and C2 and C3 are filter capacitors.

[0030] Furthermore, in step 1, the initial preheating time for the space-based atmospheric density detector is fixed. Since the adsorption membrane is already saturated or nearly saturated during the detector's on-orbit power-up initialization, the fixed time is intended to ensure complete release of gas molecules. The initial preheating time is preferably 5-10 minutes.

[0031] Furthermore, in step 3, the difference frequency value is the effective difference frequency value obtained after digital filtering and smoothing filtering by the FPGA digital signal operation circuit. The difference frequency value is filtered mainly to filter out the wild value that appears during operation.

[0032] Furthermore, the first threshold parameter and the second threshold parameter are set in the FPGA digital signal operation circuit, and can be modified on-orbit by uploading the ground software. When the quartz crystal microbalance (QCM) sensor is working for a long time on-orbit, the atmospheric adsorption and desorption performance will also decrease due to fatigue loss. The threshold parameter value f H and f L It can be modified on-orbit by adding parameters to the ground software. The first threshold parameter f L and the second threshold parameter f H Calibration is achieved using ground-based calibration equipment. Two threshold parameter values are initially set in the FPGA. These values are then modified on the ground using software based on actual detection conditions during the detection process. On-orbit software modifications are only made to address sensor fatigue degradation later in the payload's lifespan and do not require frequent revisions.

[0033] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A thermal desorption drive control method for a space atmospheric density detector, characterized in that: The steps include: Step 1: Initially preheat the space atmospheric density detector; Step 2: After the preheating is completed, the space atmospheric density detector enters the atmospheric adsorption process; Step 3: During the atmospheric adsorption process, the difference frequency value between the measured frequency signal of the space atmospheric density detector and the reference frequency signal is compared with the set first threshold parameter; Step 4: If the difference frequency value is greater than or equal to the first threshold parameter, the space atmospheric density detector continues the atmospheric adsorption process; if the difference frequency value is less than the first threshold parameter, the space atmospheric density detector enters the heating desorption process; Step 5: During the heating and desorption process, the difference frequency value between the measured frequency signal of the space atmospheric density detector and the reference frequency signal is compared with the set second threshold parameter; Step 6: If the difference frequency value is less than or equal to the second threshold parameter, the space atmospheric density detector returns to step 2 and continues to enter the atmospheric adsorption process. If the difference frequency value is greater than the second threshold parameter, the thin film electric heater is turned on during the heating and desorption process. Step 7: After the space atmospheric density detector turns on the thin film electric heater, it will perform real-time temperature judgment. If the real-time temperature is greater than 170°C, the space atmospheric density detector will turn off the thin film electric heater. If the real-time temperature is less than or equal to 170°C, it will continue to judge the real-time temperature. Step 8: If the real-time temperature is greater than 165°C, the space atmospheric density detector will turn off the thin film electric heater. If the real-time temperature is less than or equal to 165°C, the process will return to step 5 and re-compare the difference frequency value with the second threshold parameter.

2. The thermal desorption drive control method of a space atmospheric density detector according to claim 1, characterized in that: The space atmospheric density detector includes a quartz crystal microbalance sensor, an oscillation circuit, an FPGA digital signal operation circuit, a heating drive control circuit, a temperature sensor, a temperature measurement circuit and a thin film electric heater, wherein: The quartz crystal microbalance sensor includes a measuring quartz crystal microbalance sensor and a reference quartz crystal microbalance sensor; The oscillation circuit includes a measurement oscillation circuit and a reference oscillation circuit; The thin film electric heater covers the quartz crystal microbalance sensor; The measuring quartz crystal microbalance sensor is connected to the FPGA digital signal operation circuit through the measuring oscillation circuit, and is used to output a measuring frequency signal; The reference quartz crystal microbalance sensor is connected to the FPGA digital signal operation circuit through the reference oscillation circuit, and is used to output a reference frequency signal; The temperature sensor is connected to the FPGA digital signal operation circuit through the temperature measurement circuit, and is used to output a real-time temperature signal; The FPGA digital signal operation circuit is connected to the thin film electric heater through the heating drive control circuit; The FPGA digital signal operation circuit is used to couple and transform the output measurement frequency signal and the output reference frequency signal, and perform a difference operation on the two signals to obtain a difference frequency value, and then judge and compare the difference frequency value, the set threshold parameter and the real-time temperature signal. According to the comparison result, the heating drive control circuit controls the opening and closing of the thin film electric heater.

3. The thermal desorption drive control method of a space atmospheric density detector according to claim 2, characterized in that: The thin film electric heater is a polyimide thin film electric heater with a rated power of 15W, a rated temperature of 230°C, and a maximum heating temperature of 170°C.

4. The thermal desorption drive control method for a space atmospheric density detector according to claim 3, characterized in that: The heating drive control circuit is directly connected to the thin film electric heater via a primary bus bar, and is used to control the opening and closing of the thin film electric heater.

5. The thermal desorption drive control method for a space atmospheric density detector according to claim 1, characterized in that: In step 1, the heating time for the initial preheating of the space-based atmospheric density detector is fixed.

6. The thermal desorption drive control method for a space atmospheric density detector according to claim 2, characterized in that: In step 3, the difference frequency value is an effective difference frequency value obtained after digital filtering and smoothing filtering by the FPGA digital signal operation circuit.

7. The thermal desorption drive control method for a space atmospheric density detector according to claim 1, characterized in that: The first threshold parameter and the second threshold parameter are set in the FPGA digital signal operation circuit, and can be modified on-orbit by uploading them into ground software.

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