Method for multichannel frequency acquisition of an air data system
By combining the STM32F407 chip and the SN74LV8154 external counter with a synchronous acquisition algorithm for low-frequency and high-frequency counters, the problems of accuracy and cost in multi-channel frequency acquisition of atmospheric data systems are solved, achieving high-precision and low-cost frequency acquisition and meeting the requirements for system miniaturization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN AVIATION INSTR
- Filing Date
- 2023-12-20
- Publication Date
- 2026-06-09
Smart Images
Figure CN117848576B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of atmospheric data and relates to a method for multi-channel frequency acquisition of atmospheric data systems. Background Technology
[0002] Atmospheric data sensing systems utilize arrays of pressure sensors installed on the nose, fuselage, and wings of aircraft to calculate total and static pressure by collecting data at various frequencies, and further interpret the atmospheric data. Atmospheric data systems have wide applications in industry, aviation, and aerospace.
[0003] The existing system uses F / D frequency acquisition modules to measure frequency. However, the highest frequency supported by the high-frequency counting clock of the F / D frequency acquisition chip is 12.8MHz, resulting in relatively low frequency measurement accuracy. Furthermore, when acquiring multiple channels, it requires multiple interfaces and multiple F / D modules, which is not economical. Summary of the Invention
[0004] The purpose of this invention is to provide a method for multi-channel frequency acquisition in an atmospheric data system. This invention can simultaneously acquire frequencies from eight channels to calculate pressures from four channels and report them to a higher-level system, featuring low cost, high precision, and high efficiency.
[0005] The technical solution of this invention is: a method for multi-channel frequency acquisition in an atmospheric data system, comprising an acquisition chip, an external counter, sensor 1, sensor 2, sensor 3, and sensor 4; the acquisition chip includes 8 low-frequency acquisition channels, of which 6 channels are equipped with 6 low-frequency acquisition timers, namely TIM1, TIM3, TIM4, TIM8, TIM9, and TIM12; the external counter includes channels CLKA and CLKB, which are connected to the remaining 2 channels of the acquisition chip; the pressure calculation frequency output channel fp1 of sensor 1 is connected to the low-frequency acquisition timer TIM4, and the temperature calculation frequency output channel ft1 of sensor 1 is connected to the low-frequency acquisition timer TIM3; the pressure calculation frequency output channel fp2 of sensor 2 is connected to the low-frequency acquisition timer TIM12, and the sensor… The temperature calculation frequency output channel ft2 of sensor 2 is connected to the low-frequency acquisition timer TIM8; the pressure calculation frequency output channel fp3 of sensor 3 is connected to channel CLKA, and the temperature calculation frequency output channel ft3 of sensor 3 is connected to the low-frequency acquisition timer TIM9; the pressure calculation frequency output channel fp4 of sensor 4 is connected to channel CLKB, and the temperature calculation frequency output channel ft4 of sensor 4 is connected to timer TIM1; the acquisition chip also includes two 4-channel high-frequency counters TIM5 and TIM2; the four channels of high-frequency counter TIM5 are respectively connected to low-frequency acquisition timers TIM4, TIM12 and channels CLKA, CLKB; the four channels of high-frequency counter TIM2 are respectively connected to low-frequency acquisition timers TIM3, TIM8, TIM9 and TIM1.
[0006] In the aforementioned multi-channel frequency acquisition system for atmospheric data, the acquisition chip is an STM32F407 chip.
[0007] In the aforementioned multi-channel frequency acquisition system for atmospheric data, the external counter is model SN74LV8154.
[0008] In the aforementioned multi-channel frequency acquisition system for atmospheric data, sensors 1, 2, 3, and 4 are all pressure-sensitive sensors.
[0009] A method for acquiring atmospheric data using a multi-channel frequency acquisition system as described above includes the following steps: Sensor 1 converts the acquired pressure signal into pressure frequency and temperature frequency signals, respectively, and inputs them to the low-frequency acquisition timers TIM4 and TIM3 of the acquisition chip via pressure calculation frequency output channel fp1 and temperature calculation frequency output channel ft1, respectively; Sensor 2 converts the acquired pressure signal into pressure frequency and temperature frequency signals, respectively, and inputs them to the low-frequency acquisition timers TIM12 and TIM8 of the acquisition chip via pressure calculation frequency output channel fp2 and temperature calculation frequency output channel ft2, respectively; Sensor 3 converts the acquired pressure signal into a pressure frequency signal and inputs it to the low-frequency acquisition timers TIM12 and TIM8 of the acquisition chip via pressure calculation frequency output channel ft2. The pressure sensor 3 inputs the pressure signal to an external counter via channel fp3, and then to the acquisition chip via channel CLKA of the external counter. Sensor 3 converts the acquired pressure signal into a temperature frequency signal, which is then input to the low-frequency acquisition timer TIM9 of the acquisition chip via temperature calculation frequency output channel ft3. Sensor 4 converts the acquired pressure signal into a pressure frequency signal, which is then input to an external counter via pressure calculation frequency output channel fp4, and then to the acquisition chip via channel CLKB of the external counter. Sensor 4 converts the acquired pressure signal into a temperature frequency signal, which is then input to the low-frequency acquisition timer TIM1 of the acquisition chip via temperature calculation frequency output channel ft4. Both the pressure frequency signal and the temperature frequency signal are low-frequency signals.
[0010] When the pressure frequency signals acquired by TIM2, TIM12, channel CLKA and channel CLKB have a rising edge, the corresponding channel of high frequency counter TIM5 is excited to capture the high frequency count value of its own high frequency signal.
[0011] When the temperature frequency signals acquired by TIM3, TIM8, TIM9, and TIM1 have a rising edge, the corresponding channel of the high-frequency counter TIM2 is excited to capture the high-frequency count value of its own high-frequency signal.
[0012] Synchronize the high-frequency count values captured in high-frequency counters TIM5 and TIM2 with the low-frequency count values acquired by the 8 low-frequency acquisition channels;
[0013] After synchronization, the measured frequency is calculated based on the changes in high and low frequency count values within the period.
[0014] In the aforementioned multi-channel frequency acquisition system for atmospheric data, the synchronization method is as follows: when the timer period expires, three consecutive low-frequency counts and high-frequency counts are sampled, the values of the three low-frequency counts are compared, and a set is selected for subsequent frequency calculation; the synchronization method for each channel is performed in accordance with the above.
[0015] In the aforementioned multi-channel frequency acquisition system for atmospheric data, the specific decision-making method is as follows: if the three sets of acquired data are the same, the second set of data is selected; if the latter two sets of data are the same, the third set of data is selected; and if the first two sets of data are the same, the first set of data is selected.
[0016] In the aforementioned multi-channel frequency acquisition system for atmospheric data, after synchronous counting, the measured frequency is calculated based on the high and low frequency count values. The calculation formula is as follows: Where f is the silicon resonant frequency (low frequency), Fs is the high-frequency clock frequency of the high-frequency counters TIM5 and TIM2, and n is the frequency of the high-frequency counters TIM5 and TIM2. i n is the initial low-frequency count value for this sampling period. i+1 N is the initial low-frequency count value for the next sampling period. i N is the initial high-frequency count value for this sampling period. i+1 This is the initial high-frequency count value for the next sampling period.
[0017] In the aforementioned method for acquiring atmospheric data using a multi-channel frequency acquisition system, the high-frequency clock frequency is set to 42MHz.
[0018] Beneficial effects:
[0019] This invention designs a synchronous acquisition algorithm for a single channel using a fixed-period method. By employing a redundant algorithm that involves three consecutive acquisitions of low-frequency counts followed by comparison and decision-making, synchronous acquisition of high and low frequencies is achieved, avoiding excessive low-frequency counting and improving acquisition reliability.
[0020] In this invention, the measured frequency is calculated by the change in the measured low-frequency count value and high-frequency count value within a fixed sampling period. If there is an error in the period, the period of the high-frequency and low-frequency counts is kept consistent.
[0021] 1. The accuracy error of the standard atmospheric pressure calculated by frequency in this invention is less than 10 Pa;
[0022] 2. This invention enables synchronous measurement of 8 external frequencies;
[0023] 3. This invention ensures that each frequency acquisition path is independent and does not affect the others;
[0024] 4. For a measured frequency of 40kHz, the highest accuracy error of this invention is 0.095Hz;
[0025] 5. This invention can achieve periodic real-time data acquisition, with a frequency of once every 10ms. The acquisition period can be adjusted according to actual requirements.
[0026] 6. This invention uses a method of multiple continuous acquisitions within a single cycle to adjudicate the multiple acquisition methods. The adjudicated data is used to calculate the frequency and subsequent pressure data, ensuring real-time performance and accuracy.
[0027] 7. This invention replaces traditional hardware modules for frequency acquisition with algorithm design, saving hardware costs and reducing weight, thus facilitating system miniaturization. Traditional frequency detection in this system requires four detection modules, each costing approximately 2600 yuan. Using this invention, at least 10400 yuan is effectively saved per product.
[0028] 8. This invention saves chip resources through software design, reduces the number of interfaces required by traditional detection modules by 12, and reduces power consumption by 60%.
[0029] 9. The accuracy is shown in Table 1. The traditional F / D detection module supports a maximum high-frequency clock of 12.8MHz. When the measured frequency is 40Hz, it cannot meet the requirements of subsequent pressure calculation. However, the present invention supports a maximum high-frequency clock of 168MHz, which improves the accuracy by 13.2 times and meets the requirements of subsequent pressure error.
[0030] Table 1
[0031]
[0032] In summary, this invention can simultaneously acquire the frequency of 8 channels to calculate the pressure of 4 channels and report it to the upper-level system, featuring low cost, high precision and high efficiency. Attached Figure Description
[0033] Figure 1 It refers to the interface design of the acquisition channel;
[0034] Figure 2 It is a decision design for synchronous implementation algorithms. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in more detail below with reference to the accompanying drawings.
[0036] Example 1. The system collects pressure signals from 4 pressure sensors (converted into 8 frequency signals). In addition to ensuring high accuracy, the frequency acquisition must also ensure real-time performance.
[0037] The frequency acquisition function is implemented through the processor's internal timer and external counter. It adopts a fixed-period sampling method, that is, it synchronously counts the measured frequency (low frequency) and the reference frequency (high frequency) within a fixed sampling period (10ms) to obtain the change in the count value of the silicon resonant frequency (low frequency) and the change in the count value of the high-frequency clock reference (high frequency). The frequency acquisition and calculation are completed by comparing with the high-frequency clock reference.
[0038] First, the interface was designed using 16-bit timers with external counting capabilities. The STM32F407 timers (TIM1, TIM3, TIM4, TIM8, TIM9, TIM12) in this operating platform meet the requirements and are designed as low-frequency acquisition input interfaces. These timers are set to continuous incrementing mode, counting on the rising edge of an external pulse. The other two channels acquire two frequencies by setting external dual-channel counters. Simultaneously, the advanced counters (TIM2, TIM5) are set to capture function, and the low-frequency acquisition interface is connected to the four channels of the TIM2 and TIM5 interfaces respectively, ensuring that TIM2 and TIM5 capture the count when a rising edge is detected.
[0039] Then, a decision is made regarding the synchronous counting of high and low frequencies to ensure that the sampling periods corresponding to the high and low frequency counts are consistent. When the timer period expires, the low-frequency count and high-frequency count are sampled three times consecutively. The values of the three low-frequency counts are compared, and a set is selected for subsequent frequency calculations. The specific decision-making scheme is as follows: if the three sets of data are the same, the second set of data is selected; if the last two sets of data are the same, the third set of data is selected; if the first two sets of data are the same, the first set of data is selected.
[0040] After synchronous counting, the measured frequency is calculated based on the high and low frequency count values. The calculation formula is as follows: Where f is the silicon resonant frequency (low frequency), Fs is the high-frequency clock frequency (42MHz), and the measurement principle is to calculate the frequency of the silicon resonant component after conversion by the ratio of the count values within the same period.
[0041] After the two frequencies fp and ft output by the pressure sensor are calculated, the single-channel pressure is calculated using the pressure calculation formula. Then, the four real-time pressures are calculated separately. After smoothing and filtering, the pressure is sent to the upper-level system via the serial bus.
[0042] Example 1. The system collects pressure signals from 4 pressure sensors (converted into 8 frequency signals). In addition to ensuring high accuracy, the frequency acquisition must also ensure real-time performance.
[0043] The frequency acquisition function is implemented through the processor's internal timer and external counter. It adopts a fixed-period sampling method, that is, it synchronously counts the measured frequency (low frequency) and the reference frequency (high frequency) within a fixed sampling period (10ms) to obtain the change in the count value of the silicon resonant frequency (low frequency) and the change in the count value of the high-frequency clock reference (high frequency). The frequency acquisition and calculation are completed by comparing with the high-frequency clock reference.
[0044] First, the interface was designed using 16-bit timers with external counting capabilities. The STM32F407 timers (TIM1, TIM3, TIM4, TIM8, TIM9, TIM12) in this operating platform meet the requirements and are designed as low-frequency acquisition input interfaces. These timers are set to continuous incrementing mode, counting on the rising edge of an external pulse. The other two channels acquire two frequencies by setting external dual-channel counters. Simultaneously, the advanced counters (TIM2, TIM5) are set to capture function, and the low-frequency acquisition interface is connected to the four channels of the TIM2 and TIM5 interfaces respectively, ensuring that TIM2 and TIM5 capture the count when a rising edge is detected.
[0045] Then, a decision is made regarding the synchronous counting of high and low frequencies to ensure that the sampling periods corresponding to the high and low frequency counts are consistent. When the timer period expires, the low-frequency count and high-frequency count are sampled three times consecutively. The values of the three low-frequency counts are compared, and a set is selected for subsequent frequency calculations. The specific decision-making scheme is as follows: if the three sets of data are the same, the second set of data is selected; if the last two sets of data are the same, the third set of data is selected; if the first two sets of data are the same, the first set of data is selected.
[0046] After synchronous counting, the measured frequency is calculated based on the high and low frequency count values. The calculation formula is as follows: Where f is the silicon resonant frequency (low frequency), Fs is the high-frequency clock frequency (42MHz), and the measurement principle is to calculate the frequency of the silicon resonant component after conversion by the ratio of the count values within the same period.
[0047] After the two frequencies fp and ft output by the pressure sensor are calculated, the single-channel pressure is calculated using the pressure calculation formula. Then, the four real-time pressures are calculated separately. After smoothing and filtering, the pressure is sent to the upper-level system via the serial bus.
Claims
1. A multi-channel frequency acquisition system for atmospheric data, characterized in that, The system includes a data acquisition chip, an external counter, sensor 1, sensor 2, sensor 3, and sensor 4. The data acquisition chip has eight low-frequency acquisition channels, six of which correspond to six low-frequency acquisition timers: TIM1, TIM3, TIM4, TIM8, TIM9, and TIM12. The external counter includes channels CLKA and CLKB, which are connected to the remaining two channels of the data acquisition chip. Sensor 1's pressure calculation frequency output channel fp1 is connected to low-frequency acquisition timer TIM4, and sensor 1's temperature calculation frequency output channel ft1 is connected to low-frequency acquisition timer TIM3. Sensor 2's pressure calculation frequency output channel fp2 is connected to low-frequency acquisition timer TIM12, and sensor 2's temperature calculation frequency output channel ft1 is connected to low-frequency acquisition timer TIM3.
2. Connected to low-frequency acquisition timer TIM8; the pressure calculation frequency output channel fp3 of sensor 3 is connected to channel CLKA, and the temperature calculation frequency output channel ft3 of sensor 3 is connected to low-frequency acquisition timer TIM9; the pressure calculation frequency output channel fp4 of sensor 4 is connected to channel CLKB, and the temperature calculation frequency output channel ft4 of sensor 4 is connected to timer TIM1; the acquisition chip also includes two 4-channel high-frequency counters TIM5 and TIM2; the four channels of high-frequency counter TIM5 are respectively connected to low-frequency acquisition timers TIM4, TIM12 and channels CLKA, CLKB; the four channels of high-frequency counter TIM2 are respectively connected to low-frequency acquisition timers TIM3, TIM8, TIM9 and TIM1.
2. The multi-channel frequency acquisition system for atmospheric data according to claim 1, characterized in that, The acquisition chip is an STM32F407 chip.
3. The multi-channel frequency acquisition system for atmospheric data according to claim 1, characterized in that, The external counter is model SN74LV8154.
4. The multi-channel frequency acquisition system for atmospheric data according to claim 1, characterized in that, Sensors 1, 2, 3, and 4 are all pressure-sensitive sensors.
5. A method for acquiring atmospheric data using a multi-channel frequency acquisition system as described in any one of claims 1-4, characterized in that, Sensor 1 converts the acquired pressure signal into pressure frequency and temperature frequency signals, respectively, and inputs them to the low-frequency acquisition timers TIM4 and TIM3 of the acquisition chip through pressure calculation frequency output channel fp1 and temperature calculation frequency output channel ft1, respectively; Sensor 2 converts the acquired pressure signal into pressure frequency and temperature frequency signals, respectively, and inputs them to the low-frequency acquisition timers TIM12 and TIM8 of the acquisition chip through pressure calculation frequency output channel fp2 and temperature calculation frequency output channel ft2, respectively; Sensor 3 converts the acquired pressure signal into a pressure frequency signal and inputs it to an external counter through pressure calculation frequency output channel fp3. The pressure signal is input to the acquisition chip via channel CLKA of an external counter; sensor 3 converts the acquired pressure signal into a temperature frequency signal and inputs it to the low-frequency acquisition timer TIM9 of the acquisition chip via temperature calculation frequency output channel ft3; sensor 4 converts the acquired pressure signal into a pressure frequency signal and inputs it to an external counter via pressure calculation frequency output channel fp4, and then inputs it to the acquisition chip via channel CLKB of the external counter; sensor 4 converts the acquired pressure signal into a temperature frequency signal and inputs it to the low-frequency acquisition timer TIM1 of the acquisition chip via temperature calculation frequency output channel ft4; both the pressure frequency signal and the temperature frequency signal are low-frequency signals. When the pressure frequency signals acquired by TIM2, TIM12, channel CLKA and channel CLKB have a rising edge, the corresponding channel of high frequency counter TIM5 is excited to capture the high frequency count value of its own high frequency signal. When the temperature frequency signals acquired by TIM3, TIM8, TIM9, and TIM1 have a rising edge, the corresponding channel of the high-frequency counter TIM2 is excited to capture the high-frequency count value of its own high-frequency signal. Synchronize the high-frequency count values captured in high-frequency counters TIM5 and TIM2 with the low-frequency count values acquired by the 8 low-frequency acquisition channels; After synchronization, the measured frequency is calculated based on the changes in high and low frequency count values within the period.
6. The acquisition method of the multi-channel frequency acquisition system for atmospheric data according to claim 5, characterized in that, The synchronization method is as follows: When the timer period expires, the low-frequency count and high-frequency count are sampled three times consecutively. The values of the three low-frequency counts are compared, and a set is selected for subsequent frequency calculation.
7. The acquisition method of the multi-channel frequency acquisition system for atmospheric data according to claim 6, characterized in that, The specific decision-making method is as follows: if the three sets of data collected are the same, the second set of data is selected; if the last two sets of data are the same, the third set of data is selected; if the first two sets of data are the same, the first set of data is selected.
8. The acquisition method of the multi-channel frequency acquisition system for atmospheric data according to claim 5, characterized in that, After synchronous counting, the measured frequency is calculated based on the high and low frequency count values. The calculation formula is as follows: Where f is the low-frequency silicon resonant frequency, Fs is the high-frequency clock frequency of the high-frequency counters TIM5 and TIM2, and n is the high-frequency clock frequency of the high-frequency counters TIM5 and TIM2. i n is the initial low-frequency count value for this sampling period. i+1 N is the initial low-frequency count value for the next sampling period. i N is the initial high-frequency count value for this sampling period. i+1 This is the initial high-frequency count value for the next sampling period.
9. The acquisition method of the multi-channel frequency acquisition system for atmospheric data according to claim 8, characterized in that, The high-frequency clock frequency is set to 42MHz.