An atmospheric pressure signal filtering method based on elliptic filters

Abstract

The present invention belongs to the technical field of atmospheric systems, and particularly relates to an atmospheric pressure signal filtering method based on an elliptic filter. The method includes: S1, collecting and resolving the atmospheric pressure signal of a certain type of aircraft in real time to obtain the resolved atmospheric pressure signal; S2, performing amplitude-frequency characteristic analysis on the resolved atmospheric pressure signal to obtain the physical characteristics of the resolved atmospheric pressure signal; S3, determining the performance parameters of the elliptic filter according to the type of the aircraft, the sampling period of the atmospheric pressure signal, and the physical characteristics of the resolved atmospheric pressure signal; S4, inputting the resolved atmospheric pressure signal into the elliptic filter to obtain the filtered atmospheric pressure signal. This method can dynamically adjust the elliptic filtering parameters according to different types of aircraft and acquisition periods, achieving the effects of reducing the fluctuation of the atmospheric pressure signal while reducing the startup output time and improving the real-time response.

Description

Technical Field

[0001] The present invention belongs to the technical field of the atmospheric system, and particularly relates to a filtering method for atmospheric pressure signals based on an elliptic filter. Background Art

[0002] The atmospheric pressure signal is one of the original atmospheric characteristic parameters, and it is the basis for calculating atmospheric flight parameters such as barometric altitude, indicated altitude, and rate of climb or descent. It is important information to ensure the safe flight of an aircraft. Due to the influence of background noise and other interference signals such as electromagnetic signals, the atmospheric pressure signal collected by the pressure sensor fluctuates greatly, and it is impossible to provide stable barometric altitude, altitude, rate of climb or descent and other important flight parameters to the relevant systems of the aircraft, affecting the safety, maneuverability and comfort of the aircraft.

[0003] To reduce the fluctuation of the atmospheric pressure signal and improve the response speed, currently, a smoothing filtering method with a window length of N is generally used to digitally filter the atmospheric pressure signal. Due to the constraints of the smoothing filtering method itself, it is impossible to quickly reflect the change of the current atmospheric pressure while removing the influence of the atmospheric pressure acquisition noise. That is, when the number of source data used for filtering is small, the stability of the filtered atmospheric pressure signal cannot meet the ideal requirements. When the number of source data used for filtering is large, the real-time response of the filtered atmospheric pressure signal is poor. At the same time, after the filtering starts, N data need to be obtained before an effective atmospheric pressure signal can be output. In addition, for different types of aircraft, the window length of the smoothing filter needs to be changed to meet the maneuvering characteristics of various aircraft, and the filtering method cannot dynamically be compatible with multiple types of aircraft. Summary of the Invention

[0004] Aiming at the above problems, the purpose of the present invention is to provide a filtering method for atmospheric pressure signals based on an elliptic filter, which can effectively eliminate the interference of background noise and electromagnetic signals during the acquisition of atmospheric pressure, reduce the fluctuation of the atmospheric pressure signal collected by the aircraft, and ensure the stability and real-time performance of the subsequent atmospheric parameter calculation.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions.

[0006] A filtering method for atmospheric pressure signals based on an elliptic filter, the method comprising:

[0007] S1, collecting and calculating the atmospheric pressure signal of a certain type of aircraft in real time to obtain the calculated atmospheric pressure signal;

[0008] S2, performing amplitude-frequency characteristic analysis on the calculated atmospheric pressure signal to obtain the physical characteristics of the calculated atmospheric pressure signal;

[0009] S3. Determine the performance parameters of the elliptic filter according to the type of the aircraft, the sampling period of the atmospheric pressure signal, and the physical characteristics of the resolved atmospheric pressure signal;

[0010] S4. Input the resolved atmospheric pressure signal into the elliptic filter to obtain the filtered atmospheric pressure signal.

[0011] The features and further improvements of the technical solution of the present invention are as follows:

[0012] (1) Specifically, S1 is as follows:

[0013] The atmospheric pressure sensor collects the atmospheric pressure signal of a certain type of aircraft in real time, converts the atmospheric pressure signal into a frequency signal, performs frequency conversion on it and uses the corresponding high-order equation for calculation to obtain the resolved atmospheric pressure signal.

[0014] (2) Specifically, S2 is as follows:

[0015] Perform frequency domain conversion on the atmospheric pressure signals within multiple flight envelopes of a certain type of aircraft respectively, and perform amplitude-frequency characteristic analysis to determine the frequency domain characteristics of the atmospheric pressure signal of this type of aircraft, and obtain the physical characteristics of the resolved atmospheric pressure signal.

[0016] (3) Specifically, S3 is as follows:

[0017] Determine the performance parameters of the elliptic filter, including the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ in the passband p , the minimum attenuation δ that should be achieved in the stopband s ;

[0018] According to the physical characteristics of the resolved atmospheric pressure signal and the elliptic filter order calculation formula, determine the order n of the elliptic filter for this type of aircraft and the corresponding sampling period;

[0019] According to the order n of the elliptic filter, the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ in the passband p , the minimum attenuation δ that should be achieved in the stopband s and the sampling period, determine the initial variable coefficients of the elliptic filter.

[0020] (4) Specifically, S4 is as follows:

[0021] Filter the resolved atmospheric pressure signal according to the determined elliptic filter, and adjust the variable coefficients of the elliptic filter according to the filtered outputs of multiple periods.

[0022] (5) Adjust the variable coefficients of the elliptic filter according to the filtered outputs of multiple cycles, specifically: calculate the standard deviation of the filtered output signals of multiple cycles and compare it with a set threshold;

[0023] When the standard deviation of the filtered output signals of multiple cycles is less than the set threshold, keep the variable coefficients of the elliptic filter;

[0024] When the standard deviation of the filtered output signals of multiple cycles is greater than the set threshold, then dynamically adjust the variable coefficients of the elliptic filter according to a preset rule, so as to change the cut-off frequency of the elliptic filter and perform adaptive filtering on the resolved atmospheric pressure signal.

[0025] (6) Calculate the standard deviation of the filtered output signal of each cycle together with the filtered signals of previous multiple cycles. If the standard deviation calculated in the current cycle is greater than the set threshold, dynamically adjust the variable coefficients of the elliptic filter according to the atmospheric pressure corresponding to the filtered output atmospheric pressure signal of the previous cycle, the type of aircraft, and the sampling period.

[0026] (7) Dynamically adjust the variable coefficients of the elliptic filter according to a preset rule, and the preset rule is specifically:

[0027] Conduct multiple experiments in advance to determine the variable coefficients of the elliptic filter corresponding to different types of aircraft, different sampling periods, and different atmospheric pressures.

[0028] The technical solution of the present invention is based on an elliptic filter, and proposes a method for filtering atmospheric pressure signals, making up for the deficiencies of the prior art. At the same time, it can dynamically adjust the elliptic filter parameters according to different types of aircraft and acquisition periods, achieving the effects of reducing the fluctuation of the atmospheric pressure signal, reducing the start-up output time, and improving the real-time response. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic flow chart of a method for filtering an atmospheric pressure signal based on an elliptic filter provided by an embodiment of the present invention;

[0030] Figure 2 is a schematic diagram of the principle of adaptive filtering provided by an embodiment of the present invention;

[0031] Figure 3 is a comparison chart of the filtering effects of the method for filtering an atmospheric pressure signal based on an elliptic filter and the prior art. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] An embodiment of the present invention provides a method for filtering an atmospheric pressure signal based on an elliptic filter, as Figure 1 shown, the method includes:

[0033] S1. Collect and calculate the atmospheric pressure signal of a certain type of aircraft in real time to obtain the calculated atmospheric pressure signal.

[0034] S2. Analyze the amplitude-frequency characteristics of the calculated atmospheric pressure signal to obtain the physical characteristics of the calculated atmospheric pressure signal.

[0035] S3. Determine the performance parameters of the elliptic filter according to the type of the aircraft, the sampling period of the atmospheric pressure signal, and the physical characteristics of the calculated atmospheric pressure signal.

[0036] S4. Input the calculated atmospheric pressure signal into the elliptic filter to obtain the filtered atmospheric pressure signal.

[0037] The features and further improvements of the technical solution of the present invention are as follows:

[0038] (1) Specifically, S1 is as follows: The atmospheric pressure sensor collects the atmospheric pressure signal of a certain type of aircraft in real time, converts the atmospheric pressure signal into a frequency signal, performs frequency conversion on it and uses the corresponding high-order equation for calculation to obtain the calculated atmospheric pressure signal.

[0039] (2) Specifically, S2 is as follows: Perform frequency domain conversion on the atmospheric pressure signals within multiple flight envelopes of a certain type of aircraft respectively, and perform amplitude-frequency characteristic analysis to determine the frequency domain characteristics of the atmospheric pressure signal of this type of aircraft, and obtain the physical characteristics of the calculated atmospheric pressure signal.

[0040] (3) Specifically, S3 is as follows: Determine the performance parameters of the elliptic filter, including the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ in the passband p , the minimum attenuation δ that should be achieved in the stopband s ;

[0041] According to the physical characteristics of the calculated atmospheric pressure signal and the elliptic filter order calculation formula, determine the order n of the elliptic filter for this type of aircraft and the corresponding sampling period; according to the order n of the elliptic filter, the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ in the passband p , the minimum attenuation δ that should be achieved in the stopband s and the sampling period, determine the initial variable coefficients of the elliptic filter.

[0042] (4) Specifically, S4 is as follows: Filter the calculated atmospheric pressure signal according to the determined elliptic filter, and adjust the variable coefficients of the elliptic filter according to the filtering outputs of multiple periods.

[0043] (5) Adjust the variable coefficients of the elliptic filter according to the filtered outputs of multiple cycles, specifically: calculate the standard deviation of the filtered output signals of multiple cycles and compare it with a set threshold; when the standard deviation of the filtered output signals of multiple cycles is less than the set threshold, keep the variable coefficients of the elliptic filter; when the standard deviation of the filtered output signals of multiple cycles is greater than the set threshold, dynamically adjust the variable coefficients of the elliptic filter according to a preset rule, so as to change the cut-off frequency of the elliptic filter and perform adaptive filtering on the resolved atmospheric pressure signal.

[0044] (6) Calculate the standard deviation of the filtered output signal of each cycle together with the filtered signals of previous multiple cycles. When the standard deviation calculated in the current cycle is greater than the set threshold, dynamically adjust the variable coefficients of the elliptic filter according to the atmospheric pressure corresponding to the filtered output atmospheric pressure signal of the previous cycle, the type of aircraft, and the sampling period.

[0045] (7) Dynamically adjust the variable coefficients of the elliptic filter according to a preset rule. The preset rule is specifically: conduct multiple experiments in advance to determine the variable coefficients of the elliptic filter corresponding to different aircraft types, different sampling periods, and different atmospheric pressures.

[0046] Embodiment

[0047] Step 1: Atmospheric pressure acquisition and resolution. The atmospheric pressure sensor converts the external atmospheric pressure signal into a frequency signal, and uses a frequency conversion module to convert it and transmit it to the resolver module. The resolver uses a corresponding high-order equation to resolve the atmospheric pressure.

[0048] Step 2: Analysis of the amplitude-frequency characteristics of the atmospheric pressure signal. Perform frequency domain conversion on the atmospheric pressure signals within multiple flight envelopes of different types of aircraft and conduct amplitude-frequency characteristic analysis to clarify the frequency domain characteristics of the atmospheric pressure signals of different types of aircraft, and design the parameters of the elliptic filter based on this characteristic.

[0049] Step 3: Design of the elliptic filter parameters.

[0050] 1) Determine the filter performance indicators for different types of aircraft and different sampling periods, including the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ p in the passband, and the minimum attenuation δ s that should be achieved in the stopband;

[0051] 2) Determine the order n of the elliptic filter for each type of aircraft and each sampling period according to the physical characteristics of the atmospheric pressure signal and the elliptic filter order calculation formula.

[0052] 3) Determine the variable coefficients of the elliptic filter system based on the order n of the elliptic filter, the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ in the passband p , the minimum attenuation δ that should be achieved in the stopband s and the initial sampling period, such as the a0, a1 and b1 in Figure 2 .

[0053] Step 4: Adaptive atmospheric pressure signal filtering.

[0054] Take the currently actually collected atmospheric pressure x(n) as the initial value, respond to the change of atmospheric pressure in real time, and use an elliptic filter for filtering to obtain a relatively stable and better-responsive atmospheric pressure signal y(n).

[0055] 1) In specific implementation, take the aircraft type and pressure sampling period as the original inputs of the filter, use the initial elliptic filter system to filter the atmospheric pressure signal, and take the filtered atmospheric pressure signal as the input of the filter system in the next period. The schematic diagram is as shown in Figure 2 ;

[0056] 2) At the initial stage of starting filtering or when event-triggered pressure filtering adjustment is carried out, appropriately adjust the elliptic filter system model according to the threshold (mean square error).

[0057] In specific implementation, record the atmospheric pressure signals after filtering for 2000 periods, calculate the standard deviation. If the standard deviation is less than the threshold value, no adjustment of the filter system model is carried out; if the standard deviation is greater than the threshold value, select a suitable filter model according to the atmospheric pressure signal, sampling period and aircraft type after filtering in the previous period, and dynamically adjust the variable coefficients (a0, a1 and b1) of the elliptic filter system, so as to change the cut-off frequency of the elliptic filter, achieve dynamic adjustment of the model of the atmospheric pressure signal filtering system, and realize adaptive atmospheric pressure signal filtering.

[0058] Particularly, in the experiment, the threshold value of 0.25 is selected for adjustment, and the effect of dynamic adjustment of the model is relatively ideal.

[0059] Comparison of the filtering effect of the atmospheric pressure signal filtering method based on the elliptic filter with the prior art is as shown in Figure 3 . The elliptic filter has relatively prominent advantages in both real-time response and stability for filtering the atmospheric pressure signal.

[0060] The present invention can effectively reduce the fluctuation of the atmospheric pressure signal, has a better effect of suppressing noise, and has better response performance. It can be applied to multiple types of aircraft and has good compatibility and universality.

[0061] Based on elliptic filters, the technical solution of the present invention proposes a filtering method for atmospheric pressure signals, making up for the deficiencies of the prior art. At the same time, the elliptic filter parameters can be dynamically adjusted according to different types of aircraft and acquisition periods, achieving the effects of reducing the fluctuation of atmospheric pressure signals, reducing the startup output time, and improving the real-time response.

Claims

1. An atmospheric pressure signal filtering method based on an elliptic filter, characterized in that, The method includes: S1. Collect and calculate the atmospheric pressure signal of a certain type of aircraft in real time to obtain the calculated atmospheric pressure signal; S2. Analyze the amplitude-frequency characteristics of the calculated atmospheric pressure signal to obtain the physical characteristics of the calculated atmospheric pressure signal; S3. Determine the performance parameters and initial variable coefficients of the elliptic filter according to the type of the aircraft, the sampling period of the atmospheric pressure signal, and the physical characteristics of the calculated atmospheric pressure signal; S4. Input the calculated atmospheric pressure signal into the elliptic filter to obtain the filtered atmospheric pressure signal.

2. The atmospheric pressure signal filtering method based on an elliptic filter according to claim 1, wherein, Specifically, S1 is as follows: The atmospheric pressure sensor collects the atmospheric pressure signal of a certain type of aircraft in real time, converts the atmospheric pressure signal into a frequency signal, performs frequency conversion on it and calculates it using the corresponding high-order equation to obtain the calculated atmospheric pressure signal.

3. A filtering method for atmospheric pressure signals based on an elliptic filter according to claim 1, characterized in that Specifically, S2 is as follows: Perform frequency-domain conversion on the atmospheric pressure signal calculated in S1, and perform amplitude-frequency characteristic analysis to determine the frequency-domain characteristics of the atmospheric pressure signal of this type of aircraft, and obtain the physical characteristics of the calculated atmospheric pressure signal.

4. A method for filtering atmospheric pressure signals based on an elliptic filter according to claim 1, characterized in that, Specifically, S3 is as follows: Determine the performance parameters of the elliptical filter, including the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ in the passband p , the minimum attenuation δ that should be achieved in the stopband s ; Determine the order n of the elliptic filter for this type of aircraft and the corresponding sampling period according to the physical characteristics of the calculated atmospheric pressure signal and the elliptic filter order calculation formula; According to the order n of the elliptic filter, the passband cut-off frequency F p , the stopband cut-off frequency F s , the maximum allowable attenuation δ in the passband p , the minimum attenuation δ that should be achieved in the stopband s and the sampling period to determine the initial variable coefficients of the elliptic filter.

5. A method for filtering atmospheric pressure signals based on an elliptic filter according to claim 1, characterized in that, Specifically, S4 is as follows: Filter the calculated atmospheric pressure signal according to the elliptic filter with determined performance parameters, and adjust the variable coefficients of the elliptic filter according to the filtered output signals of multiple periods.

6. A filtering method for atmospheric pressure signals based on an elliptic filter according to claim 5, characterized in that, Adjust the variable coefficients of the elliptic filter according to the filtered output signals of multiple periods, specifically: calculate the standard deviation of the filtered output signals of multiple periods and compare it with the set threshold; When the standard deviation of the filtered output signals of multiple periods is less than the set threshold, keep the variable coefficients of the elliptic filter; When the standard deviation of the filtered output signals of multiple periods is greater than the set threshold, then dynamically adjust the variable coefficients of the elliptic filter according to the preset rules, so as to change the cut-off frequency of the elliptic filter and perform adaptive filtering on the calculated atmospheric pressure signal.

7. A method for filtering atmospheric pressure signals based on an elliptic filter according to claim 6, characterized in that, Calculate the standard deviation of the filtered output signal of each period together with the filtered signals of the previous multiple periods. If the standard deviation calculated in the current period is greater than the set threshold, dynamically adjust the variable coefficients of the elliptic filter according to the atmospheric pressure, aircraft type, and sampling period corresponding to the filtered output atmospheric pressure signal of the previous period.

8. A method for filtering atmospheric pressure signals based on an elliptic filter according to claim 6, characterized in that Dynamically adjust the variable coefficients of the elliptic filter according to the preset rules, and the preset rules are specifically as follows: Conduct multiple tests in advance to determine the variable coefficients of the elliptic filter corresponding to different aircraft types, different sampling periods, and different atmospheric pressures.

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