Lifting speed filtering method and system based on second-order butterworth filter

Abstract

The application relates to the field of avionics, and discloses a lifting speed filtering method and system based on a second-order Butterworth filter, which comprises the following steps: collecting an atmospheric pressure signal of an airplane in real time, calculating an air pressure height according to the atmospheric pressure signal, calculating a lifting speed signal according to the air pressure height, performing amplitude-frequency characteristic analysis on the lifting speed signal to determine a cutoff frequency of the second-order Butterworth filter, dynamically adjusting the cutoff frequency of the second-order Butterworth filter according to the flight state of the airplane, inputting the lifting speed signal into the second-order Butterworth filter with the adjusted cutoff frequency, and obtaining a filtered lifting speed signal. The application realizes scientific design of filter parameters by performing amplitude-frequency characteristic analysis on the lifting speed signal and obtaining a digital filter structure through denormalization processing and bilinear transformation, determines the cutoff frequency based on the physical characteristics of the signal, and avoids the disadvantages of selecting parameters by experience in the traditional method.

Description

Technical Field

[0001] This invention relates to the field of avionics technology, and in particular to a method and system for filtering acceleration and deceleration based on a second-order Butterworth filter. Background Technology

[0002] Climb / deceleration rate (CDR) is a crucial flight parameter in air data systems, providing vital information for ensuring flight safety. It's used for climb and descent control during flight and is a primary input parameter for the flight control system. Since CDR is calculated based on altitude, which in turn is calculated from atmospheric pressure sensed by sensors, atmospheric pressure is susceptible to interference from background noise and electromagnetic signals, leading to fluctuations in the pressure data signal. These fluctuations in atmospheric pressure, when transmitted to the CDR signal, can amplify the CDR fluctuations significantly, impacting aircraft safety, reliability, and comfort.

[0003] To improve the real-time performance and stability of acceleration / deceleration signals, the commonly used filtering methods are first-order alpha filtering or moving average filtering with a length of N. First-order alpha filtering is relatively simple to implement, but the selection of its alpha filter coefficients directly affects the filtering effect, making it difficult to simultaneously achieve both real-time performance and stability. Moving average filtering with a length of N exhibits poor real-time performance when N is large, and significant fluctuations when N is small. Regardless of the approach used, it is difficult to simultaneously meet the requirements of both real-time performance and stability.

[0004] Furthermore, existing technologies rely primarily on engineers' experience and flight testing to determine filter parameters, lacking a systematic parameter design methodology. Moreover, traditional solutions use fixed filter parameters, making dynamic adjustments impossible based on changes in flight conditions. In actual flight, aircraft frequently switch between climb, descent, and level flight states, making it difficult for filters with fixed parameters to maintain optimal filtering performance under all conditions.

[0005] Therefore, there is an urgent need for a filtering method that can both meet the real-time requirements of flight control and ensure data stability and reliability. Summary of the Invention

[0006] The purpose of this invention is to provide a method and system for filtering the acceleration and deceleration based on a second-order Butterworth filter, which can eliminate the influence of background noise and electromagnetic signals and other interference signals, and better meet the real-time requirements of flight control under different flight conditions, ensuring the stability and reliability of data.

[0007] To achieve the above-mentioned objectives, the technical solution provided by this invention includes:

[0008] A method for filtering acceleration and deceleration based on a second-order Butterworth filter includes the following steps:

[0009] The atmospheric pressure signal of the aircraft is collected in real time, and the pressure altitude is calculated based on the atmospheric pressure signal.

[0010] Calculate the ascent / descent speed signal based on the air pressure altitude;

[0011] The amplitude-frequency characteristics of the acceleration / deceleration signal are analyzed to determine the cutoff frequency of the second-order Butterworth filter.

[0012] The cutoff frequency of the second-order Butterworth filter is dynamically adjusted according to the flight status of the aircraft.

[0013] The acceleration / deceleration signal is input into the second-order Butterworth filter after the cutoff frequency is adjusted to obtain the filtered acceleration / deceleration signal.

[0014] Preferably, the step of dynamically adjusting the cutoff frequency of the second-order Butterworth filter according to the aircraft's flight status includes:

[0015] Acquire multiple acceleration and deceleration signal values ​​within a preset time window;

[0016] Calculate the statistical characteristic values ​​of the plurality of acceleration and deceleration speed signal values;

[0017] The flight status is determined based on the comparison between the statistical feature values ​​and the preset threshold.

[0018] Set the corresponding cutoff frequency according to the flight status.

[0019] Preferably, the statistical characteristic value is the average of the plurality of acceleration and deceleration speed signal values;

[0020] When the average value is greater than the positive threshold, it is determined to be in a climbing state, and the cutoff frequency is set to the first frequency value.

[0021] When the mean value is less than the negative threshold, it is determined to be in a downward state, and the cutoff frequency is set to the first frequency value.

[0022] When the mean value is between the negative threshold and the positive threshold, it is determined to be in a level flight state, and the cutoff frequency is set to the second frequency value.

[0023] Wherein, the first frequency value is greater than the second frequency value.

[0024] Preferably, the step of performing amplitude-frequency characteristic analysis on the acceleration / deceleration signal to determine the cutoff frequency of the second-order Butterworth filter includes:

[0025] The initial cutoff frequency of the second-order Butterworth filter is determined based on the sampling period of the acceleration / deceleration signal and the range of its physical characteristics.

[0026] The discretization coefficients of the second-order Butterworth filter are calculated using bilinear transformation based on the sampling period and the initial cutoff frequency.

[0027] Preferably, when the cutoff frequency changes, the discretization coefficients of the second-order Butterworth filter are recalculated based on the changed cutoff frequency and sampling frequency, and the filtering operation is performed using the recalculated discretization coefficients.

[0028] This invention also discloses a speed-increasing filtering system based on a second-order Butterworth filter, comprising:

[0029] The data acquisition module is used to acquire atmospheric pressure signals from the aircraft in real time.

[0030] The calculation module is used to calculate the air pressure altitude based on the atmospheric pressure signal, and to calculate the ascent and descent speed signals based on the air pressure altitude;

[0031] The parameter determination module is used to perform amplitude-frequency characteristic analysis on the acceleration / deceleration signal and determine the cutoff frequency of the second-order Butterworth filter.

[0032] An adaptive adjustment module is used to dynamically adjust the cutoff frequency of the second-order Butterworth filter according to the flight status of the aircraft.

[0033] The filtering module is used to filter the acceleration / deceleration signal using the second-order Butterworth filter after the cutoff frequency adjustment.

[0034] Preferably, the adaptive adjustment module is configured as follows:

[0035] Acquire multiple acceleration and deceleration signal values ​​within a preset time window;

[0036] Calculate the statistical characteristic values ​​of the plurality of acceleration and deceleration speed signal values;

[0037] The flight status is determined based on the comparison between the statistical feature values ​​and the preset threshold.

[0038] Set the corresponding cutoff frequency according to the flight status.

[0039] Preferably, the adaptive adjustment module is configured as follows:

[0040] The average of the multiple acceleration and deceleration speed signal values ​​is calculated as a statistical feature value;

[0041] When the average value is greater than the positive threshold, it is determined to be in a climbing state, and the cutoff frequency is set to the first frequency value.

[0042] When the mean value is less than the negative threshold, it is determined to be in a downward state, and the cutoff frequency is set to the first frequency value.

[0043] When the mean value is between the negative threshold and the positive threshold, it is determined to be in a level flight state, and the cutoff frequency is set to the second frequency value.

[0044] Wherein, the first frequency value is greater than the second frequency value.

[0045] Preferably, the parameter determination module is configured as follows:

[0046] The initial cutoff frequency of the second-order Butterworth filter is determined based on the sampling period of the acceleration / deceleration signal and the range of its physical characteristics.

[0047] The discretization coefficients of the second-order Butterworth filter are calculated using bilinear transformation based on the sampling period and the initial cutoff frequency.

[0048] Preferably, when the cutoff frequency changes, the parameter determination module recalculates the discretization coefficients of the second-order Butterworth filter based on the changed cutoff frequency and sampling frequency, and the filtering module performs filtering operations using the recalculated discretization coefficients.

[0049] Beneficial effects

[0050] This invention analyzes the amplitude-frequency characteristics of acceleration / deceleration signals and obtains a digital filter structure through denormalization and bilinear transformation, thus achieving the scientific design of filter parameters. This method determines the cutoff frequency based on the physical characteristics of the signal, avoiding the drawbacks of traditional methods that rely on experience to select parameters, and providing a theoretical basis for the selection of filter parameters.

[0051] This invention achieves adaptive optimization of the filter's response characteristics by determining the current flight state and dynamically adjusting the cutoff frequency accordingly. When the aircraft is determined to be climbing or descending, the cutoff frequency is adjusted to a higher first preset frequency value, giving the filter a faster response speed; when the aircraft is determined to be in level flight, the cutoff frequency is adjusted to a lower second preset frequency value, enhancing the filter's noise suppression capability. Thus, this invention overcomes the shortcomings of fixed-parameter filters, which cannot simultaneously achieve both real-time performance and stability. Attached Figure Description

[0052] Figure 1 This is a flowchart illustrating the acceleration / deceleration filtering method based on a second-order Butterworth filter in a preferred embodiment of the present invention.

[0053] Figure 2This is a schematic diagram of the acceleration / deceleration filtering system based on a second-order Butterworth filter in a preferred embodiment of the present invention. Detailed Implementation

[0054] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0055] Example 1

[0056] like Figure 1 As shown, this embodiment of the invention provides a method for filtering acceleration and deceleration based on a second-order Butterworth filter.

[0057] S1. Collect the atmospheric pressure signal of the aircraft in real time, and calculate the pressure altitude based on the atmospheric pressure signal.

[0058] The atmospheric pressure P at the aircraft's location is collected in real time by a pressure sensor. Using this atmospheric pressure signal as input, the pressure altitude H is calculated according to the pressure altitude calculation formula. Under the international standard atmospheric model, there is a known conversion relationship between pressure altitude and atmospheric pressure; this conversion process is a fundamental step in atmospheric data calculation.

[0059] In one embodiment of the invention, the sensor employs a high-sensitivity microelectromechanical system (MEMS) piezoresistive structure, converting the analog voltage signal into a digital quantity via a precision analog-to-digital converter (ADC) at a fixed sampling frequency (e.g., 100 Hz or higher). The accuracy of the pressure sensor directly determines the reliability of the subsequently calculated altitude and speed. Considering the modern high-altitude, high-speed flight environment, the sensor typically needs to have temperature compensation capabilities to offset measurement offsets caused by thermal expansion and contraction of the fuselage or temperature drift of electronic components.

[0060] S2. Calculate the ascent and descent speed signal based on the air pressure altitude.

[0061] Using the barometric altitude signal as input, the altitude signal V is calculated according to the formula for calculating the altitude signal.

[0062] In existing technologies, there are various methods for calculating acceleration and deceleration signals, including integration, interpolation, and multi-order difference methods. Among these, the integration method requires accelerometer data for assistance, which increases the hardware cost and complexity of the system; while the multi-order difference method can improve calculation accuracy, it introduces greater latency, affecting real-time performance.

[0063] To address the aforementioned shortcomings, in some preferred embodiments of the present invention, the ascent / descent speed signal V is obtained by performing a first-order difference operation on the air pressure altitude H:

[0064] V(n) = [H(n) - H(n-1)] / T; where V(n) is the acceleration / deceleration signal calculated at the current sampling time; H(n) is the air pressure altitude at the current sampling time; H(n-1) is the air pressure altitude at the previous sampling time; T is the sampling period, i.e. the time interval between two adjacent samplings; n is the sampling time number, and n-1 represents the previous sampling time.

[0065] The advantages of using first-order difference operations are: simple calculation, low latency, and the ability to complete the calculation by only storing the data from the previous cycle, making it very suitable for implementation in embedded real-time systems. Although first-order difference is relatively sensitive to noise, the subsequent adaptive filtering steps of this invention can effectively compensate for this deficiency.

[0066] S3. Perform amplitude-frequency characteristic analysis on the acceleration / deceleration signal to determine the cutoff frequency of the second-order Butterworth filter.

[0067] In existing technologies, the selection of filter cutoff frequency often relies on engineering experience or trial-and-error methods. Engineers typically preset a cutoff frequency value based on subjective judgment and then adjust it through repeated experiments. This method has the following drawbacks: first, it lacks scientific basis, and different engineers may arrive at significantly different parameters; second, it lacks specificity and is difficult to optimize based on specific signal characteristics; and third, it is inefficient, requiring a large number of experiments to find suitable parameters.

[0068] To address the aforementioned shortcomings, in some preferred embodiments of the present invention, a system analysis method based on the physical characteristics of the signal is used to determine the cutoff frequency, specifically including:

[0069] First, the amplitude-frequency characteristics of the calculated acceleration / deceleration signal are analyzed based on the sampling period and normal parameter range to obtain the physical characteristics of the acceleration / deceleration signal. Then, by collecting a data sequence of acceleration / deceleration signal over a period of time, spectral analysis is performed on the data sequence to determine the main frequency range of the effective components and the frequency range of the noise components in the acceleration / deceleration signal.

[0070] Then, the cutoff frequency fd is determined based on the amplitude-frequency response analysis results. The selection of the cutoff frequency should ensure that the effective signal can pass through smoothly, while suppressing noise components as much as possible.

[0071] Next, the filter is denormalized. Since Butterworth filters are typically designed at a normalized frequency, denormalization is necessary based on the actual sampling and cutoff frequencies.

[0072] Finally, a bilinear transform is performed on the denormalized filter to obtain the digital filter structure of the second-order Butterworth filter.

[0073] After bilinear transformation, the difference equation structure of the second-order Butterworth filter is obtained:

[0074] d(n)=x(n)-a1×d(n-1)-a2×d(n-2);

[0075] y(n)=b0×d(n)+b1×d(n-1)+b2×d(n-2);

[0076] Where x(n) is the unfiltered acceleration / deceleration signal input at the current sampling time; y(n) is the filtered acceleration / deceleration signal output at the current sampling time; d(n) is the intermediate variable value at the current sampling time, used for internal state calculation of the filter; d(n-1) is the intermediate variable value at the previous sampling time; d(n-2) is the intermediate variable value at the sampling time two periods prior; b0, b1, and b2 are the feedforward coefficients of the filter, which determine the influence weight of the input signal on the output; a1 and a2 are the feedback coefficients of the filter, which determine the influence weight of the historical output on the current output; and n is the sampling time number.

[0077] S4. The cutoff frequency of the second-order Butterworth filter is dynamically adjusted according to the flight status of the aircraft.

[0078] In existing technologies, the main methods for determining flight status are as follows: first, directly using the current altitude and climb rate signal values; second, using the mode signals provided by the flight control system; and third, averaging over a fixed time window. Among these, directly using the current value is susceptible to noise interference, leading to frequent misjudgments; using flight control mode signals requires an additional system interface, increasing coupling; and averaging over a fixed time window makes it difficult to achieve a balance between response speed and judgment stability.

[0079] To address the aforementioned shortcomings, in some preferred embodiments of the present invention, a flight status determination method based on the average number of cycles is employed:

[0080] In some preferred embodiments, a specific method for dynamically adjusting the cutoff frequency of the second-order Butterworth filter is provided, including:

[0081] S41. Acquire multiple acceleration and deceleration signal values ​​within a preset time window. The preset time window is used to slide and acquire historical records for a preset duration (e.g., 1 second or 2 seconds). Within this window, the system acquires multiple consecutive acceleration and deceleration signal sample values.

[0082] S42. Calculate the statistical characteristic value of the plurality of acceleration and deceleration signal values. The statistical characteristic value is not only a numerical average, but also a physical inertial judgment. In the most common implementation, the mean is used as the statistical characteristic value.

[0083] S43. Determine the flight status based on the comparison result between the statistical feature value and the preset threshold.

[0084] In some preferred embodiments, if the arithmetic mean of the climb rate signals within these 2 seconds exceeds a certain positive preset threshold (e.g., +0.5 m / s), then the possibility of instantaneous noise is excluded, and it is determined that the aircraft is in a defined climb state.

[0085] Furthermore, to enhance the rigor of the judgment, in some advanced embodiments, the statistical feature values ​​can also adopt a weighted moving average, assigning higher weights to data closer to the present, thereby reducing recognition delay while maintaining noise resistance.

[0086] Based on the comparison of statistical characteristic values ​​with positive / negative thresholds, the system divides the flight state into a clear three-state logic:

[0087] 1. State A (Climbing): Average value > positive threshold. Conclusion: High dynamics; set the cutoff frequency to a relatively high first frequency value.

[0088] 2. State B (Sliding): Average value < negative threshold. Conclusion: High dynamics; set the cutoff frequency to a relatively high first frequency value.

[0089] 3. State C (Level Flight): The average value lies between the positive and negative thresholds. Conclusion: Low dynamics; set the cutoff frequency to a lower second frequency value.

[0090] This three-state classification perfectly meets the needs of aerospace engineering. The difference between the first and second frequency values ​​(e.g., one selects 1.5Hz, and the other selects 1.0Hz) forms the core of the adaptive mechanism.

[0091] The advantages of using the above method are: averaging based on the number of periods rather than a fixed time can adapt to different sampling frequency configurations; averaging can effectively smooth instantaneous noise fluctuations and avoid misjudgments caused by single-point data anomalies; and by reasonably setting the number of periods N and the threshold, a good balance can be achieved between response speed and judgment stability.

[0092] S44. Set the corresponding cutoff frequency according to the flight status.

[0093] In some existing technologies, several pre-calculated coefficient tables are used, and parameters are obtained by looking up the tables during state switching. Although this method saves computational power, it introduces the hard switching problem, that is, sudden changes in coefficients can cause a step jump in the filter output y(n).

[0094] In some preferred embodiments, when the adaptive adjustment detects a change in state, the bilinear transform program is invoked in real time to recalculate the discretization coefficients a1, a2, b0, b1, b2 based on the new precise cutoff frequency after the change.

[0095] This real-time recalculation method allows for the setting of a transition band (which can even be continuously adjusted rather than a step switch) between the first and second frequency values. When the cutoff frequency changes, the system updates the coefficient matrix and smoothly injects these new coefficients into the filtering algorithm. Because there is a clear mathematical relationship between the coefficients of the second-order structure and the cutoff frequency, real-time computation eliminates the reliance on massive storage tables and enhances the algorithm's general adaptability to different sampling frequencies fs.

[0096] S5. Input the acceleration / deceleration signal into the second-order Butterworth filter after the cutoff frequency adjustment to obtain the filtered acceleration / deceleration signal.

[0097] The average climb and descent rates over the first 10 cycles are calculated. When the average is greater than 0.5 m / s or less than -0.5 m / s, it indicates that the aircraft is climbing or descent, and the cutoff frequency is set to 1.5. Otherwise, it indicates that the aircraft is in level flight, and the cutoff frequency is set to 1.0. This dynamically adjusts the second-order Butterworth filter coefficients to achieve adaptive filtering of climb and descent rates.

[0098] Example 2

[0099] like Figure 2 As shown, this embodiment discloses a speed-up / down velocity filtering system based on a second-order Butterworth filter, including:

[0100] The data acquisition module is used to acquire atmospheric pressure signals from the aircraft in real time.

[0101] The calculation module is used to calculate the air pressure altitude based on the atmospheric pressure signal, and to calculate the ascent and descent speed signals based on the air pressure altitude;

[0102] The parameter determination module is used to perform amplitude-frequency characteristic analysis on the acceleration / deceleration signal and determine the cutoff frequency of the second-order Butterworth filter.

[0103] An adaptive adjustment module is used to dynamically adjust the cutoff frequency of the second-order Butterworth filter according to the flight status of the aircraft.

[0104] The filtering module is used to filter the acceleration / deceleration signal using the second-order Butterworth filter after the cutoff frequency adjustment.

[0105] Preferably, the adaptive adjustment module is configured as follows:

[0106] Acquire multiple acceleration and deceleration signal values ​​within a preset time window;

[0107] Calculate the statistical characteristic values ​​of the plurality of acceleration and deceleration speed signal values;

[0108] The flight status is determined based on the comparison between the statistical feature values ​​and the preset threshold.

[0109] Set the corresponding cutoff frequency according to the flight status.

[0110] Preferably, the adaptive adjustment module is configured as follows:

[0111] The average of the multiple acceleration and deceleration speed signal values ​​is calculated as a statistical feature value;

[0112] When the average value is greater than the positive threshold, it is determined to be in a climbing state, and the cutoff frequency is set to the first frequency value.

[0113] When the mean value is less than the negative threshold, it is determined to be in a downward state, and the cutoff frequency is set to the first frequency value.

[0114] When the mean value is between the negative threshold and the positive threshold, it is determined to be in a level flight state, and the cutoff frequency is set to the second frequency value.

[0115] Wherein, the first frequency value is greater than the second frequency value.

[0116] Preferably, the parameter determination module is configured as follows:

[0117] The initial cutoff frequency of the second-order Butterworth filter is determined based on the sampling period of the acceleration / deceleration signal and the range of its physical characteristics.

[0118] The discretization coefficients of the second-order Butterworth filter are calculated using bilinear transformation based on the sampling period and the initial cutoff frequency.

[0119] Preferably, when the cutoff frequency changes, the parameter determination module recalculates the discretization coefficients of the second-order Butterworth filter based on the changed cutoff frequency and sampling frequency, and the filtering module performs filtering operations using the recalculated discretization coefficients.

[0120] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method of lift velocity filtering based on a second order Butterworth filter, characterized in that, Includes the following steps: The atmospheric pressure signal of the aircraft is collected in real time, and the pressure altitude is calculated based on the atmospheric pressure signal. Calculate the ascent / descent speed signal based on the air pressure altitude; The amplitude-frequency characteristics of the acceleration / deceleration signal are analyzed to determine the cutoff frequency of the second-order Butterworth filter. The cutoff frequency of the second-order Butterworth filter is dynamically adjusted according to the flight status of the aircraft. The acceleration / deceleration signal is input into the second-order Butterworth filter after the cutoff frequency is adjusted to obtain the filtered acceleration / deceleration signal. The step of dynamically adjusting the cutoff frequency of the second-order Butterworth filter according to the aircraft's flight status includes: Acquire multiple acceleration and deceleration signal values ​​within a preset time window; Calculate the statistical characteristic values ​​of the plurality of acceleration and deceleration speed signal values; The flight status is determined based on the comparison between the statistical feature values ​​and the preset threshold. Set the corresponding cutoff frequency according to the flight status; The statistical characteristic value is the average of the multiple acceleration and deceleration speed signal values; When the average value is greater than the positive threshold, it is determined to be in a climbing state, and the cutoff frequency is set to the first frequency value. When the mean value is less than the negative threshold, it is determined to be in a downward state, and the cutoff frequency is set to the first frequency value. When the mean value is between the negative threshold and the positive threshold, it is determined to be in a level flight state, and the cutoff frequency is set to the second frequency value. Wherein, the first frequency value is greater than the second frequency value; The step of performing amplitude-frequency characteristic analysis on the acceleration / deceleration signal to determine the cutoff frequency of the second-order Butterworth filter includes: The initial cutoff frequency of the second-order Butterworth filter is determined based on the sampling period of the acceleration / deceleration signal and the range of its physical characteristics. The discretization coefficients of the second-order Butterworth filter are calculated using bilinear transformation based on the sampling period and the initial cutoff frequency.

2. The method of claim 1, wherein, When the cutoff frequency changes, the discretization coefficients of the second-order Butterworth filter are recalculated based on the changed cutoff frequency and sampling frequency, and the filtering operation is performed using the recalculated discretization coefficients.

3. A speed filtering system based on a second-order Butterworth filter, characterized in that, include: The data acquisition module is used to acquire atmospheric pressure signals from the aircraft in real time. The calculation module is used to calculate the air pressure altitude based on the atmospheric pressure signal, and to calculate the ascent and descent speed signals based on the air pressure altitude; The parameter determination module is used to perform amplitude-frequency characteristic analysis on the acceleration / deceleration signal and determine the cutoff frequency of the second-order Butterworth filter. An adaptive adjustment module is used to dynamically adjust the cutoff frequency of the second-order Butterworth filter according to the flight status of the aircraft. The filtering module is used to filter the acceleration / deceleration signal using the second-order Butterworth filter after the cutoff frequency adjustment; The adaptive adjustment module is configured as follows: Acquire multiple acceleration and deceleration signal values ​​within a preset time window; Calculate the statistical characteristic values ​​of the plurality of acceleration and deceleration speed signal values; The flight status is determined based on the comparison between the statistical feature values ​​and the preset threshold. Set the corresponding cutoff frequency according to the flight status; The adaptive adjustment module is configured as follows: The average of the multiple acceleration and deceleration speed signal values ​​is calculated as a statistical feature value; When the average value is greater than the positive threshold, it is determined to be in a climbing state, and the cutoff frequency is set to the first frequency value. When the mean value is less than the negative threshold, it is determined to be in a downward state, and the cutoff frequency is set to the first frequency value. When the mean value is between the negative threshold and the positive threshold, it is determined to be in a level flight state, and the cutoff frequency is set to the second frequency value. Wherein, the first frequency value is greater than the second frequency value; The parameter determination module is configured as follows: The initial cutoff frequency of the second-order Butterworth filter is determined based on the sampling period of the acceleration / deceleration signal and the range of its physical characteristics. The discretization coefficients of the second-order Butterworth filter are calculated using bilinear transformation based on the sampling period and the initial cutoff frequency.

4. The system according to claim 3, characterized in that, When the cutoff frequency changes, the parameter determination module recalculates the discretization coefficients of the second-order Butterworth filter based on the changed cutoff frequency and sampling frequency, and the filtering module uses the recalculated discretization coefficients to perform filtering operations.

Images