An aircraft ultrasonic altimetry method, system and storage medium based on dynamic attitude compensation

Abstract

The present invention discloses an ultrasonic altimetry method, system and storage medium for an aircraft based on dynamic attitude compensation, which collects original altitude data h₀ and obtains sampling data of the pitch angle and roll angle of the aircraft; corrects the original altitude data h₀ based on the pitch angle and roll angle of the aircraft to obtain the corrected ultrasonic original altitude h_prev. Based on the attitude sensor speed data, an altitude estimate value is obtained, and the corrected ultrasonic original altitude h_prev is subjected to Kalman filtering to output the optimal altitude estimate value. The present invention performs real-time compensation on ultrasonic altimetry data based on aircraft attitude data, solves problems such as projection errors and data jumps caused by the deflection of the ultrasonic ranging axis under complex attitudes of the aircraft, and has good practicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-altitude altitude measurement of aircraft, and particularly relates to an ultrasonic altitude measurement method, system and storage medium for aircraft based on dynamic attitude compensation. Background Art

[0002] In the field of low-altitude altitude measurement of aircraft (such as unmanned aerial vehicles, helicopters, etc.), ultrasonic altitude measurement technology is widely used due to its low cost, small size, strong anti-interference ability and other characteristics. For example, the existing patent CN104678397A discloses an ultrasonic altimeter for small unmanned aerial vehicles, which introduces ultrasonic ranging technology into the near-ground ranging of unmanned aerial vehicles. The ultrasonic altimeter includes an ultrasonic probe and a signal acquisition box, and the output signal is the time pulse for ultrasonic waves to travel back and forth between the aircraft and the ground. However, this existing technology does not make targeted designs for the geometric errors and signal interferences introduced by the attitude changes of small unmanned aerial vehicles. When the attitude of the unmanned aerial vehicle is tilted, the ultrasonic beam direction is no longer perpendicular to the ground, and the measured distance becomes the slant range rather than the true altitude.

[0003] The existing patent CN103257348A discloses a measurement system and method for the relative altitude and relative attitude of an aircraft. Four ultrasonic ranging modules are installed at different positions of the aircraft. The ultrasonic emission and reception of the ultrasonic ranging modules are controlled by an MPU, the ultrasonic propagation time is calculated, the air pressure, temperature, and humidity parameters of the atmosphere are collected to compensate the ultrasonic propagation speed, and at the same time, a ranging error compensation model is used to compensate the ranging error of the ultrasonic ranging sensor, and the relative altitude data between each and the ground is measured. A relative altitude and attitude calculation model is established to calculate the accurate relative altitude of the center position of the aircraft wing relative to the landing runway plane and the attitude angle information of the ultrasonic installation plane relative to the runway plane. However, this existing technology collects the air pressure, temperature, and humidity parameters of the atmosphere to compensate the ultrasonic propagation speed, but still does not make targeted designs for the geometric errors and signal interferences introduced by the attitude changes of the aircraft.

[0004] In summary, the existing ultrasonic altitude measurement technology still faces bottleneck problems such as geometric errors and signal interferences introduced by the attitude disturbance of the aircraft. Specifically, when the aircraft undergoes attitude deflections such as pitching and rolling, due to the change in the angle between the ultrasonic beam and the ground, the ultrasonic ranging value is only the projection value of the slant range, rather than the true vertical altitude, resulting in projection errors. In addition, attitude changes will also cause problems such as the echo exceeding the acceptance range and the echo being reflected by the fuselage resulting in interference. Summary of the Invention

[0005] The purpose of the present invention is to provide an ultrasonic altitude measurement method, system and storage medium for aircraft based on dynamic attitude compensation, aiming to solve the above problems.

[0006] The present invention is mainly implemented through the following technical solutions:

[0007] An ultrasonic altimetry method for an aircraft based on dynamic attitude compensation, comprising the following steps:

[0008] Step S1: Collect the original altitude data h0 and obtain the sampling data of the pitch angle and roll angle of the aircraft;

[0009] Step S2: Correct the original altitude data h0 based on the pitch angle and roll angle of the aircraft to obtain the corrected ultrasonic original altitude h_prev;

[0010] Step S3: Based on the attitude sensor speed data, obtain the altitude estimate value, perform Kalman filtering on the corrected ultrasonic original altitude h_prev, and output the optimal altitude estimate value.

[0011] To better implement the present invention, further, the step S1 includes the following steps:

[0012] Step S10: Initialize the loop sampling times i_max and set the sliding window length N;

[0013] Step S11: Collect the original altitude data h0 and read the pitch angle and roll angle of the current aircraft;

[0014] Step S12: If the sampling times i exceed the loop sampling times i_max, then enter step S13, otherwise enter step S11;

[0015] Step S13: Perform mean filtering on the sampling data of the pitch angle and roll angle and enter step S2.

[0016] To better implement the present invention, further, in the step S11, the original altitude data h0 is:

[0017] h0 = α_k × h_k,

[0018] where: α_k is the temperature compensation coefficient, and α_k ∈ [0.9, 1.1];

[0019] h_k is the original altitude sampling value;

[0020] The read pitch angle and roll angle of the aircraft are:

[0021] θ_i = θ_raw + Δθ,

[0022] φ_i = φ_raw + Δφ,

[0023] where: θ_i is the pitch angle of the aircraft collected for the i-th time;

[0024] φ_i is the roll angle of the aircraft collected for the i-th time;

[0025] θ_raw is the reading value of the pitch angle sensor;

[0026] φ_raw is the reading value of the roll angle sensor;

[0027] Δθ is the zero-bias compensation value of the pitch angle sensor;

[0028] Δφ is the zero-bias compensation value of the roll angle sensor.

[0029] To better implement the present invention, further, in the step S13, after mean filtering processing, it is obtained that:

[0030] θ' = Σ(w_i × θ_i) / Σw_i,

[0031] φ' = Σ(w_i × φ_i) / Σw_i,

[0032] w_i = 0.5(i_max - i),

[0033] where: θ' is the pitch angle after mean filtering;

[0034] φ' is the roll angle after mean filtering;

[0035] w_i is the weight coefficient in weighted mean filtering.

[0036] To better implement the present invention, further, the step S2 includes the following steps:

[0037] Step S21: Based on three-dimensional space compensation, correct h0 to obtain the corrected ultrasonic original height h_prev:

[0038] h_prev = h0 × cosθ' × cosφ',

[0039] where: θ' is the pitch angle after mean filtering;

[0040] φ' is the roll angle after mean filtering.

[0041] To better implement the present invention, further, the step S21 includes the following steps:

[0042] Step A1: Based on the principle of orthogonal decomposition of spatial vectors, establish the rotation transformation relationship between the aircraft body coordinate system O-XYZ and the ground coordinate system O-X'Y'Z';

[0043] Step A2: Construct a projection relationship through the pitch angle θ ∈ [-π / 2, π / 2] and roll angle φ ∈ [-π, π] of the aircraft, and orthogonally decompose the ultrasonic beam direction vector V = (0, 0, h0) to obtain the attitude compensation height h1.

[0044] To better implement the present invention, further, in step S2, if |θ'| > θ_max or |φ'| > φ_max is not satisfied, then step S21 is entered; otherwise, step S22 is entered; step S2 further includes the following steps:

[0045] Step S22: Correct the original height data and obtain the abnormally corrected height h':

[0046] h' = h0 × sec(min(θ', θ_max)) × sec(min(φ', φ_max)),

[0047] where: θ_max is the maximum beam angle of the pitch angle;

[0048] φ_max is the maximum beam angle of the roll angle;

[0049] Step S23: Then, perform median filtering to obtain the compensated height h1:

[0050] h1 = median{h'(j) × cosθ'(j) × cosφ'(j)}, j ∈ [1, M],

[0051] where: M is the sliding window length of the median filtering;

[0052] j is the index value of the samples within the window, used to traverse all M data points;

[0053] Step S24: Compensate the height h1 using dynamic error correction to obtain the corrected original ultrasonic height h_prev as:

[0054] h_prev = h1 × (1 ± σ), σ = 0.01 × |θ'φ'|,

[0055] where: σ is the dynamic error factor.

[0056] To better implement the present invention, further, step S3 includes the following steps:

[0057] Step S31: Obtain the corrected original ultrasonic height h_prev and the current pulse period T_pulse;

[0058] Step S32: According to the speed threshold, establish a strong coupling relationship between the Kalman iteration period Δt and the ultrasonic hardware transmission pulse T_pulse:

[0059] Δt = 0.7 * T_pulse,

[0060] Force-align the prediction period and the physical echo sampling moment through an interrupt signal to eliminate the cumulative error caused by traditional cycle asynchrony;

[0061] Step S33: Predict the predicted height value h_pred at the next moment based on the motion model: h_pred = h_prev + v_prev × Δt; where, v_prev is the ascending speed of the current aircraft in the z-axis direction;

[0062] Step S34: Linearly weight the predicted height value and the measured height value to calculate the estimated height H:

[0063] H = h_pred + K × (TOF × C / 2 - h_pred),

[0064] C = 331.4 + 0.6T,

[0065] where: TOF is the direct time data for height measurement;

[0066] C is the sound speed model dependent on temperature;

[0067] T is the environmental temperature parameter;

[0068] K is the data trust weight, K = P_pred / (P_pred + R);

[0069] P_pred is the prediction error;

[0070] R is the measurement noise;

[0071] Step S35: Update the prediction error P_pred, and repeat Step S33 - Step S35 continuously for iteration to minimize the prediction error P_pred and achieve forced convergence at low signal-to-noise ratio;

[0072] where, the update formula for the prediction error P_pred is:

[0073] P_pred = (1 - K α )P_pred,

[0074] where: α is the echo quality coefficient, α = SNR / 10;

[0075] SNR is the echo quality index;

[0076] Step S36: Finally, output the optimal height estimate value that resists pulse loss and step noise.

[0077] The present invention is mainly implemented through the following technical solutions:

[0078] An aircraft ultrasonic altimetry system based on dynamic attitude compensation, comprising a communication interface unit, a data processing unit, an ultrasonic transducer unit and a power supply unit, wherein the data processing unit is respectively connected to the communication interface unit, the ultrasonic transducer unit and the power supply unit; the data processing unit is used to implement the above-mentioned aircraft ultrasonic altimetry method based on dynamic attitude compensation.

[0079] A computer-readable storage medium, on which a computer program is stored, and when the program is executed by a processor, it implements the above-mentioned aircraft ultrasonic altimetry method based on dynamic attitude compensation.

[0080] The beneficial effects of the present invention are as follows:

[0081] (1) By integrating multi-axis attitude sensor data, the present invention realizes the adaptive angle compensation of the ultrasonic emission beam under pitch and roll disturbances, providing a reliable height perception guarantee for key tasks such as autonomous obstacle avoidance and precise landing of the aircraft. Based on the aircraft attitude data, the present invention performs real-time compensation on the ultrasonic altimetry data, solves problems such as projection error and data jump caused by the deflection of the ultrasonic ranging axis in complex attitudes of the aircraft, and has good practicability.

[0082] (2) The present invention innovatively defines the echo quality coefficient, and reconstructs the standard covariance update equation into an exponential decay model, realizing forced convergence at low signal-to-noise ratio and maintaining classical characteristics at high signal-to-noise ratio. Secondly, the present invention establishes a strong coupling relationship between the Kalman iteration period Δt and the ultrasonic hardware emission pulse T_pulse, and forcibly aligns the prediction period and the physical echo sampling moment through an interrupt signal, eliminating the cumulative error caused by traditional period asynchrony, and having good practicability.

[0083] (3) When the present invention corrects the height data by integrating multi-axis attitude sensor data, an abnormal data processing mechanism is also introduced, enhancing the stability and robustness of the algorithm, and having good practicability. Description of the Drawings

[0084] Figure 1 It is the schematic diagram of the aircraft ultrasonic altimetry system based on dynamic attitude compensation of the present invention;

[0085] Figure 2 It is the flowchart of the aircraft ultrasonic altimetry method based on dynamic attitude compensation of the present invention;

[0086] Figure 3 It is the flowchart of correcting the original height data h0 in Embodiment 3;

[0087] Figure 4 It is the flowchart of Kalman filtering in Embodiment 3;

[0088] Figure 5The collected original height data h0 and the collection curve graph of the pitch angle and roll angle of the aircraft;

[0089] Figure 6 It is a comparison curve diagram of the collected original height data h0 and the certified reference standard data Href;

[0090] Figure 7 is a comparison curve diagram of the corrected ultrasonic original height h_prev and the certified reference standard data Href;

[0091] Figure 8 This is a comparison curve between the optimal height estimate after Kalman filtering and the certified reference standard data Href. DETAILED DESCRIPTION

[0092] Embodiment 1:

[0093] A method for ultrasonic height measurement of aircraft based on dynamic attitude compensation, such as Figure 2 As shown, the specific working steps of the data processing unit are:

[0094] 1) Emitting ultrasonic pulses: Generate 40-200kHz pulse signals to start a single height measurement cycle;

[0095] 2) Capture ultrasonic signals reflected by the ground, and the signal amplitude decays with the propagation distance;

[0096] 3) Set a dynamic voltage threshold to filter out environmental noise and multiple reflection interference, and trigger the timer to stop only when the echo intensity exceeds the threshold;

[0097] 4) Get the current original height data h0, measure the transmission-reception time difference Δt through a high-precision timer, and calculate the original height data h0=(v_sound×Δt) / 2;

[0098] 5) Combine the attitude sensor angle data (the pitch angle θ and roll angle φ of the aircraft) to perform geometric correction on the original height data h0 to obtain the corrected ultrasonic original height h_prev;

[0099] 6) Combined with the attitude sensor speed data, an estimated height value is generated, and the corrected ultrasonic original height h_prev is processed by Kalman filtering.

[0100] First, the height prediction value is inferred based on the motion model. Then, the Kalman gain is calculated. Finally, the predicted value and the measured value are linearly weighted: optimal height = predicted value + gain × (measured value - predicted value). Continuous iteration is performed to minimize the estimation error variance and achieve dynamic noise suppression.

[0101] Preferably, the data processing unit of the present invention realizes two core architecture innovations within the Kalman framework in view of the characteristics of ultrasonic altimetry, namely pulse asynchrony and step mutation of signal-to-noise ratio:

[0102] 1) Nonlinear covariance attenuator: Define the echo quality coefficient α = SNR / 10 innovatively, and reconstruct the standard covariance update equation into an exponential decay model P_pred=(1-K^α)P_pred, so as to achieve forced convergence at low signal-to-noise ratio (the decay rate increases by 3 times when α < 0.3) and maintain classical characteristics at high signal-to-noise ratio (degenerates into the standard equation when α = 1);

[0103] 2) Ultrasonic clock drive mechanism: Establish a strong coupling relationship between the Kalman iteration period Δt and the ultrasonic hardware emission pulse T_pulse, Δt = 0.7*T_pulse (when v > 2 m / s), and force the alignment of the prediction period and the physical echo sampling moment through the interrupt signal to eliminate the cumulative error caused by traditional period asynchrony.

[0104] Preferably, the specific steps of Kalman filtering are as follows:

[0105] Step 1: Obtain the corrected original ultrasonic height h_prev and the current pulse period T_pulse;

[0106] Step 2: According to the speed threshold, establish a strong coupling relationship between the Kalman iteration period Δt and the ultrasonic hardware emission pulse T_pulse:

[0107] Δt = 0.7*T_pulse,

[0108] Force the alignment of the prediction period and the physical echo sampling moment through the interrupt signal to eliminate the cumulative error caused by traditional period asynchrony.

[0109] Step 3: Predict the height prediction value h_pred = h_prev + v_prev×Δt at the next moment based on the motion model; where v_prev is the rising speed of the current aircraft in the z-axis direction.

[0110] Step 4: Linearly weight the height prediction value and the measured height value to calculate the height estimation value H:

[0111] H = h_pred + K×(TOF×C / 2 - h_pred),

[0112] C = 331.4 + 0.6T,

[0113] Where: TOF is the direct time data for altitude measurement;

[0114] C is the temperature-dependent sound speed model;

[0115] T is the environmental temperature parameter;

[0116] K is the data trust weight, K = P_pred / (P_pred + R);

[0117] P_pred is the prediction error;

[0118] R is the measurement noise.

[0119] Step 5: Update the prediction error P_pred, and repeat Steps 3 - 5, continuously iterate to minimize the prediction error P_pred, and achieve forced convergence at low signal-to-noise ratios;

[0120] Among them, the update formula for the prediction error P_pred is:

[0121] P_pred = (1 - K α )P_pred,

[0122] Among them: α is the echo quality coefficient, α = SNR / 10;

[0123] SNR is the echo quality index.

[0124] Step 6: Finally, output the optimal height estimation value that resists pulse loss and step noise.

[0125] Example 2:

[0126] This example is optimized based on Example 1, and a three-dimensional space compensation algorithm can be used to geometrically correct the original height data h0:

[0127] Based on the principle of orthogonal decomposition of spatial vectors, establish the rotation transformation relationship between the aircraft body coordinate system O-XYZ and the ground coordinate system O-X'Y'Z'. Construct the projection relationship through the pitch angle θ ∈ [-π / 2, π / 2] and the roll angle φ ∈ [-π, π], and orthogonally decompose the ultrasonic beam direction vector V = (0, 0, h0). Finally, the height correction formula is optimized to:

[0128] Compensated height h1 = h0 × cosθ ' × cosφ '

[0129] Among them: θ' is the pitch angle after mean filtering;

[0130] φ' is the roll angle after mean filtering;

[0131] Take the compensated height h1 as the corrected ultrasonic original height h_prev.

[0132] θ' = Σ (w_i × θ_i) / Σw_i, φ' = Σ (w_i × φ_i) / Σw_i; or θ' = Σθ_i / N, φ' = Σφ_i / N.

[0133] Both of the above two methods are mean filtering methods for attitude angles. However, the former is an equal-weight sliding average, and the latter is a weighted average. The filtering strategy is dynamically switched according to the sampling stage to balance real-time performance and accuracy. The former can be understood as the latter with a more complex algorithm.

[0134] Other parts of this embodiment are the same as those of Embodiment 1, so they will not be elaborated here.

[0135] Embodiment 3:

[0136] An ultrasonic altimetry method for an aircraft based on dynamic attitude compensation, as Figure 3 shown, the specific implementation steps for geometric correction of the original height data h0 are as follows:

[0137] 1) Initialize the sampling parameters: Set the threshold i_max of the cyclic sampling times to 8, and the sliding window length N to 5;

[0138] 2) Obtain the original height data h0 = α_k × h_k, where α_k ∈ [0.9, 1.1] is the temperature compensation coefficient; read the pitch angle θ and roll angle φ of the current aircraft;

[0139] θ_i = θ_raw + Δθ,

[0140] φ_i = φ_raw + Δφ,

[0141] where: Δθ, Δφ are the sensor zero-bias compensation values;

[0142] 3) When the sampling times i ≤ i_max, go to step 2); when i > i_max, go to step 4);

[0143] 4) Perform weighted mean filtering on the sampled data of the pitch angle and roll angle:

[0144] θ' = Σ(w_i × θ_i) / Σw_i,

[0145] φ' = Σ(w_i × φ_i) / Σw_i,

[0146] w_i = 0.5(i_max - i);

[0147] 5) Establish beam angle constraints: If |θ'| > θ_max or |φ'| > φ_max, go to step 7), otherwise go to step 6);

[0148] 6) Under normal conditions, perform orthogonal projection calculation to correct the original ultrasonic height h_prev:

[0149] h_prev = h0 × cosθ' × cosφ'.

[0150] 7) Trigger the abnormal correction formula:

[0151] h' = h0 × sec(min(θ', θ_max)) × sec(min(φ', φ_max));

[0152] 8) Based on the anomaly correction result in step 7), median filtering is adopted:

[0153] Compensation height h1 = median{h'(j) × cosθ'(j) × cosφ'(j)}, j ∈ [1, M];

[0154] where: M represents the sliding window length of median filtering, that is, the number of corrected data samples participating in the calculation;

[0155] j is the index value of the samples within the window, used to traverse all M data points.

[0156] j ∈ [1, M] means traversing the results of the most recent M anomaly corrections, that is, the h' values output in step 7);

[0157] For each sample j, the corrected height h'(j) corresponding to it needs to be multiplied by the average attitude angles θ'(j) and φ'(j) within the current window, and finally the median is taken as the filtered output.

[0158] 9) Output the dynamic error correction result: h_prev = h1 × (1 ± σ), σ = 0.01 × |θ'φ'| is the dynamic error factor based on the filtering result in step 8).

[0159] 10) Combine the speed data of the attitude sensor to generate an estimated height value, and perform Kalman filtering on the corrected original ultrasonic height h_prev. As Figure 4 shown, the specific steps of the Kalman filtering are as follows:

[0160] 1) Obtain the original ultrasonic height h_prev and the current pulse period T_pulse;

[0161] 2) Calculate the dynamic step size Δt according to the speed threshold;

[0162] 3) Perform speed prediction to predict the height prediction value at the next moment: h_pred = h_prev + v_prev × Δt;

[0163] 4) Calculate the α value based on the real-time SNR;

[0164] 5) Fuse the TOF measurement value to calculate the height estimation value H:

[0165] H = h_pred + K × (TOF × C / 2 - h_pred),

[0166] C = 331.4 + 0.6T,

[0167] 6) Apply exponential decay to update the covariance: P_pred = (1 - K^α)P_pred; and repeat steps 3) - 6) continuously for iteration to minimize the prediction error P_pred;

[0168] 7) Output the optimal height estimation value that resists pulse loss and step noise.

[0169] The test data analysis is as follows:

[0170] As Figure 5 shown, in the original acquisition curve, the blue curve is the acquisition curve of the original height data, the red curve is the acquisition curve of the pitch angle θ collected by the attitude sensor, and the green curve is the acquisition curve of the roll angle φ collected by the attitude sensor. As Figure 6 shown, compared with the certified reference standard data Href (laser test height), the acquisition curve of the original height data has large fluctuations and large errors. As Figure 7 shown, the relative fluctuations of the geometrically corrected height data are significantly reduced. As Figure 8 shown, after further Kalman filtering, the data curve is relatively smooth and basically consistent with the change of the reference standard data Href, proving that the processing method of the present invention has made remarkable progress.

[0171] The present invention can be applied to various aircraft altimetry scenarios, such as small rotorcraft, helicopters, evtol, fixed-wing aircraft; the present invention can be used in conjunction with multiple ultrasonic altimeters or other data sources, and the reliability of the data is improved after the fusion of multiple data sources.

[0172] Example 4:

[0173] An aircraft ultrasonic altimetry system based on dynamic attitude compensation, as Figure 1 shown, includes a communication interface unit, a data processing unit, an ultrasonic transducer unit, and a power supply unit. The data processing unit is used to implement the above-mentioned aircraft ultrasonic altimetry method based on dynamic attitude compensation.

[0174] 1) Data processing unit: includes a processor, a memory, and an attitude sensor. The processor is used to receive the start altimetry instruction input by the user from the communication interface unit and control the ultrasonic transducer unit to emit ultrasonic pulse signals; when the ultrasonic transducer unit receives the ground reflected echo signal, calculate the height data through threshold judgment and time difference judgment; communicate with the attitude sensor to obtain the current roll and pitch attitude information of the aircraft in real time, and use an algorithm to filter and compensate the height data, and feedback the processed height data to the user through the communication interface unit.

[0175] 2) Communication interface unit: It includes a physical layer and a controller, and the physical layer and the controller are respectively connected to the processor. The controller is used to manage the data transmission between the node and the bus, and the physical layer is used to transmit electrical signals.

[0176] 3) Ultrasonic transducer unit: It includes a transmitting probe, a receiving probe, a transmitting drive circuit, a variable gain amplifier circuit, an adjustable band-pass filter circuit, and a detection circuit. The transmitting drive circuit is used to convert the pulse signal sent by the data processing unit into a high-voltage signal that can drive the piezoelectric ceramic, and send out the ultrasonic signal through the transmitting probe; the receiving probe is used to receive the ground echo, and is processed into an envelope signal that can be used by the data processing unit for threshold judgment through the variable gain amplifier circuit, the adjustable band-pass filter circuit, and the detection circuit in sequence.

[0177] 4) The power supply unit is used to supply power to the data processing unit, the communication interface unit, and the ultrasonic transducer unit.

[0178] As mentioned above, it is only a preferred embodiment of the present invention, and does not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention falls within the protection scope of the present invention.

Claims

1. An ultrasonic altimetry method for an aircraft based on dynamic attitude compensation, characterized in that, It includes the following steps: Step S1: Collect the original height data h0 and obtain the sampled data of the pitch angle and roll angle of the aircraft; Step S2: Correct the original height data h0 based on the pitch angle and roll angle of the aircraft to obtain the corrected ultrasonic original height h_prev; Step S3: Based on the attitude sensor speed data, obtain the height estimation value, perform Kalman filtering on the corrected ultrasonic original height h_prev, and output the optimal height estimation value; Step S31: Obtain the corrected ultrasonic original height h_prev and the current pulse period T_pulse; Step S32: According to the speed threshold, establish a strong coupling relationship between the Kalman iteration period Δt and the ultrasonic hardware emission pulse T_pulse: Δt = 0.7 * T_pulse, Force-align the prediction period and the physical echo sampling moment through the interrupt signal to eliminate the cumulative error caused by the traditional period asynchrony; Step S33: Predict the height prediction value h_pred at the next moment based on the motion model: h_pred = h_prev + v_prev × Δt; where, v_prev is the rising speed of the current aircraft in the z-axis direction; Step S34: Linearly weight the height prediction value and the measured height value to calculate the height estimation value H: H = h_pred + K × (TOF × C / 2 - h_pred), C = 331.4 + 0.6T, where: TOF is the direct time data for height measurement; C is the temperature-dependent sound speed model; T is the environmental temperature parameter; K is the data trust weight, K = P_pred / (P_pred + R); P_pred is the prediction error; R is the measurement noise; Step S35: Update the prediction error P_pred, and repeat steps S33 - S35, continuously iterate to minimize the prediction error P_pred and achieve forced convergence at low signal-to-noise ratio; Among them, the update formula of the prediction error P_pred is: P_pred=(1-K α )P_pred, where: α is the echo quality coefficient, α = SNR / 10; SNR is the echo quality index; Step S36: Finally, output the optimal height estimation value that resists pulse loss and step noise.

2. The ultrasonic altimetry method for an aircraft based on dynamic attitude compensation according to claim 1, wherein The said step S1 includes the following steps: Step S10: Initialize the loop sampling times i_max and set the sliding window length N; Step S11: Collect the original height data h0 and read the pitch angle and roll angle of the current aircraft; Step S12: If the sampling times i exceed the loop sampling times i_max, enter step S13, otherwise enter step S11; Step S13: Perform mean filtering on the sampled data of the pitch angle and roll angle, and enter step S2.

3. The method for ultrasonic altimetry of an aircraft based on dynamic attitude compensation according to claim 2, wherein, In the said step S11, the original height data h0 is: h0 = α_k × h_k, where: α_k is the temperature compensation coefficient, and α_k ∈ [0.9, 1.1]; h_k is the original height sampling value; The read pitch angle and roll angle of the aircraft are: θ_i = θ_raw + Δθ, φ_i = φ_raw + Δφ, where: θ_i is the pitch angle of the aircraft collected for the i-th time; φ_i is the roll angle of the aircraft collected for the i-th time; θ_raw is the reading value of the pitch angle sensor; φ_raw is the reading value of the roll angle sensor; Δθ is the zero-bias compensation value of the pitch angle sensor; Δφ is the zero-bias compensation value of the roll angle sensor.

4. A method for ultrasonic altimetry of an aircraft based on dynamic attitude compensation according to claim 2 or 3, characterized in that In the step S13, after mean filtering processing, we get: θ' = Σ(w_i × θ_i) / Σw_i, φ' = Σ(w_i × φ_i) / Σw_i, w_i = 0.5(i_max - i), where: θ' is the pitch angle after mean filtering; φ' is the roll angle after mean filtering; w_i is the weight coefficient in the weighted mean filtering.

5. A method for ultrasonic altimetry of an aircraft based on dynamic attitude compensation according to claim 1, characterized in that, The step S2 includes the following steps: Step S21: Based on the three-dimensional space compensation correction, correct h0 to obtain the corrected ultrasonic original height h_prev: h_prev = h0 × cosθ' × cosφ', where: θ' is the pitch angle after mean filtering; φ' is the roll angle after mean filtering.

6. The ultrasonic altimetry method for an aircraft based on dynamic attitude compensation according to claim 5, wherein The step S21 includes the following steps: Step A1: Based on the principle of orthogonal decomposition of spatial vectors, establish the rotation transformation relationship between the aircraft body coordinate system O-XYZ and the ground coordinate system O-X'Y'Z'; Step A2: Through the pitch angle θ ∈ [-π / 2, π / 2] and roll angle φ ∈ [-π, π] of the aircraft, construct a projection relationship, and orthogonally decompose the ultrasonic beam direction vector V = (0, 0, h0) to obtain the attitude compensation height h1.

7. A method for ultrasonic altitude measurement of an aircraft based on dynamic attitude compensation according to claim 5 or 6, characterized in that In the step S2, if |θ'| > θ_max or |φ'| > φ_max is not satisfied, then enter step S21; otherwise, enter step S22; the step S2 also includes the following steps: Step S22: Correct the original height data and obtain the abnormal correction height h': h' = h0 × sec(min(θ', θ_max)) × sec(min(φ', φ_max)), where: θ_max is the maximum beam angle of the pitch angle; φ_max is the maximum beam angle of the roll angle; Step S23: Then, perform median filtering processing to obtain the compensation height h1: h1 = median{h'(j) × cosθ'(j) × cosφ'(j)}, j ∈ [1, M], where: M is the sliding window length of the median filtering; j is the index value of the samples within the window, used to traverse all M data points; Step S24: Use dynamic error correction to compensate the height h1 to obtain the corrected ultrasonic original height h_prev as: h_prev = h1 × (1 ± σ), σ = 0.01 × |θ' × φ'|, where: σ is the dynamic error factor.

8. An aircraft ultrasonic altimetry system based on dynamic attitude compensation, characterized in that, It includes a communication interface unit, a data processing unit, an ultrasonic transducer unit, and a power supply unit. The data processing unit is respectively connected to the communication interface unit, the ultrasonic transducer unit, and the power supply unit; the data processing unit is used to implement the aircraft ultrasonic altimetry method based on dynamic attitude compensation according to any one of claims 1-7.

9. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by a processor, it implements the aircraft ultrasonic altimetry method based on dynamic attitude compensation according to any one of claims 1-7.

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