A radio altimeter automatic calibration method

Abstract

The present invention relates to the field of instrument calibration technology, and specifically to a radio altimeter automatic calibration method, comprising the following steps: generating a radio altimeter adaptive calibration result through stability identification, error comparison, mutation detection, and rhythm regulation. In the present invention, based on the quantification of time difference fluctuations and the statistics of variation amplitude, accurate identification of periodic state stability is achieved, the accuracy of ranging result screening is enhanced by limiting the error fluctuation range, a multi-group comparison mechanism with ground reference data is combined to improve the sensitivity and pertinence of error identification, and the dynamic extraction and identification of ranging error mutation rates are superimposed to enhance the ability to capture abnormal ranging behavior in a timely manner. By dynamically adjusting the correction rhythm and performing continuous rate acquisition within a compressed period, the efficiency of judging the recovery trend is improved, the response control process of ranging errors is optimized, and the continuity and adaptability of the altitude calibration process are effectively improved, ensuring stable support for data accuracy in a changing flight environment.

Description

Technical Field

[0001] The present invention relates to the technical field of instrument calibration, and in particular to an automatic calibration method for a radio altimeter. Background Art

[0002] The field of instrument calibration technology involves correcting and adjusting the precision of measuring instruments to ensure the accuracy and reliability of their output data, including measurement deviation identification, error analysis methods, reference standard construction, calibration process setting, etc. Usually, by comparing the difference between the standard signal source and the instrument output signal, the measurement system parameters are corrected with the help of mathematical modeling and numerical fitting to improve the consistency and repeatability of the measurement data. Among them, the traditional radio altimeter calibration method refers to the altitude calibration of the radio altimeter that uses the principle of radio wave reflection to measure the vertical distance between the aircraft and the ground. Usually, the radio altimeter reading is calibrated and adjusted by pre-setting multiple known altitude points, and the static measurement comparison method is adopted or by recording the flight altitude data in the flight test and comparing it with the standard altitude value to complete the calibration process. This process is mainly completed by manual measurement data collection and static reference point construction.

[0003] The existing radio altimeter calibration process mainly relies on manually setting static measurement points and adopting a fixed altitude comparison mode. It lacks the ability to identify and dynamically intervene in the changing trends of continuously sampled data in real time. If echo delay fluctuations or sudden error changes occur during flight, the abnormal data cannot be eliminated and corrected in time, causing the calibration window to be susceptible to interference from discrete data and distortion. Especially in scenarios with frequent terrain changes or sudden changes in flight attitude, the static reference point calibration method has problems of delayed response and reduced accuracy, which in turn affects the timeliness and stability of the overall calibration process. Summary of the Invention

[0004] The purpose of the present invention is to solve the shortcomings in the prior art and to propose a radio altimeter automatic calibration method.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: a radio altimeter automatic calibration method, comprising the following steps:

[0006] S1: Obtain the arrival timestamps of the radio altimeter's echo signals of the current and previous cycles, calculate the cycle time difference, count the change amplitudes of two consecutive segments, compare the response delay fluctuation threshold to determine whether it is stable, and generate the echo delay stability recognition result;

[0007] S2: Based on the echo delay stability identification result, the ranging values ​​within the stable period interval are screened, three sets of ranging values ​​are read and compared with the ground reference data, and the difference is recorded to see whether it falls within the altimeter calibration tolerance band, and the registration data difference comparison result is established;

[0008] S3: Obtain the sampling period corresponding to the sum of two consecutive ranging values, calculate the ranging error mutation rate per unit time, and if it is greater than the error mutation identification threshold, identify the current period as a mutation trigger point and add an alarm flag to form a ranging mutation rate identification record;

[0009] S4: Based on the ranging mutation rate identification record, if there is an alarm sign, compress the period and continuously collect three ranging error rates. If the average values ​​are all lower than the stable recovery threshold, restore the original correction rhythm configuration and establish a calibration rhythm recovery judgment result;

[0010] S5: Combining the calibration rhythm recovery judgment result and the registration data difference comparison result, determining whether the current cycle is a correction trigger state, analyzing whether to perform error correction, and generating a radio altimeter adaptive calibration result.

[0011] As a further solution of the present invention, the echo delay stability identification result includes a time difference stability flag, a variation amplitude statistical value, and a Doppler tolerance comparison conclusion; the alignment data difference comparison result includes a ranging difference distribution record, a terrain reference offset mapping result, and an out-of-tolerance identification label; the ranging mutation rate identification record includes an error mutation rate value, a mutation cycle index, and a RAIM alarm flag; the calibration rhythm recovery judgment result includes an error rate mean judgment result and a stable state confirmation flag; and the radio altimeter adaptive calibration result includes a correction trigger state judgment result, a calibration window update control record, and error correction output data.

[0012] As a further solution of the present invention, the response delay fluctuation threshold is a Doppler tolerance, the ground reference data is obtained through a terrain reference database, and the warning sign is a RAIM warning sign.

[0013] As a further solution of the present invention, the specific steps for obtaining the echo delay stability identification result are:

[0014] S111: Obtain the arrival timestamps of the echo signals of the current cycle and the previous cycle of the radio altimeter, calculate the difference between the two cycle timestamps, arrange them in a time series, and extract the change amplitude between the two adjacent time differences to generate a periodic change amplitude sequence;

[0015] S112: comparing each set of continuous change amplitudes based on two consecutive change amplitudes in the periodic change amplitude sequence to see whether they are all less than a response delay fluctuation threshold, thereby obtaining a continuous change amplitude comparison record;

[0016] S113: According to the continuous change amplitude comparison record, determine whether all the continuous data groups meet the fluctuation threshold limit condition. If so, mark the periodic state as having stability and generate an echo delay stability identification result.

[0017] As a further solution of the present invention, the specific steps for obtaining the registration data difference comparison result are:

[0018] S211: Based on the echo delay stability identification result, filter the period index interval marked as stable, obtain the ranging value in the corresponding period, write the data window structure in the corresponding sampling time sequence, do not adjust the recording time sequence, only perform the index mapping operation, and generate the data window ranging sequence;

[0019] S212: extracting three sets of ranging values ​​according to the index position in the ranging sequence of the data window, reading the corresponding three sets of ground reference data with the same sampling time, calculating the difference between the ranging values ​​and the corresponding reference data, and generating a ranging reference difference value group;

[0020] S213: Based on each set of difference values ​​in the ranging reference difference value group, determine whether it is within the altimeter calibration tolerance range item by item, convert each judgment result into a status mark value, and count the sequence composed of all mark values ​​to establish the registration data difference comparison result.

[0021] As a further solution of the present invention, the specific steps for obtaining the ranging mutation rate identification record are:

[0022] S311: Obtain the ranging values ​​under two consecutive sampling periods and calculate the difference. Combined with the sampling time interval between the two periods, calculate the ranging error change rate per unit time for all periodic data in turn to obtain the ranging mutation rate sequence;

[0023] S312: Compare each rate value in the ranging mutation rate sequence with the dynamic error rate threshold item by item to determine whether there is a periodic point with a rate value greater than the dynamic error rate threshold, and add a mark state to the periodic point that meets the condition to obtain a mutation period mark sequence;

[0024] S313: Extract the corresponding sampling timestamp according to the period position of the trigger state in the mutation period mark sequence, and write the alarm flag into the data structure in combination with the mutation state of each period, synchronously record the corresponding timestamp information, and establish the ranging mutation rate identification record.

[0025] As a further solution of the present invention, when the alarm flag is written, the flag is 0 if the trigger period corresponds to the trigger period, otherwise it is 1.

[0026] As a further solution of the present invention, the specific steps for obtaining the calibration rhythm recovery judgment result are:

[0027] S411: Based on the ranging mutation rate identification record, searching for a record in which a periodic point status is marked as an alarm; if so, calculating a compressed period value, setting a sampling rhythm based on the compressed period, and establishing compressed rhythm sampling period data;

[0028] S412: Based on the compressed rhythm sampling period data, three ranging error rate values ​​are collected within a set continuous time range, an average of the three error rates is calculated, and an average is compared with a stable recovery threshold to determine whether it is lower than the stable recovery threshold, thereby obtaining a stable trend state marking result;

[0029] S413: According to the stable trend state marking result, if the continuous sampling values ​​are all lower than the stable recovery threshold, the correction rhythm is restored to the originally set period value, and the period index and time information corresponding to the recovery operation are synchronously recorded to establish the calibration rhythm recovery judgment result.

[0030] As a further solution of the present invention, the specific steps for obtaining the adaptive calibration result of the radio altimeter are:

[0031] S511: Based on the calibration rhythm recovery judgment result and the recovery state flag value corresponding to the current cycle in the registration data difference comparison result and the difference comparison state, determine whether the current cycle simultaneously meets the two conditions of unestablished recovery rhythm and registration difference exceeding the altimeter calibration tolerance band; if both conditions are met, mark the current cycle as a correction trigger state, and obtain a correction trigger cycle flag record;

[0032] S512: Determine whether the current cycle is a marked cycle based on the correction trigger cycle mark record. If so, suspend the update operation of the historical comparison data in the registration window, retain the ranging error data of the current cycle, and calculate the error correction value based on the ground reference height data within the current cycle to generate current error correction data.

[0033] S513: Based on the coordination status of the current error correction data and the correction trigger cycle mark record, if the current cycle is not in the correction state, the registration data difference comparison operation is performed and the correction offset trend is recorded; if the current cycle is in the correction state, the error correction value is used to update the radio altimeter reading and establish the radio altimeter adaptive calibration result.

[0034] As a further solution of the present invention, the error correction value adopts the formula:

[0035] ;

[0036] Calculate and characterize the correction value of the current cycle under the correction trigger, where: Indicates the error correction value in the current cycle, in meters. Indicates the ground reference height corresponding to the current period sampling moment, in meters. Indicates the ranging output value of the radio altimeter during the current sampling period, in meters. Indicates the ranging reference difference of the current cycle, calculated as , in meters, It represents the arithmetic mean of the ranging reference differences corresponding to all trigger correction cycles within the current correction window, in meters. and Respectively represent the rhythm recovery judgment status mark value of the previous cycle and the previous two cycles, with a value of 0 or 1. Indicates the degree of change in the rhythm judgment state.

[0037] Compared with the prior art, the advantages and positive effects of the present invention are:

[0038] In the present invention, based on the quantification of time difference fluctuations and the statistics of variation amplitude, accurate identification of periodic state stability is achieved, the screening accuracy of ranging results is enhanced by limiting the error fluctuation range, and combined with a multi-group comparison mechanism with ground reference data, the sensitivity and pertinence of error identification are improved. The dynamic extraction and identification of the mutation rate of ranging errors are superimposed to enhance the ability to capture abnormal ranging behaviors in a timely manner. By dynamically adjusting the correction rhythm and executing continuous rate acquisition within a compressed period, the efficiency of judging the recovery trend is improved, the response control process of ranging errors is optimized, the continuity and adaptability of the altitude calibration process are effectively improved, and stable support for data accuracy in a variable flight environment is ensured. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a schematic diagram of the steps of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0041] In the description of the present invention, it should be understood that the terms "length," "width," "up," "down," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inside," "outside," and the like, indicating positions or relationships, are based on the positions or relationships shown in the accompanying drawings and are intended only to facilitate the description of the present invention and simplify the description. They do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, in the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

[0042] See also Figure 1 , a radio altimeter automatic calibration method, comprising the following steps:

[0043] S1: Obtain the arrival timestamps of the radio altimeter's echo signals for the current and previous cycles, calculate the cycle time difference, count the change amplitudes of two consecutive segments, and compare whether they are both less than the response delay fluctuation threshold (Doppler tolerance, in compliance with the time jitter requirements of Article 4.3.2.3 of the standard). If the conditions are met, the cycle state is determined to be stable and an echo delay stability identification result is generated.

[0044] S2: Based on the echo delay stability identification results, the ranging values ​​within the stable period are screened and written into the data window in the order of ranging value sampling time. The three sets of ranging values ​​in the window are read and compared one by one with the ground reference data (using the terrain reference database of the EGNOS satellite augmentation system). It is recorded whether the difference falls within the altimeter calibration tolerance band (±0.3 meters set according to EUROCAEED-54) and the registration data difference comparison results are established.

[0045] S3: Obtain the difference between two consecutive ranging values ​​and divide it by the corresponding sampling period. Calculate the ranging error mutation rate per unit time and compare it with the dynamic error rate threshold (set to 0.5m / s² according to SAEAS8006). If it is greater than the error mutation identification threshold, identify the current period as a mutation trigger point and add an alarm flag (RAIM alarm flag, in compliance with integrity monitoring requirements). Simultaneously record the current period timestamp to form a ranging mutation rate identification record.

[0046] S4: Based on the ranging mutation rate identification record, if there is an alarm sign, the next correction check rhythm is compressed to half of the current sampling period. The ranging error rate is continuously collected three times within the compressed period, and the average value is calculated and compared with the stability recovery threshold (determined according to the ARINC707 altimeter specification). If both are lower than the stability recovery threshold, the original correction rhythm configuration is restored and the calibration rhythm recovery judgment result is established;

[0047] S5: Comprehensively compare the calibration rhythm recovery judgment result and the registration data difference comparison result to determine whether the current cycle is in the correction trigger state. If so, suspend the registration window update and only perform the error correction calculation under the current cycle; if not, continue the ground reference registration operation to generate the radio altimeter adaptive calibration result.

[0048] The echo delay stability identification results include the time difference stability mark, the variation amplitude statistics, and the Doppler tolerance comparison conclusion. The registration data difference comparison results include the ranging difference distribution record, the terrain reference offset mapping result, and the out-of-tolerance identification label. The ranging mutation rate identification record includes the error mutation rate value, the mutation cycle index, and the RAIM alarm mark. The calibration rhythm recovery judgment result includes the error rate mean judgment result and the stable state confirmation mark. The radio altimeter adaptive calibration result includes the correction trigger state judgment result, the calibration window update control record, and the error correction output data.

[0049] The specific steps of S1 are:

[0050] S111: Obtain the arrival timestamps of the echo signals of the current cycle and the previous cycle of the radio altimeter, calculate the difference between the two cycle timestamps, arrange them in a time series, and extract the change amplitude between the two adjacent time differences to generate a periodic change amplitude sequence;

[0051] In practical applications, in order to obtain the echo stability of the radio altimeter, it is necessary to extract the timestamp of the arrival of the main peak of the echo signal from each cycle and record it as the timestamp of the current cycle. Timestamp of the previous cycle , for example, 、 , then the difference between the two can be calculated as By performing this difference calculation operation on all consecutive period timestamps in the entire sampling process, a period time difference sequence arranged in chronological order can be obtained. Then, the cycle-to-cycle variation of the sequence is extracted by traversing three sliding windows, extracting the difference between the current and previous period in each group, performing absolute difference calculation, and obtaining the variation amplitude. ,like 、 ,but , and process them in sequence to obtain the periodic variation amplitude sequence , for example, suppose the analog signal time series is: , then we can get , and further obtain the change range as , this sequence will serve as the basis for subsequent stability judgment.

[0052] S112: comparing the values ​​of two consecutive change amplitudes in the periodic change amplitude sequence to see whether each group of continuous change amplitudes is less than the response delay fluctuation threshold, thereby obtaining a continuous change amplitude comparison record;

[0053] In the obtained periodic variation amplitude sequence It is necessary to construct a comparison sequence of two consecutive amplitude values ​​to identify whether the fluctuation range is within the system allowable range. Suppose any two consecutive amplitude values ​​are and , perform amplitude judgment operation on it, requiring the comparison conditions to be met ,in For the response delay fluctuation threshold, refer to the system response error range of the radio altimeter and take the maximum allowable fluctuation error as ±25 microseconds, then set , with instance value For example, judge and Established, mark this group of comparison records as If any amplitude value does not meet the condition, it is marked as ,like , then the group comparison is , by traversing the entire amplitude sequence to generate a comparison record sequence , each comparison record , which is used to reflect whether the amplitude of periodic changes is within the allowable fluctuation range and serves as the core basis for the next step of stability identification.

[0054] S113: comparing the records based on the continuous change amplitude, determining whether all the continuous data groups meet the fluctuation threshold limit condition; if so, marking the periodic state as having stability, and generating an echo delay stability identification result;

[0055] In the obtained comparison record sequence In order to determine whether the echo delay has reached a stable state, a sliding window of fixed length needs to be constructed to identify the subsequences of comparisons that continuously meet the conditions. The window length is set to , each time a subsequence is extracted , if all records in the subsequence are , then the period is judged to meet the stability condition and the corresponding period state is marked as stable. In the example, if the comparison record is

[0056] , then the window Meet the stability standard and mark the cycle number accordingly The state is stable, and the subsequent sliding window continues to advance to the right until the end of the sequence. Finally, all the period numbers or their corresponding timestamps that meet the conditions are recorded and summarized to form a stable period identification sequence. ,in Indicates that the cycle is stable. Indicates instability, and the sequence is used as a reference input for the system to subsequently identify the credibility of periodic signals.

[0057] The specific steps of S2 are:

[0058] S211: Based on the echo delay stability identification result, filter the period index interval marked as stable, obtain the ranging value in the corresponding period, write it into the data window structure in the corresponding sampling time sequence, do not adjust the recording time sequence, only perform the index mapping operation, and generate the data window ranging sequence;

[0059] Based on the echo delay stable recognition result, we first need to extract the state marked as All period indexes , which constitutes a stable period index set , where each Corresponding to a specific cycle number or timestamp index, the original ranging sequence is then called according to the index set Extract the corresponding elements in one by one Construct a new ranging subsequence The extraction process is strictly based on the index position, without any adjustment of the time sequence, and only records in sequence in the data window structure to ensure that the recording time corresponds to the original sampling time sequence. Suppose the original ranging sequence is , if the stable period index set is , then the data window ranging sequence is ,This data window structure construction process only involves index mapping,,without interpolation or filtering, and finally generates a data window ranging,sequence arranged in time order.

[0060] S212: Based on the three sets of ranging values ​​extracted according to the index position in the ranging sequence of the data window, and reading the corresponding three sets of ground reference data with the same sampling time (read from the terrain reference database), calculate the difference between the ranging values ​​and the corresponding reference data one by one to generate a ranging reference difference value group;

[0061] Ranging sequence according to data window , according to the index position corresponding to each item, call the ground reference data corresponding to its sampling time in the terrain reference database , the two correspond one to one, and the data format is the height value in meters, which is recorded as the distance value Corresponding ground height reference value , perform one-by-one difference calculation operation, the calculation formula is: , the difference results constitute the ranging reference difference group , using a practical example, if the data window ranging sequence is , and its corresponding reference height is , then we can get:

[0062] , and finally generate the ranging benchmark difference group , which serves as the basis for subsequent altimeter error calibration judgment.

[0063] S213: Based on each set of difference values ​​in the ranging reference difference value group, determine whether it is within the altimeter calibration tolerance band (±0.3 meters set according to EUROCAEED-54), convert each judgment result into a status mark value, and calculate the sequence composed of all mark values ​​to establish the registration data difference comparison result;

[0064] According to the distance measurement reference difference group , for each difference Perform the tolerance zone judgment operation and set the altimeter error tolerance zone to ±0.3 meters. According to the EUROCAEED-54 standard, the judgment conditions are: , judge whether each difference meets the interval limit item by item, and mark the one that meets the condition as the status value , otherwise it is recorded as , and finally obtain the registration state mark sequence , combined with the difference group in the previous example , judge item by item: , so the state sequence is , if any of the differences exceeds ±0.3 meters, for example , then the corresponding ,The final statistical comparison result consisting of the state tag value sequence is used to feedback the difference alignment between the altimeter data and the terrain reference data.

[0065] The specific steps of S3 are:

[0066] S311: Obtain the ranging values ​​under two consecutive sampling periods and calculate the difference. Combined with the sampling time interval between the two periods, calculate the ranging error change rate per unit time for all periodic data in turn to obtain the ranging mutation rate sequence;

[0067] To obtain the ranging values ​​under two consecutive sampling periods, the original ranging data sequence needs to be called , and for each pair of continuous distance values Perform difference operation, the calculation method is: , while from the system time series Get the corresponding sampling timestamp difference , perform rate calculation operations and define the ranging mutation rate is the rate of change of ranging error per unit time, that is: , need to go through one by one arrive All period indexes of complete the construction of the entire rate sequence to form a ranging mutation rate sequence For example, if there is ,but:

[0068] , the same calculation is performed on all cycles through the above operations, and finally a complete ranging mutation rate sequence is generated , used for subsequent outlier detection.

[0069] S312: Compare each rate value in the ranging mutation rate sequence with the dynamic error rate threshold (set to 0.5 m / s²) to determine whether there is a periodic point with a rate value greater than the dynamic error rate threshold. Mark the periodic points that meet the condition to obtain a mutation period mark sequence.

[0070] According to the distance mutation rate sequence , you need to set the dynamic error rate threshold , the maximum allowable rate change of the reference system's response to transient mutation is set to , for each rate value in the sequence Perform judgment operations to compare whether the following conditions are met: If the condition is met, mark the cycle index The state is triggered, and the state value is recorded as , otherwise it is recorded as , forming a mutation cycle marker sequence , calculated in the previous example For example, compared with the threshold , if a certain rate is , then judge In this way, the entire rate sequence is traversed and a complete mark sequence is formed for subsequent abnormal alarm flag setting.

[0071] S313: Extract the corresponding sampling timestamp based on the period position of the trigger state in the mutation period mark sequence, and write the RAIM alarm flag into the data structure in combination with the mutation state of each period. Simultaneously record the corresponding timestamp information to establish the ranging mutation rate identification record.

[0072] Labeling sequences according to mutation cycles , extract all the cycle index positions where the state is triggered, that is, satisfy All Composition set , and then according to the index position from the sampling timestamp sequence Extract the corresponding timestamp value , and then for each index in the data structure Add RAIM alarm flag and set alarm flag , the corresponding flags of the other untriggered cycles are , forming a RAIM state flag sequence , for example, if , corresponding to the timestamp , then the RAIM flag sequence is ,Finally, the flag sequence and the corresponding timestamp information are synchronously written into the recognition result structure,,establishing a complete ranging mutation rate recognition record.

[0073] The specific steps of S4 are:

[0074] S411: Based on the ranging mutation rate identification record, whether there is a record with the periodic point status marked as RAIM alarm is searched, and if so, the compressed period value is calculated (the original corrected rhythm period is divided by 2), and the sampling rhythm is set based on the compressed period to establish the compressed rhythm sampling period data;

[0075] Identifying records based on ranging mutation rates First, check whether the status flags exist. The periodic point, that is, whether there is a RAIM alarm cycle, once a trigger state point is identified, such as , then the compression rhythm reset process is triggered, and the current correction rhythm cycle value needs to be called , perform compression operation and get the compression cycle value , if the original rhythm period is , then the compression period is , then the sampling rhythm needs to be reset to is the period step, starting after the current trigger period, to build a new time series , set the starting point to the RAIM alarm time , then the compression rhythm sampling point is , based on this, the compressed rhythm sampling period data is established for subsequent high frequency detection and judgment.

[0076] S412: Based on the compressed rhythm sampling period data, three ranging error rate values ​​are collected within a set continuous time range. The average of the three error rates is calculated and compared with the stability recovery threshold (determined according to the ARINC707 altimeter specification) to determine whether it is lower than the stability recovery threshold, and a stable trend state flag result is obtained;

[0077] Sampling periodic time series according to the established compression rhythm , it is necessary to extract three consecutive sampling moments within a fixed continuous time range (for example, within 0.06 seconds) , call the ranging value , perform two sets of mutation rate calculations, assuming: , , calculate the average of the three error rates: , then read the stability recovery threshold , refer to ARINC707 specification, set , the judgment condition is If the condition is met, the current data segment is marked as having a stable trend state, and the state mark value , otherwise , for example, if , ,but: , the status mark is , on the contrary, if the ranging difference is only 0.01 meters, the average rate is , the recovery condition is still not met until the continuous value meets the judgment condition and the stable trend state mark result sequence is output.

[0078] S413: Based on the stable trend state marking result, if the consecutive sampling values ​​are all lower than the stable recovery threshold, the corrected rhythm is restored to the originally set period value, and the period index and time information corresponding to the restoration operation are synchronously recorded to establish the calibration rhythm restoration judgment result;

[0079] Label the resulting series according to the stable trend status , it is necessary to identify whether there are multiple consecutive mark values ​​1, and it is required that the status of three consecutive sampling points meets If the condition is met, the system is judged to have recovered to a stable state, and the current rhythm cycle is immediately reset to the original modified rhythm cycle after the judgment period is met. , and the trigger cycle index corresponding to the operation Its sampling timestamp Record together, for example, if the stable sequence is , the corresponding time is , then judge in When the continuous recovery condition is met, the rhythm cycle recovery operation is performed and the recovery index value is recorded as 4 and the time is 1.66 seconds. Finally, the recovery rhythm cycle value is updated to , and write the rhythm recovery judgment result structure for use in subsequent rhythm control strategies.

[0080] The specific steps of S5 are:

[0081] S511: Based on the calibration rhythm recovery judgment result and the registration data difference comparison result, the recovery state flag value corresponding to the current cycle and the difference comparison state are determined to determine whether the current cycle simultaneously satisfies the two conditions of unestablished recovery rhythm and registration difference exceeding the altimeter calibration tolerance band. If both conditions are met, the current cycle is marked as a correction trigger state, and a correction trigger cycle flag record is obtained.

[0082] Recover the judgment result based on the calibration rhythm Comparison results with the registration data , for the current cycle index To perform the joint judgment operation, the following two conditions must be met at the same time: First, the recovery rhythm state is not established, that is, , the second is that the current cycle registration difference exceeds the error band, that is , the judgment condition expression is: If the condition is met, the current cycle Added correction trigger period index set , and establish a modified trigger cycle marking sequence ,in Indicates that the cycle triggers a correction, Indicates that no correction has been triggered. For example, if hour, ,but If any one of the items is not satisfied, then , and finally form a complete correction trigger cycle marking record.

[0083] S512: Determine whether the current cycle is a marked cycle based on the correction trigger cycle mark record. If so, suspend the update operation of the historical comparison data in the registration window, retain the ranging error data of the current cycle, and calculate the error correction value based on the ground reference height data within the current cycle to generate current error correction data.

[0084] Error correction value, using the formula:

[0085] ;

[0086] Calculate and characterize the correction value of the current cycle under the correction trigger, where: Indicates the error correction value in the current cycle, in meters. Indicates the ground reference height corresponding to the current period sampling moment, in meters. Indicates the ranging output value of the radio altimeter during the current sampling period, in meters. Indicates the ranging reference difference of the current cycle, calculated as , in meters, It represents the arithmetic mean of the ranging reference differences corresponding to all trigger correction cycles within the current correction window, in meters. and Respectively represent the rhythm recovery judgment status mark value of the previous cycle and the previous two cycles, with a value of 0 or 1. Indicates the change amplitude of the rhythm judgment state, which is used to reflect the impact of rhythm fluctuations and ultimately generate the current error correction data.

[0087] : The base height (unit: meter) read from the ground database for the current period. The acquisition method is to match the period time by GPS index in the pre-installed terrain database and extract the corresponding elevation, such as: the GPS corresponding point (longitude 113.9637, latitude 22.5421) m;

[0088] : The original distance value (unit: meter) measured by the radio altimeter in the current cycle, read by the device sampling module, for example, the reading in the cycle is m;

[0089] : The distance measurement reference difference of the current cycle, calculated as m;

[0090] : The average value of all error differences in the historical correction period (unit: meter). Assume that there are three trigger periods in the current window, namely ,but:

[0091] ;

[0092] : The rhythm recovery status flag value of the previous cycle and the previous two cycles comes from the system rhythm judgment module. If there is no rhythm recovery event in the previous two cycles, then , the absolute value of the difference is ;

[0093] Table 1 Ranging Correction Calculation Parameters

[0094]

[0095] As shown in Table 1, the main input parameters involved in the calculation of this correction value are listed, all of which are derived from real-time sampling data or historical comparison results.

[0096] Substituting the above parameters into the formula:

[0097] ;

[0098] The results show that the current period error correction value is This value is equal to the upper limit of ±0.3m set by the EUROCAEED-54 altimeter calibration tolerance band, indicating that the current cycle is in a boundary deviation state. It is necessary to execute the periodic correction process and lock the current ranging error value for subsequent alignment correction.

[0099] The error correction value refers to the numerical adjustment calculated for adaptive calibration of the radio altimeter ranging data within a specific sampling period. This value is based on the actual ranging error of the current period, combined with its deviation from the historical error mean, and introduces the regulatory influence of the system rhythm change state. It is used to measure the systematic or instantaneous deviation between the current ranging value and the ground reference altitude, thereby providing a basis for whether the original ranging reading of the period needs to be numerically corrected. This correction value essentially reflects the degree of distance difference between the ranging result under the current system state and the ideal reference state. It is the direct decision-making basis for whether and how to update the subsequent altimeter output data. The larger the value, the more serious the deviation of the current reading from the true ground altitude, and the closer it is to zero, the more consistent the current measurement is with the ground reference.

[0100] The formula adds the absolute error term of the current cycle to the error term. Deviation from the historical average The combination reflects the joint effect of the instantaneous value of the current ranging error and the trend deviation, where the former represents the actual measurement error and the latter is used to measure the deviation amplitude of the current error in the overall fluctuation background; the additive structure enables the correction value to quickly respond to instantaneous anomalies while taking into account historical consistency, eliminating the influence of the error direction through absolute value calculation, ensuring that the amplitude intensity is processed regardless of the deviation direction; the square root operation in the denominator is based on the influencing factors of the rhythm recovery state jump, and is used A nonlinear suppression mechanism is constructed. When the system rhythm does not change (i.e., the state is stable), the denominator is 1, and the correction amplitude is not suppressed. When the rhythm changes (for example, from 0 to 1), the denominator becomes larger, thereby compressing the overall correction value, achieving the purpose of slowing down over-correction. The introduction of the square root avoids the problem of linear scaling being allergic to the correction result, so that the entire correction behavior logically maintains flexible adaptability to rhythm fluctuations. In summary, the operators have clear division of labor in the structure, integrating the error source through linear addition, controlling the response intensity through nonlinear normalization, and using absolute values ​​to ensure that the result is used for amplitude processing of system correction, forming a composite correction logic that takes into account the error amplitude, direction and rhythm dynamics.

[0101] S513: Based on the matching status of the current error correction data and the correction trigger period mark record, if the current period is not in the correction state, performing a registration data difference comparison operation and recording the correction offset trend; if the current period is in the correction state, using the error correction value to update the radio altimeter reading, and establishing the radio altimeter adaptive calibration result;

[0102] According to the correction status of the current cycle Corresponding correction data , execute status branch judgment, if , that is, it is not in the correction state, then enter the registration data difference comparison process and update the difference group Corresponding elements , and record the difference relative to the previous period The changing trend of , that is, the record correction offset direction is: ,like Indicates that the offset increases. If Indicates that the offset is reduced. If , that is, if the current cycle is in the correction state, the correction value calculated in the previous cycle is used Adjusting the original range value, the updated radio altimeter reading is: , continue to explain with actual data, if ,but The correction value is written into the updated altimeter data stream and synchronously written into the calibration result record structure to complete the radio altimeter adaptive calibration operation.

[0103] The above are merely preferred embodiments of the present invention and do not limit the present invention in any other form. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A radio altimeter automatic calibration method, characterized in that: The following steps are involved: S1: Obtain the arrival timestamps of the radio altimeter's echo signals of the current and previous cycles, calculate the cycle time difference, count the change amplitudes of two consecutive segments, compare the response delay fluctuation threshold to determine whether it is stable, and generate the echo delay stability recognition result; S2: Based on the echo delay stability identification result, the ranging values ​​within the stable period interval are screened, three sets of ranging values ​​are read and compared with the ground reference data, and the difference is recorded to see whether it falls within the altimeter calibration tolerance band, and the registration data difference comparison result is established; S3: Obtain the sampling period corresponding to the sum of two consecutive ranging values, calculate the ranging error mutation rate per unit time, and if it is greater than the error mutation identification threshold, identify the current period as a mutation trigger point and add an alarm flag to form a ranging mutation rate identification record; S4: Based on the ranging mutation rate identification record, if there is an alarm sign, compress the period and continuously collect three ranging error rates. If the average values ​​are all lower than the stable recovery threshold, restore the original correction rhythm configuration and establish a calibration rhythm recovery judgment result; S5: Combining the calibration rhythm recovery judgment result and the registration data difference comparison result, determining whether the current cycle is a correction trigger state, analyzing whether to perform error correction, and generating a radio altimeter adaptive calibration result.

2. The radio altimeter automatic calibration method according to claim 1, characterized in that: The echo delay stability identification result includes a time difference stability flag, a variation amplitude statistic, and a Doppler tolerance comparison conclusion; the registration data difference comparison result includes a ranging difference distribution record, a terrain reference offset mapping result, and an out-of-tolerance identification label; the ranging mutation rate identification record includes an error mutation rate value, a mutation cycle index, and a RAIM alarm flag; the calibration rhythm recovery judgment result includes an error rate mean judgment result and a stable state confirmation flag; and the radio altimeter adaptive calibration result includes a correction trigger state judgment result, a calibration window update control record, and error correction output data.

3. The radio altimeter automatic calibration method according to claim 1, characterized in that: The response delay fluctuation threshold is a Doppler tolerance, the ground reference data is obtained through a terrain reference database, and the warning sign is a RAIM warning sign.

4. The radio altimeter automatic calibration method according to claim 1, characterized in that: The specific steps for obtaining the echo delay stability identification result are: S111: Obtain the arrival timestamps of the echo signals of the current cycle and the previous cycle of the radio altimeter, calculate the difference between the two cycle timestamps, arrange them in a time series, and extract the change amplitude between the two adjacent time differences to generate a periodic change amplitude sequence; S112: comparing each set of continuous change amplitudes based on two consecutive change amplitudes in the periodic change amplitude sequence to see whether they are all less than a response delay fluctuation threshold, thereby obtaining a continuous change amplitude comparison record; S113: According to the continuous change amplitude comparison record, determine whether all the continuous data groups meet the fluctuation threshold limit condition. If so, mark the periodic state as having stability and generate an echo delay stability identification result.

5. The radio altimeter automatic calibration method according to claim 1, characterized in that: The specific steps for obtaining the registration data difference comparison result are: S211: Based on the echo delay stability identification result, filter the period index interval marked as stable, obtain the ranging value in the corresponding period, write the data window structure in the corresponding sampling time sequence, do not adjust the recording time sequence, only perform the index mapping operation, and generate the data window ranging sequence; S212: extracting three sets of ranging values ​​according to the index position in the ranging sequence of the data window, reading the corresponding three sets of ground reference data with the same sampling time, calculating the difference between the ranging values ​​and the corresponding reference data, and generating a ranging reference difference value group; S213: Based on each set of difference values ​​in the ranging reference difference value group, determine whether it is within the altimeter calibration tolerance range item by item, convert each judgment result into a status mark value, and count the sequence composed of all mark values ​​to establish the registration data difference comparison result.

6. The radio altimeter automatic calibration method according to claim 1, characterized in that: The specific steps for obtaining the ranging mutation rate identification record are: S311: Obtain the ranging values ​​under two consecutive sampling periods and calculate the difference. Combined with the sampling time interval between the two periods, calculate the ranging error change rate per unit time for all periodic data in turn to obtain the ranging mutation rate sequence; S312: Compare each rate value in the ranging mutation rate sequence with the dynamic error rate threshold item by item to determine whether there is a periodic point with a rate value greater than the dynamic error rate threshold, and add a mark state to the periodic point that meets the condition to obtain a mutation period mark sequence; S313: Extract the corresponding sampling timestamp according to the period position of the trigger state in the mutation period mark sequence, and write the alarm flag into the data structure in combination with the mutation state of each period, synchronously record the corresponding timestamp information, and establish the ranging mutation rate identification record.

7. The radio altimeter automatic calibration method according to claim 6, characterized in that: When the alarm flag is written, the flag is 0 if the trigger period corresponds to the trigger period, otherwise it is 1.

8. The radio altimeter automatic calibration method according to claim 1, characterized in that: The specific steps for obtaining the calibration rhythm recovery judgment result are: S411: Based on the ranging mutation rate identification record, searching for a record in which a periodic point status is marked as an alarm; if so, calculating a compressed period value, setting a sampling rhythm based on the compressed period, and establishing compressed rhythm sampling period data; S412: Based on the compressed rhythm sampling period data, three ranging error rate values ​​are collected within a set continuous time range, an average of the three error rates is calculated, and an average is compared with a stable recovery threshold to determine whether it is lower than the stable recovery threshold, thereby obtaining a stable trend state marking result; S413: According to the stable trend state marking result, if the continuous sampling values ​​are all lower than the stable recovery threshold, the correction rhythm is restored to the originally set period value, and the period index and time information corresponding to the recovery operation are synchronously recorded to establish the calibration rhythm recovery judgment result.

9. The radio altimeter automatic calibration method according to claim 1, characterized in that: The specific steps for obtaining the radio altimeter adaptive calibration result are: S511: Based on the calibration rhythm recovery judgment result and the recovery state flag value corresponding to the current cycle in the registration data difference comparison result and the difference comparison state, determine whether the current cycle simultaneously meets the two conditions of unestablished recovery rhythm and registration difference exceeding the altimeter calibration tolerance band; if both conditions are met, mark the current cycle as a correction trigger state, and obtain a correction trigger cycle flag record; S512: Determine whether the current cycle is a marked cycle based on the correction trigger cycle mark record. If so, suspend the update operation of the historical comparison data in the registration window, retain the ranging error data of the current cycle, and calculate the error correction value based on the ground reference height data within the current cycle to generate current error correction data. S513: Based on the coordination status of the current error correction data and the correction trigger cycle mark record, if the current cycle is not in the correction state, the registration data difference comparison operation is performed and the correction offset trend is recorded; if the current cycle is in the correction state, the error correction value is used to update the radio altimeter reading and establish the radio altimeter adaptive calibration result.

10. The radio altimeter automatic calibration method according to claim 9, characterized in that: The error correction value is calculated using the formula: ； Calculate and characterize the correction value of the current cycle under the correction trigger, where: Indicates the error correction value in the current cycle, Indicates the ground reference height corresponding to the current period sampling moment, in meters. Indicates the ranging output value of the radio altimeter during the current sampling period. Indicates the ranging reference difference of the current cycle, calculated as , It represents the arithmetic mean of the ranging reference differences corresponding to all trigger correction cycles within the current correction window, in meters. and Respectively represent the rhythm recovery judgment status mark value of the previous cycle and the previous two cycles, with a value of 0 or 1. Indicates the degree of change in the rhythm judgment state.

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