Beidou priority multimode positioning method and system based on signal feature comparison

Abstract

The invention discloses a Beidou priority multimode positioning method and system based on signal feature comparison, and the method comprises the following steps: S1, calculating the pseudo-range, Doppler and carrier phase measurement value residual error of each satellite according to the GNSS time service time and a verified reference position; s2, if the pseudo-range measurement value residual error of each satellite exceeds a first threshold value, counting the common-mode deviation of the pseudo-range measurement value residual error of each satellite, and removing the common-mode deviation; s3, respectively calculating signal characteristic values according to the pseudo-range, Doppler frequency shift and carrier phase measurement values of the Beidou satellite signal group and other satellite signal groups to obtain two groups of signal characteristic values; s4, dynamically selecting a Beidou priority or multi-mode combined positioning mode based on a signal characteristic value comparison rule; if the characteristic values of the two groups of signals are obviously different, the Beidou signals are preferentially adopted, otherwise, multimode positioning is adopted, and the safety, precision and reliability of positioning can be remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of satellite positioning technology, and in particular to a Beidou-priority multi-mode positioning method and system based on signal feature comparison. Background Art

[0002] Currently, there are multiple satellite positioning systems in the global satellite positioning field, such as the US GPS, Russia's GLONASS, the EU's GALILEO, and China's BeiDou satellite navigation system. Each positioning system has its own advantages and disadvantages. In practical applications, existing positioning devices and methods often lack intelligent mechanisms for prioritizing specific positioning systems. In some scenarios with high national information security requirements, the BeiDou satellite system should be prioritized for positioning. Furthermore, when BeiDou signals are consistent with those of other systems, the appropriate use of multi-mode positioning can further improve positioning reliability and accuracy. However, existing technologies cannot adequately meet the positioning requirements in these specific scenarios.

[0003] Currently, there are relatively few patents specifically addressing the prioritization of the Beidou satellite system for positioning in various scenarios, and there are still deficiencies in how to effectively determine the availability of Beidou signals and implement a fast and accurate Beidou priority positioning switching mechanism. For example, Chinese patent publication number CN109085619B relates to a positioning method and apparatus, storage medium, and receiver for a multi-mode GNSS system. The method measures pseudorange observations based on received satellite signals and calculates receiver clock differences for each positioning system in the multi-mode GNSS system. When the receiver clock differences of each positioning system are reliable, the receiver clock differences are used to calculate the inter-system delay between the positioning systems during measurement. When the inter-system delay is stable, the inter-system delay is used as an observation and combined with the pseudorange observations to detect and eliminate abnormal satellites. The pseudorange observations of the remaining satellites after eliminating the abnormal satellites are used to calculate the receiver's position information. However, the existing satellite positioning technology in Chinese patent publication number CN109085619B lacks an intelligent switching mechanism for multi-system collaboration, making it impossible to prioritize the Beidou system, resulting in insufficient positioning security and accuracy. Summary of the Invention

[0004] In order to solve the problem of the lack of Beidou priority selection mechanism in traditional multi-mode positioning, the present invention proposes a Beidou-priority multi-mode positioning method and system based on signal feature comparison, which can realize adaptive Beidou priority decision-making based on signal features. By constructing a multi-dimensional feature comparison model of pseudorange, Doppler and carrier phase, combined with the dynamic weight allocation of elevation angle-carrier-to-noise ratio, intelligent switching between Beidou and other satellite systems is realized, significantly improving the security, accuracy and reliability of positioning.

[0005] In order to achieve the above object, the present invention adopts the following technical solution: a BeiDou priority multi-mode satellite signal adaptive selection and determination method, comprising the following steps: S1, calculates the residuals of pseudorange, Doppler and carrier phase measurements of each satellite based on the GNSS timing time and verified reference position; S2: If the residuals of the pseudorange measurements of the satellites exceed a first threshold, calculating the common mode deviations of the residuals of the pseudorange measurements of the satellites and removing the common mode deviations; S3, calculating signal characteristic values ​​based on the pseudorange, Doppler frequency shift, and carrier phase measurement values ​​of the Beidou satellite signal group and the other satellite signal groups, respectively, to obtain two sets of signal characteristic values; S4, based on the signal characteristic value comparison rules, dynamically selects Beidou priority or multi-mode joint positioning mode; if there is a significant difference between the two sets of signal characteristic values, Beidou signal is determined to be used first, otherwise multi-mode positioning is determined to be used.

[0006] In this technical solution, the technical difficulty of the Beidou system being unable to be intelligently prioritized in multi-mode joint positioning is solved through multi-dimensional signal feature comparison and dynamic weight allocation model. Combined with pseudo-range common mode deviation correction, elevation angle-carrier-to-noise ratio joint noise modeling and eigenvalue total amount comparison rules, Beidou is prioritized when the signal quality difference is significant, and multi-system fusion positioning is enabled when there is no difference, so as to improve national security protection capabilities and positioning accuracy in complex scenarios.

[0007] Preferably, step S3 includes: S31, calculating the elevation angle of the current satellite based on the verified reference position; S32, modeling the noise of the current satellite measurement value based on the satellite elevation angle and carrier-to-noise ratio to obtain the reliability weight of the satellite measurement value at the current moment; S33, respectively calculating the reliability weight of each satellite according to the elevation angle and the carrier-to-noise ratio, and calculating the comprehensive reliability weight of each satellite; S34, obtaining the signal characteristic value of the corresponding measurement value of the Beidou satellite system and the signal characteristic value of the measurement value of other satellite systems according to the comprehensive reliability weight of each satellite.

[0008] Preferably, the step S33 includes: S331, calculating an elevation angle dynamic weight based on the satellite elevation angle and a preset elevation angle threshold range, wherein the elevation angle dynamic weight increases nonlinearly with increasing elevation angle and approaches zero when the elevation angle is lower than a first threshold to suppress low elevation angle noise; S332: Calculate a dynamic carrier-to-noise ratio weight based on the carrier-to-noise ratio and a preset carrier-to-noise ratio threshold range, wherein the dynamic carrier-to-noise ratio weight is generated based on a Sigmoid function constructed from the carrier-to-noise ratio and an empirical coefficient, and when the carrier-to-noise ratio is lower than a second threshold, the weight approaches zero to filter out low signal-to-noise ratio signals; S333: Calculate a comprehensive reliability weight based on the elevation angle dynamic weight, the carrier-to-noise ratio dynamic weight, and the reference noise variance of the measurement value.

[0009] Preferably, in step S333, the reference noise variance is modeled differentially according to the measurement value type: the pseudorange noise variance includes a carrier-to-noise ratio exponential decay term and an elevation angle inverse correction term; the Doppler noise variance is inversely proportional to the coherent integration time and the inverse of the square of the elevation angle; and the carrier phase noise variance is dynamically adjusted based on the phase double difference statistics and the continuous lock count.

[0010] Preferably, the step S34 includes: S341: Calculate the weighted sum of squares of the measurement value residuals of all Beidou satellites based on the comprehensive reliability weight of each satellite, perform normalization, and divide the result by the sum of the weight coefficients of all satellites to obtain the signal characteristic value of the corresponding measurement value of the Beidou satellite system; S342: Calculate the weighted sum of squares of the residual errors of the measurements of all satellites except BeiDou based on the comprehensive reliability weight of each satellite, and perform normalization to obtain the signal characteristic value of the measurement value corresponding to the current satellite system.

[0011] Preferably, in step S4, if at least one of the pseudorange characteristic values ​​of the two groups of signals is lower than the second threshold, the sum of the pseudorange, Doppler and carrier phase characteristic values ​​of each group of signals is calculated as the total characteristic value; if the pseudorange characteristic values ​​of the two groups of signals are both higher than the second threshold, the sum of the Doppler and carrier phase characteristic values ​​of each group of signals is calculated as the total characteristic value; the two groups of total characteristic values ​​are compared, and if the difference between the two groups of total characteristic values ​​exceeds the preset deviation threshold, it is determined that there is a significant difference between the characteristic values ​​of the two groups of signals.

[0012] The present invention also adopts the following technical solution: a method based on Beidou priority positioning, comprising the following steps: A1, receiving signals from Beidou satellites and other satellites, and obtaining Beidou satellite signal groups and other satellite signal groups; A2, performing feature analysis and comparison on the Beidou signal group and other satellite signal groups according to the above-mentioned Beidou priority multi-mode satellite signal adaptive selection and determination method to determine the positioning mode; A3, based on the determination result of the positioning method, transmits satellite signals and performs positioning calculations.

[0013] Preferably, step A3 includes: If it is determined that Beidou signals are preferred, the Beidou satellite signal group is transmitted for positioning calculation; If it is decided to use multi-mode positioning, the Beidou satellite signal group and other satellite signal groups are transmitted simultaneously for joint positioning calculation.

[0014] The present invention also adopts the following technical solution: a system based on Beidou priority positioning, characterized in that it adopts the above-mentioned method based on Beidou priority positioning, including: Signal receiving module, which receives and pre-processes Beidou signals and other satellite signals, and extracts effective positioning information from the signals; The signal analysis and judgment module is connected to the signal receiving module and dynamically selects the Beidou priority or multi-mode joint positioning mode based on the signal characteristic value comparison rules; The positioning selection module transmits the corresponding satellite signal to the positioning calculation module according to the judgment result of the signal analysis and judgment module; the positioning calculation module performs positioning calculation based on the satellite signal selected by the positioning selection module to obtain the positioning result; The result output module receives and outputs the positioning result of the positioning calculation module.

[0015] Preferably, the signal receiving module includes: Beidou signal receiving unit, which receives positioning signals transmitted by Beidou satellites, performs preliminary processing on the signals, and extracts effective positioning information from the signals; Other satellite signal receiving units receive signals from other satellite positioning systems except Beidou satellites, perform corresponding signal processing, and extract valid positioning information from the signals. The other satellite positioning systems include GPA, GLONSAA, and GSLILEO.

[0016] The beneficial effects of the present invention are: 1) Improve positioning security: When there is a discrepancy between the BeiDou signal and other system signals, the BeiDou satellite system is prioritized for positioning. This can reduce positioning errors in simulated spoofing attack tests, ensure information security, and effectively mitigate the risk of positioning deviation caused by abnormal signals from overseas satellite systems. 2) Enhanced positioning accuracy: When there is no deviation between Beidou and other system signals, multi-mode positioning is used to further improve positioning accuracy and stability, meeting the needs of some application scenarios with high positioning accuracy requirements; 3) Strong compatibility and flexibility: It can intelligently select the positioning method according to the signal characteristics, and can ensure the continuity and reliability of positioning under different signal conditions, with strong compatibility and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a flowchart of a method for adaptively selecting and determining Beidou priority multi-mode satellite signals.

[0018] Figure 2 The present invention is a flowchart of a method based on Beidou priority positioning.

[0019] Figure 3This is a structural diagram of a system based on Beidou priority positioning according to the present invention. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific implementation method described herein is only an optimal embodiment of the present invention, which is only used to explain the present invention and does not limit the scope of protection of the present invention. All other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] Example 1 This embodiment provides a BeiDou priority multi-mode satellite signal adaptive selection and determination method, referring to Figure 1 , including the following steps.

[0022] Step S1, using the relatively accurate time obtained by the receiver through the frame synchronization process and the reliable position saved historically, the pseudorange measurement residuals, Doppler measurement residuals and carrier phase measurement residuals of all satellites are calculated.

[0023] The pseudorange residual is determined by the difference between the actual observed pseudorange and the theoretical pseudorange.

[0024] Specifically, in this embodiment, the theoretical pseudorange needs to be calculated by combining the receiver's historical position with the geometric distance calculated by satellite ephemeris data, and correcting the receiver clock error, satellite clock error, ionospheric delay, and tropospheric delay.

[0025] First, the satellite position is determined based on the satellite ephemeris, and the geometric distance is calculated based on the known position of the receiver. Then, dual-frequency observation data or an ionospheric model is introduced to correct the ionospheric delay in signal propagation, and the tropospheric model is used to correct the atmospheric refraction effect. Finally, the receiver clock error and the satellite clock error are converted into distance error, and the theoretical pseudorange is obtained by combining all correction terms.

[0026] The actual observed pseudorange minus the theoretical pseudorange is the pseudorange residual, which is used to reflect the uncorrected error.

[0027] The Doppler residual is calculated as the difference between the actual measured frequency shift and the theoretically predicted frequency shift.

[0028] Specifically, in this embodiment, the theoretical prediction of frequency shift needs to take into account the relative motion between the receiver and the satellite, calculate the instantaneous velocity of the satellite based on the satellite orbit dynamics model, estimate the receiver velocity in combination with the receiver inertial navigation data or historical trajectory, calculate the dot product of the two velocity vectors and convert it into Doppler frequency shift.

[0029] At the same time, the inherent deviation of the satellite transmission frequency and the frequency offset of the receiver local oscillator need to be corrected.

[0030] The difference between the measured frequency shift and the theoretical frequency shift is the Doppler residual, which reflects the signal tracking error in a dynamic environment.

[0031] The carrier phase residual is determined by the difference between the phase observation value and the theoretical value, and the whole cycle ambiguity problem needs to be resolved.

[0032] Specifically, in this embodiment, the theoretical value calculation includes geometric distance, clock error correction, ionospheric delay reverse correction and tropospheric delay correction.

[0033] Since the carrier phase is affected by the ionosphere in the opposite direction to the pseudorange, the ionosphere correction needs to be adjusted in the opposite direction.

[0034] Integer cycle ambiguity is resolved by calculating the phase double difference statistics within consecutive locking cycles, combined with wide-lane combination or filtering algorithms to eliminate integer cycle unknowns.

[0035] Finally, the difference between the observed phase value and the theoretical value is the carrier phase residual.

[0036] The residual needs to be double-differenced to eliminate common errors and monitor phase continuity to avoid cycle slip interference.

[0037] In step S2, if the residual values ​​of the pseudorange measurement values ​​of all satellites are large, for example, they all exceed a certain threshold T, then the common mode deviation of the pseudorange measurement residuals of all satellites is statistically calculated as the estimated value of the receiver clock error, and the deviation is removed.

[0038] Step S3, calculating signal characteristic values ​​according to the pseudorange, Doppler shift and carrier phase measurement values ​​of the Beidou satellite signal group and other satellite signal groups, respectively, to obtain two groups of signal characteristic values.

[0039] The specific process of step S3 includes the following sub-steps.

[0040] Step S31: Calculate the elevation angle of the current satellite using the historically saved reliable positions.

[0041] Step S32: Model the noise of the current satellite's measurement value using the satellite's elevation angle and carrier-to-noise ratio, and provide a reliability weight for the satellite's measurement value at the current moment.

[0042] Step S33, calculating the reliability weight of each satellite according to the elevation angle and the carrier-to-noise ratio, and calculating the comprehensive reliability weight of each satellite.

[0043] In step S33, different weight calculation methods need to be used for different types of satellite measurement values.

[0044] First, the dynamic weights are calculated based on the satellite elevation angle.

[0045] Step S331, calculating the elevation angle dynamic weight according to the satellite elevation angle and the preset elevation angle threshold range, wherein the elevation angle dynamic weight increases nonlinearly with the increase of the elevation angle and approaches zero when the elevation angle is lower than the first threshold.

[0046] In this embodiment, the calculation of the elevation angle dynamic weight satisfies the following conditions: the preset elevation angle threshold interval is 15° to 60°, the weight function approaches 1 when the elevation angle reaches 60°, and approaches 0 when the elevation angle is lower than 15°; the elevation angle dynamic weight is dynamically modeled by adjusting the upper and lower limits of the threshold interval.

[0047] Specifically, the elevation angle The weight function can be combined with the sine function and the exponential decay function by and Multiplying them as the weight function of the elevation angle makes the weight approach 1 when the satellite elevation angle reaches 60 degrees, and the weight approach 0 when the elevation angle is lower than 15 degrees, thereby suppressing the noise impact of low-elevation-angle satellites.

[0048] In actual applications, the elevation angle threshold range (15 degrees to 60 degrees) can be dynamically adjusted according to scenario requirements. For example, in an open environment, the lower elevation angle limit can be relaxed to retain more available satellites.

[0049] Step S332: Calculate a dynamic carrier-to-noise ratio weight based on the carrier-to-noise ratio and a preset carrier-to-noise ratio threshold range, wherein the dynamic carrier-to-noise ratio weight is generated based on a Sigmoid function constructed from the carrier-to-noise ratio and an empirical coefficient, and the weight approaches zero when the carrier-to-noise ratio is lower than a second threshold.

[0050] In this embodiment, the calculation of the dynamic weight of the carrier-to-noise ratio satisfies the following conditions: The preset carrier-to-noise ratio threshold range is 25dB / Hz to 45dB / Hz, and the empirical coefficient k is determined by fitting historical data; When the carrier-to-noise ratio exceeds 45dB / Hz, the weight approaches 1, and when it is lower than 25dB / Hz, the weight approaches 0.

[0051] Specifically, the carrier-to-noise ratio weight is dynamically allocated through the Sigmoid function.

[0052] The function takes 35dB / Hz as the central reference value. When the carrier-to-noise ratio is higher than 45dB / Hz, the weight is close to 1, and when it is lower than 25dB / Hz, it approaches 0, thereby giving priority to satellite signals with high signal-to-noise ratio.

[0053] The empirical coefficient k is determined by fitting historical data, and the upper and lower thresholds of the carrier-to-noise ratio can be reconfigured in different signal-to-noise environments (such as strong electromagnetic interference scenarios).

[0054] S333: Calculate a comprehensive reliability weight based on the elevation angle dynamic weight, the carrier-to-noise ratio dynamic weight, and the reference noise variance of the measurement value.

[0055] The comprehensive reliability weight is determined by the elevation angle weight, the carrier-to-noise ratio weight and the baseline noise variance of the measurement value.

[0056] Specifically, the ratio of the product of the elevation angle weight and the carrier-to-noise ratio weight to the reference noise variance of the measurement value may be used as the total reliability weight.

[0057] The reference noise variance needs to be modeled differently for different measurement types.

[0058] The pseudorange noise variance includes the carrier-to-noise ratio exponential decay term and the elevation angle inverse sine correction term.

[0059] In this embodiment, the calculation of the pseudorange noise variance includes: The exponential decay term is generated based on the carrier-to-noise ratio and the attenuation coefficient to suppress low signal-to-noise ratio noise; The elevation reciprocal correction term is generated based on the reciprocal of the elevation sine value and is used to filter multipath interference.

[0060] Among them, the exponential attenuation term, carrier-to-noise ratio and elevation angle reciprocal correction term are respectively provided with empirical constant coefficients, which can be set according to actual usage.

[0061] The calculation of Doppler noise variance comprehensively considers the influence of carrier-to-noise ratio, satellite elevation angle and coherent integration time.

[0062] The higher the carrier-to-noise ratio, the better the signal quality and the lower the noise variance. On the contrary, when the carrier-to-noise ratio is lower than a certain threshold, the noise variance increases significantly.

[0063] The effect of satellite elevation angle on noise is that the lower the elevation angle, the more obvious the signal is affected by multipath effects or atmospheric disturbances, and the noise variance increases accordingly. For example, when the satellite elevation angle decreases from a high angle to a low angle, the noise variance may increase exponentially. In this embodiment, the elevation angle effect term can be expressed as

[0064] The Doppler noise variance is inversely proportional to the coherent integration time. The longer the coherent integration time, the higher the receiver's tracking accuracy of the Doppler frequency shift, and the noise variance decreases due to the enhanced signal smoothing effect.

[0065] In addition, the empirical constant coefficient c is introduced 2 In order to adapt to the dynamic characteristics of different hardware or environments, the coefficient is calibrated by measured data. For example, the coefficient value is adjusted in high dynamic scenes to optimize tracking stability. In this embodiment, the coherent integration time influence term can be expressed as

[0066] The product of the elevation angle influence term and the coherent integration time influence term is used as the Doppler noise variance. By dynamically adjusting the above parameters, the noise variance model can accurately reflect the signal quality differences, provide a reliable basis for the signal weight calculation of Beidou and other systems, and thus support intelligent decision-making of positioning modes.

[0067] The carrier phase noise variance is calculated based on the phase double difference statistics and the continuous lock count, combined with the carrier wavelength λ to quantify phase stability. Fewer phase jumps within a continuous lock cycle result in lower noise variance, making it suitable for high-precision positioning scenarios.

[0068] In this embodiment, the calculation of the carrier phase noise variance includes: calculating the phase double difference statistic through the phase change amount within the continuous locking period; the noise variance is proportional to the carrier wavelength and the square root of the phase double difference statistic, and inversely proportional to the square root of the carrier phase continuous locking count.

[0069] Step S34 , obtaining the signal characteristic values ​​of the Beidou satellite system's corresponding measurement values ​​and the signal characteristic values ​​of the measurement values ​​of other satellite systems based on the comprehensive reliability weights of the respective satellites.

[0070] After completing the weight distribution, the normalized weighted sum of squares of the residuals of the BeiDou satellite group and other satellite groups are calculated respectively.

[0071] For the Beidou satellite group, the residuals of all Beidou satellite measurements are weighted and summed up and then divided by the total weight coefficient to generate the normalized eigenvalue; other satellite groups are calculated separately using the same method.

[0072] The normalized weighted sum of squares of the measurement value residuals is used as the signal characteristic value of the corresponding measurement value of the current satellite system.

[0073] The eigenvalues ​​of pseudorange, Doppler and carrier phase need to be calculated and compared independently.

[0074] The eigenvalue comparison rules are as follows: If the pseudorange eigenvalue of any satellite group is below the preset threshold A, the pseudorange, Doppler, and carrier phase eigenvalues ​​of that group are summed to generate a total eigenvalue. If both pseudorange eigenvalues ​​are above threshold A, only the sum of the Doppler and carrier phase eigenvalues ​​is compared. A deviation threshold is used to determine the difference between BeiDou signals and other systems, enabling intelligent switching between BeiDou-first and multi-mode joint positioning modes.

[0075] Its advantage is that the elevation angle-carrier-to-noise ratio joint weight model can dynamically adapt to complex environments, such as urban multipath or ionospheric disturbances, while the type-specific noise variance modeling accurately reflects the error characteristics of different observation values.

[0076] Example 2 This embodiment provides a system based on Beidou priority positioning. Figure 3, including signal receiving module, signal analysis and judgment module, positioning selection module, positioning calculation module and result output module.

[0077] Among them, the signal receiving module consists of Beidou signal receiving unit and other satellite signal receiving units.

[0078] The Beidou signal receiving unit is used to receive the positioning signals transmitted by Beidou satellites, perform preliminary processing on the signals, and extract effective positioning information from the signals.

[0079] Other satellite signal receiving units can receive signals from satellite positioning systems other than Beidou satellites, perform corresponding signal processing, and extract effective positioning information from the signals.

[0080] The signal analysis and judgment module is connected to the Beidou signal receiving module and other satellite signal receiving modules to analyze the characteristic differences between Beidou signals and other system signals.

[0081] The judgment rule is: when there is a difference between the Beidou signal and the signals of other systems, the Beidou signal is used first; when there is no deviation between the Beidou signal and the signals of other systems, multi-mode positioning is used.

[0082] The specific judgment rules of this module refer to the Beidou priority multi-mode satellite signal adaptive selection judgment method in Example 1.

[0083] The positioning selection module selects the Beidou satellite signal for positioning calculation based on the judgment result of the signal analysis and judgment module. If it is determined that the Beidou signal is preferred, the Beidou satellite signal will be selected for positioning calculation; if it is determined that multi-mode positioning is adopted, the Beidou satellite signal and the signals of other satellite positioning systems will be transmitted to the positioning calculation module at the same time for joint positioning calculation.

[0084] The Positioning Calculation Module performs positioning calculations based on the satellite signals selected by the Positioning Selection Module, producing a positioning result. For single-Beidou signal positioning, a positioning algorithm suitable for the Beidou system is used; for multi-mode positioning, a multi-system fusion positioning algorithm is used.

[0085] The result output module outputs the positioning results obtained by the positioning calculation module in an appropriate manner, such as transmitting them to other devices through serial ports, SPI, I2C, etc.

[0086] In actual applications, the signal receiving module can use a dedicated Beidou-compatible multi-mode satellite signal receiver, which can simultaneously receive Beidou and GPS, GLONASS, GALILEO and other satellite signals.

[0087] The signal analysis and judgment module can be implemented through software programming, running the signal analysis and judgment program on a high-performance embedded processor to monitor the characteristic differences between Beidou signals and other system signals in real time.

[0088] The positioning selection module and the positioning calculation module can also be integrated into an embedded processor, and their functions can be realized by writing corresponding algorithm programs.

[0089] In the signal receiving step, after the system is started, the Beidou signal receiving module and other satellite signal receiving modules start working at the same time to continuously receive satellite signals.

[0090] In the signal analysis and judgment step, the signal analysis and judgment program performs a feature analysis and comparison on the Beidou signal and other system signals at regular intervals, such as 1 second.

[0091] The positioning calculation module uses least squares method, Kalman filtering and other algorithms for positioning calculation.

[0092] Taking the least squares method as an example, if the positioning calculation module only receives signals from the Beidou system, the only state that needs to be determined during the positioning calculation is the ECEF three-dimensional coordinates of the position, which is 4 states away from the Beidou system time difference of the receiver. At least 4 satellites are needed to construct the positioning solution equation and obtain the positioning result.

[0093] If the positioning calculation module receives signals from multiple satellite systems, such as BeiDou, GPS, GLONASS, and Galileo, the positioning calculation method used is essentially the same as the BeiDou-only method, but the number of states required to be determined changes: the ECEF three-dimensional coordinates of the location and the time differences between the BeiDou, GPS, GLONASS, and Galileo systems at the receiver, for a total of seven states. A minimum of seven satellites is required to construct the positioning solution equation and obtain a positioning result.

[0094] Finally, the positioning results are output through the result output module, such as transmitting the positioning results to terminal devices such as mobile phones through interfaces such as serial ports, SPI, and I2C.

[0095] Example 3 This embodiment provides a method based on Beidou priority positioning. Figure 2 , including the following steps.

[0096] Step A1, signal reception, receives Beidou satellite signals through the Beidou signal receiving module, and simultaneously receives signals from other satellite positioning systems through other satellite signal receiving modules.

[0097] Step A2, signal analysis and judgment: the signal analysis and judgment module performs feature analysis and comparison on the Beidou signal group and other satellite signal groups according to a Beidou priority multi-mode satellite signal adaptive selection and judgment method described in Example 1 to determine the positioning mode.

[0098] The specific steps of step A2 include the following sub-steps.

[0099] The receiver uses the relatively accurate time obtained through the frame synchronization process and the reliable position saved historically to calculate the pseudorange measurement residuals, Doppler measurement residuals and carrier phase measurement residuals of all satellites.

[0100] If the residual values ​​of the pseudorange measurements of all satellites are very large, for example, they all exceed a certain threshold T, then the common mode deviation of the pseudorange measurement residuals of all satellites is statistically calculated as the estimated value of the receiver clock error, and the deviation is removed.

[0101] Calculate the current satellite elevation angle using historically saved reliable positions.

[0102] The noise of the current satellite's measurement is modeled using the satellite's elevation angle and carrier-to-noise ratio, giving the reliability weight of the current satellite measurement. Different weight calculation methods are used for different types of satellite measurements.

[0103] After obtaining the reliability weights for all satellite measurements, the weighted sum of squares of the residual errors for all BeiDou satellites and the residual error for all satellites other than BeiDou are calculated and normalized. The result is then divided by the sum of the weight coefficients for all satellites. This normalized weighted sum of squares of the residual errors is used as the signal eigenvalue for the corresponding measurement value of the current satellite system. The signal eigenvalues ​​for pseudorange, Doppler, and carrier phase must be calculated separately.

[0104] The pseudorange, Doppler, and carrier phase signal eigenvalues ​​of the two satellite signals are compared. The comparison rule is: if one of the pseudorange eigenvalues ​​of the two signals is below a certain threshold A, the pseudorange eigenvalue of the same signal is summed with the eigenvalues ​​of the Doppler and carrier phase to obtain the total eigenvalue, and then the two total eigenvalues ​​are compared. If the pseudorange eigenvalues ​​of both signals are greater than the threshold A, only the Doppler and carrier phase eigenvalues ​​are summed to obtain the total eigenvalue, and then the two total eigenvalues ​​are compared.

[0105] If there is a significant difference between the two sets of values, the Beidou signal will be used first; if there is no deviation, multi-mode positioning will be used.

[0106] Step A3: Position selection and position calculation.

[0107] If it is determined that the Beidou signal is used first, the positioning selection module transmits the Beidou satellite signal to the positioning calculation module for positioning calculation.

[0108] If it is determined to adopt multi-mode positioning, the positioning selection module will simultaneously transmit the Beidou satellite signal and the signals of other satellite positioning systems to the positioning calculation module for joint positioning calculation.

[0109] The positioning calculation module performs positioning calculations based on the received satellite signals. Whether it is single-Beidou system positioning or multi-system fusion positioning, positioning calculations generally use the least squares algorithm and Kalman filter algorithm.

[0110] Taking the least squares method as an example, pseudo-range measurements are used to build a model to obtain the observation equation, the satellite pseudo-range measurements are associated with the theoretical model, and the observation matrix is ​​used to reflect the impact of satellite geometric distribution on positioning solution.

[0111] The state update amount is calculated by multiplying the transpose of the observation matrix and the pseudorange residual, and its value reflects the correction requirement of the receiver position and clock bias.

[0112] For single Beidou system positioning, the state quantities include the receiver's three-dimensional position coordinate correction and the Beidou system clock error correction, a total of four unknown parameters. Therefore, measurement values ​​from at least four visible Beidou satellites are required to complete the solution.

[0113] When multi-system joint positioning is involved, such as using the Beidou, GPS, GLONASS and Galileo systems at the same time, the state quantity needs to be expanded to include the independent clock correction parameters of each system. The total state quantity is expanded to seven dimensions, including three-dimensional position correction and four system clock corrections.

[0114] At this time, at least seven satellites from different systems are required to participate in the calculation, and each system must contribute at least one valid satellite data.

[0115] In actual operations, whether in single-system or multi-system scenarios, a unified least squares algorithm framework is used, and mode switching is achieved only by adjusting the state dimension and inputting satellite data.

[0116] For example, the single Beidou mode only processes the pseudorange residuals of Beidou satellites, while the multi-system mode integrates data from multiple constellations and expands the number of observation matrix columns to adapt to the newly added state quantities.

[0117] Through this design, the system can not only ensure the Beidou-first security needs, but also improve positioning accuracy and reliability through data fusion when there is no deviation in multi-system signals.

[0118] Finally, the positioning result obtained by the positioning calculation module is output through the result output module.

Claims

1. A BeiDou priority multi-mode satellite signal adaptive selection and determination method, characterized in that: The following steps are involved: S1, calculates the residuals of pseudorange, Doppler and carrier phase measurements of each satellite based on the GNSS timing time and verified reference position; S2: If the residuals of the pseudorange measurements of the satellites exceed a first threshold, calculating the common mode deviations of the residuals of the pseudorange measurements of the satellites and removing the common mode deviations; S3, calculating signal characteristic values ​​based on the pseudorange, Doppler frequency shift, and carrier phase measurement values ​​of the Beidou satellite signal group and the other satellite signal groups, respectively, to obtain two sets of signal characteristic values; S4: If there is a significant difference between the two sets of signal characteristic values, the Beidou signal is used first; otherwise, multi-mode positioning is used.

2. A BeiDou priority multi-mode satellite signal adaptive selection and determination method according to claim 1, characterized in that: The step S3 comprises: S31, calculating the elevation angle of the current satellite based on the verified reference position; S32, modeling the noise of the current satellite measurement value based on the satellite elevation angle and carrier-to-noise ratio to obtain the reliability weight of the satellite measurement value at the current moment; S33, calculating the reliability weight of each satellite according to the elevation angle and the carrier-to-noise ratio, and calculating the comprehensive reliability weight of each satellite; S34, obtaining, based on the comprehensive reliability weights of the respective satellites, signal characteristic values ​​of the corresponding measurement values ​​of the Beidou satellite system and signal characteristic values ​​of the measurement values ​​of other satellite systems.

3. A BeiDou priority multi-mode satellite signal adaptive selection and determination method according to claim 2, characterized in that: The step S33 includes: S331, calculating an elevation angle dynamic weight based on the satellite elevation angle and a preset elevation angle threshold range, wherein the elevation angle dynamic weight increases nonlinearly with increasing elevation angle and approaches zero when the elevation angle is lower than a first threshold; S332: Calculate a dynamic carrier-to-noise ratio weight based on the carrier-to-noise ratio and a preset carrier-to-noise ratio threshold range, wherein the dynamic carrier-to-noise ratio weight is generated based on a Sigmoid function constructed by the carrier-to-noise ratio and an empirical coefficient, and the weight approaches zero when the carrier-to-noise ratio is lower than a second threshold; S333: Calculate a comprehensive reliability weight based on the elevation angle dynamic weight, the carrier-to-noise ratio dynamic weight, and the reference noise variance of the measurement value.

4. A BeiDou priority multi-mode satellite signal adaptive selection and determination method according to claim 3, characterized in that: In step S333, the reference noise variance is modeled differentially according to the measurement value type: the pseudorange noise variance includes a carrier-to-noise ratio exponential decay term and an elevation angle reciprocal correction term; The Doppler noise variance is inversely proportional to the coherent integration time and the inverse of the square of the elevation angle; The carrier phase noise variance is dynamically adjusted based on the phase double difference statistics and the continuous lock count.

5. A BeiDou priority multi-mode satellite signal adaptive selection and determination method according to claim 2 or 3, characterized in that: The step S34 includes: S341: Calculate the weighted sum of squares of the measurement value residuals of all Beidou satellites based on the comprehensive reliability weight of each satellite, perform normalization, and divide the result by the sum of the weight coefficients of all satellites to obtain the signal characteristic value of the corresponding measurement value of the Beidou satellite system; S342: Calculate the weighted sum of squares of the residual errors of the measurements of all satellites except BeiDou based on the comprehensive reliability weight of each satellite, and perform normalization to obtain the signal characteristic value of the measurement value corresponding to the current satellite system.

6. A BeiDou priority multi-mode satellite signal adaptive selection and determination method according to claim 1, 2, 3 or 4, characterized in that: In step S4, if at least one of the pseudorange characteristic values ​​of the two groups of signals is lower than the second threshold, the sum of the pseudorange, Doppler and carrier phase characteristic values ​​of each group of signals is calculated as the total characteristic value; if the pseudorange characteristic values ​​of the two groups of signals are both higher than the second threshold, the sum of the Doppler and carrier phase characteristic values ​​of each group of signals is calculated as the total characteristic value; if the difference between the two groups of total characteristic values ​​exceeds the preset deviation threshold, it is determined that there is a significant difference in the characteristic values ​​of the two groups of signals.

7. A method based on Beidou priority positioning, characterized in that: The following steps are involved: A1, receiving signals from Beidou satellites and other satellites, and obtaining Beidou satellite signal groups and other satellite signal groups; A2, according to any one of claims 1-6, a Beidou priority multi-mode satellite signal adaptive selection and determination method, performing feature analysis and comparison on the Beidou signal group and other satellite signal groups to determine the positioning mode; A3, based on the determination result of the positioning method, transmits satellite signals and performs positioning calculations.

8. The Beidou-based priority positioning method according to claim 7, characterized in that: Step A3 includes: If it is determined that Beidou signals are preferred, the Beidou satellite signal group is transmitted for positioning calculation; If it is decided to use multi-mode positioning, the Beidou satellite signal group and other satellite signal groups are transmitted simultaneously for joint positioning calculation.

9. A system based on Beidou priority positioning, characterized in that: The method based on Beidou priority positioning according to claim 6 or 7 is adopted, comprising: Signal receiving module, which receives and pre-processes Beidou signals and other satellite signals, and extracts effective positioning information from the signals; The signal analysis and judgment module is connected to the signal receiving module and dynamically selects the Beidou priority or multi-mode joint positioning mode based on the signal characteristic value comparison rules; The positioning selection module transmits the corresponding satellite signal to the positioning calculation module according to the judgment result of the signal analysis and judgment module; The positioning calculation module performs positioning calculation based on the satellite signals selected by the positioning selection module to obtain the positioning result; The result output module receives and outputs the positioning result of the positioning calculation module.

10. The Beidou priority positioning system according to claim 9, characterized in that: The signal receiving module includes: Beidou signal receiving unit, which receives positioning signals transmitted by Beidou satellites, performs preliminary processing on the signals, and extracts effective positioning information from the signals; Other satellite signal receiving units receive signals from satellite positioning systems other than Beidou satellites, perform corresponding signal processing, and extract effective positioning information from the signals.

Images