A pseudo-satellite system positioning method based on Doppler phase difference

Abstract

The application discloses a pseudo-satellite system positioning method based on Doppler phase difference, and relates to the technical field of pseudo-satellite positioning, which comprises the following steps: setting a starting time and a terminal time, making a receiver continuously move from a starting point to a terminal point, and keeping the receiver capable of continuously tracking at least seven pseudo-satellites; continuously recording the whole-week carrier and phase change amount of each pseudo-satellite by the receiver to obtain a recording result; constructing an observation equation based on Doppler phase difference for each pseudo-satellite based on the recording result; obtaining the observation equations of all the pseudo-satellites and performing a simultaneous observation equation set; and solving the observation equation set to obtain the accurate coordinates of the starting point and the terminal point and outputting the same. The application constructs a new pseudo-satellite positioning observation equation set through the Doppler phase difference of the receiver between two points, realizes high-precision user position solving without the aid of code bandwidth on the premise that the frequencies of the pseudo-satellites are synchronized without clock synchronization.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of pseudolite positioning technology, in particular to a pseudolite system positioning method based on Doppler phase difference. BACKGROUND

[0002] With the increasing demand for indoor positioning, a large number of indoor positioning technologies have emerged and developed. Among them, as a navigation device capable of transmitting GNSS-like signals, pseudolite can be integrated with GNSS system to realize continuous indoor and outdoor positioning, and can also form a network to provide indoor location service for users, so it has a wide application prospect. Pseudolite usually uses a ground-based signal transmitter to provide GNSS-like positioning signals in areas where satellite navigation signals are weak or missing, to assist and enhance satellite navigation positioning function or to realize independent positioning. The use of pseudolite technology can effectively enhance the GNSS satellite navigation system, and pseudolite has the characteristics of strong anti-interference ability and flexible networking.

[0003] However, when using a pseudolite system to provide high-precision positioning services, the time synchronization accuracy between each pseudolite base station directly affects the measurement accuracy and has a crucial impact on positioning performance. In an independent networked pseudolite positioning system, the clock of each pseudolite base station can be set independently, but the problem of time synchronization between pseudolite base stations must be solved. Considering the cost factor, pseudolite base stations generally do not carry high-precision and long-term stable atomic clocks like GNSS satellites, but use relatively inexpensive voltage-controlled temperature-compensated crystal oscillators as clocks, which will cause serious clock drift and affect the performance of positioning services. Therefore, in order to provide high-precision positioning services, high-precision synchronization of the pseudolite system time is required. At the same time, the principle of pseudolite system positioning is similar to that of GNSS system, that is, the more satellite signals received by the receiver, the higher the positioning accuracy. When multiple satellite signals arrive at the same time, multiple access technology is needed to distinguish different satellites. Taking GPS as an example, it can be regarded as a spread spectrum communication system based on code division multiple access. The code in it is the pseudo code. Therefore, the pseudo code bandwidth of the pseudolite base station has a great influence on the positioning performance of the pseudolite system.

[0004] In summary, the high-precision performance of the current pseudolite system is greatly affected by the time synchronization performance between each pseudolite base station and the pseudo code bandwidth of each base station. Therefore, there is an urgent need for a pseudolite system positioning method that can achieve high-precision positioning without clock synchronization between each pseudolite base station and with less influence of pseudo random code on positioning accuracy. SUMMARY

[0005] To solve the above problems of the prior art, the present application provides a pseudolite system positioning method based on Doppler phase difference, which comprises the following steps:

[0006] set a start time and an end time, so that the receiver continuously moves from the start point to the end point, and keeps the receiver capable of continuously tracking a preset number of pseudolites, the preset number being at least 7;

[0007] The receiver continuously records the carrier whole week and phase change amount of each pseudolite to obtain a recording result.

[0008] Based on the recording result, an observation equation based on Doppler phase difference is constructed for each pseudolite.

[0009] Obtain the observation equations of all pseudolites and solve them to obtain an observation equation set about the pseudolite system.

[0010] Solve the observation equation set to obtain the accurate coordinates of the start point and the end point and output.

[0011] The present application is realized by the following technical scheme: the present scheme continuously moves the receiver between the start time and the end time, and keeps the receiver capable of continuously tracking more than at least 7 pseudolites during the whole movement process, and continuously records the carrier whole week and phase change amount of each pseudolite by the receiver to obtain a recording result; based on the recording result, an observation equation based on Doppler phase difference is constructed for each pseudolite, and the observation equations of all pseudolites are solved to construct an observation equation set about the pseudolite system, and the accurate coordinates of the receiver at the start point and the end point are obtained by solving the observation equation set. Since the phase accumulation of the pseudolite signal observed by the receiver only needs to keep the frequency synchronization between the pseudolites, the clock synchronization between the pseudolites is not required, and at the same time, the use of the pseudo-random code is not involved when the position is solved by the observation equation set, so the code bandwidth is not required, and the accurate solution of the user position can be realized.

[0012] As an optional technical scheme, based on the recording result, the observation equation based on Doppler phase difference of each pseudolite includes a first formula, which is specifically:

[0013]

[0014] ΔN represents the carrier phase whole week offset amount caused by the Doppler frequency shift, represents the carrier phase decimal part offset amount, f d (t) represents the Doppler frequency shift of the received signal caused by the movement of the receiver relative to the pseudolite, t0 is the time when the receiver starts from the start point, and t1 is the time when the receiver reaches the end point.

[0015] As an optional technical solution, based on the record result, the observation equation of each pseudolite based on Doppler phase difference is constructed, and the second formula is further included, specifically as follows:

[0016]

[0017] ΔL is the distance difference between the receiver and the pseudolite at the end point and the start point respectively, S1 is the distance between the receiver and the pseudolite at the start point, S2 is the distance between the receiver and the pseudolite at the end point, and v(t) is the radial instantaneous velocity of the receiver relative to the pseudolite;

[0018] Based on the Doppler effect formula, the third formula is obtained, specifically as follows:

[0019] v(t) / C=f d (t) / f

[0020] C represents the transmission rate of the pseudolite electromagnetic wave signal, and f represents the carrier frequency of the pseudolite signal.

[0021] Based on the second formula and the third formula, the fourth formula is obtained by processing, specifically as follows:

[0022]

[0023] λ=C / f represents the wavelength of the pseudolite electromagnetic wave signal.

[0024] As an optional technical solution, based on the first formula and the fourth formula, the fifth formula is obtained by processing, specifically as follows:

[0025]

[0026] When the receiver moves from the start point to the end point, the recorded carrier phase change amount includes not only the Doppler phase change amount of the received signal caused by the movement of the receiver relative to the pseudolite, but also the phase change amount of the pseudolite signal received by the receiver, which is represented by the sixth formula, specifically as follows:

[0027]

[0028] ΔN ′ represents the real recorded carrier phase change amount of the receiver, represents the real recorded carrier phase change amount of the receiver, ΔN0 represents the carrier phase change amount of the pseudolite signal received by the receiver, represents the carrier phase change amount of the pseudolite signal received by the receiver.

[0029] As an optional technical solution, based on the fifth formula and the sixth formula, a seventh formula is obtained by processing, specifically:

[0030]

[0031] Wherein, let And substitute into the seventh formula, and transform to obtain:

[0032]

[0033] As an optional technical solution, the eighth formula is used to calculate the distance between the receiver and the pseudolite at the starting point, and the ninth formula is used to calculate the distance between the receiver and the pseudolite at the terminal point, including:

[0034]

[0035] (p x ,p y ,p z ) represents the three-dimensional coordinates of the pseudolite, (u x1 ,u y1 ,u z1 ) represents the coordinates of the starting point, (u x2 ,u y2 ,u z2 ) represents the coordinates of the terminal point.

[0036] As an optional technical solution, the eighth formula, the ninth formula and the transformed seventh formula are solved simultaneously to obtain a tenth formula, including:

[0037]

[0038] Wherein, (p x ,p y ,p z ) is a known quantity, is a known quantity measured by the receiver, (u x1 ,u y1 ,u z1 ), (u x2 ,u y2 ,u z2 ), ΔS is an unknown quantity, and the tenth formula has a total of 7 unknown quantities. Therefore, at least 7 tenth formulas need to be solved simultaneously.

[0039] As an optional technical solution, at least 7 tenth formulas of the pseudolite are obtained and solved simultaneously to obtain an observation equation set of the pseudolite system.

[0040] The one or more technical solutions provided by the application have at least the following technical effects or advantages:

[0041] The application discloses a pseudo-satellite system positioning method based on Doppler phase difference. BRIEF DESCRIPTION OF DRAWINGS

[0042] The accompanying drawings, which are included to provide a further understanding of the application and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the principles of the application.

[0043] Figure 1 is a flowchart of a pseudo-satellite system positioning method based on Doppler phase difference in the application;

[0044] Figure 2 is a schematic diagram of movement of a receiver between a starting point and an ending point in the application;

[0045] Figure 3 is a simulation schematic diagram of a pseudo-satellite system in the application. DETAILED DESCRIPTION

[0046] In order to more clearly understand the above objectives, features and advantages of the present application, the application will be further described below in detail with reference to the drawings and specific embodiments. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0047] In the following description, a large number of specific details are set forth in order to facilitate a thorough understanding of the present application, however, the present application can also be implemented in other ways different from the scope described herein, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0048] EMBODIMENTS

[0049] Reference should be made to Figure 1 and Figure 2 , Figure 1 is a flowchart of a pseudo-satellite system positioning method based on Doppler phase difference in the application; Figure 2 is a schematic diagram of movement of a receiver between a starting point and an ending point in the application. The pseudo-satellite system positioning method based on Doppler phase difference comprises the following steps:

[0050] The starting point and the ending point are set, the receiver continuously moves from the starting point to the ending point, and the receiver can continuously track a preset number of pseudo-satellites, and the preset number is at least 7;

[0051] The receiver continuously records the whole number of each pseudolite carrier and the phase change amount, and obtains a recording result;

[0052] Based on the recording result, a Doppler phase difference-based observation equation is constructed for each pseudolite;

[0053] The observation equations of all pseudolites are obtained and combined, and an observation equation set about the pseudolite system is obtained;

[0054] The observation equation set is solved, and the accurate coordinates of the starting point and the accurate coordinates of the ending point are obtained and output.

[0055] The specific implementation of the present application is as follows:

[0056] The embodiment establishes the relationship between the distance difference and the carrier phase difference between the pseudolite and the receiver between the two points by the continuous movement of the receiver between the starting point and the ending point, constructs a new observation equation set, and solves the observation equation set to obtain the accurate coordinates of the receiver at the starting point and the ending point, thereby realizing high-precision positioning of the pseudolite system under the premise that the pseudolites are the same frequency and do not occupy the pseudorandom code bandwidth.

[0057] In Figure 2 , the pseudolites are frequency-synchronized, the receiver continuously moves between point 1 (the starting point) and point 2 (the ending point) along an arbitrary trajectory, and continuously tracks the pseudolite signals during the movement. The received pseudolite signal phase continuously accumulates with time. Since the initial whole number ambiguity of the received phase is unknown, the distance difference between the receiver and the pseudolite between the two points cannot be calculated by phase accumulation. Since the receiver continuously moves between the two points, the received pseudolite signal will have a Doppler frequency shift, and the Doppler frequency shift will affect the accumulation of the carrier phase, that is, the first formula:

[0058]

[0059] ΔN represents the whole number of the carrier phase offset caused by the Doppler frequency shift, represents the decimal part of the carrier phase offset, and f d (t) represents the Doppler frequency shift of the received signal caused by the movement of the receiver relative to the pseudolite, t0 is the time when the receiver starts from the starting point, and t1 is the time when the receiver reaches the ending point;

[0060] At the same time, the distance difference between the receiver moving from point 1 to point 2 and the pseudolite is, that is, the second formula:

[0061]

[0062] AL is the difference between the distances between the receiver and the pseudolite at the end point and the start point respectively, S1 is the distance between the receiver and the pseudolite at the start point, S2 is the distance between the receiver and the pseudolite at the end point, and v(t) is the instantaneous radial velocity of the receiver relative to the pseudolite;

[0063] Based on the Doppler effect formula, the following equation is obtained:

[0064] v(t) / C = f d (t) / f

[0065] C represents the transmission rate of the pseudolite electromagnetic wave signal, and f represents the carrier frequency of the pseudolite signal.

[0066] Based on the second formula and the third formula, the following equation is obtained:

[0067]

[0068] λ = C / f represents the wavelength of the pseudolite electromagnetic wave signal.

[0069] Then, based on the first formula and the fourth formula, the relationship between the distance difference of the receiver phase pseudolite and the carrier phase change caused by the Doppler effect is obtained, i.e., the following equation:

[0070]

[0071] When the receiver moves from the start point to the end point, the recorded carrier phase change amount includes not only the Doppler phase change amount caused by the movement of the receiver relative to the pseudolite, but also the phase change amount of the pseudolite signal received by the receiver, i.e., the following equation:

[0072]

[0073] ΔN ′ represents the real recorded carrier phase change amount, represents the real recorded carrier phase change amount, ΔN0 represents the carrier phase change amount of the pseudolite signal received by the receiver, represents the carrier phase change amount of the pseudolite signal received by the receiver;

[0074] Based on the fifth formula and the sixth formula, the following equation is obtained:

[0075]

[0076] Since the frequencies of the pseudolites are synchronized, the carrier phase accumulation amounts of the receiver for each pseudolite are equal. is a constant value but unknown, and can be obtained by the seventh formula, The value of will finally be fed back to the distance difference between the receiver and the pseudolite, so let and substitute it into the seventh formula, and transform it to get:

[0077]

[0078] According to the distance formula between two points, the distance between the receiver and the pseudolite at point 1 and point 2 is calculated respectively, that is, in the eighth formula and the ninth formula:

[0079]

[0080] (p x ,p y ,p z ) represents the three-dimensional coordinates of the pseudolite, (u x1 ,u y1 ,u z1 ) represents the coordinates of the starting point, and (u x2 ,u y2 ,u z2 ) represents the coordinates of the end point.

[0081] Finally, the eighth formula, the ninth formula and the transformed seventh formula are combined to get in the tenth formula:

[0082]

[0083] where (p x ,p y ,p z ) is a known quantity, is a known quantity measured by the receiver, (u x1 ,u y1 ,u z1 ), (u x2 ,u y2 ,u z2 ), and ΔS is an unknown quantity. There are a total of 7 unknown quantities in the tenth formula, so at least 7 tenth formulas need to be combined for calculation.

[0084] In the tenth formula, the three-dimensional coordinates of the pseudolite (p x ,p y ,p z ) are determined when the pseudolite system is laid out, and are known quantities. The whole cycle change ΔN′ and the carrier phase change are given by the receiver. The coordinates of point 1 (u x1 ,u y1 ,u z1 ) and the coordinates of point 2 (u x2 ,uy2 ,u z2 ) is an unknown quantity to be solved, and the distance difference caused by the carrier phase accumulation is also an unknown quantity, so there are 7 unknown quantities in the above equation, so at least 7 equations are needed to solve the coordinate positions of point 1 and point 2, which is why the receiver can continuously track more than 7 pseudolites, that is, receive 7 pseudolite signals, during the movement of the receiver from point 1 to point 2.

[0085] Please refer to Figure 3 , Figure 3 is a simulation schematic diagram of a pseudolite system in the application, and the pseudolite system is simulated by using MATLAB, and it should be noted that 1 represents the starting point 1, and 2 represents the ending point 2. The positions of the ten pseudolites and the positions of the starting point 1 and the ending point 2 are fixed, so that the receiver continuously moves between point 1 and point 2 along an arbitrary trajectory, different carrier phase measurement errors are set, and the observation equation set in the embodiment is solved to obtain the solving results of the starting point 1 and the ending point 2, as shown in Table 1.

[0086] Table 1

[0087] Phase measurement error (m) Point 1 solution error (m) Point 2 solution error (m) 0.002 (0.0258,0.0011,0.0254) (0.0235,0.0037,0.0203) 0.004 (0.0393,0.0001,0.0291) (0.0446,0.0077,0.0121) 0.006 (0.0587,0.0027,0.0778) (0.0910,0.0016,0.0505) 0.008 (-0.0719,0.0214,0.0188) (-0.0803,0.0368,0.0061) 0.010 (-0.1095,0.0570,-0.1170) (-0.1713,0.0397,-0.0653)

[0088] The observation equation set established in the embodiment can successfully solve the position coordinates between the starting point and the ending point of the movement, and since the phase measurement error is in the order of millimeters, the positioning accuracy of the pseudolite system positioning method based on the Doppler phase difference in the embodiment reaches the order of centimeters, and high-precision positioning is achieved.

[0089] Although the preferred embodiments of the present application have been described, those skilled in the art can make further changes and modifications to the embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including all changes and modifications falling within the scope of the present application.

[0090] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application also intends to include these modifications and variations.

Claims

1. A method for positioning in a pseudolite system based on differential Doppler phase, characterized in that, The method comprises the following steps: Setting a starting time and an ending time, so that the receiver continuously moves from the starting point to the ending point, and keeps the receiver capable of continuously tracking a preset number of pseudolites, the preset number being at least 7; The receiver continuously records the whole-week carrier phase and the phase change amount of each pseudolite, to obtain a record result; Based on the record result, an observation equation based on Doppler phase difference is constructed for each pseudolite; Obtaining the observation equations of all pseudolites and solving them together to obtain an observation equation set about the pseudolite system; Solving the observation equation set to obtain the accurate coordinates of the starting point and the ending point and outputting them; Based on the record result, constructing the observation equation based on Doppler phase difference for each pseudolite comprises a first formula, specifically: denotes the carrier phase integer ambiguity caused by the Doppler shift, denotes the carrier phase fractional ambiguity, denotes the Doppler shift of the received signal caused by the movement of the receiver relative to the pseudolite, is the time of departure of the signal from the pseudolite, is the time of arrival of the signal at the receiver. Based on the record result, constructing the observation equation based on Doppler phase difference for each pseudolite also comprises a second formula, specifically: a difference between a distance between the receiver and the pseudolite at the end point and a distance between the receiver and the pseudolite at the start point, a distance between the receiver and the pseudolite at the start point, a distance between the receiver and the pseudolite at the end point, a radial instantaneous velocity of the receiver relative to the pseudolite; Based on the Doppler effect formula, a third formula is obtained, specifically: a transmission rate of the pseudolite electromagnetic wave signals, a carrier frequency of the pseudolite signals; Based on the second formula and the third formula, a fourth formula is obtained, specifically: denotes the wavelength of the pseudolite electromagnetic wave signal; Based on the first formula and the fourth formula, a fifth formula is obtained, specifically: When the receiver moves from the starting point to the ending point, the recorded carrier phase change amount not only includes the Doppler phase change amount of the received signal caused by the movement of the receiver relative to the pseudolite, but also includes the phase change amount of the pseudolite signal received by the receiver, which is represented by a sixth formula, specifically: denotes the amount of integer cycle changes of the carrier phase recorded by the receiver truthfully, denotes the amount of fractional changes of the carrier phase recorded by the receiver truthfully, denotes the amount of integer cycle changes of the carrier phase of the received pseudolite signal by the receiver, denotes the amount of fractional changes of the carrier phase of the received pseudolite signal by the receiver; Based on the fifth formula and the sixth formula, a seventh formula is obtained, specifically: wherein let and substituting into the seventh formula, transformation is obtained: 。 2. The differential Doppler phase-based pseudolite system positioning method according to claim 1, wherein, The eighth formula is used to calculate the distance between the receiver and the pseudolite at the starting point, and the ninth formula is used to calculate the distance between the receiver and the pseudolite at the ending point, including: a three-dimensional coordinate representing a pseudo-satellite, a coordinate representing the starting point, a coordinate representing the end point.

3. The differential Doppler phase-based pseudolite system positioning method of claim 2, wherein, Solving the eighth formula, the ninth formula and the transformed seventh formula together to obtain a tenth formula, including: ； wherein, is a known quantity, is a known quantity measured by the receiver, , , is an unknown quantity, and there are a total of 7 unknown quantities in the tenth equation, so at least 7 tenth equations are needed to solve.

4. The differential Doppler phase-based pseudolite system positioning method of claim 3, wherein, Obtaining the tenth formula of at least 7 pseudolites and solving them together to obtain an observation equation set about the pseudolite system.

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