Pseudo-satellite system positioning method based on Doppler phase difference

Abstract

The invention discloses a pseudo-satellite system positioning method based on Doppler phase difference, which relates to the technical field of pseudo-satellite positioning, and comprises the following steps: setting a starting moment and an ending moment, enabling a receiver to continuously move from a starting point to an ending point, and keeping the receiver to continuously track at least seven pseudo-satellites; the receiver continuously records the whole cycle and the phase variation of each pseudo satellite carrier to obtain a recording result; based on the recorded result, constructing an observation equation based on Doppler phase difference for each pseudo-satellite; obtaining observation equations of all pseudo-satellites and carrying out simultaneous observation of equation sets; and resolving the observation equation set to obtain and output the precise coordinates of the starting point and the precise coordinates of the end point. According to the method, a new pseudo-satellite positioning observation equation set is constructed through Doppler phase difference of a receiver between two points, and high-precision user position calculation is realized without the aid of code bandwidth on the premise of frequency synchronization between pseudo-satellites without clock synchronization.

Description

Technical Field

[0001] The present invention relates to the technical field of pseudolite positioning, and in particular to a pseudolite system positioning method based on Doppler phase difference. Background Art

[0002] As people's demand for indoor positioning increases, a large number of indoor positioning technologies continue to emerge and develop. Among them, pseudo-satellites, as a navigation device that can transmit GNSS-like signals, can be integrated with the GNSS system to achieve continuous indoor and outdoor positioning, and can also self-organize networks to provide indoor location services for users, so they have broad application prospects. Pseudo-satellites usually use ground-based signal transmitters to provide GNSS-like positioning signals in areas where satellite navigation signals are weak or missing, to assist in enhancing satellite navigation and positioning functions, or to achieve independent positioning. The use of pseudo-satellite technology can effectively enhance the GNSS satellite navigation system. At the same time, pseudo-satellites have the characteristics of strong anti-interference ability and flexible networking.

[0003] However, when using the pseudo-satellite system to provide high-precision positioning services, the time synchronization accuracy between each pseudo-satellite base station directly affects the measurement accuracy and has a crucial impact on the positioning performance. In the independently networked pseudo-satellite positioning system, the clock of each pseudo-satellite base station can be set independently, but the time synchronization problem between pseudo-satellite base stations must be solved. Considering the cost factor, pseudo-satellite base stations generally do not carry high-precision, long-term stable atomic clocks like GNSS satellites, but use relatively cheap voltage-controlled temperature-compensated crystal oscillators as clocks, which will cause serious clock drift and affect the positioning service performance. Therefore, in order to provide high-precision positioning services, it is necessary to maintain high-precision synchronization of the pseudo-satellite system time. At the same time, the principle of positioning by the pseudo-satellite system is similar to that of the GNSS system, that is, for the receiver, the more satellite signals received, the higher the positioning accuracy provided. 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, in which the code is the pseudo-code, so the pseudo-code bandwidth of the pseudo-satellite base station also has a great influence on the positioning performance of the pseudo-satellite system.

[0004] In summary, the current high-precision performance of the pseudo-satellite system is greatly affected by the time synchronization performance between each pseudo-satellite base station and the pseudo-code bandwidth of each base station. There is an urgent need for a positioning method based on the pseudo-satellite system. While achieving high-precision positioning, there is no need for clock synchronization between each pseudo-satellite base station, and the positioning accuracy is less affected by the pseudo-random code. Summary of the invention

[0005] In order to solve the above-mentioned deficiencies in the prior art, the present invention provides a pseudo-satellite system positioning method based on Doppler phase difference, the method comprising the following steps:

[0006] Setting a start time and an end time so that the receiver moves continuously from the start point to the end point and the receiver is able to continuously track a preset number of pseudolites, wherein the preset number is at least 7;

[0007] The receiver continuously records the whole cycle and phase change of each pseudo-satellite carrier to obtain a recording result;

[0008] Based on the recorded results, constructing an observation equation based on Doppler phase difference for each pseudo-satellite;

[0009] Obtain the observation equations of all pseudolites and combine them to obtain the observation equation group about the pseudolites system;

[0010] The observation equation group is solved to obtain the precise coordinates of the starting point and the end point and output them.

[0011] The present invention is realized by the following technical scheme: the scheme is to continuously move the receiver between the start time and the end time, and keep the receiver able to continuously track more than at least 7 pseudo-satellites during the whole movement process, and continuously record the carrier cycle and phase change of each pseudo-satellite by the receiver to obtain the recording result; based on the recording result, an observation equation based on Doppler phase difference is constructed for each pseudo-satellite, and the observation equations of all pseudo-satellites are combined to construct an observation equation group about the pseudo-satellite system, and the precise coordinates of the receiver at the start point and the end point are obtained by solving the observation equation group. Since the phase accumulation of the pseudo-satellite signal observed by the receiver only needs to maintain frequency synchronization between pseudo-satellites, the clock synchronization between pseudo-satellites does not need to be guaranteed. At the same time, the use of pseudo-random codes is not involved when solving the position through the observation equation group, so the accurate solution of the user position can be achieved without the use of code bandwidth.

[0012] As an optional technical solution, based on the recording results, constructing the observation equation of each pseudo-satellite based on Doppler phase difference includes a first formula, specifically:

[0013]

[0014] ΔN represents the carrier phase integer offset caused by Doppler frequency shift. Indicates the fractional part of the carrier phase offset, f d (t) represents the Doppler frequency shift of the received signal caused by the movement of the receiver relative to the pseudo-satellite, t0 is the time when the receiver starts from the starting point, and t1 is the time when the receiver reaches the end point.

[0015] As an optional technical solution, based on the recording results, constructing the observation equation of each pseudo-satellite based on Doppler phase difference also includes a second formula, specifically:

[0016]

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

[0018] Based on the Doppler effect formula, the third formula is obtained, which is:

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

[0020] C represents the transmission rate of the pseudo-satellite electromagnetic wave signal, and f represents the carrier frequency of the pseudo-satellite signal;

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

[0022]

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

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

[0025]

[0026] When the receiver moves from the starting point to the end point, the recorded carrier phase change includes not only the Doppler phase change of the received signal caused by the movement of the receiver relative to the pseudo-satellite, but also the phase change of the pseudo-satellite signal received by the receiver, which is expressed by the sixth formula, specifically:

[0027]

[0028] ΔN ′ Indicates the actual carrier phase change recorded by the receiver. It represents the fractional change of the carrier phase actually recorded by the receiver, ΔN0 represents the integer change of the carrier phase when the receiver receives the pseudo-satellite signal. Indicates the fractional change in the carrier phase when the receiver receives the pseudo-satellite signal.

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

[0030]

[0031] Among them, Substitute it into the seventh formula and transform it to get:

[0032]

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

[0034]

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

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

[0037]

[0038] Among them, (p x ,p y ,p z ) is a known quantity, is the known quantity measured by the receiver, (u x1 ,u y1 ,u z1 ), (u x2 ,u y2 ,u z2 ), ΔS is an unknown quantity, and there are 7 unknown quantities in the tenth formula, so at least 7 tenth formulas need to be combined to solve.

[0039] As an optional technical solution, the tenth formula of at least seven pseudolites is obtained and combined to obtain a set of observation equations for the pseudolites system.

[0040] One or more technical solutions provided by the present invention have at least the following technical effects or advantages:

[0041] The present invention discloses a pseudo-satellite system positioning method based on Doppler phase difference. A new pseudo-satellite positioning observation equation group is constructed by using the Doppler phase difference of a receiver between two points. Under the premise of frequency synchronization between pseudo-satellites without clock synchronization, high-precision user position solution can be achieved without the aid of code bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of the present invention, and do not constitute a limitation on the embodiments of the present invention;

[0043] Figure 1 It is a flow chart of a pseudo-satellite system positioning method based on Doppler phase difference in the present invention;

[0044] Figure 2 is a schematic diagram of the receiver moving between the starting point and the end point in the present invention;

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

[0046] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0047] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those within the scope of this description. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0048] Example

[0049] Please refer to Figure 1 and Figure 2 , Figure 1 It is a flow chart of a pseudo-satellite system positioning method based on Doppler phase difference in the present invention; Figure 2 A pseudo-satellite system positioning method based on Doppler phase difference comprises the following steps:

[0050] Setting a starting point and an end point, so that the receiver moves continuously from the starting point to the end point, and the receiver is able to continuously track a preset number of pseudolites, wherein the preset number is at least 7;

[0051] The receiver continuously records the whole cycle and phase change of each pseudo-satellite carrier to obtain a recording result;

[0052] Based on the recorded results, constructing an observation equation based on Doppler phase difference for each pseudo-satellite;

[0053] Obtain the observation equations of all pseudolites and combine them to obtain the observation equation group about the pseudolites system;

[0054] The observation equation group is solved to obtain the precise coordinates of the starting point and the end point and output them.

[0055] The specific embodiments of the present invention are as follows:

[0056] In this embodiment, the receiver continuously moves between the starting point and the end point, establishes the relationship between the distance difference and the carrier phase difference between the pseudo-satellite and the receiver between the two points, constructs a new set of observation equations, and solves the observation equations to obtain the precise coordinates of the receiver at the starting point and the end point, thereby realizing high-precision positioning of the pseudo-satellite system under the premise that the pseudo-satellites have the same frequency and do not occupy the pseudo-random code bandwidth.

[0057] exist Figure 2 In the above formula, the pseudo-satellites are kept in frequency synchronization, and the receiver moves continuously between point 1 (starting point) and point 2 (end point) with an arbitrary trajectory, and keeps tracking the pseudo-satellite signal during the movement. The phase of the pseudo-satellite signal received by the receiver accumulates with the increase of time. Since the initial integer ambiguity of the received phase is unknown, the phase accumulation method cannot be used to calculate the distance difference between the receiver and the pseudo-satellite between the two points. Since the receiver moves continuously between the two points, the received pseudo-satellite signal will have a Doppler frequency shift, and the Doppler frequency shift will affect the accumulation of the carrier phase, that is, in the first formula:

[0058]

[0059] ΔN represents the carrier phase integer offset caused by Doppler frequency shift. Indicates the fractional part of the carrier phase offset, f d (t) represents the Doppler frequency shift of the received signal caused by the motion of the receiver relative to the pseudo-satellite, t0 is the time when the receiver starts from the starting point, and t1 is the time when the receiver reaches the end point;

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

[0061]

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

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

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

[0065] C represents the transmission rate of the pseudo-satellite electromagnetic wave signal, and f represents the carrier frequency of the pseudo-satellite signal;

[0066] Combining the second formula and the third formula, we can get the fourth formula:

[0067]

[0068] λ = C / f represents the wavelength of the pseudo-satellite electromagnetic wave signal;

[0069] Then, by combining the first formula and the fourth formula, we can obtain the relationship between the receiver phase pseudo-satellite distance difference and the carrier phase change caused by the Doppler effect, which is the relationship in the fifth formula:

[0070]

[0071] When the receiver moves from the starting point to the end point, the recorded carrier phase change includes not only the Doppler phase change of the received signal caused by the movement of the receiver relative to the pseudo-satellite, but also the phase change of the pseudo-satellite signal received by the receiver, that is, in the sixth formula:

[0072]

[0073] ΔN ′ Indicates the actual carrier phase change recorded by the receiver. It represents the fractional change of the carrier phase actually recorded by the receiver, ΔN0 represents the integer change of the carrier phase when the receiver receives the pseudo-satellite signal. Indicates the change in the fractional part of the carrier phase when the receiver receives the pseudo-satellite signal;

[0074] Combining the fifth formula and the sixth formula, we get the seventh formula:

[0075]

[0076] Since the pseudo-satellites maintain frequency synchronization, the receiver receives the accumulated phase of each pseudo-satellite carrier. is a constant but unknown, and from the seventh formula we know that, The value of will eventually be fed back to the distance difference between the receiver and the pseudo-satellite, so let 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 pseudo-satellite at point 1 and point 2 is calculated respectively, that is, the distance between the receiver and the pseudo-satellite at point 1 and point 2 ...2 and point 2, that is, the distance between the receiver and the pseudo-satellite at point 1 and point

[0079]

[0080] (p x ,p y ,p z ) represents the three-dimensional coordinates of the pseudo-satellite, (u x1 ,u y1 ,u z1 ) represents the coordinates of the starting point, (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 obtain the tenth formula:

[0082]

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

[0084] In the tenth formula, the three-dimensional coordinates of the pseudo-satellite (p x ,p y ,p z ) has been determined when the pseudo-satellite system is laid out and is a known quantity. The actual whole-cycle change ΔN′ recorded by the receiver is related to the carrier phase change 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 that needs to be solved. At the same time, the distance differential effect ΔS caused by the accumulation of carrier phase is also an unknown quantity. Therefore, there are 7 unknown quantities in the above equation, and at least 7 equations need to be solved to obtain the coordinate positions of point 1 and point 2. This is why the receiver is kept able to continuously track more than 7 pseudo-satellites when it moves from point 1 to point 2, that is, to receive 7 pseudo-satellite signals.

[0085] Please refer to Figure 3 , Figure 3 1 is a simulation diagram of a pseudo-satellite system in the present invention. The pseudo-satellite system is simulated using MATLAB. It should be noted that 1 represents the starting point 1, and 2 represents the end point 2. The positions of ten pseudo-satellites and the starting point 1, that is, the end point 2, are fixed, and the receiver is made to move continuously between point 1 and point 2 along an arbitrary trajectory. Different carrier phase measurement errors are set, and the observation equation group in this embodiment is solved to obtain the solution results of the starting point 1 and the end 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] Among them, the observation equation group established in this embodiment can successfully solve the position coordinates between the starting point and the end point of the movement, and because the phase measurement error is in the millimeter order, a pseudo-satellite system positioning method based on Doppler phase difference in this embodiment has a positioning accuracy of the centimeter order, thereby achieving high-precision positioning.

[0089] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

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

Claims

1. A pseudo-satellite system positioning method based on Doppler phase difference, characterized in that: The method comprises the following steps: Setting a start time and an end time so that the receiver moves continuously from the start point to the end point and the receiver is able to continuously track a preset number of pseudolites, wherein the preset number is at least 7; The receiver continuously records the whole cycle and phase change of each pseudo-satellite carrier to obtain a recording result; Based on the recorded results, constructing an observation equation based on Doppler phase difference for each pseudo-satellite; Obtain the observation equations of all pseudolites and combine them to obtain the observation equation group about the pseudolites system; The observation equation group is solved to obtain the precise coordinates of the starting point and the end point and output them.

2. The pseudo-satellite system positioning method based on Doppler phase difference according to claim 1, characterized in that: Based on the recorded results, the observation equation for each pseudo-satellite based on Doppler phase difference is constructed, including the first formula, which is specifically: ΔN represents the carrier phase integer offset caused by Doppler frequency shift. Indicates the fractional part of the carrier phase offset, f d (t) represents the Doppler frequency shift of the received signal caused by the movement of the receiver relative to the pseudo-satellite, t0 is the time when the receiver starts from the starting point, and t1 is the time when the receiver reaches the end point.

3. The method for positioning a pseudo-satellite system based on Doppler phase difference according to claim 2, characterized in that: Based on the recorded results, constructing the observation equation of each pseudo-satellite based on Doppler phase difference also includes a second formula, specifically: ΔL is the distance difference between the receiver and the pseudo-satellite at the end point and the start point respectively, S1 is the distance between the receiver and the pseudo-satellite at the start point, S2 is the distance between the receiver and the pseudo-satellite at the end point, and v(t) is the radial instantaneous velocity of the receiver relative to the pseudo-satellite; Based on the Doppler effect formula, the third formula is obtained, which is: v(t) / C=f d (t) / f C represents the transmission rate of the pseudo-satellite electromagnetic wave signal, and f represents the carrier frequency of the pseudo-satellite signal; Based on the second formula and the third formula, a fourth formula is obtained by processing, which is specifically: λ=C / f represents the wavelength of the pseudo-satellite electromagnetic wave signal.

4. The method for positioning a pseudo-satellite system based on Doppler phase difference according to claim 3, characterized in that: Based on the first formula and the fourth formula, a fifth formula is obtained by processing, which is specifically: When the receiver moves from the starting point to the end point, the recorded carrier phase change includes not only the Doppler phase change of the received signal caused by the movement of the receiver relative to the pseudo-satellite, but also the phase change of the pseudo-satellite signal received by the receiver, which is expressed by the sixth formula, specifically: ΔN ′ Indicates the actual change in carrier phase recorded by the receiver. It represents the fractional change of the carrier phase actually recorded by the receiver, and ΔN0 represents the integer change of the carrier phase when the receiver receives the pseudo-satellite signal. Indicates the fractional change in the carrier phase when the receiver receives the pseudo-satellite signal.

5. The method for positioning a pseudo-satellite system based on Doppler phase difference according to claim 4, characterized in that: Based on the fifth formula and the sixth formula, the seventh formula is obtained by processing, which is specifically: Among them, Substitute it into the seventh formula and transform it to get:

6. The method for positioning a pseudo-satellite system based on Doppler phase difference according to claim 5, characterized in that: The eighth formula is used to calculate the distance between the receiver and the pseudo-satellite at the starting point, and the ninth formula is used to calculate the distance between the receiver and the pseudo-satellite at the end point, including: (p x ,p y ,p z ) represents the three-dimensional coordinates of the pseudo-satellite, (u x1 ,u y1 ,u z1 ) represents the coordinates of the starting point, (u x2 ,u y2 ,u z2 ) represents the coordinates of the end point.

7. The method for positioning a pseudo-satellite system based on Doppler phase difference according to claim 6, characterized in that: The eighth formula, the ninth formula and the transformed seventh formula are combined to obtain the tenth formula, including: Among them, (p x ,p y ,p z ) is a known quantity, is the known quantity measured by the receiver, (u x1 ,u y1 ,u z1 ), (u x2 ,u y2 ,u z2 ), ΔS is an unknown quantity, and there are 7 unknown quantities in the tenth formula, so at least 7 tenth formulas need to be combined to solve.

8. The method for positioning a pseudo-satellite system based on Doppler phase difference according to claim 7, characterized in that: The tenth formula of at least seven pseudolites is obtained and combined to obtain a set of observation equations for the pseudolites system.

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