CN114966747A - Asynchronous pseudo satellite networking precision positioning method - Google Patents
Asynchronous pseudo satellite networking precision positioning method Download PDFInfo
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- CN114966747A CN114966747A CN202210564464.XA CN202210564464A CN114966747A CN 114966747 A CN114966747 A CN 114966747A CN 202210564464 A CN202210564464 A CN 202210564464A CN 114966747 A CN114966747 A CN 114966747A
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- 230000006855 networking Effects 0.000 title claims abstract description 27
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- 238000005259 measurement Methods 0.000 claims description 5
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/03—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers
- G01S19/10—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing dedicated supplementary positioning signals
- G01S19/11—Cooperating elements; Interaction or communication between different cooperating elements or between cooperating elements and receivers providing dedicated supplementary positioning signals wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
- G01S19/115—Airborne or satellite based pseudolites or repeaters
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention relates to the technical field of pseudolite positioning, in particular to a method for networking and precisely positioning an asynchronous pseudolite. The user establishes a large number of observation equations through different ranging signals received at different epochs, the observation equations are linearized by Taylor series expansion, and finally the position of the user is solved through the linearized equation set, so that the high-precision positioning of the user is completed. The invention can realize high-precision positioning of the user for the pseudo satellite under the conditions that the pseudo satellite does not have an atomic clock with high precision and high stability and the clocks of the pseudo satellites are not synchronous.
Description
Technical Field
The invention relates to the technical field of pseudolite positioning, in particular to a method for asynchronous pseudolite networking precision positioning.
Background
Pseudolites are generally defined as terrestrial GPS signal transmitters, and a synchronous pseudolite system was developed to verify the operation of the GPS transmitter and receiver as early as 1978 before the first GPS satellite transmitted. With the establishment of a GPS constellation, pseudolite technology is used for assisting in enhancing the positioning function of a GPS or realizing an independent networking positioning function in an environment with weak or missing GPS signals. In 2003, a positioning technology of a pseudolite of a first generation of a Locata system is formally published by a Locata company in australia, and a low-price crystal oscillator is utilized to enable the pseudolite positioning system to achieve high-precision synchronization, so that the application cost of the pseudolite is greatly reduced, and the application scene of the pseudolite is expanded.
Currently, pseudolite technology utilizes the principle of satellite navigation and positioning, and adopts a signal structure and a signal transmitter and receiver similar to a satellite. For a pseudo satellite for assisting in enhancing satellite navigation and positioning, an additional navigation signal which is the same as a standard navigation satellite signal is provided after the time service technology and a navigation satellite are precisely time-synchronized, so that the satellite navigation signal and the additional navigation signal are fused, and the positioning and navigation of a user are completed. For the autonomous networking positioning pseudolite system, it is first necessary to synchronize clocks of the pseudolites in the networking network for networking positioning. However, pseudolite base stations for pseudolite networked positioning systems are different from GNSS satellites and are typically equipped with inexpensive crystal clocks. The clock has low stability and precision, thereby generating clock drift errors, and various algorithms are needed to realize the clock synchronization with high precision, which often increases the complexity of the system.
Disclosure of Invention
The invention aims to provide a method for accurately positioning an asynchronous pseudolite networking, which can realize high-precision positioning of a user under the condition that clocks of all pseudolites in the networking are not synchronous.
In order to achieve the above object, the present invention provides a method for precise positioning of asynchronous pseudolite networking, comprising the following steps:
measuring to obtain the accurate position of each pseudo satellite base station in the group network;
a pseudo satellite base station transmitter transmits a modulation signal;
the user receiver receives the modulation signal, and processes and obtains the position information, the phase difference and the clock error information of the pseudo satellite base station transmitter;
establishing a carrier phase observation equation by using the acquired position information, the phase difference and the clock difference information;
linearizing the carrier phase observation equation by a taylor series;
and establishing an observation equation set and solving to obtain the position coordinate information of the user, thereby realizing accurate positioning.
The networking comprises a plurality of pseudo satellite base stations and a plurality of users, wherein the base stations emit GNSS/BD-like wireless positioning signals to provide positioning services for the users.
In the process of measuring and obtaining the accurate position of each pseudo satellite base station in the network group, geodetic surveying and mapping or the existing surveying and mapping tool is adopted for accurate measurement.
The pseudo satellite base station transmitter modulates position information and clock information onto a carrier wave through modulation to obtain the modulation signal, and the modulation signal is transmitted through up-conversion and a transmitting antenna.
And in the process of receiving the modulation signal by the user receiver and processing and obtaining the position information, the phase difference and the clock error information of the pseudo-satellite base station transmitter, the user receiver receives the modulation signal through a receiving antenna, and carries out down-conversion, A/D conversion, demodulation, de-spreading and text analysis on the modulation signal to obtain the position information, the phase difference and the clock error information obtained by comparing with a local clock of the pseudo-satellite base station transmitter.
The method comprises the steps of establishing an observation equation set and solving, specifically establishing the observation equation set through different observation values obtained by different epochs, and solving unknowns in the observation equation set.
The invention provides a method for networking and precisely positioning an asynchronous pseudolite, which is characterized in that the position of each pseudolite is precisely determined by adopting the existing mapping technology, a user in a regional network receives a ranging signal of each pseudolite to obtain position information, clock error information and carrier phase data of each pseudolite, and the user establishes an observation equation by using the ranging signal of each pseudolite, an unknown position of the user and a local clock error. The user establishes a large number of observation equations through different ranging signals received at different epochs, the observation equations are linearized by Taylor series expansion, and finally the position of the user is solved through the linearized equation set, so that the high-precision positioning of the user is completed. The invention can realize the high-precision positioning of the user under the condition that the pseudolite does not have an atomic clock with high precision and high stability and the pseudolite clocks are not synchronous.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for precise positioning of an asynchronous pseudolite networking according to the present invention.
Fig. 2 is a schematic structural diagram of a pseudolite networking positioning system according to an embodiment of the present invention.
Figure 3 is a schematic diagram of a pseudolite hardware implementation of a specific embodiment of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative and intended to explain the present invention and should not be construed as limiting the present invention.
Referring to fig. 1, the present invention provides a method for precise positioning of an asynchronous pseudolite networking, comprising the following steps:
s1: measuring to obtain the accurate position of each pseudo satellite base station in the group network;
s2: a pseudo satellite base station transmitter transmits a modulation signal;
s3: the user receiver receives the modulation signal, and processes and obtains the position information, the phase difference and the clock error information of the pseudo satellite base station transmitter;
s4: establishing a carrier phase observation equation by using the acquired position information, the acquired phase difference and the acquired clock difference information;
s5: linearizing the carrier phase observation equation by a taylor series;
s6: and establishing an observation equation set and solving to obtain the position coordinate information of the user, thereby realizing accurate positioning.
The networking comprises a plurality of pseudo satellite base stations and a plurality of users, wherein the base stations emit GNSS/BD-like wireless positioning signals to provide positioning services for the users.
In the process of measuring and obtaining the accurate position of each pseudolite base station in the network, geodetic surveying and mapping or the existing surveying and mapping tool is adopted for accurate measurement.
And the modulation signal is obtained by modulating position information and clock information onto a carrier wave through modulation by the pseudo-satellite base station transmitter, and is sent out through up-conversion and a transmitting antenna.
And in the process of receiving the modulation signal by the user receiver and processing and obtaining the position information, the phase difference and the clock error information of the pseudo-satellite base station transmitter, the user receiver receives the modulation signal through a receiving antenna, and performs down-conversion, A/D conversion, demodulation, de-spreading and text analysis on the modulation signal to obtain the position information, the phase difference and the clock error information obtained by comparing with a local clock of the pseudo-satellite base station transmitter.
And establishing an observation equation set and solving, specifically, establishing the observation equation set through different observation values obtained by different epochs, and solving the unknowns in the observation equation set.
The invention is further illustrated below with reference to specific examples and step flows:
referring to fig. 2, the pseudolite networking positioning system mainly comprises a regional network formed by a plurality of pseudolites and different types of users, and for the pseudolite system of independent networking, the pseudolite system comprises 4-5 pseudolite base stations and a plurality of users, and the base stations emit GNSS/BD-like wireless positioning signals to provide positioning services for the users. The system scheme comprises the following steps: 1) the signal system scheme adopts GNSS/BD signal system for reference and adopts direct-spread mode as wireless positioning signal. The C/A code adopts a GNSS/BD standby pseudo code, the code chip rate is 1.023Mcps or 2.046Mcps, the navigation message rate is 50bps, the message length and the content are set according to requirements, the GNSS/BD frequency point can be selected according to specific conditions in the radio frequency working frequency band, and any frequency point of 900-1900MHz can also be selected according to requirements, so that the influence of on-site radio interference is avoided as much as possible. 2) The hardware architecture of the pseudolite transmitter is shown in figure 3. Each transmitter in the group network modulates the clock information and the position information of the transmitter on a carrier wave through BPSK to form a modulation signal, the modulation signal is converted into an analog signal through D/A, and finally the modulation signal is sent to a user through up-conversion and a transmitting antenna.
In consideration of the requirement of millimeter-scale positioning, a carrier-phase ranging technique must be adopted. Theoretically, for a radio wave of 900MHz, with a wavelength of 30cm, the ranging accuracy can be up to 1% of the wavelength, i.e. 3 mm. Considering the influence of factors such as noise, interference and the like, as long as each link is reasonably designed and a smooth filtering technology is adopted, the precision level of 5 mm can be achieved. The key of the carrier phase ranging is the determination of cycle skipping and whole-cycle ambiguity, linear operation is carried out by utilizing observation equation sets of different epochs, the whole-cycle ambiguity and clock errors between a user and each pseudolite are solved, the position coordinates of the user are solved, and millimeter-level positioning is realized.
Further, in a satellite navigation positioning system, whether a satellite is in geosynchronous or medium earth orbit, it is located a considerable distance from the receiver. The power of the signals received by the terrestrial receiver is not very different, so the near-far effect is not obvious. However, in the case of a pseudolite navigation positioning system, since the distances of the pseudolite transmitters are different and the received signal powers of the pseudolite transmitters are greatly different, the near-far effect greatly affects the pseudolite transmitters, and therefore, the influence of the near-far effect on the receivers can be reduced by reasonably determining the near-region boundary and the far-region boundary through the optimized layout of the pseudolite transmitting base stations from the aspect of the layout of the pseudolites. Multipath effects are created by the reflection of the signal off the reflector surface, and the user receiver receives multipath signals in addition to line-of-sight signals. The multipath signals have different amplitudes and phases relative to the line-of-sight signal. Therefore, based on the influence of multipath signals, a small-sized anti-multipath antenna is designed to reduce the influence of multipath effect on a receiver.
The detailed implementation flow of the specific embodiment is as follows:
first, accurate measurements are made of each pseudolite base station by mapping or other measurement tools to determine its location information. The pseudo satellite transmitter modulates the clock information and the position information of the pseudo satellite transmitter on a carrier wave through BPSK to form a modulation signal, the modulation signal is converted into an analog signal through D/A, and finally the modulation signal is sent to different users through up-conversion and a transmitting antenna.
Different users receive the modulation signals sent by the pseudolite base station through different receivers (such as mobile phones, computers and the like), the receivers convert the modulation signals into intermediate-frequency signals through down-conversion, analog signals are converted into digital signals through A/D conversion, the digital signals are demodulated, de-spread and analyzed through messages, the ranging information and clock information of each base station are obtained, and the position coordinates of the users are solved by utilizing a carrier phase equation, so that high-precision positioning is achieved.
The calculation method of the carrier phase equation comprises the following steps:
λ×(N+θ)＝R j +c×Δt j +w+v
j 1,2.. m is the reference number of each pseudolite base station;
λ is the pseudolite signal carrier wavelength;
n is the initial integer ambiguity;
theta is the phase difference between the user and the pseudolite;
c is the speed of light (c is 3.0 × 10) 8 )；
Δt j Clock error between the user and different pseudo satellite base stations;
R j for the geometric distance between the user and the different pseudolites ((x) j ,y j ,z j ) Known coordinates for pseudolites, (x, y, z) user-sought coordinates);
w is the multipath error;
v is the user receiver noise error.
W (multipath error) can reduce the influence of the pseudo satellite base station on positioning accuracy through the geometric layout and antenna design of the pseudo satellite base station, and v (user receiver noise error) can reduce the influence of the pseudo satellite base station through denoising processing of a user receiver, so that an observation equation for calculating the carrier phase can be ignored. The carrier phase observation equation can be simplified as: λ × (N + θ) ═ R j +c×Δt j
The value of θ, which is used as the phase difference between the user and the pseudolite, can be obtained by a phase comparison method or other methods for measuring the phase, and can be regarded as a known value in the carrier phase observation equation, so the unknown parameters of the carrier phase observation equation are: n (initial integer ambiguity), Δ t j (clock difference between the user and different pseudolite base stations), (x, y, z) (user to be coordinated).
Considering R j The carrier phase observation equation is a nonlinear equation, so that the equation needs to be linearized. The carrier phase observation equation can be linearized using a taylor series expansion.
And (3) analyzing an observation equation of the carrier phase after linearization to obtain: in an epoch observation equation, a user observes a pseudolite base station with 3 user coordinate unknown parameters, 1 initial integer ambiguity and 1 user receiver to pseudolite clock offset. If j pseudolite signals are received by a user at the same time, 4+ j unknown parameters exist, and if j pseudolites are observed by adopting one epoch, j observation equations can be listed but the unknown parameters exist in 4+ j. Obviously, even if the number of the observation pseudosatellites is more than 4, the positioning cannot be performed by using 1 epoch, that is, the carrier phase positioning method cannot perform the positioning in real time.
When a static location is made on a user, multiple calendars may be observedYuan t i N, (i ═ 1,2.. n). At this time, the user coordinate correction number changes with time, and 3 unknown parameters are kept. Clock difference Δ t j Changes occur with epoch (j 1,2.... m, the corresponding pseudolite designation). If n epochs are observed and each epoch observes m pseudolites, then m multiplied by n observation equations are shared, in one epoch, the unknown parameters comprise m unknown integer ambiguities, at the moment, the coordinate correction number of the user receiver changes along with the time, and 3 unknown position parameters are kept. The clock difference Δ t varies from epoch to epoch, and is generally described by a second-order or third-order polynomial, i.e., Δ t ═ a 0 +a 1 (t-t 0 )+a 2 (t-t 0 ) 2 Wherein t is 0 For time reference, the clock offset parameter a of 3 users and pseudolite is maintained 0 、a 1 、a 2 There are (m +6) unknown numbers, and in order to solve the (m +6) unknown parameters, the number of observation equations must satisfy m × n ≧ m +6, that is:
for example, as shown in fig. 1, when the pseudolite number is 4, that is, when m is 4, the relationship between the epoch and the number of observation pseudolites
Knowing that the number of observation epochs is greater than or equal to
Therefore, an observation epoch of 3 can be taken, resulting in the following system of equations:
wherein N is 1 Representing the initial integer ambiguity of the first epoch user with the pseudolite base station numbered 1, and so on; theta.theta. 1 The phase difference between the first epoch user and the pseudolite base station numbered 1, and the rest are analogized in the following order; r is 1 For the first epoch user from the pseudolite base station numbered 1, i.e. distance
The rest is analogized in times; Δ t 1 The clock error between the first epoch user and the pseudolite base station with the label 1, and the rest are analogized in the following times; 10 unknowns are solved through 12 equations, and when the 12 unknowns are solved, the position (x, y, z) of a user is also solved, so that the position of the user is determined, the precise positioning of the user is completed, and the precise positioning of the asynchronous pseudolite networking is realized.
While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (6)
1. A method for precisely positioning asynchronous pseudolite networking is characterized by comprising the following steps:
measuring to obtain the accurate position of each pseudo satellite base station in the group network;
a pseudo satellite base station transmitter transmits a modulation signal;
the user receiver receives the modulation signal, and processes and obtains the position information, the phase difference and the clock error information of the pseudo satellite base station transmitter;
establishing a carrier phase observation equation by using the acquired position information, the acquired phase difference and the acquired clock difference information;
linearizing the carrier phase observation equation by a taylor series;
and establishing an observation equation set and solving to obtain the position coordinate information of the user, thereby realizing accurate positioning.
2. The method for precision positioning of asynchronous pseudolite networking according to claim 1,
the networking comprises a plurality of pseudo satellite base stations and a plurality of users, wherein the base stations emit GNSS/BD-like wireless positioning signals to provide positioning services for the users.
3. The method for precision positioning of asynchronous pseudolite networking according to claim 1,
in the process of measuring and obtaining the accurate position of each pseudolite base station in the network, geodetic surveying and mapping or the existing surveying and mapping tool is adopted for accurate measurement.
4. The method for precision positioning of asynchronous pseudolite networking according to claim 1,
and the modulation signal is obtained by modulating position information and clock information onto a carrier wave through the pseudo-satellite base station transmitter by modulation, and is sent out through up-conversion and a transmitting antenna.
5. The method for precision positioning of asynchronous pseudolite networking according to claim 1,
and in the process of receiving the modulation signal by the user receiver and processing and obtaining the position information, the phase difference and the clock error information of the pseudo-satellite base station transmitter, the user receiver receives the modulation signal through a receiving antenna, and performs down-conversion, A/D conversion, demodulation, de-spreading and text analysis on the modulation signal to obtain the position information, the phase difference and the clock error information obtained by comparing with a local clock of the pseudo-satellite base station transmitter.
6. The method for precision positioning of asynchronous pseudolite networking according to claim 1,
and establishing an observation equation set and solving, specifically, establishing the observation equation set through different observation values obtained by different epochs, and solving the unknowns in the observation equation set.
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