Long-range non-cooperative wireless positioning and inertial navigation combined positioning system and method

Abstract

This invention discloses a combined positioning system and method for long-range non-cooperative wireless positioning (NWL) and inertial navigation (INS) systems. First, the NWL system estimates parameters of the NWL signals and combines this with Time of Arrival (TOA) and Least Squares (LS) methods to achieve wireless positioning for the receiver. Then, by combining the NWL system with an inertial navigation system (INS), a tightly coupled NWL / INS positioning system is proposed. This system leverages the short-term high accuracy of INS and the superior positioning and fault-tolerant performance of the combined navigation system to further enhance the system's positioning performance. The proposed NWL / INS combined system provides a long-range, high-precision positioning system using NWL signals, laying the foundation for long-range wireless navigation in GNSS rejection situations.

Description

Technical Field

[0001] This invention belongs to the field of wireless positioning system technology, specifically relating to a combined positioning system of long-range non-cooperative wireless positioning and inertial navigation, and also to a combined positioning method of long-range non-cooperative wireless positioning and inertial navigation. Background Technology

[0002] Radio positioning systems play a vital role in various aspects of social life, traffic navigation, and military deployment, and are an indispensable part of modern human life. Currently, the most popular and widely used wireless positioning technologies are Bluetooth and Wi-Fi. Both can achieve positioning through Received Signal Strength Indication (RSSI) ranging technology, but they are short-range wireless positioning technologies, mainly used in short-range indoor scenarios. In outdoor scenarios, commonly used positioning systems are Global Navigation Satellite Systems (GNSS) and long-wave positioning systems. GNSS systems include the US GPS, Russia's GLONSS, China's BeiDou, and the EU's GALILEO. GNSS systems can provide accurate global position coordinates under line-of-sight (LOS) conditions. However, in environments such as forests, factories, and urban areas, satellite positioning system signals are blocked by buildings and trees, resulting in reflection, diffraction, and scattering, causing severe attenuation of received power. Alternatively, when the number of visible satellites is less than four, GNSS cannot provide satisfactory positioning accuracy, or may even fail to achieve positioning.

[0003] A typical long-range wireless positioning system is the long-wave positioning system, which mainly includes LORAN-C, RSDN-20, and NDB systems. However, these systems rely on the cooperation of the transmitting station and receiver, making them vulnerable to attack and failure in electronic warfare. Considering that existing wireless communication stations used for long-range communication (such as long / shortwave communication transmitters) have high transmission power, large size, and fixed locations, their positions can be determined by certain means, and these transmitters could be enemy transmitters. Therefore, non-cooperative wireless positioning (NWL) based on the non-cooperative wireless signals transmitted by these non-cooperative transmitters has the characteristics of long range and anti-interference. Since NWL achieves positioning based on the estimation of non-cooperative signals, its positioning accuracy and stability will decrease due to factors such as channel fading and receiver movement. Inertial navigation systems (INS) are another important navigation method. They can independently provide attitude, velocity, and position, as well as navigation information such as acceleration and angular rate. They can be used for the correct control of a vehicle and have advantages such as strong autonomy, good dynamic performance, comprehensive navigation information, and high output frequency. However, their errors accumulate over time, resulting in low long-term accuracy. Summary of the Invention

[0004] The purpose of this invention is to provide a combined positioning system of long-range non-cooperative wireless positioning and inertial navigation system, which solves the problem of low long-range wireless navigation and positioning accuracy in the case of GNSS system denial.

[0005] The present invention also aims to provide a combined positioning method using long-range non-cooperative wireless positioning and inertial navigation systems.

[0006] The first technical solution adopted in this invention is: a combined positioning system of non-cooperative wireless positioning and inertial navigation system, including a tightly coupled NWL / INS combined positioning system composed of a non-cooperative wireless positioning system (NWL) and an inertial navigation system (INS), and a UKF filter; wherein the NWL includes a transmitting station that transmits long-range radio signals that are independent of ionospheric reflection and a carrier receiver, and the positioning terminal calculates the distance from each transmitting station to the positioning terminal by measuring the arrival time of the signals transmitted by each transmitting station; the positioning terminal is also equipped with an inertial measurement unit (IMU), and the INS system collects the data obtained by the inertial measurement unit; the UKF filter is used for fusion filtering of INS and NWL information.

[0007] The invention is further characterized in that, The inertial measurement unit includes a three-axis accelerometer and a gyroscope; the accelerometer is used to measure the acceleration of the carrier receiver in different states, thereby obtaining the specific force information of the positioning terminal; the gyroscope detects the angular velocity of the carrier about three fixed axes through Coriolis force, and obtains the attitude information of the carrier receiver accordingly.

[0008] There are three or more launch stations.

[0009] The second technical solution adopted in this invention is a combined positioning method of long-range non-cooperative wireless positioning and inertial navigation, and the specific operation steps are as follows: Step 1: Establish an NWL / INS tightly coupled integrated positioning error model based on the NWL / INS tightly coupled integrated positioning system, and construct the measurement equation and state equation of the NWL / INS tightly coupled integrated positioning error model; use the pseudorange error and pseudorange rate error of the system as inputs to the measurement equation; Step 2: Use the Unscented Kalman Filter (UKF) algorithm to fuse and filter the NWL and INS information to obtain the optimal estimate of the positioning terminal's position error. Subtract the estimate from the position information output by the INS to calculate the final NWL / INS positioning information.

[0010] The invention is further characterized in that, Step 1 is as follows: 1) The NWL / INS tightly coupled positioning system uses the northeast-sky geographic coordinate system as the navigation coordinate system, denoted as the n-system; and the right-front-upper coordinate system as the positioning terminal coordinate system, denoted as the b-system; and sets the INS error state variables to 15 dimensions and the NWL error state variables to 8 dimensions. 2) The INS error state variables are: (1) in, This represents the misalignment angle error in the three directions of East, North, and Sky in the n-system; This represents the three velocity errors in the n-system; This indicates latitude error, longitude error, and altitude error; This indicates that the gyroscope in the b-series has a constant zero bias. This indicates that the accelerometer constant has zero bias in the b-series. The state transition matrix of INS is The system noise driving matrix is The driving noise is ; 3) NWL state variables are: (2) In the above formula, The pseudorange error of NWL is generated by the propagation delay error of the signal received by the receiver from the transmitting station. The pseudorange rate error of NWL is generated by the carrier frequency estimation error of the signal received by the receiver from the transmitting station. In non-cooperative scenarios, the state variables of each transmitting station are solved separately. The state equation of NWL can be expressed as: (3) , indicating the first One launch site, The process noise vector for the NWL pseudorange error. The process noise vector for the NWL pseudorange rate error; From equation (3), the NWL state transition matrix is: (4) in, for The zero matrix, for The identity matrix; The noise matrix of the NWL driving process is: (5) in, yes The identity matrix; The process noise vector of NWL is: (6) 4) Combine the INS state equation and the NWL state equation to obtain the state equation of the tightly coupled INS / NWL positioning error model: (7) 5) Construct the measurement equations for the tightly coupled NWL / INS positioning error model: The measurement equations for the NWL / INS tightly coupled positioning error model are as follows: (8) in, For measurement input, For the observation matrix, For measuring noise.

[0011] pseudorange error Combining the pseudorange rate error with the measurement equations of the NWL / INS tightly coupled positioning error model, the measurement equations of the NWL / INS tightly coupled system are obtained from (8): (9).

[0012] The specific calculations for the pseudorange error and pseudorange rate error of the system in step 1 are as follows: Long-range non-cooperative positioning (NWL) uses the time-of-arrival (TOA) method to estimate the propagation time of non-cooperative signals transmitted from a known and fixed transmitting station, thereby obtaining the estimated distance and velocity from the carrier receiver to the transmitting station. Inertial navigation systems (INS) use an inertial navigation algorithm to calculate the attitude, velocity, and position of the current positioning terminal, and perform position calculation to obtain the estimated distance and velocity from the positioning terminal to the transmitting station. The estimated distance is called pseudorange, and the estimated velocity is called pseudorange rate. The pseudorange error and pseudorange rate error are obtained by subtracting the pseudorange and pseudorange rate of the NWL and INS systems, respectively.

[0013] Step 2 is as follows: The Unscented Kalman Filter (UKF) algorithm is used to fuse and filter the information from the NWL and INS to obtain the optimal estimate of the position error. The difference between this estimate and the position information output by the INS is used to calculate the final NWL / INS positioning information. At the same time, the results obtained after the filter update are used to correct the results calculated by the INS and the original output of the IMU, and the pseudorange and pseudorange rate outputs of the NWL are also corrected to improve the positioning accuracy of the NWL.

[0014] The beneficial effects of this invention are that the combined positioning system and method of long-range non-cooperative wireless positioning and inertial navigation system of this invention... 1. The NWL positioning system uses non-cooperative radio signals for positioning, which has strong anti-interference capabilities and has become an important supplement to GNSS. 2. The NWL positioning system utilizes long-wave and other long-distance communication signals to achieve long-distance wireless positioning; 3. The NWL / INS tightly coupled positioning system uses non-cooperative radio signals for positioning, which has strong anti-interference capabilities and has become an important supplement to GNSS. 4. The NWL / INS tightly coupled positioning system further improves the accuracy of long-range wireless positioning by utilizing INS; 5. The NWL / INS tightly coupled positioning system utilizes NWL to further improve the positioning accuracy of INS; 6. The NWL / INS tightly coupled positioning system utilizes long-distance communication signals to achieve long-distance wireless positioning. Attached Figure Description

[0015] Figure 1 This is a flowchart of the method of the present invention.

[0016] Figure 2 This is a structural diagram of the NWL system of the present invention.

[0017] Figure 3This is a block diagram of the NWL / INS tightly coupled combined positioning system of the present invention.

[0018] Figure 4 This is a schematic diagram of NWL positioning according to the present invention.

[0019] Figure 5 This is a comparison chart of the positioning accuracy of NWL, INS, and NWL / INS according to the present invention.

[0020] Figure 6 This is a comparison chart of the positioning stability of NWL, INS, and NWL / INS according to the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0022] Example 1 The long-range non-cooperative wireless positioning and inertial navigation system combined positioning system of the present invention includes an NWL / INS tightly coupled combined positioning system consisting of a non-cooperative wireless positioning system (NWL) and an inertial navigation system (INS), and a UKF filter; wherein, as shown in the figure... Figure 1 As shown, the NWL includes a transmitting station that transmits long-range radio signals that are independent of ionospheric reflection and a carrier receiver. The positioning terminal calculates the distance from each transmitting station to the positioning terminal by measuring the arrival time of the signals transmitted by each transmitting station. The positioning terminal is also equipped with an inertial measurement unit (IMU), and the INS system collects the data obtained by the IMU. The UKF filter is used for the fusion filtering of INS and NWL information.

[0023] The inertial measurement unit includes a three-axis accelerometer and a gyroscope; the accelerometer is used to measure the acceleration of the carrier receiver in different states, thereby obtaining the specific force information of the positioning terminal; the gyroscope detects the angular velocity of the carrier about three fixed axes through Coriolis force, and obtains the attitude information of the carrier receiver accordingly.

[0024] There are three or more launch stations.

[0025] Example 2 like Figure 2 As shown, the combined positioning method of long-range non-cooperative wireless positioning and inertial navigation system provided in this embodiment includes the following steps: Step 1: As Figure 3 As shown, an error model for tightly coupled NWL / INS integrated navigation is established, along with the corresponding state equations and measurement equations: 1) The tightly coupled integrated navigation error model uses the northeast-sky geographic coordinate system as the navigation coordinate system (n system) and the right-front-upper coordinate system as the positioning terminal coordinate system (b system). The INS error state variables are set to 15 dimensions and the NWL error state variables are set to 8 dimensions.

[0026] 2) The IMU is installed on the positioning terminal and consists of an accelerometer and a gyroscope. The accelerometer measures the acceleration of the positioning terminal under different conditions, and the velocity and position information of the positioning terminal are obtained by integrating the acceleration. The error model of the accelerometer is as follows: (1) in, This indicates the actual value that the accelerometer should output; This represents the actual output value of the accelerometer; It is an accelerometer Scale factors for the three axes; It is an accelerometer Zero drift error of the three axes.

[0027] A gyroscope is used to measure the angular velocity of the positioning terminal around three fixed axes, and this is used to obtain the attitude information of the positioning terminal; the error model of the gyroscope is as follows: (2) in, This indicates the actual output of the gyroscope. Angular velocity value of the shaft, This indicates the actual values ​​that each axis of the gyroscope should output. It is the scaling factor error coefficient vector. It is a non-orthogonal error coefficient vector. It is a zero-bias vector. These are random noise vectors, and the calculation of these model parameters generally requires a high-precision turntable.

[0028] The INS state variables are: (3) in, This represents the misalignment angle error in the three directions of East, North, and Sky in the n-system; This represents the three velocity errors in the n-system; This indicates latitude error, longitude error, and altitude error; This indicates that the gyroscope in the b-series has a constant zero bias. This indicates that the accelerometer constant is zero bias in the b-series.

[0029] The state transition matrix of INS is The system noise driving matrix is The driving noise is .

[0030] 3) The state variables of NWL are: (4) In the above formula, The pseudorange error of NWL is generated by the propagation delay error of the signal received by the receiver from the transmitting station. This represents the pseudorange rate error of NWL, which is caused by the carrier frequency estimation error of the received signal from the transmitting station. In non-cooperative scenarios, the state variables of each transmitting station are solved separately.

[0031] The error state equation of NWL can be expressed as: (5) Indicates the first One launch site, The process noise vector for the NWL pseudorange error. This is the process noise vector for the NWL pseudorange rate error.

[0032] From equation (5), the system matrix of NWL is: (6) in, for The zero matrix, for The identity matrix.

[0033] The noise matrix of the driving process is: (7) in, yes The identity matrix.

[0034] The process noise vector is: (8) 4) Combine the INS state equations with the NWL state equations to obtain the state equations for the tightly coupled INS / NWL system: (9) 5) Construct the measurement equations for the tightly coupled NWL / INS positioning error model: The measurement equations of the INS / NWL integrated positioning system describe the observations, and the state variables are updated through the observations. The tight coupling uses pseudorange and pseudorange rate as measurement information.

[0035] The measurement equation is: (10) in, For measurement input, For the observation matrix, For measuring noise.

[0036] Assuming the actual location of the positioning terminal is in the Earth coordinate system (e-frame), The location of the positioning terminal obtained by INS measurement is , No. i The location of each launch station is Then locate the terminal to the first i The pseudorange of each launch station is: (11) Positioning terminal to the i The actual distance between the launch stations is: (12) The observation pseudorange of NWL can be expressed as: (13) in, For the first The pseudorange error of each launch station It is the first The pseudorange measurement noise at the transmitter station is white noise. Equation (11) is in Perform a first-order Taylor series expansion at the given point, ignoring higher-order terms, and subtract from equation (13) to obtain the pseudorange measurement equation: (14) in, , , .

[0037] The pseudorange measurement matrix of NWL obtained from equation (14) is as follows: (15) in, This is the transformation matrix from the geographic coordinate system (g system) to the geocentric coordinate system (e system). , , for A matrix consisting entirely of zeros.

[0038] Pseudorange measurement noise: (16) Differentiating equation (14) yields the pseudorange rate measurement equation: (17) From equation (17), the pseudorange rate measurement matrix of NWL is as follows: (18) in, , It is a fourth-order zero matrix. It is a fourth-order identity matrix; Pseudorange rate measurement noise: (19) Combining the pseudorange measurement equation with the pseudorange rate measurement equation yields the measurement equation for the NWL / INS tightly coupled system: (20) The pseudorange error and pseudorange rate error of the system are used as inputs to the measurement equation: Long-range non-cooperative positioning (NWL) uses the time-of-arrival (TOA) method to estimate the propagation time of non-cooperative signals transmitted from a known and fixed transmitting station, thereby obtaining the estimated distance and velocity from the carrier receiver to the transmitting station. Inertial navigation systems (INS) use an inertial navigation algorithm to calculate the attitude, velocity, and position of the current positioning terminal, and perform position calculation to obtain the estimated distance and velocity from the positioning terminal to the transmitting station. The estimated distance is called pseudorange, and the estimated velocity is called pseudorange rate. The difference between the pseudorange and pseudorange rate of the two systems is used to obtain the pseudorange error and pseudorange rate error, respectively, which serve as the measurement inputs for the measurement equations of the tightly coupled NWL / INS positioning error model in step 1.

[0039] Step 2: The Unscented Kalman Filter (UKF) algorithm is used to fuse and filter the NWL and INS information to obtain the optimal estimate and error correction value for the positioning terminal's location. Unscented Kalman filtering (UKF), suitable for nonlinear systems, is employed for tightly coupled integrated navigation of the NWL and INS to avoid errors caused by linearization. The basic filtering process of UKF mainly includes sample point selection, mathematical expectation and variance estimation calculation, and Kalman gain calculation. Substituting the measurement input from step 3 into step 2, the unscented Kalman filtering algorithm is used to fuse and filter the information from the NWL and INS to obtain the optimal estimate and output navigation information. Simultaneously, the results obtained after filtering and updating are used to correct the results calculated by the inertial navigation system and the original output of the IMU, and the pseudorange and pseudorange rate outputs of the NWL are also corrected.

[0040] Example 3 Based on Example 2, such as Figure 4 As shown, NWL uses the least squares method to locate the positioning terminal. The positioning results of NWL, INS system, and NWL / INS integrated navigation are compared to analyze their positioning accuracy, verify the superior positioning performance of the integrated navigation system, and demonstrate that the system can provide a foundation for long-range wireless navigation in GNSS denial situations. NWL consists of three or more transmitting stations and positioning terminals. After the transmitting stations transmit signals, the positioning terminals calculate the distance from each transmitting station to the positioning terminal by measuring the arrival time of the signals transmitted by each transmitting station. For example... Figure 4 As shown, the estimated values ​​of the distances r1, r2, r3, and r4 from the four transmitting stations to the positioning terminal are respectively... , , and 。 Due to the existence of estimation error, the positioning terminal is located in the intersection area of ​​four circles. NWL uses least squares to calculate the optimal estimate of the positioning terminal's position.

[0041] Following the steps above, UKF iterative updates are performed to obtain the three-dimensional output results of attitude, velocity, and position for the NWL / INS integrated navigation system. Different datasets are used for testing. Based on 100 experimental tests, the positioning performance of the NWL / INS integrated navigation system, compared to INS and NWL alone, is compared with the increase of signal-to-noise ratio (SNR). A set of relatively ideal scenarios is selected for analysis, such as... Figure 5 As shown, the average positioning error of the NWL / INS combined positioning system is stable at around 100 meters, which is better than other systems; Figure 6 As shown, the NWL / INS integrated positioning system exhibits better positioning stability, significantly outperforming NWL. In harsh environments, the tight coupling and use of NWL pseudorange as the observation means that the performance of the integrated navigation system is almost negligible due to changes in the environment. This underscores the necessity of the tight coupling approach in the NWL / INS integrated navigation system.

[0042] It is worth noting that the accuracy of the inertial navigation module has a significant impact on data acquisition. This system improves system performance by selecting a high-precision inertial navigation module. In addition, by removing data that deviates from the normal range, the model is corrected and error compensation is performed, resulting in higher accuracy and stronger stability of the navigation results.

Claims

1. A combined positioning method of long-range non-cooperative wireless positioning and inertial navigation, characterized in that, The specific steps are as follows: Step 1: Establish an NWL / INS tightly coupled integrated positioning error model based on the NWL / INS tightly coupled integrated positioning system, and construct the measurement equations and state equations of the NWL / INS tightly coupled integrated positioning error model; use the system's pseudorange error and pseudorange rate error as inputs to the measurement equations; specifically as follows: 1) The NWL / INS tightly coupled positioning system uses the northeast-sky geographic coordinate system as the navigation coordinate system, denoted as the n-system; and the right-front-upper coordinate system as the positioning terminal coordinate system, denoted as the b-system; and sets the INS error state variables to 15 dimensions and the NWL error state variables to 8 dimensions. 2) The INS error state variables are: (1) in, This represents the misalignment angle error in the three directions of East, North, and Sky in the n-system; This represents the three velocity errors in the n-system; This indicates latitude error, longitude error, and altitude error; This indicates that the gyroscope in the b-series has a constant zero bias. This indicates that the accelerometer constant has zero bias in the b-series. The state transition matrix of INS is The system noise driving matrix is The driving noise is ; 3) The NWL state variables are: (2) In the above formula, The pseudorange error of NWL is generated by the propagation delay error of the signal received by the receiver from the transmitting station. The pseudorange rate error of NWL is generated by the carrier frequency estimation error of the signal received by the receiver from the transmitting station. In non-cooperative scenarios, the state variables of each transmitting station are solved separately. The state equation of NWL is expressed as: (3) , indicating the first One launch site, The process noise vector for the NWL pseudorange error. The process noise vector for the NWL pseudorange rate error; From equation (3), the NWL state transition matrix is: (4) in, for The zero matrix, for The identity matrix; The noise matrix of the NWL driving process is: (5) in, yes The identity matrix; The process noise vector of NWL is: (6) 4) Combine the INS state equation and the NWL state equation to obtain the state equation of the tightly coupled INS / NWL positioning error model: (7) 5) Construct the measurement equations for the tightly coupled NWL / INS positioning error model: The measurement equations for the NWL / INS tightly coupled positioning error model are as follows: (8) in, For measurement input, For the observation matrix, For measuring noise; pseudorange error pseudorange rate error Combining the measurement equations of the NWL / INS tightly coupled positioning error model with Equation (8), the measurement equations of the NWL / INS tightly coupled system are obtained: (9)； Step 2: Use the Unscented Kalman Filter (UKF) algorithm to fuse and filter the NWL and INS information to obtain the optimal estimate of the positioning terminal's position error. Subtract the estimate from the position information output by the INS to calculate the final NWL / INS positioning information.

2. The combined positioning method of long-range non-cooperative wireless positioning and inertial navigation according to claim 1, characterized in that, The specific calculations for the pseudorange error and pseudorange rate error of the system in step 1 are as follows: Long-range non-cooperative positioning (NWL) uses the time-of-arrival (TOA) method to estimate the propagation time of non-cooperative signals transmitted from a known and fixed transmitting station, thereby obtaining the estimated distance and velocity from the carrier receiver to the transmitting station. Inertial navigation systems (INS) use an inertial navigation algorithm to calculate the attitude, velocity, and position of the current positioning terminal, and perform position calculation to obtain the estimated distance and velocity from the positioning terminal to the transmitting station. The estimated distance is called pseudorange, and the estimated velocity is called pseudorange rate. The pseudorange error and pseudorange rate error are obtained by subtracting the pseudorange and pseudorange rate of the NWL and INS systems, respectively.

3. The combined positioning method of long-range non-cooperative wireless positioning and inertial navigation according to claim 1, characterized in that, Step 2 is as follows: The Unscented Kalman Filter (UKF) algorithm is used to fuse and filter the information from the NWL and INS to obtain the optimal estimate of the position error. The difference between this estimate and the position information output by the INS is used to calculate the final NWL / INS positioning information. At the same time, the results obtained after the filter update are used to correct the results calculated by the INS and the original output of the IMU, and the pseudorange and pseudorange rate outputs of the NWL are also corrected to improve the positioning accuracy of the NWL.

4. The combined positioning method of long-range non-cooperative wireless positioning and inertial navigation according to claim 1, characterized in that, The tightly coupled NWL / INS positioning system includes a non-cooperative wireless positioning system (NWL) and an inertial navigation system (INS), along with a UKF filter. The NWL comprises a transmitting station that emits long-range radio signals independent of ionospheric reflection and a carrier receiver. The positioning terminal calculates the distance from each transmitting station to itself by measuring the arrival time of the signals emitted by each station. The positioning terminal is also equipped with an inertial measurement unit (IMU). The UKF filter is used for fusion filtering of INS and NWL information.

5. The combined positioning method of long-range non-cooperative wireless positioning and inertial navigation according to claim 4, characterized in that, The inertial measurement unit includes a three-axis accelerometer and a gyroscope; the accelerometer is used to measure the acceleration of the carrier receiver in different states, thereby obtaining the specific force information of the positioning terminal; the gyroscope detects the angular velocity of the carrier around three fixed axes through Coriolis force, and obtains the attitude information of the carrier receiver accordingly.

6. The combined positioning method of long-range non-cooperative wireless positioning and inertial navigation according to claim 4, characterized in that, There are three or more launch stations.

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