A Beidou information positioning method for tunnels

Abstract

The present invention relates to the field of positioning and navigation, and in particular to a Beidou information positioning method for use in tunnels. The present invention provides a method for obtaining communication transmission parameters when a vehicle communicates and transmits with a pseudo-satellite group in each positioning area at predetermined intervals, obtains a multipath effect characterization value, and adjusts the transmission power according to the multipath effect characterization value. This method achieves a real-time evaluation of the strength of the multipath effect of electromagnetic communication in the tunnel, and adaptively adjusts the transmission power based on the evaluation result, thereby improving the ability to resist the multipath effect in the complex electromagnetic environment in the tunnel, improving the accuracy of satellite positioning in the tunnel, and reducing positioning delay. The present invention considers the communication signals of different vehicles and the multipath effect characterization values ​​at corresponding moments, sets corresponding correction intervals for different vehicles, and selects different positioning strategies according to the location of the vehicle, thereby improving the positioning accuracy when the positioning system interacts with different vehicle models.

Description

Technical Field

[0001] The present invention relates to the field of positioning and navigation, and in particular to a Beidou information positioning method for use in tunnels. Background Art

[0002] Global satellite positioning and navigation systems are widely used in the transportation industry. However, obstacles such as reinforced concrete and mountains block satellite signals, making it difficult for vehicles' receiving terminals to directly receive them. To achieve satellite positioning and navigation in tunnels, technologies such as pseudolites have emerged.

[0003] For example, Chinese Patent Publication No. CN109031377A discloses a method for tunnel positioning based on pseudolites, which includes the following steps: S1. Setting m sets of pseudolites in the tunnel to form m positioning cells; S2. Maintaining the ephemeris and time of satellites inside and outside the tunnel consistent; S3. Making each set of pseudolites simulate the signals of satellites in orbit outside the tunnel; S4. Adding a Doppler frequency corresponding to the simulated vehicle speed to the carrier of each set of pseudolites, and synthesizing this frequency into the corresponding satellite signal; S5. Calibrating the vehicle positioning result; S6. Switching the pseudolites that interact with the vehicle to the pseudolites in the next positioning cell based on the satellite signal and the vehicle positioning result, thereby achieving uninterrupted positioning of the vehicle in the tunnel. This invention adjusts the Doppler frequency on the carrier of the pseudolites, allowing the location fingerprint to change rapidly and accurately, forming a location fingerprint within the tunnel, and solving the problem of difficulty in achieving satellite positioning and navigation in tunnels.

[0004] However, the prior art still has the following problems:

[0005] Pseudo-satellites are located much lower than the orbital altitude of satellites in the global positioning and navigation system. This lower altitude creates a significant multipath effect, especially in relatively closed environments such as tunnels. The multipath effect can significantly reduce positioning accuracy. Furthermore, in real-world applications, pseudo-satellites are typically spaced apart along tunnels. When a vehicle is at the center of an interval, it is far from both pseudo-satellites, resulting in fluctuating signal quality. This can easily lead to poor satellite positioning accuracy and high positioning latency. Summary of the Invention

[0006] To this end, the present invention provides a Beidou information positioning method for use in tunnels, which is used to overcome the lack of real-time evaluation of multipath effects in the existing technology, resulting in the inability to adjust the transmission power in a timely manner. When the vehicle is located at the center of the interval, it is far away from the two pseudo-satellites, and the signal quality fluctuates, which easily leads to poor satellite positioning accuracy and high positioning delay.

[0007] To achieve the above object, the present invention provides a Beidou information positioning method for use in a tunnel, comprising:

[0008] Several positioning areas are determined along the tunnel, and a pseudo-satellite group for simulating satellite signals is set in the middle of each positioning area;

[0009] Acquiring communication transmission parameters when the vehicle communicates with the pseudolite group in each positioning area, acquiring a multipath effect characterization value every predetermined period, and adjusting the transmission power according to the multipath effect characterization value;

[0010] Determine the change in the signal-to-noise ratio of the communication signal between a single vehicle and the pseudolite group when it passes through the first positioning area, so as to determine the specific time and analyze the reference distance between the vehicle and the center of the pseudolite group;

[0011] Correct the reference distance based on the multipath effect characterization value corresponding to the positioning area where the vehicle is located to determine the correction interval;

[0012] Positioning the vehicle based on whether the vehicle is in the correction interval includes:

[0013] Obtain the vehicle's positioning information at the starting point of the correction interval, locate the vehicle in combination with the vehicle's inertial navigation information, and correct the positioning;

[0014] or, positioning the vehicle based on simulated satellite signals of the vehicle and the pseudolite group;

[0015] The process of correcting the positioning includes acquiring communication signals between the vehicle and the pseudolite group, screening confidence signal segments, and correcting the positioning according to the confidence signal segments.

[0016] Furthermore, the process of obtaining the communication transmission parameters when the vehicle communicates with the pseudolite group in each positioning area at predetermined intervals includes:

[0017] Extracting the signal-to-noise ratio of the communication data received by the pseudolite group at each moment and determining the mean value of the signal-to-noise ratio;

[0018] Extracting the time delay and amplitude of each main reflection path signal in the communication data received by the pseudolite group at each moment, and determining the mean time delay and mean amplitude corresponding to each moment;

[0019] Determine the mean variance of the delay and the mean variance of the amplitude corresponding to each moment;

[0020] The signal-to-noise ratio mean, delay mean variance and amplitude mean variance are determined as communication transmission parameters.

[0021] Furthermore, the process of obtaining a multipath effect characterization value and adjusting the transmit power according to the multipath effect characterization value includes:

[0022] Determining the ratio of the signal-to-noise ratio mean to a predetermined signal-to-noise ratio threshold as a signal-to-noise ratio influencing factor;

[0023] Determining a ratio of a delay mean variance to a predetermined delay variance threshold as a delay influencing factor;

[0024] determining a ratio of the amplitude mean variance to a predetermined amplitude variance threshold as an amplitude influencing factor;

[0025] The multipath effect characterization value is obtained by weighted summing the signal-to-noise ratio influencing factors, the delay influencing factors, and the amplitude influencing factors.

[0026] The transmit power is adjusted based on the multipath effect characterization value, and the adjusted transmit power is positively correlated with the multipath effect characterization value.

[0027] Furthermore, the process of determining the change in the signal-to-noise ratio of the communication signal between the single vehicle and the pseudolite group when the single vehicle passes through the first positioning area to determine the specific time includes:

[0028] Continuously obtain the signal-to-noise ratio of the communication signal between the vehicle and the pseudo-satellite group when the vehicle passes through the first positioning area;

[0029] When the signal-to-noise ratio is lower than the preset signal-to-noise ratio threshold for the first time, the corresponding moment is marked as the special moment.

[0030] Furthermore, the process of analyzing the reference distance between the correction region and the center of the pseudolite group includes:

[0031] Obtain the vehicle's positioning coordinates at a specific moment;

[0032] The distance between the vehicle and the center of the pseudolite group is determined based on the positioning coordinates, and the distance is determined as a reference distance.

[0033] Furthermore, the process of correcting the reference distance based on the multipath effect characterization value corresponding to the positioning area where the vehicle is located includes:

[0034] The corrected reference distance is negatively correlated with the multipath effect characterization value.

[0035] Furthermore, the process of determining the correction interval includes,

[0036] Obtaining the corrected reference distance;

[0037] Determine the starting point of the correction interval based on the center of the pseudolite group in the current positioning area and the reference distance;

[0038] Determine the end point of the correction interval based on the center of the pseudolite group of the adjacent next positioning area and the reference distance;

[0039] The correction interval is determined based on the correction interval start point and the correction interval end point.

[0040] Further, based on whether the vehicle is in the correction interval, the vehicle is positioned, including:

[0041] If the vehicle is located in the non-correction interval, positioning the vehicle based on the simulated satellite signals of the vehicle and the pseudolite group;

[0042] If the vehicle is located within the correction interval of the positioning area, the positioning information of the vehicle at the starting point of the correction interval is obtained, the vehicle is positioned in combination with the vehicle's inertial navigation information, and the positioning is corrected.

[0043] Further, obtaining the positioning information of the vehicle at the starting point of the correction interval, positioning the vehicle in combination with the vehicle's inertial navigation information, and correcting the positioning, positioning the vehicle in combination with the vehicle's inertial navigation information, including,

[0044] Obtaining the vehicle's positioning information when the vehicle reaches a predetermined distance before the starting point of the correction interval;

[0045] Determine the vehicle's speed and direction based on the vehicle's inertial navigation information;

[0046] The vehicle's positioning information at each moment is predicted based on positioning information and inertial navigation information.

[0047] Furthermore, the process of correcting the positioning includes:

[0048] Continuously obtaining a multipath effect characterization value of the communication signal when the vehicle passes through the correction interval;

[0049] If the multipath effect characterization value at the time of existence is lower than the preset correction threshold, determining the communication signal at the time of existence as a confidence signal segment;

[0050] Positioning the vehicle based on the confidence signal segment to obtain corrected positioning information;

[0051] Updating the current location of the vehicle to the corrected location information;

[0052] The vehicle is positioned based on the corrected positioning information in combination with vehicle inertial navigation information.

[0053] Compared with the prior art, the beneficial effect of the present invention lies in that, by setting the steps of obtaining the communication transmission parameters of the vehicle when communicating with the pseudo-satellite group in each of the positioning areas at predetermined intervals, obtaining the multipath effect characterization value, and adjusting the transmission power according to the multipath effect characterization value, the present invention realizes real-time evaluation of the strength of the multipath effect of electromagnetic communication in the tunnel, and adaptively adjusts the transmission power according to the evaluation result, thereby improving the ability to resist the multipath effect in the complex electromagnetic environment in the tunnel, improving the accuracy of satellite positioning in the tunnel, and reducing positioning delay. The present invention considers the communication signals of different vehicles and the multipath effect characterization values ​​at the corresponding time, sets corresponding correction intervals for different vehicles, and selects different positioning strategies according to the location of the vehicle, thereby improving the positioning accuracy when the positioning system interacts with different vehicle models.

[0054] In particular, the present invention considers changes in the signal-to-noise ratio (SNR) when a single vehicle passes through its first positioning area, marking specific time points. As the vehicle travels, it moves away from the pseudolite group in the current positioning area, causing the communication transmission quality between the vehicle and the pseudolite group to degrade. When crossing the positioning area, the vehicle is far away from both pseudolites. Due to the superposition of multipath effects, the communication quality between the vehicle and the pseudolite group is prone to fluctuations. In addition, the signal transceiver capabilities of different vehicles vary in actual applications. Therefore, the present invention considers identifying correction intervals with significant signal quality degradation based on the corresponding SNR changes when the vehicle passes through the first positioning area. It then adaptively constructs a reference distance for the corresponding vehicle to support the subsequent determination of the length of the correction interval. This allows the vehicle to use different positioning methods in the correction interval and the non-correction interval, ensuring continuous and uninterrupted navigation and positioning of the vehicle, reducing navigation and positioning failures caused by disconnection or distortion of the simulated satellite signal at a certain moment, and ensuring accurate positioning of the vehicle in tunnels.

[0055] In particular, the present invention adaptively corrects the reference distance. In actual situations, the traffic density and tunnel environment in different positioning areas may be different, which will affect the multipath effect. Therefore, the present invention adaptively corrects the reference distance. The change of the reference distance will affect the length of the correction interval, so that the correction interval can better match the current vehicle, provide support for the subsequent use of different positioning methods, and thus ensure the accuracy of vehicle positioning in the tunnel.

[0056] In particular, the present invention enables a vehicle to adopt different positioning methods in the correction interval and the non-correction interval during tunnel driving. Outside the correction interval, the communication quality between the vehicle and the pseudo-satellite group is better and can be directly positioned. Within the correction interval, the vehicle is relatively far away from the two adjacent pseudo-satellite groups, and the signal is easily distorted. Therefore, when the vehicle is in the correction interval, positioning is performed by combining the positioning information of the vehicle at the starting point of the correction interval and the vehicle's own inertial navigation system. This can meet the accuracy requirements in a short period of time, but the error will increase over time. Therefore, the present invention considers identifying confident signal segments and timely correcting the positioning by screening out high-confidence satellite positioning data, thereby improving the reliability of the positioning results within the correction interval, allowing the vehicle to be continuously positioned in the tunnel, reducing the problem of discontinuous positioning caused by distortion of the communication signal with the pseudo-satellite group in some areas, and ensuring the accuracy of the vehicle's positioning in the tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 A schematic diagram of the steps of a Beidou information positioning method for use in a tunnel according to an embodiment of the invention;

[0058] Figure 2 This is a schematic diagram of the correction interval of an embodiment of the invention;

[0059] Figure 3A logic block diagram of positioning the vehicle based on whether the vehicle is in the correction zone according to an embodiment of the invention;

[0060] Figure 4 A logic block diagram of screening confidence signal segments according to an embodiment of the invention; DETAILED DESCRIPTION

[0061] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0062] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0063] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0064] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0065] See also Figure 1 As shown, it is a schematic diagram of the steps of the Beidou information positioning method for a tunnel according to an embodiment of the present invention. The Beidou information positioning method for a tunnel according to the present invention includes:

[0066] Step S1, determining a plurality of positioning areas along the tunnel, wherein a pseudolite group for simulating satellite signals is provided in the middle of each positioning area;

[0067] Step S2, obtaining communication transmission parameters when the vehicle communicates with the pseudolite group in each positioning area, obtaining a multipath effect characterization value every predetermined period, and adjusting the transmission power according to the multipath effect characterization value;

[0068] Step S3, determining the change in the signal-to-noise ratio of the communication signal between a single vehicle and the pseudolite group when passing through the first positioning area, so as to mark a specific time point and analyze the reference distance between the vehicle and the center of the pseudolite group;

[0069] Step S4, correcting the reference distance based on the multipath effect characterization value corresponding to the positioning area where the vehicle is located to determine a correction interval;

[0070] Step S5, positioning the vehicle based on whether the vehicle is in the correction interval, including:

[0071] Obtaining the positioning information of the vehicle at the starting point of the correction interval, positioning the vehicle in combination with the inertial navigation information of the vehicle, and correcting the positioning;

[0072] or, positioning the vehicle based on simulated satellite signals of the vehicle and the pseudolite group;

[0073] The process of correcting the positioning includes acquiring communication signals between the vehicle and the pseudolite group, screening confidence signal segments, and correcting the positioning according to the confidence signal segments.

[0074] Specifically, there is no limitation on the structure of the pseudo-satellite group. The pseudo-satellite group is usually arranged on the upper surface of the tunnel at the same intervals to receive satellite signals from extraterrestrial satellites and communicate with vehicles on the ground. For example, the pseudo-satellite group can be connected to the relay satellite antenna arranged outside the tunnel via optical fiber. The relay satellite antenna communicates with the Beidou positioning system and forwards the satellite signals to the pseudo-satellite group.

[0075] Specifically, the midpoints between the pseudo-satellite groups can be used as dividing points to divide the tunnel into several pseudo-positioning areas, which will not be described in detail.

[0076] It can be understood that the pseudo-satellite groups in each positioning area are connected in sequence along the axial direction of the tunnel. The connection can be a wired connection, such as optical fiber, or a wireless connection, such as using 5G signals in the tunnel for communication. In an embodiment of the present invention, optical fiber is used to connect the pseudo-satellite groups.

[0077] Specifically, see Figure 2 As shown, Figure 2This is a schematic diagram of the correction interval according to an embodiment of the present invention. After entering the tunnel, the vehicle enters the non-correction interval of the positioning area from point A. The vehicle communicates with the pseudo-satellite in the positioning area and performs positioning based on simulated satellite signals. As the vehicle reaches point B, it enters the correction interval. Within this interval, the vehicle is positioned based on its inertial navigation information. Because the correction interval spans two adjacent positioning areas, the vehicle reaches point C and enters the non-correction interval of the next adjacent positioning area. The vehicle enters the correction interval again after reaching point D, and then enters the non-correction interval again after passing through points E and F. The vehicle then travels back and forth between the correction interval and the non-correction interval until it exits the tunnel.

[0078] Specifically, the process of obtaining the communication transmission parameters when the vehicle communicates with the pseudolite group in each positioning area at predetermined intervals includes:

[0079] Extracting the signal-to-noise ratio of the communication data received by the pseudolite group at each moment and determining the mean value of the signal-to-noise ratio;

[0080] Extracting the time delay and amplitude of each main reflection path signal in the communication data received by the pseudolite group at each moment, and determining the mean time delay and mean amplitude corresponding to each moment;

[0081] Determine the mean variance of the delay and the mean variance of the amplitude corresponding to each moment;

[0082] The signal-to-noise ratio mean, delay mean variance and amplitude mean variance are determined as communication transmission parameters.

[0083] Specifically, the predetermined period is set within the interval [30s, 60s].

[0084] Specifically, the main reflection path signal refers to a reflection path signal that is more obvious in the multipath effect and significantly interferes with the main path signal. In this embodiment of the present invention, a filter is used to filter out reflection path signals with a strength greater than 0.03% of the main path signal, and the filtered signal is determined as the main reflection path signal.

[0085] Specifically, the process of obtaining the multipath effect characterization value and adjusting the transmit power according to the multipath effect characterization value includes:

[0086] Determining the ratio of the signal-to-noise ratio mean to a predetermined signal-to-noise ratio threshold as a signal-to-noise ratio influencing factor;

[0087] Determining a ratio of a delay mean variance to a predetermined delay variance threshold as a delay influencing factor;

[0088] determining a ratio of the amplitude mean variance to a predetermined amplitude variance threshold as an amplitude influencing factor;

[0089] The multipath effect characterization value is obtained by weighted summing the signal-to-noise ratio influencing factors, the delay influencing factors, and the amplitude influencing factors.

[0090] The transmit power is adjusted based on the multipath effect characterization value, and the adjusted transmit power is positively correlated with the multipath effect characterization value.

[0091] Specifically, the signal-to-noise ratio threshold, the delay variance threshold, and the amplitude variance threshold are all pre-set. The communication transmission parameters of several vehicles passing through the tunnel and communicating with the pseudo-satellite group during a historical period are pre-stated, and the signal-to-noise ratio mean, delay mean variance, and amplitude mean variance corresponding to the vehicles are recorded. A first mean of the signal-to-noise ratio mean, a second mean of the delay mean variance, and a third mean of the amplitude mean variance corresponding to each vehicle are solved. The first mean is set as the signal-to-noise ratio threshold, the second mean is set as the delay variance threshold, and the third mean is set as the amplitude variance threshold. The historical period can be set to 1 week.

[0092] Specifically, in the embodiment of the present invention, the weighted weight of the delay influencing factor is 0.3, the weighted weight of the amplitude influencing factor is 0.3, and the weighted weight of the signal-to-noise ratio influencing factor is 0.4.

[0093] It can be understood that the multipath effect characterization value in the tunnel under normal conditions is close to 1, and when the multipath effect characterization value is larger, the transmit power is adjusted accordingly;

[0094] In implementation, optionally,

[0095] When the multipath effect characterization value is in [0,1.15), the pseudolite group transmit power uses the initial power;

[0096] When the multipath effect characterization value is in [1.15, 1.35), the transmission power of the pseudolite group is 1.15 times the initial power;

[0097] When the multipath effect characterization value is in [1.35,+∞), the power of the pseudo-satellite group is 1.35 times the initial power.

[0098] Specifically, the process of determining the change in the signal-to-noise ratio of the communication signal between a single vehicle and the pseudolite group when the vehicle passes through the first positioning area to determine the specific time includes:

[0099] Continuously obtain the signal-to-noise ratio of the communication signal between the vehicle and the pseudo-satellite group when the vehicle passes through the first positioning area;

[0100] When the signal-to-noise ratio is lower than the preset signal-to-noise ratio threshold for the first time, the corresponding moment is marked as the special moment.

[0101] In implementation, the signal-to-noise ratio threshold is predetermined, where

[0102] Record the lowest signal-to-noise ratio when several vehicles pass through the tunnel and communicate with each pseudo-satellite group;

[0103] The lowest mean signal-to-noise ratio is solved, and the signal-to-noise ratio threshold is set to the product of the lowest mean signal-to-noise ratio and the deviation coefficient. The deviation coefficient is selected in the interval [1.25, 1.35].

[0104] It is understandable that as the vehicle moves away from the pseudolite group at the center of the positioning area, the signal strength between the vehicle and the pseudolite group during the communication transmission process also attenuates, thereby reducing the signal-to-noise ratio.

[0105] In some cases, the signal-to-noise ratio of the communication signal between the vehicle and the pseudo-satellite group passing through the first positioning area may be greater than the preset signal-to-noise ratio threshold. In this case, there is no specific moment, no correction interval, and only a non-correction interval.

[0106] Specifically, the process of analyzing the reference distance between the vehicle and the center of the pseudolite group includes:

[0107] Obtain the vehicle's positioning coordinates at a specific moment. At this time, the positioning coordinates can be determined based on communication transmission between the vehicle and the pseudo-satellite group, and the vehicle positioning coordinates are determined using simulated satellite signals. Satellite positioning is an existing technology and will not be described in detail here.

[0108] The distance between the vehicle and the center of the pseudolite group is determined based on the positioning coordinates, and the distance is determined as a reference distance.

[0109] The present invention considers changes in the signal-to-noise ratio (SNR) when a single vehicle passes through its first positioning area and marks specific time points. As the vehicle travels, it moves away from the pseudolite group in the current positioning area, causing the communication transmission quality between the vehicle and the pseudolite group to degrade. When crossing the positioning area, the vehicle is far away from both pseudolites. Due to the superposition of multipath effects, the communication quality between the vehicle and the pseudolite group is prone to fluctuations. In addition, the signal transceiver capabilities of different vehicles vary in actual applications. Therefore, the present invention considers identifying a correction interval with significant signal quality degradation based on the corresponding SNR change when the vehicle passes through the first positioning area. It then adaptively constructs a reference distance for the corresponding vehicle to support the subsequent determination of the length of the correction interval. This allows the vehicle to use different positioning methods in the correction interval and the non-correction interval, ensuring continuous and uninterrupted navigation and positioning of the vehicle, reducing navigation and positioning failures caused by disconnection or distortion of the simulated satellite signal at a certain moment, and ensuring accurate positioning of the vehicle in tunnels.

[0110] Specifically, the process of correcting the reference distance based on the multipath effect characterization value corresponding to the positioning area where the vehicle is located includes:

[0111] The corrected reference distance is negatively correlated with the multipath effect characterization value.

[0112] Specifically, a correction coefficient is determined according to the multipath effect characterization value, and the product of the reference distance and the correction coefficient is used as the corrected reference distance.

[0113] In implementation, optionally,

[0114] When the ratio of the multipath effect characterization value to the preset multipath effect threshold is in [0, 1.05), the correction coefficient is 1.0;

[0115] When the ratio of the multipath effect characterization value to the preset multipath effect threshold is in [1.26, +∞), the correction coefficient is 0.8.

[0116] Specifically, the process of determining the correction interval includes:

[0117] Obtaining the corrected reference distance;

[0118] Determine the starting point of the correction interval based on the center of the pseudolite group in the current positioning area and the reference distance;

[0119] Determine the end point of the correction interval based on the center of the pseudolite group of the adjacent next positioning area and the reference distance;

[0120] The correction interval is determined based on the correction interval start point and the correction interval end point.

[0121] In implementation, the reference distance from the center of the pseudolite group in the positioning area is set as the starting point of the correction interval, and the reference distance from the center of the pseudolite group in the next adjacent positioning area is set as the starting point of the correction interval;

[0122] Please continue reading Figure 2 As shown, E1 is the center of the pseudo-satellite group in the positioning area, and the distance from E1 to point B is the reference distance. Point B is the starting point of the correction interval, and the distance from E2 to point C, the center of the pseudo-satellite group in the next adjacent positioning area, is the reference distance. Point C is the end point of the correction interval.

[0123] See also Figure 3 , Figure 3 A logic block diagram of positioning the vehicle based on whether the vehicle is in the correction zone according to an embodiment of the invention;

[0124] Specifically, based on whether the vehicle is in the correction interval, the vehicle is positioned, including:

[0125] If the vehicle is located in the non-correction interval, positioning the vehicle based on the simulated satellite signals of the vehicle and the pseudolite group;

[0126] If the vehicle is located within the correction interval of the positioning area, the positioning information of the vehicle at the starting point of the correction interval is obtained, the vehicle is positioned in combination with the vehicle's inertial navigation information, and the positioning is corrected.

[0127] The present invention adaptively corrects the reference distance. In actual situations, the traffic density and tunnel environment in different positioning areas may be different, which will affect the multipath effect. Therefore, the present invention adaptively corrects the reference distance. The change of the reference distance will affect the length of the correction interval, so that the correction interval can better match the current vehicle, providing support for the subsequent use of different positioning methods, thereby ensuring the accuracy of vehicle positioning in the tunnel.

[0128] Specifically, the positioning information of the vehicle at the starting point of the correction interval is obtained, the vehicle is positioned in combination with the vehicle's inertial navigation information, and the positioning is corrected, and the positioning of the vehicle is positioned in combination with the vehicle's inertial navigation information, including:

[0129] Obtaining the vehicle's positioning information when the vehicle reaches a predetermined distance before the starting point of the correction interval;

[0130] Determine the vehicle's speed and direction based on the vehicle's inertial navigation information;

[0131] The vehicle's positioning information at each moment is predicted based on positioning information and inertial navigation information.

[0132] In practice, the predetermined distance is selected within the interval [5m, 10m].

[0133] Specifically, the vehicle's positioning information includes the vehicle's position coordinates. Based on the vehicle's position coordinates at a single moment, and on the premise of knowing the vehicle's moving speed and direction, the vehicle's subsequent position coordinates at each moment can be predicted. This will not be repeated here.

[0134] The present invention enables a vehicle to adopt different positioning methods in the correction interval and the non-correction interval during tunnel driving. Outside the correction interval, the communication quality between the vehicle and the pseudo-satellite group is better and can be directly positioned. Within the correction interval, the vehicle is relatively far away from the two adjacent pseudo-satellite groups, and the signal is easily distorted. Therefore, when the vehicle is in the correction interval, positioning is performed by combining the positioning information of the vehicle at the starting point of the correction interval and the vehicle's own inertial navigation system. This can meet the accuracy requirements in a short period of time, but the error will increase over time. Therefore, the present invention considers identifying confident signal segments and timely correcting the positioning by screening out high-confidence satellite positioning data, thereby improving the reliability of the positioning results within the correction interval, allowing the vehicle to be continuously positioned in the tunnel, reducing the problem of discontinuous positioning caused by distortion of the communication signal with the pseudo-satellite group in some areas, and ensuring the accuracy of the vehicle's positioning in the tunnel.

[0135] See also Figure 4 , Figure 4 A logic block diagram of screening confidence signal segments according to an embodiment of the invention;

[0136] Specifically, the process of correcting the positioning includes:

[0137] Continuously obtaining a multipath effect characterization value of the communication signal when the vehicle passes through the correction interval;

[0138] If the multipath effect characterization value at the time of existence is lower than the preset correction threshold, determining the communication signal at the time of existence as a confidence signal segment;

[0139] Positioning the vehicle based on the confidence signal segment to obtain corrected positioning information;

[0140] Updating the current location of the vehicle to the corrected location information;

[0141] The vehicle is positioned based on the corrected positioning information in combination with vehicle inertial navigation information.

[0142] Specifically, in the embodiment of the present invention, the preset correction threshold is 0.9 times the preset multipath effect threshold.

[0143] It can be understood that the confidence signal segment contains simulated satellite signals, which can be used to obtain the vehicle's positioning information, and then used as corrected positioning information. Since the inertial navigation information contains the vehicle's moving speed and direction, the position coordinates of the subsequent vehicle can be predicted based on the corrected positioning information, moving speed and direction. This will not be repeated here.

[0144] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A Beidou information positioning method for use in tunnels, characterized in that: include: A plurality of positioning areas are determined along the tunnel, and a pseudo-satellite group for simulating satellite signals is set in the middle of each positioning area; Acquiring communication transmission parameters when the vehicle communicates with the pseudolite group in each positioning area, acquiring a multipath effect characterization value every predetermined period, and adjusting the transmission power according to the multipath effect characterization value; Determine the change in the signal-to-noise ratio of the communication signal between a single vehicle and the pseudolite group when it passes through the first positioning area, so as to mark the specific time point and analyze the reference distance between the vehicle and the center of the pseudolite group; Correcting the reference distance based on the multipath effect characterization value corresponding to the positioning area where the vehicle is located to determine a correction interval; Positioning the vehicle based on whether the vehicle is in the correction interval, include, Obtaining the positioning information of the vehicle at the starting point of the correction interval, positioning the vehicle in combination with the inertial navigation information of the vehicle, and correcting the positioning; or, positioning the vehicle based on simulated satellite signals of the vehicle and the pseudolite group; The process of correcting the positioning includes obtaining a communication signal between the vehicle and the pseudolite group, screening a confidence signal segment, and correcting the positioning according to the confidence signal segment; The process of determining the change in the signal-to-noise ratio of the communication signal between a single vehicle and the pseudolite group when the vehicle passes through the first positioning area to determine the specific time includes: Continuously acquiring a signal-to-noise ratio of a communication signal between the vehicle and the pseudolite group while passing through the first positioning area; When the signal-to-noise ratio falls below a preset signal-to-noise ratio threshold for the first time, marking the corresponding moment as the special moment; The process of analyzing the reference distance of the center of the vehicle pseudolite group includes: Obtaining the positioning coordinates of the vehicle at the specific moment; The distance between the vehicle and the center of the pseudolite group is determined based on the positioning coordinates, and the distance is determined as a reference distance.

2. The Beidou information positioning method for use in tunnels according to claim 1, characterized in that: The process of obtaining the communication transmission parameters when the vehicle communicates with the pseudolite group in each positioning area at predetermined intervals includes: Extracting the signal-to-noise ratio of the communication data received by the pseudolite group at each moment and determining the mean value of the signal-to-noise ratio; Extracting the time delay and amplitude of each main reflection path signal in the communication data received by the pseudolite group at each moment, and determining the mean time delay and mean amplitude corresponding to each moment; Determine the mean variance of the delay and the mean variance of the amplitude corresponding to each moment; The signal-to-noise ratio mean, delay mean variance, and amplitude mean variance are determined as communication transmission parameters.

3. The Beidou information positioning method for use in tunnels according to claim 2, characterized in that: The process of obtaining a multipath effect characterization value and adjusting the transmit power according to the multipath effect characterization value includes: Determining the ratio of the signal-to-noise ratio mean to a predetermined signal-to-noise ratio threshold as a signal-to-noise ratio influencing factor; Determining a ratio of a delay mean variance to a predetermined delay variance threshold as a delay influencing factor; determining a ratio of the amplitude mean variance to a predetermined amplitude variance threshold as an amplitude influencing factor; The multipath effect characterization value is obtained by weighted summing the signal-to-noise ratio influencing factor, the delay influencing factor, and the amplitude influencing factor; The transmit power is adjusted based on the multipath effect characterization value, and the adjusted transmit power is positively correlated with the multipath effect characterization value.

4. The Beidou information positioning method for use in tunnels according to claim 1, characterized in that: The process of correcting the reference distance based on the multipath effect characterization value corresponding to the positioning area where the vehicle is located includes: The corrected reference distance is negatively correlated with the multipath effect characterization value.

5. The Beidou information positioning method for use in tunnels according to claim 1, characterized in that: The process of determining the correction interval includes: Obtaining the corrected reference distance; Determine the starting point of the correction interval based on the center of the pseudolite group in the current positioning area and the reference distance; Determine the end point of the correction interval based on the center of the pseudolite group of the adjacent next positioning area and the reference distance; A correction interval is determined based on the correction interval start point and the correction interval end point.

6. The Beidou information positioning method for use in tunnels according to claim 1, characterized in that: The positioning of the vehicle based on whether the vehicle is in the correction interval includes: If the vehicle is located in the non-correction interval, positioning the vehicle based on the simulated satellite signals of the vehicle and the pseudolite group; If the vehicle is located within the correction interval of the positioning area, the positioning information of the vehicle at the starting point of the correction interval is obtained, the vehicle is positioned in combination with the inertial navigation information of the vehicle, and the positioning is corrected.

7. The Beidou information positioning method for use in tunnels according to claim 6, characterized in that: Positioning the vehicle in combination with the inertial navigation information of the vehicle includes: Obtaining positioning information of the vehicle when the vehicle reaches a predetermined distance before the starting point of the correction interval; Determine the vehicle's speed and direction based on the vehicle's inertial navigation information; The positioning information of the vehicle at each moment is predicted based on the positioning information and the inertial navigation information.

8. The Beidou information positioning method for use in tunnels according to claim 7, characterized in that: The process of correcting the positioning includes: Continuously obtaining a multipath effect characterization value of the communication signal when the vehicle passes through the correction interval; If the multipath effect characterization value at the time of existence is lower than the preset correction threshold, determining the communication signal at the time of existence as a confidence signal segment; Positioning the vehicle based on the confidence signal segment to obtain corrected positioning information; Updating the current location of the vehicle to the corrected location information; The vehicle is positioned based on the corrected positioning information in combination with vehicle inertial navigation information.

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