CN117896791B

CN117896791B - Tunnel vehicle-mounted auxiliary seamless roaming method and system based on inertial navigation

Info

Publication number: CN117896791B
Application number: CN202410277029.8A
Authority: CN
Inventors: 熊严明
Original assignee: Wuhan Zhihui Subway Tech Co ltd
Current assignee: Wuhan Zhihui Subway Tech Co ltd
Priority date: 2024-03-12
Filing date: 2024-03-12
Publication date: 2024-05-28
Anticipated expiration: 2044-03-12
Also published as: CN117896791A

Abstract

The invention discloses a tunnel vehicle-mounted auxiliary seamless roaming method and system based on inertial navigation, wherein the method comprises the following steps: measuring train dynamic data in real time through an inertial navigation sensor; according to the dynamic data of the train, carrying out attitude calculation and determining the position of the train from the target base station; monitoring surrounding neighbor APs through active scanning to obtain received signal strength indication RSSI of the neighbors and analyzing the RSSI to obtain a slope k; determining whether to switch to the target AP by determining the difference between the RSSI value of the target AP with the largest RSSI value in the neighbor list and the RSSI value of the currently connected AP and whether to continuously switch to the target AP three times in a preset interval, determining whether the slope k of the currently connected AP is smaller than a certain negative threshold value, determining whether the slope k of the target AP is larger than a certain positive threshold value, and determining whether the current train position is larger than or equal to a preset optimal switching position. The invention can quickly find the optimal switching point of the vehicle-mounted wireless access point and ensure the switching communication quality.

Description

Tunnel vehicle-mounted auxiliary seamless roaming method and system based on inertial navigation

Technical Field

The invention relates to the field of rail transit, in particular to a tunnel vehicle-mounted motion unit auxiliary seamless roaming method and system based on inertial navigation.

Background

As shown in fig. 1, the conventional switching scenario of the subway vehicle-mounted motion unit is considered to be switched at a Point a through RSSI (signal strength Indication received by RECEIVED SIGNAL STRENGTH Indication) according to surrounding APs (WIRELESS ACCESS Point, wireless access Point, commonly called "hot spot") detected by the vehicle-mounted wireless unit, and the communication quality of the Point a is not necessarily the optimal switching Point in theory in the face of the switching scenario under the complex tunnel environment. From a practical point of view, it is theorized that the base stations AP1 and AP2 are installed in the tunnel, there is actually an optimal switching point between them, possibly a point B or a point C, and each optimal switching timing must be near the optimal switching point when the train passes nearby,

When a conventional subway vehicle-mounted motion unit performs switching, whether a single radio (wireless network card communication) or a dual radio is required, the following steps are definitely performed if the conventional subway vehicle-mounted motion unit is subjected to standard switching: as shown in FIG. 2, the air interface interaction cost required by each switching is 2-3s, and the packet loss is serious, and even if the 802.11r protocol is started, the following 4-step key interaction is omitted, the consumption caused by the air interface cost still cannot be solved qualitatively.

Disclosure of Invention

The invention mainly aims to provide an inertial navigation-based tunnel vehicle-mounted moving unit auxiliary seamless roaming method and system which can assist tunnel vehicle-mounted and surrounding wireless access points to perform rapid switching and are high in switching quality.

The technical scheme adopted by the invention is as follows:

the utility model provides a tunnel vehicle-mounted motion unit auxiliary seamless roaming method based on inertial navigation, which comprises the following steps:

S1, measuring train dynamic data in real time through an inertial navigation sensor, wherein the data comprise acceleration, angular velocity and magnetic field of train movement;

S2, carrying out attitude calculation according to the dynamic data of the train, updating the position of the train, and determining the position of the train from the target base station;

S3, monitoring surrounding neighbor APs through active scanning to obtain received signal strength indication RSSI of the neighbors, inserting the received signal strength indication RSSI into a corresponding neighbor list, and analyzing the RSSI value of each neighbor for a period of time to obtain a slope k reflecting the change speed of each neighbor;

s4, judging whether the difference between the RSSI value of the target AP with the largest RSSI value in the neighbor list and the currently connected AP is larger than or equal to a preset threshold value, and if not, executing the step S5; if yes, executing step S6;

s5, judging whether the difference between the RSSI value of the target AP with the largest RSSI value in the neighbor list and the RSSI value of the currently connected AP is continuously in a preset interval for a plurality of times, if so, executing the step S6, otherwise, returning to the step S1;

S6, judging whether the slope k of the currently connected AP is smaller than a certain negative threshold value, judging whether the slope k of the target AP is larger than a certain positive threshold value, if so, executing the step S7, and if not, returning to the step S1;

s7, judging whether the current train position is larger than or equal to a preset optimal switching position, if so, executing the step S8, otherwise, returning to the step S1;

s8, switching to the target AP.

In the technical scheme, step S1 further comprises performing second-order low-pass filtering processing on the real-time measurement train dynamic data.

In step S2, the attitude calculation is performed by specifically adopting a direction cosine matrix algorithm.

In step S2, the gesture calculation is specifically performed by using a quaternion algorithm.

In step S3, the slope k is calculated by the least square method.

With the above technical solution, the neighbor list is based on a hash table, and the index is the MAC address of the currently connected AP.

By adopting the technical scheme, the vehicle-mounted wireless unit obtains the latest scanning result through active scanning, inserts the latest scanning result into the corresponding neighbor list, and performs aging treatment in a timing way.

The invention also provides a tunnel vehicle-mounted motion unit auxiliary seamless roaming system based on inertial navigation, which comprises the following steps:

The data acquisition module is used for measuring train dynamic data in real time through the inertial navigation sensor, wherein the data comprises acceleration, angular velocity and magnetic field of train movement;

the attitude calculation module is used for carrying out attitude calculation according to the dynamic data of the train, updating the position of the train and determining the position of the train from the target base station;

The neighbor monitoring module is used for monitoring surrounding neighbor APs through active scanning to obtain the received signal strength indication RSSI of the neighbors, inserting the received signal strength indication RSSI into a corresponding neighbor list, and analyzing the RSSI value of each neighbor for a period of time to obtain a slope k reflecting the change speed of the RSSI value;

The first judging module is used for judging whether the difference between the RSSI value of the target AP with the largest RSSI value in the neighbor list and the currently connected AP is larger than or equal to a preset threshold value, and if not, the second judging module is shifted to execute; if yes, the third judging module is switched to execute;

The second judging module is used for judging whether the difference between the RSSI value of the target AP with the largest RSSI value in the neighbor list and the currently connected AP is in a preset interval or not three times continuously, if so, the third judging module is switched to execute, and the data acquisition module is switched to execute;

The third judging module is used for judging whether the slope k of the currently connected AP is smaller than a certain negative threshold value or not, judging whether the slope k of the target AP is larger than a certain positive threshold value or not, if yes, switching to the fourth judging module for execution, and if no, switching to the data acquisition module for execution;

And the fourth judging module is used for judging whether the current train position is greater than or equal to a preset optimal switching position, if so, switching to the target AP, and if not, switching to the data acquisition module for execution.

By adopting the technical scheme, the system also comprises a data processing module which is used for carrying out second-order low-pass filtering processing on the dynamic data of the real-time measurement train.

The invention also provides a computer storage medium, in which a computer program executable by a processor is stored, and the computer program executes the tunnel vehicle-mounted moving unit assisted seamless roaming method based on inertial navigation.

The invention has the beneficial effects that: the invention measures the dynamic data of the train in real time through the inertial navigation sensor, including the acceleration, angular velocity and magnetic field of the train movement, and takes the train position calculated in real time as the input condition of the roaming switching opportunity decision; after the position of the train from the target base station is determined, the judgment threshold value of the RSSI is reduced near the optimal switching point, so that the actual switching point is near the optimal switching point, and the maximum air interface bandwidth and the switching quality can be ensured.

Furthermore, the invention provides a wireless distributed system mechanism based on no association, which realizes seamless switching of dual radio, ensures switching without air interface interaction, and only performs switching on a communication data link, thereby realizing the effect that switching is within 50ms and on average about 15ms, and the packet loss rate is less than 0.001%, even zero packet loss.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic diagram of a conventional subway vehicle-mounted motion unit switching scene;

FIG. 2 is a flow chart of a conventional subway on-board movement unit when performing a switch;

FIG. 3 is a flow chart of a tunnel vehicle motion unit assisted seamless roaming method based on inertial navigation according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of inertial navigation sensor data acquisition, calculation and transmission according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a geographic coordinate system R;

FIG. 6A is a schematic diagram of a world reference frame;

FIG. 6B is a schematic diagram of a carrier coordinate system;

FIG. 7A is a schematic view of rotation about the Z axis;

FIG. 7B is a schematic view of rotation about Y;

FIG. 7C is a schematic view of rotation about the X axis;

FIG. 8A is a diagram of a side-base station neighbor relation;

FIG. 8B is a schematic diagram II of the most common neighbor relation of the secondary base station;

FIG. 9 is a stored version of a neighbor list according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of an active scan mode according to an embodiment of the present invention;

FIG. 11 is a diagram of scan result storage according to an embodiment of the present invention;

FIG. 12 is a flow chart of a tunnel vehicle motion unit assisted seamless roaming method based on inertial navigation according to an embodiment of the present invention;

FIG. 13 is a schematic diagram of setting up the dead zone of 6 db before and after in order to prevent repeated hops according to the embodiment of the present invention;

fig. 14 is a schematic diagram of normal communication between a Master Radio and an AP1 at the current vehicle-mounted end according to an embodiment of the present invention;

fig. 15 is a schematic diagram of a vehicle-mounted terminal performing Master Radio and Slave Radio to switch roles according to an embodiment of the present invention.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

The invention is mainly based on micro inertial navigation autonomous positioning technology, utilizes an inertial measurement unit (comprising an accelerometer, a gyroscope and a magnetometer) of MEMS technology to measure the acceleration and the angular velocity of a train in a tunnel, and realizes the rapid switching of wireless communication of a subway vehicle-mounted motion unit to a ground base station in an auxiliary manner through integrating and resolving the velocity, the position and the course. Because the GPS signal is not acceptable within the tunnel, the vehicle location cannot be located by GPS. The invention adopts the inertial navigation sensor (such as a 9-axis inertial navigation sensor) to collect the speed, acceleration, position and other information of the tunnel vehicle-mounted motion unit, and comprehensively evaluates the communication quality of the vehicle-mounted unit by combining the beacon information of the base station, thereby carrying out the optimal time switching.

The tunnel vehicle-mounted motion unit assisted seamless roaming method based on inertial navigation in the embodiment of the invention, as shown in fig. 3, comprises the following steps:

S5, judging whether the difference between the RSSI values of the target AP with the largest RSSI value in the neighbor list and the currently connected AP is continuously in a preset interval for multiple times (for example, three times), if so, executing the step S6, otherwise, returning to the step S1;

s8, switching to the target AP.

Further, step S1 further includes performing a second-order low-pass filtering process on the real-time measured train dynamic data.

Further, in step S2, the direction cosine matrix algorithm is specifically adopted to perform gesture calculation, or the quaternion algorithm is adopted to perform gesture calculation.

Further, in step S3, the slope k is specifically calculated by the least square method.

Further, the neighbor list is based on a hash table, indexed as the MAC address of the currently connected AP.

Further, the vehicle-mounted wireless unit obtains the latest scanning result through active scanning, inserts the latest scanning result into the corresponding neighbor list, and performs aging treatment in a timing mode.

Specifically, an embodiment of the present invention solves the position information by a 9-axis sensor as follows:

The sensor group distribution is shown in fig. 4 and mainly comprises an accelerometer, a gyroscope and a magnetometer. The accelerometer is mainly used for collecting acceleration of train movement, the gyroscope is mainly used for collecting angular velocity of train movement, and the magnetometer is mainly used for collecting magnetic field of train movement. All the collected data can be subjected to pose calculation through a central processing unit, and the pose calculation mainly comprises calculation of position, speed and the like, and then the pose calculation is sent to vehicle-mounted wifi6 equipment (namely vehicle-mounted STA equipment) through a communication bus.

The sensor data is real-time data, the jitter is relatively large, and the FIR or IIR filter is a better choice for achieving better filtering effect.

For a first order low pass filter, there are:

cut-off frequency 30Hz, sampling frequency 500Hz, can be found a:

For a second order low pass filter, there are:

also, the cut-off frequency is 30Hz sampling frequency is 500Hz, and the coefficient can be obtained. Obtaining

The filtering effect of the measured XYZ three-axis accelerations can be seen by comparison: under the condition that the original data waveform fluctuates at the rest moment, the acceleration effect of the second-order low-pass filtering is much better than that of the first-order low-pass filtering, so that the test is passed, and therefore, the embodiment of the invention finally adopts the low-pass filter with the 2-order 30Hz to process the original data.

The sensor data with smaller noise is obtained by filtering the original data, the value of the train acceleration acquisition is larger in instantaneous response for the accelerometer and the gyroscope sensor, if the data are adopted for calculating the angle, the error is definitely larger, and the angle obtained by integrating the gyroscope is basically less influenced by the instantaneous change of the train acceleration, but the error brought for a long time is larger due to the problems of integral drift and temperature drift. In summary, gyroscopes have the characteristic of short-term reliability and long-term instability, so complementary filtering can be used to fuse them.

The gesture resolving mainly refers to that a central processing unit fuses collected data, and the real-time position of the train is resolved through a quaternion algorithm or a cosine matrix algorithm.

The attitude solution needs to solve the problem of the relative positions of the train and the earth. The geographic coordinate system is fixed, the coordinate system is composed of the X, Y and Z axes, the geographic coordinate system R is shown in fig. 5, and the fixed coordinate system of the train is shown as R, so that the Euler angle, the quaternion and the like can be used for describing the angular position relationship of R and R.

The inertial navigation module attitude calculation mainly comprises a directional cosine matrix algorithm and a quaternion algorithm, and the motion attitude of the train is analyzed in real time by any algorithm. The algorithm for solving these two poses is highlighted below.

(1) Updating a pose matrix using a directional cosine matrix algorithm

In the motion analysis of a train, it is necessary to analyze the motion gesture and the movement track. For convenience and accuracy of description, a space coordinate system is required to be introduced, two different three-dimensional space coordinates are defined, and one three-dimensional coordinate is a carrier coordinate and is used for describing movement posture information of a train; the other coordinate is the world reference coordinate, which is used to describe the running position information of the train.

As shown in figure 6A of the drawings,Representing the world reference frame, as shown in FIG. 6B,/>Representing the carrier coordinate system. The origin of the coordinates of the carrier corresponds to the geometric center of the train,/>The axial direction corresponds to the positive direction of travel of the train,/>Shaft and/>The axes are in the same horizontal plane, the directions are the same as those of the first embodimentThe axial direction is vertical,/>The axis is perpendicular to the geometric center of the trainShaft sum/>The plane of the axis is upward,/>Axis,/>Shaft and/>The axes form a right hand coordinate system. The carrier coordinate system moves along with the movement of the train, and the world coordinate system is always fixed. We assume that in the initial state the carrier coordinate system coincides with the world coordinate system. And in the train movement process, the carrier coordinate system translates relative to the world coordinate system, so that a new carrier coordinate system is continuously generated.

First, the position between the origin of the carrier coordinate system and the origin of the world coordinate system is marked as:

（0-1）

The pitch angle, roll angle and yaw angle of the train are respectively recorded as 、/>/>The coordinates of the rotation axis of the carrier coordinate system relative to the world coordinate system are:

（0-2）

from the above two formulas, the extended coordinates of the carrier coordinate system after translation and rotation relative to the world coordinate system can be defined:

（0-3）

the positional relationship between the transformed carrier coordinate system and the previous carrier coordinate system can be easily seen, but the rotational relationship needs to be represented by a rotation matrix. Let the initial carrier coordinate system be It is related to world coordinate systemThe world coordinate system is always a fixed coordinate system, and the carrier coordinate system is a dynamic coordinate system. Respectively rotating around three axes by a small angle to obtain a new carrier coordinate system/>, after three changes。/>Axis,/>Axis,/>The axes are three axes which are orthogonal in pairs, so that any spatial attitude of the train can be represented by the following/>The axis is the rotation axis,/>The axis is the rotation axis,/>The shaft is realized by three rotations of a rotary shaft.

If first byThe axis is the rotation axis, rotation/>Degree, i.e. yaw angle/>A degree; then by/>The shaft being a rotary shaft, rotatingDegree, i.e. pitch angle/>A degree; finally by/>The axis is the rotation axis, rotation/>Degree, i.e. pitch angle/>Degree. The rotation order of the carrier coordinate system is as follows:

According to the above steps, the coordinate system is first set To/>The axis is the rotation axis, rotation/>Degree, i.e. yaw angle/>Degree, as shown in fig. 7A. The rotation process may be represented by a rotation matrix as shown in equations (0-4).

（0-4）

Then the coordinate systemTo/>The axis is the rotation axis, rotation/>Degree, i.e. pitch angle/>Degree, as shown in fig. 7B. The rotation process may be represented by a rotation matrix as shown in equations (0-5).

（0-5）

Finally, the coordinate systemTo/>The axis is the rotation axis, rotation/>Degree, i.e. pitch angle/>Degree, as shown in fig. 7C. The rotation process may be represented by a rotation matrix as shown in equations (0-6).

（0-6）

The above process is according toThe axis is the rotation of the rotation axis/>Degree,/>The axis is the rotation of the rotation axis/>Degree,/>The axis is the rotation of the rotation axis/>And (3) the train obtains a new movement posture after three small-angle rotations in the sequence of the degrees. The transformation relation between the new carrier coordinate system and the old carrier coordinate system can be obtained by combining the formulas (0-4), (0-5) and (0-6):

（0-7）

When the rotation angle in each direction is kept unchanged, only the order of the selected rotation axes is changed, with the result that a different rotation matrix occurs. For example, we take the following rotation order with the above method, the result is as shown in the formula (0-8).

（0-8）

The results shown in formulas (0-8) are significantly different from those shown in formulas (0-7), and similarly, the results in several other orders can be calculated. It is clear from this that the rotation matrix of the coordinate system is related not only to the rotation angles in the respective directions, but also to the rotation axis selection order. So that in case the rotation angles in each direction are the same, the rotation axis selection order is different, six different rotation matrices are still obtained, and they are not equal.

However, the angular sampling rate of the train for each direction is high, so the rotation angle in each direction is small in each sampling. When the angle isIs sufficiently small, there is/>, in mathematics，/>This approximation relation.

Substituting this approximation into equations (0-7) respectively yields:

（0-9）

substituting this approximation into equations (0-8) respectively yields:

（0-10）

It can be seen from formulas (0-9) and (0-10) that in the results of the approximation calculation, the results of the two different rotation axis selection sequences are identical. Similarly, it is easy to prove that the results of other sequences are the same, and the similar remembers can be used for analyzing the posture of the train in engineering. The transformation process between the carrier coordinate system and the world coordinate system of the four-axis flight is known, and the principle of the gesture rotation of the train is known, so that the method is a basis for gesture calculation in software control and 3D effect display in an upper computer.

In summary, the following is written:

Then the matrix I.e. a cosine matrix.

(2) Updating a pose matrix using a quaternion algorithm

First, introduction of quaternion: the quaternion is an overcomplex number, and if the collection of quaternions is considered to be a multi-dimensional real space, the quaternion represents a four-dimensional space of k, i and j, and is a two-dimensional space relative to complex numbers. In short, the quaternion contains all information of the rigid body rotation, and in the attitude calculation of the train, a quaternion differential equation is often used to update the quaternion, and the form is as follows:

The quaternion represents a gesture matrix:

Updating quaternion, using first order longger-Kutta method (ringe-Kutta):

to reduce the computational effort, a dielectric approximation of the cosine matrix has been tried:

and then according to the small angle approximation, sin theta (radian) is approximately equal to theta (radian):

That is, the present invention attempts an algorithm design of three kinds of gesture solutions: the cosine matrix, the first order approximation of the cosine matrix, and the quaternion, the comparison effect of the three algorithms is shown in table 1 below:

Table 1 comparison of the effects of the three algorithms

The direction cosine and quaternion slow shake effect comparison results are shown in table 2 below:

TABLE 2 contrast of cosine and quaternion slow shaking effects

The direction cosine and quaternion quick shake effect comparison results are shown in table 3 below:

TABLE 3 contrast of cosine and quaternion fast shake effects

Although the directional cosine matrix first order approximation can also converge in a short time, it is not sufficient; the quaternion mode has quicker response, the direction cosine method is smoother, and the two differences in practical use are not great. The present invention preferably updates the pose by a directional cosine matrix algorithm.

The position information of the train can be easily obtained by updating the gesture. The most common neighbor relationships of the trackside base stations are shown in fig. 8A and 8B. The neighbor relation is stored in a neighbor list manner, and the storage manner is based on a hash table, and the index is the MAC address of the current AP, as shown in fig. 9.

As shown in fig. 10, in the active mode, when a scan command (network card scan command) is initiated, a probe frame is actively initiated to monitor surrounding aps, and if a fixed frequency scan is performed, the scan is typically completed within 5ms, which is normally shorter. Note that: and the overtime period is 10ms, and the active becon behaviors of the ap can be closed in the mode, so that the air interface collision is reduced.

In the case of full load, this operation is performed, and the air interface and the wired end appear as follows:

a) The empty bag grabbing performance: the scan behavior is certainly completed within 10ms at the longest according to 4 neighbors;

b) Wired end performance: from the current test results, the full bandwidth test of the iporf has no obvious condition of the pit drop interruption of the wired end flow.

The scan results are shown in fig. 11.

And (3) inserting the latest scanning result obtained after scan into a corresponding neighbor linked list, then carrying out aging treatment in a timing way, and analyzing the rssi value of each neighbor for a period of time to obtain a slope k (k is positive and negative and indicates to increase and decrease, and the absolute value of k reflects the change speed of the rssi value). Slope k calculation mode: the least squares method (Least Square Method, LSM) finds the optimal functional match of the data by minimizing the sum of squares of the errors (also called residuals). The calculation formula (please give the meaning of each letter) is as follows:

Wherein xi is the ith sampling times; yi: the corresponding i-time sampled rssi value; average value of n times; ; n is the sampling times; /(I) Calculated slope k.

With the location information and the rssi information of surrounding neighbors, roaming opportunities are described below. In a preferred embodiment of the present invention, the specific process of train roaming is shown in fig. 12, and specifically is:

1) Updating inertial navigation data to obtain information such as gesture, position, speed and the like;

2) Scanning to obtain the latest scanning result, and inserting the latest scanning result into a linked list corresponding to each neighbor according to the description of FIG. 12;

3) Analyzing statistical data according to the scanning result, and recording the slope k, variance and the travelling direction of the train of the signal value of each neighbor by linear regression;

4) Judging the difference between the rssi values of the best ap and the current link ap in the neighbor, judging whether the best switching position is reached, if so:

a) rssi differs by 3db, and the horse roams;

b) rssi is not 3db different, and the step 1) is continuously repeated;

5) If the optimal position is not reached: continuing to go down;

6) If the rsi difference is more than or equal to 6, or the difference lasts for 3 times between 3 and 6, continuing downwards, otherwise repeating the step 1);

7) Judging whether the slope k of the rssi of the currently connected ap is smaller than a certain negative threshold value, and if the slope k of the rssi of the target ap is larger than a certain positive threshold value, directly roaming, otherwise, exiting the step 1);

8) By repeating the above steps, the optimal switching time of roaming can be realized.

To prevent the repeated jump, a dead zone of 6db before and after can be set as a hysteresis process, as shown in fig. 13.

As shown in fig. 14: the current vehicle-mounted terminal Master Radio is normally communicated with the AP1, and the Slave Radio is used as a scanned Radio for detecting surrounding APs; when the optimal AP and the optimal switching time are acquired, roaming action is started to be executed; if the current target AP is AP2, the Slave Radio is configured according to the wireless distributed system rule without association and bridged with the AP 2; the Slave Radio and AP2 carry out relearning message, the purpose is that the Slave Radio sends ARP broadcast message of all source MAC addresses of the local wired port, so that the new bridge link knows MAC addresses of all terminal users, and an uplink wired channel is established rapidly; thereafter, the vehicle-mounted terminal performs Master Radio and Slave Radio to switch roles, as shown in fig. 15; by repeating the above steps, the roaming zero-packet-loss low-delay seamless switching can be realized.

The modules of the system are mainly used for implementing the steps of the method embodiment, and are not described in detail herein.

The present application also provides a computer readable storage medium such as a flash memory, a hard disk, a multimedia card, a card memory (e.g., SD or DX memory, etc.), a Random Access Memory (RAM), a Static Random Access Memory (SRAM), a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a programmable read-only memory (PROM), a magnetic memory, a magnetic disk, an optical disk, a server, an App application store, etc., on which a computer program is stored that when executed by a processor performs a corresponding function. The computer readable storage medium of the present embodiment, when executed by a processor, implements the tunnel vehicle-mounted motion unit assisted seamless roaming method based on inertial navigation of the method embodiment.

It should be noted that each step/component described in the present application may be split into more steps/components, or two or more steps/components or part of operations of the steps/components may be combined into new steps/components, according to the implementation needs, to achieve the object of the present application.

The sequence numbers of the steps in the above embodiments do not mean the execution sequence, and the execution sequence of the processes should be determined according to the functions and internal logic, and should not limit the implementation process of the embodiments of the present application.

It will be understood that modifications and variations will be apparent to those skilled in the art from the foregoing description, and it is intended that all such modifications and variations be included within the scope of the following claims.

Claims

1. The tunnel vehicle-mounted motion unit assisted seamless roaming method based on inertial navigation is characterized by comprising the following steps of:

s8, switching to the target AP.

2. The inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming method according to claim 1, wherein the step S1 further comprises performing a second-order low-pass filtering process on the real-time measured train dynamic data.

3. The inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming method according to claim 1, wherein in step S2, a direction cosine matrix algorithm is specifically adopted for gesture calculation.

4. The inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming method according to claim 1, wherein in step S2, a quaternion algorithm is specifically adopted for gesture calculation.

5. The inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming method according to claim 1, wherein the slope k in step S3 is specifically calculated by a least square method.

6. The inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming method according to claim 1, wherein the neighbor list is based on a hash table and is indexed as the MAC address of the currently connected AP.

7. The inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming method according to claim 1, wherein the vehicle-mounted wireless unit obtains the latest scanning result through active scanning, inserts the latest scanning result into a corresponding neighbor list, and performs aging treatment in a timing mode.

8. An inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming system, comprising:

the second judging module is used for judging whether the difference between the RSSI value of the target AP with the largest RSSI value in the neighbor list and the currently connected AP is in a preset interval three times continuously, if so, the third judging module is switched to execute, and if not, the data acquisition module is switched to execute;

The third judging module is used for judging whether the slope k of the currently connected AP is smaller than a certain negative threshold value or not, judging whether the slope k of the target AP is larger than a certain positive threshold value or not, if yes, executing the fourth judging module, and if not, executing the data acquisition module;

9. The inertial navigation-based tunnel vehicle-mounted motion unit assisted seamless roaming system of claim 8, further comprising a data processing module for performing a second order low pass filtering process on real-time measured train dynamic data.

10. A computer storage medium, in which a computer program executable by a processor is stored, the computer program performing the inertial navigation-based tunnel vehicle motion unit assisted seamless roaming method of any one of claims 1-7.