JP6510988B2 - Positioning system and positioning method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a positioning system and techniques of a positioning method.

A Global Navigation Satellite System (GNSS), such as a Global Positioning System (GPS), has become widespread in order to specify the position of its own device using a car navigation system or the like.
FIG. 10 shows each node that receives radio waves from GNSS satellites.
Each of the nodes A, B, and C specifies its own position based on the information received from the GNSS. When the clock time of the GNSS satellite and the time of the node are synchronized (coincident), the node may acquire three or more GNSS satellites. However, as in node Z, when three satellites can not be captured simultaneously due to an obstacle or irregular weather, or when GNSS radio waves such as indoors can not be received, the positional relationship between the node and the GNSS satellites is It can not be determined accurately.

  FIG. 11 identifies the position of node T from the arrival times (ToA: Time of Arrival) of radio waves received from three points A, B, C whose positions are known, such as three GNSS satellites and three base stations. The calculation method is shown. Based on the coordinates (X, Y, Z) of each of the three points, and the distance L between each base station to the node T calculated based on the arrival time of the radio wave received from each base station by the node T, The position (x, y, z) of the node T can be determined by solving the three simultaneous equations shown in 1).

Here, the accuracy of the position of the node T depends on the accuracy of the distance L, and the distance L is obtained from the arrival time of the radio wave. Therefore, as the difference between the clock time of the base station and the clock time of the node T is larger, the arrival time of the radio wave includes more errors, and the positional accuracy of the node T is also degraded.
Therefore, before communicating with the base station, the node T needs to be notified of the correct time from the server providing the correct time, and must synchronize (correct) its own clock time. As this time synchronization protocol, for example, PTP (Precision Time Protocol) described in Non-Patent Document 1 has been proposed.

IEEE (The Institute of Electrical and Electronics Engineers, Inc.), "IEEE Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems", IEEE Std 1588-2008 (Revision of IEEE Std 1588-2002)

  There are also nodes located in an area with irregular weather as shown in FIG. 10, and nodes located in an area where acquisition of GNSS satellites is difficult, such as high-rise buildings and underground malls. As shown in FIG. 11, if three GNSS satellites are not captured, simultaneous equations can not be solved, and the position of node T can not be identified. However, there is a need to position these nodes with high accuracy. In addition, even for an inexpensive terminal that does not have a GNSS antenna, there is a need to specify the position with high accuracy.

  Therefore, the present invention has as its main object to specify the position with high accuracy even under the situation where acquisition of GNSS satellites is difficult.

In order to solve the above-mentioned subject, position determination system of the present invention,
A plurality of master nodes whose own position is specified can communicate with a plurality of slave nodes whose own position is not specified,
Each of the slave nodes determines distance information with respect to each of the master nodes based on the transmission and reception time of the time synchronization packet exchanged with each of the master nodes, and the transmission / reception partner of the time synchronization packets Transition to the master node by specifying its own position information from the obtained distance information based on the position information of the master node, which is
In each of the time synchronization packets transmitted to each of the slave nodes, each of the master nodes notifies each of the slave nodes of its own clock time and its own position information .
Each of the slave nodes preferentially selects a node with a small degree n when selecting three of the master nodes for specifying its own position information among the plurality of communicable master nodes,
The order n of the master node means the order of the master node that has received radio waves directly from GNSS satellites as 1, and the master node that has newly transitioned by receiving the time synchronization packet from the nth master node It is characterized in that the order of n is n + 1 .

  As a result, by gradually propagating (propagating) the slave node to the master node, it is possible to specify the position widely even in an area where acquisition of GNSS satellites is difficult, such as high-rise buildings and underground malls.

  The present invention is characterized in that the time synchronization packet is a PTP (Precision Time Protocol) packet.

  In this way, positioning can be performed extensively using the PTP mechanism.

According to the present invention, a plurality of master nodes whose own position is specified can communicate with a plurality of slave nodes whose own position is not specified,
Each of the slave nodes obtains distance information with respect to each of the master nodes based on the transmission and reception time of the time synchronization packet exchanged with each of the master nodes, and the other party of transmission and reception of the time synchronization packets Transition to the master node by specifying its own position information from the obtained distance information based on the position information of the master node, which is
Each of the master nodes notifies each of the slave nodes of its own clock time and its own position information in the time synchronization packet transmitted to each of the slave nodes.
Each slave node calculates the deviation of its own clock time from the clock time of the master node based on the transmission and reception time of the time synchronization packet exchanged with the master node, and eliminates the deviation. Correct its own clock time to match the clock time of the master node ,
Before the elapse of a predetermined time after correcting its own clock time, correction of its own clock time is omitted, and a time synchronization packet exchanged between the slave node and the master node is regarded as a one-way packet. ,
After the elapse of a predetermined time after correcting the clock time of itself, correction of clock time of its own is permitted, and a packet for time synchronization exchanged between the slave node and the master node is used as a round trip packet. It is characterized by

As a result, by gradually propagating (propagating) the slave node to the master node, it is possible to specify the position widely even in an area where acquisition of GNSS satellites is difficult, such as high-rise buildings and underground malls.
And since the accurate clock time is provided from the master node without separately preparing a server for providing the correct time, the time and cost for preparing the time synchronization server can be reduced.
Furthermore, in a period in which the clock time difference between the master node and the slave node does not have to be taken into consideration, the internode distance can be simply obtained by only one-way packet communication without reciprocating the time synchronization packet. be able to.

In the present invention, the location system further includes a management device capable of communicating with the master node and the slave node, respectively.
The management apparatus receives notification of transmission and reception times of the time synchronization packet from the master node and the slave node, calculates the distance information between the master node and the slave node, and the position of the slave node. And calculating information in place of the slave node.

  As a result, each node does not have to execute calculation of distance information and position information by itself, so low-performance terminals such as portable terminals can also be used as nodes.

  According to the present invention, the slave node attempts transmission and reception of the time synchronization packet with the specific master node multiple times, and the slave node performs a specific operation based on an attempt with the shortest transmission / reception time among the results of the attempt. The distance information with respect to the master node is obtained.

  Thereby, even when the communication situation fluctuates due to noise of radio waves, etc., position information can be calculated with high accuracy.

In the present invention, the slave node is
In the process of selecting three of the master nodes in the set of communicable master nodes to form a node group, a plurality of the node groups are formed in different combinations of the master nodes belonging to the node group,
The position information of its own is determined from the overlapping range of the position information of its own obtained for each node group based on the position information of the master node belonging to each of the node groups,
The master node belonging to each node group determined according to a rule in which the individual reliability of the master node is evaluated to be higher as the distance information with the master node belonging to each node group is closer to the slave node of its own When the reliability of each node group is calculated based on the individual reliability of and the position information of its own is determined from the overlapping range, priority is given to the range of position information obtained from the node group having high reliability. It is characterized by

  Thus, slave nodes capable of communicating with four or more master nodes can determine their own position information with higher accuracy by effectively using the combination of the master nodes of the communication counterparts, and further, The calculation accuracy of the position information can be improved by determining the position information of the master node in favor of a master node close to.

  According to the present invention, even in a situation where acquisition of GNSS satellites is difficult, the position can be identified with high accuracy.

FIG. 1 (a) shows the stage in which nodes A to C, which have received radio waves directly from GNSS satellites, become base stations. FIG. 1B shows a stage in which nodes D and E which have received radio waves from nodes A to C of the base station become new base stations. FIG. 2A shows a stage in which the node F which has received radio waves from the nodes A, B and D of the base station becomes a new base station. FIG. 2 (b) shows the stage in which the node G which has received radio waves from the nodes B, D, F of the base station becomes a new base station. It is a block diagram of a position identification system concerning this embodiment. It is a block diagram which shows a form different from FIG. 3 of the position specifying system concerning this embodiment. It is a flowchart which shows the position identification process which paid its attention to the slave node concerning this embodiment. It is explanatory drawing which shows the detail of the calculation content of the time synchronization part concerning this embodiment, and a coordinate calculation part. FIG. 7A shows an example of obtaining the position range R1 of the slave. FIG. 7 (b) shows an example of obtaining the position range R2 of the slave. FIG. 8A shows an example of obtaining the position range R3 of the slave. FIG. 8 (b) shows an example of obtaining the position F of the slave. FIG. 9A shows that the position range R3 of FIG. 8A is narrowed down in three trials (R3a to R3c). FIG. 9B illustrates an example of referring to the reliability of the node group when specifying the position of the slave node F from the overlapping region Rz of the range R1 to R3 in FIG. 8B. Each node which receives an electromagnetic wave from the GNSS satellite concerning this embodiment is shown. A calculation method for specifying the position of the node T from the arrival times (ToA: Time of Arrival) of radio waves received from three GNSS satellites A, B, C according to the present embodiment will be shown.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 (a) shows the stage in which nodes A to C, which have received radio waves directly from GNSS satellites, become base stations.
First, two types of nodes are defined as follows for nodes that are computers having a communication function.
The nodes A, B and C are described by solid circles. These nodes have already been located and become base stations (reference points) for assisting in locating other nodes by notifying other nodes of their location information. It is a master node 1 (details are shown in FIG. 3).
Nodes D, E, F, G, and H are described by broken-line circles. These nodes are slave nodes 2 (details shown in FIG. 3) whose positions have not been identified yet, and whose positions are to be identified with the assistance of the master node 1.

  Nodes A, B, and C specify their positions by receiving radio waves directly from GNSS satellites (in other words, becoming primary nodes) using their GNSS antenna 23 (FIG. 3). If radio waves can be received from three or more GNSS satellites for one node, the three-dimensional position (x, y, z) of the node can be specified. On the other hand, the other nodes D, E, F, G, H do not have the GNSS antenna 23, or even if they have the GNSS antenna 23, the radio waves from the GNSS satellites are blocked, etc. The position of oneself is not specified at present.

FIG. 1B shows a stage in which nodes D and E which have received radio waves from nodes A to C of the base station become new base stations.
The node D specifies its own position by receiving radio waves from the nodes A to C of the base station. Similarly, the node E also specifies its own position by receiving radio waves from the nodes A to C of the base station. That is, nodes D and E become secondary nodes with respect to primary nodes A to C.

Here, two types of expressions indicating the position information of the node will be described.
"Global coordinates" indicate coordinates that can uniquely identify the position on the earth by satellites. For example, the global coordinates of Tokyo Tower are expressed as “longitude = 139 degrees 44 minutes 43.558 seconds, north latitude = 35 degrees 39 minutes 30.89 seconds”.
The “local coordinates” is a coordinate system arbitrarily set by the measurer, and indicates relative coordinates viewed from the origin. For example, the local coordinates of Tokyo Station are expressed as "1800 m east and 2500 m north" from the viewpoint of Tokyo Tower.

When the global coordinates of the origin A with respect to the local coordinates of the point B are known, the global coordinates of the point B can be obtained by the difference calculation from the global coordinates of the origin A.
For example, around 35 degrees north latitude, it is 25 m per second and 31 m per second, so “Longitude = 139 degrees 44 minutes 43.558 seconds, North latitude = 35 degrees 39 minutes 30.89 seconds” of Tokyo Tower, the difference “Longitude = By adding + about 82 seconds and north latitude = + about 74 seconds, the global coordinate of Tokyo Station “longitude = 139 degrees 45 minutes 57.902 seconds, north latitude = 35 degrees 40 minutes 52.975 seconds” can be obtained.

  In FIG. 1 (b), the global coordinates of the nodes A to C of the base station are known, so the local coordinates of the node D are obtained after the position of the node D is relatively determined as the local coordinates from the global coordinates. The global coordinates of the node D are obtained by coordinate conversion to global coordinates. Thus, the node D shifts from the slave node 2 to the master node 1 and operates as a base station in the same manner as the other nodes A to C. The node E also migrates to the master node 1 in the same manner.

  FIG. 2A shows a stage in which the node F which has received radio waves from the nodes A, B and D of the base station becomes a new base station. Since node F is located far from node C unlike node D, it is difficult to receive radio waves from node C. Therefore, it is possible to shift from slave node 2 to master node 1 with assistance from a total of three nodes of secondary nodes D located near node F in addition to primary nodes A and B. That is, node F transitions to a tertiary node.

FIG. 2 (b) shows the stage in which the node G which has received radio waves from the nodes B, D, F of the base station becomes a new base station. Similarly to the node F, the node G does not distinguish between the primary node and the secondary node, and by receiving assistance from the nodes B, D, and F, which are base stations near the node G, the slave node 2 From the master node 1 to the master node 1.
If the distances from the node G are substantially the same, it is desirable that the degree n of the n-th node be assisted by a node with a small number. An error in coordinate conversion of local coordinates to global coordinates is accumulated as the degree n increases.
As described above, by performing propagation from slave nodes 2 to master node 1 in propagation from primary nodes A to C, the range of position specification is expanded even for nodes that can not receive radio waves from GNSS satellites. can do. That is, the primary node, the secondary node,..., (N-1) next node is the master node 1, and the slave node 2 of the n-th node is the master node 1.

FIG. 3 is a block diagram of a position identification system.
As described in FIG. 1 and FIG. 2, the position identification system is configured such that each node can communicate with other nearby nodes in a wired or wireless manner, and the master node 1 whose position is known, or itself The slave node 2 is classified into one of the slave nodes 2 whose positions are unknown. It should be noted that even if the same node is the slave node 2 at a predetermined time, it may be transitioned (promoted) to the master node 1 with the assistance of another master node 1.

Each of the master node 1 and the slave node 2 is configured as a computer having a central processing unit (CPU), a memory, a storage unit (storage unit) such as a hard disk, and a network interface.
The computer operates a control unit (control means) configured of respective processing units described later by the CPU executing a program (also referred to as an application or an abbreviation of the application) read into the memory.

The master node 1 includes a communication interface 10a, a transmitter 11a, a receiver 12a, a time synchronization unit 21a, a coordinate calculation unit 22a, and a storage unit 30a. Furthermore, in the case of a primary node, the GNSS antenna 23 is also included. doing. The storage unit 30a stores its own clock time 31a, its own local coordinates 32a, and its own global coordinates 33a.
The slave node 2 basically has the same configuration as the master node 1 but does not have the GNSS antenna 23. In order to distinguish whether it is a component of the master node 1 or a component of the slave node 2 even for the same component, the code end of the component of the master node 1 is "a" and the code end of the component of the slave node 2 is Let's say "b".

The communication interface 10a is connected to the transmitter 11a and the receiver 12a, and the communication interface 10b is connected to the transmitter 11b and the receiver 12b. The packet from transmitter 11a arrives at receiver 12b and the packet from transmitter 11b arrives at receiver 12a.
The communication standard between the communication interfaces 10a and 10b is arbitrary, and may be wired communication or wireless communication. Furthermore, unicast communication between one master node 1 and one slave node 2 may be used, or multicast transmission may be performed from one master node 1 to N slave nodes 2, or M Multicast transmission may be performed from one slave node 2 to the master node 1 of

  The time synchronizer 21a of the master node 1 corrects (synchronizes) the clock time 31b of the slave node 2 by notifying the time synchronizer 21b of the time stamp information of the clock time 31a. For this time synchronization process, for example, a time synchronization protocol such as PTP is used (see FIG. 6 for details). Furthermore, the time synchronization units 21a and 21b use the time stamp information of the clock times 31a and 31b used for the time synchronization process also for estimating the distance between the master node 1 and the slave node 2.

The coordinate calculation unit 22b calculates the coordinates of its own slave node 2 based on the local coordinates 32a and the global coordinates 33a notified from the master node 1 and the time stamp information acquired by the time synchronization unit 21b. Therefore, the coordinate calculation unit 22b first calculates the local coordinates 32b of the slave node 2, and then calculates the difference between the local coordinates 32b with the global coordinates 33a as the origin as described in the example of the Tokyo Tower. Calculate global coordinates 33b of node 2. The coordinate conversion calculation from the local coordinates 32b to the global coordinates 33b may be realized by any known calculation method such as using a coordinate conversion rule by matrix calculation or the like.
Thereby, the local coordinates 32b and the global coordinates 33b are associated with each other and stored in the storage unit 30b. Since the slave node 2 behaves as the master node 1 thereafter, processing for specifying the position of the other slave node 2 is performed for the other slave node 2 based on the local coordinates 32a and the global coordinates 33a in the storage unit 30a. To help.

FIG. 4 is a block diagram showing another form of the position specifying system from FIG.
The management device 3 is a part of the functions of the master node 1 and the slave node 2 shown in FIG.
The coordinate calculation unit 22z substitutes the coordinate calculation units 22a and 22b to obtain local coordinates 32a and 32b and global coordinates 33a and 33b of each node. Therefore, the coordinate calculation request units 22x and 22y of each node notify the coordinate calculation unit 22z of the time stamp information acquired by the time synchronization units 21a and 21b of their own, and request the management device 3 to calculate the coordinates of each node. .
The coordinate calculation unit 22z receives the request, and based on the notified time stamp information, the local coordinates 32a of each node stored by itself, and the global coordinates 33a of each node stored by itself, the master node 1- The distance between the slave nodes 2 and the local coordinates 32b and the global coordinates 33b of the slave node 2 are obtained.
The coordinate calculation unit 22z stores global coordinates 33a and 33b as global coordinates 33z in its own storage unit, and stores local coordinates 32a and 32b as local coordinates 32z in its own storage unit, so that the position of another node thereafter Use for identification.

As a result, the management device 3 can centrally manage the distributed position information of each node, so that, for example, the position of each node is superimposed on the map and the administrator is made aware of the distribution of the nodes, etc. , Can centrally manage location information. Furthermore, since each node does not need to calculate coordinates, a low-performance mobile terminal can be used as a node.
Alternatively, each node of the location specification system of FIG. 3 may perform unified management of location information by the management apparatus 3 by notifying the management apparatus 3 of its own location information calculated by each node.

FIG. 5 is a flow chart showing position identification processing focusing on slave nodes.
S11 to S14 are loops for selecting one master node 1 capable of communicating with the slave node 2 one by one in order.
As S12, the time synchronization unit 21b performs clock synchronization by transmitting and receiving a time synchronization packet such as PTP with the time synchronization unit 21a of the master node 1 selected in the loop. That is, the clock time 31 b of the slave node 2 is set to the clock time 31 a of the master node 1. In this time synchronization process, the time synchronization unit 21b acquires the following four pieces of time stamp information from the time synchronization packet.
(Time t1) Transmission time of packet to be transmitted from master node 1 to slave node 2 (time on master node 1 side)
(Time t2) Reception time of packet transmitted from master node 1 to slave node 2 (time on slave node 2)
(Time t3) Transmission time of packet to be transmitted from slave node 2 to master node 1 (time on slave node 2)
(Time t4) Reception time of packet transmitted from slave node 2 to master node 1 (time on master node 1)
Also, the slave node 2 can obtain the position information of each master node 1 from the global coordinates 33 a included in the time synchronization packet transmitted by each master node 1.

  The time synchronization process of S12 may be repeatedly performed (trial) on the same master node 1-slave node 2 (see FIG. 9A). Even if the transmitting and receiving nodes are the same, the arrival time (delay time) of each packet may be fluctuated by noise of the radio wave or the like in multiple time synchronization processing. Therefore, among the arrival times of packets measured repeatedly, it is possible to adopt a minimum delay time that is least affected by noise.

Further, since the time synchronization process of S12 is in the loop of S11 to S14, the time synchronization process of S12 is repeatedly performed in a short time. On the other hand, when the clock function in the slave node 2 is high-performance, once the time is updated, the accurate time can be maintained for a while. Therefore, updating of the time may be omitted as a period in which the correct time can be maintained after the time is updated.
When time update is omitted, if there is time information (a combination of t1 and t2 or a combination of t3 and t4) of one way among the times t1 to t4, the master node 1-slave node 2 The arrival time (delay time) of the packet can be determined by a simple expression "reception time-transmission time". That is, the measurement packet for clock synchronization can be shortened from the round trip packet to the one way packet.

  As S13, the coordinate calculation unit 22b measures the distance from its own slave node 2 to the master node 1 from the time stamp information of time t1 to t4 (details are shown in FIG. 6). Thus, the slave node 2 can obtain the distance to each master node 1 capable of communicating with itself, and this distance information is used for position identification processing of the slave node 2 as described in S21 to S24 described later. .

  S21 to S24 are loops for selecting three master nodes 1 for each combination of node groups extracted from the set of master nodes 1 selected in S11 to S14. For example, there are ten combinations of <A, B, C>, <A, B, D>, etc. for selecting three nodes from five nodes (A, B, C, D, E). , S21 to S24 are executed ten times.

  As S22, the coordinate calculation unit 22b calculates the position range of the slave from the distances to the respective nodes belonging to the node group (the distances obtained in S13) (for details, FIGS. 7 to 9). Here, since a slight error may be included in the time stamp information of time t1 to t4 and the global coordinates 33a of the master node 1, the position of the slave is not point coordinates, and the slave may exist. It becomes a position range.

As S23, the coordinate calculation unit 22b calculates the reliability of the node group selected in the current loop. Therefore, first, the individual reliability of each of the three master nodes 1 belonging to the node group is obtained. Basically, the individual reliability is calculated to be higher as the distance to the master node 1 determined in S13 is closer to its own slave node 2. The following is an example of correspondence between the distance and the individual reliability.
Individual reliability = 3 if 0 m ≦ distance <100 m
Individual reliability = 2 if 100 m ≦ distance <500 m
Individual reliability = 1 if 500 m ≦ distance
Next, the individual reliabilities are integrated to calculate the group reliability. For example, there is an example in which the total score of the individual reliabilities is a group reliability.

As S31, the coordinate calculation unit 22b specifies the local coordinates 32b of the slave position from the overlapping area of the position range of the slave in each node group obtained in S22. Alternatively, instead of using overlapping areas of the position ranges of all slaves, the slave positions may be narrowed down from areas where the position ranges of more (majority) slaves overlap. Here, the coordinate calculation unit 22b may narrow down the slave position from the overlapping area of the position range of the slave with reference to the group reliability obtained in S23 (see FIG. 9B).
As described above, by combining a plurality of node groups to narrow down the slave position, the accuracy of the slave position is improved.

  As S32, the coordinate calculation unit 22b performs coordinate conversion of the local coordinates 32b of the identified slave position to the global position (global coordinates 33b). The local coordinates 32b of S31 and the global coordinates 33b of S32 are stored in the storage unit 30b as position information of the slave node 2 itself.

FIG. 6 is an explanatory diagram showing details of calculation contents of the time synchronization unit 21b and the coordinate calculation unit 22b.
The node T which is the slave node 2 synchronizes time with each of the nodes A, B and C which is the master node 1 by the PTP protocol. The details of PTP are described in Non-Patent Document 1.
The slave node 2 obtains four pieces of time stamp information (time t1 to t4) by reciprocating the PTP time synchronization packet between the master node 1 and the slave node 2 as described in S12. Based on the time stamp information, the time synchronization unit 21b obtains the accurate clock time 31b and the distance between the master node 1 according to the equation (2) in FIG.

Hereinafter, exemplified packet P _AT sent to the node A → node T, in the case of packet P _TA sent to the node T → node A.
First, the transmission time t1 at the node A side for the packet P _AT, the reception time t2 at node T side of the packet is the next relationship.
(Time t1) + (delay time taken for transmission) + (offset which is a shift of time on the slave node 2 side) = (time t2)
Similarly, the transmission time t3 at node T side for the packet P _TA, the reception time t4 at the node A side of the packet is the next relationship.
(Time t3) + (Delay time taken for transmission)-(Offset that is a shift of time on the slave node 2 side) = (Time t4)
Therefore, as the first line of equation (2), determined the delay time [Delta] T _A taken to transmit an offset beta _A is the deviation of the time (S12). Here, T _AT is the time difference between the packet _{P AT (t2-t1),} T TA is the time difference between the packet P _TA (t4-t3). The slave node 2 may correct its own clock time so as to eliminate the offset β _A and match the clock time of the master node 1 (S12).

Further, the propagation velocity (speed of light) c, by using the refractive index n of the medium, the node A, the distance L _A between T can also be determined (S13). Also, δ _A is a measurement error such as a time synchronization error, and α is a measurement error of the receiver (slave node 2).
And the 3rd-5th lines of Formula (2) are simultaneous equations expanded when the right side of Formula (1) of FIG. 11 contains an error. By obtaining these simultaneous equations, the position (x, y, z) of the node T is obtained as the local coordinates 32 b (S 22).

Therefore, if the measurement error α (for example, the measurement error unique to the device) of the receiver (slave node 2) is known, the slave node 2 sets the offset β _A to the equation (2) in FIG. 6 each time PTP is performed. substituted and may be asked to distance L _a high precision.
When performing time synchronization and delay (distance) measurement simultaneously in one PTP execution,
Time synchronization processing: The offset β _A which is a time shift is corrected.
Delay measurement processing: The measurement error is corrected (the offset β _A is added or subtracted) to the time stamp information (time t1 to t4) to obtain a more accurate delay time.
By performing the two processes in parallel, as compared with the case where the delay measurement is performed after the predetermined period has elapsed from the time synchronization process, there is no concern about the time shift, and a more accurate measurement can be performed.

The details of the processing (S21 to S24) for each node group will be described below with reference to FIGS. 7 and 8.
First, it is assumed that the first node group “B, C, E” is selected in the first loop. The coordinate calculation unit 22b solves the position of the slave by solving the simultaneous equations described in FIG. 6 based on the distance information from each node in addition to the global coordinates 33a of each node B, C, E belonging to the group. The range R1 is obtained (FIG. 7 (a)).
Next, when the second node group “A, C, E” is selected in the second loop, the position range R2 of the slave is also determined in the same manner as the first node group (FIG. 7 (b)). Here, since the position ranges R1 and R2 of the slaves include some errors, both ranges do not completely match and partially overlap.

Furthermore, when the third node group "A, B, D" is selected in the third loop, the position range R3 of the slave is also determined in the same manner as the first and second node groups (FIG. 8A).
Since the overlapping range of the position ranges R1 to R3 of these slaves has narrowed somewhat, as shown in S31, the overlapping region of each of the position ranges R1 to R3 is specified as the position of the slave node F (FIG. 8 (b)) ).

FIG. 9A shows that the position range R3 of FIG. 8A is narrowed down in three trials (R3a to R3c). As described in S12, time synchronization processing of PTP may be repeatedly performed between the same master node 1-slave node 2.
Here, from the slave position range R3a calculated based on the result of the first time synchronization processing (for example, the distance from the node B), the slave's calculated based on the result of the second time synchronization processing The position range R3b is narrow. Therefore, since the second time synchronization processing is measured to have a shorter distance (higher accuracy), the range R3b is narrower than the range R3a and the distance from the node B is shorter.
Similarly, the third range R3c is more accurate than the second range R3b, so the range R3c is adopted as the position range R3 of the third node group "A, B, D".

FIG. 9B illustrates an example of referring to the reliability of the node group when specifying the position of the slave node F from the overlapping region Rz of the range R1 to R3 in FIG. 8B.
As shown in S31, the group reliability of each node group calculated in S23 can be used to narrow down the point position of the slave node F in the overlapping area Rz.
For example, the point position F1 before reflecting the group reliability is the center of gravity of the overlapping area Rz. On the other hand, the point position F2 after reflecting the group reliability is corrected so as to be closer to the center C3 of the region R3 or the center C1 of the region R1 than the point position F1. This correction process is performed because the reliability of the region R3 = 8 and the reliability of the region R1 = 6 are larger (more reliable) than the reliability of the region R2 = 4. That is, the method shown in FIG. 9B is a method of determining the point position of the slave node F so as to be closer to the region as the reliability is higher.

  In the present embodiment described above, even in the case of node Z in FIG. 10 where GNSS satellites can not be directly captured due to obstacles or irregular weather, information on inter-node distances obtained by time synchronization calculation with surrounding master node 1 The position of the slave node 2 itself can be identified with high accuracy using Furthermore, as described in FIG. 1 and FIG. 2, the slave node 2 of the n-th node (n> 1) is gradually transferred (propagated) to the master node 1, whereby high-rise buildings, underground malls, etc. Even in areas where GNSS satellite acquisition is difficult, localization can be performed over a wide range.

  In addition, even in the case of an inexpensive terminal not equipped with the GNSS antenna 23 as in the slave node 2 of FIG. 3, it is possible to specify its own position with high accuracy. Furthermore, by the configuration in which the management device 3 of FIG. 4 substitutes the position calculation of the master node 1 and the slave node 2, it is possible to utilize a low-performance node terminal for position specification.

1 Master node 2 Slave node 3 Management device 10a, 10b Communication interface 11a, 11b Transmitter 12a, 12b Receiver 21a, 21b Time synchronizer 22a, 22b, 22z Coordinate calculation unit 22x Coordinate calculation request unit 22z Coordinate calculation unit 23 GNSS antenna 30a, 30b storage unit 31a, 31b clock time 32a, 32b, 32z local coordinates 33a, 33b, 33z global coordinates

Claims (8)

A plurality of master nodes whose own position is specified can communicate with a plurality of slave nodes whose own position is not specified,
Each of the slave nodes obtains distance information with respect to each of the master nodes based on the transmission and reception time of the time synchronization packet exchanged with each of the master nodes, and the other party of transmission and reception of the time synchronization packets Transition to the master node by specifying its own position information from the obtained distance information based on the position information of the master node, which is
Each of the master nodes notifies each of the slave nodes of its own clock time and its own position information in the time synchronization packet transmitted to each of the slave nodes .
Each of the slave nodes preferentially selects a node with a small degree n when selecting three of the master nodes for specifying its own position information among the plurality of communicable master nodes,
The order n of the master node means the order of the master node that has received radio waves directly from GNSS satellites as 1, and the master node that has newly transitioned by receiving the time synchronization packet from the nth master node A positioning system characterized in that the order of n is n + 1 . A plurality of master nodes whose own position is specified can communicate with a plurality of slave nodes whose own position is not specified,
Each of the slave nodes obtains distance information with respect to each of the master nodes based on the transmission and reception time of the time synchronization packet exchanged with each of the master nodes, and the other party of transmission and reception of the time synchronization packets Transition to the master node by specifying its own position information from the obtained distance information based on the position information of the master node, which is
Each of the master nodes notifies each of the slave nodes of its own clock time and its own position information in the time synchronization packet transmitted to each of the slave nodes .
Each slave node calculates the deviation of its own clock time from the clock time of the master node based on the transmission and reception time of the time synchronization packet exchanged with the master node, and eliminates the deviation. Correct its own clock time to match the clock time of the master node,
Before the elapse of a predetermined time after correcting its own clock time, correction of its own clock time is omitted, and a time synchronization packet exchanged between the slave node and the master node is regarded as a one-way packet. ,
After the elapse of a predetermined time after correcting the clock time of itself, correction of clock time of its own is permitted, and a packet for time synchronization exchanged between the slave node and the master node is used as a round trip packet. A positioning system characterized in that . The position identifying system according to claim 1 or 2 , wherein the time synchronization packet is a packet of PTP (Precision Time Protocol). The location system further includes a management device capable of communicating with the master node and the slave node, respectively.
The management apparatus receives notification of transmission and reception times of the time synchronization packet from the master node and the slave node, calculates the distance information between the master node and the slave node, and the position of the slave node. The location system according to any one of claims 1 to 3, wherein calculation of information is performed instead of the slave node. The slave node attempts transmission and reception of the time synchronization packet with the specific master node multiple times, and based on an attempt with the shortest transmission and reception time among the results of the attempts, the slave node and the specific master node The position determination system according to any one of claims 1 to 4, wherein the distance information between the two is determined. The slave node is
In the process of selecting three of the master nodes in the set of communicable master nodes to form a node group, a plurality of the node groups are formed in different combinations of the master nodes belonging to the node group,
The position information of its own is determined from the overlapping range of the position information of its own obtained for each node group based on the position information of the master node belonging to each of the node groups,
The master node belonging to each node group determined according to a rule in which the individual reliability of the master node is evaluated to be higher as the distance information with the master node belonging to each node group is closer to the slave node of its own When the reliability of each node group is calculated based on the individual reliability of and the position information of its own is determined from the overlapping range, priority is given to the range of position information obtained from the node group having high reliability. The positioning system according to any one of claims 1 to 5, wherein: It is executed by a positioning system in which a plurality of master nodes whose own position is specified and a plurality of slave nodes whose own position is not specified are configured to be communicable,
Each of the slave nodes obtains distance information with respect to each of the master nodes based on the transmission and reception time of the time synchronization packet exchanged with each of the master nodes, and the other party of transmission and reception of the time synchronization packets Transition to the master node by specifying its own position information from the obtained distance information based on the position information of the master node, which is
In each of the time synchronization packets transmitted to each of the slave nodes, each of the master nodes notifies each of the slave nodes of its own clock time and its own position information .
Each of the slave nodes preferentially selects a node with a small degree n when selecting three of the master nodes for specifying its own position information among the plurality of communicable master nodes,
The order n of the master node means the order of the master node that has received radio waves directly from GNSS satellites as 1, and the master node that has newly transitioned by receiving the time synchronization packet from the nth master node A position specifying method characterized in that the order of n is n + 1 . It is executed by a positioning system in which a plurality of master nodes whose own position is specified and a plurality of slave nodes whose own position is not specified are configured to be communicable,
Each of the slave nodes obtains distance information with respect to each of the master nodes based on the transmission and reception time of the time synchronization packet exchanged with each of the master nodes, and the other party of transmission and reception of the time synchronization packets Transition to the master node by specifying its own position information from the obtained distance information based on the position information of the master node, which is
In each of the time synchronization packets transmitted to each of the slave nodes, each of the master nodes notifies each of the slave nodes of its own clock time and its own position information .
Each slave node calculates the deviation of its own clock time from the clock time of the master node based on the transmission and reception time of the time synchronization packet exchanged with the master node, and eliminates the deviation. Correct its own clock time to match the clock time of the master node,
Before the elapse of a predetermined time after correcting its own clock time, correction of its own clock time is omitted, and a time synchronization packet exchanged between the slave node and the master node is regarded as a one-way packet. ,
After the elapse of a predetermined time after correcting the clock time of itself, correction of clock time of its own is permitted, and a packet for time synchronization exchanged between the slave node and the master node is used as a round trip packet. A method of locating characterized by:

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