JP6862738B2 - Positioning device - Google Patents

Description

The present invention relates to a positioning device.

GPS (Global Positioning System) calculates the position of a receiving point using distance measurement signals from multiple GPS satellites, and this system is widely used in navigation devices for moving objects such as vehicles. There is. In GPS, in general, the latitude, longitude and height of a receiver can be calculated by using four or more GPS satellites for positioning.

The positioning position based on the ranging signal includes an error with respect to the actual position. Factors that cause errors in the positioning position include, for example, factors on the GPS satellite side such as satellite orbit deviation and satellite clock deviation, factors on the propagation path such as ionospheric delay, and receiver side such as receiver noise and multipath. Factors and the like.

An error circle is a circle that represents the approximate distance that the GPS positioning position may include with respect to the actual position. In other words, a state in which the radius of the error circle is small represents a state in which the positioning accuracy is high, and a state in which the radius of the error circle is large represents a state in which the positioning accuracy is low. Such an error circle is used, for example, in a map matching technique for matching a positioning position with a road position in an in-vehicle navigation device.

Various proposals have been made to reduce the error circle radius. For example, in Patent Document 1, it is calculated based on the accuracy information (User Range Accuracy: URA) transmitted from GPS satellites and the arrangement of GPS satellites. It is disclosed that the error circle radius is calculated based on the Position Dilution of Precision (PDOP) and (Horizontal DOP: HDOP).

Japanese Unexamined Patent Publication No. 6-148307

By the way, when the GPS antenna is arranged outside the vehicle, it is generally arranged near the windshield in the cabin of the vehicle because it is necessary to take measures to prevent damage and route the cable to the positioning device.

However, if the GPS antenna is arranged in the cabin of the vehicle, the ranging signal arriving from a predetermined direction may be shielded by the top plate of the cabin depending on the shape of the cabin of the vehicle.

1A and 1B are diagrams schematically showing the problem. FIG. 1A shows the arrangement position of the GPS antenna (L2 in the figure) in a passenger car, and FIG. 1B shows the arrangement position of the GPS antenna (L1 in the figure) in a large vehicle such as a truck.

As can be understood by comparing FIGS. 1A and 1B, in the case of a cabin shape with an inclined windshield as shown in FIG. 1A, the GPS antenna is measured from each direction without being shielded by the top plate of the cabin. The distance signal can be received. However, in the case of a cabin with an upright windshield as shown in FIG. 1B, the distance measurement signal coming from the rear side of the vehicle is shielded by the top plate of the cabin, so that the GPS antenna can use the distance measurement signal from that direction. Will not be received.

In this way, if the distance measurement signal from one side is shielded by the top plate of the cabin and cannot be received, for example, the positioning result may be biased and the error circle may be expanded.

The present invention has been made in view of the above problems, and it is necessary to set a highly accurate error circle even when the distance measurement signal arriving from the rear side of the vehicle is blocked by the top plate of the cabin and cannot be received. An object of the present invention is to provide a positioning device capable of providing a positioning device.

The main invention for solving the above-mentioned problems is a positioning device that receives distance measurement signals transmitted from a plurality of GPS satellites via GPS antennas arranged in the cabin of a vehicle, and the distance measurement signals. The positioning unit that calculates the positioning point indicating the position of the vehicle and the center point of the error circle based on the plurality of the positioning points calculated by the positioning unit are set based on the above, and the distance measurement signal is received. It is a positioning device including an error circle setting unit for setting the radius of the error circle with reference to the positioning point calculated at a position deviated to the direction side.

According to the positioning device according to the present invention, it is possible to set a highly accurate error circle even when the distance measuring signal arriving from the rear side of the vehicle is shielded by the top plate of the cabin and cannot be received.

The figure which shows an example of the arrangement position of the GPS antenna in a passenger car The figure which shows an example of the arrangement position of the GPS antenna in a large vehicle The figure which shows an example of the structure of the GPS receiver which concerns on 1st Embodiment A flowchart showing the operation of the positioning device according to the first embodiment. The figure explaining the calculation method of the error circle which concerns on a comparative example. The figure explaining the calculation method of the error circle which concerns on 1st Embodiment The figure which shows an example of the arrangement state of the GPS antenna which concerns on 2nd Embodiment

(First Embodiment)
Hereinafter, an example of the configuration of the GPS receiver 1 according to the present embodiment will be described with reference to FIG. The GPS receiver 1 according to the present embodiment is mounted on a large vehicle, for example, as described above with reference to FIG. 1B, and the GPS antenna 10 is arranged at the position of the windshield in the cabin of the vehicle. It is assumed that it has become.

FIG. 2 is a diagram showing an example of the configuration of the GPS receiver 1 according to the present embodiment.

The GPS receiver 1 according to the present embodiment includes a GPS antenna 10, a receiving unit 20, and a positioning device 30.

The GPS antenna 10 receives the ranging signals transmitted from each of the plurality of GPS satellites and sends them to the receiving unit 20. As the GPS antenna 10, any type of GPS antenna 10 can be used, and for example, a patch antenna is used.

The ranging signal transmitted from each GPS satellite spreads the spectrum of a carrier wave consisting of a predetermined frequency (for example, 1575.42 MHz in the case of GPS L1 wave) by a PN code set for each GPS satellite. , It is a radio wave phase-modulated by a navigation message.

The ranging signal includes the PN code of the GPS satellite, the orbit information of the GPS satellite, the position of the GPS satellite, the time information at which the ranging signal was transmitted, the correction data of the satellite clock, the ionospheric correction data, and the like.

The receiving unit 20 includes an RF unit, an AD conversion unit, and a demodulation unit. The RF unit mixes the ranging signal output from the GPS antenna 10 and the signal generated by the local oscillator, and converts the frequency of the ranging signal into an intermediate frequency. The AD conversion unit converts the ranging signal acquired from the RF unit from an analog signal to a digital signal. The demodulation unit performs autocorrelation processing on the ranging signal acquired from the AD conversion unit based on the PN code, and demodulates the data. The receiving unit 20 outputs the distance measuring signal demodulated in this way to the positioning device 30.

The positioning device 30 positions the vehicle based on the ranging signal and calculates an error circle of the positioning result. The positioning device 30 includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an input port, an output port, and the like.

The positioning device 30 includes a positioning unit 31, an error circle setting unit 32, and a map matching unit 33.

The positioning unit 31, the error circle setting unit 32, and the map matching unit 33 are realized, for example, by the CPU referring to a control program or various data stored in a ROM, RAM, or the like. However, it goes without saying that the function is not limited to processing by software, but can also be realized by a dedicated hardware circuit.

The positioning unit 31 positions the vehicle based on the ranging signals transmitted from each of the plurality of GPS satellites. In the following, the positioning position calculated by the positioning unit 31 will be referred to as a “positioning point”, and will be described separately from the “vehicle position” determined by the map matching unit 33, which will be described later.

The error circle setting unit 32 sets the error circle based on a plurality of positioning points calculated within a predetermined time (for example, for several seconds). The plurality of positioning points represent the distribution of positioning points including an error when the vehicle exists at a certain point. However, when setting the error circle, the error circle setting unit 32 receives the distance measurement signal from the GPS antenna 10 in consideration of the distance measurement signal coming from the rear side of the vehicle being shielded by the top plate of the vehicle. An error circle with a radius relative to the direction is set (described later with reference to FIG. 4B).

The map matching unit 33 determines the most probable position as the vehicle position based on the error circle set in the error circle setting unit 32 and the map data. In the storage unit such as the RAM of the positioning device 30, road information is stored as map data in association with position information such as latitude and longitude.

[Operation of positioning device]
Next, with reference to FIGS. 3 to 4, an example of the operation of the positioning device 30 according to the present embodiment will be shown.

FIG. 3 is a flowchart showing the operation of the positioning device 30. The flowchart shown in FIG. 3 is, for example, executed by the positioning device 30 according to a computer program. This operation flow is repeatedly executed by the positioning device 30, for example, when the vehicle is traveling.

First, the positioning unit 31 of the positioning device 30 calculates a positioning point based on the ranging signals received from a plurality of GPS satellites (step S1).

The positioning unit 31 calculates, for example, a pseudo distance between each GPS satellite and the GPS antenna 10 (representing the distance obtained by multiplying the time difference between the GPS satellite transmitting the distance measurement signal and receiving it by the GPS antenna 10 by the light speed). As a reference, the positioning point is calculated by the principle of triangulation.

For example, the positioning unit 31 obtains the following equation (1) for each GPS satellite, and calculates the positioning point based on the simultaneous equations.
(T _{u − Δ t u} ) − (t _{svi − Δ t svi} )
= {(X _u − x _svi ) ² + (y _{u −} y _svi ) ² + (z _{u −} z _svi ) ² } ^1/2 / C… Equation (1)
However, _{t u:} time of the positioning _device, t svi: GPS satellite time, Delta] t _u: error of _{t u, Δt svi:} error of _{t svi, (x u, y} u, z u): positioning _{point, (x svi} , Y _svi , z _svi ): GPS satellite position, C: light speed

In the above formula (1), _t u _-t svi showing the pseudorange error Delta] t _svi the GPS satellite time _{t svi,} GPS satellite position _{(x svi, y svi, z} svi) is measured is transmitted from each GPS satellite It becomes known by the distance signal. On the other hand, the error Delta] t _u times _{t u} of the positioning device 30, four variable positioning point _{(x u, y u, z} u) has a unknowns. Therefore, the positioning unit 31 can calculate one positioning point by, for example, solving simultaneous equations of four GPS satellites.

Here, the ranging signals are continuously transmitted from each GPS satellite, and in addition, the ranging signals are transmitted from about 10 GPS satellites to the GPS antenna 10. Therefore, the positioning unit 31 can calculate a plurality of positioning points in a short time.

From the viewpoint of converging the distribution of positioning points, the positioning unit 31 may be configured not to use the ranging signal whose signal strength is equal to or less than the threshold value for calculating the positioning points in the calculation. There are various known methods for calculating the positioning point, and any of the methods may be used.

Next, the error circle setting unit 32 sets the error circle based on the plurality of positioning points (steps S2 and S3).

4A and 4B are diagrams for explaining an example of a method for calculating an error circle.

FIG. 4A is a diagram illustrating an example of an error circle calculation method according to a comparative example, and as shown in FIG. 1A, shows a calculation method assuming that the distance measurement signal is not shielded by the top plate of the vehicle. .. On the other hand, FIG. 4B is a diagram for explaining an example of the error circle calculation method according to the present embodiment, and as shown in FIG. 1B, the calculation method assuming that the distance measurement signal is shielded by the top plate of the vehicle. Is shown.

In FIGS. 4A and 4B, the horizontal axis represents the longitude direction, the vertical axis represents the latitude direction, and the center point where the vertical axis and the horizontal axis intersect is the most probable position estimated from a plurality of positioning points (here, an error circle). Represents the center point of). Further, in FIG. 4A, the dotted line R1 represents an error circle, and the dot T1 represents a positioning point (the shaded area is the distribution area of the dot T1). Further, in FIG. 4B, the dotted line R2 represents the error circle, the solid line R2a represents the corrected error circle, and the dot T2 represents the positioning point (the shaded area is the distribution area of the dot T2).

If the ranging signal is not shielded by the top plate of the vehicle, positioning errors randomly appear in each direction at the positioning point T1 as shown in FIG. 4A. In other words, the positioning points T1 are distributed in a substantially circular shape. From this point of view, the center of the error circle R1 and the radius of the error circle R1 are usually calculated on the assumption that the positioning errors of the plurality of positioning points T1 are normally distributed in two dimensions with respect to the latitude direction and the longitude direction. Then, the radius of the error circle R1 at this time is obtained as, for example, the distance from the center point of the error circle R1 to the positioning point T1 farthest from the center point of the error circle R1 so that all the positioning points T1 are included in the error circle R1.

On the other hand, when the distance measurement signal is shielded by the top plate of the vehicle, the GPS antenna 10 is in a state where it cannot receive the distance measurement signal coming from the rear side of the vehicle, and can be used to calculate the positioning point T2. GPS satellites are restricted to the front side of the vehicle only (see Figure 1B). Therefore, the positioning accuracy in the predetermined direction (the lower left direction in FIG. 4B) deteriorates, and the positioning point T2 having a large positioning error exists only in that direction. Therefore, at this time, if the error circle R2 is calculated by the same calculation method as in FIG. 4A, the radius of the error circle R2 becomes large due to the positioning point T2 in which the positioning error is large.

The present inventors diligently studied the above problem, and in consideration of such directional characteristics, set the positioning point calculated by deviating to the direction in which the ranging signal is not shielded (hereinafter referred to as "reception direction"). I came up with the idea that it is possible to reduce the radius of the error circle by setting the radius of the error circle as a reference.

Specifically, the error circle setting unit 32 first uses the same method as the above-mentioned calculation method, assuming that the errors of each of the plurality of positioning points are two-dimensionally normally distributed in the latitude and longitude directions, and the error circle R2. The center point and radius (dotted line R2 in FIG. 4B) are calculated (step S2). At this time, the error circle setting unit 32 sets the direction opposite to the direction in which the positioning point T2 extends far from the center point of the error circle R2 (the upper right direction in FIG. 4B) as the receiving direction of the ranging signal. Identify.

Next, the error circle setting unit 32 refers to the positioning point T2 calculated at a position deviated to the reception direction side with respect to the center point of the error circle R2, and the distance between the positioning point T2 and the center of the error circle R2. Is calculated. Then, the error circle setting unit 32 determines the calculated distance as the radius of the error circle (solid line R2a in FIG. 4B), and corrects the radius of the error circle R2 pseudo-calculated above (step S3). By doing so, the radius of the error circle can be set without considering the positioning point T2 in which the positioning error in the predetermined direction is large, which is generated by the distance measurement signal being shielded by the top plate of the vehicle.

However, the calculation method at this time can be variously modified. For example, the error circle setting unit 32 may set the relationship between the error circle before correction and the directivity characteristic in advance, and after specifying the receiving direction, correct the error circle based on the directivity characteristic. .. Further, the error circle setting unit 32 may specify the receiving direction based on the direction in which the vehicle is traveling and the signal strength of the distance measuring signal. Further, the error circle setting unit 32 may be configured to calculate the error circle again by excluding the positioning point at the end on the side where the positioning error is large from the calculation symmetry.

Next, the map matching unit 33 performs map matching processing based on the error circle obtained in step S3, and determines the position of the vehicle (step S4).

The map matching unit 33 refers to, for example, map data stored in a storage unit such as a RAM, and superimposes the error circle obtained above on the map of the map data. Then, the map matching unit 33 determines the most probable position (for example, the position near the center of the error circle) at the position where the error circle and the road overlap as the position of the vehicle.

As described above, according to the positioning device 30 according to the present embodiment, an error circle having a radius based on the receiving direction of the GPS antenna 10 is set in consideration of the direction in which the ranging signal is shielded by the top plate of the cabin of the vehicle. can do. Therefore, even when the distance measurement signal from one side is shielded by the top plate of the cabin and cannot be received, the expansion of the error circle can be suppressed and the error circle with high accuracy can be set. Thereby, for example, the position of the vehicle can be determined more accurately in the map matching process.

(Second Embodiment)
Next, the GPS receiver 1 according to the second embodiment will be described.

The GPS receiver 1 according to the first embodiment is different from the first embodiment in that the GPS antenna 10 is arranged in the cabin of the vehicle so that the directivity direction of the GPS antenna 10 faces the front side of the vehicle. It's different.

FIG. 5 is a diagram showing an example of the arrangement state of the GPS antenna 10 according to the present embodiment.

The GPS antenna 10 generally has directivity (for example, a solid angle of about π [sr]). Therefore, if the GPS antenna 10 is arranged so that the directivity direction of the GPS antenna 10 faces upward in the vertical direction, the positioning accuracy will be further improved if the distance measurement signal is shielded by the top plate of the cabin. It gets worse.

In this regard, in the present embodiment, the GPS antenna 10 is arranged so that the directivity direction of the GPS antenna 10 is tilted from the upper side in the vertical direction to the front side by a certain degree (for example, 30 degrees). FIG. 5 shows that the GPS antenna 10 (indicated as L1 in FIG. 5) has sensitivity to a ranging signal in a predetermined angle range on the front side of the vehicle. As a result, it is possible to increase the sensitivity to the ranging signal coming from the front side of the vehicle and suppress the deterioration of the positioning accuracy.

As described above, according to the GPS receiver 1 according to the present embodiment, it is possible to set an error circle with higher accuracy.

(Other embodiments)
The present invention is not limited to the above embodiment, and various modifications can be considered.

In the above embodiment, as an example of the positioning device 30, the functions of the positioning unit 31, the error circle setting unit 32, the map matching unit 33, and the like are described as being realized by one computer, but they are realized by a plurality of computers. Of course, it is also good. For example, the function of the positioning unit 31 may be realized by performing arithmetic processing in a distributed manner by a plurality of computers.

Further, in the above embodiment, as an example of the positioning device 30, the processing of the positioning unit 31, the error circle setting unit 32, and the map matching unit 33 is shown to be executed in a series of flows. Some may be executed in parallel.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

The positioning device according to the present disclosure can be suitably used for a GPS receiver mounted on a large vehicle such as a truck.

1 GPS receiver 10 GPS antenna 20 receiver 30 positioning device

Claims (3)

A positioning device that receives ranging signals transmitted from a plurality of GPS satellites via GPS antennas arranged in the cabin of a vehicle.
A positioning unit that calculates a positioning point indicating the position of the vehicle based on the ranging signal, and a positioning unit.
Based on the direction in which the vehicle is traveling or the signal strength of the ranging signal, the receiving direction of the ranging signal is specified, and based on the plurality of positioning points calculated by the positioning unit within a predetermined time. An error circle setting unit that sets the center point of the error circle , assuming that the positioning errors of each of the plurality of positioning points are normally distributed in two dimensions with respect to the latitude and longitude directions.
With
Among the plurality of positioning points calculated by the positioning unit within the predetermined time, the error circle setting unit selects only the positioning point calculated at a position deviated to the reception direction side of the distance measurement signal. With reference to this, the distance to the positioning point calculated at the position farthest from the center point of the error circle is set as the radius of the error circle.
The GPS antenna is arranged in the cabin of the vehicle so that the directivity direction of the GPS antenna faces the front side of the vehicle.
Positioning device. Refer to the map data including road information,
A map matching unit for determining the position of the vehicle based on the map data and the error circle is further provided.
The positioning device according to claim 1. The cabin of the vehicle has an upright windshield.
The positioning device according to claim 1 or 2.

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