JPH0816698B2 - Mobile satellite navigation system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a mobile satellite navigation device that receives radio waves from a satellite and performs positioning of a vehicle traveling on the ground.

[Prior Art] Conventionally, as a device for detecting the position of a traveling vehicle and performing navigation, there is a means for performing positioning using a geomagnetic sensor, a rate gyro sensor, or the like. However, with such a means, there is a problem that errors are accumulated as the traveling distance is integrated.

As a device that solves this problem, there is a GPS (Global Positioning System) that detects the position of a vehicle based on radio waves from a plurality of satellites (hereinafter referred to as satellite radio waves).

That is, as shown in FIG. 2, 21 satellites 1 are arranged in a predetermined orbit, so that four or more satellite radio waves can be constantly received at any place on the ground. On the other hand, in the satellite navigation device on the moving body side, a plurality of satellite radio waves are received by a receiver, three distances to the moving body centered on each satellite are measured, and an intersection of circles having a radius of the satellite is obtained. Here, if three radio waves are received, the position of the moving body can be measured, but in reality, in order to measure the propagation time of the radio wave, it is necessary to have a very accurate clock on the receiving side.
Since this is difficult, four satellite radio waves are actually received because the distance to the satellite is actually obtained by using the fourth satellite radio wave for time correction. In this way, the current position of the moving body obtained at the intersection of the circles is converted into longitude, latitude and altitude, and the current position of the moving body is displayed on the map of the display device.

[Problems to be Solved by the Invention] However, in the above-described three-dimensional positioning device, when there is a building or the like that blocks satellite radio waves on the ground, only three or less satellite radio waves may be received. At this time, there is a problem that only the two-dimensional positioning is possible and the exact position of the traveling vehicle becomes unknown.

[Means for Solving the Problems] The present invention made to solve the above problems is the first aspect.
As shown in the figure, in a satellite navigation device for positioning a moving body based on radio waves from a plurality of satellites, a map information storage unit C that stores map information including altitude in advance, and at least three or more satellites. A receiver A for receiving radio waves from the receiver and separating and outputting the radio waves; a first computing means B for measuring a distance to each satellite based on the radio waves from the receiver A; A determination means D for determining whether or not the number of radio waves received by A is three, and when the determination means D determines that there are three radio waves, it is different from the radio waves from the satellite. Detecting means F for detecting the position of the moving body using the information of 1., estimated altitude setting means G for setting an altitude estimated value from the map information based on the information from the detecting means F, and the first calculating means. The distance obtained in B and the estimated altitude setting means G That it comprises a second calculating means E for obtaining the current position of the mobile body and spirit satellite navigation system of a mobile body, wherein on the basis of the estimated altitude value set Te.

Further, the detecting means F may be, for example, a geomagnetic direction sensor or a gyro sensor.

[Operation] First, in the present invention, at least three or more satellite radio waves are received by the receiver A, and each radio wave is separated and output. Each of these radio waves is input to the first calculation means B, and the distance to each satellite is measured.

On the other hand, when the determination unit D determines whether the number of the radio waves received by the receiver A is three and the detection unit F determines that the number of the radio waves received by the determination unit D is three, The position of the moving body is detected using information different from the radio waves from the satellite. Then, the estimated altitude setting means G sets the altitude estimated value from the map information based on the information from the detecting means F,
The second calculation means E calculates the current position of the moving body based on the distance calculated by the first calculation means B and the altitude estimated value set by the estimated altitude setting means G.

Therefore, even when only three distances to the satellite are required, the current position of the moving body can be obtained by being compensated by the map information stored in the map information storage means C, so that the current position with high accuracy can be obtained. Is obtained.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing a satellite navigation device, which receives radio waves from an artificial satellite moving in a predetermined orbit, that is, satellite radio waves subjected to spread spectrum modulation of 1.575 GHz and 1.227 GHz, and predetermined This is a device that obtains and displays the current position of the vehicle by performing the processing of.

In FIG. 3, the satellite navigation device comprises an antenna section 65, a main body section 66, an electronic control circuit 90, and a display device 14.

The antenna unit 65 includes an antenna 71, a first reception frequency converter 72 and a first reception local oscillator 72a, and a 1.575 [GHz] signal received by the antenna 71 is received by the first reception frequency converter 72. The signal is mixed with the transmission signal of the first receiving local oscillator 72a, converted into the first intermediate frequency of 75.42 [MHz], and transmitted to the main body 66.

In the main body 66, the transmitted signal is mixed by the second reception frequency converter 73 with the transmission signal of the second reception local oscillator 73a and converted into the second intermediate frequency of 10.7 [MHz], and thereafter, It is distributed to the first channel 74, the second channel 75, the third channel 76, and the fourth channel 77. Each channel 74
Since the configurations of Nos. 77 to 77 are the same, the first channel 74 will be described as an example.

The signal of the second intermediate frequency input to the spectrum despreader 81 of the first channel 74 is mixed with the pseudo noise output from the pseudo noise generator 82, and the original PSK (Phase Sh
ift Keying) signal is demodulated. Then bandpass filter 8
The signal passes through 3 and is converted by the third intermediate frequency converter 85 into the third intermediate frequency of 455 [KHz] by using the local oscillation frequency of the third receiving local oscillator 84 controlled by the electronic control circuit 90 described later. .

The signal converted to the third intermediate frequency is corrected so as not to include the Doppler shift. This signal is demodulated by the demodulator 86 and input to the electronic control circuit 90.

In addition, a range measuring instrument composed of a digital counter
87 measures a pseudo range signal corresponding to the distance from each satellite to the reception point and outputs it to the electronic control circuit 90.

The electronic control circuit 90 is configured as a logical operation circuit centering on the CPU 90a, the ROM 90b, the RAM 90c, is connected to the input / output unit 90e via the common bus 90d, and outputs signals between the channels 74 to 77 and the display device 14. To communicate.

Next, the vehicle positioning process executed by the electronic control circuit 90 of the satellite navigation device 62 will be described with reference to the flowchart of FIG. This flowchart is repeatedly executed every time the vehicle travels a predetermined distance.

First, in step 100, after reading the distance between the vehicle and the satellite from the main body 66 of the receiver, the process proceeds to step 110, and it is determined whether three-dimensional positioning is possible. That is, when it is possible to receive four radio waves from the satellite, determine whether or not the four distance information between the satellite and the vehicle required for three-dimensional positioning is required, and if four or more are required. In step 120, the current position of the vehicle is obtained by three-dimensional positioning.

The three-dimensional positioning process is executed according to the flowchart shown in FIG.

That is, in step 400, a process of selecting a combination of four satellites having the highest positioning accuracy is performed based on the orbital elements of each satellite stored in the ROM 90b. Next, in step 405, pseudo noise codes corresponding to the above four satellites are set. In the following step 410, the pseudo noise code is output to the pseudo noise generator 82 of each channel.
Next, in step 415, the Doppler frequency is calculated. In the following step 420, the third receiving local oscillator frequency determined according to the Doppler frequency is set to the third receiving local oscillator.
Output to 84. Next, go to step 425, wait until the synchronization with the signal from the satellite is completed, and if it is synchronized, step
Proceed to 430.

In step 430, a process of reading the data demodulated by the demodulator 86 is performed. In the following step 435, a process of calculating the position of each satellite at a predetermined time using the orbital elements of the satellite in the data is performed. This is achieved by iteratively solving the Kepler equation. Next, proceeding to step 440, processing for reading the range measurement value from the range deciding device 87 is performed. Next, in step 445, a process of calculating the current position of the reception point is performed by solving an equation in which the latitude, the longitude, the altitude of the reception point, and the difference between the reception side clock and the GPS time are unknowns.

That is, the distance to each satellite is obtained from the radio wave propagation time between each satellite and the receiving point, and each distance centered on the satellite is set as the radius, and the intersection point of the sphere centered on each satellite is the current position of the receiving point. Become. The present position thus obtained is displayed on the map of the display device 14 in step 180 of FIG.

On the other hand, when it is determined in step 110 in FIG. 4 that the three-dimensional positioning cannot be performed, that is, the radio wave from the satellite is 3
If only three can be received and only three distances to the satellite can be obtained, it is determined in step 130 whether or not the two-dimensional positioning process is the first time. Here, if it is determined that it is the first time, in step 140, the altitude E0 of the current position of the vehicle is estimated. As for the altitude, the current position of the moving body is measured by using a detecting unit such as a geomagnetic direction sensor or a gyro sensor, and the altitude information at the current position is output as an initial value according to the altitude on the map corresponding to the current position.

Next, in step 150, the map information including altitude information is read from the ROM 90b, and then the current position (N1, E1) of the vehicle is calculated from the distance obtained by the two-dimensional positioning and the estimated altitude E0 obtained in step 140. (Step 160). Here, as for the current position of the vehicle, the current position is obtained by the same processing as that shown in FIG. 5 for one sphere whose radius is the estimated altitude E0 as the center of the earth and three satellites. Next, at step 170, the altitude H1 (= (N1, E1)) corresponding to the position on the map is calculated using the current position (N1, E1) of the vehicle and the map.
Then, in step 180, the current position of the vehicle is displayed on the display device 14
Is displayed on the map on the screen, and this processing is once terminated.

Then, in the next process, if the two-dimensional positioning state continues, that is, if it is determined in step 130 that the two-dimensional positioning is not the first time, in step 150, after the map information is read. In step 160, the current position (N2, E2) of the vehicle is obtained from the three distances between the altitude E1 obtained in the previous processing (step 170) and the satellite obtained in this processing. Then, the altitude E2 (= (N2, E2)) corresponding to the current position (N2, E2) on the map is calculated, and the previously acquired altitude information E1 is updated to E2, and the display device 14 displays Display the current position (N2, E2).

After that, by repeating this process, the current position (Nn, En) of the vehicle is obtained from the two-dimensional positioning distance of the vehicle and the altitude that is sequentially updated, and displayed on the display device 14.

Therefore, according to the above-mentioned embodiment, when the three-dimensional positioning becomes impossible due to the obstacle of the satellite radio wave or the like, the two-dimensional positioning supplemented by the altitude information on the map is performed.

That is, in the flow chart of FIG. 4, when the altitude corresponding to the current position (Nn, En) of the vehicle is obtained from the altitude information on the map stored in advance, and this altitude cannot be three-dimensionally positioned. It is used as supplementary information.

By repeating the processing of the flowchart of FIG. 4 as described above, the current position gradually approaches the true current position of the vehicle as shown in FIG. This is because the vehicle usually travels only in a mountainous area, and there is usually no rapid change in altitude when traveling, so if the true current position is (N, E), the measured position is (N1 , E1) → (N2, E2) → (N3, E3), approaching the true position one after another.

In particular, the correct altitude Hn
When is calculated (including the case where it is calculated by accident), the true current position can be rapidly calculated. Then, once the altitude information at the true current position is obtained, all subsequent calculation results of the current position will output the true current position.

In other words, for vehicles traveling in areas other than mountainous areas, the altitudes on the ground surface do not differ much anywhere, so after providing approximate altitude information, accurate altitude information can be obtained from map information. The current position of the vehicle can be accurately obtained.

Moreover, it is possible to obtain the current position with higher accuracy than that obtained by the geomagnetic sensor or the like as described in the conventional technique.

In the above embodiment, the satellite navigation device is used as a three-dimensional positioning guarantee device, but may be configured as a two-dimensional positioning device independently to provide a simple satellite navigation device.

[Effects of the Invention] As described above, according to the present invention, the altitude estimation value is set from the map information stored in advance based on the current position of the moving body detected by the detecting means, and the set altitude is set. Since the current position is determined from the estimated value and the information from the three satellites, for example, a road with a sudden altitude change is approached,
Moreover, even when information is obtained only from three satellites, the current position can be located by the altitude estimation value according to the altitude after the altitude changes, and the positioning accuracy can be improved. Also, for example, when performing three-dimensional positioning,
Even if there is a building or the like on the ground that blocks the radio waves from satellites, the accurate position of the traveling vehicle can be known.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of the configuration of the present invention, and FIG. 2 is a GP.
FIG. 3 is an explanatory diagram for explaining the principle of S, FIG. 3 is a system configuration diagram showing a satellite navigation device for a vehicle according to an embodiment of the present invention, and FIG.
FIG. 5 is a flowchart for processing by the same embodiment, FIG. 5 is a flowchart showing processing by three-dimensional positioning, and FIG. 6 is an explanatory view for explaining the operation of the same embodiment. A ... Receiver, B ... First computing means C ... Map information storage means D ... Determination means E ... Second computing means F ... Detecting means G ... Estimated altitude setting means

Claims (2)

[Claims] 1. A satellite navigation device for positioning a mobile body based on radio waves from a plurality of satellites, comprising map information storage means for storing map information including altitude in advance, and at least three or more satellites. A receiver that receives radio waves and separates and outputs each radio wave, a first computing means that measures the distance to each satellite based on each radio wave from this receiver, and a radio wave received by the receiver Of the mobile unit using the information different from the radio wave from the satellite when the radio wave received by the decision unit determines that there are three radio waves. Detecting means for detecting a position, estimated altitude setting means for setting an estimated altitude value from the map information based on information from the detecting means, distance obtained by the first computing means, and estimated altitude setting means Based on the altitude estimate set in And a second computing means for determining the current position of the mobile body. 2. A satellite navigation system for a mobile body according to claim 1, wherein said detecting means is either a geomagnetic direction sensor or a gyro sensor.