JPS63238423A - Navigation apparatus - Google Patents

Abstract

PURPOSE:To enhance position measuring accuracy by detecting the magnitude of the measuring error of the present position due to a satellite utilizing measuring means and that of the measuring error due to a running history position measuring means. CONSTITUTION:At first, the present position Pd (Xd, Yd) is measured by a running history position measuring means 9. Subsequently, the cumulative error DELTALd from a measuring start reference position Po (Xo, Yo) to the present position is calculated. Herein, when a satellite radio wave is received, the present position Pg (Xg, Yg) is measured by a satellite utilizing position measuring means 1. At the same time, the magnitude DELTALg of the measuring error of the present position is calculated by the means 1. Next, the magnitudes of the measuring errors DELTALd, DELTALg are compared with each other and, at the time of DELTALd>DELTALg, the measured value Pg (Xg, Yg) is displayed on a display device 16 as the present position. When no satellite radio wave is received, the measured value Pd (Xd, Yd) is set as the present position and, when the satellite signal is received but DELTALd<DELTALg is judged, the measured value Pd is read as the present position.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a navigation device for an e-vehicle, particularly a satellite-based positioning means for receiving radio waves from Nishizato and recognizing the current position of the vehicle, and - This is a dispute regarding a navigation device equipped with a travel history positioning means that detects the travel history based on the travel history and detects the current position based on this travel history.

(Prior art) As an automobile navigation device, for example,
As disclosed in Japanese Patent Application No. 8-70117, there is a known vehicle that displays the current location of the vehicle and a map of its surroundings on the screen of a display device to provide travel guidance.

As means for recognizing the current position of a vehicle in such a navigation device, one using a direction sensor such as a geomagnetic sensor has already been put into practical use.

That is, the vehicle speed sensor and the azimuth sensor detect the distance and azimuth of the vehicle from a certain reference point, thereby recognizing the current position of the vehicle. Furthermore, it is also being considered to determine the orientation by detecting the rotation difference between the left and right wheels, the steering angle of the steering wheel, etc., without relying on the orientation sensor. However, in such conventional current position vjl recognition means, the current position of the vehicle is calculated by integrating the travel distance corresponding to the change in direction according to the travel from a reference point, that is,
Since the current position is measured relative to the reference point based on the travel history from the reference point, accuracy decreases due to measurement errors in travel distance and direction, and this decrease in viscosity increases as the distance from the reference point increases. Become. Note that the means for measuring the current position based on the travel 1i11ffl from such a reference point is the travel li! It is called historical positioning means.

Based on the above, it is conceivable to measure the current position of the vehicle as an absolute position using radio waves emitted from star '#1. For example, the Global Positioning Satellite System (Global Positioning Satellite System) currently under development
It is conceivable to measure the current position of the vehicle as an absolute position using the ngS system (hereinafter referred to as GPS). This GPS is for four artificial valves (NAVSTA
It is possible to measure the current position of a vehicle with a positioning accuracy of about 30 meters based on radio waves emitted from the C/A code (which is open to the public).

In a vehicle using a navigation device equipped with a satellite-based positioning means that detects the current position using GPS, for example, a map of the driving area is displayed on a screen such as an in-vehicle CRT, and the above-mentioned satellite-based positioning method is displayed on this map. The current position detected by the positioning means is displayed. Note that as the vehicle travels, its current position also moves, so it is necessary to display this movement on the screen. For this reason, the navigation device described above repeatedly receives radio waves from each satellite at predetermined intervals, detects the current position each time it is received, and displays the movement of the vehicle on the screen. ing.

(Problem to be Solved by the Invention) When the above navigation device is used, the current position of the vehicle can be detected as an absolute position, so
This eliminates the problem of cumulative errors that occur with i1N positioning methods, but the accuracy of measuring the current position using GPS varies by about 30 meters, and this variation is due to the position of each f# star and the difference from the satellite. This often worsens depending on the reception condition of radio waves, and in this case, the problem arises that the measurement error of the current position measured by the first-time satellite positioning method becomes larger than the measurement error of the current position measured by the driving history positioning method. be. In particular, since the measurement error by the travel R history positioning means is a cumulative error that increases in proportion to the travel distance, when the travel distance from the measurement start point is small,
The measurement error of the positioning means for star images using fFI stars tends to be larger.

(Means for solving the problem) As described above, by measuring the current position using satellite-based positioning means, the current position can be determined as an absolute position. If the reception is not good or the mileage is short,
The present invention was made in view of the problem that the measurement error of the satellite-based positioning means is larger than the measurement W4 difference of the travel history positioning means. Therefore, in the present invention, as a means to solve the above problem, f# The size of the measurement error of the current position by the star-based positioning means and the size of the measurement error by the above-mentioned traveling FIFfi positioning means are detected, and the current position measured by the positioning means with the smaller size among the plane measurement errors is detected. A control device is provided that reads the value as a value indicating the current position.

(Function) When using the navigation device according to the present invention having the above configuration, the current position is measured by the satellite first-use positioning means and the current position is measured by the travel history positioning means. The device detects the magnitude of the measurement error of both lateral means at this time, reads the current position measured by the positioning means with the smaller measurement error as the value indicating the current position, and thereby determines the measurement accuracy of the current position. I'm trying to improve it.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram showing an example of a vehicle navigation device according to the present invention. This navigation device is
A GPS receiver 2 receives radio waves from satellites, a vehicle speed sensor 4a detects vehicle speed, a geomagnetic sensor 4b detects geomagnetism, and the current position of the vehicle is recognized from the radio waves received by the GPS receiver 2. Current position recognition means 3 that recognizes the current position from the driving history based on signals from the vehicle speed sensor 4a and the geomagnetic sensor 4b, and control that performs various signal controls in response to signals from the current position recognition means 3. It has a device 10. Furthermore, a storage device 5 consisting of a compact disk, ROM, etc. that stores map information, etc., and an operating device 7 that performs various key operations are connected to this control device 10 via a decoder 6 and an encoder 8, respectively. At the same time, the display device 16 such as a CRT and the video RAM 15 are
connected via.

The GPS receiver 2 and the current position recognition device 3 constitute a satellite-based positioning means 1, while the TH speed sensor 4a, the geomagnetic sensor 4b, and the current position recognition device 3 calculate the driving history and calculate the current position based on this driving history. A driving history positioning means 9 is configured to recognize the position. Further, the storage device e15 stores maps and the like showing contents necessary for driving guidance of the vehicle such as roads and buildings. The operating device 7 is a key switch or the like that can be operated by a driver or the like, and can change the content displayed on the display 16 in response to this operation.

The control circuit 10 consists of a microcomputer equipped with an @hai circuit 12 and a ROM 11a and a RAM 11b connected thereto, and the arithmetic circuit 12 is connected to the current position recognition device 3 etc. via an interface 13 as shown in the figure. . Then, in this control circuit 10, the current position of the vehicle is calculated based on the signal from the current position recognition device 3, a map around the current position is pulled out from the storage device e15, and this current position is displayed on the display 16. It is displayed or stored in the video RAM 15. Note that there are two types of recognition of the current position by the current position recognition bag @3, as described above, recognition by the satellite-based positioning means 1 and recognition by the travel history positioning means 9. teeth,
For example, the size of the measurement error of the current position by the satellite-based positioning means 1 and the size of the measurement error of the current position by the travel history positioning means 9 are detected and compared. The current position value measured by the smaller positioning means is read and this position is displayed on the display 1.
It is designed to be displayed on 6. Note that the magnitude of the measurement error by the satellite first-use positioning means 1 is determined by the deterioration coefficient GDOP (Geomwtrical Diluti), which will be described later.
On Of Precision), and since the magnitude of the measurement error by the travel history positioning means 9 is a value proportional to the travel distance, it can be determined by multiplying the travel distance by the ratio that occurs as an accumulated error.

Here, first, the satellite-based positioning means 1 will be explained.

The satellite-based positioning means 1 includes 18 to 21 antennas controlled by a main control station 1a on the ground via, for example, four ground antennas 1b, which are appropriately distributed, in the case of GPS as schematically shown in FIG. 3, for example. Of the satellites, the receivable area (field of view)
It constitutes the user part of the GPS that measures the current position of the vehicle based on radio waves transmitted from four of the satellites 81 to S4. Note that the positioning accuracy of this wI foot-based positioning means 1 may be affected by the position of the satellite, perturbation of the satellite, the state of the ionosphere, etc., or the accuracy of positioning may decrease, or positioning may become impossible in a region for a very short time. Furthermore, obstacles on the ground, such as when driving in a tunnel, may make it difficult or impossible to receive the necessary radio waves.

The degree of deterioration in positioning accuracy in the WI foot-based positioning means 1 varies depending on the deterioration coefficient and electric field strength.

That is, the deterioration coefficient is a value determined by the geometrical relationship between the satellite used during positioning and the vehicle, and as the deterioration coefficient increases, the positioning error also increases and the positioning accuracy decreases. Other factors that cause the positioning accuracy to decrease appear as a decrease in electric field strength. Then, as the deterioration coefficient increases or the electric field strength decreases, the positioning error increases. This deterioration coefficient can be calculated from the position data of the satellite used during positioning, which is transmitted from each satellite based on the tracking results of the satellite by the ground antenna 1b and the data received by the ground monitor station 1c. is possible, and the electric field strength can be detected by the strength of radio waves received from the satellite.

The principle of positioning using GPS is as follows.

There is a clock that is perfectly synchronized at the transmitting and receiving points of radio waves,
Assuming that the transmitted signal is controlled by the clock, by measuring the timing of reception at the receiving point, we can find the propagation time of the radio wave between the transmitting and receiving points, and by multiplying it by the speed of light, we can calculate the distance between the transmitting and receiving points. You can ask for it. Now, as shown in Figure 4, there are three satellites S1, S2, and S3 in the user's field of view (receivable area).
2. Suppose that S3 is transmitting ranging signals using clocks that are synchronized with each other. By measuring the reception time of these signals at reception point P, the distance between each satellite S1, S2, S3 and reception point 2 can be found, and reception point P is the intersection of three spherical surfaces centered on each satellite S1, S2, S3. It can be found as However, synchronizing the clock at the receiving point P with that at the transmitting point is
This is not only technically problematic, but also disadvantageous in terms of making the receiver cheaper. This problem increases the number of satellites receiving the signal by one more.
Solved by @Increase/In. FIG. 4 shows this in a two-dimensional manner for easy understanding.

If the clock at the receiving point is behind the clock at each satellite by Δtu, the radii of the three measured circles will be larger than the actual ones by Δtuc (c is 1 degree of light), which means that there should be only one point. The three circles that should intersect no longer intersect (solid line diagram). By adjusting the value of Δtuc so that these three circles intersect at one point, Δtu can also be found at the same time as the position of the receiving point P.
You can In GPS, the measured value of the distance that differs from the true distance R1 to the satellite i by Δtuc is called a pseudorange. The pseudorange Ri to the satellite i is Ri =
It is expressed as Ri +cΔtai+c (Δtu−Δtsvi). Here, Δtai is the delay time of radio waves in the ionosphere and troposphere, and ΔtsviG is the time offset of the clock of satellite i. Instead of synchronizing each other, the atomic clocks on the satellite measure their offset values, make predictions, and transmit the value of Δtsvi from the satellite in a form that can be calculated. To perform three-dimensional positioning, it is possible to solve a total of four unknowns, three position coordinates and ΔtU, using the four pseudorange measurements for the four satellites i=1 to 4.

Similarly, measurements of the Doppler frequency, or pseudorange rate of change, of the II signal can be used to measure the user's three-dimensional velocity.

In addition, when determining the user's position based on the satellite position, the user must know the position of the II star and the status of the clock on the satellite, which change from time to time, and these data must also be known as described below. broadcast from satellite.

Each satellite is equipped with a receiving circuit (not shown) for receiving radio waves transmitted from the main control station 1a via the ground antenna 1b and a transmitting circuit 20 shown in FIG.

This transmitting circuit 20 includes a reference frequency oscillation circuit 21 that outputs a reference frequency signal of, for example, 10.23 MH2, and an L1 carrier wave (1575 ,42M
Hz), and a multiplier 23 that multiplies the frequency of the reference frequency signal by 120 times to form an L2 carrier wave (1227,6 MHz) as a second carrier wave. , this transmitting circuit 20 includes a clock forming circuit 24 that forms a clock signal of a predetermined period from a reference frequency signal, and two types of codes called P code and C/A code as ranging signals from the reference frequency signal and this clock signal. It has a code generation circuit 25 that forms a signal, and a computer 26 whose timing is controlled by the clock signal and outputs data regarding the constantly changing position of the satellite and the status of the clock on the satellite. It is a secret code that can only be used by users who have been specifically recognized as such, and after being superimposed on the data output from the computer 26, it is transmitted in the form of orthogonally modulating both the 1 and L2 carrier waves, and the repetition rate is 10. 23M
bit/s, a long code lasting one week.

The C/A code is used for coarse positioning (standard positioning) and P code acquisition, and is a code that is made available to the public. After this C/A code signal is superimposed with the data output from the computer 26, it is transmitted in the form of both Ll and Lz transmission modulation, and the repetition rate is 1.023 Mbit /
s, the length is 1,023 bits, or repeated every 'lns. It should be noted that the C/A code generation circuit is constituted by, for example, a gold code generation circuit using two 10-stage shift registers. The data output by the computer 26 is measured and predicted by a control section on the ground, stored in a storage circuit (not shown) of the satellite, and sequentially read out. These data are, for example, 50bit/s
It is transmitted at a predetermined timing at a transmission speed of In addition,
This data includes telemeter transmission, handover words, parameters for ionospheric correction, extension correction for single-frequency receivers, age of clock correction data, reference time for clock correction, GPS system time, age of orbit prediction, and orbit element information. Reference time, average periapsis angle at orbit element reference time, eccentricity, square root of major axis, right ascension of gastric intersection, orbital inclination, perigee argument, perturbation of ascending node, correction of average motion, parameters for inclination angle correction , orbit hole correction term, satellite identification number, data subframe reference time, satellite health status, etc. Also, the period during which the user's receiver can receive each satellite's signal. Other systems belonging to the system can be used to predict the number of Wi stars in the field of view, select the combination of satellites that will give the highest positioning accuracy from the Wi stars in the field of view, and preset the receiving circuit to capture signals from the satellites as quickly as possible. Satellite calendar (allanac)
>Includes data.

The above control section includes a main control station 1a, a ground antenna 1b placed at multiple fixed points on the ground (4 or more locations are planned), and a ground antenna 1b located at multiple fixed points on the ground (4 or more locations are planned). It has a monitor station 1C arranged therein. The main control station 1a tracks the satellite via the ground antenna 1b, predicts the clock on the satellite and the orbit of the satellite based on the results, and stores the data in the memory of the satellite so as to broadcast them from the satellite. It is a manned M-equipment equipped with a large computer and a series of operational control consoles, and is installed to transmit data as well as receive telemeters and commands necessary for controlling the satellite. Monitor station 1cG is an unmanned station equipped with a receiver for signals from satellites, an atomic clock, and a meteorological side instrument for calculating tropospheric delays.

As shown in FIG. 2, the satellite-based positioning means 1, which is the user part, measures the current position of the vehicle from the GPS receiver 2 that receives signals from the required satellites and the received signals, and measures the current position of the vehicle. It has a current position recognition device 3 that outputs a position signal. In addition, as shown in FIG. 6, the satellite-based positioning means 1
includes a crystal oscillator 38 that outputs a reference frequency signal that is an overall timing control signal, and a clock oscillation circuit 39 that forms a clock signal that controls the operation timing of the signal processing means 37 from this reference frequency signal. An antenna 31 connected to the front stage of the GPS reception island 2,
It has a preamplifier 32 and a bandpass filter 33.

The GPS receiver 2 has a frequency synthesis circuit 61 which generates a signal with the same pattern as the carrier wave of the satellite's transmitter 20 and data regarding the position of the satellite and the state of the clock on the lfi star based on the reference frequency signal oscillated by the crystal oscillator 38. and a code generation circuit 62 which inputs the clock signal output from the clock oscillation circuit 39 and forms a code signal having the same pattern as the ranging signal, and the frequency synthesis port 2861.
and 1! by the output signal of the code signal light main circuit 62!
a data and carrier wave detector 63 that performs correlation detection of data regarding the orbit of the clock and the satellite on the li star, and a carrier wave; and a code vine detector 64 that performs correlation detection of the distance measurement signal using the code signal output from the code generation circuit 62. have. Further, the timing of the signal processing means 37 is controlled by a clock signal output from a clock oscillation circuit 39.

In addition, Fig. 6 shows a GP with one receiving channel.
S reception n2 is shown, but two reception channels are provided, the first reception channel is dedicated to sequentially switching reception of signals from four satellites within the field of view, and the second reception channel is dedicated to receiving signals from each satellite. This method can be used to acquire broadcast data of the first channel and preliminary capture of signals from the satellite that is scheduled to be received next, and to eliminate interruptions in positioning due to successive reception stops in order to acquire data from the satellite of the first reception channel. It is possible. In addition, in the case of 5-channel reception, simultaneous and continuous tracking of 4 satellites is performed on 4 channels, and in parallel, preliminary acquisition of the next satellite is performed on the other channel, allowing instant switching of the satellites used. It is possible to do so.

By the way, in GPS, all the errors associated with the measurement of the above-mentioned pseudo distances are converted into distances, and the user equivalent distance measurement difference (jl s
er Equivalent Range E
rror.

(abbreviated as UERE). The causes of this UERE and the nominal values for each cause in the P code are shown in Table 1 below. In UERE in the C/A code, both the ionospheric error and the receiver error are thought to be several times larger.

The GPS positioning error value (positioning accuracy) can be found by simply multiplying this UERE by the deterioration coefficient GDOP, and in the C/A code, the positioning accuracy is nominally 40r in radius for probability error (CEP).
rt (50%).

(Table 1: Types and magnitudes of equivalent distance measurement errors of user equipment (P code)) Furthermore, as shown in FIG. The current position recognition device 3 measures the current position of the vehicle from these outputs and outputs a position signal corresponding to the current position to the control unit 11 @10.

The vehicle speed sensor 4a is a known rotational speed sensor or the like, and by integrating the vehicle speed measured by this sensor 4a, the traveling distance is calculated, and this traveling distance is accumulated in correspondence with the change in the traveling direction detected by the geomagnetic sensor 4b. By doing so, it is possible to obtain a travel history, and from this, a travel route from a reference point can be calculated and the current position can be measured. Since such driving history positioning means 9 is already well known, detailed explanation thereof will be omitted.

The operation of recognizing the current position by the navigation device having the satellite-based positioning means 1 and the travel history positioning means 9 described above will be explained based on the flowchart shown in FIG. 6 and the explanatory diagram of FIG. 7. In this operation, first, in step 71, the current position Pd (Xd, Yd) is measured by the travel history positioning means 9. Then, a predetermined coefficient (this value depends on the accuracy of the distance sensor, The magnitude of the measurement error ΔLd is determined by multiplying by the determined value). This measurement error ΔLd represents the maximum error between the measured current position Pd and the actual current position, and if a circle with radius ΔLd is drawn with Pd as the center, the actual current position will be located within this circle. 0 Next, in step 73, it is determined whether or not radio waves from the satellite are being received, and if so, the current position P9 (Xq, Yq) is measured by the satellite-based positioning means 1. At the same time, the magnitude of the measurement error ΔLCI of the current position measured by the satellite-based positioning means 1 is calculated. This measurement error Δ 9 is calculated by multiplying the user equivalent distance measurement difference (UERE) by the deterioration coefficient (GDOP), as described above. Thereafter, the process proceeds to step 74, where the magnitude of the measurement error ΔLd by the travel H history positioning means 9 obtained as described above is compared with the magnitude of the measurement error ΔLO by the satellite-based positioning means 1. ΔLd>ΔL
9, in step 75, the measured value Pch (Xg, Yq) by the satellite-based positioning means is read as the current position and displayed on the display 16 as the current position, and this position is used for subsequent driving history positioning. It is stored as a reference position po (Xo, YO) for measuring the current position by means 9. On the other hand, if it is detected in step 73 that radio waves from the satellite are not being received, the process proceeds to step 76, and the value Pd (Xd, Yd) measured by the driving history positioning means 9 in step 71 is set as the current position. The position is read and displayed on the display 16. Also, although radio waves from the satellite are being received, step 7
If it is determined in step 4 that Δld≦ΔLCI, the process proceeds to step 76, where the measured value P by the driving history positioning means 9 is determined.
d is read as the current position.

(Effects of the Invention) As described above, according to the present invention, the current position is measured by the satellite-based positioning means and the travel history positioning means are both measured, and the control device It is configured to detect the magnitude of the measurement error of both lateral means and read the current position measured by the positioning means with the smaller measurement error as the value indicating the current position. , the current position measured by the means with higher measurement accuracy at that time is displayed, and the recognition accuracy of the current position can be improved.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram showing one example of a navigation device according to the present invention, Fig. 2 is a perspective view showing an outline of GPS, Fig. 3 is an explanatory diagram of the principle of GPS positioning, and Fig. 4 is a diagram of a satellite. FIG. 5 is a block diagram of the transmitting circuit, FIG. 5 is a block diagram of the satellite-based positioning means, FIG. 6 is a flowchart showing the operation of recognizing the current position by the navigation device according to the present invention, and FIG. 7 is a flowchart showing the operation of recognizing the current position. It is an explanatory view for explaining operation. 1... Satellite-based positioning means 1a... Main control station 1b.
...Ground antenna 1C...Monitor station 2...G
PS receiver 4a...Vehicle speed sensor 4b...Geomagnetic sensor 9...Driving history positioning means 10...Control device 16...Display device 20...Transmission circuit~,

Claims (1)

[Scope of Claims] 1) Comprising a satellite-based positioning means for measuring the current position of the vehicle by receiving radio waves from a satellite, and a driving history positioning means for measuring the current position based on the driving history, The size of the measurement error of the current position by the satellite-based positioning means and the size of the measurement error by the travel history positioning means are detected, and the current position measured by the positioning means with the smaller size of both measurement errors is detected. A navigation device characterized by having a control device that reads a position as a value indicating a current position.