JPS63247613A - Navigation device for vehicle - Google Patents

Abstract

PURPOSE:To improve the accuracy of current position measurement by reading in a current position measured by a satellite utilizing position measuring means when the current position obtained by the satellite utilizing position measuring means is within the recognition error range of a current position obtained by a traveling history position measuring means. CONSTITUTION:The current position Pd is measured by the traveling history position measuring means 9 and at this time, a controller 10 multiplies the current traveling distance from a reference measurement position by a specific coefficient to calculate the value DELTALd of a measurement error. Then the satellite utilizing position measuring means 1 measures the current position. Then the distance D between the positions Pd and Pg is compared with DELTALd and when D<DELTALd, the measured value Pg is read in as the current value and displayed 16 while the position is stored as the reference position for current position measurement by the position measuring means 9. When it is decided that D>=DELTALd, on the other hand, the measured value Pd is read in as the current value. Namely, every time a position is measured, a measured position which has higher accuracy between measured positions of the position measuring means 1 and 9 is recognized as the current position to improve the measurement accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a navigation device for an automobile, and particularly a satellite-based positioning means that receives radio waves from a satellite and recognizes the current position of the vehicle, The present invention relates to a navigation device equipped with a travel history positioning means for detecting a travel history aW1 based on the travel history aW1.

(Prior art) As an automobile navigation device, for example,
As disclosed in Japanese Patent No. 8-70117, a vehicle is known that displays the current location of the vehicle and a map of its surroundings on the screen of a display device to provide driving 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 calculate the bearing by detecting the rotation difference between the left and right wheels, the steering angle of the steering wheel, etc., instead of using the bearing sensor. However, in such conventional current position recognition means, the current position of the vehicle is calculated by integrating the travel distance corresponding to changes in direction as the vehicle travels from a reference point. Since the current position is measured as a relative position to the reference point based on the travel history, accuracy decreases due to measurement errors in travel distance and direction, and this decrease in accuracy increases as the distance from the reference point increases. Note that means for measuring the current position based on the travel history from such a reference point is referred to as travel history 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 a satellite. For example, the Q global positioning satellite system currently under development
System (hereinafter referred to as GPS),
It is conceivable to measure the current position of the vehicle as an absolute position. This GPS uses four human satellites (NAVSTAR
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 W5 star is displayed on this map. The current position detected by the positioning means used is displayed. In addition,
As the vehicle moves, its current position also moves, so this movement needs to be displayed 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.

(Problems to be Solved by the Invention) When the above-mentioned navigation device is used, the current position of the vehicle can be detected as an absolute position, so the problem of cumulative 1t4 error as in driving history positioning means is eliminated. , the accuracy of measuring the current position using GPS is
There is a variation of about 30 meters, and this variation is often exacerbated by the position of each satellite and the reception condition of radio waves from the VFI star. There is a problem in that the measurement error is larger than the measurement error of the current position measured by the travel history positioning means. In particular, the measurement error caused by the positioning means for traveling 1i11ffl increases in proportion to the distance traveled (mw).
Since the difference is 4, when the travel distance from the measurement start point is short, the measurement error by the satellite-based positioning means 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 developed in view of the problem that the measurement error of the positioning method using the Wi star for the first time is larger than the measurement error of the driving history positioning means. Therefore, in the present invention, as a means to solve the above problem, the driving history The positioning means measures the current position, detects the size of the error in this measurement, and calculates the recognition error range of the current position centered on the measured current position based on the size of the measurement error. , determines whether the current position measured by the satellite-based positioning means is located within the recognition error range, and when the current position measured by the satellite-based positioning means is located within the recognition error range, the satellite-based positioning means In addition to reading the current position measured by the satellite-based positioning means as a value indicating the current position, if the current position measured by the satellite-based positioning means is outside the recognition error range, the current position measured by the travel history positioning means is read as the current position. The controller is equipped with a control device that reads the indicated value.

(Function) When using the navigation device according to the present invention having the above configuration, the current position is measured by the satellite-based positioning means and the current position is measured by the traveling FI history positioning means. At this time, the size of the measurement error of the travel history positioning means is detected, and based on this measurement error, the recognition error range of the current position measured by the travel history positioning means is calculated, and the recognition error range is calculated within this recognition error range. It is determined whether the current position measured by the satellite-based positioning means is located, and if it is located within the recognition error range, the position measured by the satellite-based positioning means is read as a value indicating the current position, and the recognition error is When the vehicle is located outside the range, the position measured by the travel history positioning means is read as a value indicating the current position. As a result, the position measured by the rear side means with higher measurement accuracy is recognized as the current position, and the accuracy of measurement of the current position is improved.

(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
'ff1 The current position of the vehicle is recognized from the radio waves received by the GPS receiver 2, the vehicle speed sensor 4a, which detects the vehicle speed, the geomagnetic sensor 4b, which detects the earth's magnetism, and the radio waves received by the GPS receiver 2. a current position recognition means 3 that recognizes the current position from a driving history based on signals from a vehicle speed sensor 4a, a geomagnetic sensor 4bhj, etc.;
The control device 10 receives the signal from the current position Z recognition means 3 and performs various signals and controls. Furthermore, this control device @10 includes a storage device 5 consisting of a compact disk, ROM, etc. that stores map information, etc., and an operation device @7 that performs various key operations, and a decoder 6, respectively.
and encoder 8, and CR
A display device 16 such as T and a video RAM 15 are connected via a display control device rH14.

A GPS receiver 2 and a current position recognition device 3 constitute a satellite-based positioning means 1, while a vehicle speed sensor 4a, a geomagnetic sensor 4b, and a current position recognition device 3 calculate a driving history and calculate the current position based on this driving history B. A travel history positioning means 9 is configured to perform recognition. Also, Ki'II!
! The device 5 stores roads, maps, etc. showing contents necessary for travel guidance of the J-YJ Kasa vehicle. The operating device 7 is
This is a key switch or the like that can be operated by the driver or the like, and the content displayed on the display 16 can be changed according to this operation.

The control circuit 10 consists of a microcomputer including an arithmetic 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 and the like via an interface 13 as shown. Then, in this control circuit 10, the current position of the vehicle is calculated based on the signal from the current position recognition device e13, a map around this current position is pulled out from the storage device 5, and this current position is displayed on the display 16. The data may be 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 device 3: recognition by the satellite-based positioning means 1 and recognition by the travel B history positioning means 9, as described above. In the σ device, for example, the size of the measurement error of the current position by the travel history positioning means 9 is detected, and the recognition error range of the current position centered on the current position measured by the travel history positioning means 9 is calculated. ,'fW when the current position measured by the FI star positioning means 1 is within the recognition error range.
The value of the current position measured by the I star-based positioning means 1 is read and the position of the lever 9 is displayed on the display 16, and on the other hand, the current position measured by the satellite-based positioning means 1 is outside the recognition error range. Sometimes, the value of the current position measured by the travel history positioning means 9 is read and this position is displayed on the display 16. Note that the magnitude of the error in measurement T by the satellite-based positioning means 1 is determined by the deterioration coefficient G, which will be described later.
D OP (Geometrical D 1lut
ionOf Precision>, and since the magnitude of the measurement error by the travel history positioning means 9 is a value proportional to the travel distance, the travel lf! It can be obtained by multiplying the 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. It constitutes the user part of the GPS, which determines the current position of the vehicle based on radio waves transmitted from four satellites 81 to S4 within the receivable area (field of view) of the stars. . Note that the positioning accuracy of this satellite-based positioning means 1 may decrease depending on the position of the satellite, perturbation of the satellite, the state of the ionosphere, etc., or it may become impossible to perform positioning in a region for a very short time. For example, when driving in a tunnel, obstacles on the ground may make it difficult or impossible to receive the necessary radio waves.

The degree of decrease in positioning accuracy in satellite-based positioning means 1 is as follows:
It 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 vehicle and the star used during positioning, 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, when the deterioration coefficient increases or the electric field strength decreases, the positioning WA difference increases. This deterioration coefficient is determined based on the position data of the curve tail used during positioning, the tracking results of the satellite by the ground antenna 1b, the satellite data of the ground monitor station 1C, etc. (1) Therefore, it is possible to obtain it from these, and the electric field strength can be detected by the strength of the 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 Fig. 4, there are three satellites S1, S2, and S3 in the user's field of view (receivable 1tl: area), and each
Assume that stars S1, S2, and S3 are transmitting ranging signals using clocks that are synchronized with each other. By measuring the reception time of these signals at the receiving point P, the distance between each satellite 81, 82, S3 and the receiving point 2 can be found, and the receiving point P is connected to each '# star S1, S2,
It can be determined as the intersection of three spherical surfaces centered at S3. However, synchronizing the clock at the receiving point P with that at the transmitting point is not only technically problematic, but also disadvantageous in terms of making the receiver inexpensive. The problem is receiving the signal′
# Solved by increasing the number of stars by one more. FIG. 4 shows this in a two-dimensional manner for easy understanding.

If the clock at the receiving point is behind the clock on each satellite by Δtu, the radius of the three measured circles will be larger than the actual one by Δtuc (c is the speed of light), and they should intersect at one point. The three power circles 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 determined at the same time as the position of the receiving point P. In GPS, a measured value of distance that differs by Δtuc from the true distance IRi with respect to '#ai is called a pseudorange. 'ffI The pseudorange MRi to star i is R
i = Ri +c △tai+c (Δtu-
Δtsvi). Here, △shi ai is the delay time of radio waves in the ionosphere and troposphere, and △tsvi is the time offset of the clock of satellite i. '#Atom F on a star! Instead of synchronizing them with each other, the meters measure their offset values, make predictions, and transmit the value from the satellite in a form that allows calculation of the value of Δtsvi. To perform 3D positioning 1
Using the measured values of the four pseudoranges for the four satellites = 1 to 4, it is possible to solve the three position coordinates and the total number of unknowns, ΔtU.

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

In addition, when determining the user's position based on the position of the satellite, the user must know the position of the satellite and the status of the clock on the satellite, which change from time to time, and these data are also used as described below. It will be broadcast from W1 Star.

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 MHz, and a first carrier wave (Ltl) which multiplies the frequency of the reference frequency signal to be outputted by 154 times. Ill transmission wave (15
75,42 MH2), and a transmitter 22 that multiplies the frequency of the reference frequency signal to 120@ to generate a second carrier wave, Lz111z wave (1227,6 MHz > sound formation 0).
6M multiplier 23. In addition, this transmitting circuit 20
consists of a clock forming circuit 24 that forms a clock signal of a predetermined period from a reference frequency signal, and a code that forms two types of code signals called P code and C/A code as ranging signals from the reference frequency signal and this clock signal. It has a transmitter 1 circuit 25 and a computer 26 whose timing is controlled by the clock signal and which outputs data regarding the position of the satellite and the status of the clock on the star W1, which changes from time to time. The P-code is a highly accurate and secret code that can only be used by the military and specially authorized users.
After being superimposed with the data output from
There is a long code p that is transmitted by orthogonally modulating two carrier waves, has a repetition rate of 10.23 Mbit/s, and lasts for one week. The C/A code is used for coarse image measurement (standard positioning) and P code capture, and is a code that is open to the public. This C/A code signal is
After being superimposed with the data output from 6, it is transmitted by modulating both Ll and Lz transmission waves, and the repetition rate is 1.0.
At 23 Mbit/S, the length is 1,023 bits, or repeated every 1113. 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 transmitted at a predetermined timing, for example, at a transmission rate of sob;t/S. In addition, this data includes the telemeter language, handover candy, parameters for ionospheric correction, Chikanobu correction for 1-frequency reception, the age of clock correction data, reference time for clock correction, GPS system fff interval, orbit prediction age,
Orbital element reference time, average periapsis angle at orbital element reference time, eccentricity, square root of semimajor axis, ascending node right ascension, orbital inclination, perigee argument, ascending node perturbation, mean motion correction, inclination angle It includes data such as correction parameters, correction terms for orbit deviation, satellite identification number, data subframe reference time, and satellite obscurity status. Also, if the user's receiver
# Predicting the period during which star signals can be received, selecting the combination of Nishio that will give the highest positioning accuracy from the satellites in the field of view,
Alnanac data of other satellites belonging to the system are also included so that the receiving circuit can be preset to capture signals from the WI star as quickly as possible.

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 10 arranged therein. The main control station 1a tracks the satellite via the ground antenna 1b, and uses the results to predict the clock on the star and the orbit of the lfj star, and stores them in the memory of the satellite so that they can be broadcast from the satellite. In addition to sending the data of
It was established to receive telemeters and commands necessary for star control, and is a manned facility equipped with a large paralysis machine and a series of operational control consoles. The monitor station 1C is an unmanned station equipped with an air contamination measuring instrument for receiving signals from satellites, an atomic clock, and calculating tropospheric delay.

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 reception n2 that receives signals from the required satellites and the received signals, and determines the position corresponding to the current position. It has a current position recognition device 3 that outputs a 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 edge 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 receiver 2
, a preamplifier 32 and a bandpass filter 33.

The GPS receiver 2 includes a frequency synthesis circuit 61 that 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 status of the clock on the satellite based on the reference frequency signal oscillated by the crystal oscillator 38. , inputs the clock signal output from the clock oscillation circuit 39,
The code generation circuit 62 forms a code signal having the same pattern as the ranging signal, and the output signals of the frequency synthesis circuit 61 and the code signal generation circuit 62 generate the clock on the satellite, the data regarding the orbit of the star '#I, and the carrier wave. It has a data and carrier wave detector 63 for correlation detection, and a code lock detector 64 for correlation detection of the distance measurement signal using the code signal output from the code generation circuit 62.

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.
The S receiver 2 is shown with two receiving channels, the first receiving channel being dedicated to sequentially switching reception of signals from the four satellites within the field of view, and the second receiving channel being dedicated to receiving signals from each satellite in its field of view. To eliminate interruptions in positioning due to sequential stoppage of reception to acquire data from satellites of the first reception channel, by acquiring broadcast data from satellites and preliminary acquisition of signals from satellites scheduled to be received next. is possible. In addition, in the case of a 5-channel receiver, 4 channels simultaneously and continuously track 4 satellites, and in parallel, the other channel performs preliminary acquisition of the next satellite to switch the star used. can be done instantly.

By the way, in GPS, all the errors associated with the measurement of the above-mentioned pseudo distance are converted into distance, and the equivalent measured distance 1 (Use
r Equivalent Range E
rrrr.

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

GPS α1 position error 1111 (positioning accuracy) is this UER
It can be found by simply multiplying E by the deterioration coefficient GDOP, and C/A
In the code, the positioning accuracy is nominally 4077L (50%) in radius for probability error (CEP).

(Table 1: Scales and magnitude of equivalent distance measurement error of user device, P code) In addition, as shown in FIG. and a current position recognition device 3 that measures the current position of the vehicle from these outputs and outputs a position signal corresponding to the current position to the control device 10.

A vehicle speed sensor 4at, a known rotation speed sensor, etc. are used,
By integrating the vehicle speed measured by this sensor 4a, the traveling distance is calculated, and by accumulating this traveling distance in correspondence with the change in the traveling direction detected by the geomagnetic sensor 4b, a driving history can be obtained. The driving route from the reference point is calculated using the following steps, and the current position is measured.

Since such driving history positioning means 9 is already well known, detailed explanation thereof will be omitted.

Did I explain it above? The operation of recognizing the current position by the navigation device having the i-publication positioning means 1 and the travel history positioning means 9 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. Next, in step 72, a predetermined coefficient (this value is determined by the accuracy of the distance sensor, etc.) is used to calculate the cumulative error in the distance traveled from the position po (Xo, Yo), which is the reference point for measurement by the travel history positioning means 9, to the present time. The magnitude of the measurement error Δld is determined by multiplying by Δld. This measurement error ΔLd represents the maximum error between the measured current position Pd and the actual current position, and if a circle with a radius ΔLd is drawn with Pd as the center, the area surrounded by this circle will be the current position determined by the travel history positioning means. This is the recognition error range, and the actual current position is located within this circle. After that, the process proceeds to step 73, where it is determined whether or not radio waves from the satellite are being received. If so, the current position PG (XQ, YQ) is measured using the positioning means using the VF1 positioning method. will be done.

At the same time, the magnitude of the measurement error ΔL (J) of the current position measured by the satellite-based positioning means 1 is calculated. This measurement error ΔL (J) is calculated from the user equivalent side distance difference (UERE) as described above. ) by the deterioration coefficient (GDOP).After this, the process proceeds to step 74, and the magnitude of the measurement error ΔLd by the driving history positioning means 9 obtained as described above is calculated by multiplying the measurement error ΔLd by the driving history positioning means 9. Compare the distance ii D + mF between the current measured position and the current position measured by the satellite-based positioning means 1. In the case of D ΔLd,
In step 75, WIfl=measured value PQ by the used positioning means ()1. Yq) is read as the current position and displayed on the display 16 as the current position, and this position is stored as a reference position Po (Xo, Yo) for subsequent current position measurement by the travel history positioning means 9. Ru. On the other hand, if it is detected in step 73 that the radio waves from the ¥fI star are not being received, the process proceeds to step 76, and in step 71
The value Pd (Xd.

Yd) as the current position, and this position is displayed on the display 16.
to be displayed. Further, although radio waves from the satellite are being received, if it is determined in step 74 that D≦ΔLd, the process proceeds to step 76, and the measured value Pd by the travel history positioning means 9 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 positioning means and the travel history positioning means, and the control device Detects the size of the measurement error of the driving history positioning method,
Calculates the recognition error range of the current position measured by the travel history positioning means based on this measurement error, and determines whether the current position measured by the satellite-based positioning means is located within this recognition error range; If the position is within the recognition error range, the position measured by the lff1 star positioning means is read as the value indicating the current position, and if the position is outside the recognition error range, the position measured by the travel history positioning means is read as the current position. Since it is read as a value indicating the current position, each time the current position is measured, the position measured by the one of the above two lateral means with higher measurement accuracy is recognized as the current position, improving the measurement accuracy of the current position. can be done.

[Brief explanation of drawings]

Fig. 1 is a body configuration diagram showing an 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 satellite 5 is a block diagram of the heavy-duty positioning means, and FIG. 6 is a flowchart 1 showing the operation of recognizing the current position by the navigation device according to the present invention.
~, Fig. 7 is an explanatory diagram for explaining the operation of recognizing the current position. 1... Positioning means using Saisei 1a... Main control station 1b.
...Ground antenna 1C... [Nita station 2...G
3 PS receivers 4a...Vehicle speed sensor 4b...Geomagnetic sensor 9...Driving history positioning means 10...
Control I equipment@16...Display unit 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 satellite-based positioning means measures the current position and the travel history positioning means measures the current position, and the magnitude of the positioning error of the current position by the travel history positioning means is detected, and based on the measurement error, the Calculate the recognition error range of the current position centered on the current position measured by the travel history positioning means, and if the current position measured by the satellite-based positioning means is located within the recognition error range, the above The current position measured by the satellite positioning means is read as a value indicating the current position, and if the current position measured by the satellite positioning means is outside the recognition error range, the travel history positioning means is used to read the current position measured by the satellite positioning means. A navigation device for a vehicle, comprising a control device that reads a measured current position as a value indicating the current position.