JP3488983B2 - Vehicle navigation system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a vehicle speed sensor or a GP.
The present invention relates to a vehicle navigation device that detects a traveling speed of a vehicle by using a GPS signal from an S satellite.

[0002]

2. Description of the Related Art There is known a vehicular navigation device which automatically detects a traveling distance and a traveling speed of a vehicle by using a vehicle speed sensor or the like. Since the sensor output of the vehicle speed sensor or the like contains some error, it is necessary to calibrate the sensor output periodically. Various methods are conceivable for the calibration method. For example, in the device disclosed in Japanese Patent Laid-Open No. 57-206815, the vehicle travels between two points whose actual distances are known and the distance is measured using a vehicle speed sensor. The sensor output is calibrated by comparing the measured distance with the actual distance.

[0003]

However, when performing calibration with this type of device, it is necessary to move the vehicle to one of the above two points and manually instruct the start and end of measurement. In addition to being cumbersome, errors are likely to occur because humans give instructions for calibration. On the other hand, the vehicle speed sensor used for detecting the traveling distance and the traveling speed of the vehicle generates a predetermined number of pulses per one rotation of the wheel, and the traveling distance of the vehicle is determined by the number of pulses and the tire diameter. Further, the vehicle traveling speed is obtained from the traveling distance in units of a predetermined time.

However, since the tire diameter differs depending on the type of tire, it is necessary to measure the tire diameter in advance in order to accurately obtain the traveling distance. However, it is troublesome to measure the tire diameter every time the traveling distance is obtained, and it takes time to obtain the traveling distance. In order to solve such a problem, for example, a ROM storing the vehicle speed sensor calibration value for each tire type may be provided, but the tire gradually wears down as the vehicle is repeatedly run, and the tire speed is reduced by the vehicle running speed and vehicle weight. Since the air pressure also changes, the tire diameter changes accordingly. Therefore, even if the calibration is performed based on the contents of the ROM, it is not possible to perform highly accurate calibration. Further, if the calibration is performed based on the stored contents of the ROM, the calibration cannot be performed when the tire having a tire diameter not stored in the ROM is replaced.

It is an object of the present invention to provide a vehicular navigation device which is capable of accurately obtaining a vehicle traveling speed.

[0006]

When in association with FIG. 1 showing an embodiment illustrating the present invention SUMMARY OF THE INVENTION The present invention provides a wheel revolution per
Pulse generator 1 that outputs a predetermined number of pulses
The number of output pulses CC of the pulse generator 1 during the interval T and the pulse
Distance traveled by the vehicle at the output pulse interval of the pulse generator 1
Based on k (hereinafter referred to as the pulse distance),
The speed for calculating the running speed (hereinafter referred to as sensor speed) V D
And capacitors speed calculating means 5, a GPS receiver 3 for receiving a GPS signal, the running speed (hereinafter of the vehicle based on the GPS signal
Below, GPS speed) GPS speed calculation to calculate V G
Means 5, GPS speed V G , predetermined time T and output pulse
Output pulse interval of the pulse generator 1 based on the number of pulses CC
Vehicle mileage (hereinafter referred to as theoretical pulse distance)
U) The theoretical pulse distance calculation means 5 for calculating k G
Estimate the reliability r of the GPS speed V G according to the sensor speed V D
Reliability estimation means 5 and the larger the reliability r,
A pulse that corrects the inter-pulse distance k to a value close to the inter-pulse distance k G.
And a GPS speed V G and its correspondence
The sensor speed V D is modified based on the dependence r . Claim 2
The invention according to is the vehicle navigation apparatus according to claim 1, the average value k G theoretical pulse distance k G
average value calculation hand for calculating the av, the average value r av of reliability r
The step 5 is provided, and the reliability between the pulse distance correction means 5 is increased.
The larger the average value r av, the average value of theoretical pulse distances k Gav
The inter-pulse distance k is corrected to a value close to. According to a third aspect of the present invention, in the vehicular navigation device according to the first or second aspect, the inter-pulse distance correcting means 5 is used.
The absolute difference between the GPS speed V G and the sensor speed V D
If the value exceeds the specified value, correct the inter-pulse distance k.
I did not try to avoid it.

[0007]

In the invention described in claim 1,During a predetermined time T
The number of output pulses CC of the pulse generator and the output of the pulse generator
Vehicle mileage at force pulse intervals (distance between pulses)
Based on k and the traveling speed (sensor speed) V of the vehicle D To
The vehicle speed is calculated by receiving GPS signals
Degree (GPS speed) V G Is calculated. Also, the GPS speed V
G , Based on the predetermined time T and the output pulse count CC,
Distance traveled by the pulse generator pulse (theory
Distance between pulses) k G And the sensor speed V D
According to GPS speed V G Estimate the reliability r of That
And the reliability r is larger, the theoretical pulse distance k G Close to
By correcting the inter-pulse distance k to the value,
Degree V G And the sensor speed V based on the reliability r D Fix
ItAccording to the invention of claim 2,Theoretical pulse distance k G
Mean k of Gav And the average value r of the reliability r av And compute
Average reliability r av Is larger, the theoretical average distance between pulses
k Gav The inter-pulse distance k is corrected to a value close to.Claim 3
In the invention described inGPS speed V G And sensor speed V D With
If the absolute value of the difference exceeds the specified value,
Do not modify.

Incidentally, in the section of means and action for solving the above-mentioned problems for explaining the constitution of the present invention, the drawings of the embodiments are used to make the present invention easy to understand. It is not limited to.

[0009]

1 is a block diagram of an embodiment of a vehicle navigation device according to the present invention. In FIG. 1, reference numeral 1 denotes a vehicle speed sensor for detecting a vehicle traveling speed, which is attached to, for example, a transmission of a vehicle and outputs a predetermined number of pulses per one rotation of a wheel. A bearing sensor 2 detects the traveling direction of the vehicle and outputs the angular velocity of the vehicle in the yaw direction. The traveling direction of the vehicle is detected by integrating this angular velocity. 3 is a GPS receiver for receiving GPS signals from GPS satellites (not shown). Reference numeral 4 denotes a map storage memory for storing road map data including intersection network data, which stores position information of nodes indicating intersections and curve points, path information of roads (links) connecting nodes and character information such as place names. Remember. 5 is shown in FIGS.
A CPU that performs the processing of 5, a ROM that stores a control program and the like executed by the CPU 5, and a RAM that stores the calculation result by the CPU 5. Reference numeral 8 is an operation board for inputting a destination and the like, 9 is a V-RAM for storing the image data created by the CPU 5, and this V-RA
Pictographic information is displayed on the display 10 according to the contents stored in M9. The above-described vehicle speed sensor 1, azimuth sensor 2, GPS receiver 3, map storage memory 4, CPU 5,
The ROM 6, the RAM 7, the operation board 8, the V-RAM 9, and the display 10 exchange signals with each other via the interface circuit 11.

2 to 4 each show an interrupt process performed by the CPU 5, FIG. 2 shows a vehicle speed pulse measurement process, FIG. 3 shows a vehicle speed detection process, and FIG. 4 shows a vehicle speed pulse interval correction process. CP
When an ignition key (not shown) is operated to the ON position, U5 controls the electric equipment of each part of the vehicle by a main process (not shown), and performs the interrupt process of FIGS. For example, the vehicle speed pulse measurement process of FIG.
Whenever a pulse is output from the vehicle, the vehicle speed detection process of FIG. 3 is performed about every 100 ms, and the vehicle speed pulse interval correction process of FIG. 4 is performed about every 1 sec. However, GP such as tunnels
If the vehicle is driving in an area where S signals cannot be received,
The processing interval in FIG. 4 becomes longer.

The operation of this embodiment will be described below with reference to these figures. In step S1 of the vehicle speed pulse measurement process shown in FIG. 2, the number of pulses output from the vehicle speed sensor 1 is measured and the process returns. Specifically, a variable C that measures the number of pulses each time a pulse is output from the vehicle speed sensor 1.
Is incremented by 1.

On the other hand, in step S11 of the vehicle speed detection processing shown in FIG. 3, the variable C measured in step S1 of FIG.
Is substituted into the variable CC, and in the next step S12, the variable C
To zero. Therefore, the variable C measures the number of vehicle speed pulses after this point. That is, the variable C measures the number of pulses output from the vehicle speed sensor 1 between the vehicle speed detection processing and the next vehicle speed detection processing. In step S13, the vehicle traveling speed V _D is calculated based on the equation (1). Note that k represents the distance traveled by the vehicle between the output of the vehicle speed pulse and the next output of the vehicle speed pulse (hereinafter, k is referred to as the inter-pulse distance),
T indicates a time interval for performing the vehicle speed detection process.

## EQU1 ## V _D = CC × k / T (1) Hereinafter, the speed V _D calculated based on the equation (1) will be referred to as a vehicle speed sensor calculated speed.

In step S14, the vehicle speed sensor calculation speed V _D calculated in step S13 is stored in the RAM 7 and the process returns. Since the inter-pulse distance k shown in the equation (1) is periodically corrected by the vehicle speed pulse interval correction processing of FIG. 4 which will be described later, the accuracy of the vehicle speed sensor calculation speed obtained in step S13 is increased.

In step S21 of the vehicle speed pulse interval correction process shown in FIG. 4, the vehicle traveling speed is calculated based on the GPS signal. This calculation is performed as follows. Let U (Ux, Uy, Uz) be the coordinate where the vehicle is located, G (Xi, Yi, Zi) be the coordinate G of the GPS satellite, and Ri be the true distance between the vehicle and the GPS satellite. The relational expression is represented by Expression (2). Note that i is a symbol that distinguishes GPS satellites.

## EQU2 ## (Xi-Ux) ² + (Yi-Uy) ² + (Zi-Uz) ² = Ri ² (2) By calculating the relationship of equation (2) for four different GPS satellites , Vehicle position U (Ux, Uy, Uz) can be obtained. Note that four GPS satellites are needed to obtain the vehicle position U because the true distance Ri includes a time component.

On the other hand, when the equation (2) is differentiated with respect to time, the equation (3) is obtained.

## EQU00003 ## (Xi-Ux). (Xi'-Ux ') + (Yi-Uy). (Yi'-Uy') + (Zi-Uz). (Zi'-Uz ') = Ri.Ri' ... (3) (Xi ', Yi', Zi ') in the equation (3) indicates the velocity component of the GPS satellite, and (Ux', Uy ', Uz') indicates the velocity component of the vehicle. The velocity component of the GPS satellite can be obtained by time-differentiating the orbital position of the satellite. Therefore, the vehicle speed V (Ux ′, Uy ′, U can be obtained by calculating the relationship of the equation (3) for four different GPS satellites.
z ') can be obtained.

The absolute value V _G of the vehicle speed is expressed by the equation (4).

## EQU4 ## V _G = {(Ux ') ² + (Uy') ² + (Uz ') ² } ^1/2 (4) In step S21 in FIG. 3, V is calculated based on the equation (4). _Ask for _G. Hereinafter, V _G will be referred to as the GPS calculation speed.

In step S22, the vehicle speed sensor calculation speed V _D stored in the RAM 7 is read. Step S
At 23, the vehicle speed sensor calculation speed V _D read from the RAM 7 is corrected. That is, when the vehicle travels at a high speed, the tire expands and the tire diameter increases, so the number of pulses output from the vehicle speed sensor 1 decreases and the detected vehicle speed becomes lower than the actual speed. Therefore,
In step S23, if the vehicle traveling speed is high, the calculated vehicle speed sensor calculation speed V _D is corrected to a higher speed. However, the process of step S23 is not essential and may be omitted.

In step S24, step S1 of FIG.
It is determined whether or not the absolute value of the difference between the vehicle speed sensor calculation speed V _D obtained in step ₃ and the GPS calculation speed V _G obtained in step S21 is larger than the threshold value TH1. This determination is provided because the GPS calculation speed obtained in step S21 varies greatly depending on the GPS signal reception state.
This is because the reliability of the calculation speed V _G may be extremely reduced. That is, when there is a radio wave obstacle such as a building near the vehicle, the GPS signal from the GPS satellite may be reflected by the building or the like to change the frequency or phase, or noise may lower the signal level. In such a case, the accuracy of the GPS calculation speed V _G calculated becomes poor. Therefore, in step S24, if the absolute value of the difference between the vehicle speed sensor calculated speed V _D and the GPS calculated speed V _G is larger than the threshold value TH1, it is determined that the GPS signal is abnormal and the process returns. That is, in this case,
The vehicle traveling speed is not corrected using the GPS calculation speed V _G.

Although the vehicle speed sensor calculation speed V _D may fluctuate due to tire replacement, tire wear, or the like, the fluctuation amount is much smaller than the GPS calculation speed V _G , and therefore in this step S24. Then, the variation amount of the GPS calculation speed V _G is determined with reference to the vehicle speed sensor calculation speed V _D.

On the other hand, if the determination in step S24 is negative, the process proceeds to step S25, and it is determined whether the vehicle speed sensor calculation speed V _D is smaller than the threshold value TH2. This judgment is provided when the vehicle traveling speed decreases and the GPS
This is because the accuracy of the calculation speed V _G becomes poor. For example, when the vehicle speed is 20 km / h or less, the GPS calculation speed V _G
Disable the vehicle speed correction using _G. If the determination in step S25 is affirmative, the process returns, and if the determination is negative, the process proceeds to step S26. In step S26, the reliability of the GPS calculation speed is estimated based on the equation (5).

[Number 5] _{r = f (V D) ···} (5)

As shown in the equation (5), the reliability r changes according to the vehicle speed sensor calculated speed V _D , and the relationship is shown in FIG.
It becomes like (a). As shown in the figure, the reliability is very poor when the vehicle traveling speed is about 20 km / h or less. Therefore, as shown in FIG. 5B, the vehicle traveling speed is about 20k.
When the reliability in the case of m / h is 0 and the reliability in the case where the vehicle traveling speed is sufficiently high is 1, the curve of FIG. 5A is extended in the vertical axis direction shown in the drawing, and the curve is created. Is used as a function f to obtain the reliability r.

In step S27, the coefficient k _G indicating the distance traveled by the vehicle from the output of the vehicle speed pulse to the output of the next vehicle speed pulse is determined based on the equation (6). Hereinafter, this coefficient k _G is called a theoretical pulse interval value.

[Equation 6] k _G = V _G × T / CC (6) In step S28, as shown in the equation (7), a value obtained by multiplying the theoretical pulse interval value k _G and the reliability r is sequentially applied. to add. Further, as shown in the equation (8), the reliability r is sequentially added. Further, as shown in the equation (9), 1 is added to the variable n indicating the number of calculations in step S28.

(7) S _kr = S _kr + k _G × r (7) S _r = S _r + r (8) n = n + 1 (9)

In step S29, it is determined whether or not the number of calculations n is less than a value TH3 indicating the number of thresholds. If the determination is affirmative, the process returns. If the determination is negative , the process proceeds to step S30. In step S30, (1
The average value kGav of the theoretical pulse interval values kG and the average value rav of the reliability r are calculated based on the equations (0) and (11).

[Equation 8] kGav = Skr / Sr (10) rav = Sr / n (11) As described above, the theoretical pulse interval value kG and the reliability r are averaged. kG and reliability r are both G
This is because it fluctuates according to the PS operation speed VG, so that the fluctuation is absorbed.

In step S31, the variables S _kr , S _r and n are reset. That is, the theoretical pulse interval value k _G
After obtaining each average value of the reliability r, the variables S _kr , S _r and n are once reset to obtain each average value again. In step S32, the pulse interval value k used in the process of step S13 of FIG. 3 is corrected based on the equation (12).

[Equation 9] k = (k _Gav −k) × r _av × k1 + k (12) The pulse interval value k is theoretical as the reliability average value r _av is closer to 1 as shown in the equation (12). The pulse interval value k _Gav is approached. Further, k1 in the equation (12) is a coefficient set in advance at the time of shipment, and changes in the range of 0 <k1 ≦ 1. The closer the k1 is to 1, the closer the pulse interval value k becomes to the theoretical pulse interval value k _Gav . Therefore, if the reliability of the GPS operation speed V _G is expected to be high, the coefficient k1 should be increased, and conversely, if the reliability of the GPS operation speed V _G is expected to be low, the coefficient k1 should be decreased. Good. For example, when it is desired to match the pulse interval value k with the theoretical pulse interval value k _G , if the coefficient k1 is 0.1 and the reliability average value r _av is 1, the process of step S31 needs to be performed 10 times. , Coefficient k1
If 1 is set to 1, it is sufficient to perform the process of step S31 once.

As described above, the vehicle speed pulse interval correction processing of FIG. 4 is summarized.
S calculation speed V _G is calculated, and _G is calculated in steps S24 and S25.
It is determined whether or not the correction using the PS signal is performed, the reliability r of the GPS calculation speed V _G is obtained in step S26, and the theoretical pulse interval value k _G is obtained in step S27. In steps S28 to S30, the theoretical pulse interval value k _G and the reliability r
Then, the average value of each of the
At 32, the pulse interval value k is modified. This step S3
The pulse interval value k corrected in 2 is used in the process of step S13 of FIG.

As described above, in the above embodiment, the vehicle traveling speed calculated using the vehicle speed sensor 1 is corrected in accordance with the vehicle traveling speed calculated using the GPS signal and the reliability thereof. A speed close to the true vehicle traveling speed can be calculated without being affected by changes or the like.

[0027] In the process of FIG. 4 is to modify the pulse interval value k by the theoretical pulse interval value k _G calculated based on the GPS operation speed V _G and reliability r, the reception state of the GPS signal stability In such a case, the theoretical pulse interval value k _G may be set as the pulse interval value k without considering the reliability r.
This shortens the processing time of FIG. In the vehicle speed pulse measurement process of FIG. 3, the CPU 5 is interrupted at predetermined time intervals to measure the number of pulses output from the vehicle speed sensor 1, but when the vehicle speed sensor 1 outputs a pulse, it automatically counts up. The number of pulses may be measured by a counter or the like.

In step S26 of FIG. 4, the reliability r of the GPS calculation speed is estimated using the function f in which the reliability r is 0 when the vehicle traveling speed is 20 km / h.
As shown in (a), the reliability r may be estimated using a function that also takes into consideration the reliability when the vehicle traveling speed is 20 km / h or less. In step S24 of FIG. 4, if the difference between the GPS calculated speed V _G and the vehicle speed sensor calculated speed V _D is less than or equal to the threshold value TH1, the vehicle running speed is not corrected using the GPS calculated speed V _G. However, if you set an upper limit on the difference and exceed the upper limit,
The correction by the GPS calculation speed V _G may not be performed. In step S32 of FIG. 4, the pulse interval value k is modified based on the expression (12), but the expression for modifying the pulse interval value k is not limited to the expression (12). That is, the equation may be such that the larger the average value of the reliability r is, the closer the pulse interval value k is to the value close to the average value of the theoretical pulse interval values.

In the embodiment configured as above, the vehicle speed
Sensor 1 is a pulse generator and CPU 5 is a sensor speed calculator.
Step, GPS speed calculation means, pulse distance calculation means, reliability
Degree estimation means, pulse distance correction means and average value calculator
Configure each step .

[0030]

As described above, according to the present invention ,
The car both running speed can be accurately obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a vehicle navigation device according to the present invention.

FIG. 2 is a flowchart showing a vehicle speed pulse measurement process by a CPU.

FIG. 3 is a flowchart showing a vehicle speed detection process by a CPU.

FIG. 4 is a flowchart showing a vehicle speed pulse interval correction process by a CPU.

FIG. 5 is a diagram showing a relationship between vehicle traveling speed and reliability.

[Explanation of symbols]

1 vehicle speed sensor 2 direction sensor 3 GPS receiver 4 map memory 5 CPU 6 ROM 7 RAM 8 operation board 9 V-RAM 10 display

Continuation of the front page (56) Reference JP-A-2-107985 (JP, A) JP-A-3-137515 (JP, A) JP-A-4-142480 (JP, A) JP-A-63-302317 (JP , A) JP-A-5-157828 (JP, A) JP-A-5-18776 (JP, A) JP-A-4-346023 (JP, A) JP-A-7-164830 (JP, A) JP-A-7-164830 (JP, A) 7-260502 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S 5/00-5/14 G01S 11/00 G01C 21/00

Claims (3)

(57) [Claims] 1. A predetermined number of pulses are output per wheel rotation.
Pulse generator, and the number of output pulses CC of the pulse generator during a predetermined time T
And the vehicle's output pulse interval of the pulse generator
Based on mileage (hereinafter referred to as pulse distance) k
Te, running speed of the vehicle (hereinafter, referred to as the sensor rate) the V D
A sensor speed computing means for computing a GPS receiver for receiving GPS signals, the traveling speed of the vehicle based on the GPS signal (hereinafter, GPS speed
GPS speed calculating means for calculating V G , GPS speed V G , predetermined time T and output pulse number CC
Based on the output pulse interval of the pulse generator
Vehicle mileage (hereinafter referred to as theoretical pulse distance) k G
For calculating the distance between theoretical pulses for calculating the distance, and estimating the reliability r of the GPS speed V G according to the sensor speed V D
The reliability estimation means and the larger the reliability r , the closer to the theoretical pulse distance k G.
Equipped with an inter-pulse distance correction means for correcting the inter-pulse distance k
E, sensor speed V D based on GPS speed V G and its reliability r
A vehicle navigation device characterized by modifying the following . 2. The vehicle navigation system according to claim 1, wherein the average value k Gav of the theoretical inter-pulse distances k G and the reliability r are averaged.
An average value calculating means for calculating the value r av is provided, and the inter-pulse distance correcting means has a large reliability average value r av.
The pulse is closer to the theoretical average distance between pulses k Gav
A vehicle navigation device characterized in that the inter-distance k is corrected . 3. A vehicle navigation system according to claim 1 or claim 2, wherein the pulse distance modifying means includes a GPS velocity V G sensor
If the absolute value of the difference from the speed V D exceeds the specified value,
A vehicular navigation device characterized in that the distance k between spaces is not corrected .