JP3584543B2 - Navigation device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a navigation device that is mounted on a moving body and detects the speed and the like.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, various navigation devices to be mounted on an automobile or the like have been developed. This navigation device includes, for example, a large-capacity data storage means such as a CD-ROM in which road map data is stored, a current position detection means, and a data read out from the data storage means of a road map near the detected current position. And a display device for displaying on the basis of. In this case, as a means for detecting the current position, a means using a positioning system (hereinafter simply referred to as GPS) using an artificial satellite for positioning called GPS (Global Positioning System), a traveling direction of the vehicle, and a traveling direction are used. For example, there is an autonomous navigation system that tracks a change in the current position from a departure point based on information such as speed.
[0003]
Here, if a positioning system using a positioning signal such as GPS is used, positioning with relatively high accuracy is possible, and the current position can be accurately known. However, in the case of such a positioning system, for example, the inside of a tunnel is required. In a state where a positioning signal from a satellite or the like cannot be received, such as when traveling, positioning cannot be performed.
[0004]
For this reason, navigation devices developed in recent years include both positioning by positioning signals such as GPS and positioning by autonomous navigation that tracks changes in position based on information such as the traveling direction and traveling speed of a vehicle. In some cases, positioning is performed by autonomous navigation during a period in which positioning cannot be performed by a positioning signal, so that positioning can be performed at all times.
[0005]
[Problems to be solved by the invention]
By the way, when positioning is performed by autonomous navigation, at least information on the traveling direction (traveling direction) and traveling speed of the vehicle is required, and the information on the traveling direction can be obtained using a gyro device, a geomagnetic sensor, or the like. In the case of an automobile, the information on the traveling speed can be obtained by counting the number of pulses output every predetermined rotation of a tire (axle) of the vehicle at predetermined time intervals.
[0006]
However, when the speed is detected from a pulse output in synchronization with the rotation of the tire of the vehicle, there is a problem that an error is easily generated in the detected speed. That is, the detected speed often deviates from the actual speed due to a change in various conditions such as a change in a tire air pressure, a change in a running environment, and the like.
[0007]
On the other hand, a positioning system using GPS has a function of detecting not only the position of the current position but also the speed of a vehicle equipped with a receiver based on the reception state of a positioning signal from a satellite.
[0008]
Therefore, in the case of a navigation device provided with both a positioning system by GPS and a positioning system by autonomous navigation, when positioning by GPS is possible, the speed information detected from the rotation speed of the axle and the speed information detected by GPS And if there is a difference, the detected speed value is corrected from the rotational speed of the axle.
[0009]
However, the speed value can be corrected only while the GPS positioning signal can be received, and it is difficult to correct the error of the detected speed value during the period when the GPS positioning signal cannot be received. If the period during which the positioning signal cannot be received continues for a long time, the speed at which the error is accumulated and detected has a large error, and there is a possibility that a large error occurs in the position to be located.
[0010]
For example, when a coefficient value (hereinafter, referred to as a vehicle speed coefficient value) for converting the number of pulses output for each predetermined rotation of the axle into speed information can be continuously corrected based on GPS reception data, Assume that there is a change shown as S1 in FIG. Here, if the positioning signal cannot be received by the GPS during the period from A to B indicated by the horizontal axis in FIG. 9, the coefficient value cannot be corrected during this period. Since the numerical value is maintained up to the point B, the change in the vehicle speed coefficient value used for the positioning in the autonomous navigation is S1 ', and the change S1 when continuously corrected and the uncorrected section An error occurs in a range X (a range indicated by hatching in FIG. 9) surrounded by a certain change S1 ', and a positioning error corresponding to the area of the range X accumulates.
[0011]
In view of the above, an object of the present invention is to make it possible to always accurately detect the speed of a moving body such as a vehicle in a navigation device of this type.
[0012]
[Means for Solving the Problems]
According to the present invention, when a speed proportional signal obtained from a moving object is multiplied by a predetermined coefficient and converted into speed information, at least two coefficients are prepared as conversion coefficients and based on speed information obtained by receiving a positioning signal. The at least two coefficients are updated in different modes, and at least two coefficients are selected according to the situation and used for conversion.
[0013]
[Action]
According to the present invention, it is possible to detect speed information with a small error by selecting a coefficient considered to be good according to the situation of the moving body and using the selected coefficient for conversion of speed information.
[0014]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0015]
FIG. 1 is a diagram showing the entire configuration of the present embodiment. In this embodiment, a navigation device 10 is mounted on an automobile (not shown). The navigation device 10 includes a GPS antenna 11 and the antenna 11 The GPS signal receiving unit 12 performs reception processing on the received positioning signal from the GPS satellite, and supplies the received data to the GPS positioning calculation unit 13. The GPS positioning calculation unit 13 analyzes the supplied reception data to calculate the current coordinate position and its altitude, and also calculates the moving speed and the traveling direction of the vehicle on which the navigation device 10 is mounted. . However, in the case of a positioning system based on GPS, it is difficult to accurately calculate the moving speed and traveling direction when the moving speed of the vehicle is low (for example, at a speed of 20 km / h or less). The data of the current coordinate position here is, for example, latitude and longitude data which is absolute position information.
[0016]
Then, each information such as the current coordinate position calculated by the GPS positioning calculation unit 13 is supplied to a central control unit (CPU) 14 that controls the positioning operation of the navigation device. The central controller 14 is connected to a RAM 15 and a CD-ROM driver 16. A CD-ROM (optical disk) in which road map data is stored is set in the CD-ROM driver 16. Under the control of the central control device 14, a reproduction process for reading the data stored in the CD-ROM is performed. Done.
[0017]
When the GPS positioning calculation unit 13 calculates the current position coordinates, the central control unit 14 performs control to read data of a road map near the coordinate position from the CD-ROM, and stores the read road map data. It is stored in the RAM 15. The central controller 14 reads out the road map data in the range to be displayed from the road map data stored in the RAM 15 and supplies the read road map data to the video signal generation circuit 17. Then, a video signal to be displayed is generated, and this video signal is output from the output terminal 18. The video signal for displaying the road map is a video signal for displaying some kind of mark or the like indicating the current position or the running locus, or various information such as the current speed or the traveling direction in characters or graphics.
[0018]
Then, the video signal output from the output terminal 18 is supplied to a display device 31, and the display device 31 performs an image receiving process based on the video signal, and displays a road map or the like on a display panel of the display device 31.
[0019]
In addition to displaying such a road map near the current position, a road map at a position instructed by the central controller 14 by operating the operation key 19 or the like is also displayed based on the control of the central controller 14. I can do it.
[0020]
Then, the navigation device 10 of the present example is capable of measuring the current position by autonomous navigation. That is, a pulse signal as a speed proportional signal supplied to the input terminal 21 from a pulse generator 32 provided on the side of the vehicle on which the navigation device 10 is mounted is counted by the pulse counter 22 and the traveling speed of the vehicle is counted. Is detected.
[0021]
In this case, the pulse signal output from the pulse generator 32 is a pulse signal proportional to the rotation speed of the axle of the vehicle. For example, when the vehicle is running at a certain speed, a pulse signal having a cycle shown in FIG. 2A is output, and as the running speed becomes faster than that, as shown in FIG. 2B and FIG. The cycle of the pulse signal is shortened. Then, the counter 22 can detect a count value proportional to the speed by counting the number of pulses during a predetermined period t ₁ (for example, one second) as shown in FIG. 2, for example. The count data of the counter 22 is supplied to the autonomous navigation positioning calculation unit 23, and the count data is multiplied by a predetermined vehicle speed coefficient value to obtain speed data.
[0022]
In this example, two kinds of vehicle speed coefficient values, a vehicle speed coefficient 1 based on a short-term average and a vehicle speed coefficient 2 based on a long-term average, are prepared. It is set, and after the start of travel, the correction coefficient value is sequentially corrected by a correction process described later so that accurate speed data can be obtained. Each vehicle speed coefficient value is stored in a predetermined area in the RAM 15 connected to the central control device 14, and the stored data is updated each time it is corrected.
[0023]
Further, the navigation device 10 includes a gyro device 24, detects a traveling direction of an automobile on which the navigation device 10 is mounted, and supplies the detected data to the positioning calculation unit 23 for autonomous navigation.
[0024]
Then, the autonomous navigation positioning calculation unit 23 calculates the running state of the vehicle based on the speed data calculated based on the supplied count data and the running direction data, and calculates the current position. In this case, when the GPS positioning calculation unit 13 can calculate the current position coordinates, the data of the current position coordinates is supplied to the autonomous navigation positioning calculation unit 23, and the coordinate position is used as a starting point to change the traveling state from there. The current position is calculated based on a travel locus based on the calculated position. When the current position coordinates cannot be calculated by the GPS positioning calculation unit 13, the data of the current position coordinates calculated by the autonomous navigation positioning calculation unit 23 is supplied to the central control unit 14. Based on the data of the current position coordinates, control is performed to cause the display device 31 to display the road map, the current position, and the like described above.
[0025]
Further, when the traveling speed is calculated by the arithmetic processing based on the positioning signal in the GPS positioning operation section 13, the speed data is supplied to the autonomous navigation positioning operation section.
[0026]
The autonomous navigation positioning calculation unit 23 sequentially determines the difference between the speed data supplied from the GPS positioning calculation unit 13 and the speed data calculated based on the supplied count data. If the difference is within a predetermined range, the vehicle speed coefficient value used for the calculation is corrected based on the speed difference.
[0027]
Next, a process of correcting the vehicle speed coefficient value by the navigation device of the present embodiment will be described with reference to the flowchart of FIG. In the following description, for the sake of simplicity, the speed data calculated by the GPS positioning system in the GPS positioning calculation unit 13 is used as GPS speed data, and the count value and the vehicle speed coefficient value of the counter 22 are calculated. Is used as sensor speed data.
[0028]
First, it is determined whether or not the GPS speed data supplied to the autonomous navigation positioning calculation unit 23 is within the usable range (step 101). In this determination, the speed data detected by the GPS positioning system has a large detection error at a low speed, and therefore, only when the speed is a certain speed (for example, 20 km / h or more), is the speed data within the usable range. And the process proceeds to step 102. When it is determined that the speed data is out of the usable range, or when the positioning signal cannot be received and the GPS speed data is not supplied, the process proceeds to step 107 in which the GPS speed data is not used.
[0029]
If it is determined that the GPS speed data is within the usable range and the process proceeds to step 102, it is determined whether the difference between the GPS speed data and the sensor speed data is within ± 3 m / sec. to decide. Here, if the difference between the two speeds is ± 3 m / sec or more, it is highly likely that the GPS speed data is erroneously detected data because the difference is large. Move to 107.
[0030]
When it is determined in step 102 that the difference between the two speeds is within ± 3 m / sec, a speed ratio between the GPS speed data and the sensor speed data is obtained (step 103). The calculation of the speed ratio is performed based on the following equation.
[0031]
(Equation 1)
Speed ratio = (GPS speed data) / (sensor speed data)
[0032]
Then, the process proceeds to step 104, which is a step of correcting the vehicle speed coefficient 1 which is the vehicle speed coefficient based on the short-time average. In this step, the vehicle speed coefficient 1 is updated based on the following equation.
[0033]
(Equation 2)
Vehicle speed coefficient 1 = (old vehicle speed coefficient 1 × speed ratio × COEF1) + [old vehicle speed coefficient 1 × (1-COEF1)]
Here, COEF1 is a value for obtaining a short-time average, and is a value between 0 and 1, here 0.01.
[0034]
Next, the process proceeds to step 105, which is a step of correcting the vehicle speed coefficient 2 which is the vehicle speed coefficient based on the long-term average. In this step, the vehicle speed coefficient 2 is updated based on the following equation.
[0035]
(Equation 3)
Vehicle speed coefficient 2 = (old vehicle speed coefficient 2 × speed ratio × COEF2) + [old vehicle speed coefficient 2 × (1-COEF2)]
Here, COEF2 is a value for obtaining a long-term average, and is a value between 0 and 1, here, 0.001.
[0036]
After the correction of the vehicle speed coefficient 1 and the vehicle speed coefficient 2, the sensor speed is obtained based on the following equation using the corrected vehicle speed coefficient 1 (step 106).
[0037]
(Equation 4)
Sensor speed = speed proportional signal x vehicle speed coefficient 1
In this case, the speed proportional signal is count data of the counter 22.
[0038]
Then, using the obtained sensor speed data and the like, the positioning calculation unit for autonomous navigation performs positioning calculation of the current position, and after a predetermined time, repeats the processing from step 101.
[0039]
Next, when it is determined in step 101 that the speed data is out of the usable range, or when the positioning signal cannot be received and the GPS speed data is not supplied, in step 102, the difference between the two speeds is ± 3 m / sec or more. A case will be described in which it is determined that there is, and the process proceeds to step 107. In this case, the vehicle speed coefficient 1 is corrected by the vehicle speed coefficient 2. The arithmetic expression in this case is shown by the following expression.
[0040]
(Equation 5)
Vehicle speed coefficient 1 = [old vehicle speed coefficient 1 × (1-COEF3)] + (vehicle speed coefficient 2 × COEF3)
Here, COEF3 is a value for bringing the vehicle speed coefficient 1 closer to the vehicle speed coefficient 2, and is a value between 0 and 1, here 0.01.
[0041]
Then, when the vehicle speed coefficient 1 is updated in step 107, the process proceeds to step 106, and the sensor speed is obtained by the above-described equation (4) using the updated vehicle speed coefficient 1 at this time. Using the sensor speed data and the like, the positioning calculation unit for autonomous navigation performs positioning calculation of the current position, and the processing from step 101 is repeatedly executed after a predetermined time.
[0042]
By updating the vehicle speed coefficient in the above processing, the navigation device of the present example can improve the accuracy in obtaining the current position by autonomous navigation. That is, if the vehicle speed coefficient 1 can be updated using the GPS speed data, the sensor speed is calculated based on the vehicle speed coefficient 1 corrected using the GPS speed data, and the sensor speed data is always accurate. A value process is performed.
[0043]
Then, when the vehicle speed coefficient 1 based on the short-term average is corrected, the vehicle speed coefficient 2 based on the long-term average is also corrected, and the data of the long-term average value of the vehicle speed coefficient has accurate data.
[0044]
Then, when the GPS speed data cannot be detected, an update process for gradually bringing the vehicle speed coefficient 1 closer to the vehicle speed coefficient 2 is performed by the calculation of Expression (5) shown in step 107 of the flowchart of FIG. Processing for obtaining sensor speed data based on the updated vehicle speed coefficient 1 is performed. Therefore, when the period during which the GPS speed data cannot be detected continues for a long time, the sensor speed data is finally calculated by the vehicle speed coefficient 2 based on the long-term average, and the error between the sensor speed data and the actual speed is calculated. It is more likely to be less.
[0045]
FIG. 4 is a diagram showing a time window when each of the vehicle speed coefficients 1 and 2 is calculated as an average value in the case of this example. As shown by a solid line in this figure, from a certain past time ta to a current time Tb. The weighting for obtaining the average vehicle speed coefficient increases as the time window increases exponentially and approaches the present time. The past time ta differs between the vehicle speed coefficient 1 and the vehicle speed coefficient 2. Then, by increasing the values of COEF1 and COEF2, the change of the time window becomes sharp as shown by the broken line in FIG. 4, and the average weighted more toward the current value is obtained, and the values of COEF1 and COEF2 are calculated. By making it smaller, the change in the time window becomes gentler as shown by the one-dot chain line in FIG. 4, and an average weighted more in the past is obtained.
[0046]
Here, it will be described with reference to FIG. 5 and FIG. 6 that the error in the sensor speed data is reduced by setting the vehicle speed coefficient as in this example. When the GPS speed data can be continuously detected, it is assumed that the vehicle speed coefficient 1 changes to the curve S1 shown in FIG. 5 and the vehicle speed coefficient 2 changes to the curve S2 shown in FIG. The running state of No. 5 is the same as the running state of FIG.
[0047]
Here, it is assumed that the GPS speed data cannot be detected from time A to time B. At this time, in the case of the present example, the vehicle speed coefficient 1 changes to the state shown by the curve S3 shown in FIG. The vehicle speed coefficient 1 shown by the curve S3 coincides with the original curve S1 of the vehicle speed coefficient 1 until time A when the GPS speed data can be detected, but after the time A elapses, the curve S2 of the vehicle speed coefficient 2 gradually increases. , And when the time during which the GPS speed data cannot be detected continues for a long time, the curve S2 of the vehicle speed coefficient 2 and the curve S3 match. When the GPS speed data can be detected again after the lapse of time B, the original vehicle speed coefficient 1 is corrected again, so that the curve S3 matches the original vehicle speed coefficient 1 curve S1.
[0048]
Therefore, the error range Y from time A to time B shown in FIG. 6 is a relatively small range, and a vehicle speed coefficient having a smaller error than the error range X shown in FIG. In a state in which is not detected, more accurate sensor speed data is calculated. For this reason, in the navigation device of this example, even if the period in which positioning is performed only by autonomous navigation continues for a long time, processing is performed to minimize the positioning error, and more accurate positioning is performed.
[0049]
In the above-described embodiment, as the processing for obtaining the vehicle speed coefficient 1 and the vehicle speed coefficient 2, the average is obtained in a time window that changes with an exponential curve as shown in FIG. 4, but the processing is performed in another processing. May be.
[0050]
For example, as shown in FIG. 7, when calculating the average from time ta to time tb, the same time window may be set at each point in time, and the vehicle speed coefficient 1 and the vehicle speed coefficient 2 may be calculated as a perfect average. good. In addition, as shown in FIG. 8, the time window may be linearly widened from time ta to time tb. Further, the vehicle speed coefficient 1, which is the short-time average, is obtained from the time window that increases with the exponential curve shown in FIG. 4 described above, and the vehicle speed coefficient 2, which is the long-time average, is calculated as shown in FIG. 7 or FIG. It may be determined by setting a time window.
[0051]
In the above-described embodiment, when the GPS speed data cannot be detected, the coefficient for obtaining the speed data is switched from the vehicle speed coefficient 1 to the vehicle speed coefficient 2 in the above-described embodiment. Although the switching is performed with a gradual change based on the value of the above, the coefficient for obtaining the speed data may be switched from the vehicle speed coefficient 1 to the vehicle speed coefficient 2 in a shorter time. In this case, for example, the vehicle speed coefficient may be switched from the vehicle speed coefficient 1 to the vehicle speed coefficient 2 instantaneously.
[0052]
Further, in the above embodiment, the vehicle speed coefficient 1 which is a short-time average and the vehicle speed coefficient 2 which is a long-time average are prepared, and these two types of coefficients are switched. Alternatively, three or more types of vehicle speed coefficients may be prepared, and the three or more types of vehicle speed coefficients may be appropriately selected.
[0053]
In the above-described embodiment, the present invention is applied to a navigation device using a positioning system called GPS. However, it is needless to say that the present invention can be applied to a navigation device combining another positioning system and a positioning system based on autonomous navigation. In addition, it can be applied to various navigation devices for mobile objects other than the navigation device for automobiles. However, since the form of the speed proportional signal obtained by the mounted moving body is different, it is necessary to change the processing in the navigation device (the counting processing by the pulse counter 22 in the above embodiment) correspondingly.
[0054]
【The invention's effect】
According to the present invention, it is possible to detect speed information with a small error by selecting a coefficient considered to be good and using it for conversion of speed information according to the situation of the moving object, and based on the detected speed information. Accurate navigation becomes possible.
[0055]
In this case, as the update by the coefficient updating means, based on the weight value set for each coefficient, a value between the coefficient value before the update and the coefficient value by the newly detected received signal is selected, By using the updated coefficient value, the detection is updated to better detection, and more accurate detection of speed information becomes possible.
[0056]
Further, in this case, the updating of at least one coefficient is a weighting value that is updated in a relatively short time to a value close to the coefficient value of the newly detected reception signal, and the updating of another coefficient is compared with the updating of another coefficient. By setting the weighting value to be updated to a value close to the coefficient value of the newly detected received signal in a very long time, it is possible to select an appropriate coefficient value according to the situation.
[0057]
Furthermore, by performing the current position positioning of the moving body based on the speed information thus obtained, accurate current position positioning with little error by autonomous navigation becomes possible.
[0058]
The current position measured in this way is displayed on the map displayed on the map display means, so that the navigation device operates well and always provides good navigation.
[0059]
Furthermore, by receiving a signal from a positioning signal transmitting artificial satellite such as a GPS and using it as a reference speed signal, the reference speed signal becomes an accurate value, and more accurate speed information is obtained. Detection becomes possible.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing one embodiment of the present invention.
FIG. 2 is a waveform diagram showing an example of a pulse as a vehicle speed proportional signal according to one embodiment.
FIG. 3 is a flowchart illustrating speed correction processing according to one embodiment.
FIG. 4 is an explanatory diagram showing a change state of a time window according to one embodiment.
FIG. 5 is a characteristic diagram illustrating an example of a change in a vehicle speed coefficient value according to one embodiment (in a case where correction is continuously performed).
FIG. 6 is a characteristic diagram showing an example of a change in a vehicle speed coefficient value according to one embodiment (a case where correction was not possible between times A and B).
FIG. 7 is an explanatory diagram showing a change state of a time window according to another embodiment of the present invention.
FIG. 8 is an explanatory diagram showing a change state of a time window according to still another embodiment of the present invention.
FIG. 9 is a characteristic diagram showing a conventional example of a change in a vehicle speed coefficient value.
[Explanation of symbols]
Reference Signs List 10 Navigation device 12 GPS signal receiving unit 13 GPS positioning calculation unit 14 Central control unit (CPU)
15 RAM
Reference Signs List 16 CD-ROM driver 17 Video signal generation circuit 22 Pulse counter 23 Positioning calculation unit for autonomous navigation 24 Gyro device 31 Display device 32 Pulse generator

Claims (6)

In a navigation device mounted on a moving body,
Conversion means for multiplying a speed proportional signal obtained from the moving body by a predetermined coefficient and converting the signal into speed information,
Storage means for storing at least two coefficients to be multiplied by the conversion means;
Means for receiving a positioning signal;
A calculating means for detecting speed information based on a reception state of the positioning signal received by the receiving means,
Coefficient updating means for updating the at least two coefficients in different modes based on the speed information based on the reception signal detected by the arithmetic means,
Selecting means for selecting a coefficient used for conversion by the conversion means. As updating by the coefficient updating means,
A request for selecting a value between a coefficient value before update and a coefficient value based on a newly detected received signal based on a weight value set for each coefficient to obtain an updated coefficient value. Item 4. The navigation device according to item 1. A weighting value for updating at least one coefficient to a value close to a coefficient value based on a newly detected received signal in a relatively short time;
3. The navigation device according to claim 2, wherein the updating of another coefficient is a weighting value which is updated to a value close to a coefficient value by a newly detected received signal for a relatively long time. 2. The navigation device according to claim 1, wherein the current position of the moving object is determined based on the speed information obtained by the conversion means. The navigation device according to claim 1, wherein the measured current position is displayed on a map displayed on a map display means. 2. The navigation device according to claim 1, wherein the receiving means receives a signal from a positioning signal transmitting artificial satellite.

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