JPH05312584A - On-vehicle navigation system - Google Patents

Abstract

PURPOSE:To improve the displaying accuracy of a navigation system equipped with a sign-post receiver in connection with the sign-post receiver. CONSTITUTION:The sign-post receiver 6 of this system is provided with an antenna 6a which receives radio waves from sign-post transmitters, receiving section 6b for demodulation connected to the antenna 6a, data processing section 6c connected to the section 6b, data output line 6d connecting the section 6c to a controller, and radio wave intensity measuring section 6e which measures the intensity of the radio waves received by the section 6b and sends the measured intensity to the section 6c. The section 6c outputs data containing received data and the time difference between the point of time at which the intensity reaches a peak and a predetermined point of time at which the data are sent to the controller at the predetermined point of time and the controller calculates the position data of its own vehicle and displays the data on a displaying section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted navigation system, and more particularly to a vehicle-mounted navigation system equipped with a sign post receiver as an auxiliary to a GPS receiver.

[0002]

2. Description of the Related Art Conventionally, as a vehicle-mounted navigation system equipped with a sign post receiver, the one shown in FIG. 7 is known. This navigation system
A controller 1 for controlling the entire system, and a display / operation unit 2, a CD-ROM unit 3, a vehicle speed sensor / gyro unit 4, a GPS (global positioning system) receiver 5 connected to and under the control of the controller 1. And a sign post receiver 6. CD-ROM
The unit 3 stores map data and associated data. The display / operation unit 2 is provided with operation buttons 2a and an LCD display device 2b, and a vehicle position mark 2c is displayed on the LCD display device 2b. GPS receiver 5
The absolute position of the own vehicle is calculated based on signals received from a plurality of satellites. The vehicle speed sensor outputs a pulse train having a pulse number proportional to, for example, the rotation speed of the axle.

In this navigation system,
The controller 1 reads the map data from the CD-ROM unit 3 and the position data from the GPS receiver 5, and displays the vehicle position mark 2c together with the road map on the LCD display 2b. This vehicle position mark 2c
When the GPS receiver 5 receives a signal from the satellite,
It is displayed based on the calculated absolute position. Also, G
Until the PS receiver 5 receives a new signal from the satellite,
Based on the output signal of the vehicle speed sensor / gyro unit 4, the moving direction and the moving distance are integrated, and the vehicle position is continuously displayed.
This fulfills the function of the navigator. Further, when the operation button 2a is operated, it is possible to enlarge or reduce the map and use a database (for example, tourist spot guide) attached to the map data.

The sign post receiver 6 is used as a countermeasure when a building is forested in an urban area or the like and radio waves from satellites cannot be received well. In such a case, the sign post receiver 6 is used. The position data obtained from is used as a supplement. The sign post transmitter opposite to the sign post receiver 6 is installed on the side post,
Point data of the installation point and traffic data are wirelessly transmitted from the sign post transmitter to the sign post receiver 6.

As shown in FIG. 8, this sign post receiver 6 is connected to a receiving section 6b connected to an antenna 6a, a data processing section 6c for receiving data from the receiving section 6b, and a data processing section 6c. Data output line 6d. FIG. 9 shows a transmission data format 70 on the side of the sign post transmitter, which is repeatedly transmitted.
2 shows a data format 60 after reception processing, which is output from the sign post receiver 6 to the controller 1.

The operation of the sign post receiver 6 will be described. The signal received by the antenna 6a is received by the receiving unit 6b.
Is demodulated by and transmitted to the data processing unit 6c. The data processing unit 6c performs processing according to the flow shown in FIG. First, in step P1 of FIG. 11, data reception waiting and reception processing are performed. That is, it waits until the reception, and at the time of the reception, an error check of the received data is performed, and if the data is normal in the check, the process proceeds to the next step P2. In this step P2, comparison with the previous data is performed. When it is determined in step P2 that the data is the same as the previous data, the interval check in step P3 is performed, and if 30 seconds (that is, the predetermined time) has not elapsed, the data to the controller 1 in the next step P4. Does not execute the sending process. That is, if the same data is received within 30 seconds, it is considered that the same data is received from the same place, and the position data is not output to the controller 1. As a result, new data (different from the previous data)
In this case, or even if the same data is received after 30 seconds have elapsed, the data 60 of the predetermined format shown in FIG. 10 is output to the controller 1 in step P4.

Signpost receiver 6 which functions in this way
Was expected to fully demonstrate its function in urban areas.

[0008]

However, since the sign post receiver 6 is designed to immediately send the data to the controller 1 when valid data can be received, for example, the sign post transmitter installation location. There is a problem in that the display accuracy is lowered, in which a position several tens of meters away from is erroneously recognized as the position of the sign post and a position deviating from the true own vehicle position is displayed as the own vehicle position. Also, the display position error is due to the installation conditions of the sign post transmitter and receiver,
The situation is not sufficient to achieve the intended purpose, such as fluctuations due to the congestion of vehicles running in parallel.

This situation will be described in detail with reference to FIG. FIG. 12 shows an example of the relationship between the received radio wave intensity and the data reception timing, with the vertical axis representing the received radio field intensity and the horizontal axis representing the time. When traveling at a constant speed, the horizontal axis is equivalent to the distance, so time can be read as “distance”.

Of the two curves A and B in FIG. 12, one curve A changes rapidly and crosses a preset threshold value I _th at times t = t _1a and t _3a . The other curve B changes gradually and its threshold value I _th is changed at times t = t _1b and t _3b.
Intersect with. The threshold value I _th is a radio wave intensity that does not cause an error in received data. That is, in the reception related to the one curve A, valid data reception is started at time t _1a and cannot be received after the time t _3a (reception end). Similarly, in the reception related to the other curve B, the time t _1b is the reception start and the time t _3b is the reception end.
It should be noted that time t ₂ existing between both times t _1a and t _3a (between t _1b and t _3b ) is the time at which the received radio wave intensity reaches the peak value, and corresponds to the transmitter installation place or a position in the vicinity thereof. ..

According to the conventional sign post receiver 6, the data is immediately sent to the controller 1 at the timing t _1a or t _1b , which causes an error in the sent position data. When the data is transmitted at the timing t ₂ at the peak of the radio wave intensity, there is almost no error in the position data, so the above error will be exemplified with reference to this. Now, assuming that the reception state is related to the curve A, t
_{If 2-} t _1a = 1 second and traveling speed = 40 km / h, the position error will be about 11 m, which is relatively small compared to the GPS receiver error of around 30 m, so the error is considered to be within the allowable range. You can also On the other hand, when the data related to the curve B is received, t ₂
Since −t _1b > 1 second (distance conversion: [> 11 m]), the position error cannot be ignored.

Whether the reception mode of the curve A or the reception mode of the curve B is as described above depends on the traveling speed and the radio wave propagation state being influenced by the traveling place and the traveling situation.
In particular, the sign post receiver cannot sufficiently perform the auxiliary function of the GPS receiver during traveling when only the reception mode of the curve B is obtained, the display accuracy of the vehicle position is reduced, and its reliability is also low. Was becoming.

The present invention has been made in view of the above conventional problems, and improves the display accuracy of a sign post receiver as an auxiliary device of a GPS receiver regardless of external factors such as running conditions and traffic conditions. That is the purpose.

[0014]

In order to achieve the above object, a vehicle-mounted navigation system of the present invention is a sign for receiving point information transmitted from a fixed transmission facility provided on a side road using radio waves as a medium. In the vehicle-mounted navigation system, which includes a post receiver, a controller that calculates the vehicle position based on the received information of the sign post receiver, and a display device that displays the vehicle position calculated by the controller, In the post receiver, receiving means for receiving the point information using the radio wave as a medium, radio wave intensity measuring means for measuring the intensity of the radio wave received by the receiving means, and radio wave intensity measured by the radio wave intensity measuring means. Based on this, the maximum intensity time point specifying means for specifying the time point when the radio field intensity exhibits the maximum value and the maximum intensity time point specifying means for specifying the maximum time point. Data for creating data that combines the time difference calculation means for calculating the time difference between the strength time point and the time point for transmitting the point information to be executed later, and the point information received by the receiving means and the time difference calculated by the time difference calculating means. The data creating means and the data sending means for sending the data created by the data creating means to the controller at the sending time are provided, and the controller is based on the point information and the time difference data sent from the data sending means. A vehicle position calculating means for calculating the vehicle position is provided. Particularly, the maximum intensity time point specifying means may be a means for estimating the reception time point of the maximum radio wave intensity based on the measurement result of the radio wave intensity measuring means.

[0015]

In the vehicle-mounted navigation system of the present invention, the spot information using the radio waves sent from the fixed transmission equipment as a medium is obtained by the receiving means of the sign post receiver.
The strength of the received radio wave is measured by the radio wave strength measuring means, and the time point at which the maximum value is exhibited is specified by the maximum strength time point specifying means based on the measured radio wave strength (the time point showing the maximum value is estimated. Sometimes). The time difference calculating means calculates the time difference between the specified time point of the maximum intensity and the time point of transmitting the point information after the specified time point. Data combining the point information received by the receiving means and the calculated time difference is created by the data creating means, and the data is sent from the data sending means to the controller at the sending time. The own vehicle position calculating means of the controller calculates a highly accurate own vehicle position in consideration of the time difference based on the sent point information and the time difference. This vehicle position is displayed on the display device.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. Here, the same or equivalent components as those of the conventional system described above are designated by the same reference numerals, and the description thereof will be omitted or simplified.

The overall configuration of the vehicle-mounted navigation system according to this embodiment is the same as that shown in FIG. 7, and the sign post receiver 6 is constructed as shown in FIG.

The sign post receiver 6 shown in FIG. 1 has a receiving antenna 6a equivalent to that shown in FIG.
Demodulation receiving unit 6b, data processing unit 6 responsible for data processing
In addition to c and its data output line 6d, a radio wave intensity measuring unit 6e is added. Radio wave strength measurement unit 6e
Is configured to measure the strength of the radio wave medium received by the receiving unit 6b and sequentially output the measurement result to the data processing unit 6c. The data processing unit 6c is provided with a microcomputer, and repeatedly executes the processing described in FIG. 2 to send data having a format shown in FIG.
The controller 1 performs the processing shown in FIG.

First, the processing shown in FIG. 2 will be described. In step P1 of FIG. 2, data reception waiting and processing at the time of reception are performed. That is, it waits until reception (step P1a), writes transmitter side data in the storage unit (step P1b),
Next, a data error check is performed (step P1
c) If the data is validated by the check, the process proceeds to the next step P2.

In step P2, comparison with the previous data is performed. If YES in step P2, that is, if it is determined to be the same as the previous data, the interval check in step P3 is performed, and it is determined, for example, whether 30 seconds (that is, a predetermined time) has elapsed. If the result of the determination in step P3 is NO, that is, if the predetermined time has not elapsed, the processes in the following steps P4 and P5 are not performed (that is, the radio wave intensity measurement and the data transmission process to the controller 1 are not performed) and the process is directly performed. It returns to step P1. Therefore, when the same data is received within a predetermined time of 30 seconds, it is considered that the same data is received from the same place, and the data regarding the point data shown in FIG. 3 is not sent to the controller 1.

However, it is judged YES in step P3, that is, even if the same data as the previous data is received after a predetermined time of 30 seconds has passed, NO in step P2, that is, new data (the previous data is In the case of (different), it is considered as a legitimate reception, and the processing of the next step P4 is performed.

In step P4, a process relating to peak detection of received radio waves is executed. First, step P4a
At, the intensity value of the radio wave measured by the radio wave intensity measuring unit 6e is read. Next, at step P4b, the threshold I _th (see FIG. 4) or more signal strength determined as a radio wave strength causing no error in the received data, stores the time that has reached its intensity and its intensity. This storage process is performed for all threshold values I _th , for example, between the reception start and reception end times t _{1 to} t _{3 according} to the radio field intensity curve in FIG. Then, in Step P4c, Step P4b
Based on the intensity data stored in
_max is _calculated , and time t when the peak value I _max is reached
Identify ₂ . Then proceeds to step P4d, future data sending predetermined a predetermined time t _alpha elapses a preset from the current time t ₃ time _{t 4 (= t 3 + t} α) is calculated (see FIG. 4). Further, the process proceeds to step P4e, and the time difference t _d = t ₄ −t ₂ from the scheduled data transmission time t ₄ to the time t ₂ at the peak time of the radio wave intensity is calculated as delay time data.

Next, returning to step P5, the transmission data 60 to the controller 1 is created in the format of FIG. In other words, this transmission data 60 is information type (1), point data transmitted from the sign post transmitter,
The delay time data t _d calculated in step P4e, information type (2), and traffic data.

When the transmission data has been created in this way, the data processing unit 6e waits until the data transmission scheduled time t _{4 in} the process of step P6, and then, in step P7, creates the transmission data 60 by the controller 1 Send to.

After that, the process returns to step P1 again to repeat the above-mentioned processing.

When the data 60 is sent from the sign post receiver 6 to the controller 1 in this way, the controller 1 changes from the state of waiting for reception in step P10 to the temporary own vehicle position in step P11 in the process of FIG. Enter into arithmetic processing. That is, the input point data is collated with the map data, and the provisional own vehicle position (temporary current position) is obtained. Next, in step P12, the vehicle speed value at that time is read from the vehicle speed sensor 4, and in step P13, the product of the input delay time data t _d and the vehicle speed value is calculated as a correction value of the point data.

Here, the time when the vehicle passes through the sign post is t ₂ in the past, and the true vehicle position (current position) corresponds to the time difference t _d from the passing point t ₂ as shown in FIG. Since the traveling distance has advanced by the distance, then in step P14, the correction value in step P13 is added to the provisional vehicle position, and the point data is corrected. Next, in step P15, the corrected spot data is output to the display / operation unit 2. As a result, the display / operation unit 2 displays the vehicle position by the mark 2c based on the spot data supplied from the controller 1.

As described above, the sign post receiver 6 of this embodiment calculates the peak time t ₂ of the radio field intensity, that is, the exact time when the signal passes through the sign post, and stores the data including the subsequent point data. The time difference from the scheduled sending time is calculated, and the data is sent to the controller 1 at the scheduled time in a format incorporating the time difference as a part of the point data. On the other hand, the controller 1 calculates the spot data corrected by the time difference. For this reason, since the vehicle position is displayed based on the data that has truly confirmed the passage of the sign post, as compared to the conventional case where just receiving the correct point data, it is regarded as the passage of the sign post. Therefore, the accuracy of the calculation of the own vehicle position, and in fact, the reliability of the display, is improved. Further, even if the steepness of the reception curve fluctuates due to the traveling speed of the own vehicle, the fluctuation has little influence on the calculation accuracy of the own vehicle position. Further, in order to specify the peak time of the radio field intensity, in this embodiment, all the ranges t _{1 to} t ₃ (though not limited to the threshold I _th or more)
The accuracy of the peak point identification is high. This makes it possible to fully utilize the auxiliary function of the sign post receiver for the GPS receiver as originally expected, and enhance the navigation function of the entire system.

By the way, when the data transmission time t ₄ is determined, the data transmission time t ₄ is calculated from the time t ₂ of the maximum radio field intensity.
_The shorter the time difference t _d up to ₄ , the more accurate the calculation can be performed. In the above embodiment, the constant time t _α is set to an appropriate value so that the high-accuracy calculation can be achieved. This is because if the time difference t _d is too large, the controller 1 is required to perform an operation in consideration of the vehicle speed change during the time difference t _d in order to maintain a constant display accuracy. This is because it becomes complicated and the calculation load increases. On the other hand, in this embodiment, an excessive increase in calculation load is suppressed.

When the time point of the maximum radio wave intensity is specified, the radio wave intensity is previously set to the threshold value I _th as in the above embodiment.
Wait until time t _{3 when the signal} reaches the maximum t
_In addition to the method of determining the point ₂ , the time t _{2 at} which the maximum field intensity is reached is determined when the field strength is relatively decreased from the peak value by a predetermined level ΔI _th (that is, without waiting for the time t ₃ ). It may be a technique.

Further, for example, a request for low power consumption,
Due to the restriction of the control operation of the device, the measured received radio wave intensity may be discrete data rather than continuous data, but the above embodiment can handle such discrete data in the same manner.

On the other hand, in the processing of step P4c of FIG. 2 (implemented by the data processing unit 6c of the sign post receiver 6) in the above-described embodiment, for example, FIG.
Modifications such as shown in are also possible. That is, the reception radio field intensity may be in a reception state with a plurality of peaks as shown in FIG. 6 due to the influence of vehicles traveling in parallel. In that case, in the process of step P4c. It suffices to perform the highest peak estimation process (see the virtual line in FIG. 6) with the learning function to identify the peak time t _z .

[0033]

As described above, in the vehicle navigation system of the present invention, the time when the sign post receiver truly passes through the sign post is first specified, and from that specified time to the subsequent data transmission to the controller. The time difference of the vehicle is sent as data, and the controller calculates the true position of the vehicle by adding the time difference at a specific point in time, and the position is displayed on the display device. Compared to the case where the receiver just receives the correct spot data and immediately sends the data to the controller, the calculation error of the vehicle position is reduced, and the calculation accuracy is greatly improved, and the reliability of the display data is improved. It is possible to provide a vehicular navigation system that can be enhanced and has enhanced functions that the sign post receiver should have.

[Brief description of drawings]

FIG. 1 is a block diagram of a sign post receiver of a vehicle navigation system according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a processing example in the sign post receiver of the embodiment.

FIG. 3 is an explanatory diagram showing a format of data sent to the controller according to the embodiment.

FIG. 4 is a graph showing an example of received radio field intensity in the example.

FIG. 5 is a flowchart showing a processing example of the controller of the embodiment.

FIG. 6 is a graph showing an example of received radio field intensity for explaining the transformation process in the sign post receiver.

FIG. 7 is a block diagram of a navigation system according to an example and a conventional example.

FIG. 8 is a block diagram of a sign post receiver according to a conventional example.

FIG. 9 is an explanatory diagram showing a format of data on the side of a sign post transmitter according to the embodiment and the conventional example.

FIG. 10 is an explanatory diagram showing a format of data sent to a controller according to a conventional example.

FIG. 11 is a flowchart showing a processing example of a conventional sign post receiver.

FIG. 12 is a view for explaining an operation timing of a conventional example,
A graph of an example of received signal strength.

[Explanation of symbols]

 1 controller 2 display / operation unit (display device) 6 sign post receiver 6a antenna 6b receiving unit 6c data processing unit 6d data output line 6e radio wave intensity measuring unit

Claims (2)

[Claims] 1. A sign post receiver that receives point information sent from fixed transmission equipment provided on a side road using radio waves as a medium, and a vehicle position based on the information received by the sign post receiver. In a vehicle-mounted navigation system comprising a controller for calculating and a display device for displaying the own vehicle position calculated by this controller, the sign post receiver, receiving means for receiving point information using the radio wave as a medium, A radio wave strength measuring means for measuring the strength of a radio wave received by the receiving means, and a maximum strength time point specifying means for specifying a time point at which the radio wave strength exhibits a maximum value based on the radio wave strength measured by the radio wave strength measuring means. When,
The time difference calculation means for calculating the time difference between the maximum strength time point specified by the maximum strength time point specifying means and the time point for transmitting the point information to be executed later, and the point information received by the receiving means and the time difference calculating means were calculated. The data creating means for creating the data with the time difference and the data sending means for sending the data created by the data creating means to the controller at the sending time are provided and sent to the controller from the data sending means. An in-vehicle navigation system comprising a vehicle position calculating means for calculating a vehicle position based on the obtained point information and time difference data. 2. The on-vehicle navigation system according to claim 1, wherein the maximum intensity time point specifying means is a means for estimating a reception time point of the maximum radio wave intensity based on a measurement result of the radio wave intensity measuring means.