JP2002296055A - Navigation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of a counter error on positioning computing in a navigation device using a counter. SOLUTION: This navigation device is provided with an antenna part 101 receiving a signal from a GNSS satellite, a positioning part 104 computing a position from the position of the satellite and a propagation time, a counter part 107 working even during a stop of operation of the navigation device, a present time computing part 109 storing a time found by the positioning computing and a counter value of the counter part 107 for computing a present time, and a transmission time computing part 105 calculating back a transmission time of the satellite by using the present time. A present time output controlling part 110 controls the present time computed by the present time computing part 109 according to a degree of the counter error to output the present time to the transmission time computing part 105.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a navigation device, and more particularly to a navigation device that obtains the position and the current time of a navigation device using signals from GNSS and geostationary satellites.

[0002]

2. Description of the Related Art As a conventional navigation device, one described in Japanese Patent Application Laid-Open No. Hei 10-170626 is known.

[0003] There are currently two global radionavigation systems in the Global Satellite Navigation System (GNSS). The Global Positioning System (GPS) consists of a group of satellites in 12 hour orbit. These satellites are operated by or for the Pentagon. Satellite navigation system (GLONASS)
Provides similar services under the control of the Russian government.

The GPS can calculate the absolute position on the earth by simultaneously receiving radio waves from a plurality of GPS satellites and acquiring navigation messages (orbit information and time information) from the GPS satellites. System.

In order to perform positioning calculation using a GPS satellite signal and calculate a position, a satellite transmission time is calculated using transmission data from the satellite, and a satellite position is calculated using the transmission time. In addition, the propagation time is calculated from the transmission time and the time of the receiver, and the positioning calculation is performed by establishing a simultaneous equation of the sphere. By the way, there are four elements to determine the transmission time of a satellite using the transmission data from the satellite.

The first is a Z counter stored in the navigation message transmitted by the satellite. The navigation message transmitted by the satellite is transmitted in a unit composed of 300 bits called a subframe, and is transmitted at a period of 6 seconds. The Z counter included in this subframe indicates the start time of the next subframe after the stored subframe. Therefore,
If a satellite is received and a subframe is analyzed, a time in units of 6 seconds can be detected.

[0007] The second is the number of bits from the head of the subframe. At the head of the subframe, an 8-bit synchronization detection pattern called a preamble pattern is stored. By detecting this preamble pattern, the head of the subframe can be detected. Here, as described above, the subframe transmits 300 bits at a cycle of 6 seconds. Therefore, by counting the number of bits of the navigation message from the beginning of the subframe, a transmission time of 20 milliseconds can be detected.

[0008] The third is the number of repetitions of the PRN code from the navigation message bit edge. The pseudo-random noise (PRN) code is a random noise having a period of 1 millisecond unique to each satellite, and a signal from the satellite can be received by despreading the same PRN code in accordance with the PRN code. Since this PRN code is repeated 20 times in one bit of the navigation message, counting the number of repetitions of the PRN code from the bit edge of the navigation message reveals the time in 1 millisecond units.

The fourth is the number of codes from the head of the PRN code. The PRN code is transmitted at 1.023 MHz, and the time in millisecond units can be obtained by converting the number of codes from the head of the despread PRN code into time.

[0010] By the way, the acquisition time of each element for acquiring the transmission time includes firstly the third and fourth elements.
Since it can be obtained by detecting a bit edge once every 0 ms, it can be obtained in a minimum of 20 ms. For the first and second elements, it is necessary to detect the preamble pattern at the head of the subframe, and since the preamble pattern is transmitted every 6 seconds, it takes at least 6 seconds to acquire. Therefore, it takes a minimum of 6 seconds to acquire all elements and determine the satellite transmission time.

Here, as one method of reducing the power consumption of the navigation device, there is intermittent reception for operating the device intermittently. Further, in order to reduce the time required for the positioning calculation and reduce the power consumption, it is required to reduce the time required for acquiring the transmission time of the satellite.

Accordingly, a counter is provided for counting up the time regardless of whether the navigation device is operating or stopped, and the current time is obtained. Further, by correcting the current time using the error amount of the past counter stored in the storage unit, calculating the propagation time of the satellite transmission signal from the current time and the satellite position information and subtracting from the current time, The transmission time fixed element is calculated backward. As a result, the transmission time can be determined in a short time. Further, the error amount of the counter can be obtained as a difference value between the current time used for calculating the transmission time and the current time obtained by performing the positioning calculation based on the calculated transmission time.

In FIG. 8 showing the configuration of a conventional navigation device, an antenna unit 1 is an antenna for receiving a radio wave from a GNSS satellite. The detection unit 2 is a unit that demodulates the radio waves of the GNSS satellite received by the antenna unit 1 and acquires data transmitted from the satellite. The positioning unit 4 is a positioning unit that calculates the position and time of the navigation device. The transmission time calculation unit 5 that calculates the transmission time of the satellite, and the positioning calculation that actually calculates the position and time from the obtained transmission time and orbit information. And 6.

The counter unit 7 is a counter constituted by a hardware circuit, and counts up with an external power supply or the like even when the navigation device is stopped. The storage unit 8 stores the correct time and position obtained by the positioning unit 4 and the counter value of the counter unit 7 corresponding to the same time. The current time calculation unit 9 adds the difference between the counter value immediately after the start of the operation stored in the storage unit 8 and the counter value stored in the storage unit to the time stored in the storage unit 8, and adds the current time. calculate. Here, the error of the counter is obtained as a difference between the current time calculated by the current time calculation unit 9 and the current time obtained by performing positioning calculation based on the satellite transmission time calculated from the current time. be able to.

[0015]

However, in such a conventional navigation device, the current time obtained by counting up and acquiring by the counter is such that even if the current time is corrected using the error of the past counter, the temperature rapidly increases. There is a problem that an error corresponding to such a change occurs when the value fluctuates. Also, among the transmission time prediction elements, only the first and second elements that require a long time to acquire are predicted,
In order to accurately predict the transmission time, the error of the counter is 2
It must be 0 ms or less than ± 10 ms.

Also, if the error of the counter is large and an incorrect transmission time is predicted for 20 ms or more, the current time is similarly obtained for the incorrect time of 20 ms or more. Even when the positioning calculation is performed, a time lag of 20 ms or more cannot be detected,
The positioning calculation result includes the effect of an error of 20 milliseconds or more in the satellite orbit calculation. Therefore, in order to perform the positioning calculation with high accuracy, it is necessary to perform the positioning calculation before an error of 20 msec or more occurs in the counter. Therefore, the receiver is intermittently received to reduce the power consumption of the receiver. Also, there is a problem that the intermittent time cannot be set long.

The present invention has been made in order to solve such a problem, and it is an object of the present invention to provide a navigation apparatus which reduces the influence of a counter error on positioning calculation.

[0018]

According to the present invention, there is provided a navigation apparatus comprising: a counting means for measuring time even when the operation of the apparatus is stopped; a transmission time calculating means for calculating a satellite transmission time; Positioning calculation means for calculating at least the position and time of the device from the propagation time obtained from the time difference of the device and the position of the satellite; and storage means for storing at least the time calculated by the positioning calculation device and the count value of the counting means. And a current time for calculating a first current time in addition to the difference between the count value of the counting means immediately after the start of the operation of the apparatus and the count value stored in the storage means, and adding the stored time to the difference. It has a configuration including a calculation unit and a current time output control unit that controls the first current time output to the transmission time calculation unit. With this configuration, the influence of the counter error on the positioning calculation can be reduced.

The navigation apparatus according to the present invention includes a geostationary satellite receiving means for receiving a signal from a geostationary satellite, and a second time calculated by adding a propagation time to the first current time and the transmission time information from the geostationary satellite. And the current time output control means controls the current time output to the transmission time calculation unit based on the comparison result. With this configuration, the current time output to the transmission time calculation means can be controlled so as to improve the accuracy of positioning, and the occurrence of a positioning error can be reduced.

In the navigation apparatus according to the present invention, the current time output control means combines a part of the first current time with a part of the second current time to obtain a current time to be output to the transmission time calculating means. Control. With this configuration, the accuracy of the positioning calculation can be improved.

Further, the navigation device of the present invention provides an absolute value of a difference value between a first current time and a third current time calculated by performing positioning calculation based on a satellite transmission time calculated from the first current time. The present time output control means controls the output of the first current time to the transmission time calculation means depending on whether the value or transition satisfies a preset condition. With this configuration, it is possible to avoid an increase in an error in the positioning calculation due to an error in the counting means.

The navigation apparatus according to the present invention further includes counter error detection means for detecting an error in the counting accuracy of the counting means with respect to the frequency of the frequency oscillator provided in the navigation apparatus. The output control means stops outputting the current time to the transmission time calculation means. With this configuration, it is possible to avoid a decrease in positioning accuracy due to an error in the counting means.

Further, the navigation device of the present invention
By operating the counter error detecting means at a constant interval, the navigation device has a configuration for detecting the count error of the counting means while the operation is stopped. With this configuration, it is possible to monitor an error of the counting unit while the navigation device is stopped.

Further, the navigation apparatus of the present invention stores the orbit information of one or more satellites in the storage means, and calculates the maximum time in which the satellite can be used for positioning calculation from the stored orbit information for each satellite. And a satellite orbit information calculating means for calculating a time required until the number of satellites usable for positioning calculation becomes less than the number required for performing positioning calculation. With this configuration, when the apparatus resumes from the temporary stop of the intermittent operation, it is possible to obtain a time during which the intermittent operation can be stopped in which the positioning calculation can be performed in a short time.

Further, the navigation device of the present invention operates the navigation device before the number of satellites available for positioning calculation calculated by the satellite orbit information calculation means falls below the number of satellites necessary for performing positioning calculation. It has a configuration provided with intermittent reception control means for restarting and reacquiring satellite orbit information. With this configuration, it is possible to reduce the power consumption of the device and perform positioning calculation in a short time.

[0026]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram showing a configuration of a navigation device according to a first embodiment of the present invention. In FIG. 1, the antenna unit 101 is a GN
Antenna for receiving signals from SS satellites, detector 102
Means for acquiring data transmitted from the satellite by demodulating the radio waves of the GNSS satellite received by the antenna unit 101 and having a plurality of channels.

The positioning unit 104 is a means for calculating the position and time of the navigation device, and includes a transmission time calculation unit 105 and a positioning calculation unit 106. The transmission time calculation unit 105 calculates the transmission time of the satellite, The operation unit 106 is a unit for calculating the position of the navigation device, the counter unit 10
7 means for counting up a periodic counter even when the operation of the navigation device is stopped, storage unit 108
Means for storing the counter value of the counter unit 107 and the time and position calculated by the positioning operation unit 106.

The current time calculation unit 109 includes a counter unit 107
Means for calculating the current time based on the counter value of the storage unit 108 and the counter value stored in the storage unit 108 and the time stored in the storage unit 108. The current time output control unit 110 Is a means for comparing the current time calculated from the transmitting means with the current time calculated by the current time calculation unit 109 to determine the current time.

Next, the operation of the navigation device according to the first embodiment of the present invention will be described with reference to FIG. The detection unit 102 demodulates the signal from the GNSS satellite received by the antenna unit 101 and transmits the signal to the transmission time calculation unit 1 of the positioning unit 104.
Output to 05. The transmission time calculation unit 105 calculates the transmission time of the target satellite based on the signal obtained by demodulating the transmission time of the GNSS satellite in the detection unit 102 or the current time controlled and compared by the current time output control unit 110 described later, and calculates the positioning time. Part 1
06 is output. The positioning calculation unit 106 includes the transmission time calculation unit 1
The position of the navigation device is calculated from the propagation time obtained from the difference between the satellite transmission time calculated at 05 and the time received by the navigation device and the satellite position information.

The counter unit 107 counts up a periodic counter even when the operation of the navigation device is stopped, and the storage unit 108 stores the counter value of the counter unit 107, the time calculated by the positioning operation unit 106, and position information. Remember. The current time calculation unit 109 stores the difference between the counter value of the counter unit 107 immediately after the navigation device starts operating and the counter value previously stored in the storage unit 108 in the storage unit 10.
By adding to the time previously stored in 8, the first current time can be obtained as shown in the following equation.

First current time = stored time + (counter value immediately after start of operation—stored counter value) Current time output control section 110 calculates the error of the first current time calculated by current time calculation section 109. Depending on the degree, control is performed such that the first current time is not output to the transmission time calculation unit 105 or is output with some correction, so that the current time having a large error is not output to the transmission time calculation unit 105, and the positioning error is calculated. Reduce outbreaks.

As described above, the navigation device according to the first embodiment of the present invention outputs the first current time acquired by the current time calculator 109 to the transmission time calculator 105 unconditionally. Instead, since the current time output control unit 110 performs appropriate control, there is an effect that occurrence of a positioning error can be reduced.

(Second Embodiment) In recent years, positioning systems using GNSS have been actively used in various fields. In the field of aircraft, the International Civil Aviation Organization (ICAO)
Has decided to introduce an aviation security system using GNSS, and to improve the safety of navigation using GNSS, the US Wide Area Augmentation System (WAAS), the European Geostationary Satellite Navigation Overlay Service (EGNOS), and Japan's multipurpose transportation A geosynchronous satellite augmentation system (SBAS) such as a satellite navigation augmentation system (MSAS) is planned.

In the SBAS, correction information obtained by distributed monitoring stations is collected in a geostationary satellite, and the geostationary satellite transmits the correction information to a mobile unit such as an aircraft. This correction information includes three types of information.

1. 1. Security (Integrity): Information indicating the certainty of the signal of the GNSS satellite. Correction data: GNSS satellite error correction information (time error correction information, orbit error correction information, ionospheric error correction information) Ranging information: G
A signal similar to the NSS signal (WAAS, EGNOS, MSAS is the same signal as GPS) is transmitted, and the geostationary satellite is transmitted to the GN.
It can be used for positioning calculation as one satellite of SS.

The above three types of SBAS systems are GP
To perform ranging by transmitting the same signal as the S satellite,
The signal transmitted by the geostationary satellite is similar to the signal transmitted by the GPS satellite in carrier frequency and modulation method. However, GP
The S satellite transmits a preamble pattern every 6 seconds,
While a 300-bit navigation message is transmitted per second, a geostationary satellite transmits a preamble pattern every second, and transmits a 250-bit message per second. Here, since the preamble pattern is at the head of the message, the head of the message can be detected by detecting the preamble pattern.

In the case of the geostationary satellite, the message is transmitted at the GPS time 1
Since transmission is performed almost in synchronization in units of seconds, detection of this preamble pattern makes it possible to detect timing synchronized with GPS time. In the case of the geostationary satellite, the amount of deviation between the timing of the geostationary satellite and the GPS time is included in the correction data. Detecting the preamble pattern and detecting the timing synchronized with the GPS time can be performed in a minimum of 1 second (250 bits / 250 bps). Also, at most about 2 seconds (493 bit / 2
50 bps).

As described above, since a geostationary satellite message transmits 250 bits in a one-second cycle, the transmission time in units of 4 milliseconds can be detected by counting the number of bits from the beginning of the message. . In addition, since the geostationary satellite is PRN-encoded with random noise having a cycle of 1 millisecond as in the case of the GPS, the time of 1 second or less can be obtained in the same manner as the GPS.

G is added to all messages transmitted by the geostationary satellite.
Since there is no time information like the PS Z counter, the satellite transmission time cannot be obtained immediately after receiving the preamble pattern, but it can be determined by receiving a message corresponding to the GPS Z counter. .

FIG. 2 is a block diagram showing a configuration of a navigation device according to a second embodiment of the present invention. 2, the configuration from the antenna unit 101 to the detection unit 102 and the configuration from the positioning unit 104 to the current time calculation unit 109 are the same as those of the first embodiment shown in FIG. Detailed description is omitted. The difference is that the geostationary satellite receiver 103 and the current time output controller 1
11, a geostationary satellite receiving unit 103 is a receiving unit that receives a transmission signal from a geostationary satellite via an antenna 101, and includes a transmission time calculation unit 105 and a current time output control unit 1.
11 is output. The current time output control unit 111 uses the current time calculated by the current time calculation unit 109 to calculate the current time.
The output to the transmission time calculation unit 105 is controlled based on the current time received in step 3.

Next, the operation of the navigation device according to the second embodiment of the present invention will be described with reference to FIG. The detection unit 102 demodulates the signal from the GNSS satellite received by the antenna unit 101 and transmits the signal to the transmission time calculation unit 1 of the positioning unit 104.
Output to 05. The geostationary satellite receiver 103 is the antenna unit 1
01 and demodulates the signal from the geostationary satellite received by the positioning unit 1
04 transmission time calculation unit 105 and current time output control unit 11
Output to 1.

The transmission time calculation unit 105 calculates the transmission time of the GNSS satellite and the geostationary satellite based on the signal demodulated by the detection unit 102 or the geostationary satellite reception unit 103 or the current time selected by the current time output control unit 111 described later. The transmission time of the target satellite is calculated and output to the positioning calculation unit 106. The positioning calculation unit 106 calculates the position of the navigation device from the propagation time obtained from the difference between the satellite transmission time calculated by the transmission time calculation unit 105 and the time received by the navigation device and the satellite position information.

The counter unit 107 counts up a periodic counter even when the operation of the navigation device is stopped, and the storage unit 108 stores the counter value of the counter unit 107, the time calculated by the positioning operation unit 106, and position information. Remember. The current time calculation unit 109 stores the difference between the counter value of the counter unit 107 immediately after the navigation device starts operating and the counter value previously stored in the storage unit 108 in the storage unit 10.
By adding to the time previously stored in 8, the first current time can be obtained as shown in the following equation.

First current time = stored time + (counter value immediately after start of operation−stored counter value) The current time output control unit 111 transmits the geostationary satellite By adding the propagation times, the second current time can be obtained as shown in the following equation.

The second current time = the transmission time of the geostationary satellite + the propagation time of the geostationary satellite The current time output control unit 111 sets the transmission time of the geostationary satellite obtained by receiving the geostationary satellite to 1 second or less.
And the second current time obtained by adding the propagation time of the geostationary satellite, and the current time calculation unit 109.
The first current time calculated in step 1 is compared with the time of 1 second or less, and if the difference is large, the first current time using the value of the counter is determined to have a large error. The time output control unit 111 controls so that the current time calculated by the current time calculation unit 109 is not output to the transmission time calculation unit 105, and reduces the occurrence of a positioning error.

Here, the first current time is counted by the counter 1
07, and the second current time includes an error in the propagation time of the geostationary satellite. The cause of the error in the propagation time of the geostationary satellite is as follows. Delays due to the effects of the ionosphere and the atmosphere before geostationary satellite transmission data reaches the Earth's surface,
2. There are two types of errors: the position of the geostationary satellite used to determine the propagation time and the error in the temporary position of the navigation device. Here, the influence of the first element is an error of the order of several microseconds until the transmission data from the GPS satellite reaches the earth's surface, and the same error as the delay amount of the geostationary satellite. Therefore, it can be said that it is extremely smaller than the error of the counter described in the subject.

On the other hand, with respect to the second element, first, the geostationary satellite is designed so as to always stay in the same geostationary orbit, so that a large error does not occur in the position of the geostationary satellite. However, there is a possibility that an error occurs in calculating the temporary position of the navigation device. For example, if the temporary position of the navigation device is the location where the navigation device has performed the last positioning calculation, the amount of movement of the navigation device since the last time the positioning calculation was performed occurs as an error. If the vehicle travels several thousand km after the previous positioning calculation, a large error naturally occurs in the calculation of the propagation time of the geostationary satellite.

If a large error occurs in the calculation of the provisional position of the navigation device, it is natural that G other than the geostationary satellite is used.
A large error also occurs in the calculation of the propagation time of the NSS satellite. Therefore, an error occurs in the satellite transmission time calculated by calculating the current time by the counter and subtracting the propagation time from the current time. In such a case, when the positioning calculation is performed, since the position of the satellite is calculated from the transmission time of the satellite including the error, an error occurs in the position calculation of the orbiting satellite such as GPS, and the result of the positioning calculation is obtained. There will be an error between the current position and the current position.

Here, in the case where the time of 20 ms or more in the GPS transmission time is calculated backward from the counter,
About 6000 km (≒ 20 ms × speed of light) When an error occurs in the temporary position of the navigation device, a deviation occurs. In a positioning system using satellites, the range in which positioning can be performed is limited to the range in which satellite transmission signals can be received.

Here, the diameter of the earth is about 13,000 km, and the satellite altitude (GPS: about 26,000 km above the ground)
m, geosynchronous satellite: about 36000 km), the upper limit of the error generated in the calculation of the temporary position of the navigation device is tens of thousands km. Even if you move from the 0 ° north latitude to the 0 ° south latitude, the diameter of the earth is about 13,000k
m, the error in the propagation time is at most 1300
It is about 40 milliseconds obtained by dividing 0 km by the speed of light.

Since the time of one second or less of the transmission time of the geostationary satellite can be accurately obtained from the transmission signal of the geostationary satellite, the current time calculated by adding the propagation time to the transmission time includes the propagation time. Only the error of the provisional position of the navigation device included in the above is included. Even if an error occurs in the calculation of the temporary position of the navigation device, the storage unit 1
The difference between the counter value stored in the storage unit 108 immediately after the start of the operation and the counter value stored in the storage unit 108 is stored in the storage unit 108.
Does not affect the current time calculated by adding the time stored in the temporary position of the navigation device.

Therefore, if the difference between the current time calculated from the counter value and the current time calculated by adding the propagation time to the transmission time of the geostationary satellite is taken, it is possible to detect a temporary position error of the navigation device. It is. An error occurs in the provisional position of the navigation device when the device has moved several thousand km since the previous positioning calculation was performed. for that reason,
In an environment such as intermittent reception in which positioning calculation is performed again after a predetermined time from the previous positioning calculation, the device does not move significantly.

When the range can be used as described above, there is no error in the second current time calculated by adding the propagation time to the transmission time of the geostationary satellite. Therefore,
If there is a difference between the second current time and the first current time calculated from the counter value, this is because the counter 107
It can be said that this is an error.

As described above, the navigation device according to the second embodiment of the present invention, when the difference between the current time obtained from the transmission data of the geostationary satellite and the current time calculated by the counter is large, It is determined that the error of the counter is large, and the current time output control unit 111 uses the current time calculated by the current time calculation unit 109 as the transmission time calculation unit 1
By switching the output so as not to output it to 05, there is an effect that the occurrence of a positioning error is reduced.

In the above embodiment, the difference between the counter value of the counter unit 107 immediately after the navigation device starts operating and the counter value previously stored in the storage unit 108 is stored in the storage unit 108 as the first current time. Described in the case where it can be obtained by adding to the time stored in
The present invention is not limited to this case, and a similar effect can be obtained even if a correction is made by an update error of the counter value as in the following equation.

First current time = stored time + (counter value immediately after start of operation−stored counter value) − (counter value immediately after start of operation−stored counter value) × counter value update error (third embodiment) Embodiment) FIG. 2 is also a block diagram showing a configuration of a navigation device according to a third embodiment of the present invention. In FIG. 2, the present embodiment is different from the second embodiment in the configuration of the current time output control unit 110.
If the transmission time of the geostationary satellite is less than 1 second,
The time of one second or less of the first current time calculated by the current time calculation unit 109 is replaced with a part of one second or less of the second current time.

Next, the operation of the thus configured navigation device of the present embodiment will be described. The current time determination unit 111 adds the propagation time to the geostationary satellite signal received by the geostationary satellite reception unit 103 to determine the second current time of one second or less, and calculates the first current time calculated by the current time calculation unit 109. Is output to the transmission time calculation unit 105 in which the current time in the unit of one second or less is replaced with the second current time. The transmission time calculation unit 105 is a current time determination unit 111
The positioning calculation is performed by predicting the satellite transmission time based on the received combined current time.

As a result, even if an error occurs in the counter unit 107, the transmission time of the geostationary satellite in units of one second or less is one.
Since it can be acquired in about a second, the counter unit 1
07 can be eliminated. Since the transmission time of the geostationary satellite can be obtained in a short time of about 1 second, the positioning calculation may not be performed until the transmission time of the geostationary satellite is obtained. However, in this case, since it is not always possible to receive the transmission data of the geostationary satellite, such as when there is an obstacle in the vicinity, if the signal from the geostationary satellite cannot be received even after several seconds, the GNSS Processing such as restarting the positioning calculation by the satellite is required.

As described above, the navigation device according to the third embodiment of the present invention comprises a counter 10
The current time calculated by (7) is a time of one second or more. The current time of one second or less is calculated by a signal from a geostationary satellite, and the current time is determined by combining them. The accuracy of the output current time can be improved, and as a result, the accuracy of the positioning calculation can be improved. Counter unit 1
Since an error of up to 1 second can be allowed for 07, even if the navigation device is operated intermittently to reduce the power consumption of the navigation device, the intermittent time can be set long. It also has the effect that

(Fourth Embodiment) FIG. 3 is a block diagram showing a configuration of a navigation device according to a fourth embodiment of the present invention. In FIG. 3, the configuration from the antenna unit 101 to the current time calculation unit 109 is the same as the configuration and operation and effect of the second and third embodiments shown in FIG. The difference is the function of the current time comparison and determination unit 140, which determines whether to calculate the satellite transmission time using the counter based on the absolute amount or transition amount of the error of the past counter.

Next, the operation of the thus configured navigation apparatus of the present embodiment will be described. In FIG. 3, a current time calculation unit 109 obtains the current time with the counter of the counter unit 107, and further corrects the error with a past counter stored in the storage unit 108 to calculate an accurate current time. However, as described in the conventional navigation device, if the temperature fluctuates rapidly, an error may occur in the calculated current time. If the error included in the calculated current time is large, an error occurs in the satellite transmission time calculated from the current time. Here, when the error of the counter is large and an error occurs in the calculation of the current time and the transmission time of the satellite, an error also occurs in the current time calculated by the positioning calculation, and the error of the counter at this time is accurately obtained. I can't do it. Therefore, after this time, since the past counter error data becomes inaccurate, the time cannot be accurately calculated by the counter.

As described in the conventional navigation apparatus, if only the time of 6 seconds or more of the satellite transmission time and the time in units of 20 milliseconds are predicted, the error of the counter is 20 milliseconds, that is, ± 10 millimeters. Up to a second error is acceptable. Here, a case is considered in which, for example, a current time that is more accurate by +15 milliseconds than the current time calculated using the counter and corrected by the error of the counter is predicted. In this case, an error of +20 milliseconds occurs in the time of the satellite transmission time in units of 20 milliseconds, and the current time calculated by performing the positioning calculation using the transmission time of the satellite is also +20.
A millisecond error will result. Therefore, although the counter actually has an error of +15 ms, the error of the counter to be detected is -5 ms (15 ms−20 ms).
(Millisecond = −5 millisecond). After that, when the current time is corrected using the error of the counter, the counter is actually corrected, assuming that the counter has a tendency to be delayed rather than the actual time being advanced. However, the current time is corrected in a direction in which it advances further than the actual time advance. As a result, if the current time is incorrectly calculated by the counter, the subsequent prediction cannot be performed accurately.

When the prediction cannot be performed accurately, the error of the counter to be detected is also expected to vary. Therefore, when the variation of the error of the counter is large, the error It can be determined that there is. Therefore, in order to detect the degree of variation of the counter error, the current time is calculated from the counter, and the current time calculated by correcting with the error of the past counter, and the satellite transmission time is calculated based on the current time. And the current time obtained by performing the positioning calculation and storing it in the storage unit. As a result, the error of the counter can be detected as a difference value between the two current times.

In the next and subsequent positioning calculations, the two current times are similarly stored and the error of the counter is detected. In this way, the degree of variation of the counter error can be detected from the transition of the counter error. In order to determine whether or not the transmission time can be accurately predicted from the variation in the counter error obtained in this way, for example, the accuracy of the counter is checked in advance, and the allowable maximum amount of the counter error is determined. Keep it. After that, calculate the difference between the counter error detected by performing the positioning calculation and the error of the counter at the time of the previous positioning calculation, and if this difference is equal to or greater than the maximum allowable counter error, accurately predict the transmission time. The current time comparison and determination unit 140 determines that the current time has not been calculated, and the current time calculated by the current time
Stop outputting to 5.

As described above, the navigation device according to the fourth embodiment of the present invention has a
Is determined based on the difference between the previous time of the current time comparison and determination unit 140 and the time obtained by performing the positioning calculation based on the time, and the current time of the current time comparison and determination unit 140 and the time based on the time. If the difference from the time obtained by performing the calculation is large, the configuration is such that the transmission time of the satellite is not calculated by the counter, thereby preventing the prediction of the current time thereafter from being unable to be performed accurately. it can.

In the above embodiment, the difference between the two current times at the time of the previous positioning calculation and the difference between the two current times at the current positioning calculation is calculated, and this difference is equal to or greater than the allowable maximum amount of the counter error. In the case described above, the case where the calculation of the satellite transmission time is not performed by the counter is described, but the present invention is not limited to this method.For example, even if the difference between the previous time and the current time is within the allowable maximum amount range, If the transition alternates in the positive and negative directions and exceeds the variation tolerance set separately, it is determined that the transmission time cannot be accurately predicted. The current time calculated by the calculation unit 109 is used as the transmission time calculation unit 10
The same effect can be obtained by stopping the output to the fifth output.

(Fifth Embodiment) FIG. 4 is a block diagram showing a configuration of a navigation device according to a fifth embodiment of the present invention. 4, the configuration from the antenna unit 101 to the current time comparison and determination unit 140 is the same as the configuration and operation and effect of the fourth embodiment shown in FIG. 3, and a detailed description thereof will be omitted. The difference is the configuration of the counter error detection unit 150, which is a frequency of a frequency oscillator that counts up the counter unit 107 with respect to a frequency of a high-precision frequency oscillator such as a TCXO provided for the navigation device to perform detection. Is detected.

Next, the operation of the thus configured navigation device of the present embodiment will be described. In FIG. 4, the counter error detection unit 150 is a counter 107
This is a means for detecting a difference between the frequency of the crystal oscillator described above and the frequency of a high-precision frequency oscillator such as TCXO provided for the navigation device to perform detection. Here, the difference between the two frequencies can be detected by counting up the fixed interval counter by the frequency oscillator of the counter unit 107 and simultaneously counting the number of clocks of the high-precision frequency oscillator at the fixed interval.

The navigation device performs satellite acquisition, TC
Since the operation is performed based on the frequency of a temperature-compensated high-precision frequency oscillator such as XO, the frequency oscillator is always operating while the receiver is operating. Data is transmitted from a GPS satellite on a carrier of 1.57542 GHz. Further, due to the Doppler effect accompanying the movement of the satellite, the frequency changes up to about ± 5000 Hz. G
Generally, a PS receiver uses a temperature compensated frequency oscillator, and its error is several ppm. For example, when there is an error of 3 ppm, the frequency conversion is about ± 5000 Hz.

As a result, 1.5 is required to receive the satellite.
It is considered that the frequency changes in a range of ± 10000 Hz centering on 7542 GHz. Therefore, when receiving satellites,
The satellite position is calculated from the orbit information and the approximate time of the backed-up navigation message, the satellite that can be received from the position of the navigation device and the frequency offset due to the Doppler effect of the satellite are estimated, and the offset frequency is centered on that frequency. Scan area and receive satellites. That is,
When the satellites are synchronized, an error of the frequency oscillator can be obtained, so that the error of the frequency oscillator is always corrected.

Since a high-precision frequency transmitter with temperature compensation such as TCXO consumes a large amount of power, the counter 107 which operates even when the operation of the receiving function unit is stopped is supplied to the counter unit 107. When a large counter is used, the effect of reducing the power consumption of the navigation device by performing intermittent reception is diminished. Therefore, a low-precision frequency oscillator that does not perform temperature compensation is often used for the counter unit 107.

While the receiving function part is operating, TCX
Two high-precision frequency oscillators using O or the like and a relatively low-precision frequency oscillator of the counter unit 107 operate. Here, since the frequency oscillator operates with the clock of the crystal oscillator, the oscillation frequency varies depending on the temperature. The error of the frequency oscillator at each temperature can be known by checking the specifications of the crystal oscillator in advance.

Generally, the temperature characteristics of a frequency transmitter are as follows:
It is designed to minimize errors at room temperature. Therefore, if the frequency difference between the frequency oscillators at room temperature is obtained in advance, it is possible to detect the temperature change from room temperature by obtaining the frequency difference between the two frequency oscillators by the counter error detection unit 150 thereafter. Become. When the temperature change from the normal temperature is large, the counter 1 does not perform the temperature compensation.
07 increases. The counter error detection unit 150 monitors the error of the counter unit 107, and when the error becomes equal to or greater than a certain value, the current time calculation unit 109 sets the counter unit 1
The current time at the time of rising using the counter value of 07 is not calculated, and the current time comparison determination unit 140 does not output the current time to the transmission time calculation unit 105.

As described above, the navigation device according to the fifth embodiment of the present invention detects an error in the frequency of the frequency oscillator counted up by the counter unit 107 by comparing with the frequency of the high-precision frequency oscillator. If the current time calculation unit 109 determines that the error of the counter is large when calculating the rising time based on the counter value of the counter unit, the current time calculation unit 109 calculates the current time using the counter value. By not performing the calculation and not outputting the current time from the current time comparison / determination section 140 to the transmission time calculation section 105, there is an effect that a decrease in positioning accuracy can be avoided.

In the above embodiment, the case where the TCXO provided for the navigation device to perform the detection as the high-precision frequency oscillator has been described. However, the present invention is not limited to the TCXO for the detection. For TCX applications
The same effect can be obtained with a temperature-compensated crystal oscillator of a type other than O, TCXO, or a high-precision oscillator other than a crystal.

(Sixth Embodiment) FIG. 5 is a block diagram showing a configuration of a navigation device according to a sixth embodiment of the present invention. 5, the configuration from the antenna unit 101 to the counter unit 107, the configuration from the current time calculation unit 109 to the display unit 120, and the configuration from the current time comparison determination unit 140 to the counter error detection unit 150 are the same as those of the fifth embodiment shown in FIG. Therefore, detailed description is omitted. The different point is the functions of the positioning unit 112, the intermittent reception control unit 160, and the storage unit 170. The intermittent reception control unit 160 controls the power supply of the part performing the intermittent reception of the navigation device, the storage unit 170 Is a storage unit to which a function of storing the error of the counter unit calculated by the counter error detection unit 150 is added to the storage unit 108 of the fifth embodiment shown in FIG.

Next, the operation of the thus configured navigation device of the present embodiment will be described. In FIG. 5, the intermittent reception control unit 160 periodically restarts a part of the operation of the reception function part even when the reception function part performs intermittent reception and stops operation. Is performed at regular intervals.

When the receiving function part has restarted all the operations for performing the positioning calculation, when the current time calculating section 109 uses the counter value of the counter section 107 to determine the time at the time of rising, the storage section 170 Counter 107 while the receiving function part stored in the
The error of the counter 107 is corrected by subtracting the error of the counter 107 from the time at the time of rising.

As described above, according to the sixth embodiment, even when the intermittent reception is performed and the operation of the receiver is stopped for a long time, the error of the counter unit is detected at regular intervals. This has the effect that the effect of the counter error can be reduced.

(Seventh Embodiment) FIG. 6 is a block diagram showing a configuration of a navigation device according to a seventh embodiment of the present invention. 6, the configuration from the antenna unit 101 to the geostationary satellite receiving unit 103 and the configuration from the transmission time calculation unit 105 to the current time determination unit 111 are the same as those of the second and third embodiments shown in FIG. Therefore, detailed description is omitted. The difference is that the positioning unit 112, the satellite orbit information calculation unit 113, and the display unit 1
20, the positioning unit 112 includes a transmission time calculation unit 109, a positioning calculation unit 106, and a satellite orbit information calculation unit 113.
The satellite orbit information calculation unit 113 stores the
This is a means for acquiring the effective time of the satellite orbit information from the satellite orbit information stored in 08. The display unit 120 is a means for presenting the effective time of the satellite orbit information acquired by the satellite orbit information calculation unit 113 to the user.

Next, the operation of the thus configured navigation apparatus of the present embodiment will be described. In FIG. 6, in order to perform positioning calculation, it is necessary to calculate a satellite position using satellite orbit information. Here, the satellite orbit information is included in the navigation message transmitted from the GPS satellite. As described above, the navigation message of the GPS satellite is transmitted in the form of a subframe every 6 seconds.

Further, there are five types of subframes, and the GPS satellite sequentially transmits these five subframes. Here, the satellite orbit information is stored in two of the five subframes, and requires a minimum of 7.5 seconds to acquire, and usually takes several tens of seconds. In addition, each satellite orbit information has a valid time set. If intermittent reception is performed and the intermittent time exceeds the valid time of the satellite orbit information, the satellite orbit information of the satellite can be used. Instead, it becomes necessary to obtain satellite orbit information again.

Further, since the GPS satellites orbit the earth, the same applies when the GPS satellites cannot be found in the sky. Therefore, the number of valid satellite orbital information decreases as the power of the navigation device is turned off during intermittent reception for a long time, and the number of valid satellite orbital information is required for positioning calculation when operation resumes. If the number of satellite orbits falls below a certain number, it is necessary to obtain satellite orbit information again, so that positioning calculation cannot be performed for several tens of seconds until the required number of satellite orbits is secured.

The satellite orbit information calculation unit 113 first obtains the effective time of the orbit information from the orbit information of each satellite stored in the storage unit 108. Next, at the latest position of the navigation device obtained by performing the positioning calculation last, the time until the satellite no longer exists in the sky is calculated from the satellite orbit information. The shorter one of the two calculated times is regarded as the valid time of the satellite.
This calculation is performed for all the satellites for which the satellite orbit information is acquired, a time in which the number of satellites is less than the minimum number required for performing positioning calculation is calculated from the effective time, and this time is displayed to the user by the display unit 120. Inform.

As described above, the navigation device according to the seventh embodiment of the present invention can notify the user of the maximum time during which the operation of the device capable of performing the positioning calculation in a short time can be stopped. Has an effect.

(Eighth Embodiment) FIG. 7 is a block diagram showing a configuration of a navigation device according to an eighth embodiment of the present invention. 7, the configuration from the antenna unit 101 to the display unit 120 is the same as that of the seventh embodiment shown in FIG. 6, and the detailed description is omitted. A different point is the function of the intermittent reception control unit 130. Based on the calculation result of the satellite orbit information calculation unit 113, the intermittent reception control unit 130 performs the intermittent reception operation of the navigation device (hereinafter referred to as the reception function part). Control) power supply.

Next, the operation of the thus configured navigation apparatus of the present embodiment will be described. In FIG. 7, before the time at which the number of valid satellite orbit information calculated by the satellite orbit information calculation unit 113 falls below the minimum number required for performing positioning calculation is reached, the intermittent reception control unit 130 controls the reception function of the navigation device. Power on the part. Further, the satellite orbit information is acquired and the satellite orbit information calculation unit 113 is obtained.
The power is turned on until the intermittent time, which can perform the positioning calculation calculated in the above in a short time, is sufficiently long.

As described above, in the navigation apparatus according to the eighth embodiment of the present invention, the number of valid satellite orbit information is calculated by the intermittent reception control unit 130 using the calculation result of the satellite orbit information calculation unit 113. Since the intermittent reception control unit 130 turns on the power of the reception function part of the navigation device before the time less than the minimum number required for performing the positioning, the positioning calculation can be performed in a short time when the positioning is restarted. Has an effect.

[0090]

As described above, according to the present invention, the accuracy of the positioning calculation is improved by controlling the current time output to the transmission time calculating unit based on the rising time obtained by the counter. It is possible to provide a navigation device having an excellent effect.

Further, according to the present invention, not only signals from geostationary satellites but also geostationary satellites are received, the transmission time of the geostationary satellite is obtained, and the propagation time of the geostationary satellite is added to calculate the start time. Then, by comparing the rising time obtained by the counter with the rising time, and controlling the current time output by the current time output control means to the transmission time calculation unit based on the result, the accuracy of the positioning calculation is improved. It is possible to provide a navigation device having an advantageous effect.

Further, according to the present invention, the current time output control means calculates the sum of a part of the first current time at the time of rising obtained by the counter and the transmission time of the geostationary satellite by adding the propagation time of the geostationary satellite. By determining the current time to be output to the transmission time calculating means in combination with a part of the current time of No. 2 above, it is possible to provide a navigation device having an excellent effect that the accuracy of positioning calculation can be improved. Things.

Further, according to the present invention, the information is stored in the storage unit.
The difference between the first current time calculated by the current time calculation means and the third current time acquired as a result of the positioning calculation is calculated, and the first time from which the satellite transmission time is calculated based on the difference is calculated.
The error amount included in the current time is determined, and if the error amount is large, the current time output control means stops outputting the first current time to the transmission time calculation means. It is possible to provide a navigation device having an excellent effect that it is possible to avoid the problem.

Further, according to the present invention, the accuracy of the counting means is
By acquiring by comparing with the frequency of the high-precision frequency oscillator of the navigation device, when the error of the counting means is larger than a preset value, the counting time is not calculated by the counting means. Further, it is possible to provide a navigation device having an excellent effect that a decrease in positioning accuracy due to an error in the counting means can be avoided.

Further, according to the present invention, even when the operation of the navigation device is stopped, the operation of the counter error detection device is performed at a constant interval to detect the count error of the counting device, so that the navigation device operates. It is possible to provide a navigation device having an excellent effect that an error of a counter when the operation of the navigation device is stopped can be monitored even when the navigation device is stopped for a long time.

Further, the present invention calculates the time until the number of satellite orbit information held when intermittent reception is performed and the navigation apparatus resumes operation is less than the minimum number required for performing positioning calculation. With the configuration including the satellite orbit information calculation means, it is possible to provide a navigation device having an excellent effect of being able to know the maximum intermittent time in which positioning calculation can be performed in a short time.

Further, according to the present invention, the operation of the navigation device is intermittently stopped, and the operation of the receiver is restarted before the number of held satellite orbit information falls below the minimum number necessary for performing positioning calculation. By providing the intermittent reception control means for reacquiring satellite orbit information, it is possible to provide a navigation device having an excellent effect that positioning calculation can be performed in a short time.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a navigation device according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a navigation device according to second and third embodiments of the present invention.

FIG. 3 is a block diagram showing a configuration of a navigation device according to a fourth embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of a navigation device according to a fifth embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a navigation device according to a sixth embodiment of the present invention.

FIG. 6 is a block diagram showing a configuration of a navigation device according to a seventh embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of a navigation device according to an eighth embodiment of the present invention.

FIG. 8 is a block diagram showing a configuration of a conventional navigation device.

[Explanation of symbols]

 103 geostationary satellite receiving unit 104, 112 positioning unit 105 transmission time calculation unit 106 positioning calculation unit 107 counter unit 108, 170 storage unit 109 current time calculation unit 110, 111, 140 current time output control unit 113 satellite orbit information calculation unit 120 display Section 130, 160 intermittent reception control section 150 counter error detection section

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F029 AA02 AB07 AC02 AC06 AC20 AD01 5J062 AA05 AA13 BB01 CC07

Claims (8)

[Claims] 1. A counting means for measuring time even when the operation of the apparatus is stopped, a transmission time calculating means for calculating a transmission time of a satellite, and a propagation time obtained from a difference between the transmission time and the time of the apparatus. Positioning calculation means for calculating at least the position and time of the apparatus from the position of the satellite, and storage means for storing at least the time and the count value of the counting means calculated by the positioning calculation means; and Current time calculation means for calculating a difference between the count value of the counting means and the count value stored in the storage means, and calculating a first current time in addition to the time at which the difference is stored; A current time output control means for controlling the first current time outputted to the transmission time calculation section. 2. A geostationary satellite receiving means for receiving a signal from a geostationary satellite, comprising: a first current time and a second current time calculated by adding a propagation time to transmission time information from the geostationary satellite. Wherein the current time output control means controls the current time output to the transmission time calculation unit based on the comparison result. 3. The current time output control means performs control so that a part of the first current time is combined with a part of the second current time to obtain a current time to be output to the transmission time calculation means. 3. The navigation device according to claim 2, wherein: 4. An absolute value or a transition of a difference value between the first current time and a third current time calculated by performing positioning calculation based on a satellite transmission time calculated from the first current time is determined in advance. 2. The navigation device according to claim 1, wherein the current time output control means controls the output of the first current time to the transmission time calculation means depending on whether or not a set condition is satisfied. 5. A counter error detecting means for detecting an error in the counting accuracy of said counting means with respect to the frequency of a frequency oscillator provided in a navigation device, wherein said current time output controlling means is provided when said error becomes a predetermined value or more. 2. The navigation device according to claim 1, wherein output of a current time to said transmission time calculating means is stopped. 6. The navigation apparatus according to claim 5, wherein the counter error detection means is operated at regular intervals to detect a count error of the counting means while the navigation apparatus is stopped. 7. The orbital information of one or more of the satellites is stored in the storage means, and the maximum time in which the satellite can be used for positioning calculation is calculated for each satellite from the stored orbital information. 2. A satellite orbit information calculating means for calculating a time required until the number of satellites usable for calculation falls below a number necessary for performing positioning calculation.
The navigation device according to any one of claims 1 to 6. 8. The operation of the navigation apparatus is resumed before the number of satellites available for positioning calculation calculated by the satellite orbit information calculation means falls below the number of satellites necessary for performing positioning calculation. 8. The navigation device according to claim 7, further comprising intermittent reception control means for reacquiring the information.