JP4924017B2 - Position detection apparatus and position detection method - Google Patents

Description

  The present invention relates to a position detection device and a position detection method using GPS, and more particularly to a position detection device and a position detection method for detecting a current position by receiving radio waves from a satellite.

  A GPS (Global Positioning System) is a system that receives radio waves from a plurality of satellites and detects a current position. The satellites in this case are not geostationary satellites, but 32 satellites that orbit the altitude of 20,000 km and change their positions with respect to the earth. In order to detect the current position, it is necessary to receive GPS signals from at least three of the 32 satellites. Actually, GPS signals are received from four satellites to detect the current position. A 30-second mainframe is transmitted from each satellite. This main frame is composed of 5 subframes each having 6 seconds, and each subframe is composed of 300-bit data. Among the first to fifth subframes, the first subframe includes the state and clock correction coefficient of each satellite, and the second and third subframes include orbit information of each satellite. “Ephemeris” is stored, and “almanac”, which is general orbit information common to all 32 satellites, is stored in the fourth and fifth subframes.

Many proposals have been made regarding position detection technology using GPS.
For example, in a proposed GPS navigation apparatus, ephemeris data is divided and collected in units of subframes and stored in a memory, thereby shortening the time required for data collection. Specifically, a subframe collection flag is provided, and this flag is set to 1 (valid) according to the collection of the subframe. Therefore, since it is determined by the flag whether or not the subframe has been collected once, it is not necessary to collect the subframe again, and the collection time can be shortened. (See Patent Document 1)
Further, in a proposed GPS receiver, a detection unit having a plurality of channels, a message collection unit that collects a navigation message transmitted from a satellite demodulated by the detection unit, a message analysis unit that analyzes the collected message, A positioning unit that calculates the position of the receiver from the propagation time and the position of the satellite, and a timing designating unit that designates a timing for scanning the navigation message for the message collection unit of each channel, and a navigation message in one or more channels When collecting messages, specify the message collection timing for other channels. Therefore, by quickly detecting a preamble pattern that is a bit pattern indicating the head of a navigation message transmitted from a GPS satellite, reducing the time to detect a preamble pattern in all channels, and quickly collecting navigation messages, Reduce positioning time. (See Patent Document 2)
In addition, in a proposed GPS receiver, GPS satellites can be captured in a plurality of channels, time information extracted from satellite data from the captured GPS satellites, and current time measured on the GPS receiver side Based on the time, the distance between the GPS satellite and the current position (the position of the GPS receiver) is measured. Further, the detailed orbit information (ephemeris) included in the satellite data is taken out, the satellite position is calculated, and the position of the GPS receiver is calculated in consideration of the measured distance. As a result, synchronization with the satellite data can be established at an early stage, and the time required to start positioning is shortened. (See Patent Document 3)
In a proposed position detection device, data from GPS satellites received by a GPS receiver has a hierarchical structure of mainframe, subframe, and word, and a parity bit for checking is incorporated in each word check. Therefore, the GPS receiver performs a parity bit for each word and outputs how many words are MG in the parity check in the received subframe. The reception determination unit determines whether data reception is possible based on the number of parity checks MG. When it is determined that data cannot be received, the control unit turns off continuous energization for data collection, turns on the switch for data collection again after a predetermined time, and energizes the main power supply. As a result, when continuous energization is performed in order to acquire satellite orbit information, it takes a long time to collect data if the reception environment is bad, thereby avoiding unnecessary power consumption. (See Patent Document 4)
Japanese Patent Publication No. 3-42793 Japanese Patent Laid-Open No. 11-304899 JP 2000-292521 A JP 2003-194910 A

In the conventional position detection using the GPS including the above-described Patent Documents 1 to 4, the first to fifth subframes are continuously acquired. Since the five subframes are 30 seconds, if the margins before and after are included, the time for continuous energization needs 40 seconds or more. However, in the case of the wristwatch position detection device of FIG. 7 using a coin-type battery or other portable position detection device, when a coin-type battery is used as a power source for supplying power to each part, 40 seconds. If the current is continuously applied, the discharge characteristics of the battery deteriorate, and the device itself may stop functioning due to a significant voltage drop of the battery.
The present invention is to solve such a conventional problem, and even when a coin-type battery or other small battery is used as a power source, a wasteful power consumption is avoided and a significant voltage drop of the battery is achieved. An object of the present invention is to make it possible to reliably receive a GPS signal from a satellite and detect the current position without causing a situation in which the function of the apparatus is stopped due to the occurrence of an error.

The position detection device according to claim 1 is:
A time measuring means for measuring the current time;
Receiving means for receiving a navigation message transmitted from a satellite;
In response to a pre-measurement instruction of the current position, the reception unit is operated for a predetermined time, and an offset from when the reception unit is in an operating state until the subframe included in the navigation message can be stably received. Offset time measuring means for measuring time;
After the measurement of the offset time, a first subframe acquisition unit that acquires a subframe while the reception unit is in an operating state, and acquires a start time of the received subframe and a subframe number; ,
Unacquired subframe number detecting means for detecting the number of unacquired subframes based on the subframe number obtained by the first subframe obtaining means;
When a measurement instruction is given after the preliminary measurement, the current time measured by the time measuring unit, the offset time measured by the offset time measuring unit, and the first subframe acquisition unit Based on the subframe start time and the subframe number, and the unacquired subframe number detected by the unacquired subframe number detection means, the receiving means for obtaining the unacquired subframe. Time calculating means for calculating the time to set the operation state,
Second subframe acquisition means for operating the reception means at the time calculated by the time calculation means to acquire the unacquired subframe;
Current position calculation means for calculating a current position based on the subframes acquired by the first subframe acquisition means and the second subframe acquisition means;
It is provided with.

The position detection method according to claim 2 comprises:
A position detecting method for a position detecting device, comprising a time measuring means for measuring a current time and a receiving means for receiving a navigation message transmitted from a satellite,
In response to a pre-measurement instruction of the current position, the reception unit is operated for a predetermined time, and an offset from when the reception unit is in an operating state until the subframe included in the navigation message can be stably received. An offset time measurement step for measuring time;
After the measurement of the offset time, a first subframe acquisition step of acquiring a subframe while the receiving unit is in an operating state, and acquiring a start time of the received subframe and a subframe number; ,
An unacquired subframe number detection step of detecting an unacquired subframe number from the subframe number obtained in the first subframe acquisition step;
When a measurement instruction is given after the preliminary measurement, the current time measured by the time measuring means, the offset time measured by the offset time measurement step, and the first subframe acquisition step are acquired. The receiving means for acquiring the unacquired subframe based on the subframe start time and the subframe number and the unacquired subframe number detected by the unacquired subframe number detection step. A time calculating step for calculating the time to set the operation state,
A second subframe acquisition step of operating the receiving means at the time calculated by the time calculation step to acquire the unacquired subframe;
A current position calculating step for calculating a current position based on the subframes acquired in the first subframe acquisition step and the second subframe acquisition step;
It is characterized by performing.

  According to the present invention, even when a coin-type battery or other small battery is used as a power source, useless power consumption is avoided, and a significant voltage drop of the battery occurs, causing the device to stop functioning. Without incurring an error, the GPS signal from the satellite can be reliably received and the current position can be detected.

  Hereinafter, embodiments of a position detection device and a position detection method according to the present invention will be described in detail with reference to FIGS. 1 to 4. The following embodiment is an example for realizing the present invention, and the present invention is not limited to the following embodiment. That is, it goes without saying that the present invention can be variously modified by those skilled in the art as long as the technical scope of the present invention belongs.

  FIG. 1 is a block diagram illustrating a configuration of a position detection device according to an embodiment of the present invention. As shown in FIG. 1, the antenna 1, a radio frequency (RF) processing unit 2, and a GPS signal processing unit 3 are configured. Although not shown in the figure, a system having an operation unit for inputting user instructions, a display for displaying time information and position information output from the GPS signal processing unit 3, a power source for supplying power to each unit, and the like Is included in this device.

  The antenna 1 receives radio waves from the satellite and inputs them to the high frequency processing unit 2. The high frequency processing unit 2 amplifies the input radio wave to a necessary level and inputs the amplified radio wave to the GPS signal processing unit 3. The GPS signal processing unit 3 includes a satellite signal processing unit 4, a position calculation unit 5, an RF control unit 6, a measurement start time management unit 7, and a necessary data indexing unit 8. Further, the satellite signal processing unit 4 is connected to the clock unit 9 and appropriately acquires the current time from the clock unit 9. A power source (not shown) is constituted by a coin-type battery, a DC-DC converter, or the like. The satellite signal processing unit 4 controls the operation state (ON) and the non-operation state (OFF) by the RF control unit 6, and extracts a GPS signal from the high frequency signal input from the high frequency processing unit 2 in the operation state. Then, the data is demodulated and converted from an analog signal to a digital baseband signal, and data necessary for determining time information and position information is stored in a plurality of search engines.

  FIG. 2 is a diagram illustrating a format of a subframe that is a navigation message of a GPS signal. One frame is composed of five subframes and is transmitted in order from subframe # 1 to subframe # 5. As described above, subframe # 1 to subframe # 3 are composed of unique data (referred to as “ephemeris”) in each satellite, and subframe # 4 and subframe # 5 synchronize GPS signals. It consists of data common to 32 satellites to be transmitted (referred to as “almanac”). When all the data of these five subframes are acquired, position information corresponding to the satellite is obtained. In order to detect the current position, it is necessary to acquire position information corresponding to each of the four (at least three) satellites, and therefore, in general, a total of 20 subframes are acquired.

  As shown in FIG. 2, each subframe is composed of 300 bits having a time length of 6 seconds. Therefore, the main frame is composed of 1500 bits having a time length of 30 seconds, and the main frame is transmitted every 30 seconds from 32 satellites. Usually, at the beginning of each subframe, there is 30-bit TLM (Telemetry) data, followed by 30-bit HOW (Handover Word) data, followed by a 240-bit clock and each satellite. Data indicating the status (subframe # 1), ephemeris data (subframe # 2, # 3) such as detailed orbit information unique to each satellite, rough orbit information common to 32 satellites, ionosphere correction information, etc. There is almanac data (subframes # 4 and # 5). However, since all the data of the almanac cannot be transmitted once, the subframes # 4 and # 5 are divided into 25 pages and transmitted.

  As described above, the GPS signal of the navigation message is managed by setting the first transmission start after the satellite launch to 00 seconds per week, managing the passage of real time in weeks and seconds, and starting from the Nth 00 seconds to subframe # 1. Starts. Accordingly, it is possible to recognize in advance the number of the subframe transmitted at X hours, Y minutes, and Z seconds in real time. In FIG. 1, the measurement start time management unit 7 stores the actual time X hour, Y minute, and Z second at which transmission of subframe # 1 starts in the transmission timing recording folder, and updates the actual time with the current time of the clock unit 9 Then, the measurement start time is determined based on the transmission timing of the subframe to be acquired. Since the actual time at which transmission of subframe #n (n = 2 to 5) starts is X hour Y minute {Z + 6 (n-1)} seconds, transmission of subframes # 2 to # 5 starts. The actual time to be calculated may be appropriately calculated by calculation as necessary, or the actual time at which transmission of each subframe starts may be stored in the transmission timing recording folder. Furthermore, the measurement start time management unit 7 stores and manages identification information for identifying presence / absence of unacquired subframe data in a memory.

  The transmission timing of the subframe to be acquired is not necessarily managed based on the GPS time. For example, subframe transmission timing may be managed based on UTC (World Standard Time) or local time. When managing based on UTC or local time, as of June 22, 2006, 14 seconds of “leap second” is subtracted from UTC or local time. Note that the time of the clock unit 7 is calibrated as an initial value by a GPS signal received at the time of product shipment, but even if it is not calibrated, the user first gives an instruction to acquire time information and position information. It is automatically calibrated by the received GPS signal.

  FIG. 3 is a diagram showing more detailed contents of subframe # 1 to subframe # 5 in FIG. As shown in FIG. 3A, the main frame is composed of 1500 bits having a time length of 30 seconds, and the main frame is transmitted every 30 seconds from 32 satellites. As shown in FIG. 3B, each subframe is composed of 300 bits having a time length of 6 seconds. Each subframe has 30-bit TLM (Telemetry) data at the head, followed by 30-bit HOW (Handover Word) data, followed by a 240-bit clock and each satellite. Data indicating the status (subframe # 1), ephemeris data (subframe # 2, # 3) such as detailed orbit information unique to each satellite, rough orbit information common to 32 satellites, ionosphere correction information, etc. The almanac data (subframes # 4 and # 5) follow. In order to acquire the position information, data of subframe # 1 to subframe # 3 is necessary.

  The GPS signal of the navigation message manages the passage of real time in weeks and seconds, with the first transmission start after satellite launch being 00 seconds per week. That is, transmission of subframe # 1 is started at 00 seconds, 30 seconds, 60 seconds ... 604739 seconds, 604769 seconds of any wth week, 00 seconds, 30 seconds, 60 seconds ... of the (w + 1) th week. The

4 to 6 are flowcharts showing a GPS reception method executed by the measurement start time management unit 6, and FIG. 7 is a specific example of the GPS reception method.
In the flowchart of FIG. 4, initialization processing is first performed, and the contents of registers, flags, and memories in the apparatus are initialized (step S1). Thereafter, it is determined whether or not an instruction to measure the current position is given from the outside (step S2). If no instruction is given, other processes other than the current position measurement are performed (step S3), and the process of step S1 is performed again. Return.

  On the other hand, if it is determined that a measurement instruction has been made, the process proceeds to step S4, where it is determined whether or not this instruction is a preliminary measurement, that is, the first measurement instruction. If it is a prior measurement, the RF (high frequency processing unit 2) and BB (baseband processing unit 4 of the satellite signal processing unit 4) are turned on (step S5), and offset time measurement is started ( Step S6), measurement of position information is started (step S7). Here, the offset time is the time from when RF and BB are turned on until the subframe information can be stably received. Next, it is determined whether or not synchronization has been established by receiving a preamble pattern which is the first 8 bits of the TLM of an arbitrary subframe (step S8).

If it is determined in step S8 that synchronization has been established, the offset time measured at this point is first stored (step S9). Then, it progresses to step S10, acquires the start time (T0 in FIG. 7) of the received sub-frame, and stores it (step S10). This time is basically the time included in the subframe acquired from the satellite. As another method, it may be acquired from the clock unit 7 of the present apparatus. However, this is based on the premise that the time coincides with the satellite time included in the acquired subframe. For this purpose, the time from the satellite is acquired, and the time of the clock unit 7 is determined by the acquired satellite time. Means for time synchronization such as correction may be considered.
On the other hand, when synchronization is not established, this may be a case where the reception environment is bad, etc., but it is determined whether or not this state has elapsed for a predetermined time (step S11), and if it is determined that the predetermined time has elapsed, RF, The power supply of BB is turned off (step S12), and the process returns to step S2 to wait for a measurement instruction again. That is, the current position measurement process is stopped.

Here, the description returns to the processing after step S10. When the process of step S10 is performed, the process proceeds to step S13 of FIG. 5 to acquire information for one currently received subframe (subframe # 2 in FIG. 7). Then, the subframe number ("2" in FIG. 7) is extracted from the acquired information and stored (step S14).
Further, when the time from the satellite is used as the time acquired in step S10, the process of step S13 may be performed first to extract the satellite time included in the acquired subframe.

The basic process of the pre-measurement ends here, but in this embodiment, when the acquired subframe number is “1”, the current position measurement process is continuously performed.
That is, whether or not the acquired subframe number is the numbers “1”, “2”, and “3” of the three subframes # 1 to # 3 necessary for acquiring the position information after the process of step S14. It discriminate | determines (step S15). If there is a subframe that could not be acquired, the unacquired subframe number is stored (step S16). For example, as shown in FIG. 7, when only subframe # 2 can be acquired and subframes # 1 and # 3 cannot be acquired, subframe numbers 1 and 3 are stored. On the other hand, when the numbers of the three subframes # 1 to # 3 are acquired, the current position information is calculated by decoding the data of the acquired subframes # 1 to # 3 (step S17). Then, the power sources of RF and BB are turned off (step S18).
On the other hand, after storing the unacquired subframe number in step S16, the process proceeds to step S18, and the power supplies of RF and BB are turned off.
After the process of S18, the process returns to step S2 to wait for a measurement start instruction again.
The above is the operation of the prior measurement process.

Next, a description will be given of an operation when a measurement instruction is given again after the pre-measurement process is performed and the offset time, the subframe number, and the subframe start time are stored.
In this case, the process proceeds from step S4 in FIG. 4 to step S19 in FIG. In this process, the current time measured by the clock unit 7 is acquired. Subsequently, based on the acquired current time, the stored subframe number and subframe start time, and the offset time, the time to turn on RF and BB to acquire an unacquired subframe is calculated. (Step S20).

Specifically, the elapsed time from the stored frame start time to the current time is calculated, and the subframe number received at the current time is calculated from the elapsed time and the stored subframe number. From the subframe number, the start time (time T1 in FIG. 7) of the unacquired subframe (in this case, subframe # 1) that follows is calculated. Then, the offset time is subtracted from the start time of the unacquired subframe to obtain the time to be turned on. If this calculated time to be turned on has elapsed, 30 seconds are added to this time to be turned on so that the next unacquired subframe can be obtained.
Of course, the method for calculating the time to be turned on is not limited to the above method. From the stored subframe number and subframe start time, the start time of subframe # 1 in that frame is first calculated, and the start time of the unacquired subframe that follows is calculated from this time and the current time. It may be.

After the time to be turned on is calculated in the process of step S20, the process proceeds to step S21 and waits until the time to turn on has come. When the time to be turned on arrives, the RF and BB power supplies are turned on (step S22), and position measurement is started (step S23). Next, it is determined whether or not synchronization has been established by receiving a preamble pattern which is the first 8 bits of the TLM of an arbitrary subframe (step S24).
If it is determined here that synchronization has been established, information on unacquired subframes is acquired, and data on newly acquired subframes is decoded (step S25). In the example of FIG. 7, the data of subframe # 1 and subframe # 3 are decoded. Thereafter, it is determined whether or not the three subframes # 1 to # 3 have been acquired (step S26). If there are subframes that cannot be acquired, the RF and BB powers are turned off (step S27). When subframes # 1 to # 3 are acquired in step S26, current position information is calculated (step S29). Then, the power sources of RF and BB are turned off (step S27). Thereafter, the process returns to step S2 and waits for a measurement instruction again.
On the other hand, if the synchronization is not established due to a bad reception environment or the like, it is determined whether or not a predetermined time has elapsed (step S28). If it is determined that the predetermined time has elapsed, the process proceeds to S27 and the BB power is turned on. Turn off. That is, the current position measurement process is stopped.

As described above, according to the position detection device and the position detection method of this embodiment, the measurement start time management unit 7 includes the five subframes from the first to the fifth of the navigation message transmitted from the satellite. There is a transmission timing recording folder for storing the actual time of data transmission. Based on the actual transmission time of the five subframe data stored in the transmission timing recording folder and the current time of the clock unit 9, In order to receive unacquired subframe data among the subframe data, the satellite signal processing unit 4 is controlled to be in an operating state via the RF control unit 6.
Therefore, even when a coin-type battery or other small battery is used as a power source, it avoids unnecessary power consumption and does not cause a situation where a significant voltage drop of the battery occurs and the device stops functioning. The GPS signal from the satellite can be reliably received and the current position can be detected.

Moreover, in the said embodiment, the measurement start time management part 7 controls the satellite signal process part 4 to an operation state intermittently in order to receive at least 1 unacquired sub-frame data. In the example of FIG. 7, after acquiring the unacquired subframe # 1, the satellite signal processing unit 4 is maintained in the operating state until the next unacquired subframe # 3 is acquired. Is much shorter than the time of one subframe, after acquiring the unacquired subframe # 1, the satellite signal processing unit 4 is deactivated, and the next unacquired subframe # 3 is At the time of acquisition, the satellite signal processing unit 4 may be controlled to be in an operating state. Alternatively, the satellite signal processing unit 4 may be controlled to acquire the unacquired subframe # 3 after 30 seconds. In short, an acquisition method with the least power consumption may be selected.
Therefore, according to the position detection device and the position detection method of the above-described embodiment, it is possible to minimize power consumption without causing a significant voltage drop of the battery and causing the device to stop functioning.

  In the above embodiment, the configuration is such that three subframe data consisting of subframe # 1 to subframe # 3 included in the navigation message transmitted from each satellite is received. The number of is not limited to three. For example, if a GPS system capable of detecting the current position from four or more arbitrary m subframe data can be constructed in the future, a position detection device that receives m subframe data is configured.

The block diagram which shows the structure of the position detection apparatus in embodiment of this invention. The figure which shows the format of the sub-frame which is the navigation message of a GPS signal. The figure which shows the detailed content of the sub-frame of FIG. The flowchart of the GPS reception method in embodiment. The flowchart of the GPS receiving method following FIG. The flowchart of the GPS receiving method following FIG. The figure which shows the specific example of the GPS receiving method in embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Antenna 2 High frequency processing part 3 GPS signal processing part 4 Satellite signal processing part 5 Position calculating part 6 RF control part 7 Measurement start time management part 8 Necessary data index part 9 Clock part

Claims (2)

A time measuring means for measuring the current time;
Receiving means for receiving a navigation message transmitted from a satellite;
In response to a pre-measurement instruction of the current position, the reception unit is operated for a predetermined time, and an offset from when the reception unit is in an operating state until the subframe included in the navigation message can be stably received. Offset time measuring means for measuring time;
After the measurement of the offset time, a first subframe acquisition unit that acquires a subframe while the reception unit is in an operating state, and acquires a start time of the received subframe and a subframe number; ,
Unacquired subframe number detecting means for detecting the number of unacquired subframes based on the subframe number obtained by the first subframe obtaining means;
When a measurement instruction is given after the preliminary measurement, the current time measured by the time measuring unit, the offset time measured by the offset time measuring unit, and the first subframe acquisition unit Based on the subframe start time and the subframe number, and the unacquired subframe number detected by the unacquired subframe number detection means, the receiving means for obtaining the unacquired subframe. Time calculating means for calculating the time to set the operation state,
Second subframe acquisition means for operating the reception means at the time calculated by the time calculation means to acquire the unacquired subframe;
Current position calculation means for calculating a current position based on the subframes acquired by the first subframe acquisition means and the second subframe acquisition means;
A position detection device comprising: A position detecting method for a position detecting device, comprising a time measuring means for measuring the current time and a receiving means for receiving a navigation message transmitted from a satellite,
In response to a pre-measurement instruction of the current position, the reception unit is operated for a predetermined time, and an offset from when the reception unit is in an operating state until the subframe included in the navigation message can be stably received. An offset time measurement step for measuring time;
After the measurement of the offset time, a first subframe acquisition step of acquiring a subframe while the receiving unit is in an operating state, and acquiring a start time of the received subframe and a subframe number; ,
An unacquired subframe number detection step of detecting an unacquired subframe number from the subframe number obtained in the first subframe acquisition step;
When a measurement instruction is given after the preliminary measurement, the current time measured by the time measuring means, the offset time measured by the offset time measurement step, and the first subframe acquisition step are acquired. The receiving means for acquiring the unacquired subframe based on the subframe start time and the subframe number and the unacquired subframe number detected by the unacquired subframe number detection step. A time calculating step for calculating the time to set the operation state,
A second subframe acquisition step of operating the receiving means at the time calculated by the time calculation step to acquire the unacquired subframe;
A current position calculating step for calculating a current position based on the subframes acquired in the first subframe acquisition step and the second subframe acquisition step;
The position detection method characterized by performing.

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