JP2007093360A - Navigation device and azimuth calculation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a navigation device, capable of preventing deterioration of detection accuracy of a traveling azimuth, using a magnetometric sensor caused by an influence of a magnetic body around the magnetometric sensor, and specifying accurately a traveling position by detecting the traveling azimuth by using the magnetometric sensor, even when GPS signal cannot be received, and an azimuth calculation method for calculating the traveling azimuth accurately from an output value from the magnetometric sensor. <P>SOLUTION: When GPS signal can be received, the traveling azimuth is calculated from the positional information from GPS and from an output value from a gyro sensor. When GPS signal cannot be received, the traveling azimuth is calculated from the output value from the magnetometric sensor on reference to an azimuth calculation table. When the traveling azimuth is calculated from the positional information from the GPS and from the output value from the gyro sensor, the calculated traveling azimuth and the output value from the magnetometric sensor are recorded as updating data for the calculation table of the magnetometric sensor. When the pieces of data have been accumulated up to the prescribed number, the calculation table is updated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a navigation device that specifies a travel position of an automobile, and also relates to an orientation calculation method that calculates a travel orientation of an automobile that is required when specifying the travel position of an automobile.

  2. Description of the Related Art In recent years, an automobile navigation device that can specify a traveling position of an automobile and guide an appropriate route to a destination set by a driver has been used. The navigation device uses a GPS (Global Positioning System) that specifies a traveling position based on radio waves transmitted from an artificial satellite. There are a plurality of GPS satellites, the navigation device receives GPS signals from the plurality of satellites, measures the time difference of the received GPS signals, and identifies the traveling position of the vehicle based on the measured time difference .

  In addition, since an error of about several tens of meters occurs when specifying the traveling position only by GPS, the navigation device outputs according to the traveling position obtained by GPS, the traveling direction of the automobile detected by the gyro sensor, and the speed of the automobile. The map database is collated using information such as the traveling speed obtained by detecting the vehicle speed pulse, and the final traveling position is calculated. This is a so-called map matching process, and an accurate driving position of the vehicle can be specified by performing the map matching process.

  However, although the absolute position can be obtained by specifying the driving position based on the time difference of the GPS signal, the GPS signal is stabilized when the car is traveling in an underground parking lot, a tunnel or a valley of a building. May not be able to be received. In addition, the direction detection by the gyro sensor and the speed detection by the vehicle speed pulse can obtain a stable output without being influenced by the driving state of the automobile, but the relative value is detected. If accurate position information cannot be obtained, the detection accuracy may deteriorate.

  When the navigation device performs the map matching process, the information about the driving direction of the car is particularly important. Therefore, it is necessary to detect the traveling direction stably and accurately. When absolute position information by GPS cannot be obtained, in the detection of the driving direction by the gyro sensor that detects a relative value, a minute error becomes a large error as time passes. There is a problem of lowering the specific accuracy. However, since a situation in which a car continues to run without receiving GPS signals often occurs, the driving direction must be detected only by a gyro sensor at this time, which has been a factor of lowering the reliability of the navigation device. .

  There is a method using a magnetic sensor as means for detecting an absolute traveling direction instead of a relative traveling direction. The magnetic sensor can detect the absolute driving direction at the driving point of the car by detecting the geomagnetism on the earth, but ignores the influence of the influence of the magnetic substance around the sensor on the detection result. Therefore, there are few navigation devices in recent years that use a magnetic sensor to detect the traveling direction.

FIG. 6 is a schematic diagram showing the output of the magnetic sensor. The magnetic sensor detects geomagnetism in two directions of one direction (X direction) and a direction orthogonal to this (Y direction), and outputs a voltage value corresponding to the geomagnetism for each direction as a detection result. FIG. 6 is a graph showing two output values when the magnetic sensor is rotated 360 °. A vector from the origin O to one point on the graph determined by two output values indicates the traveling direction, and the angle θ between this vector and the Y axis can be calculated from the following equation.
tan θ = X / Y

  The output value of the magnetic sensor is a perfect circle shown by the alternate long and short dash line in FIG. However, in reality, the output value of the magnetic sensor has a distorted ring shape as shown by the broken line in FIG. 6 due to the influence of the surrounding magnetic material. As described above, since the accuracy of the magnetic sensor deteriorates due to the influence of the surrounding magnetic material, it has not been widely used for detecting the traveling direction.

  In Patent Document 1, the travel direction of the automobile is calculated from the travel position obtained by the GPS and the travel distance obtained by the distance sensor, and the reference value of the detection by the magnetic sensor from the calculated travel direction, that is, the origin O in FIG. A hybrid navigation device has been proposed that can reduce the influence of surrounding magnetic materials by correcting the position.

  Further, in Patent Document 2, the travel direction obtained by the geomagnetic sensor and the travel direction obtained by the gyro sensor are weighted and averaged to calculate the travel direction, and further, the obtained travel direction and the travel direction obtained from the GPS are weighted. There has been proposed a traveling direction detection device that can reduce the influence of surrounding magnetic materials by calculating a final traveling direction on average.

In Patent Document 3, the reference value of detection by the magnetic sensor, that is, the position of the origin O in FIG. 6 is corrected, and the output value of the magnetic sensor is further corrected to the ellipse to obtain the final output value of the magnetic sensor. There has been proposed a vehicle traveling direction correction device that can reduce the influence of surrounding magnetic bodies by weighted averaging of the output value of the magnetic sensor, the traveling direction obtained by the gyro sensor, and the traveling direction obtained by the GPS.
Japanese Patent Laid-Open No. 62-191713 Japanese Patent Laid-Open No. 5-288558 JP-A-5-297799

  However, the traveling azimuth detecting device described in Patent Document 2 has a problem that the detection accuracy deteriorates when a signal from the GPS cannot be received. Further, in the hybrid navigation device described in Patent Document 1, the reference value for detection by the magnetic sensor is corrected, but the output value of the magnetic sensor affected by the surrounding magnetic material is indicated by a broken line in FIG. Since the ring is distorted in a complicated manner as described above, even if the reference value is corrected, that is, the position of the origin O is corrected, a great improvement in accuracy cannot be expected. In addition, in the vehicle traveling direction correction device described in Patent Document 3, ellipse correction is performed on the output value of the magnetic sensor in addition to the correction of the reference position. Therefore, there is a limit to the correction in the approximation by an ellipse, and a large improvement in accuracy cannot be expected.

  The present invention has been made in view of such circumstances, and an object of the present invention is to use the correspondence between the output value and the orientation as correspondence information in order to calculate the orientation of the vehicle from the output value of the magnetic sensor. By storing, updating the correspondence information according to the influence of the surrounding magnetic body and the driving situation, etc., and using the updated correspondence information to calculate the direction of the car from the output value of the magnetic sensor, An object of the present invention is to provide a navigation device that can prevent deterioration in accuracy of detection of a traveling position using a magnetic sensor due to the influence of surrounding magnetic materials.

  Another object of the present invention is to receive a signal from the GPS by averaging and recording the output value of the magnetic sensor for each azimuth calculated from the position information obtained by the GPS. Sometimes, it is possible to collect information for updating with higher accuracy, and to provide a navigation device that can update correspondence information with higher accuracy.

  According to another object of the present invention, when the output values of the magnetic sensor are averaged over a predetermined number, the correspondence information is updated based on the averaged value. The object is to provide a navigation device that can be updated more accurately.

  In addition, another object of the present invention is to provide a configuration in which a traveling direction is calculated based on position information acquired by GPS and a relative direction by a gyro sensor and used for updating correspondence information. An object of the present invention is to provide a navigation device that can update information more accurately.

  Another object of the present invention is to provide a navigation system that can accurately detect the azimuth by the magnetic sensor by using two magnetic sensors that respectively detect the magnetic quantities in two intersecting directions. To provide an apparatus.

  Another object of the present invention is that the magnetic sensor is housed in a unit separate from the main body of the apparatus, so that the magnetic sensor is not affected by the surrounding magnetic material and the magnetism can be accurately detected. An object of the present invention is to provide a navigation device in which sensors can be arranged.

  Another object of the present invention is to calculate an azimuth from position information obtained by GPS, record the azimuth and the output value of the magnetic sensor in association with each other, and store them in advance based on an average value of a plurality of output values. It is to provide a direction calculation method that can correct the output value of the magnetic sensor with respect to the influence of surrounding magnetic bodies and update the traveling direction with high accuracy by updating the corresponding information. .

  A navigation device according to a first aspect of the present invention is a navigation device comprising: an acquisition unit that acquires information relating to a position of a moving body; and a position specifying unit that specifies the position of the moving body based on the information acquired by the acquisition unit. A first calculation unit that calculates the orientation of the moving body based on the information acquired by the acquisition unit, a magnetic sensor that outputs an output value corresponding to the detected amount of magnetism, and the output value of the magnetic sensor Storage means for storing correspondence information for calculating the azimuth of the moving object, recording means for associating and recording the azimuth calculated by the first calculation means and the output value of the magnetic sensor, and the recording means for recording Updating means for updating the correspondence information stored in the storage means based on the azimuth and output value, and the moving body based on the output value of the magnetic sensor and the correspondence information stored in the storage means Second position calculating means for calculating an azimuth, wherein the position specifying means specifies the position of the moving body based on the azimuth calculated by the first calculating means and / or the second calculating means. It is characterized by being.

  In the present invention, the traveling direction of the automobile is calculated with reference to correspondence information stored in advance based on the output value of the magnetic sensor. Since the traveling direction is determined based on the correspondence information, it is possible to calculate the traveling direction with high accuracy in accordance with the output value of the annular magnetic sensor that is complicatedly distorted by the influence of the surrounding magnetic body. Further, the azimuth information by GPS and the output value of the magnetic sensor corresponding thereto are recorded, and the correspondence information is updated based on this. When the traveling direction can be detected by GPS, the correspondence relationship between the accurate traveling direction and the output value of the magnetic sensor can be collected, and the accuracy of the correspondence information updated based on this can be increased.

  In the navigation device according to the second aspect of the invention, the recording means averages and records the output values sequentially obtained from the magnetic sensor for each orientation calculated by the first calculation means. Features.

  In the present invention, the output value of the magnetic sensor is averaged and recorded for each traveling direction by GPS. By averaging the output values of the plurality of magnetic sensors, the accuracy of the correspondence information updated based on these values is further increased.

  The navigation device according to a third aspect of the invention is characterized in that updating is performed when the updating means averages a predetermined number of output values of the magnetic sensor.

  In the present invention, the output value of the magnetic sensor with respect to the traveling direction by GPS is averaged over a predetermined number of times, and the correspondence information is updated when sufficient data can be collected to update the correspondence information. Thereby, the influence of the measurement error can be reduced, and the correspondence information can be updated more accurately.

  A navigation device according to a fourth aspect of the present invention includes a gyro sensor that detects angular velocity, and the first calculation unit is configured to detect the moving object based on the information acquired by the acquisition unit and the detection result of the gyro sensor. It is characterized in that the azimuth is calculated.

  In the present invention, the traveling azimuth is calculated based on the positional information acquired by the GPS and the relative azimuth obtained by the gyro sensor. Since position information obtained by GPS indicates an absolute position, an accurate traveling direction can be calculated by combining GPS and a gyro sensor. By updating the correspondence information based on the accurate traveling direction, the accuracy of detection of the traveling direction by the magnetic sensor using the correspondence information is increased.

  A navigation device according to a fifth aspect of the present invention is the navigation device, wherein the magnetic sensor detects a magnetic quantity in one direction, and a second sensor detects the magnetic quantity in a direction crossing the one direction. It is characterized by comprising.

  In the present invention, the amount of magnetism is detected in each of two directions intersecting using two magnetic sensors, and the traveling direction is calculated. Even in a situation where GPS signals cannot be received, a two-dimensional absolute traveling direction can be easily obtained by combining the output values of the two magnetic sensors, and the traveling direction can be detected with high accuracy.

  A navigation device according to a sixth aspect of the invention is characterized in that the magnetic sensor is housed in a unit different from the device main body, and includes connection means for connecting the device main body and the unit.

  In the present invention, the magnetic sensor is housed in a unit different from the apparatus main body, and is disposed at a position that is not easily affected by the surrounding magnetic body in the automobile. In many cases, an audio device, a circuit for controlling a vehicle, or the like is disposed near a place where a navigation device in the vehicle is disposed, which may deteriorate the accuracy of the magnetic sensor. For this reason, the deterioration of the detection system can be prevented by arranging the magnetic sensor in a place where there is little influence of other devices.

  An azimuth calculating method according to a seventh aspect of the present invention is the azimuth calculating method for calculating the azimuth of the moving body, wherein correspondence information for calculating the azimuth of the moving body is calculated from an output value corresponding to the amount of magnetism detected by the magnetic sensor. Record, acquire information related to the position of the moving object, calculate the orientation of the moving object based on the acquired information, acquire the output value of the magnetic sensor, and information related to the position of the moving object For each azimuth calculated from the above, the output values obtained sequentially from the magnetic sensor are averaged and recorded, and when a predetermined number of output values of the magnetic sensor are averaged, they are stored based on the averaged value. The correspondence information is updated, and the direction of the moving body is calculated based on the output value of the magnetic sensor and the correspondence information.

  In the present invention, the traveling direction is calculated with reference to correspondence information stored in advance based on the output value of the magnetic sensor. In addition, the traveling direction calculated from the position information by GPS and the output value of the magnetic sensor are recorded in association with each other. At this time, the output values obtained sequentially from the magnetic sensor are averaged and recorded for each traveling direction by GPS. The correspondence information is updated based on the correspondence between the averaged output value and the driving direction by GPS. Since the traveling direction is determined based on the correspondence information, it is possible to calculate the direction with high accuracy in accordance with the output value of the magnetic sensor having an annular shape that is complicatedly distorted by the influence of the surrounding magnetic body. Further, when the traveling direction can be detected by GPS, the correspondence between the accurate traveling direction and the output of the magnetic sensor can be collected as data for updating the correspondence information.

  In the case of the first invention, the output of the magnetic sensor having an annular shape that is complicatedly distorted by the influence of the surrounding magnetic material is obtained by calculating the traveling direction with reference to the correspondence information based on the output value of the magnetic sensor. The driving direction can be calculated with high accuracy by correcting the value with the corresponding information. Further, by adopting a configuration in which the correspondence information is updated according to the influence of the surrounding magnetic body, the accuracy of the correspondence information can be increased. Therefore, even when the automobile is traveling in a place where GPS signals cannot be received, it is possible to detect the traveling direction with high accuracy using the magnetic sensor, and to improve the reliability of the navigation device.

  Further, in the case of the second invention, when the signal from the GPS can be received by configuring the output value of the magnetic sensor to be averaged and recorded for each azimuth calculated from the position information by the GPS, Because it is possible to collect information for more accurate updates and to update the corresponding information more accurately, even if the car is traveling in a place where GPS signals cannot be received, a magnetic sensor is used. Therefore, it is possible to detect the traveling direction with high accuracy and to improve the reliability of the navigation device.

  In the case of the third invention, the correspondence relationship between the accurate driving direction by the GPS and the output value of the magnetic sensor is collected as data for updating the correspondence information, and this corresponds to the case where a predetermined number or more of data can be collected. By adopting a configuration that updates information, the influence of measurement errors can be reduced, and more accurate correspondence information can be updated. Therefore, it is possible to perform accurate traveling direction detection using a magnetic sensor. The reliability of the navigation device can be improved.

  Further, in the case of the fourth invention, the travel direction is calculated based on the position information acquired by the GPS and the relative direction by the gyro sensor, and is used for updating the correspondence information. Since the position information indicates an absolute position, an accurate traveling direction can be calculated by combining the GPS and the gyro sensor, and the correspondence information can be updated based on the accurate traveling direction. The traveling direction can be detected with high accuracy using the sensor, and the reliability of the navigation device can be improved.

  According to the fifth aspect of the invention, by using two magnetic sensors that respectively detect the magnetic quantities in two intersecting directions, the two-dimensional absolute value can be easily obtained by combining the output values of the two magnetic sensors. A reliable traveling direction can be obtained and the traveling direction can be accurately detected. Therefore, even in a situation where GPS signals cannot be received, the traveling direction can be accurately detected using a magnetic sensor. You can increase the sex.

  According to the sixth aspect of the invention, the magnetic sensor is housed in a unit separate from the main body of the apparatus, so that the magnetic sensor is arranged at a position where it is difficult to be affected by the surrounding magnetic body and can detect the magnetism with high accuracy. Therefore, the accuracy of the magnetic sensor can be prevented from deteriorating, and the reliability of the navigation device can be improved.

  Further, in the case of the seventh invention, the output value of the magnetic sensor that forms a ring that is complicatedly distorted by the influence of the surrounding magnetic material by calculating the traveling direction with reference to the corresponding information based on the output value of the magnetic sensor. Can be corrected with the correspondence information to calculate the driving direction with high accuracy. In addition, the output value obtained sequentially from the magnetic sensor is averaged and recorded for each driving direction by GPS, and the correspondence information is updated using the value averaged more than a predetermined number of times, so that the driving direction by GPS is updated. When the detection can be performed, the correspondence relationship between the accurate traveling direction and the output of the magnetic sensor can be collected as data for updating the correspondence information, and the correspondence information can be updated to increase the accuracy. Therefore, even when the vehicle is traveling in a place where GPS signals cannot be received, it is possible to perform accurate traveling direction detection using the magnetic sensor.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. FIG. 1 is a block diagram showing a configuration of a navigation apparatus according to the present invention. In the figure, reference numeral 1 denotes a main body of the navigation device, an operation unit 10 provided with switches and buttons for operation by the driver, a display unit 8 by a liquid crystal display on which a map or a message to the driver is displayed. And a voice output unit 9 that outputs a voice message to the driver, and is installed, for example, in the center of the front of the vehicle.

  The operation from the driver is accepted by the operation unit 10 and given from the operation unit 10 to the CPU 2. The CPU 2 performs calculations based on information from various sensors, calculates the travel position of the automobile, and controls the display unit 8 and the audio output unit 9 to notify the driver of the optimum route to the destination. Yes, the destination, operating conditions, and the like are set by the driver's operation given from the operation unit 10, and calculation and control are performed according to these.

  The navigation device has a GPS antenna 25 that is separate from the main body 1, and the GPS antenna 25 can easily receive GPS signals transmitted from GPS artificial satellites such as the upper surface of the dashboard or the ceiling in a car. Placed in place. The GPS antenna 25 is connected to the GPS receiver 3 of the main body 1 by a cable 26. The GPS receiver 3 measures the time difference of GPS signals from a plurality of artificial satellites received by the GPS antenna 25, estimates the position of the vehicle in the longitude direction and the latitude direction based on the measured time difference, and gives it to the CPU 2. It is.

  The CPU 2 is given a vehicle speed pulse detection result, which is information related to the traveling speed of the automobile, from the vehicle speed pulse detection unit 5. The vehicle speed pulse detected by the vehicle speed pulse detection unit 5 is output every time the automobile travels a certain distance, and the traveling speed of the automobile can be calculated by detecting this. Further, the relative traveling direction of the automobile detected by the gyro sensor 6 is given to the CPU 2. The gyro sensor 6 outputs a voltage corresponding to the angular velocity applied to the piezoelectric body, and can detect the relative traveling direction of the automobile by detecting the angular velocity applied to the piezoelectric body when the direction of the automobile is changed. . The CPU 2 is given an acceleration detected by the acceleration sensor 7. The acceleration sensor 7 detects acceleration applied to the automobile, and can calculate the relative traveling speed of the automobile by detecting the acceleration in the front-rear direction of the vehicle.

  The navigation device has a sensor unit 20 that is separate from the main body 1, and the sensor unit 20 includes two magnetic sensors 21 and 22. The magnetic sensors 21 and 22 detect the earth's geomagnetism, and are arranged in the sensor unit 20 so that the detection direction of the magnetic sensor 21 and the detection direction of the magnetic sensor 22 are substantially perpendicular. By detecting the geomagnetism in two substantially perpendicular directions, the two-dimensional absolute traveling direction of the automobile can be calculated. Since the magnetic sensors 21 and 22 are deteriorated in detection accuracy when a magnetic material is arranged around them, the sensor unit 20 is located away from the installation location of the main body 1 where a large number of electronic devices are likely to be arranged. For example, it is installed on the upper surface of the dashboard or the rear surface of the rearview mirror. The sensor unit 20 and the main body 1 are connected by a cable 23, and an interface 4 for connecting the cable 23 is provided in the main body 1. The detection results of the magnetic sensors 21 and 22 of the sensor unit 20 are given to the interface 4 via the cable 23 and from the interface 4 to the CPU 2.

  The CPU 2 performs a map matching process for collating information given from the GPS receiver 3, the vehicle speed pulse detector 5, the gyro sensor 6, the acceleration sensor 7, the magnetic sensors 21, 22 and the like with the map data 13, and finally Identify the location of the car. The map data 13 used for the map matching process is stored in the map data storage unit 12, and the CPU 2 reads out the necessary data from the map data storage unit 12 and performs the process. The map data storage unit 12 is, for example, a DVD drive that reads a DVD on which map data 13 is recorded, a hard disk drive on which map data 13 is recorded, and the like.

  In addition, the CPU 2 can store in the memory 11 detection results of various sensors, calculation results for specifying the position, setting information of the navigation device set by the driver, and the like. The memory 11 is preferably a non-volatile memory having a large capacity, and for example, a flash memory can be used. The memory 11 also stores an azimuth calculation table, which is correspondence information for calculating the driving azimuth of the automobile from the output values of the magnetic sensors 21 and 22, and an update table (recording data for calibrating the azimuth calculation table). Both of which will be described later) are stored.

  The traveling direction of the vehicle by the magnetic sensors 21 and 22 is used for specifying the traveling position when the vehicle is traveling in a tunnel, an underground parking lot, a valley of a building, or the like, and the GPS receiver 3 cannot receive a GPS signal. When the GPS signal can be received, the travel direction calculated from the absolute position by GPS and the relative travel direction by the gyro sensor 6 is used for specifying the travel position.

  As shown in FIG. 6, the output value when the magnetic sensors 21 and 22 are rotated once is affected by the surrounding magnetic material, and therefore does not exhibit an ideal perfect circular characteristic, and has a complicated and distorted annular shape. Show the characteristics. For this reason, in the navigation apparatus according to the present invention, the correspondence relationship in consideration of the influence of the surrounding magnetic body between the traveling direction and the outputs of the magnetic sensors 21 and 22 is stored in the memory 11 as the direction calculation table. When the CPU 2 calculates the travel direction using the magnetic sensors 21 and 22, the CPU 2 reads the direction calculation table from the memory 11, and calculates the travel direction of the automobile by referring to the direction calculation table from the output values of the magnetic sensors 21 and 22. .

  FIG. 2 is an azimuth calculation table for calculating the traveling azimuth from the output values of the magnetic sensors 21 and 22. In the azimuth calculation table, output values of the two magnetic sensors 21 and 22 are recorded in association with each other from 0 ° to 359.9 ° every 0.1 ° of the driving azimuth of the automobile. Note that the X output of the azimuth calculation table is the output value of the magnetic sensor 21, and the Y output is the output value of the magnetic sensor 22. The CPU 2 acquires the X output and the Y output from the magnetic sensors 21 and 22, respectively, searches for the closest one among a plurality of sets of the X output and the Y output in the azimuth calculation table by vector calculation, and the closest X output. And the direction associated with the set of Y outputs is the traveling direction of the vehicle.

  The vehicle body may be magnetized while the vehicle is running, and the driver may add or replace electronic devices in the vehicle. In order to deal with the case where the environment related to the magnetic field around the magnetic sensors 21 and 22 changes in this way, the navigation device according to the present invention automatically updates the azimuth calculation table during traveling and is suitable for the surrounding environment. The direction is calculated.

  FIG. 3 is an update table for recording data used for updating the azimuth calculation table. The data recorded in the update table is obtained from the magnetic sensors 21 and 22, which are calculated based on the positional information obtained from the GPS and the relative orientation obtained from the gyro sensor 6 (hereinafter referred to as the GPS orientation). X output, Y output, and average number indicating the number of times data is averaged, and these are recorded in association with each other.

  When the GPS azimuth is obtained, the CPU 2 acquires the output values of the magnetic sensors 21 and 22 and records them in the update table in association with each other. At this time, if the X output and the Y output for the GPS azimuth in the update table are already recorded, the recorded value and the newly acquired value are averaged, and the average value is recorded in the update table. When averaging is performed, the corresponding average number is increased, and when the average number reaches a predetermined number of times or more, the X output and Y output values of the azimuth calculation table are output as the X output in the update table. And the Y output value.

  FIG. 4 is a flowchart showing a processing procedure when the CPU 2 of the navigation device according to the present invention specifies the travel position. First, the CPU 2 checks whether or not the GPS signal can be received by the GPS receiver 3 (step S1). If the GPS signal can be received (S1: YES), the GPS receiver 3 receives the GPS signal and acquires the position information (step S2). Next, relative azimuth information is acquired from the detection result of the gyro sensor 6 (step S3), and based on the positional information obtained in step S2 and the relative azimuth information obtained in step S3, The travel direction is calculated (step S4). After calculating the traveling direction, calibration processing of the direction calculation table for calculating the direction by the magnetic sensors 21 and 22 is performed (step S5). Details of the calibration process will be described later.

  If it is determined in step S1 that the vehicle is traveling in a tunnel, an underground parking lot, a valley of a building, or the like and cannot receive a GPS signal (S1: NO), the X output and Y from the magnetic sensors 21 and 22 are determined. The output is acquired (step S6), and the driving direction of the vehicle is calculated with reference to the direction calculation table (step S7).

  After performing the calibration process in step S5 or calculating the travel direction in step S7, based on the information obtained from the vehicle speed pulse detector 5 and the acceleration sensor 7 and information such as the calculated travel direction. A map matching process is performed to identify the travel position (step S8). In accordance with the travel position obtained by the map matching process, the display of the map displayed on the display unit 8 is updated to inform the driver of the travel position of the car (step S9). Next, it is checked whether or not the driver has operated the operation unit 10 to give an end command (step S10). If no end command has been given (S10: NO), the process returns to step S1 to perform the processing. repeat. If an end command is given (S10: YES), the process ends.

  FIG. 5 is a flowchart showing a processing procedure in the case where the CPU 2 of the navigation device according to the present invention performs calibration processing of the azimuth calculation table. This is the process performed in step S5 of FIG. First, the CPU 2 acquires the X output and Y output of the magnetic sensors 21 and 22 (step S31), and determines whether the acquired X output and Y output are the first data, that is, the current GPS direction (step of FIG. 4). It is checked whether or not data is recorded in the X output and Y output items of the update table for the orientation calculated in S4 (step S32).

  When the acquired X output and Y output are the first data, that is, when the X output and Y output data for the GPS bearing are not recorded in the update table (S32: YES), the acquired X output and Y output are updated. It records in the position corresponding to the current GPS azimuth | direction of a table (step S33), and sets 1 to the item of the corresponding average frequency (step S34).

In step S32, if the acquired X output and Y output are not the first data, that is, if the X output and Y output data for the GPS orientation has already been recorded in the update table (S32: NO), the following (1) ) To calculate the average value of the X output and the Y output (step S35). In the equation (1), X _A is a new average value of X output, and Y _A is a new average value of Y output. X _a is an X output value recorded in the update table, and Y _a is _a Y output value recorded in the update table. X is a value of X output newly acquired from the magnetic sensor 21, and Y is a value of Y output newly acquired from the magnetic sensor 22. N is the value of the average number recorded in the update table.

  After calculating the average value, the calculated average value is overwritten and recorded in the corresponding position of the update table (step S36), and the corresponding average number is incremented by 1 (step S37).

  After setting the average count to 1 in step S34 or increasing the average count by 1 in step S37, all the average counts in the update table are greater than or equal to a predetermined count (for example, 10 or 100). Is checked (step S38). When all the average times have reached the predetermined number or more (S38: YES), the X output and Y output values in the bearing calculation table are updated to the X output and Y output values in the update table (step S39), and updated. All values in the table are initialized (step S40). After the initialization of the update table, or when the average number has not reached the predetermined number in step S38 (S38: NO), the calibration process is terminated and the original process is returned.

  In the navigation device having the above configuration, the driving direction of the vehicle is calculated with reference to the heading calculation table based on the X output and Y output obtained from the magnetic sensors 21 and 22, so that the magnetic sensor as shown in FIG. Even when the magnetic sensors 21 and 22 are affected by the surrounding magnetic material, it is possible to prevent the detection accuracy of the magnetic sensors 21 and 22 from deteriorating by constantly updating the azimuth calculation table to an optimal state. In addition, when a GPS signal can be acquired, the correspondence between the accurate azimuth by the GPS and the gyro sensor 6 and the output values of the magnetic sensors 21 and 22 is accumulated as update data, and a certain amount or more of data is accumulated. Then, the azimuth calculation table is updated, so that the reliability of the azimuth calculation table is improved, and the accuracy of azimuth detection by the magnetic sensors 21 and 22 when the GPS signal cannot be acquired can be increased. In addition, since the magnetic sensors 21 and 22 are provided in the sensor unit 20 separate from the main body 1 of the navigation device, the magnetic sensors 21 and 22 can be disposed in a place where there is little influence from the surrounding magnetic body in the automobile. The accuracy of azimuth detection by the magnetic sensors 21 and 22 can be increased.

  In the present embodiment, the configuration in which the sensor unit 20 and the GPS antenna 25 are disposed at a different location from the main body 1 is shown, but the present invention is not limited to this, and the configuration is provided integrally with the main body 1. It may be. Moreover, although the structure which connects the sensor unit 20 and the main-body part 1 with the cable 23 was shown, it is not restricted to this, It is the structure which receives the output of the magnetic sensors 21 and 22 using a wireless communication or infrared communication. There may be. In addition, the navigation device has a configuration in which the vehicle speed pulse detector 5 and the acceleration sensor 7 are provided in addition to the gyro sensor 6 and the magnetic sensors 21 and 22, but the present invention is not limited to this, and a configuration in which other sensors are provided. There may be.

  The configurations of the azimuth calculation table shown in FIG. 2 and the update table shown in FIG. 3 are merely examples, and the present invention is not limited to this. In the flowchart shown in FIG. 4, the map matching process is performed using the traveling direction obtained by the magnetic sensors 21 and 22 only when the GPS signal cannot be acquired. However, the present invention is not limited to this, and the GPS signal is acquired. Even when possible, the map matching process may be performed using the traveling directions obtained by the magnetic sensors 21 and 22 together. Further, in the flowchart shown in FIG. 5, when all the average times reach a predetermined number or more, all the values of the X output and the Y output of the azimuth calculation table are updated. However, the present invention is not limited to this. Only the values of the X output and the Y output corresponding to the item whose number of times has reached a predetermined number or more may be updated.

It is a block diagram which shows the structure of the navigation apparatus which concerns on this invention. It is an azimuth | direction calculation table for calculating a driving | running | working azimuth from the output value of a magnetic sensor. It is an update table for recording the data used for the update of an azimuth | direction calculation table. It is a flowchart which shows the process sequence in case CPU of the navigation apparatus concerning this invention specifies a driving | running | working position. It is a flowchart which shows the process sequence in case CPU of the navigation apparatus which concerns on this invention performs the calibration process of an azimuth | direction calculation table. It is a schematic diagram which shows the output of a magnetic sensor.

Explanation of symbols

1 Body (device body)
2 CPU
3 GPS receiver (acquisition means)
5 Vehicle speed pulse detector 6 Gyro sensor 7 Acceleration sensor 11 Memory (storage means)
12 Map data storage unit 13 Map data 20 Sensor unit (unit)
21 Magnetic sensor (first sensor)
22 Magnetic sensor (second sensor)
23 Cable (connection means)
25 GPS antenna

Claims (7)

In a navigation apparatus comprising an acquisition unit that acquires information relating to a position of a moving object, and a position specifying unit that specifies the position of the moving object based on the information acquired by the acquisition unit.
First calculating means for calculating the orientation of the moving body based on the information acquired by the acquiring means;
A magnetic sensor that outputs an output value corresponding to the detected amount of magnetism;
Storage means for storing correspondence information for calculating the orientation of the moving body from the output value of the magnetic sensor;
Recording means for associating and recording the azimuth calculated by the first calculation means and the output value of the magnetic sensor;
Updating means for updating the correspondence information stored in the storage means based on the azimuth and output value recorded by the recording means;
Second calculating means for calculating the orientation of the moving body based on the output value of the magnetic sensor and the correspondence information stored in the storage means;
The navigation device characterized in that the position specifying means specifies the position of the moving body based on the azimuth calculated by the first calculating means and / or the second calculating means.   The navigation device according to claim 1, wherein the recording unit averages and records output values sequentially obtained from the magnetic sensor for each direction calculated by the first calculation unit.   The navigation device according to claim 2, wherein the updating unit performs updating when a predetermined number of output values of the magnetic sensor are averaged. It has a gyro sensor that detects angular velocity,
4. The method according to claim 1, wherein the first calculating unit calculates an azimuth of the moving body based on information acquired by the acquiring unit and a detection result of the gyro sensor. The navigation device described in 1.   The said magnetic sensor is comprised by the 1st sensor which detects the magnetic quantity about one direction, and the 2nd sensor which detects the magnetic quantity about the direction which cross | intersects the said one direction. The navigation device according to any one of the above. The magnetic sensor is housed in a unit separate from the apparatus body,
The navigation apparatus according to claim 1, further comprising a connection unit that connects the apparatus main body and the unit. In the direction calculation method for calculating the direction of the moving object,
Recording correspondence information for calculating the direction of the moving body from the output value corresponding to the amount of magnetism detected by the magnetic sensor,
Obtaining information relating to the position of the moving object;
Calculate the orientation of the moving body based on the acquired information,
Obtaining an output value of the magnetic sensor;
For each azimuth calculated from the information relating to the position of the moving body, the output value obtained sequentially from the magnetic sensor is averaged and recorded,
When the predetermined number of output values of the magnetic sensor are averaged, the correspondence information stored based on the averaged value is updated,
An azimuth calculation method, wherein the azimuth of the moving body is calculated based on an output value of the magnetic sensor and the correspondence information.

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