JP2011002356A - Navigation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a navigation device which is suppressed low in a calculation amount necessary for estimating a present place, even when the number of sensors used for sensor fusion is increased.SOLUTION: A characteristic table in which weights to be given to each sensor in various states are set is stored in a ROM 34. After estimating the present place, a CPU 31 applies information such as the estimated present place, map data and a processing under execution to the characteristic table, to thereby calculate each sensor weight. A sensor whose weight is lower than a prescribed threshold out of four sensors 22a-22d is blocked by a switch group 32 controlled by the CPU 31, to thereby suspend output of a detection value to the CPU 31. Resultantly, the CPU 31 stops utilization of the sensor for estimating the present place.

Description

  The present invention relates to a navigation device having a function of estimating a current location.

  Various sensors such as a speed sensor, an acceleration sensor, and a GPS sensor are mounted on current navigation devices. The navigation device estimates the current location based on information output from a specific sensor among these sensors. The reason why a plurality of sensors are mounted is to enable the present location to be estimated from information acquired from another sensor even in a situation where a specific sensor does not function. For example, Patent Document 1 discloses a navigation device that normally performs positioning by GPS and performs positioning using another sensor when positioning by GPS becomes defective.

  On the other hand, unlike the navigation device disclosed in Patent Document 1, there is a technology called sensor fusion that uses a plurality of sensors simultaneously. This technique improves the accuracy of the estimated current location by combining information output from a plurality of sensors. In sensor fusion, if more sensors are used, more accurate current location estimation can be expected.

JP 7-55480 A

  Increasing the number of sensors used for sensor fusion increases the amount of calculation required to estimate the current location.

  The invention according to claim 1 is an input unit that inputs a plurality of detection values output from a plurality of sensors, an evaluation unit that calculates an evaluation value corresponding to each of the plurality of sensors, and the evaluation unit calculates Based on the evaluation value, a selection unit that selects one or more sensors from the plurality of sensors, and a current location is estimated based on a detection value corresponding to the one or more sensors selected by the selection unit. A navigation apparatus comprising: a current location estimating means.

  According to the present invention, it is possible to reduce the amount of calculation while maintaining high accuracy of the estimated current location by selecting and shutting off a sensor that does not work effectively under the current situation from various sensors. Can do.

It is a block diagram which shows the whole structure of the navigation apparatus in 1st Embodiment. 2 is a diagram showing a detailed configuration of a control circuit 11. FIG. It is a figure which shows the characteristic table for CPU31 to determine the sensor used for the present location estimation. It is a flowchart of a present location estimation process.

-First embodiment-
FIG. 1 is a block diagram showing the overall configuration of the navigation device according to this embodiment.

  The navigation device 1 includes a control circuit 11, a storage device 12, a display monitor 13, an input device 14, a touch panel control unit 15, a touch panel 16, a vibration gyro 22a, a speed sensor 22b, an acceleration sensor 22c, and a GPS sensor 22d.

  The control circuit 11 includes a microprocessor and its peripheral circuits, and performs various controls by executing a control program. The storage device 12 is an HDD or the like in which map data is stored. When the control circuit 11 performs a predetermined route search process based on the map data stored in the storage device 12, the processing result is displayed on the display monitor 13 as a recommended route.

  The map data stored in the storage device 12 includes map display data, route search data, and the like. The map display data and the route search data include road link information and node information stored in the map data. The link information includes information on the travel time of each link (hereinafter referred to as “link travel time”). The map display data has map data of a plurality of scales from wide areas to details, and the scale of the display map can be changed according to a user request. The storage device 12 in which the map data is stored may be a recording medium other than the HDD, such as a DVD-ROM or a CD-ROM.

  The display monitor 13 provides the user with various information such as a road map near the vehicle position as a screen display based on various information such as map data. The input device 14 has an input switch for a user to set various commands, and is realized by an operation panel, a remote controller, or the like. The user sets the destination by operating the input device 14 in accordance with instructions on the display screen of the display monitor 13.

  The touch panel 16 is a transparent touch switch laminated on the surface of the display monitor 13, and an image displayed on the display monitor 13 is displayed through the touch panel 16. The touch panel 16 sends a signal corresponding to the operation position on the touch panel 16 to the touch panel control unit 15. Then, the touch panel control unit 15 calculates the pressed position of the touch panel 16.

  The sensors 22a to 22d are various sensors used for estimating the current location of the vehicle. The control circuit 11 performs sensor fusion based on the detection values obtained from these sensors, and estimates the current location. Then, based on the estimated current location, a display range of the map, a route search start point, and the like are determined, and the current location is displayed on the map.

  The sensors used by the control circuit 11 are a vibration gyro 22a, a speed sensor 22b, an acceleration sensor 22c, and a GPS (Global Positioning System) sensor 22d. The control circuit 11 may use sensors other than these in order to estimate the current location. The control circuit 11 acquires the latest detection value detected by these sensors each time a predetermined time elapses or travels a predetermined distance, and estimates the current location based on a predetermined algorithm.

  The vibration gyro 22a is a sensor for acquiring the traveling direction of the vehicle, the speed sensor 22b is a sensor for acquiring the speed of the vehicle, and the acceleration sensor 22c is a sensor for acquiring the acceleration of the vehicle. The GPS sensor 22d detects a GPS signal from a GPS satellite.

  FIG. 2 is a diagram showing a detailed configuration of the control circuit 11. Hereinafter, the operation of the control circuit 11 will be described with reference to FIG.

  The control circuit 11 includes a CPU 31, a switch group 32, a RAM 33, and a ROM 34. The CPU 31 executes a control program stored in the ROM 34 and performs various controls such as estimation of the current location and route guidance. The RAM 33 is used as a work area when performing these controls. The sensors 22 a to 22 d used for estimating the current location are connected to the CPU 31 through the switch group 32. The CPU 31 estimates the current location based on the detection value of each sensor input through the switch group 32.

  After estimating the current location, the CPU 31 selects a sensor to be used for estimation of the next current location from the four sensors 22a to 22d based on the estimated current location, the map data, and the process being executed by the CPU 31. Sensors that are not selected by the CPU 31 are blocked by the switch group 32, and detection values are not output to the CPU 31. As a result, the CPU 31 does not use this sensor for estimating the current location.

  Next, a procedure for determining a sensor used for estimating the current location by the CPU 31 will be described. The ROM 34 stores a characteristic table in which weights given to the sensors in various situations are set. The CPU 31 applies information such as the estimated current location, map data, and processing being executed to the characteristic table, and calculates the weight of each sensor. The CPU 31 blocks a sensor having a calculated weight smaller than a predetermined threshold value so that it is not used for estimating the current location.

  FIG. 3 is a diagram illustrating a characteristic table for the CPU 31 to determine a sensor used for estimating the current location. Sensors 22a to 22d are assigned to each column of the characteristic table, and various situations are assigned to each row. In FIG. 3, five situations of “urban area”, “tunnel”, “during music playback”, and “map matching not executed” are set.

  A row 41 represents a weight given to each sensor when the current location corresponds to “urban area”. In urban areas, the strength of the GPS signal is reduced due to the influence of surrounding structures, so the GPS sensor 22d is given a lower weight than other sensors. Whether or not the current location is “urban” is determined from the current location and map data.

  Similarly to the row 41, the row 42 represents the weight given to each sensor when the current location corresponds to “tunnel”. Since the GPS signal cannot be received in the tunnel, the weight is set to 0 so that the GPS sensor 22d is not used.

  A row 43 represents the weight of each sensor when the music playback process is being executed. Since the calculation load on the CPU 31 increases during the music playback process, it is desirable to reduce the amount of calculation necessary for estimating the current location as much as possible. Therefore, during music playback, a lower weight than usual is set for each sensor.

  Row 44 represents the weight of each sensor when no map match is performed. If the current location is uncertain, the navigation device 1 is in a so-called free state and no map match is performed. In this case, it is desirable to quickly estimate the current location and return to a state where map matching can be performed. Therefore, in the free state, a higher weight than usual is set for all sensors. As a result, the CPU 31 tries to estimate the current location as accurately as possible using more sensors.

  When the current situation corresponds to a plurality of rows in the characteristic table, the weight set for each row is multiplied to obtain the weight of each sensor. For example, when entering a tunnel during music playback, line 42 and line 43 correspond. In this case, the weight of the speed sensor is “0.8” obtained by multiplying “1” in the row 42 by “0.8” in the row 43.

  The “situation” set in the characteristic table is not limited to that described above. The situation based on the map data includes, for example, the curvature of the road, the type of road such as an expressway and a general road, the number of intersections, and the like. In addition, examples of the situation based on the processing load of the CPU include a case where an enlarged map is being displayed and a 3D display of a road is being performed.

  FIG. 4 is a flowchart of the current location estimation process. First, in step S11, detection values are acquired from the sensors 22a to 22d. At this time, the detection value is not acquired from the sensor blocked by the switch group 32. In step S12, the weight corresponding to each sensor is calculated using the characteristic table shown in FIG. In step S13, the switch group 32 is switched based on the weight calculated in step S12, and it is determined whether or not each sensor is used for estimation of the current location. In step S14, the current location is estimated based on the detection value acquired from each sensor.

According to the navigation apparatus according to the first embodiment described above, the following operational effects can be obtained.
(1) The CPU 31 acquires a plurality of detection values respectively output from the plurality of sensors 22a to 22d. Then, a weight which is an evaluation value of each sensor is calculated, and one or more sensors used for estimating the current location are selected based on the weight. Thereafter, sensors not used for estimating the current location are blocked by the switch group 32, and the current location is estimated based on the detection value output by the selected sensor. As a result, only an appropriate sensor among various sensors is used for estimation of the current location, and the amount of calculation required for estimation of the current location is reduced.

(2) The CPU 31 calculates a weight based on the map data stored in the storage device 12, the process being executed by the CPU 31, and the state of the navigation device 1. As a result, the sensor can be flexibly selected for various situations.

(3) The CPU 31 calculates the weight of each sensor based on a characteristic table storing the weight for each sensor under a predetermined condition. Thereby, it is possible to comprehensively determine whether or not each sensor should be used even in a complicated situation where a plurality of conditions overlap.

(4) The process of calculating the weight of each sensor is a general-purpose process that does not include any content specific to a specific sensor. Thus, even when another type of sensor is further added, it can be easily handled.

(5) All information necessary for calculating the weight of each sensor is stored in the characteristic table. Thereby, it is possible to easily grasp which sensor is preferentially used in which situation by simply referring to the characteristic table.

  In the first embodiment described above, the characteristic table is used to determine whether or not the sensor can be used. In the second embodiment described in detail below, a characteristic function is used instead of the characteristic table.

-Second embodiment-
First, the variables used in the characteristic function are defined as follows.
Ct: Area ratio of building polygons within a 100 m rectangle around the current location R: Curvature up to 500 meters ahead of the road where the vehicle is currently map-matched CR: Number of intersections within the 100 m rectangle around the current location Rp: Own vehicle Is the numerical value CL corresponding to the road type of the road that currently matches the map: Numerical value Fr according to the current location and the state of the navigation device Fr: 100 if free, 0 if not
E: magnitude of accumulated error (for example, absolute value of error e integrated with travel distance l)
Cam: Numerical value according to the current time

  Here, Rp is set to a smaller numerical value as the road has a reliable sensor detection value, such as 1 for a highway, 3 for a general road, and 5 for a tunnel. In addition, CL is 90 when the navigation device is displaying an enlarged map, 70 when traveling on a highway and 3D display is being performed, 50 when traveling in an urban area, and the like. The larger the number, the larger the value. In addition, Cam is a numerical value indicating which time zone the current time corresponds to among the numerical values set for each time zone. For example, 20 at 10:00 to 12:00, and 12:00 to 17:00. Is set to 40, and 17:00 to 6:00 is set to 100.

  Next, variables Map, Cpu, and CarSt including these variables are respectively defined as the following expression (1).

  Here, the variable Map includes a variable related to map data, Cpu includes a variable related to the CPU load factor, and CarSt includes a variable related to the vehicle state. If the matrices obtained by standardizing these three variables are respectively M, CP, and CS, the characteristic function J is defined by the following equation (2).

  Here, Q1 to Q3 are coefficient matrices determined in advance for each sensor. The navigation apparatus according to the present embodiment calculates a weight for each sensor using the characteristic function J, and determines whether each sensor can be used based on the weight.

According to the navigation apparatus according to the second embodiment described above, the following functions and effects can be obtained in addition to the functions and effects obtained by the navigation apparatus according to the first embodiment.
(1) The CPU 31 calculates a weight for each sensor based on a characteristic function J including a coefficient matrix determined for each sensor. Thereby, compared with the case where a characteristic table is used, the calculated weight can be adjusted more finely.

The following modifications are also within the scope of the present invention, and one or a plurality of modifications can be combined with the above-described embodiment.
(1) Instead of determining whether or not the detection value of each sensor can be used based on the weight calculated for each sensor, the magnitude of the influence of the detection value of each sensor on the current location estimation may be determined. For example, the detection value may be ignored only when the calculated weight is equal to or less than a predetermined value, or a value obtained by multiplying the detection value by the calculated weight may be used for estimation of the current location. Or you may make it the period which acquires the detection value of a sensor change with a weight.

(2) The means for determining the availability of each sensor is not limited to a table or a function. For example, with respect to relative sensors such as vibration gyros and acceleration sensors, priority may be given to an object with little accumulation error, and only one of similar sensors such as a speed sensor and a vehicle speed pulse sensor may be used depending on the running state. May be. As for the sensors similar to the above, a priority may be set for each sensor, and a sensor with a low priority may be blocked according to the size of the CPU load. When estimating the current location, the estimated current location may be compared with the detection value of each sensor, and a sensor with a small difference may be used preferentially.

(3) The CPU load factor measured by the CPU itself or the monitoring circuit may be directly used instead of determining whether the CPU load is executing a specific process. In this case, the weight of each sensor in a situation such as “when the CPU load factor is 80% or more” may be set in the characteristic table. In the characteristic function, a variable representing the CPU load factor may be introduced to set an appropriate coefficient matrix.

(4) The sensor which is the object of the present invention is not limited to the one presented in the embodiments. For example, a vehicle speed pulse sensor or a camera sensor can be used as long as the sensor can be used for estimating the current location.

  The present invention is not limited to the above-described embodiment as long as the characteristics of the present invention are not impaired, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. .

1 Navigation Device 11 Control Circuit 22a Vibration Gyro 22b Speed Sensor 22c Acceleration Sensor 22d GPS Sensor 31 CPU
32 switches

Claims (4)

Input means for inputting a plurality of detection values respectively output from a plurality of sensors;
Evaluation means for calculating an evaluation value corresponding to each of the plurality of sensors;
Selection means for selecting one or more sensors from the plurality of sensors based on the evaluation value calculated by the evaluation means;
Current location estimation means for estimating a current location based on detection values corresponding to the one or more sensors selected by the selection means;
A navigation device comprising: The navigation device according to claim 1, wherein
The evaluation unit is based on at least one of map data, a load state of the navigation device, a current location estimated by the current location estimation unit, and a detection value corresponding to the one or more sensors. A navigation device that calculates the evaluation value. The navigation device according to claim 1 or 2,
The said evaluation means calculates the said evaluation value based on the characteristic table which has the evaluation value for every said some sensor under a predetermined condition, The navigation apparatus characterized by the above-mentioned. The navigation device according to claim 1 or 2,
The navigation device according to claim 1, wherein the evaluation unit calculates the evaluation value based on a characteristic function including a coefficient determined for each of the plurality of sensors.

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