Self-position estimation device, satellite communication system, self-position estimation method

Abstract

To enable self-position estimation without acquiring vehicle speed data from a vehicle speed sensor even in an environment where radio waves of a positioning system cannot be received.SOLUTION: A self-position estimation device is provided, comprising: a detection unit for detecting structures present around a mobile body equipped with an antenna of a satellite communication device; a speed detection unit configured to detect traveling speed of the mobile body on the basis of changes in position of the mobile body with respect to the detected structures in the surroundings; and an estimation unit for estimating the self-position based on the detected traveling speed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a self-position estimation device, a satellite communication system, and a self-position estimation method.

Background Art

[0002] There is an in-vehicle satellite communication system that is mounted on a moving body such as a vehicle and can perform satellite communication at the destination or during movement. When performing satellite communication during movement, even if the current position changes, the current position is detected, and according to the current position, the direction of the antenna capable of communicating with the satellite is detected, and the antenna is directed in a direction capable of communicating with the satellite, so that a satellite corresponding to the current position can be captured. Thereby, satellite communication can be continued. As a method for detecting the current position, for example, there is a method of positioning the current position by a positioning system such as GNSS (Global Navigation Satellite System) mounted on a vehicle.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the vehicle is in an environment where GNSS radio waves cannot be received, such as inside a tunnel or between buildings, positioning using GNSS cannot be performed, so the satellite cannot be captured. Apart from the method using GNSS, there is a technology (e.g., dead reckoning) that combines the positioning results obtained by an acceleration sensor. However, since the positioning technology using dead reckoning is relative positioning, there is a problem that the error increases as the positioning time becomes longer. In order to improve the accuracy, correction using the results of periodic absolute positioning (e.g., positioning results by GNSS) is required. Therefore, for example, when movement continues in an environment where GNSS radio waves cannot be received, such as a long tunnel, the position estimation accuracy is low immediately after exiting the tunnel. In this case, there is a problem that it takes time to capture the satellite again.

[0005] There is also a method of obtaining the detection result of a vehicle speed sensor and estimating the current position based on the speed of the vehicle. However, in order to obtain vehicle speed data from the vehicle speed sensor, it is necessary to connect a satellite communication system to the connector for obtaining the vehicle speed sensor from the vehicle's ECU (Electronic Control Unit) or the like. However, at the time of vehicle inspection, it is necessary to disconnect the satellite communication system from the connector, and after the vehicle inspection is completed, it is necessary to connect it to the connector again. In addition, in order to connect the satellite communication system to such a connector, it is necessary to remove the interior panel such as the dashboard and perform operations such as connection, which is time-consuming for removal and installation.

[0006] The present invention has been made in view of such circumstances, and its object is to provide a self-position estimation device, a satellite communication system, and a self-position estimation method that can estimate the self-position in an environment where radio waves of a positioning system cannot be received and without obtaining vehicle speed data from a vehicle speed sensor.

Means for Solving the Problems

[0007] In order to solve the above-described problems, one aspect of the present invention is a self-position estimation device including a surrounding situation detection unit that detects a structure existing around a moving body on which an antenna of a satellite communication device is mounted, a speed detection unit that detects a moving speed of the moving body based on a change in the position of the moving body with respect to the detected surrounding structure, and an estimation unit that estimates its own position based on the detected moving speed.

[0008] Also, one aspect of the present invention is a self-position estimation method in which a surrounding situation detection unit detects a structure existing around a moving body on which an antenna of a satellite communication device is mounted, a speed detection unit detects a moving speed of the moving body based on a change in the position of the moving body with respect to the detected surrounding structure, and an estimation unit detects the moving speed of the moving body based on the change in the position of the moving body with respect to the detected surrounding structure.

Advantages of the Invention

[0009] As described above, according to the present invention, it is possible to estimate the self-position in an environment where radio waves of the positioning system cannot be received and without acquiring vehicle speed data from a vehicle speed sensor.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, a satellite communication system according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram showing the configuration of a satellite communication system according to an embodiment of the present invention. The satellite communication system S is an in-vehicle satellite communication system mounted on a moving object such as a vehicle and capable of performing satellite communication at the destination or during movement. Taking the case where the moving object is a vehicle as an example, it may also be a movable robot.

[0012] The satellite communication system S includes a self-position estimation unit 10, a positioning unit 11, an attitude control unit 12, a storage unit 12a, an antenna drive unit 13, a satellite communication antenna 14, a communication unit 15, a communication processing unit 16, an input unit 17, and an output unit 18.

[0013] The self-position estimation unit 10 includes a surrounding situation detection unit 101, a speed detection unit 102, and an estimation unit 103.

[0014] The surrounding situation detection unit 101 detects structures existing around the moving object on which the antenna of the satellite communication device is mounted. The surrounding situation detection unit 101 includes a camera 101a and a LiDAR 101b. Using the camera 101a and the LiDAR 101b, the self-position estimation unit 10 detects structures existing around the moving object by SLAM (Simultaneous Localization and Mapping). Here, the structures are buildings and installed objects, which are fixed and installed objects without moving. In the detection results of the surrounding situation detected by the camera 101a and the LiDAR 101b, in addition to the fixed structures, moving objects (other vehicles, people, etc.) may also be detected. However, a process of extracting the structures may be performed, or the structures may be detected by performing a process of excluding the moving objects.

[0015] Further, the surrounding situation detection unit 101 calculates the distance between the moving object and objects such as structures and installations around it by SLAM, and obtains the change in the distance with respect to the object over time.

[0016] For example, when the surrounding situation detection unit 101 uses the camera 101a, it extracts the feature points of an object (e.g., a structure) included in the image captured of the surroundings of the moving body, and calculates the distance to the feature points based on the change in the video due to the change in the distance and angle from the camera 101a. Such calculation of the distance using the camera 101a may be performed by using the technology of Visual SLAM. The camera 101a may be a monocular camera or a stereo camera with compound eyes.

[0017] Also, when the surrounding situation detection unit 101 uses the LiDAR 101b, it emits a laser beam and receives the reflected light, and measures the distance to the surrounding object (e.g., a structure) based on the time from emission to reception. The detection result of the LiDAR 101b is point cloud data of three-dimensional data (X, Y, Z coordinates). The measurement of the distance using the LiDAR 101b may be performed by using the technology of LiDAR SLAM.

[0018] Also, the surrounding situation detection unit 101 may use a depth camera as the camera 101a and a ToF (Time Of Flight) sensor as the LiDAR 101b to measure the distance to an object (e.g., a structure) existing in the surroundings. When measuring the distance using such a camera 101a and LiDAR 101b, the technology of Depth SLAM may be used. When using the technology of Depth SLAM, even in an environment where there are few feature points that can be obtained only by the camera 101a or in a dark environment, SLAM can be executed and the distance to the surrounding objects can be measured.

[0019] The speed detection unit 102 detects the moving speed of the moving body based on the change in the distance to the surrounding objects measured by the surrounding situation detection unit 101 over time. For example, the speed detection unit 102 acquires the detection result of the surrounding situation detection unit 101 and detects the moving speed of the moving body based on the change in the position of the moving body with respect to the surrounding structures. In this way, the speed detection unit 102 detects the speed of the moving object based on how much the distance to the surrounding structures relative to the moving object changes over time. The speed detection unit 102 may be provided separately from the surrounding situation detection unit 101, or may be combined with the surrounding situation detection unit 101 and realized as a SLAM function.

[0020] The estimation unit 103 estimates its own position based on the detected moving speed. The estimation unit 103 estimates its own position based on the moving speed detected by the speed detection unit 102 and the direction of the moving object with respect to the structure based on the result obtained by SLAM. For example, starting from the position of the moving object finally obtained by the positioning unit 11, the position of the moving object can be estimated based on the changes in the moving speed and the moving direction obtained by the self-position estimation unit 10. Therefore, even when SLAM is used in the self-position estimation unit 10, it is not necessary to pre-store the surrounding map.

[0021] The positioning unit 11 obtains the position of the satellite communication system S based on information such as the position of the satellite transmitted from the positioning satellite and the signal transmission time. The positioning unit 11 may perform positioning by means of the function of GNSS (Global Navigation Satellite System).

[0022] The attitude control unit 12 controls the attitude of the satellite communication antenna 14 based on the self-position estimation result obtained from the positioning unit 11 or the self-position estimation unit 10. The attitude control unit 12 identifies the direction in which the satellite communication antenna 14 is to be directed according to the estimated self-position based on the result of the estimated self-position, and outputs a drive signal to the antenna drive unit 13 so that the direction becomes the specified direction, thereby controlling the attitude of the satellite communication antenna 14. By directing the satellite communication antenna 14 in the direction corresponding to the orientation data, the communication satellite can be captured. Thereby, even if positioning based on GNSS becomes impossible, the satellite can be tracked.

[0023] The storage unit 12a stores attitude data in which position data indicating the position of the moving body and orientation data indicating the orientation of the antenna are associated with each other. The storage unit 12a is configured by a storage medium, for example, an HDD (Hard Disk Drive), a flash memory, an EEPROM (Electrically Erasable Programmable Read Only Memory), a RAM (Random Access read / write Memory), a ROM (Read Only Memory), or an arbitrary combination of these storage media. For example, a non-volatile memory can be used for this storage unit 12a.

[0024] The above-described surrounding situation detection unit 101, speed detection unit 102, estimation unit 103, positioning unit 11, and attitude control unit 12 may be configured by a processing device such as a CPU (Central Processing Unit) or a dedicated electronic circuit.

[0025] Returning to FIG. 1, the description will be continued. The antenna drive unit 13 is a motor or the like for changing the attitude of the satellite communication antenna 14. Based on the control signal output from the attitude control unit 12, the antenna drive unit 13 drives a motor or the like to change the attitude of the satellite communication antenna 14. The antenna drive unit 13 changes the attitude of the satellite communication antenna 14 by changing the angle in the horizontal direction with respect to the moving body and the elevation angle.

[0026] The satellite communication antenna 14 transmits and receives radio waves to and from a satellite for satellite communication. The satellite communication antenna 14 is installed, for example, on the upper surface of the moving body.

[0027] The communication unit 15 outputs reception data corresponding to the reception signal received from the satellite for satellite communication via the satellite communication antenna 14 to the communication processing unit 16. Also, the communication unit 15 causes the satellite communication antenna 14 to transmit a transmission signal corresponding to the transmission data output from the communication processing unit 16. The communication processing unit 16 performs processing according to the received data acquired from the communication unit 15, and based on the processing result, performs various types of processing. For example, the communication processing unit 16 outputs various types of data from the output unit 18 based on the processing result. Also, the communication processing unit 16 outputs various types of input data or input signals input from the input unit 17 to the communication unit 15 as transmission data.

[0028] FIG. 2 is a diagram showing an example of the attitude data stored in the storage unit 12a. The attitude data stores attitude data in which position data indicating the position of the moving body and orientation data indicating the orientation in which the antenna is directed are associated with each other. The attitude data may be data in which orientation data is associated for each position, or may be data in which orientation data is associated for each area. In this FIG. 2, the case where area data indicating an area and orientation data are associated with each other is illustrated.

[0029] Next, the operation of the satellite communication system S will be described. FIG. 3 is a flowchart for explaining the operation of the satellite communication system S. First, the positioning unit 11 positions the current position of the moving body on which the satellite communication system S is mounted by GNSS (step S101). The attitude control unit 12 controls the attitude of the antenna based on the current position measured by the positioning unit 11 (step S102). Here, the attitude control unit 12 reads out the orientation data corresponding to the measured position by referring to the attitude data stored in the storage unit 12a. Then, the attitude control unit 12 outputs a drive signal to the antenna drive unit 13 based on the read orientation data, thereby controlling the attitude of the satellite communication antenna 14. Thereby, based on the current position obtained by positioning using GNSS, by changing the attitude of the satellite communication antenna 14 to a direction in which a signal from the satellite can be received, a satellite for satellite communication can be captured.

[0030] Next, after a certain waiting time has elapsed, the attitude control unit 12 determines whether positioning based on GNSS can be performed by the positioning unit 11 (step S103). If the determination result of the attitude control unit 12 is that positioning by GNSS is possible (when a positioning result is obtained from the positioning unit 11) (step S103 - YES), the satellite communication system S determines whether an instruction to turn off the power has been input (step S111). If an instruction to turn off the power has been input (step S111 - YES), the satellite communication system S ends the process. On the other hand, if an instruction to turn off the power has not been input (step S111 - NO), the satellite communication system S proceeds to step S101. Thereby, new positioning is performed by GNSS, and based on the result, the attitude of the satellite communication antenna 14 is controlled. When the radio wave from the positioning satellite can be received by GNSS, the satellite communication antenna 14 can be directed in the direction where the radio wave from the satellite for satellite communication can be received based on the position information obtained from the positioning unit 11, enabling the satellite to be tracked.

[0031] On the other hand, in step S103, if positioning by GNSS is not possible (when a positioning result cannot be obtained from the positioning unit 11 or the positioning result indicates that positioning is impossible) (step S103 - NO), the self - position estimation unit 10 acquires from the positioning unit 11 the positioning result of the last position that could be measured by the positioning unit 11 (step S104). Examples of cases where positioning by GNSS is not possible include when the moving body is traveling in a tunnel or when there are building groups around the moving body in the city center. In such cases, the process proceeds to detecting the surrounding structures using the camera 101a and LiDAR 101b and detecting the speed based on the Doppler effect.

[0032] For example, the positioning unit 11 has a function of temporarily storing the positioning result obtained immediately before the time when radio waves from satellites for GNSS positioning can no longer be received. The self-position estimation unit 10 can obtain the positioning result immediately before the time when radio waves from satellites for GNSS positioning can no longer be received (the last obtained positioning result) by reading out this temporarily stored positioning result.

[0033] Next, the surrounding situation detection unit 101 performs position measurement by SLAM (step S105). The speed detection unit 102 refers to the result of the position measurement of the surrounding situation detection unit 101 obtained every time the predetermined acquisition interval arrives based on the predetermined acquisition interval, and detects the speed based on the time result of the position measurement. The estimation unit 103 estimates the current direction from the history of changes in the direction of the moving body based on the detection result of the surrounding situation detection unit 101 (step S106). Then, the estimation unit 103 estimates the position of the moving body based on the moving speed detected by the speed detection unit 102 and the direction of the moving body with respect to the structure according to the result obtained by SLAM (step S107). Here, the latitude, longitude, and azimuth of the moving body can be obtained as the estimation result of the position.

[0034] The attitude control unit 12 refers to the storage unit 12a and reads out the direction data corresponding to the self-position estimation result obtained from the self-position estimation unit 10 (step S108). Here, the attitude control unit 12 specifies the area to which the self-position belongs among the estimated area data stored in the storage unit 12a, and reads out the direction data corresponding to the specified area. When the orientation data is read, the attitude control unit 12 controls the attitude of the satellite communication antenna 14 based on the orientation data (step S109). As a result, even when it becomes impossible to receive GNSS radio waves and positioning by the positioning unit 11 becomes impossible, the speed of the moving body can be detected by the self-position estimation unit 10, and the position (latitude, longitude, and azimuth) of the moving body can be estimated based on the detected speed. Therefore, the satellite communication antenna 14 can be continuously directed toward the satellite side. Then, when the moving body moves out of the building group and becomes able to receive GNSS radio waves again, it also becomes possible to receive radio waves from the satellite for satellite communication. Here, since the orientation of the satellite communication antenna 14 is directed toward the satellite side by the processing from step S104 to step S109, satellite communication can be resumed promptly. Then, when the position of the moving body is measured by the positioning unit 11, the satellite communication antenna 14 can be tracked with respect to the satellite for satellite communication based on the measurement result.

[0035] Also, here, when the moving body is traveling in a tunnel, by storing map data, etc. in advance, the attitude control unit 12 may determine which tunnel entrance the moving body has entered and estimate the position of the exit corresponding to that entrance. In this case, even if the surrounding situation detection unit 101 has not necessarily detected the speed of the moving body, the orientation data corresponding to the position of the exit can be read from the storage unit 12a, and the attitude of the satellite communication antenna 14 can be controlled.

[0036] On the other hand, when the moving body is traveling on a road among a building group, depending on the positions and shapes of the buildings in the building group, the relative positions between the position where the moving body is traveling and the building group, etc., the positions where communication with the satellite for satellite communication can be resumed are different. In this case, it is difficult to specify in advance the positions where communication can be resumed. In such a case, since the attitude of the satellite communication antenna 14 is controlled based on the orientation data, even while the radio waves of GNSS cannot be received (while communication with the satellite for satellite communication is impossible), the orientation of the satellite communication antenna 14 can be directed toward the satellite for satellite communication so that communication is possible. As a result, when radio waves from the satellite for satellite communication can be received within the building group, or when the moving body has passed through the building group, communication with the satellite for satellite communication can be promptly resumed. Therefore, after the moving body enters the building group and becomes capable of communicating with the satellite for satellite communication, there is no need to newly search for the position of the satellite for satellite communication, so satellite communication can be promptly resumed. In addition, since it is not necessary to temporarily stop the moving body to newly search for the position of the satellite for satellite communication, the time for stopping can be shortened. Also, since there is no need to newly search for the position of the satellite for satellite communication, even when the automatic driving technology is used for the moving body, it is not necessary to stop for re-capture, etc., and the complexity of the control related to automatic driving can be reduced. Also, regarding a tunnel, when there is a branch in the middle of the tunnel and there are multiple exits, the position of the exit of the tunnel corresponding to the position of the entrance of the tunnel cannot be specified. Even in such a case, by estimating the self-position by the surrounding situation detection unit 101, communication can be promptly resumed when communication with the satellite for satellite communication becomes possible.

[0037] Thereafter, the satellite communication system S determines whether an instruction to turn off the power has been input (step S110). If an instruction to turn off the power has been input (step S110 - YES), the satellite communication system S ends the process. If an instruction to turn off the power has not been input (step S110 - NO), the process proceeds to step S103.

[0038] In the above-described embodiment, the surrounding situation detection unit 101 performs the estimation process of the position of the moving object from the time when the positioning by the positioning unit 11 becomes impossible. However, while the positioning by the positioning unit 11 is possible, the positioning result is acquired from the positioning unit 11 at regular intervals, and the current position is estimated from the change in the surrounding situation using the position indicated by the acquired positioning result, and the estimation result may be output to the attitude control unit 12. In this case, when the positioning result representing the current position is obtained from the positioning unit 11, the attitude control unit 12 can control the attitude of the satellite communication antenna 14 based on the current position obtained from the positioning unit 11. Then, when the situation becomes such that the radio wave of GNSS cannot be received and the current position cannot be measured by the positioning unit 11, the surrounding situation detection unit 101 estimates the position of the moving object based on the result of detecting the surrounding using the positioning result last measured by the positioning unit 11. The attitude control unit 12 may control the attitude of the satellite communication antenna 14 based on the position estimated by the surrounding situation detection unit 101.

[0039] Also, in the above-described embodiment, when the positioning cannot be performed by the positioning unit 11, based on the detection result obtained from the surrounding situation detection unit 101, how much the position of the moving object has changed relative to the surrounding structures, the speed, the moving direction, etc. of the moving object can be detected. Thereby, the speed of the moving object can be detected without using a vehicle speed sensor. Also, by acquiring the moving direction from the surrounding situation detection unit 101, the moving direction can also be grasped. Therefore, even in a situation where positioning is impossible, the self-position of the moving object can be estimated more accurately than when using a vehicle speed sensor.

[0040] The self-position estimation unit 10, the positioning unit 11, and the attitude control unit 12 in the above-described embodiments may be implemented by a computer. In that case, a program for realizing this function may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to realize it. Here, the "computer system" shall include hardware such as an OS and peripheral devices. Further, the "computer-readable recording medium" refers to a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, etc., and a storage device such as a hard disk built in a computer system. Furthermore, the "computer-readable recording medium" also includes those that dynamically hold a program for a short time, such as a communication line when transmitting a program via a network such as the Internet or a communication line such as a telephone line, and those that hold a program for a certain period of time, such as a volatile memory inside a computer system that serves as a server or a client in that case. Also, the above program may be for realizing a part of the above-described functions, and may further be realized in combination with a program already recorded in a computer system for the above-described functions, or may be realized using a programmable logic device such as an FPGA (Field Programmable Gate Array).

[0041] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and designs and the like within the scope not departing from the gist of the present invention are also included.

Explanation of Reference Numerals

[0042] S Satellite communication system 10 Self-position estimation unit 11 Positioning unit 12 Attitude control unit 12a Storage unit 13 Antenna drive unit 14 Antenna for satellite communication 15 Communication unit 16 Communication processing unit 17 Input unit 18 Output unit

Claims

1. A surrounding situation detection unit that detects structures existing around a moving body on which an antenna of a satellite communication device is mounted; A speed detection unit that detects the moving speed of the moving body based on a change in the position of the moving body with respect to the detected surrounding structures; An estimation unit that estimates its own position based on the detected moving speed An own-position estimation device having the above.

2. The surrounding situation detection unit detects structures existing around by SLAM (Simultaneous Localization and Mapping), The estimation unit estimates its own position based on the moving speed detected by the speed detection unit and the orientation of the moving body with respect to the structures obtained by the SLAM The own-position estimation device according to Claim 1.

3. The moving body is a vehicle The own-position estimation device according to Claim 1.

4. The own-position estimation device according to any one of Claims 1 to 3, and An attitude control unit that controls the attitude of an antenna for performing satellite communication based on the own-position estimation result obtained from the own-position estimation device A satellite communication system having the above.

5. A surrounding situation detection unit detects structures existing around a moving body on which an antenna of a satellite communication device is mounted; A speed detection unit detects the moving speed of the moving body based on a change in the position of the moving body with respect to the detected surrounding structures based on the detected result; An estimation unit detects the moving speed of the moving body based on a change in the position of the moving body with respect to the detected surrounding structures An own-position estimation method.

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