Position estimation device

Abstract

To provide a position estimation device capable of suppressing an estimation position from lowering in precision when a moving body changes positioning means.SOLUTION: A position estimation device 200 is configured to estimate a self-location based upon absolute positioning sensor information by an absolute positioning sensor 20 and relative positioning sensor information by a relative positioning sensor 30 detecting change in position of a moving body 1, and the position estimation device 200 comprises: an absolute positioning location calculation part 50 which calculates the absolute positioning location of the moving body 1 based upon the absolute positioning sensor information; a relative positioning trajectory calculation part 60 which calculates the relative positioning trajectory of the moving body 1, based upon the absolute positioning location, on the basis of the relative positioning sensor information; and a relative positioning trajectory comparison part 90 which outputs the latest location of the moving body 1 on a selected relative positioning trajectory as an estimated location of the moving body 1 when the relative positioning trajectory meets relative positioning trajectory selection conditions.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This application relates to a position estimation device. Place

Background Art

[0002] Various position estimation techniques have been developed, such as position estimation techniques using positioning satellites such as GPS (Global Positioning System), GNSS (Global Navigation Satellite System), and QZSS (Quasi-Zenith Satellite System), position estimation techniques using the transmission time or electric field strength of radio waves from multiple wireless LAN base stations or mobile phone base stations, and position estimation techniques using infrared rays.

[0003] However, for example, in the case of position estimation using positioning satellites, there are positioning errors caused by delays in the ionosphere of signals, multipath due to buildings, etc., and interruption of signals. To reduce the influence of this positioning error, there are techniques such as dead reckoning for estimating the relative position of a moving object. Dead reckoning is a technique for performing position estimation mainly using the angular velocity obtained from a gyro sensor and the vehicle speed obtained from a vehicle speed sensor. On the other hand, when starting dead reckoning based on a satellite positioning position with reduced accuracy, there is a problem that the accuracy of the positioning position by dead reckoning also decreases at the same time.

[0004] Regarding these problems, in the position detection device described in Patent Document 1, a relative trajectory based on dead reckoning is estimated and held starting from each satellite positioning position, so that when the positioning signal transmitted from the positioning satellite is interrupted, the relative trajectory before the increase in satellite positioning error is inherited and the estimated position based on dead reckoning is calculated, thereby suppressing the decrease in the accuracy of the estimated position by dead reckoning.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] According to the position detection device described in Patent Document 1, the estimated position is calculated based on dead reckoning by inheriting the relative trajectory before the increase in satellite positioning error, and the position estimation by dead reckoning continues. However, the updating and rejection of the relative trajectory are performed sequentially, and when entering an area where satellite positioning is impossible, the options for relative trajectories to continue dead reckoning are limited, which may lead to a decrease in the accuracy of dead reckoning.

[0007] This disclosure was made to solve the above-mentioned problems, and aims to provide a position estimation device and position estimation method that can suppress the decrease in the accuracy of the estimated position even when absolute positioning, such as satellite positioning, is not possible. [Means for solving the problem]

[0008] The position estimation device disclosed herein is A position estimation device that estimates its own position based on absolute positioning sensor information acquired by an absolute positioning sensor mounted on a moving object and receiving multiple signals emitted from known positions, and relative positioning sensor information acquired by a relative positioning sensor mounted on the moving object and detecting changes in the relative position of the moving object, An absolute positioning position calculation unit calculates the absolute position of the moving object based on the absolute positioning sensor information, A relative positioning trajectory calculation unit calculates the relative positioning trajectory of the moving object based on the relative positioning sensor information, with respect to the absolute positioning position, and has a relative positioning trajectory storage area that stores the calculated relative positioning trajectory. The system includes a relative positioning trajectory comparison unit that, when the relative positioning trajectory satisfies predetermined relative positioning trajectory selection conditions, outputs the latest position of the moving object on the selected relative positioning trajectory as the estimated position of the moving object. 、 The relative positioning trajectory calculation unit repeats the process of storing the latest relative positioning trajectory in the relative positioning trajectory storage area each time the latest relative positioning trajectory based on the relative positioning sensor information satisfies the relative positioning trajectory retention conditions, updating the past relative positioning trajectories stored in the relative positioning trajectory storage area with the latest relative positioning trajectory. If the latest relative positioning trajectory does not satisfy the predetermined relative positioning trajectory retention conditions, the latest relative positioning trajectory is deleted without being stored in the relative positioning trajectory storage area. The absolute positioning position calculation unit has an absolute positioning position storage area capable of storing the calculated absolute positioning position, calculates the absolute positioning trajectory of the moving object based on a plurality of absolute positioning positions stored in the absolute positioning position storage area, and updates the latest position of the moving object on the absolute positioning trajectory as the absolute positioning position based on the absolute positioning sensor information. The absolute positioning position calculation unit calculates an absolute positioning trajectory confidence level representing the reliability of the absolute positioning trajectory, and the relative positioning trajectory calculation unit determines that the relative positioning trajectory calculation conditions are satisfied if the absolute positioning trajectory confidence level is equal to or greater than a preset threshold confidence level. The absolute positioning trajectory reliability is calculated using at least one of the following as an indicator: the estimation error occurring at each of the multiple absolute positioning positions used to calculate the absolute positioning trajectory; the positional error of each of the multiple absolute positioning positions used to calculate the absolute positioning trajectory relative to the relative positioning trajectory; and the distance the moving body traveled while calculating the multiple absolute positioning positions used to calculate the absolute positioning trajectory. . [Effects of the Invention]

[0010] The position estimation device and position estimation method disclosed herein have the effect of enabling high-precision position estimation to be continued using a more reliable relative positioning trajectory, even when absolute positioning becomes impossible while a moving object is in motion, by continuously maintaining and updating the relative positioning trajectory and relative positioning trajectory reliability based on relative positioning sensor information acquired from a relative positioning sensor, using the absolute positioning position as a reference. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing a mobile body equipped with a position estimation device according to Embodiment 1, and a positioning system for the mobile body. [Figure 2] This is a block diagram showing the configuration of the position estimation device according to Embodiment 1. [Figure 3] This flowchart schematically shows the contents of the position estimation process according to the position estimation method of Embodiment 1. [Figure 4] This flowchart schematically shows the process for calculating absolute positioning trajectory reliability using the position estimation method according to Embodiment 1. [Figure 5] This flowchart schematically shows the process for calculating the relative positioning trajectory reliability using the position estimation method according to Embodiment 1. [Figure 6] This is a schematic diagram illustrating an example of the operation of the position estimation device according to Embodiment 1. [Figure 7] This is a schematic diagram illustrating another example of the operation of the position estimation device according to Embodiment 1. [Figure 8] This figure shows an example of the hardware of a position estimation device according to Embodiment 1. [Modes for carrying out the invention]

[0012] The objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings. Embodiment 1. FIG. 1 is a schematic diagram showing a moving body 1 equipped with a position estimation device 200 according to Embodiment 1 and the entire positioning system for the moving body 1.

[0013] The moving body 1 is equipped with a position estimation device 200 according to Embodiment 1, an absolute positioning sensor 20 used for absolute positioning of the moving body 1, and a relative positioning sensor 30 used for relative positioning of the moving body 1. In FIG. 1, the case of satellite positioning by receiving satellite signals from a plurality of positioning satellites 2 is shown as an example of absolute positioning means by receiving a plurality of signals radiated from a known position.

[0014] <Configuration of the Position Estimation Device According to Embodiment 1> FIG. 2 is a block diagram showing the configuration of a position estimation device 200 according to Embodiment 1. The position estimation device 200 according to Embodiment 1 includes an absolute positioning position calculation unit 50, a relative positioning trajectory calculation unit 60, a surrounding environment estimation unit 70, a traveling state estimation unit 80, and a relative positioning trajectory comparison unit 90.

[0015] An absolute positioning position storage area 51 is provided inside the absolute positioning position calculation unit 50, and a relative positioning trajectory storage area 61 is provided inside the relative positioning trajectory calculation unit 60.

[0016] The absolute positioning sensor information acquired by the absolute positioning sensor 20 provided outside the position estimation device 200 according to Embodiment 1 and the relative positioning sensor information acquired by the relative positioning sensor 30 also provided outside are respectively output to the position estimation device 200 according to Embodiment 1.

[0017] The absolute positioning sensor 20 is composed of, for example, at least one or more of a GNSS receiver 21, a UWB receiver 22, an infrared receiver 23, a wireless LAN receiver 24, etc.

[0018] The relative positioning sensor 30 is composed of at least one of the following: a gyro sensor 31, a wheel speed sensor 32, an acceleration sensor 33, a camera 34, and so on.

[0019] In the example of the position estimation device 200 according to Embodiment 1 shown in Figure 2, the absolute positioning sensor 20 and the relative positioning sensor 30 are mounted outside the position estimation device 200, but they may also be mounted inside the position estimation device 200. For example, even if a gyro sensor 31, which is an example of a relative positioning sensor 30, is mounted inside the position estimation device 200, the position estimation device 200 according to Embodiment 1 can obtain the same effect with respect to position estimation.

[0020] The following describes the basic functions of the absolute positioning position calculation unit 50, relative positioning trajectory calculation unit 60, surrounding environment estimation unit 70, driving state estimation unit 80, and relative positioning trajectory comparison unit 90, which constitute the position estimation device 200 according to Embodiment 1. More detailed functions will be described in the description of the operation of the position estimation device 200 according to Embodiment 1.

[0021] The absolute positioning calculation unit 50 calculates the absolute position of the moving object 1 based on the absolute positioning sensor information acquired from the absolute positioning sensor 20. The calculated absolute positioning position is stored in the absolute positioning position storage area 51 located inside the absolute positioning position calculation unit 50. The absolute positioning position calculation unit 50 also calculates the absolute positioning trajectory reliability, which represents the reliability of the absolute positioning trajectory.

[0022] The relative positioning trajectory calculation unit 60 determines whether the absolute positioning trajectory confidence level calculated by the absolute positioning position calculation unit 50 is equal to or greater than a preset threshold confidence level.

[0023] The surrounding environment estimation unit 70 estimates the driving environment around the moving object 1 based on absolute positioning sensor information and relative positioning sensor information acquired from the absolute positioning sensor 20 and relative positioning sensor 30, respectively.

[0024] The driving state estimation unit 80 estimates the driving state of the mobile body 1 based on relative positioning sensor information acquired from the relative positioning sensor 30.

[0025] The relative positioning trajectory comparison unit 90 compares the reliability of the relative positioning trajectories calculated and stored by the relative positioning trajectory calculation unit 60, selects the relative positioning trajectory with the highest relative positioning trajectory reliability, and outputs the absolute position on that relative positioning trajectory (hereinafter also referred to as the latest position of the mobile body 1) as the estimated position of the mobile body 1.

[0026] <Operation of the position estimation device according to Embodiment 1> The general outline of the processing performed by the position estimation device 200 according to Embodiment 1 will be explained below using the flowcharts shown in Figures 3 to 5.

[0027] In the position estimation device 200, the position estimation process shown in the flowchart of Figure 3 is repeated. In step S301, the absolute positioning position calculation unit 50 calculates the absolute position of the moving object 1 based on the absolute positioning sensor information acquired from the absolute positioning sensor 20. The calculated absolute position is then stored in the absolute positioning position storage area 51. The absolute position stored in the absolute positioning position storage area 51 includes information related to positioning accuracy, such as the degree of convergence of carrier wave estimation in satellite positioning. After the processing in step S301, the process proceeds to step S302.

[0028] In step S302, the surrounding environment estimation unit 70 estimates the driving environment around the mobile body 1 based on the absolute positioning sensor information and relative positioning sensor information acquired from the absolute positioning sensor 20 and relative positioning sensor 30, respectively. It also stores, or retains, the calculated information about the driving environment in the absolute positioning location storage area 51. In other words, the processing in step S302 estimates the driving environment around the mobile body 1.

[0029] For example, based on the distribution of elevation angles of positioning satellites 2 whose received signal strength is above a preset threshold, among the multiple positioning satellites 2 being positioned by the GNSS receiver 21, the sky ratio, which represents the proportion of unobstructed space around the moving object 1, is roughly calculated. The calculated sky ratio may be stored in the absolute positioning location memory area 51.

[0030] Generally, when the sky ratio is low, satellite positioning accuracy decreases due to factors such as a decrease in the number of positioning satellites 2 or an increase in multipath. Also, for example, if a camera 34 is installed in front of the mobile body 1, the presence and position of surrounding obstructions along the travel path of the mobile body 1 may be detected in advance using the camera 34 and stored in the absolute positioning location memory area 51. Examples of obstructions include tall buildings, bridges, road sound barriers, mountains, trucks, or other mobile bodies 1 such as buses. After processing in step S302, the process proceeds to step S303.

[0031] In step S303, the absolute positioning location calculation unit 50 refers to the absolute positioning location storage area 51, and if the number of absolute positioning locations stored in the absolute positioning location storage area 51 is equal to or greater than a preset threshold number, it calculates the absolute positioning trajectory of the mobile body 1 based on the stored absolute positioning locations and updates the absolute position of the mobile body 1 (the latest position of the mobile body 1) on the absolute positioning trajectory as the absolute positioning location.

[0032] Furthermore, the calculation of the absolute positioning trajectory of the moving object 1 may be based on information regarding the positioning accuracy of the absolute positioning location stored in the absolute positioning location storage area 51. The absolute positioning location calculation unit 50 also calculates the absolute positioning trajectory reliability, which represents the reliability of the absolute positioning trajectory. Details of the method for calculating the absolute positioning trajectory reliability will be described later. After the processing in step S303, the process proceeds to step S304.

[0033] In step S304, the absolute positioning location calculation unit 50 deletes the information regarding the absolute positioning location used to calculate the absolute positioning trajectory from the absolute positioning location storage area 51. Performing this process makes it possible to reduce the size of the absolute positioning location storage area 51 required to hold the absolute positioning location. After the processing in step S304, the process proceeds to step S305.

[0034] In step S305, the relative positioning trajectory calculation unit 60 determines whether the absolute positioning trajectory confidence level calculated by the absolute positioning position calculation unit 50 is equal to or greater than a preset threshold confidence level. This determination condition is called the relative positioning trajectory calculation condition. If the absolute positioning trajectory confidence level is equal to or greater than the threshold confidence level, the result is YES, and the process proceeds to step S306. On the other hand, if the absolute positioning trajectory confidence level is less than the threshold confidence level, the result is NO, and the process proceeds to step S309.

[0035] In step S306, the relative positioning trajectory calculation unit 60 refers to the relative positioning trajectory storage area 61 and determines whether the confidence level of all stored relative positioning trajectories is below the threshold confidence level if relative positioning trajectories are already stored in the relative positioning trajectory storage area 61. This determination condition is called the relative positioning trajectory storage condition. If the confidence level of all stored relative positioning trajectories is below the threshold confidence level, the result is YES, and the process proceeds to step S307. On the other hand, if the confidence level of any one of the stored relative positioning trajectories is equal to or greater than the threshold confidence level, the result is NO, and the process proceeds to step S309. This suppresses the calculation of unnecessary relative positioning trajectories, resulting in reduced memory capacity and processing load.

[0036] In step S307, the driving state estimation unit 80 estimates the driving state of the mobile body 1 based on relative positioning sensor information acquired from the relative positioning sensor 30. For example, based on the rotation detection result of the mobile body 1 by the gyro sensor 31 and the left and right wheel speed difference detection result by the wheel speed sensor 32, it is estimated that the mobile body 1 is turning. In addition, for example, the vibration state or acceleration / deceleration state of the mobile body 1 is estimated based on the detection result of the acceleration sensor 33. In other words, in the processing of step S307, the driving state of the mobile body 1 is estimated.

[0037] In step S308, the relative positioning trajectory calculation unit 60 calculates the relative positioning trajectory of the moving object 1 based on the relative positioning sensor information acquired from the relative positioning sensor 30, using the absolute positioning position as a reference. The relative positioning trajectory calculation unit 60 also calculates the relative positioning trajectory reliability, which represents the reliability of the relative positioning trajectory. Details of the method for calculating the relative positioning trajectory reliability will be described later. After processing in step S308, the process proceeds to step S309.

[0038] In step S309, the relative positioning trajectory calculation unit 60 refers to the relative positioning trajectory storage area 61. If a relative positioning trajectory is already stored in the relative positioning trajectory storage area 61, it updates the relative positioning trajectory based on the relative positioning sensor information obtained from the relative positioning sensor 30, using the relative position on the relative positioning trajectory as a reference. It also updates the relative positioning trajectory reliability, which represents the reliability of the relative positioning trajectory. After processing in step S309, the process proceeds to step S310.

[0039] In step S310, the relative positioning trajectory calculation unit 60 determines whether the relative positioning trajectory confidence level calculated by the relative positioning trajectory calculation unit 60 is equal to or greater than the threshold confidence level. If the relative positioning trajectory confidence level is equal to or greater than the threshold confidence level, the result is YES, and the process proceeds to step S311. On the other hand, if the relative positioning trajectory confidence level is less than the threshold confidence level, the result is NO, and the process proceeds to step S313.

[0040] In step S311, the relative positioning trajectory calculation unit 60 refers to the relative positioning trajectory storage area 61 and determines whether the number of stored relative positioning trajectories is less than a preset threshold number. If the number of stored relative positioning trajectories is less than the threshold number, the result is YES and the process proceeds to step S312. If the number of stored relative positioning trajectories is equal to or greater than the threshold number, the result is NO and the process proceeds to step S313.

[0041] In step S312, the calculated or updated relative positioning trajectory is stored in the relative positioning trajectory storage area 61. At this time, for newly calculated relative positioning trajectories, the information regarding the driving environment estimated by the surrounding environment estimation unit 70 in step S302 and the driving state of the mobile body 1 at the time of calculation of the relative positioning trajectory estimated by the driving state estimation unit 80 in step S307 are stored in the relative positioning trajectory storage area 61 as information regarding the relative positioning trajectory.

[0042] In step S313, the relative positioning trajectory calculation unit 60 compares the relative positioning trajectory reliability of the target relative positioning trajectory with the relative positioning trajectory reliability of other relative positioning trajectories stored in the relative positioning trajectory memory area 61 to determine the ranking of relative positioning trajectory reliability. If the ranking of relative positioning trajectory reliability satisfies the preset acceptable ranking conditions, the result is YES, and the process proceeds to step S312. If the ranking of relative positioning trajectory reliability does not satisfy the preset acceptable ranking conditions, the result is NO, and the process proceeds to step S314.

[0043] In step S314, the relative positioning trajectory calculation unit 60 deletes the calculated or updated relative positioning trajectory. This reduces the memory capacity.

[0044] The relative positioning trajectory calculation unit 60 repeatedly performs the processes from step S310 to step S314 for the total number of n relative positioning trajectories that have been calculated and updated. After the processes from step S310 to step S314 have been completed, the unit proceeds to the process in step S315.

[0045] In step S315, the relative positioning trajectory comparison unit 90 compares the reliability of the relative positioning trajectories calculated and stored by the relative positioning trajectory calculation unit 60, selects the relative positioning trajectory with the highest relative positioning trajectory reliability, and outputs the absolute position (latest position of the mobile body 1) on that relative positioning trajectory as the estimated position of the mobile body 1. These selection conditions are called relative positioning trajectory selection conditions. The above is an overview of the processing performed by the position estimation device 200 according to Embodiment 1.

[0046] <Method for calculating absolute positioning trajectory confidence> The specific processing steps for calculating the absolute positioning trajectory confidence level are explained below using the flowchart in Figure 4.

[0047] <Setting the initial confidence level> In step S401, the absolute positioning calculation unit 50 sets the initial confidence level r as the initial value of the absolute positioning trajectory confidence level when calculating the absolute positioning trajectory confidence level. The initial confidence level r may be set in advance, or it may be changed dynamically during the processing steps of the position estimation device 200. For example, if the detection performance of the absolute positioning sensor 20 is high, the initial confidence level r may be set to a high value in advance.

[0048] Furthermore, for example, if multiple absolute positioning sensors 20 are installed, the initial confidence level r may be set high in advance, assuming that there are many sensor inputs for position estimation. Also, for example, if a malfunction of an absolute positioning sensor 20 is suspected during an intermediate processing step of the position estimation device 200, the initial confidence level r may be dynamically set to be lower.

[0049] In step S402, the absolute positioning position calculation unit 50 compares the estimation error of the absolute positioning position used to calculate the absolute positioning trajectory with a preset tolerance error. If the error falls within the tolerance error, it increases the initial confidence level r; otherwise, it decreases the initial confidence level r according to the magnitude of the estimation error. This corresponds, for example, to comparing the estimation error calculated in step S302 based on the satellite positioning accuracy information stored in the absolute positioning position storage area 51 with a preset tolerance error. In other words, in the process of step S402, the confidence level is set according to the accuracy of the absolute positioning position.

[0050] In step S403, the absolute positioning position calculation unit 50 compares the variance of the position error of the absolute positioning position used to calculate the absolute positioning trajectory with respect to the absolute positioning trajectory, with respect to the absolute positioning trajectory, with a preset allowable variance value. If it falls within the allowable variance value, the initial confidence level r is increased; otherwise, the initial confidence level r is decreased according to the magnitude of the variance value. For example, when the moving object 1 is moving in a straight line, ideally the absolute positioning position coincides with the absolute positioning trajectory, so the variance of the position error of the absolute positioning position with respect to the absolute positioning trajectory is 0. However, if the variance value is greater than the allowable variance value, it can be determined that a position error has occurred at one of the absolute positioning positions, and this corresponds to a case where the confidence level of the absolute positioning trajectory is reduced. In other words, in the process of step S403, the confidence level is set according to the variability of the absolute positioning position.

[0051] In step S404, the absolute positioning position calculation unit 50 compares the distance traveled by the moving body 1 during the calculation of the absolute positioning position used to calculate the absolute positioning trajectory with a preset allowable travel distance. If the distance is within the allowable travel distance, the initial confidence level r is increased; otherwise, the initial confidence level r is decreased according to the magnitude of the travel distance. This corresponds, for example, to a case where absolute positioning by the absolute positioning sensor 20 is temporarily interrupted, then resumed, and the absolute positioning positions before and after the interruption are used to calculate the absolute positioning trajectory. In other words, in the process of step S404, the confidence level is set according to the distance continuity of the absolute positioning position.

[0052] The absolute positioning trajectory confidence level is set according to the driving environment around the mobile device 1. Camera 34, map information, roadside devices, etc., are used when setting the absolute positioning trajectory confidence level. Obstacles such as buildings negatively affect satellite positioning. Therefore, it is necessary to change the degree to which the absolute positioning trajectory confidence level is increased or decreased.

[0053] In step S405, the absolute positioning calculation unit 50 compares the driving environment around the mobile body 1 used to calculate the absolute positioning trajectory with preset acceptable environmental conditions. If the conditions fall within the acceptable environmental conditions, it increases the initial confidence level r; otherwise, it decreases the initial confidence level r. In other words, in the process of step S405, the confidence level is set according to the driving environment around the mobile body 1.

[0054] Acceptable environmental conditions include, for example, the presence or absence of obstructions around the mobile body 1. This corresponds to a situation where, for example, when using satellite positioning as an absolute positioning method, in an environment where tall buildings exist around the mobile body 1, even if the signal strength from positioning satellite 2 is strong, the satellite positioning accuracy may decrease due to multipath reflection of the positioning signal off the walls of the tall buildings, thus reducing the reliability of the satellite positioning accuracy. Signal multipath can occur not only with satellite positioning but also with other absolute positioning methods, such as UWB positioning using a UWB receiver 22.

[0055] The method for calculating absolute positioning trajectory confidence described above is based on the fundamental idea of ​​reflecting in the confidence of the absolute positioning trajectory whether or not the accuracy of the multiple absolute positioning positions used in calculating the absolute positioning trajectory is good. In this case, the effects of this disclosure can be achieved by using at least one of the methods for calculating absolute positioning trajectory confidence.

[0056] <Method for calculating relative positioning trajectory confidence> The specific processing steps for calculating the relative positioning trajectory confidence level are explained below using the flowchart in Figure 5.

[0057] <Setting the initial confidence level> In step S501, the relative positioning trajectory calculation unit 60 calculates the relative positioning trajectory confidence ta of the relative positioning trajectory a to be calculated, and sets the initial confidence level ta0 as the initial value of the relative positioning trajectory confidence ta. The initial confidence level ta0 may be set in advance, or it may be changed dynamically during the processing steps of the position estimation device 200. For example, if the detection performance of the relative positioning sensor 30 is high, the initial confidence level ta0 may be set to a high value in advance.

[0058] Furthermore, for example, if there are multiple relative positioning sensors 30, the initial confidence level ta0 may be set high in advance, assuming that there are many sensor inputs for position estimation. Also, for example, if a malfunction of a relative positioning sensor 30 is suspected at an intermediate stage in the processing steps of the position estimation device 200, the initial confidence level ta0 may be dynamically set to be lower.

[0059] In step S502, the relative positioning trajectory calculation unit 60 compares the estimation error of the absolute positioning position used as the calculation criterion for relative positioning trajectory a at the start of the calculation of relative positioning trajectory a with a preset tolerance error. If the error falls within the tolerance error, the relative positioning trajectory confidence level ta is increased; otherwise, the relative positioning trajectory confidence level ta is decreased according to the magnitude of the estimation error. This corresponds, for example, to comparing the estimation error calculated based on the satellite positioning accuracy information stored in the absolute positioning position storage area 51 in step S302 with a preset tolerance error.

[0060] Alternatively, instead of using the estimation error of the absolute positioning position, the absolute positioning trajectory confidence level may be used as an indicator. This can be compared with a preset tolerance level, and if it falls within the tolerance level, the relative positioning trajectory confidence level ta may be increased. If it does not fall within the tolerance level, the relative positioning trajectory confidence level ta may be decreased according to the magnitude of the absolute positioning trajectory confidence level. This corresponds, for example, to the case where if the accuracy of the reference absolute positioning trajectory is good, the accuracy of the relative positioning trajectory is also considered to be good. In other words, in the process of step S502, the relative positioning trajectory confidence level is set according to the estimation error of the absolute positioning position (= absolute positioning trajectory confidence level) at the start of the calculation of the relative positioning trajectory.

[0061] In step S503, the relative positioning trajectory calculation unit 60 compares the driving state of the mobile body 1 at the start of the calculation of the relative positioning trajectory a with a preset allowable driving condition. If the driving state falls within the allowable driving condition, it makes it easier to increase the relative positioning trajectory confidence ta in the processing from step S504 onward. If the driving state does not fall within the allowable driving condition, it makes it harder to decrease the relative positioning trajectory confidence ta in the processing from step S504 onward. The driving state of the mobile body 1 is information about the driving state estimated by the driving state estimation unit 80 in step S307.

[0062] One example of an acceptable driving condition is the turning radius of the mobile body 1. This corresponds to the case where, for example, when calculating a new relative positioning trajectory, the system determines that the mobile body 1 is turning based on the rotation detection result of the mobile body 1 by the gyro sensor 31 and the left and right wheel speed difference detection result by the wheel speed sensor 32, and if the turning radius is greater than or equal to a preset threshold turning radius, the accuracy of the absolute positioning trajectory that serves as the basis for the relative positioning trajectory a decreases, and the amount of increase in the relative positioning trajectory confidence ta is reduced when updating the relative positioning trajectory a.

[0063] For example, when using satellite positioning by a GNSS receiver 21 as an absolute positioning means, the processing cycle of satellite positioning is generally longer than that of a gyro sensor 31 or a wheel speed sensor 32, and the ability to track the trajectory of the moving body 1 often deteriorates during turning.

[0064] In step S504, the relative positioning trajectory calculation unit 60 compares the elapsed time from the start time of calculation of the relative positioning trajectory a to the current calculation time or update time with a preset allowable time. If the time falls within the allowable time, the unit makes it easier to increase the relative positioning trajectory confidence level ta in the processing from step S504 onward. On the other hand, if the time does not fall within the allowable time, the unit makes it harder to decrease the relative positioning trajectory confidence level ta in the processing from step S504 onward. In other words, in the processing of step S504, the longer the elapsed time since the start of calculation of the relative positioning trajectory, the harder it becomes to increase the confidence level.

[0065] Generally, the relative positioning position of the moving object 1 is calculated by integrating the relative movement amount of the moving object 1, which is estimated based on relative positioning sensor information acquired from the relative positioning sensor 30. As the integration time increases, sensor errors accumulate, and the reliability of the relative positioning trajectory decreases. Therefore, by determining an allowable time according to the sensor error characteristics, it becomes possible to appropriately calculate the reliability of the relative positioning trajectory.

[0066] In step S505, the relative positioning trajectory calculation unit 60, if the estimation error of the latest absolute positioning position falls within a preset tolerance, compares the position error of relative positioning trajectory a with respect to the latest absolute positioning position as the estimation error of relative positioning trajectory a with respect to the preset tolerance. If it falls within the tolerance, it increases the relative positioning trajectory confidence level ta; otherwise, it decreases the relative positioning trajectory confidence level ta according to the magnitude of the estimation error. In other words, the process in step S505 compares the position error of the relative positioning trajectory with respect to a highly accurate absolute positioning position.

[0067] This corresponds, for example, to the case in step S302 where, if the estimated error calculated based on the satellite positioning accuracy information stored in the absolute positioning position memory area 51 falls within a preset tolerance, the absolute positioning position is considered the true value and the reliability of the relative positioning trajectory's position accuracy is determined. Furthermore, regarding the absolute positioning position when multiple absolute positioning sensors 20 are provided, one absolute positioning position with the smallest estimated error may be adopted, the average value of each absolute positioning position may be adopted, or a weighted average value may be adopted according to the detection performance of the absolute positioning sensors 20.

[0068] In step S506, the relative positioning trajectory calculation unit 60 compares the position error of relative positioning trajectory a with respect to relative positioning trajectory b held in the relative positioning trajectory memory area 61 with a preset tolerance error as the estimation error of relative positioning trajectory a. If the error falls within the tolerance, the unit increases the relative positioning trajectory confidence level ta; otherwise, the unit decreases the relative positioning trajectory confidence level ta according to the magnitude of the estimation error.

[0069] The driving state of the mobile body 1 is the information regarding the driving state estimated by the driving state estimation unit 80 in step S307. Here, the relative positioning trajectory b is the one among the relative positioning trajectories held in the relative positioning trajectory memory area 61 whose relative positioning trajectory confidence level tb is equal to or greater than a preset allowable confidence level and is the highest.

[0070] This corresponds to the case where a relative positioning trajectory with high positional accuracy already exists, and that relative positioning trajectory is treated as the true value to determine the reliability of the relative positioning trajectory's positional accuracy. Note that if the processing cycles for absolute positioning and relative positioning are different, and the absolute positioning position has not yet been calculated at the time of calculating the relative positioning trajectory reliability, the process in step S506 may be omitted.

[0071] In step S507, the relative positioning trajectory calculation unit 60 compares the driving state estimated by the driving state estimation unit 80 in step S307 with a preset allowable driving condition. If the driving state falls within the allowable driving condition, it is easier to increase ta; if it does not, it is harder to decrease ta. The same allowable driving conditions as in step S503 can be set. In other words, in the processing of step S507, it is harder to increase the reliability depending on the driving state (acceleration, yaw rate) of the moving object 1 estimated from the absolute positioning sensor 20 and the relative positioning sensor 30. This is because a scale factor error occurs in the relative positioning sensor 30.

[0072] The effects of Embodiment 1 can be obtained by using at least one of the relative positioning trajectory confidence calculation methods described above.

[0073] The relative positioning trajectory calculation unit 60 may determine that the relative positioning trajectory retention condition is satisfied if at least one of the following conditions is met for a relative positioning trajectory held in the relative positioning trajectory storage area 61: the relative positioning trajectory reliability is equal to or greater than a preset threshold reliability; the amount of relative positioning trajectories held in the relative positioning trajectory storage area 61 is less than a preset threshold holding amount; or the amount of relative positioning trajectories held in the relative positioning trajectory storage area 61 is equal to or greater than a preset threshold holding amount, and the relative positioning trajectory reliability is higher than a preset set reliability value within the threshold reliability range.

[0074] <Operation of the position estimation device according to Embodiment 1> Figure 6 is a schematic diagram illustrating an example of the operation of the position estimation device 200 according to Embodiment 1. Specifically, Figure 6 shows an example of an absolute positioning position and a relative positioning position, as well as a relative positioning trajectory calculated from the absolute positioning position and the relative positioning position. The relative positioning trajectory is calculated based on the absolute positioning position at each preset time interval. In the example shown in Figure 6, relative positioning trajectory A is calculated based on the absolute positioning position a measured at time 0s, and relative positioning trajectory B is calculated based on the absolute positioning position b measured at time 4s. That is, multiple relative positioning trajectories exist at the same time. Regarding the latest position of the moving object 1 on the relative positioning trajectory, the latest relative positioning position on the relative positioning trajectory selected from among the multiple relative positioning trajectories is output as the estimated position. The relative positioning trajectory that is most recent in time is called the latest relative positioning trajectory.

[0075] For example, if the absolute positioning result has been obtained as shown in Figure 6, at time 2s, the relative positioning position a at time 2s is output as the latest position of mobile object 1. At time 6s, if relative positioning trajectory A is selected, relative positioning position b is output as the latest position of mobile object 1, and if relative positioning trajectory B is selected, relative positioning position c is output as the latest position of mobile object 1.

[0076] Figure 7 is a schematic diagram illustrating another example of the operation of the position estimation device 200 according to Embodiment 1. Specifically, Figure 7 shows an example of the absolute positioning position and relative positioning position, as well as the relative positioning trajectory calculated from the absolute positioning position and relative positioning position, when a moving object 1 enters an area where absolute positioning is impossible, i.e., an area where absolute positioning is not possible. If the absolute positioning position a is highly accurate while the absolute positioning position b is low accuracy, only the relative positioning trajectory C starting from the highly accurate absolute positioning position a is calculated and continuously updated, and the relative positioning trajectory D is not calculated. As a result, it is possible to suppress a decrease in the accuracy of the estimated position.

[0077] In other words, by determining whether a relative positioning trajectory can be calculated based on the condition that the absolute positioning position satisfies the predetermined relative positioning trajectory calculation conditions, low-accuracy relative positioning trajectories are eliminated in advance. This has the effect of suppressing a decrease in the accuracy of the estimated position, even when absolute positioning is impossible.

[0078] <Effects of Embodiment 1> As described above, the position estimation device and position estimation method according to Embodiment 1 have the effect of being able to continue highly accurate position estimation using a more reliable relative positioning trajectory, even when absolute positioning becomes impossible while a moving object is in motion, by using the absolute positioning position calculated based on absolute positioning sensor information obtained from an absolute positioning sensor as a reference and maintaining and updating the relative positioning trajectory and relative positioning trajectory reliability at any time based on relative positioning sensor information obtained from a relative positioning sensor.

[0079] In the configuration of the position estimation device 200 according to Embodiment 1 described above, the position estimation device 200 is described as a functional block. However, an example of the configuration of the hardware housing the position estimation device 200 is shown in Figure 8. The hardware 800 consists of a processor 801 and a storage device 802. Although not shown, the storage device 802 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory.

[0080] Alternatively, a hard disk may be provided as an auxiliary storage device instead of flash memory. The processor 801 executes a program input from the storage device 802. In this case, the program is input to the processor 801 from the auxiliary storage device via a volatile storage device. The processor 801 may also output data such as calculation results to the volatile storage device of the storage device 802, or it may save the data to the auxiliary storage device via the volatile storage device.

[0081] <Summary of the various aspects of this application> The various aspects of this application are summarized below as an appendix.

[0082] (Note 1) A position estimation device that estimates its own position based on absolute positioning sensor information acquired by an absolute positioning sensor mounted on a moving object and receiving multiple signals emitted from known positions, and relative positioning sensor information acquired by a relative positioning sensor mounted on the moving object and detecting changes in the relative position of the moving object, An absolute positioning position calculation unit calculates the absolute position of the moving object based on the absolute positioning sensor information, A relative positioning trajectory calculation unit calculates the relative positioning trajectory of the moving object based on the relative positioning sensor information, with respect to the absolute positioning position, and has a relative positioning trajectory storage area that stores the calculated relative positioning trajectory. A relative positioning trajectory comparison unit outputs the latest position of the moving object on the selected relative positioning trajectory as the estimated position of the moving object when the relative positioning trajectory satisfies predetermined relative positioning trajectory selection conditions. A position estimation device equipped with the following features.

[0083] (Note 2) The relative positioning trajectory calculation unit repeats the process of storing the latest relative positioning trajectory in the relative positioning trajectory storage area each time the latest relative positioning trajectory based on the relative positioning sensor information satisfies the relative positioning trajectory storage conditions, thereby updating the past relative positioning trajectories stored in the relative positioning trajectory storage area with the latest relative positioning trajectory. The position estimation device according to Appendix 1, characterized in that if the latest relative positioning trajectory does not satisfy the predetermined relative positioning trajectory retention conditions, the latest relative positioning trajectory is deleted without being retained in the relative positioning trajectory storage area.

[0084] (Note 3) The position estimation device according to Appendix 2, wherein the absolute positioning position calculation unit has an absolute positioning position storage area capable of storing the calculated absolute positioning position, calculates the absolute positioning trajectory of the moving object based on a plurality of absolute positioning positions stored in the absolute positioning position storage area, and updates the latest position of the moving object on the absolute positioning trajectory as the absolute positioning position based on the absolute positioning sensor information.

[0085] (Note 4) The absolute positioning location calculation unit calculates the absolute positioning trajectory reliability, which represents the reliability of the absolute positioning trajectory. The position estimation device according to Appendix 3, characterized in that the relative positioning trajectory calculation unit determines that the relative positioning trajectory calculation conditions are satisfied when the absolute positioning trajectory reliability is equal to or greater than a preset threshold reliability.

[0086] (Note 5) The position estimation device according to Appendix 4, characterized in that the absolute positioning trajectory reliability is calculated using at least one of the following as an indicator: the estimation error that occurs at each of the plurality of absolute positioning positions used to calculate the absolute positioning trajectory; the position error of each of the plurality of absolute positioning positions used to calculate the absolute positioning trajectory with respect to the relative positioning trajectory; and the distance the moving body has moved while calculating the plurality of absolute positioning positions used to calculate the absolute positioning trajectory.

[0087] (Note 6) The system further includes a surrounding environment estimation unit that estimates the driving environment around the moving object based on the absolute positioning sensor information and the relative positioning sensor information. The position estimation device according to Appendix 5, further characterized in that it includes the driving environment around the moving object as an index for calculating the absolute positioning trajectory reliability.

[0088] (Note 7) The relative positioning trajectory calculation unit calculates the relative positioning trajectory reliability, which is the reliability of the relative positioning trajectory. The position estimation device according to any one of the appendices 1 to 6, characterized in that the relative positioning trajectory comparison unit determines that the relative positioning trajectory selection condition is satisfied when the relative positioning trajectory reliability is equal to or greater than a preset threshold reliability.

[0089] (Note 8) The position estimation device according to Appendix 7, characterized in that the relative positioning trajectory reliability is calculated using at least one of the following as an indicator: the estimation error of the absolute positioning position; the position error of the relative positioning trajectory with respect to the absolute positioning position; the position error of the relative positioning trajectory with respect to the relative positioning trajectory held in the relative positioning trajectory storage area; the estimation error of the absolute positioning position at the start of the calculation of the relative positioning trajectory; the driving state of the moving body estimated from the absolute positioning sensor information and the relative positioning sensor information; the driving state of the moving body at the start of the calculation of the relative positioning trajectory; the driving environment around the moving body estimated from the absolute positioning sensor and the relative positioning sensor; the driving environment of the moving body at the start of the calculation of the relative positioning trajectory; and the elapsed time since the start of the calculation of the relative positioning trajectory.

[0090] (Note 9) The system further includes a driving state estimation unit that estimates the driving state of the moving object based on the absolute positioning sensor information and the relative positioning sensor information. The position estimation device according to Appendix 8, further comprising, as an index for calculating the relative positioning trajectory reliability, the driving state of the moving body estimated by the driving state estimation unit and the driving state of the moving body at the start of the calculation of the relative positioning trajectory.

[0091] (Note 10) The relative positioning trajectory calculation unit satisfies the relative positioning trajectory calculation condition when the reliability of all relative positioning trajectories held in the relative positioning trajectory storage area is less than a preset threshold reliability, as described in any one of Appendix 7 to 9.

[0092] (Note 11) The relative positioning trajectory calculation unit determines that the relative positioning trajectory retention condition is satisfied if at least one of the following conditions is met for the relative positioning trajectory held in the relative positioning trajectory storage area: the relative positioning trajectory reliability is equal to or greater than a preset threshold reliability; the amount of the relative positioning trajectory held in the relative positioning trajectory storage area is less than a preset threshold amount; or the amount of the relative positioning trajectory held in the relative positioning trajectory storage area is equal to or greater than the threshold amount, and the relative positioning trajectory reliability is higher than a preset set reliability value within the range of the threshold reliability. This is the position estimation device according to any one of the appendices 7 to 10.

[0093] (Note 12) The position estimation device according to Appendix 1, characterized in that the relative positioning trajectory calculation unit calculates the relative positioning trajectory of the moving object with respect to the absolute positioning position based on the relative positioning sensor information when the absolute positioning position satisfies predetermined relative positioning trajectory calculation conditions.

[0094] (Note 13) A position estimation method comprising the following steps performed by a position estimation device for estimating the position of a moving object, A step of calculating the absolute position of the moving object based on absolute positioning sensor information acquired by the absolute positioning sensor, The steps include: calculating the relative positioning trajectory of the moving object based on the absolute positioning position, using relative positioning sensor information acquired by the relative positioning sensor that detects changes in the relative position of the moving object; and storing the calculated relative positioning trajectory in a relative positioning trajectory storage area. If the relative positioning trajectory satisfies the predetermined relative positioning trajectory selection conditions, the step of estimating the latest position of the moving object on the selected relative positioning trajectory as the position of the moving object, Each time the latest relative positioning trajectory satisfies the relative positioning trajectory retention conditions based on the relative positioning sensor information, the process of retaining the latest relative positioning trajectory in the relative positioning trajectory storage area is repeated, thereby updating the past relative positioning trajectories retained in the relative positioning trajectory storage area with the latest relative positioning trajectory. A position estimation method comprising the following features.

[0095] While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but can be applied individually or in various combinations to the embodiments.

[0096] Accordingly, countless variations not illustrated are conceivable within the scope of the technology disclosed herein. These include, for example, modifications, additions, or omissions of at least one component, as well as the extraction of at least one component and its combination with components of other embodiments. [Explanation of Symbols]

[0097] 1 Mobile unit, 2 Positioning satellite, 20 Absolute positioning sensor, 21 GNSS receiver, 22 UWB receiver, 23 Infrared receiver, 24 Wireless LAN receiver, 30 Relative positioning sensor, 31 Gyroscope sensor, 32 Wheel speed sensor, 33 Accelerometer, 34 Camera, 50 Absolute positioning location calculation unit, 51 Absolute positioning location memory area, 60 Relative positioning trajectory calculation unit, 61 Relative positioning trajectory memory area, 70 Surrounding environment estimation unit, 80 Driving state estimation unit, 90 Relative positioning trajectory comparison unit, 200 Position estimation device, 800 Hardware, 801 Processor, 802 Memory device

Claims

1. A position estimation device that estimates its own position based on absolute positioning sensor information acquired by an absolute positioning sensor mounted on a moving object and receiving multiple signals emitted from known positions, and relative positioning sensor information acquired by a relative positioning sensor mounted on the moving object and detecting changes in the relative position of the moving object, An absolute positioning position calculation unit calculates the absolute position of the moving object based on the absolute positioning sensor information, A relative positioning trajectory calculation unit calculates the relative positioning trajectory of the moving object based on the relative positioning sensor information, with respect to the absolute positioning position, and has a relative positioning trajectory storage area that stores the calculated relative positioning trajectory. The system includes a relative positioning trajectory comparison unit that, when the relative positioning trajectory satisfies predetermined relative positioning trajectory selection conditions, outputs the latest position of the moving object on the selected relative positioning trajectory as the estimated position of the moving object. The relative positioning trajectory calculation unit repeats the process of storing the latest relative positioning trajectory in the relative positioning trajectory storage area each time the latest relative positioning trajectory based on the relative positioning sensor information satisfies the relative positioning trajectory retention conditions, updating the past relative positioning trajectories stored in the relative positioning trajectory storage area with the latest relative positioning trajectory. If the latest relative positioning trajectory does not satisfy the predetermined relative positioning trajectory retention conditions, the latest relative positioning trajectory is deleted without being stored in the relative positioning trajectory storage area. The absolute positioning position calculation unit has an absolute positioning position storage area capable of storing the calculated absolute positioning position, calculates the absolute positioning trajectory of the moving object based on a plurality of absolute positioning positions stored in the absolute positioning position storage area, and updates the latest position of the moving object on the absolute positioning trajectory as the absolute positioning position based on the absolute positioning sensor information. The absolute positioning position calculation unit calculates an absolute positioning trajectory confidence level representing the reliability of the absolute positioning trajectory, and the relative positioning trajectory calculation unit determines that the relative positioning trajectory calculation conditions are satisfied if the absolute positioning trajectory confidence level is equal to or greater than a preset threshold confidence level. The position estimation device is characterized in that the absolute positioning trajectory reliability is calculated using at least one of the following as an indicator: the estimation error that occurs at each of the plurality of absolute positioning positions used to calculate the absolute positioning trajectory; the position error of each of the plurality of absolute positioning positions used to calculate the absolute positioning trajectory with respect to the relative positioning trajectory; and the distance the moving body traveled while calculating the plurality of absolute positioning positions used to calculate the absolute positioning trajectory.

2. The system further includes a surrounding environment estimation unit that estimates the driving environment around the moving object based on the absolute positioning sensor information and the relative positioning sensor information. The position estimation device according to claim 1, further comprising the driving environment around the moving object as an index for calculating the absolute positioning trajectory reliability.

3. The relative positioning trajectory calculation unit calculates the relative positioning trajectory reliability, which is the reliability of the relative positioning trajectory. The position estimation device according to claim 1 or 2, characterized in that the relative positioning trajectory comparison unit determines that the relative positioning trajectory selection condition is satisfied when the relative positioning trajectory reliability is equal to or greater than a preset threshold reliability.

4. The position estimation device according to claim 3, characterized in that the relative positioning trajectory reliability is calculated using at least one of the following as an indicator: the estimation error of the absolute positioning position; the position error of the relative positioning trajectory with respect to the absolute positioning position; the position error of the relative positioning trajectory with respect to the relative positioning trajectory held in the relative positioning trajectory storage area; the estimation error of the absolute positioning position at the start of the calculation of the relative positioning trajectory; the driving state of the moving body estimated from the absolute positioning sensor information and the relative positioning sensor information; the driving state of the moving body at the start of the calculation of the relative positioning trajectory; the driving environment around the moving body estimated from the absolute positioning sensor and the relative positioning sensor; the driving environment of the moving body at the start of the calculation of the relative positioning trajectory; and the elapsed time since the start of the calculation of the relative positioning trajectory.

5. The system further includes a driving state estimation unit that estimates the driving state of the moving object based on the absolute positioning sensor information and the relative positioning sensor information. The position estimation device according to claim 4, further comprising, as an index for calculating the relative positioning trajectory reliability, the driving state of the moving body estimated by the driving state estimation unit and the driving state of the moving body at the start of the calculation of the relative positioning trajectory.

6. The position estimation device according to claim 5, characterized in that the relative positioning trajectory calculation unit satisfies the relative positioning trajectory calculation condition when the reliability of all relative positioning trajectories held in the relative positioning trajectory storage area is less than a preset threshold reliability.

7. The relative positioning trajectory calculation unit determines that the relative positioning trajectory retention condition is satisfied if at least one of the following conditions is met for the relative positioning trajectory held in the relative positioning trajectory storage area: the relative positioning trajectory reliability is equal to or greater than a preset threshold reliability; the amount of the relative positioning trajectory held in the relative positioning trajectory storage area is less than a preset threshold amount; or the amount of the relative positioning trajectory held in the relative positioning trajectory storage area is equal to or greater than the threshold amount, and the relative positioning trajectory reliability is higher than a preset set reliability value within the range of the threshold reliability. This is the position estimation device according to claim 3.

8. The position estimation device according to claim 1, characterized in that the relative positioning trajectory calculation unit calculates the relative positioning trajectory of the moving object with respect to the absolute positioning position based on the relative positioning sensor information when the absolute positioning position satisfies predetermined relative positioning trajectory calculation conditions.

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