Parking assistance method and parking assistance device

Abstract

In a parking assistance method according to the present invention, target parking (31) and k-point turn site information (32) are acquired from a storage device (19b) that has stored therein, at a time of parking in advance, information of a parking position (31) at a time of parking, and information of a k-point turn site (32) that is a site at which a vehicle performed a k-point turn at the time of parking the vehicle at the parking position (31). An own position (33) that is the current position of an own vehicle (1) is detected, a threshold value is set in accordance with detection precision of the own position (33), and in a case in which a distance between the k-point turn site (32) and the own position (33) is no greater than the threshold value, guidance is given to a user of the own vehicle (1) as a parking position (31) target parking position candidate.

Description

Parking assistance method and parking assistance device

[0001] The present invention relates to a parking assistance method and a parking assistance device.

[0002] The following Patent Document 1 describes a parking assistance device that stores parking target positions from parking operations performed in the past and provides guidance to a target position where the vehicle can automatically drive to the target parking position.

[0003] Japanese Patent Application Laid-Open No. 2022-133230

[0004] When a pre-stored parking target position guide is presented to a user, if the parking target position is located in a place where the detection accuracy of the vehicle's own position is low, it may be impossible to determine that the vehicle has approached the parking target position.The present invention aims to make it easier to determine that the vehicle has approached the parking target position when a pre-stored parking target position guide is presented to a user, even in a place where the detection accuracy of the vehicle's own position is low.

[0005] In one aspect of the parking assistance method of the present invention, information on the parking position when parking and information on the turning point, which is the point where the vehicle turned when parked in the parking position, are obtained from a storage device that previously stored the information when parking, and information on the parking position and the turning point, which is the point where the vehicle turned when parked in the parking position, and the vehicle's current position, which is the vehicle's own position, is detected, a threshold is set according to the detection accuracy of the self-position, and if the distance between the turning point and the vehicle's own position is equal to or less than the threshold, the parking position is guided to the user of the vehicle as a target parking position candidate.

[0006] According to the present invention, when presenting a pre-stored parking target position guidance to a user, it becomes easier to determine that the vehicle has approached the parking target position even in a location where the detection accuracy of the vehicle's own position is low. The objects and advantages of the present invention are realized and achieved by using the elements and combinations thereof set forth in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory only and should not be construed as limiting the invention as defined by the claims.

[0007] 1 is a diagram showing an example of a schematic configuration of a parking assistance device according to an embodiment; (a) is a schematic diagram of a scene in which a target parking position is registered, and (b) is a schematic diagram of a scene in which parking assistance to the target parking position is performed; (a) is a schematic diagram of an example of a first guidance screen; (b) is a flowchart of a parking assistance method according to the first embodiment; (a) and (b) are schematic diagrams for explaining an example of a method of detecting a parking position using learned targets; (b) is a block diagram of an example of a functional configuration of the controller shown in FIG. 1; (b) is a schematic diagram of an example of a second guidance screen; (b) is a flowchart of a parking assistance method according to the second embodiment; and (b) is a flowchart of an example of a method of setting a threshold value.

[0008] (First Embodiment) (Configuration) FIG. 1 is a diagram showing an example of a schematic configuration of a parking assistance device according to an embodiment. A host vehicle 1 includes a parking assistance device 10 that assists the host vehicle 1 in parking at a target parking position. The parking assistance device 10 assists the host vehicle 1 in traveling along a target parking path from the current position of the host vehicle 1 to the target parking position. For example, an automatic driving may be performed in which the host vehicle 1 is controlled to travel to the target parking position along the target parking path of the host vehicle 1. The automatic driving that controls the host vehicle 1 to travel to the target parking position along the target parking path of the host vehicle 1 means control of all or part of the steering angle, driving force, and braking force of the host vehicle 1 to automatically perform all or part of the traveling of the host vehicle 1 along the target parking path. Furthermore, parking of the host vehicle 1 may be assisted by displaying the target parking path and the current position of the host vehicle 1 on a display device that is visible to a user (e.g., a passenger such as a driver) in the host vehicle 1.

[0009] The positioning device 11 measures the current position of the vehicle 1. The positioning device 11 includes, for example, a Global Navigation System (GNSS) receiver. For example, the GNSS receiver may be a Global Positioning System (GPS) receiver. Map data is stored in a map database (map DB) 12. The map data stored in the map database 12 may be, for example, map data for navigation or high-precision map data suitable for maps for autonomous driving. The human-machine interface (HMI) 13 is an interface device that exchanges information between the parking assistance device 10 and a user. For example, the HMI 13 may include a display device visible to the user as an interface that presents visual information to the user. The HMI 13 may also include a speaker or a buzzer as an interface that presents auditory information to the user. The HMI 13 may also include an interface (such as a touch panel, button, switch, lever, dial, or keyboard) that accepts operational input from the user.

[0010] The shift switch (shift SW) 14 is a switch used by the driver or the parking assistance device 10 to switch the shift position of the host vehicle 1. The external sensor 15 detects objects within a predetermined distance range from the host vehicle 1. The external sensor 15 detects the surrounding environment of the host vehicle 1, such as the relative position of the host vehicle 1 and an object present around the host vehicle 1, the distance between the host vehicle 1 and the object, and the direction in which the object is present. The external sensor 15 may include, for example, a camera that captures the surrounding environment of the host vehicle 1. The external sensor 15 may also include a distance measuring device such as a laser range finder, radar, LiDAR (Light Detection and Ranging), or sonar. The vehicle sensor 16 detects various information (vehicle information) about the host vehicle 1. For example, the vehicle sensor 16 may include a vehicle speed sensor that detects the traveling speed of the host vehicle 1, a three-axis acceleration sensor that detects the acceleration (including deceleration) of the host vehicle 1 in three axial directions, and sensors that detect the steering angle of the steering wheel and the steering angle of the steered wheels. The parking switch (parking SW) 17 is a switch for starting the parking assist control by the parking assist device 10 .

[0011] The controller 19 is an electronic control unit that performs parking assistance control of the host vehicle 1. The controller 19 includes a processor 19a and peripheral components such as a storage device 19b. The processor 19a may be, for example, a CPU or an MPU. The storage device 19b may include a semiconductor storage device, a magnetic storage device, an optical storage device, or the like. The functions of the controller 19 described below are realized, for example, by the processor 19a executing a computer program stored in the storage device 19b. The parking brake 20 generates frictional braking force on the wheels of the host vehicle 1 in accordance with a user's operation or a control signal from the controller 19. The steering actuator 21a controls the steering direction and steering amount of the steering mechanism of the host vehicle 1 in accordance with the control signal from the controller 19. The accelerator actuator 21b controls the accelerator opening of a drive device such as an engine or a drive motor in accordance with the control signal from the controller 19. The brake actuator 21c activates a braking device in accordance with the control signal from the controller 19.

[0012] Next, parking assist control by the controller 19 will be described. The controller 19 executes parking assist control to assist in parking at a pre-registered target parking position. The target parking position is stored (registered) in a specific storage device in advance before executing parking assist for the host vehicle 1. FIG. 2( a) is a schematic diagram of a scene in which a target parking position is registered. When registering a target parking position, a vehicle (the host vehicle 1 in the example of FIG. 2( a)) is manually driven to park at the target parking position in advance. In FIG. 2( a), a dashed line 30 indicates a parking trajectory when the host vehicle 1 is actually parked at a parking position 31 by manual driving, and reference numeral 32 indicates a turning position on the parking trajectory 30, where the host vehicle 1 turns. Note that a "turning position" refers to an operation of changing the vehicle's shift position from a forward driving position to a reverse driving position. For example, the controller 19 may detect the occurrence of a turning position based on a change in the state of the shift switch 14. The controller 19 may acquire the position of the host vehicle 1 measured by the positioning device 11 at the time of the turning position as a turning position 32. Furthermore, the controller 19 may acquire the position of the vehicle 1 measured by the positioning device 11 at the time when the parking maneuver of the vehicle 1 by manual driving is completed as the parking position 31. For example, the controller 19 may determine that the parking maneuver is completed when the shift position of the vehicle is in the parking range (P). The controller 19 registers the parking position 31 and the turning position 32 by associating them with each other in a coordinate system (hereinafter referred to as a "map coordinate system") that has a fixed point as its reference point and storing them in a specific storage device.

[0013] The specific storage device that stores the parking position 31 and the turning position 32 may be, for example, the storage device 19b, or a storage device external to the host vehicle 1 (e.g., a cloud computer). For example, the parking position 31 and the turning position 32 acquired when another vehicle other than the host vehicle 1 is manually parked at the parking position 31 may be stored in a storage device external to the host vehicle 1 and the other vehicle. The host vehicle 1 may receive the parking position 31 and the turning position 32 stored in the external storage device via a communication device and use them for parking assistance for the host vehicle 1. The following description will exemplify a case in which the parking position 31 and the turning position 32 are registered in the storage device 19b. See FIG. 2(b). When performing parking assistance for the parking position 31 as the target parking position, the controller 19 acquires the pre-registered parking position 31 and the turning position 32 from the storage device 19b. The positioning device 11 also detects the host vehicle 1's current position 33. The controller 19 sets the threshold Dth according to the detection accuracy of the host vehicle 11. For example, the controller 19 may set a larger threshold Dth when the detection accuracy is low than when the detection accuracy is high. For example, the lower the detection accuracy, the larger the threshold Dth may be set.

[0014] When the distance D between the vehicle's own position 33 and the steering position 32 is equal to or less than a threshold value Dth, the controller 19 presents the user with guidance regarding the parking position 31 as a target parking position candidate. For example, the controller 19 may display a first guidance screen presenting the parking position 31 to the user on the display device of the HMI 13 as guidance regarding the parking position 31. If there are multiple parking positions 31 that satisfy the above conditions, the controller 19 may present all parking positions that satisfy the conditions, may present the parking positions in order of proximity to the vehicle's own position 33, or may present only the parking positions closest to the vehicle's own position 33. FIG. 3 is a schematic diagram of an example of the first guidance screen. The first guidance screen 40a includes a captured image 41 generated by capturing an image of the surroundings of the vehicle 1, an overhead image 42 generated by converting the captured image of the surroundings of the vehicle 1, a message display area 43 in which visual messages and other notifications are displayed, a parking start button 44, and an end button 45. When the user operates the parking start button 44 or the end button 45 displayed on the display device, a touch panel provided on the display device detects these operations. An icon 42a representing the current position of the vehicle 1 and a target parking position mark 42b representing the parking position 31 are superimposed on the overhead image 42. A message display area 43 of the first guidance screen 40a may display a notification such as a visual message informing the user that a parking position has been detected. When the end button 45 is operated, the controller 19 stops the parking assistance control. The same applies when the end button 45 on the second guidance screen 40b shown in FIG. 7 (described later) is operated. When the parking start button 44 is operated, the controller 19 sets the parking position 31 as the target parking position and begins assistance with parking the vehicle 1 at the target parking position. On the other hand, if the distance D between the vehicle's current position 33 and the turning position 32 is longer than the threshold Dth, the controller 19 does not present the user with guidance regarding the parking position 31.

[0015] The controller 19 may determine whether to present guidance regarding the parking position 31 depending on whether the distance between the own position 33 and the parking position 31 is equal to or less than a threshold Dth. The controller 19 may also determine whether to present guidance regarding the parking position 31 depending on whether the distance between the own position 33 and any position on a line segment connecting the parking position 31 and the turning position 32 is equal to or less than a threshold Dth. For example, the controller 19 may determine whether to present guidance regarding the parking position 31 depending on whether the distance between the own position 33 and a midpoint between the parking position 31 and the turning position 32 is equal to or less than the threshold Dth.

[0016] (Operation) FIG. 4 is a flowchart of the parking assistance method of the first embodiment. In step S1, the controller 19 acquires the pre-registered parking position 31 and the turning position 32 from the storage device 19b. In step S2, the controller 19 detects the vehicle's own position 33. In step S3, the controller 19 sets a threshold Dth according to the detection accuracy of the vehicle's own position 33. In step S4, the controller 19 determines whether the distance D between the vehicle's own position 33 and the turning position 32 is equal to or less than the threshold Dth. If the distance D is not equal to or less than the threshold Dth (step S4: N), the process ends. If the distance D is equal to or less than the threshold Dth (step S4: Y), the process proceeds to step S5. In step S5, the controller 19 presents the parking position 31 to the user as a target parking position candidate based on the turning position 32 and the vehicle's own position 33. The process then ends.

[0017] Second Embodiment The controller 19 of the second embodiment learns and registers targets present around the parking position 31 in advance as "learned targets." When assisting parking of the host vehicle 1, targets detected around the host vehicle 1 are compared with the learned targets to detect the relative position of the parking position 31 with respect to the host vehicle 1. In the following description, targets detected around the host vehicle 1 and compared with the learned targets during parking assistance may be referred to as "surrounding targets." FIGS. 5( a) and 5(b) are schematic diagrams illustrating an example of a method for detecting the parking position 31 using learned targets. When registering the parking position 31, targets present around the parking position 31 are extracted and stored (registered) in advance in the storage device 19b as learned targets. For example, as shown in FIG. 5( a), the host vehicle 1 is manually driven along the parking path 30 to park it at the parking position 31, and targets present around the host vehicle 1 are detected by the external sensor 15 and stored as learned targets. The circle plots schematically represent learned targets. For example, the controller 19 may store the relative position of the learned target with respect to the parking position 31. The controller 19 can acquire the position of the learned target detected when the host vehicle 1 is parked at the parking position 31 as the relative position of the learned target with respect to the parking position 31. The controller 19 may store the coordinates of the learned target and the parking position 31 in the map coordinate system. The controller 19 stores learned target data related to the learned target in the storage device 19b. For example, the learned target data may include data representing the feature amounts of the learned target (hereinafter referred to as "feature amount data"), data on the relative positional relationship between the parking position 31 and the learned target (hereinafter referred to as "relative position data"), and position data of the parking position 31 in the map coordinate system. As the relative position data, for example, the relative position of the learned target with respect to the parking position 31 may be stored. For example, the controller 19 can acquire the position of a learned target detected when the vehicle 1 is parked in the parking position 31 as the relative position of the learned target with respect to the parking position 31. The coordinates of the learned target and the parking position 31 in the map coordinate system may be stored.

[0018] 5B. When assisting the parking of the host vehicle 1 into the parking position 31, the controller 19 uses the external sensor 15 to extract targets around the host vehicle 1 as surrounding targets. Triangular plots represent surrounding targets. The controller 19 detects parking positions 31 present around the host vehicle 1 by matching the learned targets with the surrounding targets and associating identical feature points. The controller 19 calculates the relative position of the host vehicle 1 with respect to the parking position 31 based on the relative positional relationship between the host vehicle 1 and the surrounding targets detected during parking assistance and the relative positional relationship between the learned targets associated with the surrounding targets and the parking position 31. For example, the controller 19 calculates the position of the parking position 31 in a coordinate system based on the current position of the host vehicle 1 (hereinafter referred to as the "vehicle coordinate system"). Note that, when the coordinates of the learned targets and the parking position 31 on the map coordinate system are stored in the storage device 19b, the coordinates of the parking position 31 on the map coordinate system may be converted into coordinates on the vehicle coordinate system based on the positions of the surrounding targets detected when parking assistance is performed and the positions of the learned targets in the map coordinate system. The host vehicle 1's own position 33 on the map coordinate system may be obtained based on the positions of the surrounding targets detected when parking assistance is performed and the positions of the learned targets in the map coordinate system, and the relative position of the host vehicle 1 with respect to the parking position 31 may be calculated from the difference between the coordinates of the host vehicle 1 and the coordinates of the parking position 31 in the map coordinate system. Thereafter, the controller 19 calculates a target parking path 35 from the host vehicle 1's own position 33 to the parking position 31. The controller 19 performs parking assistance control of the host vehicle 1 based on the calculated target parking path 35.

[0019] FIG. 6 is a block diagram of an example of the functional configuration of the parking assistance function performed by the controller of FIG. 1 . The HMI control unit 50 detects a user's operation to register the parking position 31. When registering the parking position 31, the HMI control unit 50 outputs a map generation command to the map generation unit 55 to store learned target data in the storage device 19b. The image conversion unit 52 converts images captured by the camera into overhead images viewed from a virtual viewpoint directly above the host vehicle 1. The image conversion unit 52 converts captured images into overhead images at predetermined intervals and accumulates the converted overhead images along the travel path of the host vehicle 1 to generate a surrounding image, which is an image of the area surrounding the host vehicle 1. The host position calculation unit 53 calculates the host position, which is the current position of the host vehicle 1 on a map coordinate system, using autonomous navigation (e.g., odometry such as dead reckoning) based on the positioning result of the host vehicle 1 measured by the positioning device 11 using the satellite positioning system and vehicle information output from the vehicle sensor 16.

[0020] For example, the self-position calculation unit 53 acquires from the positioning device 11 an observed value Xo=(X coordinate, Y coordinate, azimuth angle (yaw angle)) of the current position of the vehicle 1 on a map coordinate system measured by the satellite positioning system. The self-position calculation unit 53 also acquires positioning status information indicating the positioning status of the satellite positioning system. For example, the positioning status information may include a mode FIX_TYPE of the position information of the satellite positioning system, the number NUM of captured positioning satellites, a dilution of precision (DOP) that is an index value according to the positioning status of the captured positioning satellites, and a satellite signal reception availability signal. For example, the mode FIX_TYPE is set to “NO FIX” indicating that position information cannot be obtained, “2D FIX” indicating that two-dimensional information has been obtained, or “3D FIX” indicating that three-dimensional information has been obtained. The self-position calculation unit 53 sets a satellite positioning system usage flag Fs that determines whether or not to use position information from the satellite positioning system, based on the shift position detected by the shift switch 14 and the positioning status information. When the flag Fs = True, the self-position calculation unit 53 calculates the self-position of the vehicle 1 using the satellite positioning system and autonomous navigation, and when the flag Fs = False, the self-position calculation unit 53 calculates the self-position of the vehicle 1 using only autonomous navigation. For example, the self-position calculation unit 53 may set the satellite positioning system usage flag Fs to True when it is possible to receive satellite signals, the shift position is a forward driving position (for example, drive range (D) or brake range (B)), the acquisition number NUM is equal to or greater than the acquisition number threshold thNUM, and the accuracy degradation rate DOP is smaller than the DOP threshold thDOP, and may set the flag to False in other cases.

[0021] Furthermore, the self-position calculation unit 53 acquires from the vehicle sensor 16 a detected value of the vehicle speed V, which is the speed of the center position of the rear axle of the vehicle 1, and a detected value of the steering angle θ of the steering wheel. The self-position calculation unit 53 calculates the yaw rate γ of the vehicle 1 based on the detected values ​​of the vehicle speed V and the steering angle θ. The self-position calculation unit 53 calculates the self-position of the vehicle 1 based on these detected values ​​and calculated values ​​acquired from the vehicle sensor 16, the observed value Xo and positioning status information acquired from the positioning device 11, and the satellite positioning system usage flag Fs. For example, the self-position calculation unit 53 may calculate the self-position of the vehicle 1 using an extended Kalman filter based on a geometric model based on the rear wheel axle, which will be described below. Now, the state value X_ of the vehicle 1 = (X coordinate, Y coordinate, azimuth angle) Ｔ is defined as follows:

[0022]

[0023] In the above equations, the variables x, y, and θ are the state values ​​of the previous X coordinate, Y coordinate, and azimuth angle, respectively; ΔT is the calculation period of the Kalman filter; and the variable u is a vector (V, γ) whose elements are the vehicle speed V and yaw rate γ. The error matrices R and Q are set as shown in the following equations. The elements r1, r2, and r3 are the variances of the X error, Y error, and azimuth angle error of the satellite positioning system, respectively, and the elements q1 and q2 are the variances of the vehicle speed and yaw rate errors. These elements r1, r2, r3, q1, and q2 are adjustment parameters that are determined as appropriate depending on the design. Furthermore, the self-position calculation unit 53 sets the matrix C as shown in the following equation according to the satellite positioning system usage flag Fs.

[0024]

[0025] The self-position calculation unit 53 calculates the variance S of the estimated value of the Kalman filter, the variance S of the predicted value, the Kalman gain K, and the self-position Xh of the vehicle 1 using the following equations. The self-position calculation unit 53 also calculates the norm Ns of the variance S and the norm Nk of the Kalman gain K.

[0026]

[0027] When the satellite positioning system usage flag Fs is True (when the satellite positioning system is used), the self-position Xh is X_+K(Xo-CX_). That is, the state value X_ estimated by autonomous navigation is corrected with the observation value Xo of the satellite positioning system to calculate the self-position Xh. On the other hand, when the satellite positioning system usage flag Fs is False (when the satellite positioning system is not used), the matrix C becomes a zero matrix, and the self-position Xh becomes equal to X_. That is, the self-position Xh is detected only by autonomous navigation without using the satellite positioning system. For example, when the shift position is in a position other than the forward driving position, the self-position Xh is detected only by autonomous navigation without using the satellite positioning system. This is because when not driving forward, the vehicle is moving at a low speed or is stopped, so the error in the self-position determined by the satellite positioning system becomes larger than the distance traveled, and the self-position cannot be accurately identified. Therefore, the satellite positioning system may be used only when traveling at a predetermined speed or higher, and when traveling at a speed lower than the predetermined speed, the vehicle's own position Xh may be detected only by autonomous navigation without using the satellite positioning system. Furthermore, even when the vehicle's own position cannot be detected by the satellite positioning system (for example, when satellite signals cannot be received, when the acquisition number NUM is less than a threshold, or when the degradation rate DOP is greater than or equal to a threshold), the vehicle's own position Xh = X_ is calculated using only the state value X_ estimated by autonomous navigation. In this case, the vehicle's own position is calculated based on the positioning results from a past point in time when the vehicle's own position could be detected by the satellite positioning system and the subsequent autonomous navigation.

[0028] The target detection unit 54 detects targets from the surrounding image output from the image conversion unit 52. The target detection unit 54 may detect the positions of feature points of the targets and their image feature quantities. The target detection unit 54 outputs the detected positions of feature points and the image feature quantities as target data to the map generation unit 55 and the target parking position detection unit 57. In addition, in synchronization with the target detection, the map generation unit 55 outputs the current position of the vehicle 1 acquired from the self-position calculation unit 53 to the map generation unit 55 and the target parking position detection unit 57. When the map generation unit 55 receives a map generation command from the HMI control unit 50 (i.e., when a parking position 31 registration operation is performed), the map generation unit 55 generates learned target data and stores it in the storage device 19b as map data 56. For example, the map generation unit 55 receives the target data and the current position of the vehicle 1 on a map coordinate system synchronized with the target data from the target detection unit 54. The map generation unit 55 acquires position information of the parking position 31 in the map coordinate system. For example, when the vehicle 1 is located in the parking position 31, the current position calculated by the self-position calculation unit 53 may be acquired as the position information of the parking position 31. The map generation unit 55 generates relative position data based on the positions of the feature points included in the target data, the position information of the vehicle 1 synchronized therewith, and the position information of the parking position 31. The map generation unit 55 acquires feature amount data from the target data output from the target detection unit 54. The relative position data, feature amount data, and learned target data including the position data of the parking position 31 are stored as map data 56 in the storage device 19b.

[0029] In addition to the learned target data, the map generation unit 55 stores position information of the turning position 32 as map data 56 in the storage device 19b. Furthermore, the map generation unit 55 stores in the storage device 19b the number of captured positioning satellites NUM, the accuracy dilution rate DOP, and the estimated accuracy of the extended Kalman filter (e.g., norms Ns and Nk) when the host vehicle 1 is manually parked at the parking position 31 in order to register the parking position 31. Note that, similar to the first embodiment, the learned target data, the position information of the turning position 32, the number of captured positioning satellites NUM, the accuracy dilution rate DOP, and the estimated accuracy of the extended Kalman filter may be stored in a storage device external to the host vehicle 1 (e.g., a cloud computer).

[0030] The parking assist control unit 51 executes parking assist control to assist the host vehicle 1 in parking the parking position 31 registered in the storage device 19b. The parking assist control unit 51 can be switched between an "automatic start mode," which automatically starts searching for parking positions 31 around the host vehicle 1, and a "manual start mode," which starts searching for the parking position 31 when a user performs an operation (hereinafter sometimes referred to as an "activation operation") to instruct activation of the parking assist control of the host vehicle 1. For example, the activation operation may be an operation of the parking switch 17 by the user. The parking assist control unit 51 receives the host vehicle 1's own position 33 from the host vehicle position calculation unit 53 and acquires information on a pre-registered turning-around position 32 from the storage device 19b. In the automatic start mode, the parking assist control unit 51 determines whether the distance D between the host vehicle 1's own position 33 and the turning-around position 32 is equal to or less than a threshold value Dth. If the distance D is equal to or less than the threshold value Dth, the parking assist control is automatically started. In the manual start mode, when the parking assist control unit 51 receives a start-up operation from the user, it determines whether the distance D is equal to or less than the threshold value Dth, and starts parking assist control if the distance D is equal to or less than the threshold value Dth.

[0031] The parking assist control unit 51 changes the threshold Dth depending on the detection accuracy of the vehicle's own position. The parking assist control unit 51 may change the threshold Dth depending on the detection accuracy of the vehicle's own position when the vehicle 1 is manually parked at the parking position 31 in order to pre-register the parking position 31, or may change the threshold Dth depending on the detection accuracy of the vehicle's own position when executing parking assist control for the parking position 31 after the parking position 31 has been registered. For example, the parking assist control unit 51 may switch the threshold Dth depending on the detection accuracy of the vehicle's own position by a satellite positioning system. For example, the parking assist control unit 51 may switch the threshold Dth depending on whether the vehicle's own position can be detected by the satellite positioning system. For example, if the detection accuracy of the vehicle's own position by the satellite positioning system is good, the parking assist control unit 51 may set the threshold Dth to a first fixed value D1. If the vehicle's own position cannot be detected by the satellite positioning system, the parking assist control unit 51 may set the threshold Dth to a second fixed value D2 greater than the first fixed value D1 or a value selected by the user. For example, the parking assist control unit 51 may determine that the detection accuracy is good when the mode FIX_TYPE of the position information of the satellite positioning system is "3D FIX" or when the acquisition number NUM is 6 or more and the accuracy degradation rate DOP is less than 3. Also, for example, the parking assist control unit 51 may determine that the vehicle's own position cannot be detected by the satellite positioning system when the mode FIX_TYPE is "NO FIX" or the acquisition number NUM is 3 or less. In other cases, the parking assist control unit 51 may determine that the vehicle's own position can be detected by the satellite positioning system but the detection accuracy is poor.

[0032] Furthermore, for example, the parking assist control unit 51 may change the threshold value Dth depending on the detection accuracy of the vehicle's own position using autonomous navigation. For example, the threshold value Dth may be set higher when the detection accuracy of the vehicle's own position using autonomous navigation is low compared to when it is high. For example, when the parking assist control unit 51 determines that the vehicle's own position can be detected using a satellite positioning system but the detection accuracy is poor, the parking assist control unit 51 may set a higher threshold value Dth when the detection error using autonomous navigation is large compared to when it is small. For example, the larger the detection error using autonomous navigation, the higher the threshold value Dth may be set. For example, the parking assist control unit 51 may set an additional value ΔD that increases as the detection error using autonomous navigation increases, and may set the sum of the first fixed value D1 and the additional value ΔD as the threshold value Dth = D1 + ΔD. The parking assist control unit 51 may use the norm Ns of the variance S of the estimated value of the Kalman filter or the norm Nk of the Kalman gain K as an index of the detection error using autonomous navigation.

[0033] The parking assist control unit 51 outputs a parking position calculation command to the target parking position detection unit 57 when starting to search for the parking position 31. The HMI control unit 50 may display a second guidance screen that notifies the user that the controller 19 is searching for parking positions 31 around the vehicle 1. FIG. 7 is a schematic diagram of an example of the second guidance screen. The second guidance screen 40b includes a captured image 41, an overhead image 42, a message display area 43, and an end button 45. See FIG. 6 . Upon receiving the parking position calculation command, the target parking position detection unit 57 receives the target data output from the target detection unit 54 as target data of surrounding targets, and simultaneously receives the vehicle's own position in the map coordinate system. The target parking position detection unit 57 reads the learned target data stored in the storage device 19b as map data 56, matches the learned targets stored in the map data 56 with the surrounding targets, and associates targets with the same characteristic points. The target parking position detection unit 57 calculates the current relative position of the vehicle 1 with respect to the parking position 31 based on the relative positional relationship between the surrounding targets and the vehicle 1 and the relative positional relationship between the learned targets associated with the surrounding targets and the parking position 31. For example, if the surrounding targets are (x ｉ , y ｉ ) and the surrounding targets (x ｉ, y ｉ ) are the learned targets associated with each of the ｍｉ , y ｍｉ ) (i=1 to N). The target parking position detection unit 57 calculates the affine transformation matrix M ａｆｆｉｎｅ１ Calculate.

[0034]

[0035] The target parking position detection unit 57 detects the position (targetx) of the parking position 31 on the map coordinate system stored in the map data 56. ｍ , target ｍ ) and the following equation, the position (targetx, targety) of the parking position 31 on the vehicle coordinate system is estimated.

[0036]

[0037] When the target parking position detection unit 57 successfully estimates the position of the parking position 31 in the vehicle coordinate system (i.e., when matching between the learned objects and the surrounding objects is successful), the HMI control unit 50 displays the first guidance screen 40a shown in FIG. 3 on the display device of the HMI 13. When the parking start button 44 is operated on the first guidance screen 40a, the parking position 31 is set as the target parking position, and assistance for parking the host vehicle 1 at the target parking position begins. The target trajectory generation unit 59 calculates a target parking path from the current position of the host vehicle 1 to the parking position 31. The target trajectory generation unit 59 calculates a target vehicle speed profile, which is a target value for the vehicle speed of the host vehicle 1 on the target parking path. The steering control unit 60 controls the steering actuator 21a so that the host vehicle 1 travels along the target parking path. The vehicle speed control unit 61 controls the accelerator actuator 21b and the brake actuator 21c so that the vehicle speed of the host vehicle 1 changes in accordance with the target vehicle speed profile. When the host vehicle 1 reaches the target parking position and the parking assist control is completed, the parking assist control unit 51 activates the parking brake 20 and switches the shift position to the parking range.

[0038] FIG. 8 is a flowchart of the parking assistance method of the second embodiment. In step S10, the controller 19 acquires pre-stored learned target data and the turning position 32 from the storage device 19b. In step S11, the controller 19 detects the vehicle's own position 33. In step S12, the controller 19 sets the threshold Dth according to the detection accuracy of the vehicle's own position 33. FIG. 9 is a flowchart of an example of a method for setting the threshold Dth. In step S20, the controller 19 determines whether the detection accuracy of the vehicle's own position by the satellite positioning system is good or not. If the detection accuracy is good (step S20: Y), the process proceeds to step S21. If the detection accuracy is not good (step S20: N), the process proceeds to step S22. In step S21, the controller 19 sets the threshold Dth to a first fixed value D1. The process then ends.

[0039] In step S22, the controller 19 determines whether or not its own position can be detected by the satellite positioning system. If its own position can be detected (step S22: Y), the controller 19 determines that the accuracy of its own position detection by the satellite positioning system is poor, and the process proceeds to step S23. If its own position cannot be detected (step S22: N), the process proceeds to step S25. In step S23, the controller 19 sets an additional value ΔD according to the accuracy of its own position detection by autonomous navigation. In step S24, the controller 19 sets the sum of the first fixed value D1 and the additional value ΔD as a threshold value Dth = D1 + ΔD. The process then ends. In step S25, the controller 19 sets the threshold value Dth to a second fixed value D2 greater than the first fixed value D1, or a value selected by the user. The process then ends.

[0040] 8 . In step S13, the controller 19 determines whether the distance D between the host vehicle 1's own position 33 and the turning position 32 is equal to or less than the threshold value Dth. If the distance D is not equal to or less than the threshold value Dth (step S13: N), the process ends without displaying guidance for the parking position 31. In this case, parking assistance for the host vehicle 1 to the target parking position is not performed. If the distance D is equal to or less than the threshold value Dth (step S13: Y), the process proceeds to step S14. In step S14, the controller 19 detects surrounding objects. In step S15, the controller 19 calculates the relative position of the parking position 31 with respect to the host vehicle 1, and displays the first guidance screen 40a on the display device of the HMI 13. In step S16, the controller 19 calculates a target parking path from the current position of the host vehicle 1 to the parking position 31. In step S17, the controller 19 performs parking assistance control for the host vehicle 1 based on the calculated target parking path. The process then ends.

[0041] (Effects of the Embodiment) (1) The controller 19 acquires information about the parking position when parking and information about the turning point, which is the point where the vehicle turned when parking the vehicle in the parking position, from a storage device that previously stored the information when parking. The controller 19 detects the vehicle's current position, which is the vehicle's own position. The controller 19 sets a threshold value according to the detection accuracy of the vehicle's own position. If the distance between the turning point and the vehicle's own position is equal to or less than the threshold value, the controller 19 guides the user of the vehicle 1 to the parking position as a candidate target parking position. This makes it easier to determine that the vehicle 1 is approaching the parking target position even in places where the detection accuracy of the vehicle's own position is low when presenting guidance about the pre-stored parking target position to the user. (2) The controller 19 may detect the vehicle's own position using a satellite positioning system and switch the threshold value depending on whether the satellite positioning system can detect the vehicle's own position. This allows the threshold value to be changed depending on the detection accuracy of the vehicle's own position when the controller 19 detects the vehicle's own position using the satellite positioning system.

[0042] (3) The controller 19 may detect its own position using a satellite positioning system and set the threshold value according to the number of captured positioning satellites. This allows the threshold value to be changed according to the detection accuracy of its own position when detecting its own position using the satellite positioning system. (4) The controller 19 may detect its own position using a satellite positioning system and set the threshold value according to an index value based on the arrangement state of the captured positioning satellites. This allows the threshold value to be changed according to the detection accuracy of its own position when detecting its own position using the satellite positioning system. (5) When the controller 19 is unable to detect its own position using the satellite positioning system, it may detect its own position based on the detection result at the time when its own position was detected using the satellite positioning system and autonomous navigation. This allows the controller 19 to continue detecting its own position even when its own position cannot be detected using the satellite positioning system.

[0043] (6) The controller 19 does not need to detect the vehicle's own position using the satellite positioning system when the shift position of the vehicle 1 is in a position other than the forward driving position. This makes it possible to prevent a decrease in the detection accuracy of the azimuth angle of the vehicle 1 using the satellite positioning system when the vehicle 1 is not continuing to drive forward. (7) The controller 19 may set a higher threshold value when the detection accuracy of the vehicle's own position using autonomous navigation is low compared to when it is high. This makes it possible to change the threshold value depending on the detection accuracy of the vehicle's own position when detecting the vehicle's own position using autonomous navigation.

[0044] (8) The controller 19 may acquire learned target data from a storage device that stores data representing the relative positional relationship between the parking position and targets existing around the parking position as learned target data, detect the positions of surrounding targets that are targets existing around the vehicle 1, calculate the relative positional relationship between the parking position and the vehicle's own position based on the learned target data and the positions of the surrounding targets, calculate a driving trajectory from the vehicle's own position to the parking position based on the calculated relative positional relationship, and assist the vehicle 1 in parking the target parking position based on the driving trajectory when the parking position is set as the target parking position. This allows the user to use parking assist control that assists the vehicle 1 in parking the pre-registered target parking position.

[0045] All examples and conditional terms described herein are intended for educational purposes to aid the reader in understanding the present invention and the concepts provided by the inventor for the advancement of technology, and should be construed without limitation to the specifically described examples and conditions above, and the configuration of examples herein for illustrating the advantages and disadvantages of the present invention. Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations can be made thereto without departing from the spirit and scope of the present invention.

[0046] 1...Own vehicle, 10...Parking assistance device, 11...Positioning device, 12...Map database, 13...Human machine interface, 14...Shift switch, 15...External sensor, 16...Vehicle sensor, 17...Parking switch, 19...Controller, 19a...Processor, 19b...Storage device, 20...Parking brake, 21a...Steering actuator, 21b...Accelerator actuator, 21c...Brake actuator, 50...HMI control unit, 51...Parking assistance control unit, 52...Image conversion unit, 53...Self-position calculation unit, 54...Target detection unit, 55...Map generation unit, 56...Map data, 57...Target parking position detection unit, 59...Target trajectory generation unit, 60...Steering control unit, 61...Vehicle speed control unit

Claims

1. Acquire information on the parking position when parking was performed and information on the turning point, which is the point where the vehicle turned when parking the vehicle in the parking position, from a storage device that previously stored the information on the parking position and the turning point when parking the vehicle in the parking position, Detecting the current position of the vehicle itself, setting a threshold value according to the detection accuracy of the self-location; When the distance between the turning point and the host position is equal to or less than the threshold value, the parking position is notified to a user of the host vehicle as a target parking position candidate. A parking assistance method comprising:

2. Detecting the self-position using a satellite positioning system; The parking assistance method according to claim 1, wherein the threshold value is switched depending on whether the satellite positioning system is able to detect the vehicle's own position.

3. Detecting the self-position using a satellite positioning system; The parking assistance method according to claim 1, wherein the threshold value is set in accordance with the number of captured positioning satellites.

4. Detecting the self-position using a satellite positioning system; 2. The parking assistance method according to claim 1, wherein the threshold value is set in accordance with an index value based on the arrangement of captured positioning satellites.

5. 2. The parking assistance method according to claim 1, wherein, when the vehicle's own position cannot be detected by a satellite positioning system, the vehicle's own position is detected based on a detection result at the time when the vehicle's own position can be detected by the satellite positioning system and autonomous navigation.

6. The parking assistance method according to any one of claims 2 to 5, characterized in that when the shift position of the vehicle is a position other than a forward driving position, the detection of the vehicle's own position by the satellite positioning system is not performed.

7. The parking assistance method according to claim 5, wherein the threshold value is set to a larger value when the detection accuracy of the vehicle's own position by the autonomous navigation is low compared to when the detection accuracy is high.

8. Acquire learned target data from the storage device that stores data representing a relative positional relationship between the parking position and targets present around the parking position as learned target data; Detecting the positions of surrounding targets that are targets present around the vehicle; Calculating a relative positional relationship between the parking position and the vehicle's own position based on the learned target data and the positions of the surrounding targets; calculating a travel trajectory from the vehicle's own position to the parking position based on the calculated relative positional relationship; When the parking position is set as a target parking position, the parking system assists the host vehicle in parking at the target parking position based on the traveling trajectory.

6. The parking assistance method according to claim 1, wherein the vehicle is driven in a direction parallel to the road surface.

9. A process of acquiring information on the parking position when parking is performed and information on the turning point, which is a point where the vehicle turns when parking the vehicle at the parking position, from a storage device that previously stored the information on the parking position and the turning point when parking the vehicle; A process of detecting a self-position, which is the current position of the vehicle; a process of setting a threshold value according to the detection accuracy of the self-location; a process of informing a user of the host vehicle of the parking position as a target parking position candidate when the distance between the turning point and the host position is equal to or less than the threshold value; A parking assistance device comprising: a controller that executes the above.