Leaning vehicle FCW device and leaning vehicle FCW method

Abstract

Provided is a leaning vehicle forward-collision-warning (FCW) device that is used in a leaning vehicle in which a vehicle body tilts toward a turning inner side when making a turn, said leaning vehicle FCW device comprising: a warning unit that issues a warning to a driver; and one or more control units that execute host vehicle course prediction for predicting the course of a host vehicle and host vehicle peripheral object position detection for detecting the position of an object around the host vehicle, that calculate a possibility of collision between the host vehicle and the object using a result of the hot vehicle course prediction and a result of the host vehicle peripheral object position detection, and that execute warning control for controlling whether a warning is issued by the warning unit on the basis of the possibility of collision. The leaning vehicle FCW device further comprises: a monocular camera that is fixed to the host vehicle and that captures an image of the periphery of the host vehicle; and a turning state detection unit that detects a physical quantity relating to a yaw rate of the host vehicle. The control unit executes the host vehicle peripheral object position detection on the basis of the captured image captured by the monocular camera, and executes the host vehicle course prediction in consideration of the yaw rate of the host vehicle obtained from the detection result of the turning state detection unit, and uses the obtained results to execute the warning control as described in the following situations. Situation 1: When the host vehicle is turning on a road without white lines, if a first preceding vehicle is turning ahead of the host vehicle with the same turning radius as the host vehicle and at a vehicle speed smaller than the vehicle speed of the host vehicle, the control unit executes the warning control so that a warning is issued by the warning unit when the possibility of collision between the host vehicle and the first preceding vehicle becomes equal to or greater than a predetermined collision possibility. Situation 2: When the host vehicle is turning on a road without white lines, if a second preceding vehicle is advancing straight ahead of the host vehicle at a vehicle speed smaller than the vehicle speed of the host vehicle, and the center position in the vehicle width direction of a front wheel of the host vehicle is in a meandering state in which the front wheel is meandering centered on a straight line parallel to the advancing direction of the second preceding vehicle within a range that falls within the vehicle width of the host vehicle, and the center position in the vehicle width direction of the front wheel of the host vehicle is positioned within the vehicle width of the second preceding vehicle when viewed from the advancing direction of the second preceding vehicle, the control unit executes the warning control so that a warning is issued by the warning unit when the possibility of collision between the host vehicle and the second preceding vehicle becomes equal to or greater than a predetermined collision possibility.

Description

FCW device for lean vehicle and FCW method for lean vehicle

[0001] The present disclosure relates to a lean vehicle FCW device and a lean vehicle FCW method that issue a forward collision warning (FCW) to a driver of a lean vehicle.

[0002] Conventionally, FCW devices are known that issue a warning to a driver of a lean-to vehicle based on the possibility of a collision with a surrounding object. A lean-to vehicle turns by tilting its body. An example of a lean-to vehicle is a motorcycle. For example, Patent Document 1 discloses a device that issues a warning based on the positional relationship between a lean-to vehicle and a preceding vehicle traveling in front of the lean-to vehicle when multiple lean-to vehicles are traveling together. Patent Document 2 discloses a system that captures an image of the front using a camera attached to the lean-to vehicle, detects surrounding vehicles using the captured image, and issues a warning.

[0003] International Publication No. 2021 / 060357 Special Publication No. 2021-526681

[0004] Lean-backed vehicles tend to be lighter and more compact than non-lean-backed vehicles, which do not tilt their bodies left or right when turning. Therefore, lean-backed vehicles are more likely to sway when subjected to external disturbances, such as uneven road surfaces, while traveling straight ahead than non-lean-backed vehicles. The technologies disclosed in Patent Documents 1 and 2 do not take into consideration FCW control in situations where sway occurs due to external disturbances, such as uneven road surfaces, while a lean-backed vehicle is traveling straight ahead.

[0005] An object of the present disclosure is to provide an FCW device for a lean vehicle and an FCW method for a lean vehicle that perform FCW control different from those proposed in the past.

[0006] The present inventors have considered activating an FCW device while a lean vehicle is turning. The FCW device detects objects around the host vehicle and then selects from the detected objects those objects that are at risk of colliding with the host vehicle. A numerical value indicating the degree of risk of the host vehicle colliding with the object varies depending on whether the object is on the path of the host vehicle. The present inventors have conceived the idea that by predicting the path of the host vehicle in consideration of the turning state of the host vehicle, it is possible to execute warning control for objects on the turning path of the host vehicle.

[0007] Furthermore, the inventors of the present application have noticed that lean-to-steer vehicles are more susceptible to swaying of the vehicle body when traveling straight due to disturbances such as unevenness in the road surface than four-wheeled vehicles. If the vehicle body sways when traveling straight due to the influence of disturbances, and if the swaying is recognized as a turn and a path prediction is performed based on that, there is a possibility that a predicted path different from the actual path will be obtained. Therefore, the inventors of the present application have studied an FCW device for a lean-to-steer vehicle that can perform FCW control that takes into account the swaying state that occurs due to the influence of disturbances when traveling straight and the turning state.

[0008] While expanding the range of situations in which warning control can be performed using FCW devices, the bodies of lean vehicles are smaller than those of four-wheeled vehicles, limiting the space available for mounting the device. This means that it is necessary to reduce the processing load and increase the design freedom of hardware resources.

[0009] In this way, when the FCW device is operated while a lean vehicle is turning, it is necessary to suppress an increase in processing load while taking into account the wobbling state that occurs due to external disturbances when the lean vehicle is traveling straight and the turning state.

[0010] In order to address both of the conflicting issues described above, the FCW device for a lean vehicle according to the present disclosure employs the following configuration.

[0011] An FCW device for a lean vehicle according to one embodiment of the present disclosure includes an alarm unit that issues an alarm to the driver, and one or more control units that perform a host vehicle path prediction that predicts a path of the host vehicle and a host vehicle peripheral object position detection that detects the positions of objects around the host vehicle, calculate a possibility of a collision between the host vehicle and an object using the results of the host vehicle path prediction and the results of the host vehicle peripheral object position detection, and perform alarm control that controls whether or not an alarm is issued by the alarm unit based on the possibility of collision. The FCW device for a lean vehicle is used in a lean vehicle whose body leans to the inside of a turn when turning, and further includes a monocular camera that is fixed to the host vehicle and captures images of the periphery of the host vehicle, and a turning state detection unit that detects physical quantities related to the yaw rate of the host vehicle, and the control unit performs position detection of objects around the host vehicle based on images captured by the monocular camera, and performs the host vehicle path prediction that takes into account the yaw rate of the host vehicle obtained from the detection result of the turning state detection unit, and uses the obtained results to perform the alarm control as described in each of the following situations. Situation 1: When the host vehicle is turning on a road without white lines and a first leading vehicle is turning ahead of the host vehicle at a speed slower than the host vehicle and with the same turning radius as the host vehicle, the control unit executes warning control so that the warning unit issues a warning when the possibility of a collision between the host vehicle and the first leading vehicle reaches or exceeds a predetermined collision possibility. Situation 2: When the host vehicle is traveling straight on a road without white lines and a second leading vehicle is traveling straight ahead of the host vehicle at a speed slower than the host vehicle, the host vehicle is in a meandering state where the center position of the front wheels in the vehicle width direction of the host vehicle is centered on a straight line parallel to the traveling direction of the second leading vehicle within the vehicle width of the host vehicle, and the center position of the front wheels in the vehicle width direction of the host vehicle is located within the vehicle width of the second leading vehicle as viewed from the traveling direction of the second leading vehicle, the control unit executes warning control so that the warning unit issues a warning when the possibility of a collision between the host vehicle and the second leading vehicle reaches or exceeds a predetermined collision possibility.

[0012] In the above configuration, the control unit may execute the warning control as described in the following situations: Situation 3: When the host vehicle is traveling straight on a road without white lines, a third leading vehicle is traveling straight ahead of the host vehicle at the same vehicle speed as the host vehicle, the host vehicle is in a serpentine state where the center positions of the front wheels in the vehicle width direction of the host vehicle are serpentine around a straight line parallel to the traveling direction of the third leading vehicle within a range that fits within the vehicle width of the host vehicle, the center positions of the front wheels in the vehicle width direction of the host vehicle are located within the vehicle width of the third leading vehicle as viewed from the traveling direction of the third leading vehicle, and a fourth leading vehicle is turning at a speed slower than the vehicle speed of the host vehicle along a turning path predicted from a yaw rate occurring in the host vehicle traveling straight in the serpentine state, the control unit executes warning control so as not to issue a warning by the warning unit.

[0013] In the above configuration, the FCW device for a lean vehicle may further include a vehicle speed detection unit that detects a vehicle speed of the host vehicle. The control unit may determine whether the host vehicle is turning based on a yaw rate obtained from a detection result of the turning state detection unit, and when it is determined that the host vehicle is turning, perform the host vehicle course prediction based on the yaw rate obtained from the detection result of the turning state detection unit and the vehicle speed detected by the vehicle speed detection unit, and when the host vehicle is in the meandering state, perform the host vehicle course prediction by assuming that the host vehicle is traveling straight regardless of the value of the yaw rate.

[0014] In the above configuration, if the control unit defines the yaw rate as positive when the vehicle turns to the right relative to the direction of travel and as negative when the vehicle turns to the left relative to the direction of travel, and if the duration for which the sign of the yaw rate obtained from the detection result of the turning state detection unit continues to show the same sign is shorter than a predetermined threshold time, the control unit may determine that the vehicle is traveling straight regardless of the value of the yaw rate and perform the vehicle path prediction.

[0015] An FCW method for a lean vehicle according to one embodiment of the present disclosure includes a warning unit that issues a warning to a driver, and one or more control units that perform host vehicle path prediction that predicts a path of the host vehicle and host vehicle peripheral object position detection that detects positions of objects around the host vehicle, calculate a possibility of a collision between the host vehicle and an object using the result of the host vehicle path prediction and the result of the host vehicle peripheral object position detection, and perform warning control that controls whether or not to issue a warning by the warning unit based on the possibility of collision, and is performed by an FCW device for a lean vehicle that is used in a lean vehicle whose body leans toward the inside of a turn when turning. The FCW method includes the steps of capturing an image of the surroundings of the host vehicle with a monocular camera fixed to the host vehicle, acquiring the captured image from the monocular camera and detecting the positions of objects around the host vehicle, acquiring a yaw rate of the host vehicle from a detection result from a turning state detection unit that detects a physical quantity related to the yaw rate of the host vehicle, predicting a course of the host vehicle taking into account the yaw rate obtained from the detection result from the turning state detection unit, and executing the warning control as described in each of the following situations using the result of the course of the host vehicle prediction and the result of the position detection of the objects around the host vehicle: Situation 1: While the host vehicle is turning on a road without white lines, when a first leading vehicle is turning ahead of the host vehicle at a vehicle speed slower than the vehicle speed of the host vehicle and with the same turning radius as the host vehicle, the control unit executes the warning control so that the warning unit issues a warning when the likelihood of a collision between the host vehicle and the first leading vehicle reaches or exceeds a predetermined likelihood of collision. Situation 2: When the host vehicle is traveling straight on a road without white lines, and a second leading vehicle is traveling straight ahead of the host vehicle at a speed slower than the host vehicle, and the center position of the vehicle width direction of the front wheels of the host vehicle is in a serpentine state, snaking within a range that fits within the vehicle width of the host vehicle around a straight line parallel to the direction of travel of the second leading vehicle, and the center position of the vehicle width direction of the front wheels of the host vehicle is located within the vehicle width of the second leading vehicle when viewed from the direction of travel of the second leading vehicle, the control unit executes the warning control so that the warning unit issues a warning when the possibility of a collision between the host vehicle and the second leading vehicle exceeds a predetermined collision possibility.

[0016] The above configuration may further include a step of executing the warning control as described in the following situations: Situation 3: When the host vehicle is traveling straight on a road without white lines, a third leading vehicle is traveling straight ahead of the host vehicle at the same vehicle speed as the host vehicle, the host vehicle is in a serpentine state where the center positions of the front wheels in the vehicle width direction of the host vehicle are serpentine around a straight line parallel to the traveling direction of the third leading vehicle within a range that fits within the vehicle width of the host vehicle, the center positions of the front wheels in the vehicle width direction of the host vehicle are located within the vehicle width of the third leading vehicle as viewed from the traveling direction of the third leading vehicle, and a fourth leading vehicle is turning at a vehicle speed slower than the vehicle speed of the host vehicle along a turning path predicted from a yaw rate occurring in the host vehicle traveling straight in the serpentine state, the control unit executes the warning control so as not to issue a warning by the warning unit.

[0017] In the above configuration, it is determined whether the host vehicle is turning based on the yaw rate obtained from the detection result of the turning state detection unit, and if it is determined that the host vehicle is turning, the host vehicle course prediction is performed based on the yaw rate obtained from the detection result of the turning state detection unit and the vehicle speed detected by a vehicle speed detection unit that detects the vehicle speed of the host vehicle, and if the host vehicle is in the serpentine state, the host vehicle course prediction may be performed assuming that the host vehicle is traveling straight regardless of the value of the yaw rate.

[0018] In the above configuration, if the yaw rate when the vehicle turns to the right relative to the direction of travel is defined as positive, and the yaw rate when the vehicle turns to the left relative to the direction of travel is defined as negative, if the duration during which the sign of the yaw rate obtained from the detection result of the turning state detection unit continues to show the same sign is shorter than a predetermined threshold time, the vehicle's path prediction may be performed assuming that the vehicle is traveling straight, regardless of the value of the yaw rate.

[0019] According to the FCW device for a lean vehicle and the FCW method for a lean vehicle of the present disclosure, it is possible to provide an FCW device for a lean vehicle and an FCW method for a lean vehicle that perform FCW control different from that proposed in the past.

[0020] [Lean Vehicle] A lean vehicle according to the present disclosure is a vehicle whose body leans to the right when turning right and to the left when turning left. The left and right directions are those seen from the perspective of a driver driving the lean vehicle. In this disclosure, the right-hand side, left-hand side, front, and rear, as seen from the driver of the lean vehicle, are referred to as the right, the left, the front, and the rear, respectively. The term "host vehicle" used in this disclosure refers to a lean vehicle. Lean vehicles include motorcycles. The term "host vehicle" used in this disclosure refers to a lean vehicle. The tilt of a lean vehicle refers to the body of the lean vehicle being tilted to the left or right with respect to the vertical direction. The tilt of a lean vehicle can be expressed by the tilt angle between the body of the lean vehicle and the vertical direction. When the lean vehicle is traveling straight, the tilt angle is 0 degrees, and when the lean vehicle is turning, the tilt angle is greater than 0 degrees. The lean vehicle includes at least one front wheel and at least one rear wheel. For example, a lean vehicle may have two front wheels and one or two rear wheels, or one front wheel and one or two rear wheels. The lean vehicle may have steered front wheels or steered rear wheels. The lean vehicle runs by driving the drive wheels with a drive source. The drive source may be an internal combustion engine, an electric motor, or a hybrid drive source including an engine and an electric motor.

[0021] [FCW Device for Lean Vehicle] The FCW device for a lean vehicle described in the present disclosure includes an alarm unit, one or more control units, a monocular camera, and a turning state detection unit. The FCW device may further include a vehicle speed detection unit. The FCW device is mounted on a lean vehicle for use.

[0022] [White Lines] The white lines described in this disclosure refer to lines drawn on roads to indicate the vehicle's travel lane, and are not intended to be limited to a specific color. For example, the lines may be drawn in other colors, such as yellow. Such road lines may also be referred to as roadside lines, shoulder strips, diagonal boundary lines, or dividing lines. FCW devices can perform FCW control without detecting white lines. In this disclosure, when a vehicle is described as traveling on a road without white lines, this indicates that FCW control can be performed even on roads without white lines, and is not intended to limit roads on which lean vehicles travel to roads without white lines.

[0023] [Situation] In this disclosure, situations described with numbers, such as "Situation 1," indicate examples of situations in which the operation of the FCW device can be confirmed. One of the characteristics of the FCW device is that it can perform processes such as detecting the position of objects around the vehicle and predicting the vehicle's path, and can change whether or not to issue an alarm depending on the situation. Each situation described with a number indicates that the alarm control performed by the FCW device can be confirmed by recreating this situation, and it is not intended to limit the operation of the FCW device to the described situation.

[0024] [Meandering State] The serpentine state described in this disclosure includes a state in which the center position of the front wheels of a lean vehicle in the vehicle width direction snakes around a straight line parallel to the traveling direction of a preceding vehicle traveling straight ahead of the lean vehicle within the vehicle width of the lean vehicle. In other words, if a strip-shaped area of ​​the same width as the lean vehicle is set on the road, the serpentine state includes the traveling state of a lean vehicle that travels while changing the direction and position of the front wheels within this area. The serpentine state is merely an example of a traveling state that illustrates one of the characteristics of the FCW control executed when a lean vehicle staggers, and is not intended to limit the traveling state that is considered to be a serpentine state. For convenience of explanation, the serpentine state is used, but it is not intended to be limited to a traveling state in which the direction of the front wheels is continuously changed left and right. The number of times the direction and position of the front wheels change in the serpentine state may be only one. For example, a meandering state is also defined as a case in which a lean vehicle, while traveling straight, changes the direction of its front wheels once to the right or left, then returns to its original position and continues traveling straight from a position to the right or left of the original straight-travel path.A meandering state is also defined as a case in which a lean vehicle changes the direction of its front wheels once to the right or left, then changes the direction of its front wheels again to the left or right, then returns to its original straight-travel path and continues traveling straight.If a lean vehicle has multiple front wheels, it is sufficient to determine whether or not the vehicle is in a meandering state for any one of the front wheels.

[0025] [Warning Unit] The warning unit described in the present disclosure is a warning device that issues a warning to at least the driver of a lean vehicle. The warning unit issues a warning targeting at least one of the senses of hearing, seeing, and touch. A warning targeting the sense of hearing may be issued by emitting a voice or warning sound from a speaker. A warning targeting the sense of sight may be issued by displaying information on a display device or illuminating a light-emitting device. Warning devices such as speakers, display devices, and light-emitting devices may be installed, for example, on the handlebars or in their vicinity. If the driver wears a helmet, the warning device may be mounted on the helmet. Devices such as a speedometer and a navigation device provided in the lean vehicle may be used as warning devices. A warning targeting the sense of touch may be issued by vibrating at least one of the handlebars, helmet, and seat.

[0026] [Control Unit] The control unit described in the present disclosure controls each unit constituting the FCW device. The control unit controls each unit to realize the functions and operations of the FCW device described in the present disclosure. The control unit is a control device that executes FCW control. FCW control includes host vehicle path prediction, host vehicle peripheral object position detection, and warning control. The FCW device may include multiple control units, and multiple processes may be executed in parallel by separate control units. For example, a process related to host vehicle path prediction and a process related to host vehicle peripheral object position detection may be executed in parallel simultaneously. The control unit calculates a numerical value indicating the likelihood of a collision between the host vehicle and the object based on the host vehicle path prediction result and the host vehicle peripheral object position detection result. For example, the time to collision (TTC) may be used as the numerical value indicating the likelihood of a collision. Furthermore, the numerical value indicating the likelihood of a collision may be, for example, the distance between the leaning vehicle and the object or the relative movement speed. The control unit determines whether an alarm is necessary and when to issue the alarm based on the possibility of a collision, and executes alarm control to issue an alarm from the alarm device based on the determination result. The control unit can execute alarm control continuously while the lean vehicle is traveling, regardless of whether the lean vehicle is traveling straight or turning. A program corresponding to the control unit is prepared in advance in a non-volatile storage device, and the function and operation of the control unit are realized by executing this program by predetermined hardware. The control unit may be realized by an ECU (Electronic Control Unit) for vehicle control, or the FCW device may have a dedicated control unit.

[0027] [Monocular Camera] The monocular camera described in this disclosure is an imaging device that captures images of the periphery of a lean vehicle. The FCW device can perform FCW control using a single monocular camera, which is smaller than a stereo camera. The monocular camera is fixed to the lean vehicle and used. The monocular camera can capture images of the area ahead of the road on which the lean vehicle is traveling. The monocular camera captures images of leading vehicles traveling ahead of the lean vehicle while the lean vehicle is traveling straight or turning, vehicles stopped or parked in front of the lean vehicle, and other obstacles. The leading vehicles captured by the monocular camera include vehicles traveling on a predicted path obtained by host vehicle path prediction and vehicles traveling at positions outside the predicted path. The monocular camera captures moving images or continuously captures still images, thereby continuously capturing images of objects around the lean vehicle.

[0028] [Turning State Detection Unit] The turning state detection unit described in the present disclosure is a detection device that detects a physical quantity related to the yaw rate of a lean vehicle. The yaw rate and yaw angle of a lean vehicle can be determined from the physical quantity detected by the turning state detection unit. For example, the turning state detection unit may detect either the yaw rate or the yaw angle and calculate the other based on the detection result. For example, an IMU (Inertial Measurement Unit) may be used as the turning state detection unit. Other devices such as a GPS (Global Positioning System) or a gyro sensor may also be used as the turning state detection unit.

[0029] [Vehicle Speed ​​Detector] The vehicle speed detector described in the present disclosure is a detector for detecting the traveling speed of a lean vehicle. For example, a device that detects the vehicle speed based on the rotation speed of a front wheel or a rear wheel and the outer diameter of a tire acquired using a rotation sensor is used as the vehicle speed detector. Other devices, such as a device that detects the vehicle speed from position information obtained by GPS, may also be used as the vehicle speed detector.

[0030] [Vehicle Path Prediction] The vehicle path prediction described in the present disclosure is a process for predicting the path of the vehicle. Vehicle path prediction also includes predicting the path on an image captured by a monocular camera. Note that predicting the path on the captured image may be performed by mapping the predicted path of the vehicle in three-dimensional coordinates in the real world onto corresponding planar coordinates on the captured image. Planar coordinates on the captured image are, for example, an orthogonal coordinate system with the center of the captured image as the origin. When the lean vehicle is traveling straight, the FCW device can predict the path of the lean vehicle on the image captured by the monocular camera based on the mounting position, mounting angle, imaging direction, imaging range, etc. of the monocular camera on the lean vehicle. When the lean vehicle is turning, the FCW device can predict a curved path as the path of the turning lean vehicle based on the detection result by the turning state detection unit. When a lean vehicle is turning, the FCW device can predict the path of the turning lean vehicle by curvature-correcting the predicted path on the captured image, which is obtained assuming that the lean vehicle is traveling straight, based on the detection results by the turning state detection unit.The FCW device can predict the path of the turning lean vehicle in approximately real time after acquiring an image captured by the monocular camera while the lean vehicle is traveling.

[0031] [Position Detection of Objects Surrounding the Vehicle] The position detection of objects surrounding the vehicle described in the present disclosure is a process of detecting objects around the vehicle and identifying the position of each object. The position detection of objects around the vehicle is performed using images captured by a monocular camera. Here, the position of an object may be a position on the image captured by the monocular camera. By performing image analysis to detect objects on the image captured by the monocular camera, the objects appearing in the captured image and the positions of each object are detected. Such image analysis is sometimes referred to as object detection, object recognition, etc. Objects detected from the captured image include a preceding vehicle traveling ahead of the lean-back vehicle while the lean-back vehicle is traveling straight or turning, a stopped or parked vehicle ahead, and other obstacles. The preceding vehicle detected from the captured image includes a vehicle traveling on a predicted path obtained by vehicle path prediction and a vehicle traveling at a position outside the predicted path. When a detected vehicle is referred to as a "leading vehicle," it refers to a vehicle traveling ahead of the lean-back vehicle in the same direction as the lean-back vehicle. The FCW device can detect the positions of objects around the vehicle in approximately real time after capturing an image using a monocular camera while the vehicle is traveling lean.

[0032] [Collision Possibility] The collision probability described in the present disclosure is a numerical value indicating the possibility of a collision between a lean vehicle and a surrounding object. For example, the relative movement speed of the object relative to the lean vehicle, the distance between the lean vehicle and the object, and the time until the lean vehicle collides with the object can be used as the collision probability. The collision probability is calculated based on the predicted path of the host vehicle obtained by performing host vehicle path prediction, the position of each object obtained by performing position detection of objects around the host vehicle, and the relative movement between each detected object and the lean vehicle. For example, the position detection of objects around the host vehicle determines the distance from the detected object to the lean vehicle in the captured image. The direction and movement speed of the detected object relative to the lean vehicle are determined by comparing multiple consecutively captured images. The time until collision is determined based on the distance from the object to the lean vehicle and the relative movement speed. Alarm control is performed to determine whether and when an alarm should be issued by the alarm unit based on the result of comparing the value indicating the collision probability with a threshold value prepared in advance according to the type of collision probability. For example, when the time to collision (TTC) is used as the collision probability, a predetermined time is set as a threshold, and when the time to collision reaches the threshold time, alarm control is performed to issue an alarm.

[0033] [Hardware Configuration] The FCW device according to the present disclosure is characterized by performing FCW control that has not been performed before. The hardware configuration of the FCW device according to the present disclosure and a lean vehicle equipped with the FCW device can be implemented by a person skilled in the art using the hardware configurations of devices and lean vehicles known in prior art documents, other publicly known documents, and conventional technology. Therefore, a detailed description of the hardware configuration of the FCW device and the lean vehicle will be omitted.

[0034] [Others] In this disclosure, when a process is described as being performed "based on A" or "taking A into consideration," the process is performed using A, but the information used is not limited to A, and information other than A may also be used. In this disclosure, when "at least one" is used in conjunction with an option, this means that all possible combinations of multiple options are included. In this disclosure, when "including," "comprising," "having," and their derivatives are used, this means that other content may be included in addition to the listed content. In this disclosure, when "may" or "may" is used, this means that this is a non-exclusive example and is not limited to the described example. In this disclosure, unless the number of components is clearly specified, the number of components may be one or more. Unless otherwise defined, the terms used in this disclosure have the general meaning understood by those skilled in the art of FCW control. The FCW device according to the present disclosure is not limited to the configurations described in the following embodiments or the configurations shown in the drawings. The FCW device according to the present disclosure can be implemented by combining multiple embodiments described below. The FCW device according to the present disclosure can also be implemented in forms other than the embodiments described below, or by modifying the embodiments described below.

[0035] Fig. 1 is a diagram for explaining an overview of an FCW device for a lean vehicle according to a first embodiment of the present disclosure. Fig. 2 is a diagram for explaining an overview of an FCW device for a lean vehicle according to a second embodiment of the present disclosure. Fig. 3 is a diagram for explaining an overview of an FCW device for a lean vehicle according to a third embodiment of the present disclosure. Fig. 4 is a diagram for explaining an example of a process for determining whether a lean vehicle has started to turn or has stumbled while traveling straight.

[0036] [First Embodiment] An FCW device for a lean vehicle according to a first embodiment of the present disclosure will be described with reference to Fig. 1. As shown in Fig. 1, an FCW device 2 for a lean vehicle is provided on a lean vehicle 1 that turns by tilting the vehicle body toward the inside of the turn. The tilt angle θ shown in Fig. 1 indicates the tilt angle of the lean vehicle 1 with respect to the vertical direction. When the lean vehicle 1 is traveling straight, the tilt angle θ is 0 degrees, and when turning, the tilt angle θ is greater than 0 degrees.

[0037] The FCW device 2 includes an alarm unit 21 , one or more control units 22 , a monocular camera 23 , and a turning state detection unit 24 .

[0038] The warning unit 21 issues a warning to the driver of the lean vehicle 1. The control unit 22 predicts the path of the lean vehicle 1, i.e., the host vehicle, and detects the positions of objects around the host vehicle. The control unit 22 calculates the possibility of a collision using the results of the host vehicle path prediction and the results of the position detection of objects around the host vehicle. The control unit 22 executes warning control, which controls whether or not the warning unit 21 issues a warning and the timing of issuing the warning, based on the possibility of a collision.

[0039] As shown within the dashed line frame in FIG. 1, the FCW device 2 executes FCW control including vehicle path prediction, position detection of objects around the vehicle, and warning control.

[0040] A monocular camera 23 fixed to the body of the lean vehicle 1 captures images of the vehicle periphery including the area ahead of the lean vehicle 1. The control unit 22 acquires the captured image captured by the monocular camera 23 (A). The turning state detection unit 24 detects a physical quantity related to the yaw rate of the body of the lean vehicle 1. The control unit 22 acquires the yaw rate based on the physical quantity detected by the turning state detection unit 24 (B).

[0041] The control unit 22 performs position detection of objects around the vehicle based on the captured image (C). The control unit 22 performs vehicle path prediction taking the yaw rate into consideration (D). The control unit 22 performs warning control (E) using the results obtained by detecting the positions of objects around the vehicle and the results obtained by predicting the vehicle path so that the warning unit 21 issues a warning in situations 1 and 2 shown in FIG. 1 .

[0042] Situations 1 and 2 shown in Figure 1 show the positional relationship between the lean vehicle 1 while it is traveling and preceding vehicles 101, 102 detected by detecting the positions of objects around the vehicle, as viewed from above. The dashed and dotted lines shown in Situations 1 and 2 are the predicted paths of the lean vehicle 1 obtained by performing host vehicle path prediction. The dashed and dotted lines are the paths of the lean vehicle 1 obtained by performing host vehicle path prediction. The dashed lines are the paths that both ends of the lean vehicle 1 in the vehicle width direction will take when the lean vehicle 1 travels along the obtained path. If an object is present within the band-shaped area indicated by the two dashed lines, there is a possibility that the lean vehicle 1 will collide with this object while continuing to travel. For this reason, warning control is executed using the band-shaped area indicated by the dashed lines as the predicted path.

[0043] In situation 1, while the lean vehicle 1 is turning on a road without white lines, the first leading vehicle 101 is turning with the same turning radius as the lean vehicle 1 and at a vehicle speed V2 that is slower than the vehicle speed V1 of the lean vehicle 1 (V2<V1). The first leading vehicle 101 is turning ahead of the lean vehicle 1. The first leading vehicle 101 is turning on the predicted path of the lean vehicle 1.

[0044] In situation 1, the control unit 22 executes warning control so that the warning unit 21 issues a warning when the possibility of a collision between the lean vehicle 1 and the first leading vehicle 101 becomes equal to or greater than a predetermined possibility of collision. For example, the control unit 22 controls the warning unit 21 to issue a warning when the distance between the lean vehicle 1 and the first leading vehicle 101 becomes a predetermined distance. For example, the control unit 22 controls the warning unit 21 to issue a warning when the relative speed between the lean vehicle 1 and the first leading vehicle 101 becomes a predetermined speed. For example, the control unit 22 controls the warning unit 21 to issue a warning when the time to collision becomes a predetermined time.

[0045] In situation 2, the lean vehicle 1 is traveling straight on a road without white lines at the same vehicle speed V1 as in situation 1, while the second leading vehicle 102 is traveling straight ahead of the vehicle at a vehicle speed V2 that is slower than the vehicle's speed (V2<V1). Although the lean vehicle 1 is traveling straight, the center position of the front wheels in the vehicle width direction is meandering within a range that falls within the vehicle width W of the lean vehicle 1, centered on a straight line parallel to the traveling direction of the second leading vehicle 102 traveling straight. Furthermore, the lean vehicle 1 is traveling in such a way that the center position of the front wheels in the vehicle width direction is located within the vehicle width of the second leading vehicle 102 when viewed from the traveling direction of the second leading vehicle 102.

[0046] In situation 2, the control unit 22 executes warning control so that the warning unit 21 issues a warning when the possibility of a collision between the lean vehicle 1 and the second leading vehicle 102 reaches or exceeds a predetermined collision possibility. As in situation 1, the warning control is performed based on any one of the distance between the lean vehicle 1 and the first leading vehicle 101, the relative speed between the lean vehicle 1 and the first leading vehicle 101, or the time to collision.

[0047] When the lean vehicle 1 moves straight while meandering, as in situation 2, the yaw rate of the lean vehicle 1 may be greater than when moving straight. If the vehicle path prediction is performed based on the yaw rate obtained at this time, a predicted path 200 that is curved similar to the turning path in situation 1 is obtained, as shown in the diagram of situation 2, for example. If warning control is performed based on this predicted path 200, the second leading vehicle 102 is deemed not to be on the predicted path, and there is a risk that the second leading vehicle will be excluded from the list of vehicles to be warned. The control unit 22 avoids this by distinguishing between a turning lean vehicle 1 and a lean vehicle 1 moving straight while meandering.

[0048] The control unit 22 determines whether the lean vehicle 1 has started to turn or has become swaying while traveling straight. If it is determined that the lean vehicle 1 has become swaying while traveling straight and has become swaying, the control unit 22 can execute warning control without using the predicted path 200 at the time of turning determination. A method for determining the swaying state will be described later.

[0049] In this way, the FCW device 2 predicts the path of the turning lean vehicle 1 and controls the alarm unit 21 to issue an alarm when the possibility of a collision with an object on the predicted path reaches a predetermined collision probability. If the lean vehicle 1 traveling straight starts to snake, the FCW device 2 can determine that the lean vehicle 1 traveling straight is in a snake state and execute alarm control in the same way as when traveling straight. Situations 1 and 2 are merely examples to illustrate this, and the alarm control by the FCW device 2 is not limited to Situations 1 and 2. For example, when the first leading vehicle 101 in Situation 1 is stopped on the road, alarm control is executed in the same way as in Situation 1 described above. For example, when the second leading vehicle 102 in Situation 2 is stopped on the road, alarm control is executed in the same way as in Situation 2 described above. The FCW device 2 can also execute alarm control in various other situations based on the path of the lean vehicle 1 predicted by performing host vehicle path prediction, the position of the object detected by position detection of the object around the host vehicle, and the relative movement between the lean vehicle 1 and the object.

[0050] Second Embodiment A lean vehicle FCW device 2 according to a second embodiment of the present disclosure will be described with reference to Fig. 2. Below, content that overlaps with the description of the first embodiment will be omitted, and only content necessary to describe the FCW device 2 of the second embodiment will be described.

[0051] The FCW device 2 according to the second embodiment has the same configuration as the FCW device 2 according to the first embodiment. The control unit 22 executes host vehicle path prediction and host vehicle peripheral object position detection as described in the first embodiment. The control unit 22 executes warning control so that the warning unit 21 does not issue a warning in situation 3 shown in FIG. 2( a) by using the results obtained by executing the host vehicle peripheral object position detection and the results obtained by executing the host vehicle path prediction.

[0052] In situation 3, the lean vehicle 1 is traveling straight at a vehicle speed V1 on a road without white lines, and the third leading vehicle 103 is traveling straight ahead of the lean vehicle 1 at the same vehicle speed V1 as the lean vehicle 1. Although the lean vehicle 1 is traveling straight, the center position of the front wheels in the vehicle width direction is in a meandering state, meandering within a range that fits within the vehicle width of the lean vehicle 1, centered on a straight line parallel to the traveling direction of the third leading vehicle 103 that is traveling straight. Furthermore, the lean vehicle 1 is traveling in such a way that the center position of the front wheels in the vehicle width direction is located within the vehicle width of the third leading vehicle 103 when viewed from the traveling direction of the third leading vehicle 103.

[0053] In situation 3, in addition to the third leading vehicle 103, a fourth leading vehicle 104 is also traveling at a vehicle speed V2 that is slower than the vehicle speed V1 of the lean vehicle 1 (V2<V1). The fourth leading vehicle 104 is turning ahead of the predicted path 200. The predicted path 200 shows the path that would be obtained if the FCW device 2 performed a host vehicle path prediction for turning at the same yaw rate as the yaw rate obtained for the lean vehicle 1 that is snaking. In reality, when the lean vehicle 1 is snaking, host vehicle path prediction based on yaw rate is not performed.

[0054] When the lean vehicle 1 is meandering, the control unit 22 determines that the lean vehicle 1 is traveling straight and performs vehicle path prediction. Therefore, the predicted path of the lean vehicle 1 is a strip-shaped area extending in the same direction as the traveling direction of the third leading vehicle 103 traveling straight.

[0055] In situation 3, the control unit 22 executes warning control so as not to issue a warning from the warning unit 21. The fourth leading vehicle 104, which is traveling at a vehicle speed V2 slower than the vehicle speed V1 of the lean vehicle 1, moves relatively toward the lean vehicle 1, but the fourth leading vehicle 104 is located outside the predicted path of the lean vehicle 1, which is considered to be traveling straight. Therefore, the possibility of a collision between the lean vehicle 1 and the fourth leading vehicle 104 is below a predetermined probability of collision that requires a warning, and the control unit 22 controls the warning unit 21 so as not to issue a warning for the fourth leading vehicle 104.

[0056] The third leading vehicle 103 is on the predicted path of the lean vehicle 1, which is considered to be traveling straight, but is traveling at the same vehicle speed V1 as the lean vehicle 1. The distance between the lean vehicle 1 and the third leading vehicle 103 is maintained, and the third leading vehicle 103 is not moving relative to the lean vehicle 1. Therefore, the possibility of a collision between the lean vehicle 1 and the third leading vehicle 103 is also below a predetermined collision possibility that requires an alarm, and the control unit 22 controls the alarm unit 21 not to issue an alarm for the third leading vehicle 103.

[0057] 2B shows a situation in which the fifth leading vehicle 105 is traveling straight at a vehicle speed V2 on the predicted path of the lean vehicle 1, which is traveling straight at a vehicle speed V1. When the vehicle speed V2 of the fifth leading vehicle 105 is slower than the vehicle speed of the lean vehicle 1 (V2<V1), the control unit 22 executes warning control so that the warning unit 21 issues a warning when the possibility of a collision between the lean vehicle 1 and the fifth leading vehicle 105 reaches or exceeds a predetermined collision possibility. When the vehicle speed V2 of the fifth leading vehicle 105 is the same as the vehicle speed of the lean vehicle 1 (V2=V1), the distance between the lean vehicle 1 and the fifth leading vehicle 105 is maintained, and therefore the control unit 22 executes warning control so that the warning unit 21 does not issue a warning.

[0058] In situation 2 shown in Figure 1 and situation 3 shown in Figure 2(a), the control unit 22 determines that the lean vehicle 1 is not turning, and therefore the control unit 22 executes warning control in the same manner as when the lean vehicle 1 is traveling straight without snaking, as shown in Figure 2(b).

[0059] [Third Embodiment] A lean vehicle FCW device 2 according to a third embodiment of the present disclosure will be described with reference to Fig. 3. Below, content that overlaps with the description of the first and second embodiments will be omitted, and only content necessary to describe the FCW device 2 of the third embodiment will be described.

[0060] As shown in FIG. 3A, the FCW device 2 according to the third embodiment further includes a vehicle speed detection unit 25 that detects the vehicle speed of the lean vehicle 1 in addition to the configuration shown in FIG.

[0061] The control unit 22 determines whether the lean vehicle 1 is traveling straight or turning from the yaw rate obtained using the turning state detection unit 24. The control unit 22 determines whether the lean vehicle 1 is traveling straight or turning from the yaw rate obtained using the turning state detection unit 24. The control unit 22 may determine that the lean vehicle 1 is turning if the magnitude of the yaw rate is equal to or greater than a predetermined threshold. If the yaw rate is defined as positive when the lean vehicle 1 is turning to the right with respect to the traveling direction and as negative when the lean vehicle 1 is turning to the left with respect to the traveling direction, the control unit 22 may determine that the lean vehicle 1 is turning if the duration of the sign of the yaw rate is equal to or greater than a predetermined threshold. If it is determined that the lean vehicle 1 is traveling straight, the control unit 22 predicts a course ahead in the traveling direction of the lean vehicle 1.

[0062] As shown in Figure 3 (b), when the control unit 22 determines that the lean vehicle 1 is turning, it performs a vehicle trajectory prediction taking into account the turning of the lean vehicle 1 based on the yaw rate obtained using the turning state detection unit 24 and the vehicle speed detected by the vehicle speed detection unit 25 (S1).

[0063] When the lean vehicle 1 turns, a curved predicted path is obtained ahead of the turning direction of the lean vehicle 1, as shown in situation 1 in Figure 1. When the lean vehicle 1 travels straight, a straight predicted path is obtained ahead of the traveling direction of the lean vehicle 1, as shown in Figure 2(b).

[0064] When the lean vehicle 1 is in a meandering state, the control unit 22 performs a host vehicle path prediction that takes the meandering state into consideration (S2). Specifically, the control unit 22 performs a host vehicle path prediction when it is determined that the lean vehicle 1 is traveling straight. That is, the control unit 22 performs a host vehicle path prediction regardless of the yaw rate value obtained using the turning state detection unit 24. For example, even if a yaw rate having a value similar to that at the start of a turn is obtained, the control unit 22 performs a host vehicle path prediction, regarding the yaw rate value as 0 (zero). As a result, when the lean vehicle 1 traveling straight is in a meandering state, the same predicted path as when the lean vehicle 1 is traveling straight is obtained.

[0065] The control unit 22 executes position detection of objects around the host vehicle based on the captured image obtained by the monocular camera 23 (S3). When the lean vehicle 1 is in a meandering state, the control unit 22 executes warning control based on the predicted path obtained by the host vehicle path prediction (S2) taking the meandering state into account and the positions of objects detected by the position detection of objects around the host vehicle (S3) (S4). On the other hand, when the lean vehicle 1 is neither in a meandering state nor traveling straight, the control unit 22 executes warning control based on the predicted path obtained by the host vehicle path prediction (S1) taking turns into account and the positions of objects detected by the position detection of objects around the host vehicle (S3) (S4).

[0066] [Method for determining meandering state] An example of a process in which the FCW device 2 for a lean vehicle according to the first to third embodiments determines whether the lean vehicle 1 has started turning or has staggered while traveling straight will be described with reference to FIG. 4 .

[0067] 4A is a diagram showing the change over time in the value of the yaw rate obtained from the detection result of the turning state detection unit 24. Fig. 4A shows the change in the yaw rate when the lean vehicle 1 turns to the right relative to the traveling direction and when the lean vehicle 1 turns to the left relative to the traveling direction, the yaw rate is defined as positive and negative, respectively.

[0068] 4(b) shows the code duration, which is the duration during which the yaw rate shown in FIG. 4(a) continues to show the same code. The threshold value Th shown in FIG. 4(b) is a threshold value for determining whether the lean vehicle 1 is traveling straight or turning. If the code duration is shorter than the threshold value Th, the control unit 22 determines that the lean vehicle 1 is traveling straight.

[0069] 4C shows a straight-ahead flag indicating whether the lean vehicle 1 is traveling straight. When the lean vehicle 1 is traveling straight, the value of the straight-ahead flag is "1." When the lean vehicle 1 is turning, the value of the straight-ahead flag is "0."

[0070] If the code duration shown in Fig. 4(b) does not exceed the threshold value Th, the control unit 22 determines that the lean vehicle 1 is traveling straight and sets the straight traveling flag to "1" as shown in Fig. 4(c). If the code duration exceeds the threshold value Th, the control unit 22 determines that the lean vehicle 1 is turning and sets the straight traveling flag to "0".

[0071] If the duration of the yaw rate sign is shorter than a predetermined threshold value Th, the control unit 22 determines that the lean vehicle 1 is traveling straight and performs the host vehicle path prediction without taking the yaw rate into consideration. For example, as described above, the host vehicle path prediction is performed with the yaw rate value set to 0 (zero) regardless of the value of the yaw rate detected from the lean vehicle 1.

[0072] In the example shown in Figure 4, the sign of the yaw rate is positive from time 0 to t1, negative from time t1 to t2, and positive again from time t2 onwards. When the lean vehicle 1 is in a serpentine state, the sign of the yaw rate changes in this manner within a short period of time. The threshold value Th is set to a value greater than the sign duration when the vehicle is in a serpentine state. When the lean vehicle 1 is in a serpentine state, the sign duration does not exceed the threshold value, and the vehicle is therefore considered to be traveling straight.

[0073] When the lean vehicle 1 starts turning, the code duration becomes longer than when the vehicle is in a snaking state. In the example shown in Figure 4, the code duration reaches the threshold value Th at time t3. When the code duration exceeds the threshold value Th, i.e., a predetermined time, the lean vehicle 1 is considered to be turning.

[0074] In this way, even if the lean vehicle 1 starts to sway and meander while traveling straight and the yaw rate value shows a large value that cannot be obtained while traveling straight, the control unit 22 can determine whether the lean vehicle 1 has started to turn or is swaying and meandering while traveling straight, based on whether the time during which the yaw rate continues to show the same sign exceeds the threshold value Th.

[0075] REFERENCE SIGNS LIST 1 lean vehicle 2 FCW device 21 alarm unit 22 control unit 23 monocular camera 24 turning state detection unit 25 vehicle speed detection unit

Claims

1. An FCW device for a lean vehicle comprising: an alarm unit which issues an alarm to a driver; and one or more control units which execute a host vehicle path prediction which predicts a path of the host vehicle and a host vehicle peripheral object position detection which detects the positions of objects around the host vehicle, calculate a possibility of a collision between the host vehicle and the object using the results of the host vehicle path prediction and the results of the host vehicle peripheral object position detection, and execute an alarm control which controls whether or not an alarm is issued by the alarm unit based on the possibility of collision. The FCW device for a lean vehicle is used in a lean vehicle whose body leans to the inside of a turn when turning, further comprising: a monocular camera which is fixed to the host vehicle and which captures images of the surroundings of the host vehicle; and a turning state detection unit which detects a physical quantity related to the yaw rate of the host vehicle, wherein the control unit executes the host vehicle peripheral object position detection based on an image captured by the monocular camera, and executes the host vehicle path prediction which takes into account the yaw rate of the host vehicle obtained from the detection result of the turning state detection unit, and executes the alarm control using the obtained result as described in each of the following situations. Situation 1: When the host vehicle is turning on a road without white lines and a first leading vehicle is turning ahead of the host vehicle at a vehicle speed slower than the vehicle speed of the host vehicle with the same turning radius as the host vehicle, the control unit executes warning control so that the warning unit issues a warning when the possibility of a collision between the host vehicle and the first leading vehicle becomes equal to or greater than a predetermined collision possibility. Situation 2: When the host vehicle is traveling straight ahead on a road without white lines and a second leading vehicle is traveling straight ahead of the host vehicle at a vehicle speed slower than the vehicle speed of the host vehicle, the host vehicle is in a meandering state in which the center position of the front wheels in the vehicle width direction of the host vehicle meanders within a range that falls within the vehicle width of the host vehicle around a straight line parallel to the traveling direction of the second leading vehicle, and the center position of the front wheels in the vehicle width direction of the host vehicle is located within the vehicle width of the second leading vehicle as viewed from the traveling direction of the second leading vehicle, the control unit executes warning control so that the warning unit issues a warning when the possibility of a collision between the host vehicle and the second leading vehicle becomes equal to or greater than a predetermined collision possibility.

2. The FCW device for a lean vehicle according to claim 1, wherein the control unit executes the warning control as described in the following situations: Situation 3: When the host vehicle is traveling straight on a road without white lines, a third leading vehicle is traveling straight ahead of the host vehicle at the same vehicle speed as the host vehicle, the host vehicle is in a serpentine state in which the center position of the front wheels in the vehicle width direction of the host vehicle is centered on a straight line parallel to the traveling direction of the third leading vehicle within the vehicle width of the host vehicle, the center position of the front wheels in the vehicle width direction of the host vehicle is located within the vehicle width of the third leading vehicle as viewed from the traveling direction of the third leading vehicle, and a fourth leading vehicle is turning at a vehicle speed slower than the vehicle speed of the host vehicle along a turning path predicted from a yaw rate generated in the host vehicle traveling straight in the serpentine state, the control unit executes warning control so that a warning is not issued by the warning unit.

3. The FCW device for a lean vehicle as described in claim 1, further comprising a vehicle speed detection unit which detects the vehicle speed of the host vehicle, wherein the control unit determines whether the host vehicle is turning based on a yaw rate obtained from the detection result of the turning state detection unit, and when it is determined that the host vehicle is turning, performs the host vehicle course prediction based on the yaw rate obtained from the detection result of the turning state detection unit and the vehicle speed detected by the vehicle speed detection unit, and when the host vehicle is in the swerving state, performs the host vehicle course prediction by assuming that the host vehicle is traveling straight regardless of the value of the yaw rate.

4. The FCW device for a lean vehicle as described in claim 1, characterized in that, when the yaw rate when the vehicle turns to the right relative to the direction of travel is defined as positive and the yaw rate when the vehicle turns to the left relative to the direction of travel is defined as negative, if the duration for which the sign of the yaw rate obtained from the detection result of the turning state detection unit continues to show the same sign is shorter than a predetermined threshold time, the control unit performs the vehicle path prediction by assuming that the vehicle is traveling straight regardless of the value of the yaw rate.

5. An FCW method for a lean vehicle that is executed by an FCW device used in a lean vehicle whose body leans to the inside of a turn when turning, the FCW method comprising: a warning unit that issues a warning to a driver; and one or more control units that execute a host vehicle path prediction that predicts a path of the host vehicle and a host vehicle peripheral object position detection that detects the positions of objects around the host vehicle, calculate a possibility of a collision between the host vehicle and the object using the results of the host vehicle path prediction and the results of the host vehicle peripheral object position detection, and execute warning control that controls whether or not a warning is issued by the warning unit based on the possibility of collision, the FCW method comprising: a step of capturing an image of the surroundings of the host vehicle with a monocular camera fixed to the host vehicle; a step of acquiring an image captured from the monocular camera and executing position detection of objects around the host vehicle; a step of acquiring a yaw rate of the host vehicle from a detection result of a turning state detection unit that detects a physical quantity related to the yaw rate of the host vehicle; and a step of executing the host vehicle path prediction taking into account the yaw rate obtained from the detection result of the turning state detection unit. and executing the warning control as described in each of the following situations using the result of the host vehicle trajectory prediction and the result of the position detection of the object around the host vehicle: Situation 1: When the host vehicle is turning on a road without white lines and a first leading vehicle is turning ahead of the host vehicle at a vehicle speed slower than the vehicle speed of the host vehicle and with the same turning radius as the host vehicle, the control unit executes the warning control so that a warning is issued by the warning unit when the probability of a collision between the host vehicle and the first leading vehicle reaches or exceeds a predetermined probability of collision. Situation 2: When the host vehicle is traveling straight on a road without white lines, a second leading vehicle is traveling straight in front of the host vehicle at a speed slower than the host vehicle's speed, and the center position of the vehicle width direction of the front wheels of the host vehicle is in a zigzag state, zigzagging within a range that falls within the vehicle width of the host vehicle, centered on a straight line parallel to the direction of travel of the second leading vehicle, and the center position of the vehicle width direction of the front wheels of the host vehicle is located within the vehicle width of the second leading vehicle when viewed from the direction of travel of the second leading vehicle, the control unit executes the warning control so that the warning unit issues a warning when the possibility of a collision between the host vehicle and the second leading vehicle reaches a predetermined collision possibility or greater.

6. The FCW method for a lean vehicle according to claim 5, further comprising the step of executing the warning control as described in the following situations: Situation 3: When the host vehicle is traveling straight on a road without white lines, a third leading vehicle is traveling straight ahead of the host vehicle at the same vehicle speed as the host vehicle, the host vehicle is in a serpentine state in which the center position in the vehicle width direction of the front wheels of the host vehicle is centered on a straight line parallel to the traveling direction of the third leading vehicle within the vehicle width of the host vehicle, the center position in the vehicle width direction of the front wheels of the host vehicle is located within the vehicle width of the third leading vehicle as viewed from the traveling direction of the third leading vehicle, and a fourth leading vehicle is turning at a vehicle speed slower than the vehicle speed of the host vehicle along a turning path predicted from a yaw rate generated in the host vehicle traveling straight in the serpentine state, the control unit executes the warning control so that a warning is not issued by the warning unit.

7. The FCW method for a lean vehicle as described in claim 5, characterized in that it is determined whether or not the vehicle is turning based on a yaw rate obtained from the detection result of the turning state detection unit, and if it is determined that the vehicle is turning, the vehicle path prediction is performed based on the yaw rate obtained from the detection result of the turning state detection unit and the vehicle speed detected by a vehicle speed detection unit that detects the vehicle speed of the vehicle, and if the vehicle is in the swerving state, the vehicle path prediction is performed assuming that the vehicle is traveling straight regardless of the value of the yaw rate.

8. The FCW method for lean vehicles described in claim 5, characterized in that, when the yaw rate when the vehicle turns to the right relative to the direction of travel is defined as positive and the yaw rate when the vehicle turns to the left relative to the direction of travel is defined as negative, if the duration for which the sign of the yaw rate obtained from the detection result of the turning state detection unit continues to show the same sign is shorter than a predetermined threshold time, the vehicle path prediction is performed assuming that the vehicle is traveling straight regardless of the value of the yaw rate.

Images