JP7740086B2 - Periphery monitoring device and program - Google Patents

Description

The present invention relates to a perimeter monitoring device and program.

Known perimeter monitoring devices are those that perform collision prevention operations against moving objects approaching from the side in front of the vehicle. For example, Patent Document 1 describes a perimeter monitoring device that calculates the speed of a moving object based on the optical flow of time-series images of the area in front of the vehicle, calculates a predicted time for the moving object to pass in front of the vehicle, and performs collision prevention operations against the moving object if the predicted time falls below a threshold.

JP 2014-67276 A

For example, it is conceivable that a moving object, such as a bicycle, may stop just before reaching the road on which the vehicle is traveling. However, with existing technology, it is conceivable that a collision between the vehicle and the moving object may be incorrectly determined, resulting in unnecessary activation of collision prevention measures.

The present invention was made in consideration of the above circumstances, and its main purpose is to provide a surroundings monitoring device and program that can prevent unnecessary activation of collision prevention operations.

The present invention provides a surroundings monitoring device that performs a collision prevention operation against a moving object approaching from the side in front of a vehicle,
an image acquisition unit that acquires images of the area ahead in the traveling direction of the host vehicle from an imaging device at a predetermined interval;
a movement amount calculation unit that calculates a movement amount of the moving object recognized in the image in a vehicle width direction of the host vehicle using an optical flow;
a deceleration determination unit that determines whether the moving object on the front side of the host vehicle has decelerated in the vehicle width direction based on a rate of change in the movement amount calculated by the movement amount calculation unit;
a limiting unit that limits the execution of the collision prevention operation based on a determination result of the deceleration determining unit;
Equipped with.

If a moving object approaching from the side in front of the host vehicle decelerates in the width direction of the host vehicle before reaching the road on which the host vehicle is traveling, the possibility of a collision between the host vehicle and the moving object is considered low. Here, object detection using optical flow can detect that the moving object is decelerating in the width direction of the host vehicle by detecting a gradual decrease in the amount of movement of the moving object in the width direction of the host vehicle.

Therefore, in this invention, it is determined that a moving object approaching from the side in front of the host vehicle has decelerated in the vehicle width direction based on the rate of change of the amount of movement of the host vehicle in the vehicle width direction. As a result, if it is determined that the host vehicle and the moving object will not collide, the implementation of collision prevention operation is restricted. This makes it possible to prevent unnecessary activation of collision prevention operation.

Configuration diagram of a perimeter monitoring system. FIG. 2 is a diagram showing an image captured ahead of the vehicle in the traveling direction. 4 is a flowchart showing a processing procedure for deceleration determination control. 4 is a flowchart showing a procedure for collision prevention control. 4 is a time chart showing an example of control by the ECU. FIG. 10 is a diagram showing an image captured ahead in the traveling direction of the host vehicle according to another embodiment. 4 is a flowchart showing a processing procedure for deceleration determination control.

Hereinafter, a specific embodiment of a perimeter monitoring device according to the present invention will be described with reference to the drawings. The perimeter monitoring system 10 according to this embodiment is mounted on a vehicle and monitors the area ahead of the vehicle.

As shown in FIG. 1, the perimeter monitoring system 10 according to this embodiment includes a radar device 21, an imaging device 22, a vehicle speed sensor 23, a steering angle sensor 24, a yaw rate sensor 25, a receiving device 26, an ECU 30, and a controlled device 41. In this embodiment, the ECU 30 corresponds to the perimeter monitoring device.

The radar device 21 is, for example, a well-known millimeter-wave radar that transmits high-frequency signals in the millimeter wave band. The radar device 21 is mounted, for example, at the front of the vehicle with its optical axis facing forward. It defines an area within a predetermined detection angle as its detection range, within which objects can be detected, and detects the position of objects within the detection range. Specifically, the radar device 21 transmits search waves at a predetermined interval and receives reflected waves using multiple antennas. The radar device 21 calculates the distance to the object based on the transmission time of the search waves and the reception time of the reflected waves. The radar device 21 also calculates the relative speed based on the frequency of the waves reflected by the object, which has changed due to the Doppler effect. Additionally, the radar device 21 calculates the direction of the object based on the phase difference between the reflected waves received by the multiple antennas. The radar device 21 outputs detection data such as the distance to the object, relative speed, and direction of the object to the ECU 30.

The imaging device 22 is a single monocular camera installed on the vehicle. The imaging device 22 is, for example, a CCD camera, a CMOS image sensor, a near-infrared camera, etc. The imaging device 22 is attached, for example, at a predetermined height in the center of the vehicle's width direction, and captures an image of an area extending in a predetermined angular range forward of the vehicle from a bird's-eye view. The imaging device 22 sequentially outputs the captured images to the ECU 30. Note that the imaging device 22 may also be a stereo camera installed on the vehicle.

The vehicle speed sensor 23 is a sensor that detects the traveling speed of the host vehicle and outputs a traveling speed signal corresponding to the traveling speed of the host vehicle to the ECU 30. The steering angle sensor 24 is a sensor that detects the steering angle of the steering wheel and outputs a steering angle signal corresponding to changes in the steering angle to the ECU 30. The yaw rate sensor 25 is a sensor that detects the turning angular velocity of the host vehicle and outputs a yaw rate signal corresponding to the turning angular velocity of the host vehicle to the ECU 30.

The receiver 26 is a receiver for positioning signals from a satellite positioning system, such as a GPS receiver. The receiver 26 receives positioning signals corresponding to the current position of the vehicle and outputs the received positioning signals to the ECU 30.

The functions provided by ECU 30 can be provided by software recorded in a physical memory device and a computer that executes the software, by software alone, by hardware alone, or a combination of these. For example, if ECU 30 is provided by hardware electronic circuits, it can be provided by digital circuits including numerous logic circuits, or by analog circuits. For example, ECU 30 executes programs stored on a non-transitory tangible storage medium that serves as its own storage unit. The programs include programs for the various arithmetic processes described below. Execution of the programs results in the execution of the methods corresponding to the programs. The storage unit is, for example, non-volatile memory. Note that programs stored in the storage unit can be updated, for example, via a network such as the Internet.

The ECU 30 is configured to perform collision prevention operations against moving objects located to the sides in front of the vehicle. Specifically, the ECU 30 includes a position information acquisition unit 31, a smoothing processing unit 32, a TTC calculation unit 33, and a control unit 34. Note that moving objects include vehicles such as four-wheeled automobiles, motorcycles, and bicycles, as well as pedestrians.

The position information acquisition unit 31 acquires relative position information of a moving object relative to the host vehicle. The relative position information of a moving object is the relative distance and speed of the moving object relative to the host vehicle. The position information acquisition unit 31 may acquire the relative position information based on, for example, images captured by the imaging device 22, or based on detection information from the radar device 21.

The smoothing processing unit 32 performs smoothing processing to suppress changes in the relative position information. The smoothing processing is intended to suppress malfunctions of collision prevention operations due to noise, etc. For example, the smoothing processing unit 32 suppresses noise in the relative position information by applying Kalman filter processing to the images captured by the imaging device 22 or low-pass filter processing to the detection information from the radar device 21.

The TTC calculation unit 33 calculates the collision prediction time. The collision prediction time is an evaluation value that indicates how many seconds it will take for the vehicle to collide with an object if traveling at its current vehicle speed. The shorter the collision prediction time, the higher the risk of collision, and the longer the collision prediction time, the lower the risk of collision. In this embodiment, the TTC (Time to Collision) is calculated as the collision prediction time. The TTC is, for example, a value obtained by dividing the relative distance of a moving object to the vehicle by the relative speed of the moving object to the vehicle.

The control unit 34 performs collision prevention operation based on the TTC. In this embodiment, the conditions for performing collision prevention operation are met when the TTC for the moving object falls below a predetermined collision determination threshold Th.

In this embodiment, the perimeter monitoring system 10 includes an alarm device 42, a brake device 43, and a steering device 44 as controlled devices 41. The alarm device 42 is a device that issues an alarm to the driver of the vehicle, and is, for example, a device that issues an audible alert such as a speaker or buzzer installed in the vehicle cabin, or a device that issues a visual alert such as a display or warning light. For example, the alarm device 42 issues an alert to the driver of the vehicle by emitting an alarm sound or by turning on an indicator installed on the door mirror or instrument panel.

The brake device 43 is a device that brakes the host vehicle by operating a hydraulic actuator or the like. The steering device 44 is a device that steers the host vehicle by operating a steering motor or the like. In this embodiment, braking the host vehicle by the brake device 43 corresponds to a contact suppression operation.

However, it is conceivable that a moving object, such as a bicycle, may decelerate just before reaching the road on which the vehicle is traveling. However, with existing technology, a lack of responsiveness to the deceleration of the moving object may result in an erroneous determination that the vehicle and the moving object will collide, and collision prevention operations may be activated unnecessarily.

In this embodiment, the TTC for the moving object is calculated based on the relative position information of the moving object relative to the host vehicle, and collision prevention operation is performed based on that TTC. In this case, to prevent malfunction of the collision prevention operation due to noise, etc., it is desirable to suppress changes in the relative position information through smoothing processing. However, in this case, if a moving object approaching from a lateral position in front of the host vehicle suddenly decelerates, there is a concern that the response to that sudden deceleration will be delayed, resulting in unnecessary collision prevention operation being performed.

In this embodiment, the ECU 30 is equipped with a configuration for preventing unnecessary collision prevention operations from being performed. Specifically, the ECU 30 is equipped with an image acquisition unit 35, a movement amount calculation unit 36, a deceleration determination unit 37, and a restriction unit 38. The image acquisition unit 35 acquires images of the area ahead of the vehicle in the direction of travel from the imaging device 22 at a predetermined interval. The images acquired from the imaging device 22 are formed using pixels according to the resolution of the imaging device 22.

The movement amount calculation unit 36 calculates the amount of movement of a moving object recognized in an image in the vehicle width direction using optical flow processing.

In optical flow processing, moving objects are recognized from the changes between the previously captured image and the currently captured image. More specifically, feature points are extracted from the previously captured image, and similar feature points are extracted from the currently captured image. Motion vectors are then calculated by searching for feature points in the currently captured image that match those in the previously captured image. Motion vectors indicate the direction and magnitude of change at each feature point over time, and are calculated based on each image that comes before and after in the time series. A rectangular area surrounding the moving object is extracted based on the motion vector calculated for each feature point.

Figure 2 shows an example of optical flow processing. Image G is an image captured of the area ahead of the vehicle as it travels on road 51, which is a straight road, and shows a bicycle 50 as a moving object at a position to the side of the vehicle. Here, we imagine a scene in which bicycle 50 is moving on the left side of road 51, crossing road 51 from left to right, and coming to a stop on sidewalk 52 to the left of road 51.

For convenience, Figure 2 shows bicycle 50a detected in the current image G, and bicycle 50b detected in an image chronologically earlier than image G, shown on image G. Furthermore, because the vehicle and bicycle 50 are moving toward each other, bicycle 50b, which is later in the chronological order, is shown schematically and enlarged compared to bicycle 50a, which is earlier in the chronological order.

Optical flow processing calculates motion vectors for the pixels that make up the bicycle 50, and a rectangular region R surrounding the bicycle 50 is extracted based on the calculated motion vectors. In the vehicle width direction, the number of pixels corresponding to the width of the rectangular region Ra surrounding the bicycle 50a detected in the current image G is Wa, and the number of pixels corresponding to the width of the rectangular region Rb surrounding the bicycle 50b detected in the previous image in the chronological order is Wb (<Wa).

The movement amount calculation unit 36 calculates the amount of movement of a moving object in the width direction of the vehicle by comparing images that have undergone optical flow processing and that are previous and next in time series. In this embodiment, if the number of pixels corresponding to the movement distance of the rectangular areas Ra and Rb that are previous and next in time series in the width direction of the vehicle in Figure 2 is L, then L/Wa is the amount of movement of the bicycle 50a in the width direction of the vehicle. Note that in this embodiment, the direction of the motion vector for the bicycle 50 is considered positive when it is pointing right on image G.

The deceleration determination unit 37 determines that the moving object has decelerated at a lateral position in front of the vehicle based on the rate of change in the amount of movement calculated by the movement amount calculation unit 36. Here, the rate of change in the amount of movement is the rate of change in the amount of movement per unit time in the width direction of the vehicle. In this embodiment, the deceleration determination unit 37 determines whether the bicycle 50 will stop in front of the vehicle before reaching the road 51 on which the vehicle is traveling, based on the rate of change in the amount of movement calculated by the movement amount calculation unit 36.

When the motion vector for the bicycle 50 points to the right on the image, the deceleration determination unit 37 calculates the rate at which the movement amount decreases per unit time as the rate of change in the movement amount. Furthermore, when the motion vector for the bicycle 50 points to the left on the image, the deceleration determination unit 37 calculates the rate at which the movement amount increases per unit time as the rate of change in the movement amount. When the rate of change in the movement amount is equal to or greater than the rate of change threshold, the deceleration determination unit 37 determines that the bicycle 50 will stop before reaching the road 51, and when the rate of change in the movement amount is less than the rate of change threshold, it determines that there is a possibility that the bicycle 50 will enter the road 51.

The restriction unit 38 restricts the implementation of collision prevention operations based on the determination result of the deceleration determination unit 37. In this embodiment, when restricting the implementation of collision prevention operations for the bicycle 50 based on the determination result of the deceleration determination unit 37, the restriction unit 38 restricts the implementation of collision prevention operations by not operating the brake device 43 to brake the vehicle even if the TTC for the bicycle 50 falls below the collision determination threshold Th.

Next, the deceleration determination control and collision prevention control performed by the ECU 30 will be explained using Figures 3 and 4. The deceleration determination control and collision prevention control are performed in parallel, and the implementation of collision prevention operations in the collision prevention control is limited depending on the processing results of the deceleration determination control.

Figure 3 is a flowchart showing the processing procedure for deceleration determination control. This processing is performed at a predetermined control cycle.

In step S10, an image of the area ahead of the vehicle is acquired from the imaging device 22. In step S11, optical flow processing is performed on the acquired image. This calculates motion vectors for moving objects present in the image and extracts rectangular areas surrounding the moving objects.

In step S12, a determination is made as to whether optical flow processing is valid. For example, the conditions for determining whether optical flow processing is valid include the following: the host vehicle is not stopped; the host vehicle's yaw rate is within a specified range; the host vehicle's acceleration is within a specified range; more than a specified number of feature points for moving objects are extracted; and the height of rectangular region R is equal to or greater than a specified position. The determination of whether optical flow processing is valid may be made based on information obtained from the vehicle speed sensor 23, steering angle sensor 24, yaw rate sensor 25, and receiving device 26. If all of these conditions are met, optical flow processing is determined to be valid; if at least one of these conditions is not met, optical flow processing is determined to be invalid. Note that the conditions for determining whether optical flow processing is valid do not have to include all of the above-mentioned conditions, and may omit at least one of the above-mentioned conditions.

If it is determined in step S12 that optical flow processing is enabled, proceed to step S13; if it is determined that optical flow processing is not enabled, proceed to step S16.

In step S13, the amount of movement X of the moving object in the vehicle width direction of the host vehicle is calculated. In this embodiment, the amount of movement X of the moving object in the vehicle width direction of the host vehicle is calculated by dividing the number of pixels corresponding to the movement distance of the rectangular area before and after the time series by the number of pixels corresponding to the width of the rectangular area after the time series. The calculated amount of movement X is stored as history information in a memory unit such as RAM of the ECU 30. Here, the history information is information consisting of a pair of the average value of the amount of movement X in the current control cycle and the amount of movement X in the previous control cycle, and the time when the amount of movement X was calculated. Note that the history information may also store information consisting of a pair of the amount of movement X and the time when the amount of movement X was calculated. Furthermore, if a negative determination is made in the processing of step S12, the history information stored in the memory unit may be deleted.

In step S14, the rate of change ΔX in the movement amount X of the moving object is calculated. For example, an approximate line is obtained by applying the least squares method to the historical information in which the movement amount X was calculated most recently. The rate of change ΔX in the movement amount X of the moving object is calculated as the absolute value of the slope of the approximate line.

Note that if the amount of data in the history information is insufficient to use the least squares method, it is not necessary to calculate the rate of change ΔX in the movement amount X of the moving object. In this case, the process may proceed to step S16 without performing the next step S15.

In step S15, it is determined whether the moving object will stop at a lateral position in front of the vehicle. In this embodiment, if it is determined that the following first to third conditions are met, it is determined that the moving object will stop at a lateral position in front of the vehicle.

The first condition is that the rate of change ΔX in the amount of movement X of the moving object is equal to or greater than the rate of change threshold ΔXth. It is desirable to determine that the moving object will stop before the conditions for implementing the collision prevention operation (TTC implementation conditions) are met. In this regard, it is believed that the time from when the moving object begins to decelerate until the conditions for implementing the collision prevention operation are met becomes shorter the larger the TTC collision determination threshold Th. Therefore, for example, when the collision determination threshold Th is set high, it is preferable to set the rate of change threshold ΔXth higher than when the collision determination threshold Th is set low.

The second condition is that the amount of movement X of the moving object is within a specified range. Here, the lower limit of the specified range should be set to a value near 0, which makes it possible to determine that the moving object is moving, and the upper limit of the specified range should be set according to the speed expected from the type of moving object. Note that the type of moving object should be determined based on images acquired from the imaging device 22.

The third condition is that the magnification ratio k of the rectangular region R is equal to or greater than the magnification ratio threshold kth. Here, the value of the magnification ratio k of the rectangular region R is Wa/Wb in Figure 2 above. If the value of the magnification ratio k, Wa/Wb, is greater than 1, the moving object is recognized as approaching the host vehicle. On the other hand, if the value of the magnification ratio k, Wa/Wb, is less than 1, the moving object is recognized as moving away from the host vehicle. The magnification ratio threshold kth may be any value greater than 1.

If the determination in step S15 is negative, the process proceeds to step S16. On the other hand, if the determination in step S15 is positive, the process proceeds to step S17. In step S16, flag F is set to off, and in step S17, flag F is set to on. When flag F is on, it indicates that the deceleration determination control has determined that a moving object will stop before reaching the vehicle's travel path, and when flag F is off, it indicates that the deceleration determination control has determined that a moving object will enter the vehicle's travel path.

Figure 4 is a flowchart showing the processing procedure for collision prevention control. This processing is performed at a predetermined control cycle.

In step S20, relative position information of the moving object relative to the host vehicle is acquired. In this embodiment, the relative position information is acquired based on the image captured by the imaging device 22, and includes the lateral distance, which is the relative distance of the moving object in the vehicle width direction of the host vehicle, and the lateral speed, which is the relative speed of the moving object in the vehicle width direction of the host vehicle. It is also possible to acquire the longitudinal distance, which is the relative distance of the moving object in the vehicle length direction of the host vehicle, and the longitudinal speed, which is the relative speed of the moving object in the vehicle width direction of the host vehicle, based on the image captured by the imaging device 22, as relative information.

In step S21, a smoothing process is performed to suppress changes in lateral distance and lateral speed. In step S22, the TTC is calculated based on the smoothed lateral distance and lateral speed. Note that the TTC calculation may also take into account longitudinal distance and longitudinal speed.

In step S23, it is determined whether the TTC has fallen below the collision determination threshold Th. If the determination in step S23 is negative, the process ends. On the other hand, if the determination in step S23 is positive, the process proceeds to step S24.

In step S24, it is determined whether flag F is on. If the determination in step S24 is negative, the process proceeds to step S25, where collision prevention operation is performed. On the other hand, if the determination in step S24 is positive, the process ends. As a result, if it is determined that a moving object ahead of the host vehicle will stop before reaching the host vehicle's driving path area, the implementation of the determined collision prevention operation is restricted.

Figure 5 shows an example of control by the ECU 30 in a situation similar to that shown in Figure 2. In Figure 5, (a) shows the change in the lateral speed of the bicycle 50, (b) shows the change in the TTC for the bicycle 50, (c) shows the change in the movement amount X of the bicycle 50, and (d) shows the flag F. In Figure 5(a), the change in the lateral speed of the bicycle 50 when Kalman filter processing is applied is shown by a solid line, and the actual lateral speed of the bicycle 50 is shown by a dashed line. Note that the host vehicle is traveling at a constant speed on the road 51 while approaching the bicycle 50, and the magnification rate k of the bicycle 50 is greater than the magnification rate threshold kth.

Time t1 is the timing when the bicycle 50 begins to decelerate in order to stop on the sidewalk 52. Time t2 is the timing when the deceleration determination control determines that the bicycle 50 will stop on the sidewalk 52 in front of the vehicle, and flag F switches from OFF to ON. Time t3 is the timing when the TTC for the bicycle 50 falls below the collision determination threshold Th in the collision prevention control. Up until time t1, the value of the movement amount X of the bicycle 50 is constant at X1. After time t1, the value of the movement amount X of the bicycle 50 gradually decreases. At time t2, the value of the movement amount X of the bicycle 50 decreases to X2, which is smaller than X1. The slope of the decrease in the movement amount X of the bicycle 50 from time t1 to time t2 is assumed to be greater than the change rate threshold ΔXth.

The lateral speed of the bicycle 50 begins to decrease at time t1 and eventually reaches zero. In other words, in reality, the bicycle 50 stops on the sidewalk 52 in front of the host vehicle, and the host vehicle and the bicycle 50 do not collide. However, after time t1, the lateral speed of the bicycle 50 when Kalman filter processing is applied becomes higher than the actual lateral speed of the bicycle 50 due to the suppression of changes in lateral speed, and the TTC for the bicycle 50 continues to gradually decrease. As a result, at time t3, the TTC for the bicycle 50 falls below the collision determination threshold Th. In this case, there is a concern that unnecessary collision prevention operations may be performed.

Meanwhile, from time t1 onwards, the rate of change ΔX of movement amount X of bicycle 50 gradually increases as historical information is accumulated in the memory unit and calculations such as the least squares method progress. Therefore, at time t2, the rate of change ΔX of movement amount X calculated based on the historical information becomes equal to or greater than the change rate threshold ΔXth. This determines that conditions 1 to 3 are met, and flag F is switched from off to on. Therefore, at time t3, the TTC for bicycle 50 falls below collision determination threshold Th, but because flag F is on, implementation of collision prevention operation is restricted.

The present embodiment described above provides the following advantages:

If a moving object stops to the side in front of the host vehicle before reaching the road on which the host vehicle is traveling, the possibility of a collision between the host vehicle and the moving object is considered low. Here, when using optical flow object detection, a moving object stopping to the side in front of the host vehicle can be detected by checking that the amount of movement X of the moving object in the width direction of the host vehicle gradually decreases.

In this embodiment, a determination is made that a moving object will stop at a lateral position in front of the host vehicle based on the rate of change ΔX of the moving object's amount of movement X in the vehicle width direction of the host vehicle. As a result, if it is determined that the host vehicle and the moving object will not collide, the implementation of collision prevention operations is restricted. This makes it possible to prevent unnecessary activation of collision prevention operations.

In addition to situations where a moving object stops at a lateral position in front of the host vehicle, it is also possible that the speed of the moving object in the vehicle's width direction may decrease when a moving object approaching from the side in front of the host vehicle changes direction in the fore-aft direction of the host vehicle before entering the vehicle's driving path area. In this embodiment, even in the above-mentioned situations, it is possible to determine that the host vehicle and the moving object will not collide based on the rate of change ΔX of the moving amount X of the moving object in the vehicle's width direction.

It is conceivable that the TTC for a moving object can be calculated based on the relative position information of the moving object relative to the vehicle, and collision prevention action can be taken based on that TTC. In this case, to prevent malfunctions due to noise, etc., it is desirable to suppress changes in the relative position information through smoothing processing. However, in this case, if a moving object approaching from the side in front of the vehicle suddenly decelerates, there is a concern that the response to that sudden deceleration will be delayed, resulting in unnecessary collision prevention action being taken.

In this regard, in parallel with the control of collision prevention operations based on the smoothed relative position information, deceleration judgment is performed based on the rate of change ΔX of the movement amount X calculated using optical flow. This ensures the reliability of the implementation of collision prevention operations while effectively preventing the implementation of unnecessary collision prevention operations against moving objects approaching the vehicle.

<Other Embodiments>
The above embodiment may be modified as follows, for example.

- The following configuration may be adopted, taking into consideration that a moving object approaching from the side in front of the vehicle will change direction toward a sidewalk or other object extending parallel to the road before entering the road on which the vehicle is traveling. Here, optical flow processing may be used to calculate the amount of movement X of the moving object in the vehicle width direction (vehicle width movement amount) as well as the amount of movement Y of the moving object in the vehicle's fore-and-aft direction (front-and-aft movement amount), and a deceleration determination for the moving object may be made based on the rate of change of these amounts of movement X and Y.

In other words, in the scene shown in Figure 6, bicycle 50, approaching from the side in front of the vehicle, changes direction to follow road 51 before entering road 51. In this case, it is not necessary to perform a collision prevention operation on bicycle 50. Therefore, based on the rate of change of movement amounts X and Y, ECU 30 determines that bicycle 50 has entered the vehicle's travel path area, and restricts the implementation of a collision prevention operation based on the result of this stop determination.

The ECU 30 performs the processing shown in Figure 7 instead of Figure 3. Note that in Figure 7, the same step numbers are used for processing that overlaps with Figure 3.

In Figure 7, optical flow processing is performed on the image, and after determining that the optical flow processing is valid, the process proceeds to step S31. In step S31, the amount of movement X of the moving object in the vehicle width direction and the amount of movement Y of the moving object in the front-to-rear direction of the vehicle are calculated. In step S32, the rates of change ΔX and ΔY in the amounts of movement X and Y of the moving object are calculated. In step S33, it is determined whether the moving object will stop at a lateral position in front of the vehicle based on whether the first to third conditions described above are met. Note that here, the first condition is whether the rate of change ΔX of the amount of movement X is greater than or equal to a first threshold value Th1.

If the determination in step S33 is affirmative, the process proceeds to step S17, where flag F is set to ON. According to step S33, it is determined that a moving object on the front side of the host vehicle has decelerated in the vehicle width direction based on the fact that the rate of change ΔX of the movement amount X is equal to or greater than the first threshold value Th1 (first determination unit).

Furthermore, if step S33 is judged negative because at least the rate of change ΔX of the movement amount X is less than the first threshold value Th1 (the first condition is not satisfied), the process proceeds to step S34. In step S34, it is determined whether the rate of change ΔX of the movement amount X is equal to or greater than a second threshold value Th2, which is smaller than the first threshold value Th1, and whether the rate of change ΔY of the movement amount Y is equal to or greater than a third threshold value Th3. In this case, if ΔX < Th1, it is determined that the deceleration of the moving object in the vehicle width direction is not particularly large and that the moving object will not stop at a lateral position in front of the vehicle. However, if ΔX ≧ Th2 and ΔY ≧ Th3, it is determined that the moving object is changing direction before entering road 51. Therefore, if step S34 is judged positive, the process proceeds to step S17, where flag F is set to ON. According to step S34, if the rate of change ΔX of the movement amount X is between the first threshold value Th1 and the second threshold value Th2, and the rate of change ΔY of the movement amount Y is equal to or greater than the third threshold value Th3, it is determined that a moving object on the side in front of the vehicle has decelerated in the vehicle width direction (second determination unit).

Also, if the result of step S34 is negative, the process proceeds to step S16, where flag F is set to off.

The above configuration can appropriately prevent unnecessary collision prevention operations from being performed not only when a moving object stops just before entering the vehicle's driving path area (when it stops just before entering the vehicle's driving path area), but also when a moving object changes direction before entering the vehicle's driving path area.

- In the above embodiment, when the implementation of the collision prevention operation is restricted, the brake device 43 is not activated to brake the host vehicle, but this may be modified. For example, the implementation of the collision prevention operation may be restricted by weakening the braking force of the host vehicle by the brake device 43 compared to when the implementation of the collision prevention operation is not restricted.

- In the above embodiment, the collision prevention operation performed against a moving object located to the side in front of the vehicle is configured to brake the vehicle using the brake device 43, but this may be modified. For example, the collision prevention operation may be configured to either issue a warning using the alarm device 42 or steer the vehicle using the steering device 44.

- The vehicle control device and method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor and memory programmed to execute one or more functions embodied in a computer program. Alternatively, the vehicle control device and method described in the present disclosure may be realized by a special-purpose computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the vehicle control device and method described in the present disclosure may be realized by one or more special-purpose computers configured by combining a processor and memory programmed to execute one or more functions with a processor configured with one or more hardware logic circuits. Furthermore, the computer program may be stored on a computer-readable non-transitory tangible recording medium as instructions executed by a computer.

22: Imaging device, 30: ECU, 35: Image acquisition unit, 36: Movement amount calculation unit, 37: Deceleration determination unit, 38: Restriction unit, 50: Moving object.

Claims (4)

A surroundings monitoring device (30) that performs a collision prevention operation against a moving object (50) approaching from the side in front of a vehicle,
an image acquisition unit (35) that acquires images of a scene ahead in the traveling direction of the vehicle from an imaging device (22) at predetermined intervals;
a movement amount calculation unit (36) that calculates a movement amount of the moving object recognized in the image in a vehicle width direction of the host vehicle by optical flow processing;
a deceleration determination unit (37) that determines whether the moving object on the front side of the host vehicle has decelerated in the vehicle width direction based on a rate of change in the amount of movement calculated by the amount of movement calculation unit;
a limiting unit (38) that limits the execution of the collision prevention operation based on a determination result of the deceleration determination unit;
Equipped with
the movement amount calculation unit calculates, for the moving object recognized in the image, a vehicle width direction movement amount that is a movement amount of the moving object in a vehicle width direction of the host vehicle and a front-rear direction movement amount that is a movement amount of the moving object in a front-rear direction of the host vehicle by optical flow processing;
The deceleration determination unit
a first determination unit that determines that the moving object has decelerated in the vehicle width direction on a side in front of the host vehicle when the change in the vehicle width direction movement amount is a decreasing change and the rate of change in the decreasing side of the vehicle width direction movement amount is equal to or greater than a first threshold value;
a second determination unit that determines that the moving object has decelerated in the vehicle width direction on a front side of the host vehicle when the change in the vehicle width direction movement amount is a decrease, and the decrease rate of the vehicle width direction movement amount is less than the first threshold value and is equal to or greater than a second threshold value that is smaller than the first threshold value, and when the change in the front-rear direction movement amount is an increase, and the increase rate of the front-rear direction movement amount is equal to or greater than a third threshold value,
The restriction unit restricts the execution of the collision prevention operation when a deceleration determination is made by either the first determination unit or the second determination unit . the deceleration determination unit determines, as a deceleration determination of the moving object, whether the moving object will stop ahead of the host vehicle before reaching a driving path area of the host vehicle, based on a rate of change on a decreasing side of the vehicle width direction movement amount calculated by the movement amount calculation unit;
The surroundings monitoring device according to claim 1 , wherein the limiting unit limits the execution of the collision prevention operation based on a result of the deceleration determining unit's determination that the moving object has stopped. a position information acquisition unit (31) that acquires relative position information of the moving object with respect to the host vehicle;
a smoothing processing unit (32) that performs smoothing processing to suppress changes in the relative position information;
a collision prediction time calculation unit (33) that calculates a collision prediction time, which is a time required for the host vehicle to collide with the moving object, based on the relative position information after the smoothing process;
a control unit (34) that performs the collision prevention operation based on the collision prediction time,
The surroundings monitoring device according to claim 1 or 2, wherein the limiting unit limits the collision prevention operation based on a determination result of the deceleration determining unit in parallel with the control of the collision prevention operation by the control unit. A program executed by a control device (30) to perform a collision prevention operation against a moving object (50) approaching from the side in front of a vehicle,
an image acquisition step of acquiring images of a front area in a traveling direction of the vehicle from an imaging device (22) at a predetermined interval;
a movement amount calculation step of calculating a movement amount of the moving object recognized in the image in a vehicle width direction of the host vehicle by optical flow processing;
a deceleration determination step of determining whether the moving object on the front side of the host vehicle has decelerated in the vehicle width direction based on a rate of change of the movement amount calculated in the movement amount calculation step;
a limiting step of limiting the execution of the collision prevention operation based on a determination result of the deceleration determining step;
Including,
In the movement amount calculation step, a vehicle width direction movement amount, which is a movement amount of the moving object in a vehicle width direction of the host vehicle, and a front-rear direction movement amount, which is a movement amount of the moving object in a front-rear direction of the host vehicle, are calculated by optical flow processing for the moving object recognized in the image;
The deceleration determination step
a first determination step of determining that the moving object has decelerated in the vehicle width direction on a side in front of the host vehicle when the change in the vehicle width direction movement amount is a decreasing change and the rate of decrease in the vehicle width direction movement amount is equal to or greater than a first threshold value;
a second determination step of determining that the moving object has decelerated in the vehicle width direction on a side in front of the host vehicle when the change in the vehicle width direction movement amount is a decrease, and the decrease rate of the vehicle width direction movement amount is less than the first threshold value and is equal to or greater than a second threshold value that is smaller than the first threshold value, and when the change in the front-rear direction movement amount is an increase, and the increase rate of the front-rear direction movement amount is equal to or greater than a third threshold value,
The program further comprising: a program for restricting execution of the collision prevention operation when a deceleration determination is made in either the first determination step or the second determination step in the restriction step .