Vehicle driving assistance device

Abstract

When a stop element for automatically stopping a traveling host vehicle M by adaptive cruise control is included in travel environment information, a travel_ECU 14 sets a target stop position on the basis of the stop element and, when the host vehicle M is traveling along a downward gradient and a gradient change section, where the downward gradient changes to a more gentle gradient, exists within a set distance from the target stop position, corrects the target stop position rearward and performs stop control for stopping the host vehicle M at the target stop position.

Description

Vehicle driving assistance device

[0001] The present invention relates to a driving assistance device for a vehicle that has a function of automatically stopping the vehicle.

[0002] In recent years, driving assistance devices for assisting drivers in driving operations have been put into practical use in vehicles such as automobiles. The driving assistance devices reduce the burden of driving operations on the driver and improve safety. Driving assistance control by the driving assistance devices is basically realized by combining adaptive cruise control (ACC) and active lane keep centering control (ALKC), etc.

[0003] ACC is a control system that uses a forward recognition device installed in a vehicle to recognize the distance to the preceding vehicle and follow the preceding vehicle. With this ACC, when the preceding vehicle stops, it is possible to stop the host vehicle with a predetermined distance between the vehicles. Furthermore, with ACC, when the preceding vehicle starts moving again, it is also possible to restart the host vehicle following the preceding vehicle.

[0004] For example, Japanese Patent Application Publication No. 2010-163058 discloses a technology for using ACC to stop a vehicle when a preceding vehicle stops. In such a vehicle stop control, the control means disclosed in Japanese Patent Application Publication No. 2010-163058 determines the necessary inter-vehicle distance based on the gradient of the road surface on which the vehicle is traveling, road conditions, etc. As a result, the technology disclosed in Japanese Patent Application Publication No. 2010-163058 prevents contact between vehicles and ensures safety even when the vehicle or another vehicle slips on a sloped road, etc.

[0005] In stop control using ACC, it is desirable to optimize the stopping position of the vehicle to ensure safety as described above as well as to further improve convenience. For example, in stop control using ACC, it is desirable to reduce the running load when the vehicle restarts by optimizing the stopping position of the vehicle and to suppress the output from the power unit when the vehicle starts to run.

[0006] An object of the present invention is to provide a driving assistance device for a vehicle that can ensure safety using adaptive vehicle-following distance control and suppress output when starting to drive.

[0007] A vehicle driving assistance device according to one aspect of the present invention comprises a driving environment recognition means for acquiring driving environment information of the host vehicle, a target stop position setting means for setting a target stop position based on a stopping element when the driving environment information includes a stopping element for automatically stopping the host vehicle while in motion by adaptive cruise control, a target stop position correction means for correcting the target stop position backward when the host vehicle is traveling on a downhill slope and a gradient change section where the downhill slope changes to a gentler gradient is present within a set distance from the target stop position, and a stop control means for stopping the host vehicle at the target stop position.

[0008] Another aspect of the present invention provides a vehicle driving assistance device that includes a driving environment recognition module that acquires driving environment information for the vehicle, and a processor. When the driving environment information includes a stopping element for automatically stopping the vehicle while in motion using adaptive cruise control, the processor sets a target stopping position based on the stopping element. When the vehicle is traveling downhill and a gradient change section where the downhill gradient changes to a gentler gradient is within a set distance from the target stopping position, the processor corrects the target stopping position backward and stops the vehicle at the target stopping position.

[0009] Schematic diagram of a driving support device Flowchart showing a following vehicle distance control routine Flowchart showing a target stop position calculation subroutine Flowchart showing a target stop position correction subroutine Explanatory diagram illustrating an example of an image when the longitudinal gradient of the road surface is approximately uniform Explanatory diagram illustrating an example of an image when the longitudinal gradient of the road surface changes midway Map illustrating the relationship between gradient change amount and correction amount Map illustrating the relationship between the following vehicle distance and an upper limit value Explanatory diagram illustrating the relationship between the target stop position before and after correction Explanatory diagram illustrating the relationship between the target stop position before and after correction Explanatory diagram illustrating the relationship between the target stop position before and after correction

[0010] An embodiment of one aspect of the present invention will be described in detail below with reference to the drawings. Note that in the drawings used in the following description, each component is shown at a different scale so that it can be recognized. Therefore, the present invention is not limited to the number of components, the shapes of the components, the size ratios of the components, and the relative positional relationships of the components shown in these drawings.

[0011] 1, the driving assistance device 1 is mounted on a vehicle (host vehicle) M such as an automobile. Note that the host vehicle M in this embodiment is, for example, a hybrid vehicle that uses both an engine and an electric motor as a drive source.

[0012] The driving assistance device 1 includes a camera unit 10. The camera unit 10 is fixed to the center of the front and upper part of the cabin of the host vehicle M, for example.

[0013] The camera unit 10 includes a stereo camera 11, an image processing unit (IPU) 12, an image recognition unit (image recognition_ECU) 13, and a driving control unit (driving_ECU) 14.

[0014] The stereo camera 11 includes a main camera 11a and a sub-camera 11b. The main camera 11a and the sub-camera 11b each have a color image sensor using, for example, a CMOS. The main camera 11a and the sub-camera 11b are arranged symmetrically across the center of the vehicle width.

[0015] The main camera 11a and the sub-camera 11b capture stereo images of the driving environment outside the vehicle from different viewpoints. The image capturing periods of the main camera 11a and the sub-camera 11b are synchronized with each other.

[0016] The IPU 12 performs predetermined image processing on the driving environment images captured by the stereo camera 11. As a result, the IPU 12 detects the edges of various objects, such as three-dimensional objects and road markings, displayed in the images. The IPU 12 then calculates distance information from the positional deviation of corresponding edges on the left and right images. As a result, the IPU 12 generates image information (distance image information) that includes distance information.

[0017] The image recognition_ECU 13 determines the dividing lines that separate the left and right sides of the lane in which the vehicle M is traveling (the host vehicle driving lane), the width between the left and right dividing lines (lane width), and the road curvature [1 / m] calculated from the curvature of the left and right dividing lines, based on the distance image information received from the IPU 12. The image recognition_ECU 13 also determines the dividing lines that separate the left and right sides of other lanes adjacent to the host vehicle driving lane, the lane width, the road curvature, etc.

[0018] The image recognition ECU 13 also performs predetermined pattern matching on the distance image information, thereby recognizing three-dimensional objects such as guardrails, curbs, median strips, traffic lights, and surrounding vehicles that extend along the road.

[0019] Here, when recognizing a three-dimensional object, the image recognition ECU 13 recognizes, for example, the type of the three-dimensional object, the distance to the three-dimensional object, the speed of the three-dimensional object, and the relative speed between the three-dimensional object and the vehicle M. Furthermore, when the image recognition ECU 13 recognizes that the type of the three-dimensional object is a traffic light, it also recognizes the lighting color of the traffic light.

[0020] The image recognition ECU 13 also recognizes whether or not there is a change in the longitudinal gradient of the road surface in the host vehicle's driving lane. The presence or absence of a change in the longitudinal gradient can be determined, for example, based on the state of the left and right lane markings in the image. The image used for such determination can be, for example, an image captured by the main camera 11a (or the sub-camera 11b). For example, as shown in FIG. 5, if the rate at which the distance between the left and right lane markings decreases is approximately constant in the image, the image recognition ECU 13 determines that the longitudinal gradient is approximately uniform. On the other hand, for example, as shown in FIG. 6, if the rate at which the distance between the left and right lane markings decreases changes midway, the image recognition ECU 13 determines that the longitudinal gradient has changed midway.

[0021] If it is determined that the longitudinal gradient is changing midway, the image recognition ECU 13 recognizes the distance from the host vehicle M to the gradient change section C. The distance from the host vehicle M to the gradient change section C can be recognized, for example, based on a distance image.

[0022] Furthermore, the image recognition ECU 13 recognizes the amount of change in gradient of the road surface at the gradient change section C. For example, the image recognition ECU 13 calculates the amount of gradient change by comparing the rate at which the distance between the left and right lane markings decreases behind the gradient change section C with the rate at which the distance between the left and right lane markings decreases ahead of the gradient change section C.

[0023] The various pieces of information recognized by the image recognition_ECU 13 are output to the traveling_ECU 14 as traveling environment information.

[0024] Thus, in this embodiment, the image recognition ECU 13, together with the stereo camera 11 and the IPU 12, corresponds to a specific example of a driving environment recognition means (and a driving environment recognition module) that recognizes driving environment information outside the vehicle.

[0025] The driving_ECU 14 is a control unit for overall control of the driving assistance device 1 .

[0026] Various control units are connected to the travel_ECU 14 via in-vehicle communication lines such as a Controller Area Network (CAN). For example, a cockpit control unit (CP_ECU) 21, a hybrid control unit (HEV_ECU) 22, a transmission control unit (T / M_ECU) 23, a brake control unit (BK_ECU) 24, and a power steering control unit (PS_ECU) 25 are connected to the travel_ECU 14.

[0027] Furthermore, the travel_ECU 14 is connected with various sensors, such as a locator unit 36, a left front side sensor 37lf, a right front side sensor 37rf, a left rear side sensor 37lr, and a right rear side sensor 37rr.

[0028] The CP_ECU 21 is connected to a human-machine interface (HMI) 30 arranged around the driver's seat. The HMI 30 includes, for example, an operation switch, a mode selector switch, a steering touch sensor, a turn signal switch, a driver monitoring system (DMS), a touch panel display, a combination meter, and a speaker. Here, the operation switch is a switch for setting and executing various driving assistance controls. The mode selector switch is a switch for switching driving assistance modes. The steering touch sensor is a sensor for detecting the driver's steering state. The DMS is a system for performing face authentication, line of sight detection, etc. of the driver.

[0029] When the CP_ECU 21 receives a control signal from the travel_ECU 14, it notifies the driver of various information as appropriate. The various information includes, for example, various warnings for the preceding vehicle P, the implementation status of driving assistance control, and the driving environment of the host vehicle M. The various information is notified, for example, by display or sound using the HMI 30.

[0030] The CP_ECU 21 also outputs various types of input information input by the driver using the HMI 30 to the travel_ECU 14. The various types of input information include, for example, an ON or OFF operation for various driving assistance controls, a set vehicle speed for the host vehicle M, and an operation state of a turn signal switch.

[0031] A throttle actuator 31 of an electronically controlled throttle, an inverter 32, etc. are connected to the output side of the HEV_ECU 22. In addition, various sensors such as an accelerator sensor (not shown) are connected to the input side of the HEV_ECU 22.

[0032] The HEV_ECU 22 controls the throttle actuator 31, the inverter 32, etc. based on control signals from the travel_ECU 14 or detection signals from various sensors. By controlling the throttle actuator 31, etc., the HEV_ECU 22 adjusts the amount of intake air into the engine to generate a desired engine output. Furthermore, by controlling the inverter 32, etc., the HEV_ECU 22 generates a desired motor output. Alternatively, by controlling the inverter 32, etc., the HEV_ECU 22 generates braking force through power regeneration. Furthermore, the HEV_ECU 22 outputs signals, such as the accelerator opening degree detected by various sensors, to the travel_ECU 14.

[0033] The output side of the T / M_ECU 23 is connected to a hydraulic control circuit 33. Furthermore, various sensors, such as a shift position sensor (not shown), are connected to the input side of the T / M_ECU 23. The T / M_ECU 23 performs hydraulic control for the hydraulic control circuit 33 based on the engine torque signal and motor torque signal estimated by the HEV_ECU 22, and detection signals from various sensors. As a result, the T / M_ECU 23 operates friction engagement elements and pulleys provided in the automatic transmission to shift the engine output to a desired gear ratio. The T / M_ECU 23 also operates the friction engagement elements to connect or disconnect the engine drive shaft and the motor drive shaft. The T / M_ECU 23 also outputs signals, such as the shift position detected by the various sensors, to the travel_ECU 14.

[0034] A brake actuator 34 is connected to the output side of the BK_ECU 24. The brake actuator 34 adjusts the brake fluid pressure output to the brake wheel cylinders provided on the respective wheels. In addition, various sensors, such as a brake pedal sensor (not shown), a longitudinal acceleration sensor 41, and wheel speed sensors 42 (left front wheel speed sensor 42fl, right front wheel speed sensor 42fr, left rear wheel speed sensor 42rl, and right rear wheel speed sensor 42rr), are connected to the input side of the BK_ECU 24.

[0035] The BK_ECU 24 performs drive control on the brake actuator 34 based on a control signal from the travel_ECU 14 or detection signals from various sensors. As a result, the BK_ECU 24 appropriately generates braking force on each wheel to perform forced braking control (deceleration control) on the host vehicle M. The BK_ECU 24 also outputs signals to the travel_ECU 14, such as signals indicating the brake operation state, longitudinal acceleration, and vehicle speed (host vehicle speed), which are detected by the various sensors.

[0036] An electric power steering motor 35 is connected to the output side of the PS_ECU 25. The electric power steering motor 35 applies steering torque to the steering mechanism by the rotational force of the motor. In addition, various sensors such as a steering torque sensor and a steering angle sensor are connected to the input side of the PS_ECU 25.

[0037] The PS_ECU 25 controls the drive of the electric power steering motor 35 based on control signals from the travel_ECU 14 or detection signals from various sensors. As a result, the PS_ECU 25 generates a steering torque for the steering mechanism. The PS_ECU 25 also outputs signals indicating the steering torque, steering angle, etc. detected by the various sensors to the travel_ECU 14.

[0038] The locator unit 36 ​​includes a GNSS sensor 36a and a high-precision road map database (road map DB) 36b.

[0039] The GNSS sensor 36a receives positioning signals transmitted from a plurality of positioning satellites, thereby determining the position (latitude, longitude, altitude, etc.) of the host vehicle M.

[0040] The road map DB 36b is a large-capacity storage medium such as an HDD. High-precision road map information (dynamic map) is stored in this road map DB 36b. The road map information includes, for example, lane data required for autonomous driving, such as lane width data, lane center position coordinate data, lane travel azimuth data, speed limit data, and road surface gradient data. The lane data is stored at intervals of several meters for each lane on the road map. The road map DB 36b outputs, for example, road map information for a set range based on the vehicle position measured by the GNSS sensor 36a to the travel_ECU 14 as driving environment information.

[0041] Thus, in this embodiment, the road map DB 36b, together with the GNSS sensor 36a, corresponds to a specific example of a driving environment recognition means (and a driving environment recognition module) that recognizes driving environment information outside the vehicle.

[0042] The left front side sensor 37lf and the right front side sensor 37rf are configured, for example, by millimeter-wave radars. These left front side sensor 37lf and the right front side sensor 37rf are disposed, for example, on the left and right sides of the front bumper, respectively. The left front side sensor 37lf and the right front side sensor 37rf detect, as driving environment information, three-dimensional objects present in areas diagonally forward and to the left and right and to the sides of the vehicle M, which are difficult to recognize in images taken by the stereo camera 11.

[0043] The left rear side sensor 37lr and the right rear side sensor 37rr are configured, for example, by millimeter-wave radar and are disposed, for example, on the left and right sides of the rear bumper, respectively. The left rear side sensor 37lr and the right rear side sensor 37rr detect, as driving environment information, three-dimensional objects present in areas diagonally to the left and right sides and rear of the vehicle M that are difficult to recognize with the left front side sensor 37lf and the right front side sensor 37rf.

[0044] Here, if each radar is configured as a millimeter-wave radar, the millimeter-wave radar analyzes the waves reflected from the object in response to the output radio waves. In this way, the millimeter-wave radar mainly detects three-dimensional objects such as adjacent vehicles and following vehicles. Specifically, each radar detects information about the three-dimensional object, such as the width of the three-dimensional object, the position of a representative point of the three-dimensional object (the position relative to the vehicle M), and the speed.

[0045] Thus, in this embodiment, the left front side sensor 37lf, the right front side sensor 37rf, the left rear side sensor 37lr, and the right rear side sensor 37rr correspond to a specific example of a driving environment recognition means (and a driving environment recognition module) that recognizes driving environment information outside the vehicle.

[0046] The coordinates of each object outside the vehicle included in the traveling environment information recognized by the image recognition_ECU 13, the locator unit 36, the left front side sensor 37lf, the right front side sensor 37rf, the left rear side sensor 37lf, and the right rear side sensor 37rr are converted into coordinates of a three-dimensional coordinate system with the center of the host vehicle M as the origin. Such coordinate conversion is performed by the traveling_ECU 14, for example.

[0047] The driving modes set in the travel_ECU 14 include a manual driving mode, a first driving control mode and a second driving control mode for driving control, and an evacuation mode. These driving modes can be selectively switched by the travel_ECU 14. Such mode switching is performed based on, for example, the operation status of a mode selector switch provided in the HMI 30.

[0048] Here, the manual driving mode is a driving mode that requires the driver to maintain steering, i.e., the manual driving mode is a driving mode in which the host vehicle M is driven according to driving operations such as steering, accelerator, and brake operations by the driver.

[0049] The first driving control mode is also a driving mode that requires the driver to maintain steering. That is, the first driving control mode is a semi-automated driving mode in which the host vehicle M is driven while reflecting the driver's driving operation. This first driving control mode is realized, for example, by the driving_ECU 14 outputting various control signals to the HEV_ECU 22, the BK_ECU 24, and the PS_ECU 25. In the first driving control mode, adaptive cruise control (ACC), active lane keep centering control (ALKC), active lane keep bouncing control (ALKB), lane change control, and the like are mainly performed in appropriate combination. This enables the host vehicle M to travel along the target driving route.

[0050] Here, the following distance control is basically performed based on the driving environment information input from the image recognition ECU 13 and the like.

[0051] More specifically, when the image recognition_ECU 14 or the like does not recognize a preceding vehicle P ahead of the host vehicle M, the traveling_ECU 14 performs constant speed traveling control as part of the following inter-vehicle distance control. In this constant speed traveling control, the traveling_ECU 14 performs acceleration / deceleration control on the host vehicle M, using a set vehicle speed input by the driver as a target vehicle speed. In this way, the traveling_ECU 14 maintains the vehicle speed of the host vehicle M at the set vehicle speed.

[0052] On the other hand, when the image recognition_ECU 13 or the like recognizes a preceding vehicle P ahead of the host vehicle M, the traveling_ECU 14 performs follow-up travel control as part of follow-up inter-vehicle distance control. In this follow-up travel control, the traveling_ECU 14 sets a target inter-vehicle distance based on the vehicle speed and the like of the preceding vehicle P, and performs acceleration / deceleration control to maintain the target inter-vehicle distance.

[0053] Here, the vehicle speed control in the following inter-vehicle distance control is performed for the entire vehicle speed range including, for example, a stopped state (0 km / h) of the host vehicle M. In other words, when a stopping element for the host vehicle M is included in the traveling environment, the traveling_ECU 14 performs automatic stop control to stop the host vehicle M on the side (host vehicle M side) of the stopping element.

[0054] Note that a stopping element when the constant speed cruise control is being executed corresponds to, for example, a stop line when a traffic light ahead of the host vehicle is red. Also, a stopping element when the adaptive cruise control is being executed corresponds to, for example, a preceding vehicle P that has stopped to wait for a traffic light or a preceding vehicle P that is expected to stop due to deceleration.

[0055] The lane centering control and lane departure prevention control are basically performed based on driving environment information input from at least one of the image recognition_ECU 13 and the locator unit 36. That is, the driving_ECU 14 sets a target travel path along the left and right lane markings in the center of the lane in which the host vehicle is traveling, based on, for example, lane marking information included in the driving environment information. Then, the driving_ECU 14 performs feedforward control and feedback control of steering based on the target travel path, thereby keeping the host vehicle M in the center of the lane.

[0056] The second driving control mode is a driving mode in which the host vehicle M is driven without the driver needing to maintain steering, operate the accelerator, or operate the brakes. That is, the second driving control mode is a so-called automatic driving mode in which the host vehicle M is driven autonomously without the driver needing to perform any driving operation. This second driving control mode is realized, for example, by the driving_ECU 14 outputting various control signals to the HEV_ECU 22, the BK_ECU 24, and the PS_ECU 25. In the second driving control mode, adaptive vehicle distance control, lane centering control, lane departure prevention control, and the like are mainly performed in appropriate combination. This enables the host vehicle M to drive along a target route (route map information).

[0057] The evacuation mode is a mode for automatically stopping the host vehicle M on a shoulder strip, etc. This evacuation mode is executed, for example, when, while the host vehicle M is traveling in the second driving control mode, it becomes impossible to continue traveling in the second driving control mode and the driver cannot take over the driving operation (i.e., when the host vehicle M cannot transition to the manual driving mode or the first driving control mode).

[0058] In addition, in each of the above-mentioned driving modes, the driving ECU 14 can appropriately perform emergency braking control (autonomous emergency braking (AEB)) etc. against obstacles such as vehicles that are likely to collide with the vehicle M.

[0059] The emergency brake control is basically intended to avoid a collision with an obstacle ahead of the host vehicle M on the target travel path by deceleration control (automatic deceleration control).

[0060] During this emergency brake control, the travel_ECU 14 calculates a predicted time for a collision with an obstacle. Then, based on the result of comparing the predicted longitudinal collision time with a preset threshold, the travel_ECU 14 executes deceleration control in stages to bring the host vehicle M to an emergency stop. Note that this type of emergency brake control is an interrupt control that is executed as needed regardless of the driving mode. Therefore, for example, even when automatic stop control is being executed as part of adaptive cruise control, the emergency brake control is executed as needed.

[0061] Next, the automatic stop control during the follow-up inter-vehicle distance control will be described in detail.

[0062] In this automatic stop control, the travel_ECU 14 sets a target stop position for the stop element.

[0063] For example, when constant speed travel control is being executed, when the traffic light ahead of the vehicle's travel lane turns red, the travel_ECU 14 sets the target stop position to a position a set distance (e.g., several tens of centimeters) before the stop line.

[0064] Also, for example, when the following cruise control is being performed and the preceding vehicle P is stopped, the travel_ECU 14 sets the target stop position to a position a set distance (for example, several tens of centimeters) in front of the preceding vehicle P.

[0065] Furthermore, for example, when the following cruise control is being performed and the decelerating preceding vehicle P is expected to stop, the travel_ECU 14 calculates a predicted travel distance Lp until the preceding vehicle P stops. Furthermore, the travel_ECU 14 calculates a position where the preceding vehicle P is moved forward by the predicted travel distance Lp from its current position as a predicted stop position of the preceding vehicle P. Then, the travel_ECU 14 sets a target stop position at a position a set distance (e.g., several tens of centimeters) before the predicted stop position of the preceding vehicle P.

[0066] Here, the predicted travel distance Lp can be calculated using, for example, the following equation (1).

[0067] Lp = Vp ２ / (2・ap) …(1)

[0068] In equation (1), Vp is the current vehicle speed of the preceding vehicle P, and ap is the current deceleration of the preceding vehicle P.

[0069] Once the target stop position is set, the travel_ECU 14 performs stop control to automatically stop the host vehicle M at the target stop position.

[0070] In this stop control, when the host vehicle M is traveling on a downward gradient and a gradient change section C where the downward gradient changes to a gentler gradient is within the longitudinal set distance Dth from the target stop position, the travel_ECU 14 corrects the target stop position to the nearer side. Note that in this embodiment, the case where the downward gradient changes to a gentler gradient includes not only a case where the downward gradient changes to a gentle downward gradient, but also a case where the downward gradient changes to an upward gradient.

[0071] In correcting the target stop position, the travel_ECU 14 sets a larger stop position correction amount (correction amount) as the gradient change amount increases. The relationship between the gradient change amount and the stop position correction amount is, for example, mapped in advance based on experiments, simulations, etc., and stored in the travel_ECU 14 (see FIG. 7). In the map shown in FIG. 7, a maximum value is set for the stop position correction amount to prevent excessive correction of the target stop position. It is preferable that the maximum value of the stop position correction amount is, for example, approximately the same as the overall length of the host vehicle M (for example, approximately 4 to 5 m).

[0072] However, when a following vehicle F is present behind the host vehicle M, the travel_ECU 14 limits the stop position correction amount more as the inter-vehicle distance between the host vehicle M and the following vehicle F (following vehicle distance) becomes smaller. Such a limitation on the stop position correction amount can be achieved, for example, by setting an upper limit value for the stop position correction amount according to the following vehicle distance. The relationship between the following vehicle distance and the upper limit value of the stop position correction amount is mapped in advance based on, for example, experiments or simulations (see FIG. 8 ). The map showing the relationship between the following vehicle distance and the upper limit value is stored in the travel_ECU 14. In this case, when the following vehicle distance is less than the set value (when it is extremely short), it is preferable to set the upper limit value for the stop position correction amount to "0" and prohibit correction of the target stop position.

[0073] Thus, in this embodiment, the travel_ECU 14 corresponds to a specific example of a target stop position setting means, a target stop position correcting means, and a stop control means.

[0074] Next, the automatic stop control during the follow-up inter-vehicle distance control will be described with reference to the flowchart of the follow-up inter-vehicle distance control routine shown in Fig. 2. This routine is repeatedly executed by the travel_ECU 14 at set time intervals, for example.

[0075] When the routine starts, in step S101, the travel_ECU 14 calculates a target stop position of the host vehicle M. The calculation of the target stop position is executed, for example, according to a flowchart of a target stop position calculation subroutine shown in FIG.

[0076] When the subroutine starts, in step S201, the traveling_ECU 14 checks, based on the traveling environment information, whether or not a preceding vehicle P is present ahead in the traveling lane of the host vehicle.

[0077] Then, when it is determined in step S201 that a preceding vehicle P exists (step S201: YES), the travel_ECU 14 proceeds to step S204.

[0078] On the other hand, if it is determined in step S201 that the preceding vehicle P does not exist (step S201: NO), the travel_ECU 14 proceeds to step S202.

[0079] In step S202, the travel_ECU 14 checks whether the traveling environment information includes a stop request for the host vehicle M. A stop request for the host vehicle M may be, for example, a case where a traffic light is present within a set distance ahead of the host vehicle's traveling lane and the traffic light is red.

[0080] If it is determined in step S202 that the request does not include a stop request for the host vehicle M (step S202: NO), the travel_ECU 14 exits the subroutine without setting a target stop position.

[0081] On the other hand, if it is determined in step S202 that a stop request for the host vehicle M is included (step S202: YES), the travel_ECU 14 proceeds to step S203.

[0082] In step S203, the travel_ECU 14 sets a target stop position based on a stop line before the traffic light, and then exits the subroutine.

[0083] Furthermore, when the process proceeds from step S201 to step S204, the traveling_ECU 14 acquires the vehicle speed Vp and deceleration ap of the preceding vehicle P based on the traveling environment information.

[0084] In the following step S205, the travel_ECU 14 checks, based on the vehicle speed Vp of the preceding vehicle P, whether the preceding vehicle P is stopped.

[0085] Then, in step S205, if it is determined that the preceding vehicle P is traveling (step S205: NO), the traveling_ECU 14 proceeds to step S207.

[0086] On the other hand, if it is determined in step S205 that the preceding vehicle P is stopped (step S205: YES), the travel_ECU 14 proceeds to step S206.

[0087] In step S206, the travel_ECU 14 sets a target stop position based on the stop position of the preceding vehicle P, and then exits the subroutine.

[0088] Furthermore, when the process proceeds from step S205 to step S207, the travel_ECU 14 checks whether or not the preceding vehicle P is likely to stop based on the vehicle speed Vp and deceleration ap of the preceding vehicle P. Here, the travel_ECU 14 determines that the preceding vehicle P is likely to stop if, for example, the vehicle speed Vp of the preceding vehicle P is low and less than a set vehicle speed, and the deceleration ap is equal to or greater than the set deceleration.

[0089] If it is determined in step S207 that the preceding vehicle P is unlikely to stop (step S207: NO), the travel_ECU 14 exits the subroutine without setting a target stop position.

[0090] On the other hand, if it is determined in step S207 that the preceding vehicle P is likely to stop (step S207: YES), the travel_ECU 14 proceeds to step S208.

[0091] In step S208, the travel_ECU 14 calculates a predicted stop position of the preceding vehicle P based on the vehicle speed Vp and deceleration ap of the preceding vehicle P. That is, the travel_ECU 14 calculates a predicted travel distance Lp using the above-mentioned equation (1) based on the vehicle speed Vp and deceleration ap. Then, the travel_ECU 14 calculates a predicted stop position based on the predicted travel distance Lp.

[0092] In the following step S209, the travel_ECU 14 sets a target stop position based on the predicted stop position of the preceding vehicle P, and then exits the subroutine.

[0093] In the main routine of FIG. 2, when the process proceeds from step S101 to step S102, the travel_ECU 14 checks whether a target stop position for the host vehicle M has been set.

[0094] Then, when it is determined in step S102 that a target stop position has been set (step S102: YES), the travel_ECU 14 proceeds to step S104.

[0095] On the other hand, if it is determined in step S102 that the target stop position has not been set (step S102: NO), the travel_ECU 14 proceeds to step S103.

[0096] In step S103, the travel_ECU 14 continues the travel control of the host vehicle M and then exits the routine. That is, if a preceding vehicle P is not recognized ahead of the host vehicle M, the travel_ECU 14 executes constant speed travel control and then exits the routine. On the other hand, if a preceding vehicle P is recognized ahead of the host vehicle M, the travel_ECU 14 executes follow-up travel control and then exits the routine.

[0097] Furthermore, when the process proceeds from step S102 to step S104, the travel_ECU 14 checks whether the host vehicle's lane is on a downward slope. To make this determination, the travel_ECU 14 compares, for example, the longitudinal acceleration of the host vehicle M calculated based on the sensor values ​​of the wheel speed sensors 42fl, 42fr, 42rl, and 42rr with the longitudinal acceleration detected by the longitudinal acceleration sensor 41. Then, based on the comparison result of these longitudinal accelerations, the travel_ECU 14 calculates the longitudinal gradient of the host vehicle's lane. Alternatively, the travel_ECU 14 can obtain the longitudinal gradient of the host vehicle's lane by reading road surface gradient data from the road map DB 36b.

[0098] If it is determined in step S104 that the lane in which the vehicle is traveling is not a downward slope (step S104: NO), the traveling_ECU 14 proceeds to step S109.

[0099] On the other hand, if it is determined in step S104 that the lane in which the host vehicle is traveling is a downward slope (step S104: YES), the traveling_ECU 14 proceeds to step S105.

[0100] In step S105, the traveling_ECU 14 checks whether the downward gradient ahead of the host vehicle's traveling lane is changing to a gentler gradient. In making this determination, the traveling_ECU 14 can refer to, for example, the traveling environment information recognized by the image recognition_ECU 13. Alternatively, if the road map information stored in the road map DB 36a includes detailed road surface gradient data, the traveling_ECU 14 can also refer to the road map information.

[0101] Then, in step S105, when it is determined that the downward gradient has not changed to a gentler gradient ahead (step S105: NO), the travel_ECU 14 proceeds to step S109.

[0102] On the other hand, if it is determined in step S105 that the downward gradient is changing to a gentler gradient ahead (step S105: YES), the travel_ECU 14 proceeds to step S106.

[0103] In step S106, the travel_ECU 14 calculates a distance D between a gradient change section C where the downward gradient changes to a gentler gradient and the target stop position.

[0104] In the next step S107, the travel_ECU 14 checks whether the distance D is less than a predetermined threshold value Dth. Here, the threshold value Dth is set to a distance approximately equal to the overall length of the host vehicle M, for example.

[0105] Then, when it is determined in step S107 that the distance D is equal to or greater than the threshold value Dth (step S107: NO), the traveling_ECU 14 proceeds to step S109.

[0106] On the other hand, when it is determined in step S107 that the distance D is less than the threshold value Dth (step S107: YES), the traveling_ECU 14 proceeds to step S108.

[0107] In step S108, the travel_ECU 14 corrects the target stop position. This correction of the target stop position is executed, for example, in accordance with the flowchart of a target stop position correction subroutine shown in FIG.

[0108] When the subroutine starts, in step S301, the traveling_ECU 14 calculates a stop position correction amount based on the gradient change amount by referring to the map shown in Fig. 7 or the like. In this calculation, the traveling_ECU 14 can refer to the gradient change amount in the traveling environment information recognized by the image recognition_ECU 13. Alternatively, if the road map information stored in the road map DB 36a includes detailed road surface gradient data, the traveling_ECU 14 can also refer to the road map information.

[0109] In the next step S302, the traveling_ECU 14 checks whether or not a following vehicle is present in the lane in which the host vehicle is traveling.

[0110] If it is determined in step S302 that there is no following vehicle (step S302: NO), the travel_ECU 14 proceeds to step S306.

[0111] On the other hand, if it is determined in step S302 that a following vehicle exists (step S302: YES), the travel_ECU 14 proceeds to step S303.

[0112] In step S303, the travel_ECU 14 calculates the inter-vehicle distance from the host vehicle M to the following vehicle (following vehicle distance).

[0113] In the following step S304, the travel_ECU 14 calculates an upper limit value for the stop position correction amount based on the following inter-vehicle distance and by referring to the map shown in FIG.

[0114] In the following step S305, the travel_ECU 14 performs upper limit processing on the stop position correction amount using the upper limit value.

[0115] When the process proceeds from step S302 or step S305 to step S306, the travel_ECU 14 corrects the target stop position to the near side using the stop position correction amount.

[0116] In the next step S307, the travel_ECU 14 checks whether the position of the rear wheels when the host vehicle M is stopped is on a downhill slope before the gradual change section C. In this case, the travel_ECU 14 calculates, as the position of the rear wheels when the host vehicle M is stopped, a position obtained by moving the target stop position forward by the length from the front end of the host vehicle M to the rear wheels.

[0117] Then, in step S307, if it is determined that the rear wheel position at the time of stopping is on a downward gradient before the gradient change section C (step S307: YES), the travel_ECU 14 exits the subroutine.

[0118] On the other hand, if it is determined in step S307 that the rear wheel position at the time of stopping is not on a downward gradient before the gradient change section C (step S307: NO), the travel_ECU 14 proceeds to step S308.

[0119] In step S308, the travel_ECU 14 cancels the correction of the target stop position using the stop position correction amount, and then exits the subroutine.

[0120] In the main routine of FIG. 2, when the process proceeds from step S104, step S105, step S107, or step S108 to step S109, the travel_ECU 14 executes automatic stop control of the host vehicle M with respect to the target stop position, and then exits the routine.

[0121] According to this embodiment, when the driving environment information includes a stopping element for automatically stopping the host vehicle M while it is traveling by adaptive vehicle distance control, the driving_ECU 14 sets a target stopping position based on the stopping element, and when the host vehicle M is traveling on a downhill slope and a gradient change section C where the downhill slope changes to a gentler slope is within a set distance from the target stopping position, the driving_ECU 14 corrects the target stopping position backward (toward the driver) and performs stopping control to stop the host vehicle M at the target stopping position.

[0122] This makes it possible to ensure safety using adaptive vehicle distance control and to suppress output when starting to travel.

[0123] That is, when the host vehicle M is traveling down a slope and a gradient change section C, where the downhill gradient becomes gentler, is within a set distance from the target stop position, the travel_ECU 14 corrects the target stop position backward. By correcting the stop position in this manner, the travel_ECU 14 actively stops at least a portion of the host vehicle M on the downhill slope before the gradient change section C (see, for example, FIGS. 9 and 10 ). This allows the host vehicle M to start traveling by effectively utilizing the potential energy of the downhill slope. This reduces the traveling load at the start of traveling and appropriately suppresses the output from the power unit at the start of traveling. Here, when the target stop position is corrected in this manner, a longer inter-vehicle distance is ensured between the host vehicle M and the preceding vehicle P at the time of starting traveling than usual. Therefore, even if the host vehicle M accelerates faster than the preceding vehicle P when starting traveling on a downhill slope, a rear-end collision of the host vehicle M with the preceding vehicle P can be effectively prevented.

[0124] In this case, the travel_ECU 14 sets a larger correction amount (stop position correction amount) for the target stop position as the gradient change amount before and after the gradient change section C increases. This makes it possible to effectively utilize the downward gradient, and also ensure a sufficient inter-vehicle distance from the preceding vehicle P if there is one.

[0125] Furthermore, when a following vehicle F is present behind the host vehicle M, the travel_ECU 14 limits the correction amount for the target stop position as the inter-vehicle distance between the host vehicle M and the following vehicle F becomes shorter (see, for example, FIG. 11 ). This makes it possible to reduce the deviation between the stop position of the host vehicle M assumed by the driver of the following vehicle F and the target stop position. Therefore, it is possible to prevent the following vehicle F from colliding with the host vehicle M.

[0126] Furthermore, when the vehicle M is stopped at the corrected target stop position, the travel_ECU 14 cancels the correction to the target stop position if it is expected that the rear wheels of the vehicle M will not be located on a downward gradient behind the gradient change section C. This makes it possible to suppress unnecessary correction to the target stop position when it is difficult to effectively utilize the potential energy of the downward gradient.

[0127] In the above-described embodiment, the image recognition_ECU 13, the driving_ECU 14, the CP_ECU 21, the HEV_ECU 22, the T / M_ECU 23, the BK_ECU 24, the PS_ECU 25, etc. are configured by well-known microcomputers including a CPU, RAM, ROM, a non-volatile storage unit, etc., and their peripheral devices. The ROM stores programs to be executed by the CPU and fixed data such as data tables in advance. Note that all or part of the functions of the processor may be configured by logic circuits or analog circuits. Furthermore, the processing of various programs may be implemented by electronic circuits such as FPGAs.

[0128] The present invention is not limited to the above-described embodiments, and various modifications and variations are possible, which are also within the technical scope of the present invention.

Claims

1. A driving support device for a vehicle, comprising: a driving environment recognition means for acquiring driving environment information of the host vehicle; a target stop position setting means for setting a target stop position based on the stop element when the stop element for automatically stopping the host vehicle during driving by following distance control is included in the driving environment information; a target stop position correction means for correcting the target stop position backward when the host vehicle is traveling on a downhill slope and a slope change portion where the downhill slope changes to the gentle slope side exists within a set distance from the target stop position; and a stop control means for stopping the host vehicle at the target stop position.

2. The driving support device for a vehicle according to claim 1, wherein the target stop position correction means sets a larger correction amount for the target stop position as the amount of slope change before and after the slope change portion is larger.

3. The driving support device for a vehicle according to claim 2, wherein the target stop position correction means restricts the correction amount as the distance between the host vehicle and the following vehicle is shorter when a following vehicle exists behind the host vehicle.

4. The driving support device for a vehicle according to claim 3, wherein the target stop position correction means prohibits the correction for the target stop position when the distance from the following vehicle is less than a set value.

5. The driving support device for a vehicle according to claim 1, wherein the target stop position correction means cancels the correction when it is assumed that the rear wheels of the host vehicle do not position on a downhill slope behind the slope change portion when the host vehicle is stopped at the corrected target stop position.

6. The driving support device for a vehicle according to claim 1, wherein the driving environment recognition means determines that the slope change portion exists on the host vehicle driving lane when the rate of decrease in the interval between the left and right dividing lines that demarcate the host vehicle driving lane changes midway on the image obtained by imaging the driving environment with a camera.

7. A driving support device for a vehicle, comprising: a driving environment recognition module that acquires driving environment information of the host vehicle; and a processor, wherein when a stop element for automatically stopping the host vehicle during driving by following distance control is included in the driving environment information, the processor sets a target stop position based on the stop element, and when the host vehicle is traveling on a downhill slope and a slope change portion where the downhill slope changes to the gentle slope side exists within a set distance from the target stop position, the processor corrects the target stop position backward and stops the host vehicle at the target stop position.

Images