JP7583569B2 - Vehicle driving support device - Google Patents

Description

The present invention relates to a vehicle driving assistance device that can perform collision avoidance control by steering intervention against an obstacle in front of the vehicle.

In recent years, various driving assistance technologies have been proposed and put into practical use for automobiles and other vehicles, reducing the burden on the driver and enabling them to drive comfortably and safely.

This type of driving assistance system is equipped with an adaptive cruise control (ACC) function and a lane keeping control function, allowing the vehicle to automatically navigate along the driving lane while maintaining a certain distance from the vehicle ahead. Furthermore, by equipping it with a locator function, the vehicle can also automatically navigate to a destination.

In such driving assistance devices, lane keeping control uses a forward recognition device such as a stereo camera mounted on the vehicle to recognize the dividing lines that separate the left and right sides of the lane in which the vehicle is traveling, and performs steering control so that the vehicle travels in the center between the dividing lines.

Furthermore, in this type of driving assistance device, when lane keeping control or the like is being performed and braking control (emergency braking, etc.) is unable to avoid a collision with an obstacle ahead of the vehicle's driving path, a technology has been proposed for performing steering intervention to avoid an emergency collision with the obstacle. For example, Patent Document 1 discloses a technology that sets an assistance area around the vehicle (particularly ahead) as an area where a collision cannot be easily avoided by normal steering, based on a relationship between vehicle speed and lateral acceleration that is preset for normal turning, and when an obstacle is present within the assistance area, avoids a collision with the obstacle by steering to generate a lateral acceleration that exceeds the maximum lateral acceleration.

WO2013/140513 publication

However, the technology disclosed in the above-mentioned Patent Document 1 does not disclose anything about what kind of lateral acceleration should be generated when steering to avoid an emergency collision. Therefore, the technology disclosed in the above-mentioned Patent Document 1 may generate excessive lateral acceleration when steering to avoid an emergency collision, which may cause discomfort to the occupants.

The present invention was made in consideration of the above circumstances, and aims to provide a vehicle driving assistance device that can achieve emergency avoidance of an obstacle by steering without generating excessive lateral acceleration.

A driving assistance device for a vehicle according to one aspect of the present invention includes obstacle recognition means for recognizing an obstacle ahead of a roadway along which the host vehicle travels, collision margin calculation means for calculating a collision margin time until the host vehicle collides with the obstacle based on a distance from the host vehicle to the obstacle and the host vehicle speed, and target lateral position calculation means for calculating a target lateral position for avoiding collision with the obstacle to a position where the host vehicle does not deviate from a dividing line of the host vehicle's lane in an avoidance direction when the collision margin time is equal to or less than a set threshold value, and a control start position is set to the host vehicle position at a time when the collision margin time becomes equal to or less than the set threshold value, and a first target route from the control start position to an intermediate position between the control start position and the target lateral position, and a second target route from the intermediate position to the target lateral position, using a maximum lateral jerk allowable according to the host vehicle speed. The vehicle control system includes a target route calculation means, an avoidance determination means for calculating a collision avoidance time required to avoid the obstacle laterally based on the first target route and the second target route, and determining that collision avoidance with the obstacle is possible by steering when the collision avoidance time is equal to or less than a threshold value set based on the collision margin time, an optimal lateral jerk calculation means for calculating the first target route and the second target route using a plurality of lateral jerks set to values equal to or less than the maximum lateral jerk when it is determined that collision avoidance with the obstacle is possible by the avoidance determination means, and calculating as an optimal lateral jerk the minimum value of the lateral jerk at which the collision avoidance time is equal to or less than the threshold value, and a steering control means for performing steering control to avoid collision with the obstacle using the optimal lateral jerk.

The vehicle driving assistance device of the present invention makes it possible to realize emergency avoidance of obstacles by steering without generating excessive lateral acceleration.

1 is a schematic configuration diagram of a driving assistance device according to a first embodiment of the present invention; A flowchart showing a collision avoidance steering control routine for an obstacle. A flowchart showing a subroutine for calculating the optimum lateral jerk using a binary search method. FIG. 2 is an explanatory diagram showing parameters used in the collision avoidance steering control according to the first embodiment. FIG. 2 is an explanatory diagram showing parameters used in the collision avoidance steering control according to the first embodiment. FIG. 2 is an explanatory diagram showing an example of the relationship between lateral acceleration and time when collision avoidance steering control is performed using maximum lateral jerk. FIG. 13 is an explanatory diagram showing an example of the relationship between lateral speed and time when collision avoidance steering control is performed using maximum lateral jerk. FIG. 13 is an explanatory diagram showing an example of the relationship between lateral position and time when collision avoidance steering control is performed using maximum lateral jerk. FIG. 11 is an explanatory diagram showing another example of the relationship between lateral acceleration and time when collision avoidance steering control is performed using the maximum lateral jerk. FIG. 11 is an explanatory diagram showing another example of the relationship between lateral speed and time when collision avoidance steering control is performed using the maximum lateral jerk. FIG. 11 is an explanatory diagram showing another example of the relationship between lateral position and time when collision avoidance steering control is performed using the maximum lateral jerk. FIG. 2 is an explanatory diagram showing an example of a trajectory of a host vehicle when collision avoidance steering control is performed using a maximum lateral jerk according to the first embodiment of the present invention; FIG. 11 is an explanatory diagram showing an example of optimal lateral jerk. 1 is a flowchart showing a collision avoidance steering control routine for an obstacle according to a second embodiment of the present invention (part 1). 2 is a flowchart showing a collision avoidance steering control routine for an obstacle. A flowchart showing a subroutine for selecting the optimum lateral jerk using a binary search method. FIG. 2 is an explanatory diagram showing parameters used in the collision avoidance steering control according to the first embodiment. FIG. 2 is an explanatory diagram showing an example of a trajectory of a host vehicle when collision avoidance steering control is performed using a maximum lateral jerk according to the first embodiment of the present invention; 10 is a flowchart showing a collision avoidance steering control routine for an obstacle according to a third embodiment of the present invention.

A first embodiment of the present invention will be described below with reference to Figs. 1 to 13. Reference numeral 1 in Fig. 1 denotes a driving assistance device for performing autonomous driving, which is mounted on a host vehicle M (see Figs. 4 and 5). This driving assistance device 1 includes a locator unit 11, a camera unit 21 as a driving environment acquisition unit, and an autonomous driving control unit 26.

The locator unit 11 has a map locator calculation unit 12 and a high-precision road map database 16 as a memory unit.

A GNSS (Global Navigation Satellite System) receiver 13 as a vehicle position acquisition unit, an autonomous driving sensor 14 as a driving state acquisition unit, and a route information input device 15 are connected to the input side of the map locator calculation unit 12. The GNSS receiver 13 receives positioning signals transmitted from multiple positioning satellites. The autonomous driving sensor 14 enables autonomous driving in environments where the reception sensitivity from the GNSS satellite is low and the positioning signal cannot be effectively received, such as driving inside a tunnel, and is composed of a vehicle speed sensor, a yaw rate sensor, and a longitudinal acceleration sensor. In other words, the map locator calculation unit 12 performs localization from the travel distance and direction based on the vehicle speed detected by the vehicle speed sensor, the yaw rate (yaw angular velocity) detected by the yaw rate sensor, and the longitudinal acceleration detected by the longitudinal acceleration sensor.

The route information input device 15 is a terminal device operated by a passenger (mainly the driver). In other words, the route information input device 15 can collect and input a series of information required to set a driving route in the map locator calculation unit 12, such as setting a destination and intermediate points (such as service areas on expressways).

This route information input device 15 is specifically an input unit of a car navigation system (e.g., a touch panel of a monitor), a mobile terminal such as a smartphone, a personal computer, etc., and is connected to the map locator calculation unit 12 by wire or wirelessly.

When a passenger operates the route information input device 15 to input information about the destination and intermediate points (facility names, addresses, telephone numbers, etc.), this input information is read by the map locator calculation unit 12.

When a destination or intermediate point is input, the map locator calculation unit 12 sets the position coordinates (latitude, longitude). The map locator calculation unit 12 includes a vehicle position estimation calculation unit 12a that serves as a vehicle position estimation unit that estimates the vehicle position, and a driving route setting calculation unit 12b that sets a driving route from the vehicle position to the destination (and intermediate point).

The high-precision road map database 16 is a large-capacity storage medium such as an HDD, and stores high-precision, well-known road map information (local dynamic map). This high-precision road map information has a hierarchical structure in which additional map information necessary to support automated driving is superimposed on the lowest static information hierarchy that serves as the basis. The additional map information includes static position information such as road type (general road, expressway, etc.), road shape, left and right dividing lines, exits of expressways and bypass roads, entrance lengths (start and end positions) of branch lanes leading to junctions and service areas, and dynamic position information such as traffic congestion information, accidents, or traffic restrictions due to construction.

The vehicle position estimation calculation unit 12a acquires the current position coordinates (latitude, longitude) of the vehicle M based on the positioning signal received by the GNSS receiver 13, and estimates the vehicle's position (current position) on the road map by map matching these position coordinates on the map information. It also identifies the lane in which the vehicle is traveling, acquires the road shape of the lane stored in the map information, and stores it sequentially. Furthermore, in an environment where it is not possible to receive a valid positioning signal from a positioning satellite due to a decrease in sensitivity of the GNSS receiver 13, such as when traveling inside a tunnel, the vehicle position estimation calculation unit 12a switches to autonomous navigation and performs localization using the autonomous driving sensor 14.

The driving route setting calculation unit 12b refers to the local dynamic map stored in the high-precision road map database 16 based on the position information (latitude, longitude) of the vehicle position estimated by the vehicle position estimation calculation unit 12a and the position information (latitude, longitude) of the input destination (and intermediate point). The driving route setting calculation unit 12b then creates a driving route on the local dynamic map connecting the vehicle position and the destination (or the destination via the intermediate point if an intermediate point is set) according to preset route conditions (recommended route, fastest route, etc.).

On the other hand, the camera unit 21 is fixed to the upper center of the front interior of the vehicle M, and has an in-vehicle camera (stereo camera) consisting of a main camera 21a and a sub-camera 21b arranged at symmetrical positions on either side of the center in the vehicle width direction, an image processing unit (IPU) 21c, and a forward driving environment recognition unit 21d. This camera unit 21 captures reference image data with the main camera 21a and captures comparison image data with the sub-camera 21b.

Then, the IPU 21c processes both sets of image data in a predetermined manner. The forward driving environment recognition unit 21d reads the reference image data and comparison image data that have been image-processed by the IPU 21c, recognizes the same object in both images based on the parallax, and calculates the distance data (the distance from the vehicle M to the object) using the principle of triangulation to recognize the forward driving environment information.

This forward driving environment information includes the road shape (dividing lines dividing the lane on which the vehicle M is driving (the vehicle's driving lane) into left and right, the road curvature [1/m] at the center between the dividing lines, and the width between the left and right dividing lines (lane width)), exits to expressways and bypass roads, etc., lane widths between dividing lines on the side of branching lanes leading to junctions, intersections, pedestrian crossings, traffic lights, road signs, moving three-dimensional objects such as preceding and oncoming vehicles, and roadside obstacles O (electric poles, utility poles, parked vehicles, etc.). In this way, IPU21c realizes the function of obstacle recognition means.

The input side of the automatic driving control unit 26 is connected to the forward driving environment recognition unit 21d of the camera unit 21, and is also connected to the map locator calculation unit 12 for bidirectional communication via an in-vehicle communication line (e.g., CAN: Controller Area Network). The output side of the automatic driving control unit 26 is connected to a steering control unit 31 that drives the host vehicle M along the driving route, a brake control unit 32 that decelerates the host vehicle M by applying forced braking, an acceleration/deceleration control unit 33 that controls the vehicle speed of the host vehicle M, and an alarm device 34 such as a monitor and a speaker.

When an automatic driving section where automatic driving control is permitted is set in the driving route set by the driving route setting calculation section 12b, the automatic driving control unit 26 sets a target route for automatic driving in the automatic driving section. Then, in the automatic driving section, the steering control section 31, the brake control section 32, and the acceleration/deceleration control section 33 are controlled in a predetermined manner to automatically drive the vehicle M along the target route based on the positioning signal indicating the vehicle position received by the GNSS receiver 13.

At that time, the autonomous driving control unit 26 uses known adaptive cruise control (ACC) and lane keeping (ALK) control based on the forward driving environment recognized by the forward driving environment recognition unit 21d to follow the preceding vehicle if a preceding vehicle is detected, and drives the host vehicle M at a set vehicle speed within the speed limit if a preceding vehicle is not detected.

In addition, as part of the ACC control, when a preceding vehicle detected ahead of the vehicle M on the road ahead of the vehicle M stops, the automatic driving control unit 26 performs braking control to stop the vehicle M by following the preceding vehicle.

Furthermore, as an interrupt control for ACC control, when an obstacle O that is likely to collide with the host vehicle M is detected ahead on the road ahead of the host vehicle M, the autonomous driving control unit 26 performs emergency braking (AEB (Autonomous Emergency Braking): collision damage mitigation brake) control to stop the host vehicle M in front of the obstacle.

Here, the obstacle O in this embodiment is a three-dimensional object that may collide with the host vehicle M, and specifically refers to a three-dimensional object that is ahead of the host vehicle M on the roadway and at least a portion of which laps the host vehicle M. This obstacle O includes not only a vehicle parked near the road shoulder (see FIG. 4), but also a preceding vehicle that suddenly decelerates or stops in front of the host vehicle M.

This emergency brake control is basically performed based on an obstacle O recognized by a stereo camera, and is performed in two stages, for example, a primary brake control and a secondary brake control.

The primary brake control is a warning brake control to prompt the driver to take action to avoid a collision with an obstacle, and is a gentle brake control that decelerates the host vehicle M using a relatively small deceleration rate a0.

Secondary brake control is a type of brake control that is performed when the driver does not perform an appropriate collision avoidance operation in response to primary brake control. It is a strong brake control that uses a deceleration rate ap greater than that of the primary brake control to decelerate the vehicle M until the relative speed with the obstacle becomes "0".

These brake controls are executed when the relationship between the relative speed Vrel and the relative distance Dcam between the vehicle M and the obstacle falls below a threshold value.

In this embodiment, specifically, the automatic driving control unit 26 calculates the brake control start distances D1th and D2th, which are distance thresholds, from the relationship between the relative speed Vrel between the vehicle M and the obstacle and the overlap rate Rap. In order to calculate these distance thresholds D1th and D2th, a map for setting the primary brake control start distance and a map for setting the secondary brake control start distance are set in advance and stored in the automatic driving control unit 26 based on experiments, simulations, etc. These maps are basically set so that the lower the relative speed Vrel, the smaller the distance threshold is set to delay the deceleration start timing, and the lower the overlap rate R, the smaller the distance threshold is set to delay the deceleration start timing. In other words, each map is set so that the lower the relative speed Vrel and the lower the overlap rate R, the more room there is for the driver to avoid a collision with the obstacle by driving the vehicle himself.

Then, when the relative distance Dcam becomes equal to or less than the primary brake control start distance D1th, the automatic driving control unit 26 performs primary brake control through the brake control unit 32 and the acceleration/deceleration control unit 33.

Furthermore, if the driver does not perform an appropriate avoidance operation during primary brake control and the relative distance Dcam becomes equal to or less than the secondary brake control start distance D2th, the autonomous driving control unit 26 performs secondary brake control through the brake control unit 32 and the acceleration/deceleration control unit 33 until the relative speed with respect to the obstacle O becomes "0".

The time to collision (TTC), which will be described later, is a parameter that is essentially synonymous with the relative distance Dcam in brake control. Therefore, it is possible to use the time to collision TTC as a parameter that indicates the relationship between the relative speed Vrel and the relative distance Dcam.

In addition, while the secondary brake control is being executed, the autonomous driving control unit 26 calculates the time to collision (TTC), which is the time until the host vehicle M collides with the obstacle O. For example, the time to collision TTC is calculated by dividing the relative distance Dcam between the host vehicle M and the obstacle O ahead by the relative speed Vrel between the host vehicle M and the obstacle O ahead ((relative distance Dcam)/(relative speed Vrel)).

If the time to collision TTC is greater than the threshold value Tth, the autonomous driving control unit 26 performs braking control via the brake control unit 32 and the acceleration/deceleration control unit 33 to stop the host vehicle M behind the obstacle O.

On the other hand, when the time to collision TTC is equal to or less than a preset threshold value Tth, the autonomous driving control unit 26 determines that it is difficult to avoid a collision with the obstacle O by braking control, and performs emergency steering (AES (Autonomous Emergency Steering): automatic steering avoidance) control through the steering control unit 31 in order to avoid an emergency collision with the obstacle O by steering. Here, the threshold value Tth is a threshold value for determining whether there is enough time to avoid a collision between the host vehicle M and the obstacle O by emergency braking control in relation to the time to collision TTC.

During this steering control, the automatic driving control unit 26 calculates a target lateral position for the host vehicle M to avoid collision with the obstacle O. The automatic driving control unit 26 also sets the host vehicle position at the time when the time to collision TTC becomes equal to or less than the set threshold value Tth as the control start position, and calculates a first target route from the control start position to an intermediate position between the control start position and the target lateral position, and a second target route from the intermediate position to the target lateral position, as target routes for emergency steering control, using a maximum lateral jerk allowable according to the host vehicle speed. The automatic driving control unit 26 also calculates a collision avoidance time t_Rap0 required for the host vehicle M to avoid the obstacle laterally based on the first target route and the second target route calculated using the maximum lateral jerk, and when the collision avoidance time t_Rap0 is equal to or less than a threshold value Tth_Rap0 (for example, Tth_Rap0 = TTC - margin α) set based on the time to collision TTC, it determines that collision with the obstacle can be avoided by steering. When it is determined that a collision with an obstacle can be avoided, the automatic driving control unit 26 uses the maximum lateral jerk (maximum lateral jerk) allowed according to the vehicle speed during steering control as a reference value and sets an optimal lateral jerk for the lateral acceleration (optimal lateral jerk equal to or less than the maximum lateral jerk) using a binary search method. That is, the automatic driving control unit 26 repeatedly updates the lateral jerk J_n using the maximum lateral jerk as a reference value a set number of times (e.g., n=10), and calculates a collision avoidance time t_Rap0 until a collision with the obstacle O can be avoided when steering control is performed to move the vehicle M to a target lateral position based on the lateral jerk J_n each time the lateral jerk J_n is updated. Then, the automatic driving control unit 26 sets the lateral jerk J_n (minimum lateral jerk) for realizing the maximum collision avoidance time t_Rap0 among the collision avoidance times t_Rap0 that are equal to or less than a threshold value Tth_rap0 set based on the time to collision TTC as the optimal lateral jerk J. Once the optimal lateral jerk J is set, the automatic driving control unit 26 performs steering control via the steering control unit 31 to move the host vehicle M to the target lateral position, thereby avoiding a collision with the obstacle O.

In this manner, in this embodiment, the autonomous driving control unit 26 realizes the functions of a collision margin calculation means, a target lateral position calculation means, a target path calculation means, an avoidance determination means, an optimal lateral jerk setting means, and a steering control means.

Next, the collision avoidance steering control for an obstacle executed by the automatic driving control unit 26 will be described with reference to the flowchart of the steering avoidance control routine shown in FIG. 2. Note that immediately after the collision avoidance steering control is performed, the automatic driving control unit 26 performs steering control (steering control after t3 in FIG. 6 to FIG. 11) to return the attitude of the host vehicle M to the traveling direction of the host vehicle's travel path, but a detailed description of this control will be omitted.

This routine is executed repeatedly at set time intervals. When the routine starts, the automatic driving control unit 26 first checks in step S101 whether or not secondary brake control is currently being executed for an obstacle O ahead of the vehicle M on the road ahead.

If it is determined in step S101 that secondary brake control is not being executed, the automatic driving control unit 26 exits the routine.

On the other hand, if it is determined in step S101 that secondary brake control is being executed, the automatic driving control unit 26 proceeds to step S102, calculates the time to collision TTC for the obstacle O, and checks whether the calculated time to collision TTC is equal to or less than the set threshold value Tth.

If it is determined that the time to collision TTC is greater than the set threshold Tth, the automatic driving control unit 26 exits the routine to leave the avoidance of collision with the obstacle O to braking control such as forced braking.

On the other hand, if it is determined that the time to collision TTC is equal to or less than the set threshold value Tth, the autonomous driving control unit 26 proceeds to step S103 and calculates a target lateral position x_avoid for the host vehicle M to avoid collision with the obstacle O.

As shown in Figures 4 and 5, for example, the target lateral position x_avoid is expressed by the following formula (1), where the vehicle width is width_own, the mirror width is width_mirror, the lateral distance from the center of the vehicle M to the side edge of the obstacle O is x_obj, and the control margin is x_margin. Note that when the obstacle O is to the right of the vehicle M, the lateral distance x_obj is negative to the left of the vehicle M and positive to the right, and the sign is reversed when the obstacle O is to the left of the vehicle M.

x_avoid=((width_own/2)-x_obj)+width_mirror+x_margin...(1)
4 and 5, z_diff indicates the distance from the host vehicle M to the obstacle O, and Rap indicates the lap amount between the host vehicle M and the obstacle O.

When the process proceeds from step S103 to step S104, the autonomous driving control unit 26 checks whether the host vehicle M' (see FIG. 4) may be present within the avoidance space when the host vehicle M is moved to the target lateral position x_avoid. Here, the host vehicle M' may be present within the avoidance space when, for example, the host vehicle M' is present within the driving lane, i.e., the host vehicle M' is not protruding from the lane marking.

If it is determined in step S104 that the host vehicle M' after the movement cannot be present within the avoidance space, the automatic driving control unit 26 exits the routine.

On the other hand, if it is determined in step S104 that the host vehicle M' may be present within the avoidance space after the movement, the automatic driving control unit 26 proceeds to step S105 and sets parameters necessary for steering-based collision avoidance control with the obstacle O.

As these parameters, the automatic driving control unit 26 sets, for example, the maximum lateral jerk when turning further: Ja_max, the maximum lateral jerk when turning back: Jd_max, the standard lateral acceleration for control: astd_max, the initial lateral speed: vinit, the initial lateral position: 0, the lateral acceleration at the end: 0, the vehicle response delay time: tdelay, and the lateral position at the end (c3: see Figures 8 and 11): (x_avoid/2). Here, the maximum lateral jerk when turning further: Ja_max and the maximum lateral jerk when turning back: Jd_max are the maximum lateral jerks that can be tolerated during steering control, and are set variably according to the vehicle speed. In the following explanation, to simplify the explanation, the lateral jerk Ja when turning further and the lateral jerk Jd when turning back will be collectively referred to as the lateral jerk J (the maximum lateral jerk is J_max).

When proceeding from step S105 to step S106, the autonomous driving control unit 26 calculates the travel trajectory (target route: first target route and second target route) when the host vehicle M is moved to the target lateral position x_avoid using the maximum lateral jerk J_max, etc. That is, the autonomous driving control unit 26, for example, substitutes various parameters such as the maximum lateral jerk J_max into a predetermined lateral acceleration calculation formula, and sequentially integrates the calculation formula to calculate the progress of the lateral acceleration a during steering control (see Figures 6 and 9), calculate the progress of the lateral velocity v (see Figures 7 and 10), and further calculate the progress of the lateral position c (see Figures 8 and 11) indicating the travel trajectory (see Figure 12) of the host vehicle M. Note that, for example, as shown in Figure 6, in this calculation, the lateral acceleration a is upper-limit processed by the control standard lateral acceleration astd.

When proceeding from step S106 to step S107, the autonomous driving control unit 26 calculates the collision avoidance time t_RAP0 (see FIG. 12), which is the time until the lap amount Rap between the host vehicle M and the obstacle O becomes "0" when the host vehicle M is driven along the calculated driving trajectory.

When proceeding from step S107 to step S108, the automatic driving control unit 26 checks whether the collision avoidance time t_Rap0 is equal to or less than a threshold value Tth_Rap0 that is set based on the time to collision TTC, i.e., whether the collision avoidance time t_Rap0 is equal to or less than a value obtained by subtracting a predetermined margin α from the time to collision TTC.

If it is determined in step S108 that the collision avoidance time t_Rap0 is greater than the threshold value Tth_Rap0, the automatic driving control unit 26 determines that it is difficult to avoid a collision with the obstacle O even if steering control is performed based on the current lateral jerk (maximum lateral jerk J_max), and exits the routine.

On the other hand, if it is determined in step S108 that the collision avoidance time t_Rap0 is equal to or less than the threshold value Tth_Rap0, the automatic driving control unit 26 determines that it is possible to avoid a collision with the obstacle O by steering control based on the current lateral jerk (maximum lateral jerk J_max), and proceeds to step S109.

When the process proceeds from step S108 to step S109, the automatic driving control unit 26 calculates the optimal lateral jerk J using a binary search method. The calculation of the optimal lateral jerk J is performed, for example, according to the flowchart of the optimal lateral jerk calculation subroutine shown in FIG. 3.

When the subroutine starts, in step S201, the automatic driving control unit 26 sets initial values for the upper limit J_upp and lower limit J_low of the lateral jerk used in the binary search method. Here, the automatic driving control unit 26 sets, for example, the maximum lateral jerk J_max as the initial value of the upper limit J_upp of the lateral jerk indicating the search range of the optimal lateral jerk J, and sets a preset value as the initial value of the lower limit J_low of the lateral jerk. Here, the value set as the initial value of the lower limit J_low of the lateral jerk can be uniformly set to "0", but it is preferable to use, for example, a value (constant) that is preset for each vehicle speed at the time when the time to collision TTC becomes equal to or less than the set threshold Tth.

When proceeding from step S201 to step S202, the automatic driving control unit 26 sets the initial value of the number of calculations n using the binary search method to "1" and then proceeds to step S203.

In step S203, the automatic driving control unit 26 checks whether the number of calculations n is less than a set number (e.g., 10).

Then, if the automatic driving control unit 26 determines in step S203 that the number of calculations n is equal to or greater than "10", the automatic driving control unit 26 proceeds to step S211, and if the automatic driving control unit 26 determines that the number of calculations n is less than "10", the automatic driving control unit 26 proceeds to step S204.

When proceeding from step S203 to step S204, the automatic driving control unit 26 sets the intermediate value between the upper limit value J_upp of the lateral jerk and the lower limit value J_low of the lateral jerk as the lateral jerk J_n for the current driving trajectory calculation.

Then, the automatic driving control unit 26 calculates the traveling trajectory due to the lateral jerk J_n in step S205, calculates the collision avoidance time t_Rap0 in the following step S206, and then proceeds to step S207. Note that the processing of steps S205 and S206 is similar to the processing of steps S106 and S107 described above, and therefore a description thereof will be omitted.

In step S207, the automatic driving control unit 26 checks whether the collision avoidance time t_Rap0 is less than or equal to the threshold value Tth_Rap0.

If it is determined in step S207 that the collision avoidance time t_Rap0 is greater than the threshold value Tth_Rap0, the automatic driving control unit 26 determines that it is difficult to avoid a collision with the obstacle O even if steering control is performed based on the current lateral jerk J_n, and proceeds to step S208.

On the other hand, if it is determined in step S207 that the collision avoidance time t_Rap0 is equal to or less than the threshold value Tth_Rap0, the automatic driving control unit 26 determines that it is possible to avoid a collision with the obstacle O by steering control based on the current lateral jerk J_n, and proceeds to step S209.

When the process proceeds from step S207 to step S208, the automatic driving control unit 26 updates the lower limit value J_low of the lateral jerk to the current lateral jerk J_n (J_low←J_n) in order to narrow the search range for the optimal lateral jerk J, and then proceeds to step S210.

On the other hand, when proceeding from step S207 to step S209, the automatic driving control unit 26 updates the upper limit value J_upp of the lateral jerk to the current lateral jerk J_n (J_upp←J_n) in order to narrow the search range for the optimal lateral jerk J, and then proceeds to step S210.

When proceeding from step S208 or step S209 to step S210, the automatic driving control unit 26 increments the number of calculations n (n←n+1) and then returns to step S203.

In step S203, if it is determined that the number of calculations n is 10 or more and the process proceeds to step S211, the automatic driving control unit 26 sets the lateral jerk J_n immediately before Tth_Rap0≧t_Rap0, i.e., the lateral jerk J_n immediately before TTC-α≧t_Rap0, as the optimal lateral jerk J, and then exits the subroutine. Note that FIG. 13 shows an example in which the lateral jerk J_9 used in the ninth calculation is set as the optimal lateral jerk J.

In the main routine of FIG. 2, when the process proceeds from step S109 to step S110, the automatic driving control unit 26 performs steering control to avoid the obstacle O using the optimal lateral jerk J, and then exits the routine.

According to this embodiment, the autonomous driving control unit 26 uses the maximum lateral jerk (maximum lateral jerk) allowed according to the vehicle speed during steering control as a reference value to repeatedly update the lateral jerk J_n a set number of times (e.g., n = 10) using a binary search method, and each time the lateral jerk J_n is updated, the autonomous driving control unit 26 calculates the collision avoidance time t_Rap0 until a collision with the obstacle O can be avoided when steering control is performed to move the vehicle M to the target lateral position based on the lateral jerk J_n, and sets the lateral jerk J_n (minimum lateral jerk) that realizes the maximum collision avoidance time t_Rap0 among the collision avoidance times t_rap0 that are equal to or less than the threshold value Tth_Rap0 set based on the collision margin time TTC as the optimal lateral jerk J, thereby making it possible to realize emergency avoidance of the obstacle O by steering without generating excessive lateral acceleration.

Next, a second embodiment of the present invention will be described with reference to Figs. 14 to 18. Here, in the above-mentioned first embodiment, emergency steering control is not activated when it is not possible to calculate a target lateral position x_avoid that allows the host vehicle M to be within the lane line (within the avoidance space) and when the collision avoidance time t_Rap0 calculated based on the target lateral position x_avoid and the maximum lateral jerk is greater than the threshold value Tth_Rap0. In contrast, in the above-mentioned case, this embodiment sets a virtual target lateral position (virtual target lateral position) x_avoid' that allows the host vehicle M to be outside the lane line, and when there is a lateral jerk J_n that moves the host vehicle M within a range that does not deviate from the lane line at the timing when the host vehicle M is stopped by emergency brake control, the region in which emergency steering control is executed is expanded when there is a lateral jerk J_n that makes the collision avoidance time t_Rap0 equal to or less than the threshold value Tth_Rap0. Note that the description of the same configuration as the above-mentioned first embodiment will be omitted as appropriate.

The collision avoidance steering control for an obstacle in this embodiment, which is executed by the automatic driving control unit 26, will be explained according to the flowchart of the steering avoidance control routine shown in Figures 14 and 15.

This routine is executed repeatedly at set time intervals. When the routine starts, the autonomous driving control unit 26 performs the same processing as steps S101 to S110 shown in the first embodiment described above. However, if it is determined in step S104 that the host vehicle M' after movement cannot be present within the avoidance space, or if it is determined in step S108 that the collision avoidance time t_Rap0 is greater than the threshold value Tth_Rap0, the autonomous driving control unit 26 proceeds to step S111 (see FIG. 15).

When the process proceeds from step S104 or step S108 to step S111, the automatic driving control unit 26 performs collision avoidance steering control in the expanded area by the process up to step S118 below. Note that, in order to ensure safety, it is desirable to perform collision avoidance steering control in this expanded area only when the obstacle O is stationary.

That is, in step S111, the autonomous driving control unit 26 calculates a virtual target lateral position x_avoid'. This virtual target lateral position x_avoid' is set to a value greater than the target lateral position x_avoid, and is a virtual target lateral position that allows the host vehicle M to be outside the lane marking. Note that this virtual target lateral position x_avoid' is set based on the lap amount Rap and the host vehicle speed, for example, by referring to a preset map or the like.

When the process proceeds from step S111 to step S112, the automatic driving control unit 26 sets parameters necessary for steering-based collision avoidance control with the obstacle O. Among these parameters, for example, (x_avoid'/2) is set for the lateral position at the end (see FIG. 17).

When the process proceeds from step S112 to step S113, the automatic driving control unit 26 performs the same processing as in steps S106 and S108 described above in the processing up to step S115.

Then, when the process proceeds from step S115 to step S116, the automatic driving control unit 26 calculates the optimal lateral jerk J using a binary search method. The calculation of the optimal lateral jerk J is performed, for example, according to the flowchart of the optimal lateral jerk calculation subroutine shown in FIG. 16.

When the subroutine starts, the automatic driving control unit 26 performs the same processing as steps S201 to S206 shown in the first embodiment described above.

Then, when proceeding from step S206 to step S207, the automatic driving control unit 26 checks whether the collision avoidance time t_Rap0 is equal to or less than the threshold value Tth_Rap0.

If it is determined in step S207 that the collision avoidance time t_Rap0 is greater than the threshold value Tth_Rap0, the automatic driving control unit 26 determines that it is difficult to avoid a collision with the obstacle O even if steering control is performed based on the current lateral jerk J_n, and proceeds to step S220.

On the other hand, if it is determined in step S207 that the collision avoidance time t_Rap0 is equal to or less than the threshold value Tth_Rap0, the automatic driving control unit 26 determines that it is possible to avoid a collision with the obstacle O by steering control based on the current lateral jerk J_n, and proceeds to step S215.

When proceeding from step S207 to step S215, the automatic driving control unit 26 selects the lateral jerk J_n immediately before Tth_Rap0≧t_Rap0, i.e., the immediately before TTC-α≧t_Rap0.

In the next step S216, the autonomous driving control unit 26 calculates the time (stopping time) t_stop until the host vehicle M is stopped by emergency brake control.

In the next step S217, the autonomous driving control unit 26 calculates the lateral position (stop lateral position) at the point in time when the stop time t_stop has elapsed, at which the host vehicle M is stopped by the emergency brake control (see FIG. 18). That is, the autonomous driving control unit 26 calculates the position of the host vehicle M on the target route at the point in time when the stop time t_stop has elapsed, when the host vehicle M is caused to travel along the target route (the travel trajectory calculated in step S205) corresponding to the selected lateral jerk Jn.

Then, when the process proceeds to step S218, it is checked whether the host vehicle M at the stopping position calculated in step S217 is within the dividing line of the host vehicle's travel path.

If it is determined in step S218 that the vehicle M is within the lane marking, the autonomous driving control unit 26 proceeds to step S219.

On the other hand, if it is determined in step S214 that the vehicle M is not within the lane marking, the autonomous driving control unit 26 proceeds to step S220.

When proceeding from step S218 to step S219, the automatic driving control unit 26 updates the upper limit value J_upp of the lateral jerk to the current lateral jerk J_n (J_upp←J_n) in order to narrow the search range for the optimal lateral jerk J, and then proceeds to step S221.

Then, in step S221, the automatic driving control unit 26 determines that there is lateral jerk that can be controlled by the extended collision avoidance steering control, and then proceeds to step S222.

When the process proceeds from step S201 or step S218 to step S220, the automatic driving control unit 26 updates the lower limit value J_low of the lateral jerk to the current lateral jerk J_n (J_low←J_n) in order to narrow the search range for the optimal lateral jerk J, and then proceeds to step S222.

When proceeding from step S220 or step S221 to step S222, the automatic driving control unit 26 increments the number of calculations n (n←n+1) and then returns to step S203.

If it is determined in step S203 that the number of calculations n is 10 or more and the process proceeds to step S223, the automatic driving control unit 26 checks whether it was determined in the above-mentioned step S221 that there is a controllable lateral jerk.

If it is not determined in step S221 that there is controllable lateral jerk, the automatic driving control unit 26 exits the subroutine from step S223.

On the other hand, if it is determined in step S221 that there is a controllable lateral jerk, the automatic driving control unit 26 proceeds from step S223 to step S224, sets the smallest lateral jerk J_n among the controllable lateral jerks as the optimal lateral jerk J, and then exits the subroutine.

In the main routine of FIG. 15, when the process proceeds from step S116 to step S117, the automatic driving control unit 26 checks in step S116 whether the optimal jerk J has been set.

If it is determined in step S117 that the optimal jerk J has not been set, the automatic driving control unit 26 exits the routine.

On the other hand, if it is determined in step S118 that the optimal jerk J has been set, the automatic driving control unit 26 proceeds to step S118, performs steering control to avoid the obstacle O using the optimal lateral jerk J, and then exits the routine.

In addition to the advantageous effects of the first embodiment described above, this embodiment has the advantageous effect of expanding the space in which a collision with the obstacle O can be avoided by emergency steering control.

Next, a third embodiment of the present invention will be described with reference to FIG. 19. Here, in the above-mentioned second embodiment, when steering to avoid an obstacle based on a target lateral position is difficult, steering to avoid the obstacle is performed based on a virtual target lateral position. In contrast, the main difference of this embodiment is that it determines in advance whether steering to avoid the obstacle is possible based on a target lateral position, and whether steering to avoid the obstacle is possible based on a virtual target lateral position. Note that descriptions of configurations similar to those of the above-mentioned first and second embodiments will be omitted as appropriate.

The collision avoidance steering control for an obstacle in this embodiment, which is executed by the automatic driving control unit 26, will be explained according to the flowchart of the steering avoidance control routine shown in FIG. 19.

This routine is executed repeatedly at set time intervals. When the routine starts, the automatic driving control unit 26 first checks in step S301 whether or not secondary brake control is currently being executed for an obstacle O ahead of the vehicle M on the road ahead.

If it is determined in step S301 that secondary brake control is not being executed, the automatic driving control unit 26 exits the routine.

On the other hand, if it is determined in step S301 that secondary brake control is being executed, the automatic driving control unit 26 proceeds to step S302, calculates the time to collision TTC for the obstacle O, and checks whether the calculated time to collision TTC is equal to or less than the set threshold value Tth.

If it is determined that the time to collision TTC is greater than the set threshold Tth, the automatic driving control unit 26 exits the routine to leave the avoidance of collision with the obstacle O to braking control such as forced braking.

On the other hand, if it is determined that the time to collision TTC is equal to or less than the set threshold value Tth, the autonomous driving control unit 26 proceeds to step S303 and checks whether it is possible to avoid a collision with the obstacle O using the target lateral position x_avoid.

In this embodiment, the autonomous driving control unit 26 has a map or the like set in advance based on experiments, simulations, etc., for determining whether or not it is possible to avoid a collision with the obstacle O based on the target lateral position x_avoid. By using this map or the like, the autonomous driving control unit 26 can determine whether or not it is possible to avoid a collision with the obstacle O based on the target lateral position x_avoid, based on the overlap rate Rap with the obstacle O, the relative speed Vrel, etc.

If it is determined in step S303 that collision avoidance with obstacle O is possible based on the target lateral position x_avoid, the autonomous driving control unit 26 proceeds to step S305, performs collision avoidance steering control based on the target lateral position x_avoid, and then exits the routine.

That is, when the process proceeds from step S303 to step S305, the automatic driving control unit 26 performs the processes of steps S103 to S110 in FIG. 2 shown in the first embodiment described above, and then exits the routine.

On the other hand, if it is determined in step S303 that it is difficult to avoid a collision with obstacle O based on the target lateral position x_avoid, the autonomous driving control unit 26 proceeds to step S304 and checks whether it is possible to avoid a collision with obstacle O using the virtual target lateral position x_avoid'.

In this embodiment, the autonomous driving control unit 26 has a map or the like set in advance based on experiments, simulations, etc., for determining whether or not it is possible to avoid a collision with the obstacle O based on the virtual target lateral position x_avoid'. By using this map or the like, the autonomous driving control unit 26 can determine whether or not it is possible to avoid a collision with the obstacle O based on the virtual target lateral position x_avoid', based on the overlap rate Rap with the obstacle O, the relative speed Vrel, etc.

If it is determined in step S304 that it is difficult to avoid a collision with the obstacle O based on the virtual target lateral position x_avoid', the autonomous driving control unit 26 exits the routine.

On the other hand, if it is determined in step S304 that collision avoidance with obstacle O is possible based on the virtual target lateral position x_avoid', the autonomous driving control unit 26 proceeds to step S306, performs collision avoidance steering control based on the virtual target lateral position x_avoid', and then exits the routine.

That is, when the process proceeds from step S304 to step S306, the autonomous driving control unit 26 performs the processes of steps S111 to S118 in FIG. 15 shown in the second embodiment described above, and then exits the routine.

According to this embodiment, it is possible to achieve the same effect as the second embodiment described above.

In each of the above-mentioned embodiments, the map locator calculation unit 12, the forward driving environment recognition unit 21d described below, the automatic driving control unit 26, the steering control unit 31, the brake control unit 32, and the acceleration/deceleration control unit 33 are configured with a well-known microcomputer equipped with a CPU, RAM, ROM, non-volatile storage unit, etc., and its peripheral devices, and 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 with logic circuits or analog circuits, and the processing of various programs may be realized by electronic circuits such as FPGAs.

The invention described in the above embodiments is not limited to those forms, and various modifications can be made in the implementation stage without departing from the gist of the invention. Furthermore, each of the above forms includes inventions at various stages, and various inventions can be extracted by appropriate combinations of the multiple constituent elements disclosed.

For example, if some constituent elements are deleted from the total constituent elements shown in each form, and the problem described can still be solved and the effect described can still be obtained, then the configuration from which these constituent elements have been deleted can be extracted as the invention.

DESCRIPTION OF SYMBOLS 1 ... Driving assistance device 11 ... Locator unit 12 ... Map locator calculation unit 12a ... Vehicle position estimation calculation unit 12b ... Travel route setting calculation unit 13 ... GNSS receiver 14 ... Autonomous driving sensor 15 ... Route information input device 16 ... High-precision road map database 21 ... Camera unit 21a ... Main camera 21b ... Sub-camera 21d ... Forward driving environment recognition unit 26 ... Automatic driving control unit 31 ... Steering control unit 32 ... Brake control unit 33 ... Acceleration/deceleration control unit 34 ... Notification device M ... Vehicle O ... Obstacle

Claims (4)

An obstacle recognition means for recognizing an obstacle ahead of the vehicle;
a collision margin time calculation means for calculating a collision margin time until the host vehicle collides with the obstacle based on a distance from the host vehicle to the obstacle and the host vehicle speed;
a target lateral position calculation means for calculating a target lateral position for avoiding a collision with the obstacle at a position where the host vehicle does not deviate from a lane marking of the host vehicle's lane in an avoidance direction when the time to collision is equal to or less than a set threshold value;
a target route calculation means for calculating a first target route from the control start position to an intermediate position between the control start position and the target lateral position, and a second target route from the intermediate position to the target lateral position, using a maximum lateral jerk allowable according to the vehicle speed, the first target route being a control start position that is a vehicle position when the time to collision becomes equal to or less than the set threshold value;
an avoidance determination means for calculating a collision avoidance time required to avoid the obstacle in a lateral direction based on the first target route and the second target route, and determining that collision avoidance with the obstacle by steering is possible when the collision avoidance time is equal to or less than a threshold value set based on the collision margin time;
an optimal lateral jerk calculation means for calculating the first target path and the second target path using a plurality of lateral jerks that are set to values equal to or less than the maximum lateral jerk when the avoidance determination means determines that collision avoidance with the obstacle is possible, and for calculating, as an optimal lateral jerk, a minimum value of the lateral jerk that makes the collision avoidance time equal to or less than the threshold value;
and a steering control means for performing steering control to avoid a collision with the obstacle by using the optimal lateral jerk. 2. The vehicle driving assistance device according to claim 1, wherein, when the collision avoidance time calculated based on the maximum lateral jerk is equal to or less than the threshold value, the optimal lateral jerk calculation means sets the maximum lateral jerk to an initial value of an upper limit value of a search range of the optimal lateral jerk and sets a preset value as an initial value of a lower limit value of the search range of the optimal lateral jerk, updates the upper limit value with the intermediate value when the collision avoidance time calculated based on a lateral jerk that is an intermediate value between the upper limit value and the lower limit value is equal to or less than the threshold value, and updates the lower limit value with the intermediate value when the collision avoidance time calculated based on the intermediate value is greater than the threshold value. The vehicle driving assistance device according to claim 1 or 2, characterized in that the collision margin calculation means calculates the collision margin when emergency brake control is executed to set the relative speed between the vehicle and the obstacle to "0". the target lateral position calculation means calculates a virtual target lateral position at a position where the host vehicle will deviate from the lane marking when the target lateral position cannot be calculated at a position where the host vehicle will not deviate from the lane marking of the host vehicle, or when at least one of the collision avoidance time based on the first target route and the second target route calculated based on the target lateral position and the maximum lateral jerk is greater than the threshold value,
the target route calculation means calculates the first target route and the second target route based on the control start position and the virtual target lateral position,
The vehicle driving assistance device according to claim 3, characterized in that the optimal lateral jerk calculation means calculates, as the optimal lateral jerk, a minimum value of the lateral jerk that moves the host vehicle within a range without deviating from the lane marking at the timing when the host vehicle is stopped by the emergency brake control, which makes the collision avoidance time equal to or less than the threshold value.

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