JP6658565B2 - Driving support device - Google Patents

Description

  The present invention relates to a driving support device that controls a steering device so that a host vehicle travels in a traveling lane.

  The position of the lane in which the vehicle is traveling (hereinafter, also referred to as “traveling lane”) is acquired from the front image captured by the on-board camera, and the vehicle travels near the center in the left-right direction of the traveling lane. There is known a driving support device that executes a steering support process for controlling a steering device of a host vehicle.

  One of such driving assistance devices (hereinafter, also referred to as “conventional device”) is to prevent the driver of the own vehicle from excessively relying on the steering assistance process, so that the driver operates the steering wheel. When the gripping state continues for a predetermined determination time (time threshold) or more, the execution of the steering assist process is stopped (for example, see Patent Document 1).

  The conventional device determines the determination time according to the traveling state of the own vehicle. Specifically, the determination time is set to be shorter when the vehicle speed of the own vehicle is higher than when the vehicle speed is lower. In addition, the conventional device sets the determination time shorter as the traveling position of the host vehicle becomes farther from the center in the left-right direction of the traveling lane.

JP 2015-120374 A

  By the way, in order to execute the steering assist processing, a pair of lane markings (specifically, a combination of a lane center line, a lane boundary line, a lane outside line, etc.) that defines a traveling lane is accurately detected from a front image. It needs to be acquired (extracted). For example, if a part of the lane marking is peeled or soiled, the accuracy of obtaining the lane marking decreases.

  When the accuracy of the lane marking decreases, the error between the acquired lane marking position and the actual lane marking position increases, so that the traveling position of the vehicle and the actual traveling The possibility that the amount of separation from the center in the left-right direction of the lane becomes large increases. In this case, it is not preferable that the state in which the driver does not hold the steering wheel continues. However, the conventional device does not consider the lane marking acquisition status (specifically, lane marking acquisition accuracy) when determining the determination time.

  Therefore, one of the objects of the present invention is to provide a driving support device that can appropriately determine the determination time (time threshold) according to the acquisition state of a lane marking.

  A driving assistance device according to the present invention for achieving the above object (hereinafter, also referred to as “the present invention device”) includes an imaging device, a lane acquisition unit, a preceding vehicle acquisition unit, a lane keeping control unit, and a grip determination unit. , And a warning processing unit.

  The imaging device (front camera 42) captures a “front image” of the vehicle (10).

The lane acquisition unit (driving assistance ECU 20)
The position of a pair of lane markings (left lane marking LL and right lane marking LR) that defines a traveling lane that is the lane in which the host vehicle travels is acquired from the front image, and the “accuracy of acquisition” is high or low. (Determination as to whether or not the similarity Ds is equal to or greater than the accuracy threshold Dth2).

The preceding vehicle acquisition unit (driving assistance ECU 20, millimeter wave radar 41, and front camera 42)
The position of a “preceding vehicle” that is in the traveling lane and runs immediately before the host vehicle is acquired.

The lane keeping control unit (the driving support ECU 20 and the EPS-ECU 33)
To allow the own vehicle to travel in the traveling lane,
A “target traveling route (Ld)” is determined based on the pair of lane markings acquired by the lane acquiring unit, and the steering angle (θs) of the own vehicle is determined so that the own vehicle travels on the target traveling route. ) Is changed to execute “lane keeping control”.

The grip determination unit (the driving support ECU 20, the EPS-ECU 33, and the torque sensor 67)
It is determined whether or not the driver is gripping a steering wheel (51) operated by the driver of the host vehicle to change the steering angle (step 515 in FIG. 5).

The warning processing unit (driving assistance ECU 20)
When the lane keeping control unit is executing the lane keeping control,
When the state in which the grip determination unit determines that the driver is not gripping the steering wheel continues for a predetermined time threshold (time threshold Tth, and time obtained by adding the warning time Tw to the time threshold Tth),
At least one of a process of issuing a warning to the driver (Step 560 in FIG. 5) and a process of stopping the lane keeping control by the lane keeping control unit (Step 555 in FIG. 5) is executed.

Further, the lane keeping control unit includes:
When the pair of lane markings cannot be acquired during execution of the lane keeping control,
If the preceding vehicle is a target vehicle that runs within a predetermined range (target vehicle area) ahead of the host vehicle,
A “following traveling process” for determining the target traveling route based on the traveling locus of the following target vehicle (preceding vehicle traveling locus Lm) is executed.

The warning processing unit,
When the following running process is not executed by the lane keeping control unit and the accuracy of the acquisition is determined to be low by the lane acquisition unit (when the reliability of the route acquisition is medium),
When the following running process is not executed by the lane keeping control unit for an arbitrary vehicle speed (Vs) of the host vehicle and the accuracy of the acquisition is determined to be high by the lane acquisition unit (route acquisition). The time threshold value is set to a smaller value as compared with the case where the reliability of the time is high (solid line L1 and solid line L2 in FIG. 3).

In addition, the warning processing unit includes:
When the following running process is executed by the lane keeping control unit (when the reliability of route acquisition is low) and the vehicle speed is higher than a predetermined speed threshold (Vth),
For a given vehicle speed, the lane keeping control unit does not execute the following traveling process, and the time threshold is smaller than when the lane acquisition unit determines that the accuracy of the acquisition is low. It is set to a value (solid line L2 and broken line L3 in FIG. 3).

Further, the warning processing unit includes:
When the following running process is executed by the lane keeping control unit and the vehicle speed is equal to or less than the speed threshold,
For any of the vehicle speeds, the time threshold is set to a value equal to the case where the lane keeping control unit has not performed the following traveling process and the lane acquisition unit determines that the accuracy of the acquisition is low. (Solid line L2 and broken line L3 in FIG. 3).

  Generally, the lane keeping control is executed to assist the driver in driving, and therefore, the driver needs to maintain the intention to drive the own vehicle even during the execution of the lane keeping control. Therefore, when the state where the driver does not hold the steering wheel continues, the device of the present invention determines that the driver lacks the driving intention, and warns the driver and / or stops the lane keeping control. Execute "warning process". By executing the warning process, the device of the present invention prompts the driver to continue driving intention.

  By the way, during execution of the lane keeping control, if the traveling position of the own vehicle is largely separated from the center of the traveling lane in the left-right direction, the driver needs to operate the steering wheel (steer) to correct the traveling position. Therefore, when there is a high possibility that the distance between the traveling position of the host vehicle and the center of the traveling lane in the left-right direction is large, it is not desirable that the state in which the driver does not hold the steering wheel continues.

  If the accuracy of the lane marking is low, a difference (error) occurs between the position of the acquired lane marking and the actual position of the lane marking. There is a high possibility that the amount of separation from the center in the left-right direction increases. Therefore, the apparatus of the present invention shortens the time threshold when the accuracy of lane marking is low compared to when the accuracy of lane marking is high.

  On the other hand, when the follow-up traveling process is executed, when the distance between the traveling position of the vehicle to be followed and the center in the left-right direction of the traveling lane is large, the traveling position of the own vehicle, the center in the left-right direction of the traveling lane, Becomes large. Therefore, the apparatus of the present invention shortens the time threshold when the following traveling process is executed, as compared with the case where the accuracy of acquiring the lane marking is low.

  However, when the vehicle speed of the own vehicle is low, the device of the present invention sets the time threshold to the same value as when the accuracy of lane marking is low. Therefore, when the distance between the traveling position of the host vehicle and the center of the traveling lane in the left-right direction does not increase rapidly due to the low vehicle speed, the time threshold value is prevented from becoming too short. As a result, the warning process is executed when the driver releases his / her hand from the steering wheel for a short period of time, thereby increasing the possibility that the occurrence of an event that the driver feels troublesome can be avoided.

  Therefore, according to the present invention, the determination time (time threshold) can be appropriately determined according to the acquisition situation of the lane marking.

  In the above description, in order to facilitate understanding of the present invention, the names and / or symbols used in the embodiments are attached in parentheses to the configurations of the invention corresponding to the embodiments described later. However, each component of the present invention is not limited to the embodiment defined by the name and / or reference numeral. Other objects, other features, and attendant advantages of the present invention will be easily understood from the description of the embodiments of the present invention described with reference to the following drawings.

It is a block diagram of a vehicle (this vehicle) concerning an embodiment of the present invention. FIG. 4 is a diagram illustrating a state in which the present vehicle and a target vehicle are traveling in a traveling lane. It is a graph showing the relationship between the vehicle speed and the time threshold for each lane marking acquisition state. 4 is a flowchart illustrating a driving support control routine executed by a driving support device provided in the vehicle. 5 is a flowchart illustrating a warning processing routine executed by a driving support device provided in the vehicle. 9 is a graph showing another example of the relationship between the vehicle speed and the time threshold for each lane marking acquisition state.

  Hereinafter, a driving assistance device (hereinafter, also referred to as “this assistance device”) according to an embodiment of the present invention will be described with reference to the drawings. The support device whose block diagram is shown in FIG. 1 is applied to the vehicle 10 shown in FIG. 2 (hereinafter, also referred to as “own vehicle 10” to distinguish it from other vehicles). The assist device includes a “drive assist ECU 20, an engine ECU 31, a brake ECU 32, and an EPS-ECU 33”, each of which is an electronic control unit (ECU).

  The driving support ECU 20 includes a CPU, a ROM, and a RAM. The CPU performs data reading, numerical calculation, and output of a calculation result by sequentially executing a predetermined program (routine). The ROM stores a program executed by the CPU, a look-up table (map), and the like. The RAM temporarily stores data.

  Each of the engine ECU 31, the brake ECU 32, and the EPS-ECU 33 includes a CPU, a ROM, and a RAM, like the driving support ECU 20. These ECUs can communicate with each other (can exchange data) via a CAN (Controller Area Network) 34. In addition, these ECUs can receive the output value of the sensor connected to the other ECU from the “other ECU” via the CAN.

  The driving support ECU 20 is connected to the millimeter wave radar 41, the front camera 42, the vehicle speed sensor 43, the yaw rate sensor 44, the operation switch 45, the display device 46, and the speaker 47.

  The millimeter wave radar 41 transmits a millimeter wave (an electromagnetic wave whose frequency is included in the range of 30 GHz to 300 GHz) to the front of the vehicle 10 and receives a reflected wave thereof. The millimeter-wave radar 41 determines the position (relative position) of the target ahead of the host vehicle 10 with respect to the host vehicle 10 and the speed (relative speed) of the target with respect to the host vehicle 10 based on the transmission wave and the reflected wave. The information is acquired as target information, and the acquired target information is output to the driving support ECU 20.

  The front camera 42 is disposed at a position near a room mirror (not shown) in the cabin of the host vehicle 10. The front camera 42 acquires an image (hereinafter, also referred to as a “front image”) of the front area of the vehicle 10 and outputs a signal representing the front image. The horizontal angle of view (field of view) of the front camera 42 is equal to the angle formed by the straight line FL and the straight line FR shown in FIG.

The vehicle speed sensor 43 detects the vehicle speed Vs of the host vehicle 10, and outputs a signal representing the vehicle speed Vs.
Yaw rate sensor 44 detects yaw rate YRa of host vehicle 10 and outputs a signal indicating yaw rate YRa.

  The operation switch 45 includes a plurality of switches (not shown) disposed on the front surface (the surface on the driver side) of the steering handle 51. The driver operates the operation switch 45 to select whether or not to cause the driving support ECU 20 to execute driving support control (specifically, following inter-vehicle distance control and lane keeping control) to be described later, and It is possible to set the target vehicle speed Vtgt reflected in the following inter-vehicle distance control.

  The display device 46 is a liquid crystal display (LCD) provided on a center console (not shown) in the cabin of the host vehicle 10. The display device 46 displays characters, symbols, and the like in accordance with an instruction from the driving support ECU 20, and provides information to the driver of the host vehicle 10.

  The speakers 47 are arranged inside (inside the vehicle compartment) of left and right front doors (not shown) of the vehicle 10. The speaker 47 can reproduce and announce a warning sound in accordance with an instruction from the driving support ECU 20.

  The engine ECU 31 is connected to a plurality of engine sensors 61 and receives detection signals from these sensors. The engine sensor 61 is a sensor that detects an operation state quantity of an engine 62 that is a drive source of the vehicle 10. The engine sensor 61 includes an accelerator pedal operation amount sensor, a throttle valve opening sensor, an engine speed sensor, an intake air amount sensor, and the like.

  Further, the engine ECU 31 is connected to an engine actuator 63 such as a throttle valve actuator and a fuel injection valve, and a transmission 64. The engine ECU 31 changes the torque Tq generated by the engine 62 and the gear ratio of the transmission 64 by controlling the engine actuator 63 and the transmission 64, thereby adjusting the driving force of the vehicle 10 to accelerate the acceleration As (the vehicle speed Vs (Amount of change per unit time).

  The brake ECU 32 is connected to a plurality of brake sensors 65, and receives detection signals from these sensors. The brake sensor 65 is a sensor that detects a parameter used when controlling a “braking device (hydraulic friction braking device) mounted on the host vehicle 10” (not shown). The brake sensor 65 includes an operation amount sensor for a brake pedal (not shown), a wheel speed sensor for detecting a rotation speed of each wheel, and the like.

  Further, the brake ECU 32 is connected to a brake actuator 66. The brake actuator 66 is a hydraulic control actuator. The brake actuator 66 is provided in a hydraulic circuit (both are not shown) between a master cylinder that pressurizes hydraulic oil by the depression force of a brake pedal and a friction brake device including a well-known wheel cylinder provided on each wheel. Is done. The brake actuator 66 adjusts the hydraulic pressure supplied to the wheel cylinder. The brake ECU 32 generates a braking force (friction braking force) Bf on each wheel by driving the brake actuator 66, and controls the acceleration As (in this case, a negative acceleration, that is, deceleration) of the host vehicle 10. It has become.

  The EPS-ECU 33 is connected to the torque sensor 67 and the steering angle sensor 68, and receives detection signals from these sensors. Each of the torque sensor 67 and the steering angle sensor 68 is disposed on a steering shaft (not shown) connected to the steering handle 51. The torque sensor 67 outputs a signal indicating the steering torque Ts applied to the steering wheel 51 by the driver. The steering angle sensor 68 outputs a signal indicating a steering angle θs that is a rotation angle of the steering shaft of the steering handle 51.

  Further, the EPS-ECU 33 is connected to the drive circuit 69. Drive circuit 69 supplies electric power to electric motor 71. The electric motor 71 generates a torque Tm for rotating the steering shaft of the steering handle 51. The EPS-ECU 33 assists the driver in steering the steering wheel 51 so that the torque Tm is equal to “the target assist torque Ta * determined based on the steering torque Ts, the steering angle θs, the vehicle speed Vs, and the like”. The driving circuit 69 is controlled at the same time.

(Driving support control-following inter-vehicle distance control)
Next, the driving support control executed by the driving support ECU 20 will be described. Driving support control includes following inter-vehicle distance control and lane keeping control. First, the following inter-vehicle distance control will be described. When the driver selects the execution of the following inter-vehicle distance control via the operation switch 45 when the following inter-vehicle distance control is not executed, the driving support ECU 20 starts the following inter-vehicle distance control.

  In the following inter-vehicle distance control, a vehicle that is a “preceding vehicle that is in the traveling lane and runs immediately before the host vehicle 10” and that the host vehicle 10 should follow (hereinafter, also referred to as a “target vehicle to be followed”). If it exists, the target acceleration Ac * of the host vehicle 10 is set so that the inter-vehicle distance to the following vehicle matches the target inter-vehicle distance Dtgt, and the actual acceleration As of the host vehicle 10 is set to the target acceleration Ac *. This is the control for matching.

  More specifically, the driving support ECU 20 determines the lateral distance of the target (n) in the area in front of the host vehicle 10 based on the target information acquired from the millimeter wave radar 41 and the front image acquired from the front camera 42. (Distance in the left-right direction) Dfy (n), vertical distance (inter-vehicle distance) Dfx (n), relative lateral speed Vfy (n), and relative vertical speed Vfx (n) are acquired. Further, the driving support ECU 20 determines that the target (n) continuously exists for a predetermined time or more in a predetermined target vehicle area such that the longer the vertical distance from the own vehicle 10 becomes, the shorter the horizontal length becomes. Is specified as the vehicle to be followed.

  Further, the driving support ECU 20 calculates the target acceleration Ac * according to one of the following equations (1) and (2). In the equations (1) and (2), Vfx (a) is the relative longitudinal speed of the target vehicle (a), and k1 and k2 are predetermined positive gains (coefficients). ΔD1 is an inter-vehicle deviation obtained by subtracting the target inter-vehicle distance Dtgt from the “inter-vehicle distance Dfx (a) of the following vehicle (a)” (that is, ΔD1 = Dfx (a) −Dtgt).

When the value (k1.DELTA.D1 + k2.Vfx (a)) is positive or "0", the driving support ECU 20 determines the target acceleration Ac * using the equation (1). ka1 is a positive gain (coefficient) for acceleration, and is set to a value of “1” or less in this example.
When the value (k1.DELTA.D1 + k2.Vfx (a)) is negative, the driving support ECU 20 determines the target acceleration Ac * using the equation (2). kd1 is a positive gain (coefficient) for deceleration, and is set to “1” in this example.

Ac * (for acceleration) = ka1 · (k1 · ΔD1 + k2 · Vfx (a)) (1)
Ac * (for deceleration) = kd1 · (k1 · ΔD1 + k2 · Vfx (a)) (2)

  When the target does not exist in the following vehicle area (that is, when there is no following vehicle), the driving support ECU 20 sets the vehicle speed Vs to “the target vehicle speed Vtgt set by the operation of the operation switch 45 by the driver”. Is determined so as to coincide with the target acceleration Ac *.

  The driving support ECU 20 transmits a request signal to the engine ECU 31 and the brake ECU 32 so that the actual acceleration As becomes equal to the target acceleration Ac *. Generally, when the target acceleration Ac * is a positive value, the driving support ECU 20 transmits a request signal requesting the engine ECU 31 to increase the torque Tq. When the target acceleration Ac * is a negative value, the driving support ECU 20 transmits a request signal requesting the engine ECU 31 to reduce the torque Tq. If the target acceleration Ac * is a negative value and its absolute value is a relatively large value, the driving support ECU 20 transmits a request signal requesting the engine ECU 31 to set the torque Tq to “0”. At the same time, a request signal requesting the brake ECU 32 to generate the braking force Bf is transmitted. As a result, the traveling of the host vehicle 10 is controlled such that the actual acceleration As of the host vehicle 10 matches the target acceleration Ac *.

  The following inter-vehicle distance control described above is described in more detail in, for example, JP-A-2014-148293, JP-A-2006-31591, Japanese Patent No. 4172434, and Japanese Patent No. 49297777.

(Driving support control-Lane keeping control)
Next, the lane keeping control will be described. If the driver selects the execution of the lane keeping control via the operation switch 45 when the following inter-vehicle distance control is executed and the lane keeping control is not executed, the driving support ECU 20 starts the lane keeping control. The lane keeping control is control for adjusting the steering angle θs by the torque Tm generated by the electric motor 71 so that the host vehicle 10 travels on the target traveling route Ld in the traveling lane.

  In order to determine the target traveling route Ld, the driving support ECU 20 recognizes (acquires) “the left lane LL and the right lane LR” of the traveling lane included in the front image. When acquiring a pair of lane markings (that is, the left lane marking LL and the right lane marking LR), the driving support ECU 20 compares the front image with a number of lane marking templates stored in advance.

  If a part of the front image similar to one of the templates (that is, the part where the lane marking is drawn in the front image) is found, the driving support ECU 20 determines that the template and the part of the front image are similar. Is expressed as a similarity Ds. The similarity Ds increases as the degree of similarity between the template and a part of the front image increases.

  If the similarity Ds is higher than the predetermined acquisition threshold Dth1, the driving support ECU 20 acquires a part of the front image as a lane marking (either the left marking LL or the right marking LR). When a pair of lane markings having a sufficient length from the host vehicle 10 to the front of the host vehicle 10 are acquired, the driving support ECU 20 determines the center in the left-right direction of the pair of lane markings as the target travel route Ld ( get.

  On the other hand, when a pair of lane markings having a sufficient length for determining the target traveling route Ld have not been acquired, the driving support ECU 20 determines the target traveling route Lm based on the traveling locus of the vehicle to be followed. The traveling route Ld is determined.

  More specifically, during the execution of the lane keeping control, the driving support ECU 20 acquires (updates) the preceding vehicle movement locus Lm every time a predetermined unit time elapses, if the following vehicle exists. If a pair of lane markings having a sufficient length has not been acquired and the preceding vehicle movement trajectory Lm has been acquired, the driving support ECU 20 determines the target traveling route Ld based on the preceding vehicle movement trajectory Lm. The process of determining the target travel route Ld based on the preceding vehicle movement trajectory Lm is also referred to as “follow-up travel process”.

  The driving support ECU 20 calculates the “vector representing the change in the relative position of the following vehicle per unit time acquired based on the target information” and “the unit of the own vehicle 10 acquired based on the vehicle speed Vs and the yaw rate YRa. With the vector representing the change in the running position (absolute position) per unit time ”as the movement locus of the following vehicle in the unit time (that is, a part of the added (updated) preceding vehicle movement locus Lm). I do.

  FIG. 2 illustrates an example of a situation in which a pair of lane markings having a sufficient length is not acquired, but the preceding vehicle movement trajectory Lm is acquired. In FIG. 2, another vehicle 81, which is a target vehicle to be followed, is traveling in the traveling lane in front of the host vehicle 10. Since the left division line LL and the right division line LR are hidden by the other vehicle 81, the lengths of the left division line LL and the right division line LR included in the front image are shortened.

  In this example, the other vehicle 81 is a large vehicle (specifically, a truck), and the length of the other vehicle 81 in the left-right direction (vehicle width direction) is longer than that of a normal vehicle (for example, a passenger vehicle). Therefore, the lengths of the left lane marking line LL and the right lane marking line LR hidden by the other vehicle 81 are longer than when the target vehicle is a normal vehicle.

  Specifically, in the range from the straight line BL to the straight line BR shown in FIG. 2 in the horizontal angle of view of the front camera 42, the positions of the left and right lane markings LR are confirmed by the other vehicle 81. No longer. Therefore, the lengths of the left division line LL and the right division line LR that can be obtained are limited to the length Ls shown in FIG.

  As shown in the example of FIG. 2, a pair of lane lane markings having a sufficient length cannot be acquired because the left lane marking LL and the right lane marking LR are hidden by the following vehicle, while the preceding vehicle movement trajectory Lm is acquired. If so, the driving support ECU 20 executes the following traveling process.

  On the other hand, if a pair of lane markings having a sufficient length have not been acquired and the preceding vehicle movement trajectory Lm has not been acquired, the driving support ECU 20 causes the display device 46 to display a warning display and the speaker 47 to display a warning. After the sound is played, the lane keeping control is stopped.

  When the target travel route Ld is obtained, the driving support ECU 20 determines the position of the vehicle 10 in the travel lane defined by the curve radius (curvature radius) R of the target travel route Ld and the left lane LL and the right lane LR. And the orientation. In addition, the driving support ECU 20 determines the center distance Dc, which is the distance in the left-right direction between the front end center position of the vehicle 10 and the target traveling route Ld, and the distance between the direction of the target traveling route Ld and the traveling direction of the vehicle 10. Is calculated.

Further, based on the center distance Dc, the angle difference θy, and the road curvature ν (road curvature ν = 1 / curvature radius R), the driving support ECU 20 calculates the target yaw rate YRc * from the following equation (3) in a predetermined calculation cycle. Is calculated. In the equation (3), K1, K2 and K3 are predetermined control gains. The target yaw rate YRc * is a yaw rate set so that the host vehicle 10 travels along the target travel route Ld.

YRc * = K1 · Dc + K2 · θy + K3 · ν (3)

  The driving support ECU 20 determines a target generated torque Tg * of the electric motor 71 required for realizing the target yaw rate YRc * at a predetermined calculation cycle based on the target yaw rate YRc * and the actual yaw rate YRa. More specifically, the driving support ECU 20 calculates a yaw rate difference ΔYR that is a difference between the target yaw rate YRc * and the actual yaw rate YRa (that is, ΔYR = YRc * −YRa). In addition, the driving support ECU 20 determines the target generated torque Tg * by applying the yaw rate difference ΔYR to a “look-up table that defines the relationship between the yaw rate difference ΔYR and the target generated torque Tg *” stored in advance. .

  Further, the driving support ECU 20 transmits a request signal to the EPS-ECU 33 so that the torque Tm generated by the electric motor 71 becomes equal to the target generated torque Tg *.

  The above-described lane keeping control is described in more detail in, for example, JP-A-2008-195402, JP-A-2009-190664, JP-A-2010-6279, and Japanese Patent No. 4349210.

(Warning process)
The purpose of the lane keeping control is to assist the driver in operating the steering wheel 51. Therefore, it is not desirable that the driver lacks the driving intention during the execution of the lane keeping control. If the state where the driver does not grip the steering wheel 51 (hereinafter, also referred to as “non-grip state”) continues, it can be determined that the driver lacks driving intention.

  Therefore, when the non-gripping state continues for the time threshold value Tth or more, the driving support ECU 20 causes the display device 46 to display a warning display and causes the speaker 47 to reproduce a warning sound. In addition, after the start of reproduction of the warning sound, the driving support ECU 20 stops the lane keeping control if the non-gripping state continues for the warning time Tw or more. The warning to the driver and the stop of the lane keeping control performed when the non-gripping state continues are also referred to as “warning processing”.

  By the way, during the execution of the lane keeping control, if the traveling position of the host vehicle 10 is greatly separated from the center in the left-right direction of the traveling lane, it is necessary to correct the traveling position by operating the steering wheel 51 by the driver. It is not desirable to continue.

  If a pair of lane markings having a sufficient length are acquired (that is, the following traveling processing is not executed) and the accuracy of acquisition of the lane marking is high, the actual center of the traveling lane in the left-right direction and the target traveling route Ld (Hereinafter, also referred to as “travel route difference”) is unlikely to increase. Therefore, it is unlikely that the amount of separation between the actual traveling position of the vehicle 10 and the center of the traveling lane in the left-right direction is large. When the following traveling process is not executed and the accuracy of lane marking is high, it is also referred to as “the reliability of route acquisition is high”.

  On the other hand, when a pair of lane markings of sufficient length are acquired and the accuracy of lane marking is low, the position of the actual lane marking is acquired as compared with the case where the reliability of route acquisition is high. It is more likely that the error between the position of the lane marking and the position of the lane marking will increase. As a result, the traveling route difference becomes large, and thus the possibility that the distance between the traveling position of the vehicle 10 and the center in the left-right direction of the traveling lane becomes large is greater than the case where the reliability of the route acquisition is high. Get higher.

  If the similarity Ds is larger than the acquisition threshold Dth1 and smaller than the “accuracy threshold Dth2 larger than the acquisition threshold Dth1” (ie, Dth1 <Ds <Dth2), the driving support ECU 20 can acquire the lane marking. However, it is determined that the lane marking accuracy is low. For example, a decrease in the accuracy of lane marking is caused by peeling and soiling of a part of the lane marking. When the following traveling process is not executed and the accuracy of the lane marking is low, it is also referred to as “the reliability of the route acquisition is medium”.

  Further, when the following traveling process is executed because a pair of lane markings having a sufficient length cannot be acquired, the traveling route difference increases if the following vehicle is not traveling in the center of the traveling lane in the left-right direction. . Therefore, the possibility that the difference in the traveling route becomes large is higher than the case where the reliability of the route acquisition is medium. When the following traveling process is being executed, hereinafter, it is also referred to as “the reliability of route acquisition is low”.

  Therefore, the driving support ECU 20 shortens the time threshold Tth as the possibility that the traveling route difference increases becomes higher. Specifically, when the reliability of the route acquisition is medium, the driving support ECU 20 sets the time threshold value Tth to a smaller value than when the reliability of the route acquisition is high.

  In addition, when the reliability of route acquisition is low, the driving support ECU 20 sets the time threshold value Tth to a smaller value than when the reliability of route acquisition is medium. However, when the vehicle speed Vs is lower than the predetermined speed threshold Vth, the driving support ECU 20 sets the time threshold Tth to the same value as when the reliability of the route acquisition is medium.

  The time threshold Tth set for each vehicle speed Vs according to the reliability of the route acquisition is indicated by the solid line L1, the solid line L2, and the broken line L3 in FIG. When the reliability of the route acquisition is high, the driving support ECU 20 applies the vehicle speed Vs to the “lookup table (Map1) that defines the relationship between the vehicle speed Vs represented by the solid line L1 in FIG. 3 and the time threshold Tth”. By doing so, the time threshold Tth is determined. Specifically, when the reliability of the route acquisition is high, the driving support ECU 20 sets the time threshold Tth to the time T1.

  When the reliability of the route acquisition is medium, the driving support ECU 20 applies the vehicle speed Vs to the “lookup table (Map2) that defines the relationship between the vehicle speed Vs represented by the solid line L2 in FIG. 3 and the time threshold Tth”. By doing so, the time threshold Tth is determined. Specifically, when the reliability of the route acquisition is medium, the driving support ECU 20 sets the time threshold Tth to the time T2.

  When the reliability of the route acquisition is low, the driving support ECU 20 applies the vehicle speed Vs to the “lookup table (Map3) that defines the relationship between the vehicle speed Vs represented by the broken line L3 in FIG. 3 and the time threshold Tth”. By doing so, the time threshold Tth is determined. Specifically, when the reliability of the route acquisition is low and the vehicle speed Vs is equal to or less than the predetermined speed threshold Vth, the driving support ECU 20 sets the time threshold Tth to the time T2. If the vehicle speed Vs is higher than the speed threshold Vth and equal to or lower than the speed V1, the driving support ECU 20 sets the time threshold Tth to a smaller value as the vehicle speed Vs increases in the range between the time T2 and the time T3. If the vehicle speed Vs is higher than the speed V1, the driving support ECU 20 sets the time threshold Tth to the time T3.

(Specific operation)
The specific operation of the driving support ECU 20 will be described. The CPU of the driving support ECU 20 (hereinafter, also simply referred to as “CPU”) executes a “driving support control routine” represented by a flowchart in FIG. 4 every time a predetermined time elapses. In addition, the CPU executes a “warning process routine” represented by a flowchart in FIG. 5 every time a predetermined execution cycle Δt (fixed value) elapses.

  First, the driving support control routine will be described. At an appropriate timing, the CPU starts the process from step 400 in FIG. 4 and proceeds to step 405, where the execution of the following inter-vehicle distance control is selected via the operation switch 45 and the execution condition of the following inter-vehicle distance control is satisfied. It is determined whether or not.

  The execution condition of the following inter-vehicle distance control is a condition that is satisfied when the vehicle speed Vs is higher than a predetermined speed V2. For example, during execution of the following inter-vehicle distance control, the vehicle speed of the vehicle to be followed becomes lower than the speed V2 (as a result, the vehicle speed Vs becomes lower than the speed V2), and the vehicle to be followed changes the lane and moves out of the lane , The execution condition of the following inter-vehicle distance control is not satisfied.

  If the execution of the following inter-vehicle distance control is selected and the execution condition of the following inter-vehicle distance control is satisfied, the CPU determines “Yes” in step 405 and proceeds to step 410 to execute the following inter-vehicle distance control. . That is, if the following inter-vehicle distance control is not executed at the present time, the CPU starts the following inter-vehicle distance control. On the other hand, if the following inter-vehicle distance control has already been executed at the present time, the CPU continues to execute the following inter-vehicle distance control.

  Next, the CPU proceeds to step 415, and determines whether execution of the lane keeping control is selected via the operation switch 45 or not. If execution of the lane keeping control is not selected, the CPU determines “No” in step 415 and proceeds to step 470 to stop execution of the lane keeping control. That is, if the lane keeping control is being executed at the present time, the CPU notifies the driver via the display device 46 and the speaker 47 and then stops the execution of the lane keeping control. On the other hand, if the lane keeping control has not been executed at the present time, the CPU continues the state where the lane keeping control has not been executed.

  On the other hand, if the execution of the lane keeping control is selected, the CPU determines “Yes” in step 415 and proceeds to step 420 to acquire a pair of lane marking lines having a sufficient length from the front image. Is determined. If a pair of lane markings having a sufficient length has been acquired, the CPU determines “Yes” in step 420 and proceeds to step 425 to acquire the target travel route Ld based on the pair of lane markings. I do.

  Next, the CPU proceeds to step 430, and determines whether or not the similarity Ds when a pair of lane markings is acquired from the front image is equal to or greater than the accuracy threshold Dth2. If the similarity Ds is equal to or greater than the accuracy threshold Dth2, the CPU makes a “Yes” determination at step 430 and proceeds to step 435 to determine that the reliability of route acquisition is high.

  Next, the CPU proceeds to step 445 to execute lane keeping control. That is, if the lane keeping control is not being executed at the present time, the CPU starts the lane keeping control. On the other hand, if the lane keeping control is currently being executed, the CPU continues to execute the lane keeping control. Next, the CPU proceeds to step 495 and ends this routine.

  On the other hand, if the determination condition in step 430 is not satisfied (that is, if the similarity Ds is smaller than the accuracy threshold Dth2), the CPU determines “No” in step 430 and proceeds to step 440 to acquire the route. Is determined to be medium. Next, the CPU proceeds to step 445.

  In addition, if the determination condition of step 420 is not satisfied (that is, if a pair of lane markings having a sufficient length is not obtained from the front image), the CPU determines “No” in step 420. Then, the process proceeds to step 455 to determine whether or not the preceding vehicle movement trajectory Lm has been acquired.

  If the preceding vehicle movement trajectory Lm has been acquired, the CPU determines “Yes” in step 455 and proceeds to step 460 to acquire the target traveling route Ld based on the preceding vehicle movement trajectory Lm. Next, the CPU proceeds to step 465 and determines that the reliability of the route acquisition is low. Next, the CPU proceeds to step 445.

  On the other hand, if the preceding vehicle movement trajectory Lm has not been acquired, the CPU determines “No” in step 455 and proceeds to step 470.

  Further, if the determination condition of step 405 is not satisfied (that is, if the execution of the following inter-vehicle distance control is not selected or the execution condition of the following inter-vehicle distance control is not satisfied), the CPU proceeds to step 405. Is determined to be "No", the process proceeds to step 450, and the execution of the following inter-vehicle distance control is stopped. That is, if the following inter-vehicle distance control is executed at the present time, the CPU notifies the driver via the display device 46 and the speaker 47 and then stops the execution of the following inter-vehicle distance control. On the other hand, if the following inter-vehicle distance control is not currently executed, the CPU continues the state in which the following inter-vehicle distance control is not executed.

  Next, a warning processing routine will be described. At an appropriate timing, the CPU starts the process from step 500 in FIG. 5, proceeds to step 505, and determines whether or not the lane keeping control is being executed. If the lane keeping control has not been executed, the CPU determines “No” in step 505 and proceeds to step 510 to set the value of the release time Thr to “0”. The value of the release time Thr is set to “0” in an initial routine (not shown) executed by the CPU when the driving support ECU 20 is started. Next, the CPU proceeds to step 595 to end this routine.

  On the other hand, if the lane keeping control has been executed, the CPU determines “Yes” in step 505 and proceeds to step 515 to determine whether or not the driver of the vehicle 10 is holding the steering wheel 51. judge. If the magnitude of the steering torque Ts is substantially “0” (that is, if the magnitude of the steering torque Ts is equal to or smaller than the small torque threshold Tsth), the CPU determines that the driver does not hold the steering wheel 51. judge. If the driver is holding the steering wheel 51, the CPU determines “No” in step 515 and proceeds to step 510.

  On the other hand, if the driver does not hold the steering wheel 51, the CPU determines “Yes” in step 515 and proceeds to step 520 to increase the value of the release time Thr by the execution period Δt.

  Next, the CPU proceeds to step 525, and obtains the reliability (any of high, medium, and low) of the route acquisition determined when the driving support control routine of FIG. 4 was last executed. Next, the CPU proceeds to step 530, and selects a look-up table (any one of Map1, Map2, and Map3) that is referred to in order to determine the time threshold Tth according to the reliability of route acquisition. Next, the CPU proceeds to step 535 to determine the time threshold Tth by applying the vehicle speed Vs to the selected look-up table.

  Next, the CPU proceeds to step 540 to determine whether or not the release time Thr is equal to or longer than the time threshold Tth. If the release time Thr is equal to or greater than the time threshold value Tth, the CPU determines “Yes” in step 540 and proceeds to step 545, where the release time Thr is equal to or greater than “the time value obtained by adding the warning time Tw to the time threshold value Tth”. It is determined whether or not there is.

  If the release time Thr is smaller than the “time obtained by adding the warning time Tw to the time threshold value Tth”, the CPU determines “No” in step 545 and proceeds to step 560, where the steering wheel 51 is gripped by the driver. A warning (non-gripping warning) is issued for the absence of a continuation. Specifically, the CPU causes the display device 46 to display a sign urging the driver to hold the steering wheel 51 and causes the speaker 47 to reproduce a warning sound. If the non-gripping warning has already been executed, the CPU continues the non-gripping warning. Next, the CPU proceeds to step 595.

  On the other hand, if the release time Thr is equal to or longer than the “time obtained by adding the warning time Tw to the time threshold value Tth”, the CPU determines “Yes” in step 545 and proceeds to step 550 to instruct the driver to perform driving support control. Notify stop. Specifically, the CPU causes the display device 46 to display a sign indicating that the driving support control is to be stopped, and causes the speaker 47 to reproduce a warning sound different from the “warning sound reproduced when the non-gripping warning is executed”.

  Next, the CPU proceeds to step 555 to stop the driving support control. Further, the CPU proceeds to step 595.

  If the determination condition in step 540 is not satisfied (that is, if the release time Thr is smaller than the time threshold Tth), the CPU determines “No” in step 540 and proceeds directly to step 595.

  As described above, when the reliability of route acquisition is medium, the present support device sets the time threshold Tth to the time T2 smaller than the value (time T1) when the reliability of route acquisition is high. Set. In addition, when the reliability of route acquisition is low and the vehicle speed Vs is higher than the speed V1, the support device sets the time threshold Tth to “time T3 shorter than time T2”. Furthermore, when the reliability of route acquisition is low, the support device sets the time threshold Tth to a value that increases from time T3 to time T2 as the vehicle speed Vs decreases from the speed V1 toward the speed threshold Vth. If the vehicle speed Vs is equal to or lower than the speed threshold Vth, the time threshold Tth is set to the time T2.

  Therefore, when there is a high possibility that the amount of separation between the target traveling route Ld and the center in the left-right direction of the pair of lane marking lines (that is, the left marking line LL and the right marking line LR) is high, the time threshold Tth is set to a short value. Is set to In addition, if the vehicle speed Vs is equal to or less than the speed threshold Vth when the following traveling process is being performed, the time threshold Tth is set longer than when the vehicle speed Vs is higher than the speed threshold Vth. For this reason, when the distance between the traveling position of the host vehicle and the center in the left-right direction of the traveling lane does not increase rapidly due to the low vehicle speed Vs, the time threshold value Tth is prevented from becoming too short. Therefore, according to the present support device, the time threshold Tth can be appropriately determined according to the acquisition situation of the lane marking.

(Modification)
Next, a modified example of the present support device will be described. In the above-described embodiment, the driving support ECU 20 determines the time threshold Tth based on the relationship between the vehicle speed Vs and the time threshold Tth represented by each of the solid line L1, the solid line L2, and the broken line L3 in FIG. In contrast, the driving support ECU 20 according to the present modification determines the time threshold Tth based on the relationship between the vehicle speed Vs and the time threshold Tth represented by the solid line L4, the solid line L5, and the broken line L6 in FIG. Only the present embodiment differs from the above-described embodiment. Hereinafter, the difference will be mainly described.

  When the reliability of route acquisition is high, the time threshold Tth is set as indicated by the solid line L4 (Map4). That is, when the reliability of route acquisition is high, the time threshold Tth is set to a smaller value as the vehicle speed Vs increases. On the other hand, when the reliability of the route acquisition is medium, the time threshold Tth is set as indicated by the solid line L5 (Map5). That is, when the reliability of route acquisition is medium, the time threshold Tth is set to a value smaller by a predetermined amount than when the reliability of route acquisition is high.

  When the reliability of the route acquisition is low, the time threshold Tth is set as indicated by a broken line L6 (Map6). That is, when the reliability of the route acquisition is low, when the vehicle speed Vs is higher than the speed V1, the time threshold Tth is a value smaller by a predetermined amount than the time threshold Tth when the reliability of the route acquisition is medium. Is set. On the other hand, when the reliability of the route acquisition is low, when the vehicle speed Vs is equal to or lower than the speed V1 and is higher than the speed threshold Vth, as the vehicle speed Vs decreases from the speed V1 toward the speed threshold Vth, the “reliability of the route acquisition” increases. Is low so that the difference between the time threshold value Tth set when is low and the time threshold value Tth set when the route acquisition reliability is medium is small. Is set, the time threshold value Tth "is set. Further, if the vehicle speed Vs is equal to or lower than the speed threshold Vth during the execution of the following traveling process, the “time threshold Tth set when the reliability of the route acquisition is low” is “the reliability of the route acquisition is medium. It is set to a value equal to the time threshold Tth set at the time.

  Although the embodiment of the driving support device according to the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the object of the present invention. For example, the warning time Tw in the present embodiment is a fixed value. However, the warning time Tw may be set according to the traveling state of the vehicle 10. For example, the warning time Tw may be set to a smaller value as the vehicle speed Vs increases.

  In addition, the driving assistance ECU 20 according to the present embodiment starts warning the driver when the non-gripping state continues for the time threshold Tth or more, and stops the lane keeping control when the non-gripping state continues for the warning time Tw. Was. That is, the driving support ECU 20 executes both the warning to the driver and the stop of the lane keeping control. However, one of the warning to the driver and the stop of the lane keeping control may be omitted. Alternatively, when stopping the lane keeping control, the driving support ECU 20 may also stop the following inter-vehicle distance control.

  In addition, the driving support ECU 20 according to the present embodiment executes the lane keeping control only during the execution of the following inter-vehicle distance control. However, the driving support ECU 20 may execute the lane keeping control when the following inter-vehicle distance control is not executed.

  In addition, the target inter-vehicle distance Dtgt according to the present embodiment is a fixed value. However, the target inter-vehicle distance Dtgt may be a value that changes according to the vehicle speed Vs. For example, the target inter-vehicle distance Dtgt may be calculated by multiplying a predetermined target inter-vehicle time Ttgt by the vehicle speed Vs (that is, Dtgt = Ttgt · Vs).

  In addition, when the magnitude of the steering torque Ts is substantially “0”, the driving support ECU 20 according to the present embodiment has determined that the driver does not hold the steering wheel 51. However, the driving support ECU 20 may determine whether the driver is holding the steering wheel 51 by a different method. For example, the driving support ECU 20 may determine whether or not the driver is holding the steering wheel 51 based on an output signal from a touch sensor disposed on the steering wheel 51. In this case, the touch sensor is, for example, a capacitive sensor, and outputs a high-level signal when the driver is holding the steering wheel 51, and outputs the high-level signal when the driver is not holding the steering wheel 51. Any sensor may be used as long as it outputs a low level signal.

DESCRIPTION OF SYMBOLS 10 ... own vehicle, 20 ... driving assistance ECU, 31 ... engine ECU, 32 ... brake ECU, 33 ... EPS-ECU, 41 ... millimeter wave radar, 42 ... front camera, 43 ... vehicle speed sensor, 44 ... yaw rate sensor, 45 ... Operation switches, 46: display device, 47: speaker, 51: steering wheel, 67: torque sensor, 68: steering angle sensor, 69: drive circuit, 71: electric motor, 81: other vehicles.

Claims (1)

An imaging device that captures a forward image of the vehicle;
A lane acquisition unit that acquires the position of a pair of lane markings that define the traveling lane that is the lane in which the host vehicle travels from the front image and determines whether the acquisition accuracy is high or low,
A preceding vehicle obtaining unit that obtains a position of a preceding vehicle that runs in front of the host vehicle in the traveling lane,
In order for the own vehicle to travel in the travel lane, a target travel route is determined based on the pair of lane markings acquired by the lane acquisition unit, and the own vehicle travels on the target travel route. A lane keeping control unit that performs lane keeping control to change the steering angle of the host vehicle;
A grip determination unit that determines whether the driver of the host vehicle is gripping a steering wheel operated by the driver to change the steering angle,
When the lane keeping control unit is executing the lane keeping control, when the state in which the grip determination unit determines that the driver is not gripping the steering wheel continues for a predetermined time threshold or more, the driving is performed. A warning processing unit that performs at least one of a process of giving a warning to a person and a process of stopping the lane keeping control by the lane keeping control unit,
With
The lane keeping control unit,
When the pair of lane markings cannot be acquired during the execution of the lane keeping control, if the preceding vehicle is a target vehicle that runs within a predetermined range in front of the host vehicle, based on the travel locus of the target vehicle. Executing a following traveling process to determine the target traveling route,
The warning processing unit,
If the lane keeping control unit does not execute the following traveling process and the lane acquiring unit determines that the accuracy of the acquisition is low, the lane keeping control unit may perform any vehicle speed of the own vehicle. By setting the time threshold to a small value as compared with a case where the following traveling process is not executed and the accuracy of the acquisition is determined to be high by the lane acquisition unit,
If the lane keeping control unit has performed the following traveling process and the vehicle speed is higher than a predetermined speed threshold, the lane keeping control unit has performed the following traveling process for any given vehicle speed. And the time threshold is set to a small value as compared with the case where the accuracy of the acquisition is determined to be low by the lane acquisition unit,
When the following running process is executed by the lane keeping control unit and the vehicle speed is equal to or less than the speed threshold, the following threshold process is executed by the lane keeping control unit with the time threshold for any vehicle speed. Not set and set to a value equal to the case where the accuracy of the acquisition is determined to be low by the lane acquisition unit,
Driving assistance device configured as follows.

Images