Driving assistance device, driving assistance method, and program

Abstract

To provide a driving support device configured to execute braking control so as to stop a vehicle when a distance between an object located in front of the vehicle and the vehicle becomes a target stopping distance and capable of reducing a possibility of a collision between the object in front of the vehicle and a following vehicle by setting an appropriate target stopping distance.SOLUTION: A driving support device includes: a sensor configured to detect an object located in front of a vehicle and moving in the same direction as the vehicle; and a controller configured to execute braking control of applying braking force to the vehicle until a predetermined termination condition is satisfied when the object satisfies a predetermined start condition. When executing the braking control, the controller sets a target stopping distance such that the target stopping distance is longer as a relative speed of the object to the vehicle is higher. When a distance between the object and the vehicle coincides with the target stopping distance, the controller applies braking force so as to stop the vehicle.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a driving assistance device that executes braking control to apply braking force to a vehicle when an object satisfies a predetermined initiation condition. [Background technology]

[0002] Conventionally, there has been known a driving assistance device that determines that an object satisfies a start condition when there is a high possibility that the object will collide with a vehicle, and executes braking control. For example, a driving assistance device described in Patent Document 1 (hereinafter referred to as the "conventional device") executes braking control when the time to collision (TTC: Time to Collision) required for the vehicle to collide with the object is equal to or less than a threshold value T0.

[0003] More specifically, the conventional device increases the braking force as the time to collision increases, and when the time to collision is long, the end of the braking control is when the vehicle is avoided, and when the time to collision is short, the end of the braking control is when the vehicle is stopped. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-926 Summary of the Invention

[0005] The target stopping distance is not described in Patent Document 1. The target stopping distance is the distance between the vehicle and the "object that satisfies the start condition" when the vehicle is stopped by braking control.

[0006] The present inventor is studying a driving assistance device (hereinafter referred to as the "study device") that performs braking control so that the vehicle stops when the distance between the vehicle and the object becomes a target stopping distance.

[0007] In such a study device, the target stopping distance is preset to a relatively small value to prevent the vehicle from colliding with a following vehicle due to sudden deceleration. However, if the target stopping distance is set to a small value, the possibility of the vehicle colliding with the object increases if the object suddenly decelerates.

[0008] On the other hand, if the target stopping distance is set to a relatively large value, the vehicle is more likely to suddenly decelerate as described above, which increases the possibility of a following vehicle colliding with the vehicle.

[0009] The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to provide a driving assistance device that performs braking control so that the vehicle stops when the distance between the vehicle and an object located in front of the vehicle reaches a target stopping distance, and that can reduce the possibility of a collision with an object in front of the vehicle (e.g., a preceding vehicle) and a following vehicle by setting an appropriate target stopping distance.

[0010] The driving assistance device of the present invention (hereinafter referred to as "the device of the present invention") a sensor (22) for detecting an object located in front of the vehicle (VA) and moving in the same direction as the vehicle; a controller (20) for executing braking control (steps 400 to 495) to apply braking force to the vehicle when the object satisfies a predetermined start condition (step 325 "Yes") until a predetermined end condition is met (step 335 "Yes", step 345 "Yes"), The controller If the braking control is being performed (step 405 "Yes"), the target stopping distance is set so that it becomes longer as the relative speed of the object with respect to the vehicle increases (step 415); applying the braking force so that the vehicle stops when the distance between the object and the vehicle matches the target stopping distance (step 425); It is structured as follows.

[0011] According to the device of the present invention, the target stopping distance is set to be longer as the relative speed increases, thereby reducing the possibility of the vehicle colliding with a "suddenly decelerating object ahead" when the relative speed is high, and reducing the possibility of the vehicle being hit by a following vehicle when the relative speed is low. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic system configuration diagram of a driving assistance device according to an embodiment of the present invention; [Figure 2] FIG. 4 is an explanatory diagram of a target stopping distance map. [Figure 3] 4 is a flowchart of a program executed by a CPU of a driving assistance ECU. [Figure 4] 4 is a flowchart of a program executed by a CPU of a driving assistance ECU. [Figure 5] FIG. 10 is an explanatory diagram of a target stopping distance map according to a first modified example. DETAILED DESCRIPTION OF THE INVENTION

[0013] A driving assistance device (the assistance device 10) according to an embodiment of the present invention is applied to a vehicle VA, and includes the components shown in FIG.

[0014] The driving assistance ECU is an ECU that executes driving assistance control, which is a type of autonomous driving, and will be referred to as "ECU 20" below.

[0015] In this specification, an "ECU" is an electronic control unit that includes a microcomputer as its main component. The ECU is also called a controller. The microcomputer includes a CPU (processor), ROM, RAM, an interface, etc. The ECU 20 and some or all of the multiple ECUs described below may be integrated into a single ECU.

[0016] The millimeter wave radar 22 acquires object information of an object located in front of the vehicle VA, and transmits the object information to the ECU 20. The object information includes information relating to the following items (1) to (4). (1) Distance D from vehicle VA to the object (hereinafter referred to as "vehicle distance D"). (2) Lateral position L of the object relative to the vehicle VA (3) Relative velocity Vr of the object to the vehicle VA (4) Type of object (vehicle, pedestrian, motorcycle, etc.)

[0017] The vehicle speed sensor 24 detects the speed (vehicle speed Vs) of the vehicle VA. The acceleration sensor 26 detects the acceleration G of the vehicle VA. The ECU 20 receives the detection values ​​from these sensors 24 and 26.

[0018] The power management ECU 30 is connected to a power train actuator 32 and controls the power train actuator 32. The power train actuator 32 changes the driving force generated by a drive device (for example, an internal combustion engine and / or an electric motor) of the vehicle VA.

[0019] The brake ECU 40 is connected to the brake actuator 42 and controls the brake actuator 42. The brake actuator 42 controls the braking force applied to the vehicle VA.

[0020] The CGW (control gateway) ECU 60 controls the transmission and reception of data between the above-mentioned plurality of ECUs via the first communication line C1 and the second communication line C2.

[0021] (Activation) The operation of the ECU 20 of the assistance device 10 will now be described. The ECU 20 executes braking control from when a start condition, which will be described later, is satisfied until when a termination condition, which will be described later, is satisfied.

[0022] In braking control, the ECU 20 transmits a "target deceleration Gtgt for stopping the vehicle VA when the inter-vehicle distance D becomes the target stopping distance Dtgt" to the power management ECU 30 and the brake ECU 40. The inter-vehicle distance D represents the distance between the vehicle VA and a "forward object that satisfies the start condition." A forward object is a moving object moving in front of the vehicle VA in the same traveling direction as the vehicle VA. An example of a forward object is a preceding vehicle traveling in the same lane as the vehicle VA and located within a predetermined distance in front of the vehicle VA; an oncoming vehicle is not a forward object. Note that a forward object may be limited to an object whose object type is "vehicle."

[0023] The power management ECU 30 and the brake ECU 40 respectively control the power train actuator 32 and the brake actuator 42 so that the acceleration G coincides with the target deceleration Gtgt.

[0024] The ECU 20 determines the target stopping distance Dtgt so that the target stopping distance Dtgt increases as the relative speed Vr increases. Specifically, the ECU 20 determines the target stopping distance Dtgt by applying the relative speed Vr to the target stopping distance map MapDtgt(Vr) shown in Fig. 2. Note that the relative speed Vr when the forward object approaches the vehicle VA is a positive value.

[0025] The target stopping distance map MapDtgt(Vr) defines the relationship between the target stopping distance Dtgt and the relative speed Vr, and is stored in the ROM of the ECU 20. As shown in FIG. 2, the target stopping distance map MapDtgt(Vr) defines this relationship so that the target stopping distance Dtgt becomes longer as the relative speed Vr increases. In detail, if the relative speed Vr is smaller than "Vr1," the target stopping distance Dtgt becomes "D1," and if the relative speed Vr is larger than "Vr2 (>Vr1)," the target stopping distance Dtgt becomes "D2 (>D1)." If the relative speed Vr is equal to or larger than "Vr1" and equal to or smaller than "Vr," the target stopping distance Dtgt becomes longer as the relative speed Vr increases.

[0026] Here, the distance that the vehicle VA travels until its vehicle speed Vs matches the speed of the object ahead when the object ahead suddenly decelerates is called the “braking distance.” The braking distance when the relative speed Vr is high is longer than the braking distance when the relative speed Vr is low.

[0027] On the other hand, shortening the target stopping distance Dtgt increases the distance required for the vehicle VA to stop, reducing the likelihood of the vehicle VA suddenly decelerating. Therefore, the shorter the target stopping distance Dtgt, the lower the likelihood of the vehicle VA being hit by a following vehicle.

[0028] From these two perspectives, in this embodiment, the target stopping distance Dtgt is made longer as the relative speed Vr increases, and the target stopping distance Dtgt is made shorter as the relative speed Vr decreases. As a result, when the relative speed Vr is high, the distance between the forward object and the vehicle VA increases, reducing the possibility of the vehicle VA colliding with a "forward object that has suddenly decelerated." When the relative speed Vr is low, the distance between the forward object and the vehicle VA decreases, reducing the possibility of the vehicle VA suddenly decelerating, reducing the possibility of the vehicle VA being collided with a following vehicle.

[0029] ·Starting conditions Condition S1: An object exists ahead. Condition S2: The time to collision (hereinafter referred to as "TTC") of the forward object is equal to or less than a predetermined start threshold time Tsth. The TTC is the time it takes for the vehicle VA to collide with the object ahead. The ECU 20 obtains the TTC by dividing the inter-vehicle distance D to the object ahead by the relative speed Vr of the object ahead. When both the above conditions S1 and S2 are satisfied, the ECU 20 determines that the start condition is satisfied.

[0030] Termination conditions Condition E1: The vehicle speed Vs becomes 0 km / h (that is, the vehicle VA is stopped). Condition E2: The TTC of the forward object is equal to or less than the predetermined end threshold time Teth. The end threshold time Teth is set to a value greater than the start threshold time Tsth. If either the condition E1 or the condition E2 is satisfied, the ECU 20 determines that the termination condition is satisfied.

[0031] (Specific operation) The CPU of the ECU 20 executes the routine shown in the flowcharts of FIGS. 3 and 4 every time a predetermined time elapses.

[0032] <Start / End Judgment> Therefore, when the appropriate time arrives, the CPU begins processing at step 300 in FIG.

[0033] Step 305: The CPU acquires object information from the millimeter wave radar 22. Step 310: The CPU determines whether the value of the execution flag Xexe is “0” or not.

[0034] The value of the execution flag Xexe is set to "1" when the above start condition is met, and is set to "0" when the above end condition is met. The value of the execution flag Xexe is also set to "0" in the initial routine. The initial routine is a routine executed by the CPU when the ignition key switch (not shown) of the vehicle VA is changed from the off position to the on position.

[0035] If the value of the execution flag Xexe is "0", the CPU determines "Yes" in step 310 and proceeds to step 315. In step 315, the CPU determines whether or not a forward object exists based on the object information.

[0036] If no forward object exists, the CPU determines "No" in step 315, proceeds to step 395, and temporarily ends this routine.

[0037] If an object ahead exists, the CPU determines "Yes" in step 315 and executes steps 320 and 325 in this order.

[0038] Step 320: The CPU obtains the TTC of the forward object based on the object information. Step 325: The CPU determines whether the TTC of the forward object is less than or equal to the start threshold time Tsth.

[0039] If the TTC of the forward object is greater than the start threshold time Tsth, the CPU determines "No" in step 325, proceeds to step 395, and temporarily ends this routine.

[0040] If the TTC of the forward object is equal to or less than the start threshold time Tsth, the CPU determines "Yes" in step 325 and proceeds to step 330. In step 330, the CPU sets the value of the execution flag Xexe to "1", proceeds to step 395, and temporarily ends this routine.

[0041] If the value of the execution flag Xexe is "1" when the CPU proceeds to step 310, the CPU determines "No" in step 310 and proceeds to step 335. In step 335, the CPU determines whether the vehicle speed Vs is "0 km / h".

[0042] If the vehicle speed Vs is not "0 km / h", the CPU determines "No" in step 335 and executes steps 340 and 345 in this order.

[0043] Step 340: The CPU obtains the TTC of the forward object based on the object information. Step 345: The CPU determines whether the TTC of the forward object is equal to or greater than the end threshold time Teth.

[0044] If the TTC of the forward object is less than the end threshold time Teth, the CPU determines "No" in step 345, proceeds to step 395, and temporarily ends this routine.

[0045] If the vehicle speed Vs is "0 km / h" when the CPU proceeds to step 335, the CPU determines "Yes" in step 335 and proceeds to step 350. In step 350, the CPU sets the value of the execution flag Xexe to "0", proceeds to step 395, and temporarily ends this routine.

[0046] If the TTC of the forward object is equal to or greater than the end threshold time Teth when the CPU proceeds to step 345, the CPU determines "Yes" in step 345 and sets the value of the execution flag Xexe to "0" in step 350. Thereafter, the CPU proceeds to step 395 and temporarily ends this routine.

[0047] If the CPU determines that the forward object no longer exists, it determines "Yes" in step 345, and sets the value of the execution flag Xexe to "0" in step 350.

[0048] <Braking control routine> When an appropriate time arrives, the CPU starts the process from step 400 in Fig. 4 and proceeds to step 405. In step 405, the CPU determines whether the value of the execution flag Xexe is "1".

[0049] If the value of the execution flag Xexe is "0", the CPU determines "No" in step 405, proceeds to step 495, and temporarily ends this routine.

[0050] If the value of the execution flag Xexe is "1", the CPU determines "Yes" in step 410 and executes steps 410 to 425 in order.

[0051] Step 410: The CPU acquires object information from the millimeter wave radar 22. Step 415: The CPU obtains the target stopping distance Dtgt by applying the relative speed Vr of the forward object to the vehicle VA to the target stopping distance map MapDtgt(Vr).

[0052] Step 420: The CPU obtains the target deceleration Gtgt based on the vehicle speed Vs, the inter-vehicle distance D, and the target stopping distance Dtgt. As an example, the CPU obtains the target deceleration Gtgt by applying the vehicle speed Vs, the inter-vehicle distance D, and the target stopping distance Dtgt to the following equation (1).

[0053]

number

[0054] Equation (1) can be obtained by substituting equation (2) for t in equation (3). Equation (2) expresses the time t required for the vehicle speed Vs to reach "0 km / h." Equation (3) expresses that the distance traveled by the vehicle VA during the time t is equal to the "distance obtained by subtracting the target stopping distance Dtgt from the inter-vehicle distance D."

[0055] t=Vs / Gtgt...(2) formula

[0056]

number

[0057] Step 425: The CPU transmits the target deceleration Gtgt to the power management ECU 30 and the brake ECU 40. Thereafter, the CPU proceeds to step 495 and temporarily ends this routine.

[0058] The assistance device 10 sets a longer target stopping distance Dtgt as the relative speed Vr increases, thereby reducing the possibility of the vehicle VA colliding with a "suddenly decelerating object ahead" when the relative speed Vr is high, and reducing the possibility of the vehicle VA colliding with a following vehicle when the relative speed Vr is low.

[0059] (First Modification) The ROM of the ECU 20 according to the first modification stores a target stopping distance map MapDtgt(Vr) shown in Fig. 5. As shown in Fig. 5, this map MapDtgt(Vr) defines three relationships (A) to (C) between the relative speed Vr and the target stopping distance Dtgt according to the vehicle speed Vs.

[0060] When the vehicle speed Vs is less than the first threshold vehicle speed V1th, the CPU acquires the target stopping distance Dtgt by applying the relative speed Vr to the above relationship (A). When the vehicle speed Vs is equal to or greater than the first threshold vehicle speed V1th and less than a second threshold vehicle speed V2th that is greater than the first threshold vehicle speed V1th, the CPU acquires the target stopping distance Dtgt by applying the relative speed Vr to the above relationship (B). When the vehicle speed Vs is equal to or greater than the second threshold vehicle speed V2th, the CPU acquires the target stopping distance Dtgt by applying the relative speed Vr to the above relationship (C).

[0061] Of the above relationships (A) to (C), as shown in Figure 5, the target stopping distance Dtgt of the relationship (C) is the longest, the target stopping distance Dtgt of the relationship (B) is the next longest after the relationship (C), and the target stopping distance Dtgt of the relationship (C) is the shortest.

[0062] For example, if the relative speed Vr is the same when the vehicle speed Vs is a "first value smaller than the first threshold vehicle speed V1th" and when the vehicle speed Vs is a "second value greater than or equal to the first threshold vehicle speed V1th and less than the second threshold vehicle speed V2th," the target stopping distance Dtgt when the vehicle speed Vs is the second value will be longer than the target stopping distance Dtgt when the vehicle speed Vs is the first value.

[0063] When the relative speed Vr is the same when the vehicle speed Vs is high and when the vehicle speed Vs is low, the greater the vehicle speed Vs, the greater the moving speed of the forward object. The braking distance when the forward object suddenly decelerates becomes longer as the vehicle speed Vs increases. For this reason, in this modified example, even if the relative speed Vr is the same, the target stopping distance Dtgt is increased as the vehicle speed Vs increases. As a result, this modified example can further reduce the possibility of a collision with a suddenly decelerating forward object.

[0064] (Second Modification) The sensor for detecting an object ahead of the vehicle VA is not limited to the millimeter-wave radar 22. As an example, such a sensor may be a camera. Furthermore, the ECU 20 may detect an object ahead of the vehicle VA by integrating information about the object detected by the camera and object information acquired by the millimeter-wave radar 22.

[0065] (Third Modification) The conditions for terminating the braking control are not limited to the above conditions E1 and E2. For example, the ECU 20 may determine that the termination condition is met when it detects an accelerator override. The ECU 20 detects an accelerator override when the depression amount of the accelerator pedal (not shown) becomes equal to or greater than a threshold amount within a predetermined time after the depression speed of the accelerator pedal (not shown) becomes equal to or greater than a threshold speed.

[0066] (Fourth Modification) The relationship between the target stopping distance Dtgt and the relative speed Vr defined by the target stopping distance map MapDtgt(Vr) is not limited to the examples shown in Figures 2 and 5, and may be any relationship in which the target stopping distance Dtgt becomes longer as the relative speed Vr increases.

[0067] (Fifth Modification) The assistance device 10 is applicable to vehicles such as engine automobiles, hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), fuel cell electric vehicles (FCEVs), and battery electric vehicles (BEVs). Furthermore, the assistance device 10 is applicable to autonomous vehicles.

[0068] The present invention can also be understood as a computer-readable non-transitory storage medium that stores a program for realizing the functions of the assistance device 10. [Explanation of symbols]

[0069] 10...driving assistance device, 20...driving assistance ECU, 22...camera, 30...power management ECU, 32...power train actuator, 40...brake ECU, 42...brake actuator

Claims

1. a sensor for detecting an object located in front of the vehicle and moving in the same direction as the vehicle; a controller for executing braking control to apply a braking force to the vehicle until a predetermined termination condition is met when the object satisfies a predetermined start condition, The controller When the braking control is being performed, a target stopping distance is set so as to become longer as the relative speed of the object with respect to the vehicle increases; applying the braking force so that the vehicle stops when the distance between the object and the vehicle matches the target stopping distance; It was configured as follows: Driving assistance device.

2. The driving assistance device according to claim 1, the controller is configured to, when the relative speed is the same when a vehicle speed representing a speed of the vehicle is a first value and when the vehicle speed is a second value greater than the first value, set the target stopping distance when the vehicle speed is the second value to be longer than the target stopping distance when the vehicle speed is the first value; Driving assistance device.

3. A driving assistance method in which a computer mounted on a vehicle executes braking control to apply a braking force to the vehicle from when a predetermined start condition is satisfied by an object located in front of the vehicle and moving in the same traveling direction as the vehicle, until a predetermined end condition is satisfied, comprising: The driving assistance method includes: a first step of setting a target stopping distance so that the target stopping distance increases as the relative speed of the object with respect to the vehicle increases when the computer is executing the braking control; a second step in which the computer applies the braking force so that the vehicle stops when the distance between the object and the vehicle matches the target stopping distance; Including, Driving assistance methods.

4. A program causing a computer mounted on a vehicle to execute braking control for applying a braking force to the vehicle from when a predetermined start condition is satisfied by an object located in front of the vehicle and moving in the same traveling direction as the vehicle until a predetermined end condition is satisfied, The program causes the computer to: a first step of setting a target stopping distance so that the target stopping distance increases as the relative speed of the object with respect to the vehicle increases when the braking control is being performed; a second step of applying the braking force so that the vehicle stops when the distance between the object and the vehicle matches the target stopping distance; Execute program.

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