Driving Support Devices

Abstract

To provide a drive support device which can reduce the uncomfortable feeling of an occupant of a vehicle.SOLUTION: A drive support ECU calculates a speed of a preceding vehicle on the basis of peripheral information, suspends tracking control when a relative speed being the speed of the preceding vehicle to the own vehicle shifts to a state where the speed is larger than "0" from a state where the speed is smaller than "0" during execution of deceleration control and it detects that the lamp color of the closest traffic light in the travel direction of the own vehicle and preceding vehicle is red on the basis of the peripheral information, and can execute exceptional control being exceptional control that allows an inter-vehicle distance from becoming larger than a target value and including at least one of first exceptional control that controls a drive device and a brake device such that the acceleration of the own vehicle is held to a prescribed value smaller than "0" and second exceptional control that controls the drive device and the brake device such that the acceleration of the own vehicle gradually increases from the prescribed value.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a driving assistance device that controls a drive device and a brake device of a host vehicle so that a distance between the host vehicle and a preceding vehicle coincides with a target value. [Background technology]

[0002] Conventionally, a driving assistance device (hereinafter referred to as "conventional device") has been proposed that performs cruise control to assist in the operation of the accelerator pedal and brake pedal of a vehicle (see Patent Document 1 below). Specifically, the conventional device controls the drive device and braking device of the host vehicle so that the inter-vehicle distance between the preceding vehicle and the host vehicle matches a target value. For example, when the preceding vehicle repeatedly decelerates and accelerates (changes acceleration), the conventional device changes the speed of the host vehicle in accordance with the speed fluctuation of the preceding vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-123831 A Summary of the Invention

[0004] Here, when the conventional device is performing cruise control and the nearest traffic light in the traveling direction of the vehicle is "red," the occupants of the vehicle expect the conventional device to decelerate the vehicle and stop it in front of the traffic light. However, in this situation, if the speed of the preceding vehicle fluctuates as in the above example, the conventional device fluctuates the speed of the vehicle to follow the preceding vehicle. In this way, the behavior of the vehicle differs from the behavior expected by the occupants. Therefore, there is a risk that the occupants of the vehicle will feel uncomfortable. In addition, in the above case, the acceleration of the vehicle fluctuates relatively greatly. Such a large fluctuation in acceleration is also one of the factors that cause discomfort to the occupants of the vehicle.

[0005] An object of the present invention is to provide a driving assistance device that can reduce discomfort felt by vehicle occupants.

[0006] In order to solve the above problems, a driving assistance device (1) according to the present invention comprises: A drive device (20) that applies a drive force to drive wheels of a host vehicle (V); a braking device (30) for applying a braking force to the drive wheels; A surroundings sensor (50) that outputs surrounding information, which is information about targets around the vehicle. and, a driving assistance control device (10) that determines a target value (Ld) of a distance between the host vehicle and a preceding vehicle (VF) traveling immediately before the host vehicle based on the peripheral information, and executes a following control that controls the drive device and the braking device so that an actual measured value of the distance between the vehicles obtained based on the peripheral information coincides with the target value; Equipped with The following control is performed when the preceding vehicle decelerates and the inter-vehicle distance becomes smaller than the target value. The driving device and the braking device are controlled so that the acceleration of the host vehicle coincides with a predetermined value smaller than "0". a deceleration control for decelerating the host vehicle to bring the reduced inter-vehicle distance closer to the target value, The driving assistance control device includes: Calculating the speed of the preceding vehicle based on the surrounding information; When the relative speed (rv), which is the speed of the preceding vehicle relative to the own vehicle, transitions from a state less than "0" (first state) to a state greater than "0" (second state) during execution of the deceleration control, and when it is detected based on the surrounding information that the light color of the nearest traffic light in the traveling direction of the own vehicle and the preceding vehicle is "red", The tracking control is interrupted, and An exceptional control that allows the vehicle distance to be increased beyond the target value, The acceleration of the vehicle The above A first exceptional control for controlling the drive device and the brake device so as to maintain them at a predetermined value; and a second exceptional control for controlling the drive device and the braking device so that the acceleration of the host vehicle gradually increases from the predetermined value; of Exception control, including the law of nature, When a predetermined first time has elapsed since the start of the first exception control, the first exception control is terminated and the second exception control is initiated, and when a predetermined second time has elapsed since the start of the second exception control, the second exception control is terminated. The first exception control and the second exception control cannot be executed from the time when the second exception control is ended until the host vehicle passes through the traffic light. It is structured as follows.

[0007] The driving support device according to the present invention configured as described above allows the inter-vehicle distance to increase from a target value when the preceding vehicle is traveling at a constant speed, when the preceding vehicle repeatedly decelerates and travels at a constant speed in front of a traffic light that is "red". That is, the driving support device does not make the speed of the host vehicle completely follow that of the preceding vehicle, but continues to gently decelerate the host vehicle. In this way, the behavior of the host vehicle is approximately consistent with the behavior expected by the driver (behavior expected when the traffic light is "red"). Furthermore, the change in acceleration of the host vehicle is gentler than the change in acceleration of the preceding vehicle in this case. Therefore, according to the present invention, the discomfort of the occupants of the host vehicle can be reduced compared to the conventional device (a device that always makes the speed of the host vehicle follow that of the preceding vehicle).

[0009] According to this, when the first state transitions to the second state, the change in the acceleration of the host vehicle is more gradual than when the second exception control is immediately executed without executing the first exception control, thereby reducing discomfort felt by the occupants of the host vehicle. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram of a driving assistance device according to an embodiment of the present invention. [Diagram 2] 2 is a plan view showing an area in which the driving assistance device can recognize the light color of a traffic signal. FIG. [Diagram 3] 4 is a graph showing an example of changes in acceleration and speed of a preceding vehicle and a host vehicle, as well as a vehicle-to-vehicle distance; [Figure 4] 4 is a flowchart of a follow-up control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Outline of configuration) As shown in FIG. 1, a driving assistance device 1 according to an embodiment of the present invention is mounted on a vehicle V. Based on information acquired from a sensor mounted on the vehicle V, the driving assistance device 1 controls the engine, brakes, and the like of the vehicle V so that the vehicle V travels at a constant speed or follows a vehicle VF (see FIG. 2) traveling immediately before the vehicle V, as will be described in detail later. Hereinafter, this control will be referred to as "cruise control." Furthermore, the vehicle V will be referred to as the "host vehicle," and the vehicle VF will be referred to as the "preceding vehicle."

[0012] (Specific configuration) As shown in FIG. 1, the driving assistance device 1 includes a driving assistance ECU 10, a drive device 20, a braking device 30, a shift switching device 40, a surrounding sensor 50, and an operation switch 60.

[0013] The driving assistance ECU 10 includes a microcomputer including a CPU 10a, a RAM 10b, a ROM 10c, etc. In this specification, "ECU" means an electronic control unit, and includes a microcomputer including a CPU, a RAM, a ROM, etc. The CPU realizes various functions by executing instructions stored in the ROM.

[0014] The driving assistance ECU 10 is connected to other ECUs (an engine ECU 21, a brake ECU 31, and a SBW·ECU 41, which will be described later) via a CAN (Controller Area Network) so as to be able to transmit and receive information to and from each other.

[0015] The drive device 20 generates a driving force and applies the driving force to driving wheels among the wheels (left front wheel, right front wheel, left rear wheel, and right rear wheel). The drive device 20 includes an engine ECU 21, an engine actuator 22, an internal combustion engine 23, a transmission 24, a driving force transmission mechanism (not shown) that transmits the driving force to the wheels, and the like. The engine ECU 21 is connected to the engine actuator 22. The engine actuator 22 includes a throttle valve actuator that changes the opening degree of a throttle valve of the internal combustion engine 23. The engine ECU 21 can change the torque generated by the internal combustion engine 23 by driving the engine actuator 22. The torque generated by the internal combustion engine 23 is transmitted to the driving wheels via the transmission 24 and the driving force transmission mechanism (for example, a drive shaft). As described above, the engine ECU 21 controls the driving force of the vehicle V by controlling the engine actuator 22.

[0016] In addition, when the vehicle V to which the driving assistance device 1 is applied is a hybrid vehicle (PHEV, HEV) or an electric vehicle (BEV), the engine ECU 21 can control the driving force of the vehicle generated by either or both of an "internal combustion engine and an electric motor" as the vehicle driving source.

[0017] The braking device 30 applies a braking force to the wheels. The braking device 30 includes a brake ECU 31, a hydraulic circuit 32, and a brake caliper 33. The hydraulic circuit 32 includes a reservoir, an oil pump, various valve devices, a hydraulic sensor, etc., which are not shown. The brake caliper 33 is a hydraulic actuator equipped with a cylinder and a piston. When oil is supplied to the cylinder, the piston is pushed out of the cylinder. A brake pad is provided at the tip of the piston, and this brake pad is pressed against a brake disc. The hydraulic circuit 32 adjusts the hydraulic pressure in the cylinder of the brake caliper 33 in response to a command from the brake ECU 31. In this way, the braking force of the brake caliper 33 on the wheels (brake disc) is controlled.

[0018] The shift switching device 40 switches the shift position of the transmission 24. The shift switching device 40 includes a Shift-by-Wire (SBW) ECU 41, an SBW actuator 42, and a shift switching mechanism 43. The SBW ECU 41 is connected to the SBW actuator 42. The SBW actuator 42 controls the shift switching mechanism 43 in response to a shift switching command from the SBW ECU 41 to switch the shift position of the transmission 24.

[0019] The surrounding sensor 50 is adapted to acquire vehicle surrounding information including information about three-dimensional objects present around the vehicle V and information about road markings around the vehicle V. The three-dimensional objects are, for example, moving objects such as automobiles (other vehicles), pedestrians, and bicycles, as well as fixed objects such as white lines on the road, guardrails, and traffic lights S.

[0020] The surrounding sensors 50 include a radar sensor 51 , an ultrasonic sensor 52 , a camera 53 , a vehicle speed sensor 54 and a navigation system 55 .

[0021] The radar sensor 51 includes a radar transmitting / receiving unit and a signal processing unit (not shown). The radar transmitting / receiving unit emits millimeter-wave band radio waves (hereinafter referred to as "millimeter waves") to the surrounding area of ​​the vehicle, and receives millimeter waves reflected by a three-dimensional object present within the emission range (i.e., reflected waves). The signal processing unit acquires information indicating the distance between the vehicle V and the three-dimensional object, the relative speed between the vehicle V and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the vehicle V, etc., based on the phase difference between the transmitted millimeter wave and the received reflected wave, the attenuation level of the reflected wave, the time from transmitting the millimeter wave to receiving the reflected wave, etc., and outputs the information to the driving assistance ECU 10.

[0022] The ultrasonic sensor 52 transmits ultrasonic waves in a pulsed manner to a predetermined area around the vehicle and receives the waves reflected by a three-dimensional object. The ultrasonic sensor can detect the "reflection point, which is the point on the three-dimensional object where the transmitted ultrasonic waves are reflected," and the "distance between the ultrasonic sensor and the three-dimensional object," based on the time from transmitting the ultrasonic waves to receiving the reflected waves.

[0023] The camera 53 includes an imaging device 531 and an image analysis device 532. The imaging device 531 is, for example, a digital camera incorporating an imaging element such as a charge coupled device (CCD) or a CMOS image sensor (CIS). The imaging device 531 is disposed on the upper part of the front windshield glass. The imaging device 531 outputs image data obtained by photographing the foreground of the vehicle at a predetermined frame rate to the image analysis device 532. The image analysis device 532 analyzes the acquired image data and acquires information on a target located in front of the vehicle V from the image. The image analysis device 532 acquires (recognizes), for example, the light color of a traffic light S located in front of the vehicle V in the traveling direction. Note that in order for the image analysis device 532 to accurately determine whether a group of pixels exhibiting a red circle in the image data is light emitted from a light unit of the traffic light S, the vehicle V needs to approach the traffic light S to a certain extent. When the vehicle V approaches the traffic light S and the distance reaches, for example, 120 m, the image analysis device 532 can accurately determine the light color of the traffic light S. In the following description, the maximum distance (the distance between the vehicle V and the traffic light S) at which the image analysis device 532 can accurately determine the light color of the traffic light S is referred to as the "recognizable distance Lr" (see FIG. 2). Also, a point located the recognizable distance Lr before the traffic light S is referred to as the "recognizable point Pr." Note that the recognizable distance Lr depends on the specifications of the imaging device 531. The recognizable distance Lr is experimentally determined during the development stage of the vehicle V, and the result is stored in the ROM 10c of the driving assistance ECU 10.

[0024] The vehicle speed sensor 54 includes a wheel speed sensor that generates one pulse signal (wheel pulse signal) every time the wheels of the vehicle rotate a predetermined angle. The vehicle speed sensor 54 measures the number of pulses per unit time of the wheel pulse signal transmitted from the wheel speed sensor, calculates the rotation speed (wheel speed) of each wheel based on the measured number of pulses, and calculates the speed of the vehicle (actual vehicle speed) based on the wheel speed of each wheel. The vehicle speed sensor 54 transmits data representing the calculation result to the driving assistance ECU 10.

[0025] The navigation system 55 receives GPS signals from multiple artificial satellites, and detects the current location (latitude and longitude) of the vehicle V based on the multiple received GPS signals. The navigation system 55 also stores map data representing a map. The map data includes road information representing roads and traffic light position information representing the installation positions of traffic lights. The navigation system 55 transmits vehicle position data representing the detected current location of the vehicle V to the driving assistance ECU 10. Furthermore, the navigation system 55 has a function of calculating the distance between two points (distance along the road). For example, the navigation system 55 calculates the distance from the current location of the vehicle to the first traffic light S (the nearest traffic light S) that the vehicle V will pass if it travels straight along the road on which it is currently traveling, and transmits the distance data to the driving assistance ECU 10.

[0026] The operation switch 60 is an operator (e.g., a push button switch operator) that is operated when the driver requests the start and end of cruise control. When the driver operates the operation switch 60 (presses the button) while cruise control is not being executed, the operation switch 60 transmits a cruise control start signal to the driving assistance ECU 10, which indicates that "the driver is requesting the start of cruise control (a request to start cruise control)". On the other hand, when the driver operates the operation switch 60 while cruise control is being executed, the operation switch 60 transmits a cruise control end signal to the driving assistance ECU 10, which indicates that "the driver is requesting the end of cruise control (a request to end cruise control)".

[0027] The operation switch 60 also includes an operator for designating a target value Vd of the vehicle speed during constant speed cruise control, which will be described later.

[0028] (Activation) Next, the cruise control executed by the driving support device 1 will be described. The cruise control includes constant speed traveling control and follow-up control. The constant speed traveling control is not directly related to the present invention. Therefore, the constant speed traveling control will be merely briefly described, and the follow-up control will be described in detail.

[0029] The driving assistance ECU 10 starts the cruise control (ACC) when it receives a cruise control start signal from the operation switch 60. When the driving assistance ECU 10 starts the cruise control, the driving assistance ECU 10 sequentially determines whether or not there is another vehicle (a preceding vehicle) to be followed, based on information acquired from the surroundings sensor 50.

[0030] <Constant speed control> When it is determined that there is no preceding vehicle to be followed, the driving assistance ECU 10 controls the drive device and the like so that the speed of the host vehicle coincides with a preset target value Vd.

[0031] <Tracking control> On the other hand, when it is determined that there is a preceding vehicle to be followed, the driving assistance ECU 10 detects (actually measures) the inter-vehicle distance L between the preceding vehicle and the vehicle itself based on the vehicle surroundings information acquired from the surroundings sensor 50. Furthermore, the driving assistance ECU 10 calculates the vehicle speed and acceleration of the preceding vehicle based on the speed of the vehicle itself, changes in the inter-vehicle distance L, and the like. Furthermore, the driving assistance ECU 10 calculates the acceleration of the vehicle itself based on changes in the speed of the vehicle itself. Note that an acceleration sensor may be provided as the surroundings sensor 50. In that case, the driving assistance ECU 10 acquires the acceleration of the vehicle itself from the acceleration sensor. Furthermore, the driving assistance ECU 10 calculates a target value Ld of the inter-vehicle distance L based on the speed of the vehicle itself, the speed of the preceding vehicle, and the like.

[0032] When the speed of the preceding vehicle relative to the speed of the vehicle is greater than "0", the inter-vehicle distance L increases. When the inter-vehicle distance L is greater than the target value Ld, the driving assistance ECU 10 sets a target acceleration of the vehicle so that the speed of the vehicle becomes greater than the speed of the preceding vehicle. Then, the driving assistance ECU 10 controls the drive device 20, the braking device 30, and the shift switching device 40 (hereinafter referred to as "drive devices, etc.") so that the acceleration of the vehicle coincides with the target acceleration (hereinafter referred to as "acceleration control"). As a result, the inter-vehicle distance L, which has increased from the target value Ld, begins to return to the target value Ld. Then, when the inter-vehicle distance L coincides with the target value Ld, the driving assistance ECU 10 sets the target acceleration of the vehicle to "0". That is, the driving assistance ECU 10 controls the drive device, etc. so that the vehicle travels at the same speed as the preceding vehicle.

[0033] On the other hand, when the speed of the preceding vehicle relative to the speed of the vehicle is smaller than "0", the vehicle distance L decreases. When the vehicle distance L decreases below the target value Ld, the driving assistance ECU 10 sets a target acceleration of the vehicle so that the speed of the vehicle becomes smaller than the speed of the preceding vehicle. Then, the driving assistance ECU 10 controls the drive device, etc. so that the acceleration of the vehicle coincides with the target acceleration (hereinafter referred to as "deceleration control"). As a result, the vehicle distance L, which has decreased from the target value Ld, begins to return to the target value Ld. Then, when the vehicle distance L coincides with the target value Ld, the driving assistance ECU 10 sets the acceleration of the vehicle to "0". The target value Ld is correlated with the speed of the vehicle and the speed of the preceding vehicle. A database (table) showing the relationship between these speeds and the target value Ld or parameters that specify an arithmetic expression that determines the target value Ld are stored in the ROM 10c. According to this database or formula, a relatively small target value Ld is assigned to a relatively small speed, and a relatively large target value Ld is assigned to a relatively large speed.

[0034] As described above, the tracking control is a control (hereinafter, sometimes referred to as "normal control") that sets the target acceleration so that the inter-vehicle distance L coincides with the target value Ld. However, when the driving assistance ECU 10 determines that the exceptional control start condition described below is satisfied, it interrupts the normal control (deceleration control) and executes the exceptional control (first exceptional control and second exceptional control) described below. The exceptional control start condition consists of the following (Condition 1) to (Condition 3). (Condition 1) Deceleration control is being executed (target acceleration is less than "0"). (Condition 2) The speed of the preceding vehicle relative to the speed of the host vehicle (relative speed rv) has transitioned from a state in which it is less than "0" (hereinafter referred to as the "first state") to a state in which it is greater than or equal to "0" (hereinafter referred to as the "second state"). (Condition 3) The light color of the nearest traffic light S in the direction of travel of the vehicle and the preceding vehicle is “red”.

[0035] When the above-mentioned exception control start condition is satisfied, the driving assistance ECU 10 interrupts the normal control (deceleration control) and starts the first exception control. That is, the driving assistance ECU 10 controls the drive device and the like so that the acceleration of the host vehicle does not change. That is, when (Condition 1) to (Condition 3) are satisfied, the driving assistance ECU 10 allows the inter-vehicle distance L to increase from the target value Ld. When a predetermined time tx has elapsed since the start of the first exception control, the driving assistance ECU 10 ends the first exception control and starts the second exception control. That is, the driving assistance ECU 10 increases the acceleration of the host vehicle at a constant rate of change. Then, when a predetermined time ty has elapsed since the start of the second exception control, the driving assistance ECU 10 ends the second exception control and resumes the normal control.

[0036] However, if the preceding vehicle suddenly decelerates while the exception control is being executed and the inter-vehicle distance L becomes smaller than the target value Ld, the driving assistance ECU 10 immediately ends the exception control and resumes normal control.

[0037] In this embodiment, the driving assistance ECU 10 can execute the above-mentioned exception control only once in a predetermined area R (between the recognizable point Pr and the traffic light S) where the host vehicle approaches the traffic light S. In other words, even if the above-mentioned exception control start condition is satisfied again in the area R after the driving assistance ECU 10 executes the exception control once in the area R (including the case where the exception control is stopped midway), the driving assistance ECU 10 does not execute the exception control. Alternatively, the driving assistance ECU 10 may interrupt the normal control and execute the exception control every time the exception control start condition is satisfied in the area R.

[0038] As a situation in which the exceptional control start condition is satisfied, for example, when the road surface is horizontal just before traffic light S, the braking force of the preceding vehicle is suddenly weakened from a relatively strong state. In this example, the speed of the preceding vehicle relative to the speed of the host vehicle becomes greater than "0", and the inter-vehicle distance L increases. In this situation, if the light color of the nearest traffic light S is "red", the driving assistance ECU 10 maintains or gradually weakens the braking force of the host vehicle, rather than suddenly weakening the braking force of the host vehicle in response to the preceding vehicle. In other words, the driving assistance ECU 10 allows the inter-vehicle distance L to increase.

[0039] For example, when the acceleration and speed of the preceding vehicle change within the region R as shown by the dashed lines in Fig. 3(A) and Fig. 3(B), the driving assistance ECU 10 changes the acceleration of the host vehicle as shown by the solid line in Fig. 3(A). As a result, the speed of the host vehicle changes as shown in Fig. 3(B). The inter-vehicle distance L also changes as shown in Fig. 3(C). The operation of the driving assistance ECU 10 at this time will be specifically described below.

[0040] Here, the driving assistance ECU 10 repeatedly determines whether or not the exceptional control start condition is satisfied within the region R. The driving assistance ECU 10 executes normal control or exceptional control according to the determination result. In the following description, the timing at which the driving assistance ECU 10 executes normal control or exceptional control (the timing at which the target acceleration is updated) is referred to as "control timing T."

[0041] Specifically, when the acceleration of the host vehicle is less than "0", the driving assistance ECU 10 determines that "Condition 1 is satisfied". On the other hand, when the acceleration of the host vehicle is equal to or greater than "0", the driving assistance ECU 10 determines that "Condition 1 is not satisfied".

[0042] Furthermore, at each control timing T, the driving assistance ECU 10 judges whether or not (Condition 2) is satisfied as described below. That is, if the relative speed rv at the previous control timing T is smaller than "0" and the relative speed rv at the current control timing T is equal to or greater than "0", the driving assistance ECU 10 judges that "(Condition 2) is satisfied". On the other hand, for example, if both the relative speeds rv at the previous and current control timings T are greater than "0" or smaller than "0", the driving assistance ECU 10 judges that "(Condition 2) is not satisfied". Also, for example, if the relative speed rv at the previous control timing T is greater than "0" and the relative speed rv at the current control timing T is equal to or less than "0", the driving assistance ECU 10 judges that "(Condition 2) is not satisfied".

[0043] Furthermore, when the driving assistance ECU 10 analyzes the image data acquired from the camera 53 and recognizes that the light color of the nearest traffic light S is "red," it determines that "(Condition 3) is met." On the other hand, when the driving assistance ECU 10 recognizes that the light color of the recognized traffic light S is "yellow" or "green," it determines that "(Condition 3) is not met." It is assumed that "(Condition 3) is met" throughout the entire period of this example. In other words, the driving assistance ECU 10 recognizes that the light color of the nearest traffic light S is "red."

[0044] Note that the time it takes for the acceleration of the host vehicle to match the target acceleration after the driving assistance ECU 10 updates (sets) the target acceleration is very short. Therefore, when the driving assistance ECU 10 sets the target acceleration at the control timing T, the acceleration of the host vehicle matches the target acceleration before the next control timing T.

[0045] <Behavior of preceding vehicle> Next, with reference to FIG. 3, the behavior (changes in acceleration and speed) of the leading vehicle in the example of the figure will be described. In a first period from time t0 to time t1, the braking force of the leading vehicle is strengthened. Specifically, in the early part of the first period, the acceleration of the leading vehicle suddenly drops from "0" at a substantially constant rate of change, and the speed of the leading vehicle also suddenly drops. Then, from the middle of the first period, the braking force of the leading vehicle is gradually weakened. That is, from the middle of the first period, the rate of change of the acceleration of the leading vehicle starts to become smaller, and eventually the rate of change becomes "0". Then, at the end of the first period, the acceleration of the leading vehicle is substantially constant. That is, at the end of the first period, the speed of the leading vehicle decreases a little more gently than before (the early and middle parts of the first period).

[0046] In the second period from time t1 to time t2, the braking force of the leading vehicle is suddenly weakened. That is, in the second period, the acceleration of the leading vehicle suddenly increases toward "0". That is, at the end of the second period, the speed of the leading vehicle hardly changes at all.

[0047] In a third period from time t2 to time t3, the acceleration of the leading vehicle is maintained at approximately “0.” That is, in the third period, the leading vehicle travels at a substantially constant speed.

[0048] In the fourth period from time t3 to time t4, the braking force of the leading vehicle is increased, as in the first period. Specifically, in the early stage of the fourth period, the acceleration of the leading vehicle decreases from "0" at a substantially constant rate of change. Next, from the middle of the fourth period, the braking force of the leading vehicle is gradually weakened. That is, the rate of change of the acceleration of the leading vehicle starts to decrease, and eventually the rate of change becomes "0". Then, at the end of the fourth period, the acceleration of the leading vehicle is substantially constant. The speed of the leading vehicle decreases gradually in the early stage of the fourth period, and decreases rapidly in the middle stage. Then, at the end of the fourth period, it decreases relatively gradually. Note that, at the end of the fourth period, the leading vehicle is quite close to the traffic light S and is traveling at a fairly low speed.

[0049] In the fifth period from time t4 to time t5, the braking force of the leading vehicle is weakened. That is, in the beginning of the fifth period, the acceleration of the leading vehicle increases rapidly toward "0". Then, in the end of the fifth period, the acceleration of the leading vehicle becomes "0". In this way, the speed of the leading vehicle becomes "0". That is, the leading vehicle stops slightly before traffic light S.

[0050] <Operation of driving assistance ECU 10> Next, the operation of the driving assistance ECU 10 will be described with reference to Fig. 3. As described above, (Condition 3) is satisfied throughout the entire period of this example. Therefore, hereinafter, it will be described whether (Condition 1) and (Condition 2) are satisfied at each control timing T.

[0051] At time t0, the host vehicle is traveling at a speed slightly slower than the preceding vehicle. At time t0 (control timing T0), the acceleration of the host vehicle is "0". That is, at control timing T0, (condition 1) is not satisfied. At control timing T0, the relative speed rv is greater than "0". At control timing T, which is one control timing before the control timing T0, the relative speed rv is also greater than "0". That is, at control timing T0, (condition 2) is not satisfied. That is, at control timing T0, the exceptional control start condition is not satisfied. Therefore, at control timing T0, the driving assistance ECU 10 executes normal control. At control timing T0, the relative speed rv is relatively small, and the inter-vehicle distance L tends not to change much (the rate of change of the inter-vehicle distance L is small). Also, the inter-vehicle distance L is approximately equal to the target value Ld. Therefore, at this control timing T0, the driving assistance ECU 10 hardly changes the target acceleration of the host vehicle. Note that the target value Ld is not shown in FIG. 3.

[0052] In this example, at the control timing T following the control timing T0, (Condition 2) is not satisfied. Therefore, the driving assistance ECU 10 also executes normal control at the control timing T. The driving assistance ECU 10 also executes normal control at each control timing T in the time period before the subsequent time ta (control timing Ta). As a result, during this time period, the acceleration and speed of the host vehicle are gradually decreasing. Meanwhile, during this time period, the preceding vehicle has begun to decelerate. Then, at the time ta (control timing Ta), the speed of the preceding vehicle and the speed of the host vehicle match.

[0053] At the control timing Ta, the acceleration of the host vehicle is slightly smaller than "0". That is, at the control timing Ta, (Condition 1) is satisfied. On the other hand, at the control timing Ta, the relative speed rv is "0", but at the control timing T immediately preceding the control timing Ta, the relative speed rv is greater than "0". That is, at the control timing Ta, (Condition 2) is not satisfied. Therefore, the driving assistance ECU 10 also executes normal control at the control timing Ta. At the control timing Ta, the inter-vehicle distance L is slightly smaller than the target value Ld. Therefore, at the control timing Ta, the driving assistance ECU 10 slightly reduces the target acceleration. As a result, the speed of the host vehicle begins to decrease. Note that at the time ta, the speed of the preceding vehicle tends to decrease more rapidly than that of the host vehicle.

[0054] At the control timing T following the control timing Ta, (Condition 1) is satisfied, but (Condition 2) is not satisfied. Therefore, the driving assistance ECU 10 also executes normal control at the control timing T. At each control timing T in the subsequent time period before time t1 (control timing T1), the driving assistance ECU 10 also executes normal control, as at the control timing Ta. As a result, the acceleration and speed of the host vehicle decrease during this time period.

[0055] At control timing T1, the acceleration of the host vehicle is less than "0". That is, at control timing T1, (condition 1) is satisfied. On the other hand, at control timing T1, the relative speed rv is less than "0", and at the control timing T immediately preceding control timing T1, the relative speed rv is also less than "0". That is, (condition 2) is not satisfied at control timing T1. Therefore, the driving assistance ECU 10 executes normal control at control timing T1. At control timing T1, the inter-vehicle distance L is less than the target value Ld. Therefore, at control timing T1, the driving assistance ECU 10 further reduces the target acceleration. As a result, the acceleration and speed of the host vehicle are further reduced.

[0056] At the control timing T following the control timing T1, (Condition 1) is satisfied, but (Condition 2) is not satisfied. Therefore, the driving assistance ECU 10 also executes normal control at the control timing T. At each control timing T in the subsequent time period before time t2 (control timing T2), the driving assistance ECU 10 also executes normal control, as in the case of control timing T1. As a result, the acceleration and speed of the host vehicle decrease during this time period. "0000" The exceptional control start condition is not satisfied at control timing T2 or at each subsequent control timing T (control timing T before time tb). Therefore, the driving assistance ECU 10 executes normal control. This causes the acceleration and speed of the host vehicle to decrease further. Meanwhile, as described above, at time t2, the rate of change in the speed of the preceding vehicle is approximately "0". Therefore, at time tb (control timing Tb) after time t2, the speed of the host vehicle matches the speed of the preceding vehicle.

[0057] At the control timing Tb, the acceleration of the host vehicle is less than "0". That is, (Condition 1) is satisfied at the control timing Tb. On the other hand, at the control timing Tb, the relative speed rv is "0", and at the control timing T immediately preceding the control timing Tb, the relative speed rv is less than "0". That is, (Condition 2) is satisfied at the control timing Tb. Also, as described above, (Condition 3) is satisfied at the control timing Tb. Therefore, the driving assistance ECU 10 interrupts normal control at the control timing Tb and starts exceptional control.

[0058] That is, the driving assistance ECU 10 executes the first exception control in a period A from time tb to the following time tc. That is, the driving assistance ECU 10 keeps the acceleration of the host vehicle constant in the period A. Specifically, at each control timing T in the period A, the driving assistance ECU 10 sets the target acceleration to the same value as the target acceleration set at the control timing T immediately preceding the control timing Tb. Note that the time tx from time tb to time tc is specified in advance.

[0059] Next, the driving assistance ECU 10 executes the second exception control in a period B from time tc, which is the end of the period A, to the following time td. That is, the driving assistance ECU 10 gradually increases the acceleration of the host vehicle at a constant rate of change α in the period B. Specifically, at each control timing in the period B, the driving assistance ECU 10 adopts a value obtained by adding a predetermined value to the target acceleration at the previous control timing T as a new target acceleration. Note that the time ty from time tc to time td is specified in advance. The driving assistance ECU 10 ends the exception control when the time ty has elapsed since starting the second exception control. Note that in this example, the driving assistance ECU 10 ends the exception control in the middle of the third period.

[0060] Since the rate of change α is relatively small and the time ty is relatively short, the acceleration of the host vehicle does not reach "0" while the second exception control is being executed. However, for example, if the time during which the preceding vehicle travels at a constant speed (the time during which the acceleration is "0") is relatively long, the acceleration of the host vehicle may reach "0" while the driving assistance ECU 10 is executing the second control. In this case, the driving assistance ECU 10 keeps the target acceleration of the host vehicle at "0" at the control timing T thereafter.

[0061] As described above, the driving assistance ECU 10 continues to decelerate the host vehicle rather than causing the host vehicle to follow the leading vehicle during the periods A and B. That is, the vehicle-to-vehicle distance L is allowed to increase during these periods.

[0062] After the driving assistance ECU 10 ends the above-mentioned exceptional control, it does not execute the exceptional control even if the exceptional control start condition is satisfied again within the same region R. That is, in this case, the driving assistance ECU 10 executes the normal control.

[0063] The driving assistance ECU 10 resumes normal control from time td (control timing Td) when the exceptional control ends. At the control timing Td, the inter-vehicle distance L is larger than the target value Ld. Therefore, the driving assistance ECU 10 sets the target acceleration of the host vehicle so that the inter-vehicle distance L is reduced. Note that at the control timing Td, the preceding vehicle is traveling at a slower speed than the host vehicle. Therefore, it is not necessary to suddenly decelerate the host vehicle, and the inter-vehicle distance L will decrease if the host vehicle is decelerated gradually. Therefore, the driving assistance ECU 10 gradually reduces the target acceleration at the control timing Td and subsequent control timings.

[0064] At time te (control timing Te) after time td, the host vehicle is approaching the traffic light S quite closely. The host vehicle is also traveling at a fairly slow speed. From the control timing Te, the driving assistance ECU 10 gradually increases the target acceleration of the host vehicle toward "0". This causes the speed of the host vehicle to decrease gradually. Then, the host vehicle stops behind the preceding vehicle that has stopped in front of the traffic light S.

[0065] In the example shown in the figure, the inter-vehicle distance L tends to increase from the start to the end of the exceptional control. Therefore, the exceptional control is not stopped. In contrast, if the preceding vehicle suddenly decelerates while the exceptional control is being executed and the inter-vehicle distance L starts to decrease, the driving assistance ECU 10 immediately stops the exceptional control and executes the normal control.

[0066] Next, with reference to FIG. 4, the operation of the CPU 10a (hereinafter simply referred to as "CPU") of the driving assistance ECU 10 (the tracking program that realizes the above-mentioned tracking control) will be specifically described.

[0067] As described above, the CPU successively determines whether or not there is another vehicle (preceding vehicle) to be followed, based on the information acquired from the surrounding sensor 50. When the CPU determines that there is a preceding vehicle to be followed, it starts the following process from step 100 and proceeds to step 101.

[0068] When the CPU proceeds to step 101, it determines whether or not the host vehicle has entered area R based on the information acquired from the navigation system 55. That is, the CPU successively acquires information indicating the position of the host vehicle from the navigation system 55, and determines that the host vehicle has entered area R if the previously acquired position was outside area R and the currently acquired position is inside area R (including the boundary). If the CPU determines that "the host vehicle has entered area R" (101: Yes), it proceeds to step 102. On the other hand, if the CPU determines that "the host vehicle has not entered area R" (i.e., the host vehicle is traveling outside area R (101; No)), it proceeds to step 110.

[0069] When the CPU proceeds to step 102, it initializes the value of exception control flag F to "1". Here, exception control flag F is a flag that indicates whether or not exception control can be executed within region R. That is, when the value of exception control flag F is "1", the execution of exception control is permitted. On the other hand, when the value of exception control flag F is "0", the execution of exception control is prohibited. As described above, in step 102, the CPU sets the value of exception control flag F to "1". That is, the CPU becomes capable of executing exception control.

[0070] Next, the CPU determines whether or not the exception control start condition is satisfied in step 103. If the exception control start condition is satisfied (103: Yes), the CPU proceeds to step 104. On the other hand, if any one or more of the three conditions constituting the exception control start condition are not satisfied (103: No), the CPU proceeds to step 110.

[0071] When the CPU proceeds to step 104, it determines whether or not the value of the exception control flag F is "1." If the value of the exception control flag F is "1" (104: Yes), the CPU proceeds to step 105. On the other hand, if the value of the exception control flag F is not "1" (if the value is "0" (104: No)), the CPU proceeds to step 110.

[0072] When the CPU proceeds to step 105, it sets the value of the exception control flag F to “0.” Then, the CPU proceeds to step .

[0073] When the CPU proceeds to step 106, it executes the first exception control. That is, the CPU does not change the target acceleration of the host vehicle. Next, in step 107, the CPU determines whether the duration of the first exception control (the elapsed time t from the start of the first exception control) has exceeded a predetermined time tx. If the elapsed time t has not yet exceeded the time tx (107: No), the CPU returns to step 106. On the other hand, if the elapsed time t has exceeded the time tx (107: Yes), the CPU proceeds to step 108.

[0074] When the CPU proceeds to step 108, it executes the second exception control. That is, the CPU adds a predetermined value to the current value of the target acceleration of the host vehicle. Next, in step 109, the CPU determines whether the duration of the second exception control (the elapsed time t from the start of the second exception control) has exceeded a predetermined time ty. If the elapsed time t has not yet exceeded time ty (109: No), the CPU returns to step 108. On the other hand, if the elapsed time t has exceeded time ty (109: Yes), the CPU proceeds to step 110.

[0075] When the CPU proceeds to step 110, it executes normal control. That is, the CPU updates the target acceleration of the host vehicle so that the inter-vehicle distance L matches a predetermined value. Then, in step 111, the CPU determines whether the host vehicle has left area R. If the host vehicle has left area R (111: Yes), the CPU returns to step 101. On the other hand, if the host vehicle is located within area R (111: No), the CPU returns to step 103.

[0076] During execution of steps 106 to 109 (during execution of exception control), the CPU monitors changes in the inter-vehicle distance L. When the inter-vehicle distance L starts to decrease, the CPU stops execution of the exception control and proceeds to step 110.

[0077] (effect) As described above, when the light color of the traffic light S is "red" and the preceding vehicle repeats deceleration and constant speed driving before the traffic light S, the driving support device 1 according to this embodiment allows the inter-vehicle distance L to increase from the target value Ld determined in the normal control when the preceding vehicle is driving at a constant speed. That is, the driving support device 1 does not make the speed of the host vehicle completely follow the speed of the preceding vehicle, but continues to gently decelerate the host vehicle. In this way, the behavior of the host vehicle is approximately consistent with the behavior expected by the driver (behavior expected when the light color of the traffic light S is "red"). In addition, the change in acceleration of the host vehicle is gentler than the change in acceleration of the preceding vehicle in this case. Therefore, according to the present invention, the discomfort of the occupants of the host vehicle can be reduced compared to the conventional device (a device that always makes the speed of the host vehicle follow the speed of the preceding vehicle).

[0078] The present invention is not limited to the above-described embodiment, and various modifications can be adopted within the scope of the present invention, as described below.

[0079] <Variation 1> In the above embodiment, when the state transitions from the first state to the second state, the first exception control is executed and then the second exception control is executed. Alternatively, when the state transitions from the first state to the second state, the second exception control may be executed without executing the first exception control.

[0080] <Variation 2> In the above embodiment, the driving assistance ECU 10 determines whether the light color of the traffic light S is "red" based on image data obtained from the camera 53, but may also obtain information regarding the light color of the traffic light S from a server via a communication device. [Explanation of symbols]

[0081] 1...driving assistance device, 10...driving assistance ECU, 20...driving device, 30...braking device, 40...shift switching device, 50...surrounding sensor, 60...operation switch, A, B...period, F...exception control flag, L...inter-vehicle distance, Ld...target value, R...area, S...traffic signal, T...control timing, rv...relative speed

Claims

[Claim 1] A drive device that applies a drive force to drive wheels of the host vehicle; A braking device that applies a braking force to the drive wheels; A surroundings sensor that outputs surrounding information that is information about targets around the host vehicle; a driving assistance control device that determines a target value of an inter-vehicle distance between the host vehicle and a preceding vehicle traveling immediately in front of the host vehicle based on the peripheral information, and executes a following control to control the drive device and the braking device so that an actual measured value of the inter-vehicle distance obtained based on the peripheral information coincides with the target value; Equipped with the following control includes a deceleration control for controlling the drive device and the front braking device to decelerate the host vehicle so that the acceleration of the host vehicle coincides with a predetermined value smaller than "0" when the preceding vehicle decelerates and the vehicle-to-vehicle distance becomes shorter than the target value, thereby bringing the shortened vehicle-to-vehicle distance closer to the target value; The driving assistance control device includes: Calculating the speed of the preceding vehicle based on the surrounding information; When the relative speed of the preceding vehicle relative to the host vehicle changes from a state smaller than "0" to a state larger than "0" during the execution of the deceleration control, and when it is detected based on the surrounding information that the light color of the nearest traffic light in the traveling direction of the host vehicle and the preceding vehicle is "red", The tracking control is interrupted, and An exceptional control that allows the vehicle distance to be increased beyond the target value, A first exceptional control for controlling the drive device and the braking device so that the acceleration of the host vehicle is maintained at the predetermined value; and a second exceptional control for controlling the drive device and the braking device so that the acceleration of the host vehicle gradually increases from the predetermined value; It is possible to perform exception control, including When a predetermined first time has elapsed since the start of the first exception control, the first exception control is terminated and the second exception control is started; when a predetermined second time has elapsed since the start of the second exception control, the second exception control is terminated; and from the point in time when the second exception control is terminated until the host vehicle passes through the traffic light, the first exception control and the second exception control cannot be executed. Driving assistance device.

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