Driving assistance devices

Abstract

To provide an operation support device capable of curbing a delay in arrival time at a destination while keeping fuel consumption low.SOLUTION: An operation support device comprises: an on-vehicle sensor which acquires and outputs information on a position of an own vehicle, information on an object positioned around the own vehicle and information on operation of an operation section of an own vehicle; and a control device which controls at least one of a drive device, a brake device and a steering device of the own vehicle so as to detect existence of a preceding vehicle traveling immediately ahead of the own vehicle, determine the preceding vehicle as a following object vehicle, and cause the own vehicle to follow the following object vehicle. The following object vehicle is changed from a vehicle V0 to a vehicle V1 when the own vehicle is following the vehicle V0 as the following object vehicle with a speed of either the own vehicle or the vehicle V0 equal to or less than a first threshold and when it is detected that the own vehicle can follow the vehicle V1 traveling in a traffic lane Lb neighboring a traffic lane La of the own vehicle at a speed higher than the own vehicle.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention relates to a driving assistance device that controls the drive device, braking device, etc. of a vehicle so that the vehicle follows a preceding vehicle. [Background technology]

[0002] Conventionally, there is known a driving assistance device (hereinafter referred to as a "conventional device") that controls the drive device, braking device, etc. of a host vehicle so that the host vehicle follows a preceding vehicle (a vehicle traveling immediately in front of the host vehicle) (see, for example, Patent Document 1 below). This conventional device controls the drive device and braking device so that the distance between the host vehicle and the preceding vehicle matches a predetermined value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-520173 Summary of the Invention

[0004] Generally, a vehicle's fuel consumption rate (fuel economy) correlates with its speed. For example, within a vehicle speed range of 80 km / h or less, the higher the vehicle speed, the lower the fuel consumption rate. However, within a vehicle speed range of over 80 km / h, the lower the vehicle speed, the lower the fuel consumption rate. Furthermore, when there is a preceding vehicle, the air resistance value is smaller than when there is no preceding vehicle, and the fuel consumption rate is lower. However, if the speed of the preceding vehicle is significantly slow, it will take a relatively long time to arrive at the destination.

[0005] An object of the present invention is to provide a driving assistance device that can suppress delays in arrival at a destination while keeping fuel consumption low.

[0006] In order to solve the above problems, the driving assistance device (1) of the present invention comprises: an on-board sensor (20) that acquires and outputs information relating to the position of the vehicle, information relating to targets located around the vehicle, and information relating to the operation of an operating unit of the vehicle; a control device (10) that detects the presence of a preceding vehicle traveling just ahead of the host vehicle based on information acquired from the on-board sensor, determines the preceding vehicle as a vehicle to be followed, and controls at least one of a drive device (30), a braking device (40), and a steering device (60) of the host vehicle so that the host vehicle follows the vehicle to be followed; Equipped with. The control device When the host vehicle is following a first vehicle as the following target vehicle and the speed of the host vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, a vehicle adjacent to the first lane in which the host vehicle is traveling is detected based on information acquired from the on-board sensor. Among vehicles traveling in the second lane and approaching your vehicle from behind, A second vehicle traveling at a higher speed than the vehicle in question and searching for a third vehicle traveling immediately behind the second vehicle, and if the distance between the second vehicle and the third vehicle exceeds a threshold and the speed of the second vehicle is faster than the speed of the third vehicle, If your vehicle can follow the second vehicle, Judging, The vehicle to be followed is changed from the first vehicle to the second vehicle. The control device When the host vehicle is following a first vehicle as the vehicle to be followed and the speed of the host vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, the system may be configured to search, based on information acquired from the on-board sensor, for a second vehicle traveling in a second lane adjacent to the first lane in which the host vehicle is traveling and approaching the host vehicle from behind, the second vehicle traveling at a higher speed than the host vehicle, and a third vehicle traveling immediately behind the second vehicle, and predict the time required for the third vehicle to catch up with the host vehicle based on the distance between the host vehicle and the third vehicle, the speed of the host vehicle, and the speed of the third vehicle, and if the time obtained by adding a predetermined margin to the predicted time exceeds a threshold, determine that the host vehicle can follow the second vehicle and change the vehicle to be followed from the first vehicle to the second vehicle.

[0007] According to the driving assistance device of the present invention, when the host vehicle is following a first vehicle and the first vehicle is traveling at an extremely slow speed, the control device can change the vehicle to be followed from the first vehicle to a second vehicle traveling in an adjacent lane. The host vehicle can then follow the second vehicle and overtake the first vehicle. In this case, since the host vehicle is following the second vehicle (traveling immediately behind the second vehicle), the air resistance value during overtaking is smaller than when the host vehicle is traveling alone. This allows fuel consumption to be kept low. Furthermore, by overtaking the first vehicle, the host vehicle can travel at a higher speed than the first vehicle, thereby reducing fuel consumption and delaying arrival time at the destination. Furthermore, safety can be improved when the host vehicle overtakes the first vehicle, which is the original vehicle to be followed (when the host vehicle changes its traveling lane from the first lane to the second lane).

[0008] In one aspect of the present invention, there is provided a driving assistance device, The control device When the difference (Δv) between the speed of the host vehicle and the speed of the second vehicle while the host vehicle is traveling in the first lane is less than a predetermined second threshold (Δvth), the vehicle to be followed can be changed from the first vehicle to the second vehicle.

[0009] If the second vehicle is traveling at an extremely high speed, it is difficult for the host vehicle to change lanes from the first lane to the second lane and follow the second vehicle. According to the present invention, it is possible to prevent the host vehicle from determining (adopting) such a second vehicle traveling at a high speed as a vehicle to be followed.

[0010] In a driving assistance device according to another aspect of the present invention, The control device After the second vehicle follows the second vehicle and overtakes the first vehicle, if the speed of the second vehicle traveling in the second lane exceeds the first threshold and there is an area in the first lane in which the vehicle can travel, the drive device, braking device, and steering device are controlled so that the vehicle moves from the second lane to the first lane.

[0011] According to this, if the host vehicle becomes unable to keep up with the second vehicle after overtaking the first vehicle, the host vehicle can be made to travel faster than the first vehicle in an area ahead of the first vehicle, thereby keeping fuel consumption low and minimizing delays in arrival time at the target value. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a block diagram of a driving assistance device according to an embodiment of the present invention. [Figure 2A] FIG. 2A is a plan view showing a state before the host vehicle overtakes the leading vehicle. [Figure 2B] FIG. 2B is a plan view showing a state in which the adjacent vehicle has changed lanes after the host vehicle has overtaken the leading vehicle. [Figure 2C]FIG. 2C is a plan view showing a state in which the host vehicle changes lanes after overtaking the leading vehicle and then being unable to follow the adjacent vehicle. [Figure 3] Figure 3 is a flowchart of the ACC program. [Figure 4] Figure 4 is a flowchart of the overtaking program. [Figure 5] FIG. 5 is a flowchart of an overtaking program according to a modified example of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] (Outline of configuration) As shown in FIG. 1, a driving assistance device 1 according to one embodiment of the present invention is mounted on a vehicle V. Based on information acquired from sensors 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 traveling immediately in front of the vehicle V, as will be described in detail later. Hereinafter, this control will be referred to as "cruise control." In the following description, the vehicle V will be referred to as the "host vehicle." Furthermore, a vehicle traveling immediately in front of the vehicle V will be referred to as the "preceding vehicle." Furthermore, a vehicle traveling in a lane adjacent to the lane in which the vehicle V is traveling will be referred to as the "adjacent vehicle."

[0016] (Specific configuration) As shown in FIG. 1, the driving assistance device 1 includes a driving assistance ECU 10, an on-board sensor 20, a drive device 30, a braking device 40, a shift switching device 50, and a steering device 60.

[0017] The driving assistance ECU 10 includes a microcomputer including a CPU 10a, a ROM 10b, a RAM 10c, a timer 10d, etc. In this specification, "ECU" means an electronic control unit, and includes a microcomputer including a CPU, RAM, ROM, etc. The CPU realizes various functions by executing instructions stored in the ROM.

[0018] The driving assistance ECU 10 is connected to other ECUs (an engine ECU 31, a brake ECU 41, a SBW·ECU 51, and an EPS·ECU 61, 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.

[0019] The on-board sensor 20 includes a sensor that acquires vehicle surrounding information including information about three-dimensional objects present around the vehicle V and information about road markings on the road surface around the vehicle V. That is, for example, the on-board sensor 20 includes a sensor that acquires information about moving objects such as automobiles (other vehicles), pedestrians, and bicycles, as well as fixed objects such as white lines on the road surface, guardrails, and traffic lights.

[0020] Specifically, the on-board sensors 20 include a radar sensor 21, an ultrasonic sensor 22, a camera 23, and a navigation system 24.

[0021] The radar sensor 21 includes a radar transmitter / receiver and a signal processor (not shown). The radar transmitter / receiver emits millimeter-wave band radio waves (hereinafter referred to as "millimeter waves") to the area surrounding the vehicle and receives millimeter waves reflected by a three-dimensional object present within the emission range (i.e., reflected waves). The signal processor 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 waves and the received reflected waves, the attenuation level of the reflected waves, the time from transmitting the millimeter waves to receiving the reflected waves, etc., and transmits the information to the driving assistance ECU 10.

[0022] The ultrasonic sensor 22 transmits ultrasonic waves in pulses within a predetermined range around the vehicle and receives the waves reflected by a three-dimensional object. Based on the time from transmitting the ultrasonic waves to receiving the reflected waves, the ultrasonic sensor acquires information indicating the "reflection point, which is the point on the three-dimensional object where the transmitted ultrasonic waves are reflected," the "distance between the ultrasonic sensor and the three-dimensional object," and the like, and transmits this information to the driving assistance ECU 10.

[0023] The camera 23 includes an imaging device and an image analysis device. The imaging device is, for example, a digital camera incorporating an imaging element such as a CCD (charge coupled device) or a CIS (CMOS image sensor). The imaging device is disposed above the front windshield glass. The imaging device captures an image of the view in front of the vehicle at a predetermined frame rate and outputs the acquired image data to the image analysis device. The image analysis device analyzes the acquired image data and acquires information about targets located in front of the vehicle V from the images, and transmits the information to the driving assistance ECU 10. For example, the image analysis device recognizes the light color of a traffic light located ahead in the traveling direction of the vehicle V. The image analysis device also recognizes white lines on the road (division lines, stop lines), etc., and transmits information representing the recognition results to the driving assistance ECU 10.

[0024] The navigation system 24 receives GPS signals from multiple satellites and detects the current location (latitude and longitude) of the vehicle V based on the received GPS signals. The navigation system 24 also stores map data representing a map. The map data includes road information representing roads and traffic light position information representing the locations of traffic lights. The navigation system 24 transmits vehicle position information representing the detected current location to the driving assistance ECU 10. Furthermore, the navigation system 24 has a function to calculate the distance between two points (distance along the road).

[0025] The on-board sensors 20 further include sensors that acquire information about the traveling state of the vehicle V (speed, acceleration, operation mode of an operator, etc.).

[0026] Specifically, the on-vehicle sensors 20 include a speed sensor 25, an acceleration sensor 26, an accelerator pedal sensor 27, a brake pedal sensor 28, a shift lever sensor 29, and a steering sensor 2a.

[0027] The speed sensor 25 includes a wheel speed sensor that generates one pulse signal (wheel pulse signal) each time a wheel of the host vehicle rotates a predetermined angle. The speed sensor 25 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 vs (actual vehicle speed) of the host vehicle based on the wheel speed of each wheel. The speed sensor 25 transmits data representing the speed vs to the driving assistance ECU 10.

[0028] The acceleration sensor 26 detects acceleration Ga acting on the vehicle V (for example, acceleration acting in the width direction of the vehicle V when traveling on a curved road, acceleration acting in the longitudinal direction of the vehicle V when traveling on a straight road, etc.). The acceleration sensor 26 transmits data representing the acceleration Ga to the driving assistance ECU 10.

[0029] The accelerator pedal sensor 27 detects the depression depth AD of an accelerator pedal (not shown) of the vehicle V. The accelerator pedal sensor 27 transmits data indicating the depression depth AD of the accelerator pedal to the driving assistance ECU 10.

[0030] The brake pedal sensor 28 detects the depression depth BD of a brake pedal (not shown) of the vehicle V. The brake pedal sensor 28 transmits to the driving assistance ECU 10 data indicating the depression depth BD of the brake pedal.

[0031] The shift lever sensor 29 detects the position (shift lever position SP) of a shift lever (not shown) of the vehicle V. The shift lever sensor 29 transmits data indicating the shift lever position SP to the driving assistance ECU 10.

[0032] The steering sensor 2a detects the steering angle (also referred to as the steering angle or the turning angle) Φ of the steering wheel. The steering sensor 2a transmits data representing the detected steering angle Φ to the driving assistance ECU 10.

[0033] Furthermore, the on-board sensor 20 includes various switches provided in the vehicle V (for example, a switch for detecting the operation state of a direction indicator operating lever).

[0034] The drive unit 30 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 unit 30 includes an engine ECU 31, an engine actuator 32, an internal combustion engine 33, a transmission 34, and a driving force transmission mechanism (not shown) that transmits the driving force to the wheels. The engine ECU 31 is connected to the engine actuator 32. The engine actuator 32 includes a throttle valve actuator that changes the opening degree of a throttle valve of the internal combustion engine 33. The engine ECU 31 acquires the depression depth AD of the accelerator pedal from the driving assistance ECU 10. The driving assistance ECU 10 can appropriately correct the depression depth AD acquired from the accelerator pedal sensor 27 and send it to the engine ECU 31. The engine ECU 31 drives the engine actuator 32 in accordance with the depression depth AD acquired from the driving assistance ECU 10. In this manner, the torque generated by the internal combustion engine 33 is controlled. The torque generated by the internal combustion engine 33 is transmitted to the drive wheels via a transmission 34 and a drive force transmission mechanism (for example, a drive shaft).

[0035] If the vehicle V to which the driving assistance device 1 is applied is a hybrid vehicle (HEV), the engine ECU 31 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. If the vehicle V to which the driving assistance device 1 is applied is an electric vehicle (BEV), the engine ECU 31 can be replaced with an electric motor ECU that controls the driving force of the vehicle generated by an electric motor as the vehicle driving source.

[0036] The braking device 40 applies braking force to the wheels. The braking device 40 includes a brake ECU 41, a hydraulic circuit 42, and a brake caliper 43. The hydraulic circuit 42 includes a reservoir, an oil pump, various valve devices, a hydraulic sensor, and other components (not shown). The brake caliper 43 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 the brake pad presses against a brake disc. The brake ECU 41 acquires the brake pedal depression depth BD from the driving assistance ECU 10. The driving assistance ECU 10 can appropriately modify the depression depth BD acquired from the brake pedal sensor 28 and send it to the brake ECU 41. The brake ECU 41 transmits a hydraulic control command to the hydraulic circuit 42 in accordance with the depression depth BD acquired from the driving assistance ECU 10. The hydraulic circuit 42 adjusts the hydraulic pressure in the cylinder of the brake caliper 43 in accordance with the hydraulic control command acquired from the brake ECU 41. In this manner, the braking force of the brake caliper 43 on the wheel (brake disc) is controlled.

[0037] The shift-switching device 50 switches the shift position of the transmission 34. The shift-switching device 50 includes a Shift-by-Wire (SBW) ECU 51, an SBW actuator 52, a shift-switching mechanism 53, and the like. The SBW ECU 51 is connected to the SBW actuator 52. The SBW ECU 51 acquires a shift lever position SP from the driving assistance ECU 10. The driving assistance ECU 10 can appropriately correct the shift lever position SP acquired from the shift lever sensor 29 and send it to the SBW ECU 51. The SBW ECU 51 transmits a shift-switching command to the SBW actuator 52 in accordance with the shift lever position SP acquired from the driving assistance ECU 10. The SBW actuator 52 controls the shift-switching mechanism 53 in accordance with the shift-switching command acquired from the SBW ECU 51. In this manner, the shift position of the transmission 34 is switched.

[0038] The steering device 60 controls the steering angle of the steered wheels (left front wheel and right front wheel). The steering device 60 includes an electric power steering ECU (hereinafter referred to as "EPS·ECU") 61, an assist motor (M) 62, and a steering mechanism 63. The EPS·ECU 61 is connected to the assist motor 62 (a drive circuit for the assist motor 62). The assist motor 62 is incorporated into the steering mechanism 63. The steering mechanism 63 is a mechanism for steering the steered wheels. The steering mechanism 63 includes a steering wheel SW, a steering shaft US, and a steering gear mechanism (not shown). The EPS·ECU 61 detects the steering torque input to the steering wheel SW by the driver using a steering torque sensor (not shown) provided on the steering shaft US, and drives the assist motor 62 based on this steering torque. The EPS·ECU 61 applies a steering torque (steering assist torque) to the steering mechanism 63 by driving the assist motor 62, thereby assisting the driver's steering operation.

[0039] In addition, the EPS-ECU 61 acquires the steering angle Φ from the driving assist ECU 10. The driving assist ECU 10 can appropriately correct the steering angle Φ acquired from the steering sensor 2a and send it to the EPS-ECU 61. The EPS-ECU 61 can send a steering command to the EPS-ECU 61 according to the steering angle Φ acquired from the driving assist ECU 10. When the EPS-ECU 61 receives a steering command from the driving assist ECU 10, it drives the assist motor 62 based on the steering command. The steering torque generated by the assist motor 62 in this case differs from the steering assist torque that is applied to assist the driver's steering as described above, and is a torque that is applied to the steering mechanism 63 in response to the steering command from the EPS-ECU 61 without the driver's steering. In this way, the steering angle of the steered wheels of the vehicle is controlled.

[0040] (Activated) Next, a description will be given of the cruise control executed by the driving assistance device 1. The cruise control includes constant speed control and follow-up control.

[0041] The driver can specify whether or not to execute cruise control by operating a switch (not shown). When the driving assistance ECU 10 receives a cruise control start signal from the switch indicating that cruise control is to be started, the driving assistance ECU 10 starts cruise control (ACC). When the driving assistance ECU 10 starts cruise control, it executes the following constant speed traveling control or tracking control.

[0042] <Constant speed control> The driving assistance ECU 10 determines whether or not there is a vehicle (a preceding vehicle) traveling immediately in front of the host vehicle (within a region up to a point a predetermined distance away from the host vehicle) based on information acquired from the on-board sensor 20. If there is a preceding vehicle, the driving assistance ECU 10 detects the speed v0 of the preceding vehicle. If the detected speed v0 exceeds a predetermined value vd, the driving assistance ECU 10 controls the drive device 30, the braking device 40, and the shift switching device 50 (hereinafter referred to as "drive devices, etc.") so that the speed vs of the host vehicle coincides with the predetermined value vd (for example, the vehicle speed at which the fuel consumption rate can be minimized). Note that if there is no preceding vehicle (if it is too far away to be detected), the driving assistance ECU 10 determines that "the speed v0 exceeds the predetermined value vd."

[0043] <Follow-up control> On the other hand, if the detected speed v0 is equal to or less than a predetermined value vd, the driving assistance ECU 10 determines (adopts) the preceding vehicle as a vehicle to be followed. Then, the driving assistance ECU 10 detects (measures) the inter-vehicle distance L between the vehicle to be followed and the subject vehicle based on information acquired from the on-board sensor 20. Furthermore, the driving assistance ECU 10 calculates the speed and acceleration of the vehicle to be followed based on the speed vs of the subject vehicle, changes in the inter-vehicle distance L, etc. Furthermore, the driving assistance ECU 10 calculates a target value Ld of the inter-vehicle distance L based on the speed of the subject vehicle, the speed of the vehicle to be followed, etc.

[0044] When the speed v0 of the target vehicle relative to the speed vs of the host vehicle (relative speed vr = v0 - vs) 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 host vehicle so that the speed vs of the host vehicle is greater than the speed v0 of the target vehicle. Then, the driving assistance ECU 10 controls the drive devices and the like so that the acceleration of the host vehicle matches the target acceleration (hereinafter referred to as "acceleration control"). As a result, the inter-vehicle distance L, which had been greater than the target value Ld, begins to return to the target value Ld. Then, when the inter-vehicle distance L matches the target value Ld, the driving assistance ECU 10 sets the target acceleration of the host vehicle to "0". In other words, the driving assistance ECU 10 controls the drive devices and the like so that the host vehicle travels at the same speed as the target vehicle.

[0045] On the other hand, when the relative speed vr is smaller than "0", the inter-vehicle distance L decreases. When the inter-vehicle distance L decreases below the target value Ld, the driving assistance ECU 10 sets a target acceleration of the host vehicle so that the speed vs of the host vehicle becomes smaller than the speed v0 of the vehicle to be followed. Then, the driving assistance ECU 10 controls the drive device, etc. so that the acceleration of the host vehicle coincides with the target acceleration (hereinafter referred to as "deceleration control"). As a result, the inter-vehicle distance L, which has decreased below 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 acceleration of the host vehicle to "0". Note that the target value Ld is correlated with the speed of the host vehicle and the speed of the vehicle to be followed. A database (table) showing the relationship between these speeds and the target value Ld or parameters specifying an arithmetic expression for determining the target value Ld are stored in the ROM 10b.

[0046] Here, when the vehicle is following a preceding vehicle and the speed vs of the vehicle is equal to or less than a threshold value vth (=vd-Δv) which is smaller than a predetermined value vd (when the vehicle V0 to be followed is traveling at an extremely slow speed), the driving assistance ECU 10 executes the overtaking control described below.

[0047] <Overtaking control> If the host vehicle can follow an adjacent vehicle traveling in an adjacent lane at a higher speed than the host vehicle, the driving assistance ECU 10 changes the host vehicle to the adjacent vehicle. Then, the driving assistance ECU 10 causes the host vehicle to enter the adjacent lane (change lanes), and then causes the adjacent vehicle to follow the host vehicle, causing the host vehicle to overtake the original vehicle V0 to be followed, and then causes the host vehicle to enter (return to) the original lane.

[0048] Specifically, the driving assistance ECU 10 searches for adjacent vehicles traveling at a higher speed than the host vehicle based on information acquired from the on-board sensor 20, and determines the adjacent vehicles as candidates for a new vehicle to be followed. That is, as shown in FIG. 2A , when the host vehicle is traveling in lane La following vehicle V0, the driving assistance ECU 10 detects the speeds of vehicles traveling in lane Lb adjacent to lane La and approaching the host vehicle from behind. Then, the driving assistance ECU 10 determines vehicle V1, whose speed difference with the host vehicle is equal to or less than a predetermined threshold vdif, as a candidate for a new vehicle to be followed. That is, because it is difficult to follow a vehicle traveling at an extremely high speed, the driving assistance ECU 10 excludes the vehicle from the candidates. Note that, when there are multiple vehicles whose speed difference with the host vehicle is equal to or less than the threshold vdif, the leading vehicle V1 among those vehicles is determined as a candidate. However, in this case, the driving assistance ECU 10 may determine a vehicle other than the leading vehicle (for example, the last vehicle) among the plurality of vehicles as a candidate.

[0049] When the inter-vehicle distance Δd between vehicle V1, which is a new candidate vehicle to be followed as determined above, and vehicle V2 traveling immediately behind it is relatively small, or when vehicle V2 is traveling at a higher speed than vehicle V1, the host vehicle may not be able to safely enter between vehicles V1 and V2 (i.e., the host vehicle may not be able to change lanes from lane La to lane Lb). Therefore, the driving assistance ECU 10 determines whether the following condition X is met: (Condition X) The inter-vehicle distance Δd between the vehicle V1 and the vehicle V2 exceeds a predetermined threshold Δdth, and the vehicle V1 is traveling at a higher speed than the vehicle V2. If the condition X is satisfied, the driving assistance ECU 10 determines the vehicle V1 as a new vehicle to be followed. On the other hand, if the condition X is not satisfied, the driving assistance ECU 10 does not determine the vehicle V1 as a new vehicle to be followed, and causes the host vehicle to follow the vehicle V0.

[0050] When the driving assistance ECU 10 determines the vehicle V1 as a new vehicle to be followed, it controls the drive devices and the steering device 60 so that the host vehicle follows the vehicle V1. That is, the driving assistance ECU 10 activates a turn signal to notify the driver of a vehicle surrounding the host vehicle that the host vehicle will change lanes. Then, the driving assistance ECU 10 controls the drive devices 30 and the shift switching device 50 to accelerate the host vehicle, and controls the steering device 60 to adjust the steering angle so that the host vehicle enters the area immediately behind the vehicle V1 (the area between the vehicle V1 and the vehicle V2).

[0051] In this manner, the host vehicle can travel diagonally forward of vehicle V0, the original target vehicle to be followed (see FIGS. 2B and 2C). Thereafter, if the speed v1 of vehicle V1 is equal to or less than the predetermined value vd, the driving assistance ECU 10 continues to make the host vehicle follow vehicle V1. That is, the driving assistance ECU 10 controls the drive device and the like so that the host vehicle follows vehicle V1. When vehicle V1 enters lane La from lane Lb, the driving assistance ECU 10 makes the host vehicle follow vehicle V1 and enter lane La from lane Lb. If there is no area behind vehicle V1 that the host vehicle can enter immediately after vehicle V1 enters lane La, the driving assistance ECU 10 performs constant-speed cruise control of the host vehicle in lane Lb, and when it detects that there is an area in lane La that the host vehicle can enter, makes the host vehicle enter that area. In this way, the overtaking of vehicle V0 is completed.

[0052] On the other hand, after the host vehicle travels diagonally ahead of vehicle V0 in lane Lb, if the speed v1 of vehicle V1 (the host vehicle's speed vs) exceeds a predetermined value vd, the driving assistance ECU 10 causes the host vehicle to travel at a constant speed rather than following vehicle V1. That is, the driving assistance ECU 10 controls the drive device and the like so that the host vehicle's speed vs matches the predetermined value vd. Then, when the driving assistance ECU 10 detects that there is an area in lane La where the host vehicle can enter, it causes the host vehicle to enter that area. In this way, the overtaking of vehicle V0 is completed.

[0053] Next, the operation (ACC program that realizes the above-mentioned cruise control (ACC)) of the CPU 10a (hereinafter simply referred to as "CPU") of the driving assistance ECU 10 will be specifically described with reference to Figures 3 and 4. When the CPU receives a cruise control start signal indicating that cruise control is to be started from the switch, it starts executing the ACC program.

[0054] (ACC Program) The CPU starts the ACC process from step 100 and proceeds to step 101.

[0055] When the CPU proceeds to step 101, it detects the speed v0 of the vehicle V0 traveling just ahead of the host vehicle and determines whether the speed v0 exceeds a predetermined value vd. If the speed v0 exceeds the predetermined value vd (101: Yes), the CPU proceeds to step 102. On the other hand, if the speed v0 is equal to or less than the predetermined value vd (101: No), the CPU proceeds to step 103.

[0056] When the CPU proceeds to step 102, it executes constant speed cruise control. That is, the CPU controls the drive device and the like so that the speed vs of the host vehicle coincides with the predetermined value vd. Then, the CPU returns to step 101.

[0057] When the CPU proceeds to step 103, the CPU executes follow-up control. That is, the CPU controls the drive device and the like so that the inter-vehicle distance L coincides with the target value Ld. Then, the CPU proceeds to step 104.

[0058] When the CPU proceeds to step 104, it determines whether the speed vs of the host vehicle is equal to or less than the threshold value vth (whether the vehicle V0 is traveling at an extremely slow speed). If the speed vs is equal to or less than the threshold value vth (104: Yes), the CPU proceeds to step 105. On the other hand, if the speed vs exceeds the threshold value vth (104: No), the CPU returns to step 101.

[0059] When the CPU proceeds to step 105, it executes the overtaking program shown in Fig. 4. The CPU starts the overtaking process from step 105a and proceeds to step 105b.

[0060] When the CPU proceeds to step 105b, it determines whether or not there is a vehicle (adjacent vehicle) traveling in lane Lb adjacent to lane La in which the host vehicle is traveling. If there is an adjacent vehicle (105b: Yes), the CPU proceeds to step 105c. On the other hand, if there is no adjacent vehicle (105b: No), the CPU proceeds to step 105l and returns to the ACC program.

[0061] In step 105c, the CPU determines vehicle V1 as a candidate for a new vehicle to be followed. That is, the CPU determines vehicle V1 whose speed difference with the host vehicle is equal to or less than threshold value vdif as a candidate for a new vehicle to be followed. Then, the CPU proceeds to step 105d.

[0062] When the CPU proceeds to step 105d, it determines whether or not a lane change from lane La to lane Lb is possible. That is, the CPU determines whether or not the above-mentioned condition X is satisfied. If a lane change is possible (if condition X is satisfied (105d: Yes)), the CPU proceeds to step 105e. On the other hand, if a lane change is not possible (if condition X is not satisfied (105d: No)), the CPU proceeds to step 105l.

[0063] When the CPU proceeds to step 105e, it determines vehicle V1 as a new vehicle to be followed and executes control to overtake vehicle V0. That is, the CPU causes the host vehicle to enter lane Lb, follow vehicle V1, and travel diagonally ahead of vehicle V0. Then, the CPU proceeds to step 105f.

[0064] When the CPU proceeds to step 105f, it determines whether or not it is possible to make the host vehicle continue to follow vehicle V1. That is, it determines whether or not the speed v1 of vehicle V1 is equal to or less than a predetermined value vd. If the host vehicle can be made to follow vehicle V1 (v1≦vd (105f: Yes)), the CPU proceeds to step 105g. On the other hand, if the host vehicle cannot be made to follow vehicle V1 (v1>vd (105f: No)), the CPU proceeds to step 105i.

[0065] When the CPU proceeds to step 105g, it causes the host vehicle to follow vehicle V1. That is, it controls the drive system and the like so that the inter-vehicle distance L between the host vehicle and vehicle V1 matches the target value Ld. Furthermore, when the CPU detects that vehicle V1 has changed lanes from lane Lb to lane La, it determines whether or not there is an area in lane La where the host vehicle can enter. If there is such an area, the CPU controls the drive system and the steering device 60 to cause the host vehicle to enter that area. Then, the CPU proceeds to step 105h.

[0066] When the CPU proceeds to step 105h, it determines whether the host vehicle has returned to the original lane La. If the host vehicle has returned to lane La (105h: Yes), the CPU proceeds to step 105l, terminates the overtaking process, and returns to the ACC process, which is the main routine. On the other hand, if the host vehicle is traveling in lane Lb (105h: No), the CPU returns to step 105f.

[0067] Furthermore, when the CPU proceeds to step 105i, the CPU causes the host vehicle to travel at a low speed. That is, the CPU controls the drive device and the like so that the host vehicle speed vs matches a predetermined value vd. Then, the CPU proceeds to step 105j.

[0068] When the CPU proceeds to step 105j, it determines whether or not there is an area in which the host vehicle can enter the lane La. If such an area exists, the CPU proceeds to step 105k. On the other hand, if such an area does not exist (if it cannot be detected), the CPU returns to step 105f.

[0069] When the CPU proceeds to step 105k, it controls the drive device and the steering device 60 to make the host vehicle enter the above-mentioned area. Then, the CPU proceeds to step 105l.

[0070] When the CPU receives a cruise control end signal indicating that the ACC control is to be ended (stopped) from the switch device during the ACC process, the CPU ends the ACC process when a predetermined time has elapsed from that point.

[0071] (effect) According to the driving assistance device 1 described above, when the host vehicle is following vehicle V0 and vehicle V0 is traveling at an extremely slow speed, the driving assistance ECU 10 can change the vehicle to be followed from vehicle V0 to vehicle V1 traveling in an adjacent lane. The host vehicle can then follow vehicle V1 and overtake vehicle V0. In this case, since the host vehicle is following vehicle V1 (traveling immediately behind vehicle V1), the air resistance value during overtaking is smaller than when the host vehicle is traveling alone. This allows fuel consumption to be kept low. Furthermore, by overtaking vehicle V0, the host vehicle can travel faster than vehicle V0 (can travel at a speed closer to the predetermined value vd), which allows fuel consumption to be reduced while suppressing delays in arrival time at the destination.

[0072] 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.

[0073] <Variation 1> For example, the driving assistance ECU 10 may obtain the driver's approval (see FIG. 4) before starting the overtaking process (step 105e in FIG. 3). That is, if it is possible for the vehicle V1 to follow the vehicle V1 and overtake the vehicle V0 (105d: Yes), the CPU proceeds to step 105m and presents audio or video to the driver to request permission to execute control to overtake the vehicle V0. If the driver operates a switch device (not shown) to send a permission signal to the CPU, the CPU proceeds to step 105e and starts the overtaking process. On the other hand, if the driver operates the switch device to send a prohibition signal to the CPU, or if the driver does not send a permission signal or a prohibition signal within a predetermined time, the CPU proceeds to step 105l.

[0074] <Variation 2> In the above embodiment, when the host vehicle is following the vehicle V0 and the speed vs of the host vehicle is equal to or less than a threshold value vth (=vd-Δv) that is smaller than the predetermined value vd, the driving assistance ECU 10 executes the overtaking control. However, instead of this, when the host vehicle is following the vehicle V0 and the speed v0 of the vehicle V0 is equal to or less than a threshold value vth (=vd-Δv) that is smaller than the predetermined value vd, the driving assistance ECU 10 may execute the overtaking control.

[0075] <Variation 3> In the above example, the driving assistance ECU 10 determines that the target vehicle to be followed can be changed from vehicle V0 to vehicle V1 (the vehicle can follow vehicle V1) when condition X is met. Alternatively, the driving assistance ECU 10 may determine that the target vehicle to be followed can be followed in the following cases. Specifically, the driving assistance ECU 10 calculates (predicts) the time t2 required for vehicle V2 to catch up with the host vehicle based on the longitudinal distance D2 between the host vehicle and vehicle V2, the speed v0 of the host vehicle, and the speed v2 of vehicle V2. If the time t2 exceeds a threshold T (a value obtained by adding a predetermined margin to the time required for the host vehicle to change lanes), the driving assistance ECU 10 determines that the target vehicle to be followed can be changed to vehicle V1. Note that if vehicle V2 is not detected (if it is not within a detectable range), the driving assistance ECU 10 determines that the target vehicle to be followed can be changed to vehicle V1. [Explanation of symbols]

[0076] 1... driving assistance device, 10... driving assistance ECU, 20... on-vehicle sensor, 30... drive device, 40... braking device, 50... shift switching device, 60... steering device, La... lane, Lb... lane

Claims

1. an on-board sensor that acquires and outputs information relating to the position of the vehicle, information relating to targets located around the vehicle, and information relating to the operation of an operating unit of the vehicle; a control device that detects the presence of a preceding vehicle traveling just ahead of the host vehicle based on information acquired from the on-board sensor, determines the preceding vehicle as a vehicle to be followed, and controls at least one of a drive device, a braking device, and a steering device of the host vehicle so that the host vehicle follows the vehicle to be followed; Equipped with The control device When the host vehicle is following a first vehicle as the vehicle to be followed and the speed of the host vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, based on information acquired from the on-board sensor, the system searches for a second vehicle that is traveling in a second lane adjacent to the first lane in which the host vehicle is traveling and is approaching the host vehicle from behind, the second vehicle that is traveling at a higher speed than the host vehicle, and a third vehicle that is traveling immediately behind the second vehicle, and when the distance between the second vehicle and the third vehicle exceeds a threshold and the speed of the second vehicle is higher than the speed of the third vehicle, the system determines that the host vehicle can follow the second vehicle and changes the vehicle to be followed from the first vehicle to the second vehicle. A driving assistance device configured as follows.

2. an on-board sensor that acquires and outputs information relating to the position of the vehicle, information relating to targets located around the vehicle, and information relating to the operation of an operating unit of the vehicle; a control device that detects the presence of a preceding vehicle traveling just ahead of the host vehicle based on information acquired from the on-board sensor, determines the preceding vehicle as a vehicle to be followed, and controls at least one of a drive device, a braking device, and a steering device of the host vehicle so that the host vehicle follows the vehicle to be followed; Equipped with The control device When the host vehicle is following a first vehicle as the vehicle to be followed and the speed of the host vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, the system searches for a second vehicle that is traveling in a second lane adjacent to the first lane in which the host vehicle is traveling and is approaching the host vehicle from behind, the second vehicle that is traveling at a higher speed than the host vehicle, and a third vehicle that is traveling immediately behind the second vehicle, based on information acquired from the on-board sensor, predicts the time required for the third vehicle to catch up with the host vehicle based on the distance between the host vehicle and the third vehicle, the speed of the host vehicle, and the speed of the third vehicle, and if the time obtained by adding a predetermined margin to the predicted time exceeds a threshold, determines that the host vehicle can follow the second vehicle and changes the vehicle to be followed from the first vehicle to the second vehicle. A driving assistance device configured as follows.

3. an information acquisition step of acquiring and outputting information relating to the position of the host vehicle, information relating to targets located around the host vehicle, and information relating to operation of an operation unit of the host vehicle; a control step of detecting the presence of a preceding vehicle traveling just ahead of the host vehicle based on the information acquired in the information acquisition step, determining the preceding vehicle as a vehicle to be followed, and controlling at least one of a drive device, a braking device, and a steering device of the host vehicle so that the host vehicle follows the vehicle to be followed; Including, The control step When the subject vehicle is following a first vehicle as the subject vehicle to be followed and the speed of the subject vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, the method includes a step of searching, based on the information acquired in the information acquisition step, for a second vehicle traveling in a second lane adjacent to the first lane in which the subject vehicle is traveling and approaching the subject vehicle from behind, the second vehicle traveling at a higher speed than the subject vehicle, and a third vehicle traveling immediately behind the second vehicle, and determining that the subject vehicle can follow the second vehicle if the distance between the second vehicle and the third vehicle exceeds a threshold and the speed of the second vehicle is higher than the speed of the third vehicle, and changing the subject vehicle to be followed from the first vehicle to the second vehicle. Driving assistance methods.

4. an information acquisition step of acquiring and outputting information relating to the position of the host vehicle, information relating to targets located around the host vehicle, and information relating to operation of an operation unit of the host vehicle; a control step of detecting the presence of a preceding vehicle traveling just ahead of the host vehicle based on the information acquired in the information acquisition step, determining the preceding vehicle as a vehicle to be followed, and controlling at least one of a drive device, a braking device, and a steering device of the host vehicle so that the host vehicle follows the vehicle to be followed; Including, The control step and when the host vehicle is following a first vehicle as the vehicle to be followed and the speed of the host vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, the method includes a step of searching, based on the information acquired in the information acquisition step, for a second vehicle traveling in a second lane adjacent to the first lane in which the host vehicle is traveling and approaching the host vehicle from behind, the second vehicle traveling at a higher speed than the host vehicle, and a third vehicle traveling immediately behind the second vehicle, predicting the time required for the third vehicle to catch up with the host vehicle based on the distance between the host vehicle and the third vehicle, the speed of the host vehicle, and the speed of the third vehicle, and determining that the host vehicle can follow the second vehicle if the time obtained by adding a predetermined margin to the predicted time exceeds a threshold, and changing the vehicle to be followed from the first vehicle to the second vehicle. Driving assistance methods.

5. A computer provided in the vehicle, an information acquisition step of acquiring and outputting information relating to the position of the host vehicle, information relating to targets located around the host vehicle, and information relating to operation of an operation unit of the host vehicle; a control step of detecting the presence of a preceding vehicle traveling just ahead of the host vehicle based on the information acquired in the information acquisition step, determining the preceding vehicle as a vehicle to be followed, and controlling at least one of a drive device, a braking device, and a steering device of the host vehicle so that the host vehicle follows the vehicle to be followed; A driving assistance program that executes The control step When the subject vehicle is following a first vehicle as the subject vehicle to be followed and the speed of the subject vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, the method includes a step of searching, based on the information acquired in the information acquisition step, for a second vehicle traveling in a second lane adjacent to the first lane in which the subject vehicle is traveling and approaching the subject vehicle from behind, the second vehicle traveling at a higher speed than the subject vehicle, and a third vehicle traveling immediately behind the second vehicle, and determining that the subject vehicle can follow the second vehicle if the distance between the second vehicle and the third vehicle exceeds a threshold and the speed of the second vehicle is higher than the speed of the third vehicle, and changing the subject vehicle to be followed from the first vehicle to the second vehicle. Driver assistance programs.

6. A computer provided in a vehicle, an information acquisition step of acquiring and outputting information relating to the position of the host vehicle, information relating to targets located around the host vehicle, and information relating to operation of an operation unit of the host vehicle; a control step of detecting the presence of a preceding vehicle traveling just ahead of the host vehicle based on the information acquired in the information acquisition step, determining the preceding vehicle as a vehicle to be followed, and controlling at least one of a drive device, a braking device, and a steering device of the host vehicle so that the host vehicle follows the vehicle to be followed; A driving assistance program that executes The control step and when the host vehicle is following a first vehicle as the vehicle to be followed and the speed of the host vehicle or the speed of the first vehicle is equal to or less than a predetermined first threshold, the method includes a step of searching, based on the information acquired in the information acquisition step, for a second vehicle traveling in a second lane adjacent to the first lane in which the host vehicle is traveling and approaching the host vehicle from behind, the second vehicle traveling at a higher speed than the host vehicle, and a third vehicle traveling immediately behind the second vehicle, predicting the time required for the third vehicle to catch up with the host vehicle based on the distance between the host vehicle and the third vehicle, the speed of the host vehicle, and the speed of the third vehicle, and determining that the host vehicle can follow the second vehicle if the time obtained by adding a predetermined margin to the predicted time exceeds a threshold, and changing the vehicle to be followed from the first vehicle to the second vehicle. Driver assistance programs.

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