Driving assistance method and driving assistance device

Abstract

When there is a leading vehicle to be followed, the driving assistance device outputs a target acceleration / deceleration for causing the vehicle to follow the leading vehicle. On the other hand, when there is no leading vehicle to be followed, the driving assistance device outputs a target acceleration for causing the vehicle's speed to become a set constant speed. In addition, the target acceleration is changed (corrected) according to the lane width.

Description

Technical Field

[0001] The present disclosure relates to a driving assistance method and a driving assistance device for assisting driving of a vehicle. Background Art

[0002] In recent years, adaptive cruise control (ACC) has attracted attention as a technology to assist vehicle driving (see, for example, Patent Document 1). ACC uses information such as the vehicle's speed, the relative speed of the preceding vehicle, and the distance between the preceding vehicle and the vehicle in front to control the vehicle's drive and braking systems to maintain a constant speed and distance to the preceding vehicle.

[0003] Another technology that assists vehicle driving is cruise control (hereinafter referred to as "CC") (see, for example, Patent Document 2). CC detects the difference between the driver's set speed and the actual vehicle speed (actual speed) and controls the engine output and the transmission gear (speed ratio) based on this speed difference to ensure that the actual vehicle speed converges to the set speed. In short, CC maintains the vehicle's speed at a set constant speed even when the driver is not pressing the accelerator pedal.

[0004] Generally, a vehicle equipped with an ACC function also has a CC function as one of the ACC functions. The CC function is executed when there is no preceding vehicle, for example.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 7-17295

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 1-202538 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] The present disclosure provides a driving assistance method and a driving assistance device, which can reduce the pressure on the driver caused by acceleration without reducing the followability of the preceding vehicle in a vehicle having both ACC and CC functions.

[0011] Technical solutions to the problem

[0012] One embodiment of the driving assistance method disclosed herein is:

[0013] A driving assistance method for assisting driving of a vehicle, comprising:

[0014] A preceding vehicle determination step is to determine whether there is a preceding vehicle that the vehicle should follow;

[0015] a lane width detection step, detecting the width of the lane in which the vehicle is traveling; and

[0016] The target control value output step outputs the target acceleration / deceleration or the target acceleration of the vehicle for automatic driving.

[0017] In the target control value output step,

[0018] When a determination result indicating that a preceding vehicle to be followed is obtained in the preceding vehicle determination step, outputting a target acceleration / deceleration for causing the host vehicle to follow the preceding vehicle based on the relative speed and inter-vehicle distance between the host vehicle and the preceding vehicle;

[0019] On the other hand, when a determination result indicating that there is no preceding vehicle to be followed is obtained in the preceding vehicle determination step and the speed of the own vehicle is less than a set speed, a target acceleration for making the speed of the own vehicle become the set constant speed is output. In addition, the target acceleration is changed according to the lane width obtained in the lane width detection step.

[0020] One embodiment of the driving assistance device disclosed herein is:

[0021] A driving assistance device for assisting driving of a vehicle, comprising:

[0022] A preceding vehicle determination unit determines whether there is a preceding vehicle that the vehicle should follow;

[0023] a lane width detection unit for detecting the width of the lane in which the vehicle is traveling; and

[0024] The target control value output unit outputs the target acceleration / deceleration or target acceleration of the vehicle for automatic driving.

[0025] The target control value output unit,

[0026] outputting target acceleration / deceleration for causing the host vehicle to follow the preceding vehicle based on the relative speed and inter-vehicle distance between the host vehicle and the preceding vehicle when the preceding vehicle determination unit determines that there is a preceding vehicle to be followed;

[0027] On the other hand, when a determination result indicating that there is no preceding vehicle to be followed is obtained by the preceding vehicle determination unit and the speed of the own vehicle is less than a set speed, a target acceleration for making the speed of the own vehicle become the set constant speed is output. In addition, the target acceleration is changed according to the lane width obtained by the lane width detection unit.

[0028] Effects of the Invention

[0029] According to the present disclosure, the target acceleration is changed according to the lane width when there is no preceding vehicle to be followed. Therefore, in a vehicle having both ACC and CC functions, the pressure on the driver caused by acceleration when switching to constant speed driving can be reduced without reducing the ability to follow the preceding vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 1 is an external view showing an example of a vehicle to which the driving assistance device according to the embodiment is applied.

[0031] Figure 2 It is a block diagram showing the structure of a vehicle according to the embodiment.

[0032] Figure 3 is a block diagram showing the structure of a driving assistance device.

[0033] Figure 4 This is a flowchart for explaining the driving control operation of the driving assistance device. DETAILED DESCRIPTION

[0034] Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0035] <1> Vehicle structure

[0036] First, the structure of a vehicle including a driving assistance device according to an embodiment of the present disclosure will be described.

[0037] Figure 1 1 is an external view showing an example of a vehicle 1 to which the driving assistance device of this embodiment is applied. Figure 2 2 is a block diagram showing the structure of the vehicle 1. Note that, here, the illustration and description focus on the portion related to the driving assistance device.

[0038] like Figure 1 As shown, vehicle 1 is a tractor head (tractor) capable of towing a trailer 2. Vehicle 1 includes a vehicle body 3 and trailer 2. Vehicle body 3 includes a power system such as an engine and drive wheels and a driver's seat, and trailer 2 is connected to vehicle body 3.

[0039] like Figure 2 As shown, the vehicle 1 includes a drive system 10 for driving the vehicle 1 , a brake system 20 for decelerating the vehicle 1 , and a driving assistance device 30 for assisting a driver in driving the vehicle 1 .

[0040] The drive system 10 includes an engine 11 , a clutch 12 , a transmission 13 , a propeller shaft 14 , a differential device 15 , a drive shaft 16 , wheels 17 , an engine ECU 18 , and a power transmission ECU 19 .

[0041] The engine ECU 18 and the powertrain ECU 19 are connected to the driving assistance device 30 via an in-vehicle network such as a CAN (Controller Area Network), enabling them to exchange necessary data and control signals. The engine ECU 18 controls the output of the engine 11 in response to drive commands from the driving assistance device 30. The powertrain ECU 19 controls the engagement and disengagement of the clutch 12 and the shifting of the transmission 13 in response to drive commands from the driving assistance device 30.

[0042] The power of the engine 11 is transmitted to the transmission 13 via the clutch 12. The power transmitted to the transmission 13 is further transmitted to the wheels 17 via the propeller shaft 14, the differential device 15, and the drive shaft 16. Thus, the power of the engine 11 is transmitted to the wheels 17, causing the vehicle 1 to travel.

[0043] The brake system 20 includes a service brake 21 , auxiliary brakes 22 and 23 , a parking brake (not shown), and a brake ECU 24 .

[0044] Generally, the service brake 21 is called a service brake, friction brake, service brake, or foundation brake. The service brake 21 is, for example, a drum brake that obtains braking force by pressing a brake lining against the inside of a brake drum that rotates together with the wheel 17 .

[0045] The auxiliary brake 22 is a speed reducer (hereinafter referred to as "speed reducer 22") that generates braking force by directly applying a load to the rotation of the transmission shaft 14. For example, it is an electromagnetic speed reducer. The auxiliary brake 23 is an exhaust brake (hereinafter referred to as "exhaust brake 23") that utilizes the engine's rotational resistance to enhance the engine's braking effect. The provision of speed reducer 22 and exhaust brake 23 increases braking force and reduces the frequency of use of the service brake 21, thereby minimizing wear on brake pads and other components.

[0046] The brake ECU 24 is connected to the driving assistance device 30 via an on-vehicle network such as a CAN, enabling the exchange of necessary data and control signals. The brake ECU 24 controls the braking force of the service brake 21 (the brake fluid pressure in the wheel cylinders of the wheels 17) in accordance with the braking command from the driving assistance device 30.

[0047] The braking operation of the service brake 21 is controlled by the driving assistance device 30 and the brake ECU 24. The braking operation of the retarder 22 and the exhaust brake 23 is controlled on / off by the driving assistance device 30. Because the braking force of the retarder 22 and the exhaust brake 23 is generally constant, the service brake 21, which allows for fine adjustment of the braking force, is preferably used to accurately generate the desired braking force.

[0048] The driving assistance device 30 receives input from a millimeter-wave radar or camera. This information indicates traffic conditions or road conditions ahead of the vehicle. Furthermore, the driving assistance device 30 includes an ACC operation unit 41, an accelerator operation detection unit 43, and a brake operation detection unit 44.

[0049] The driving assistance device 30 generates control signals for controlling the operation of the drive system 10 and the brake system 20. In particular, the driving assistance device 30 of this embodiment determines target acceleration / deceleration for achieving ACC and target acceleration for achieving CC, and outputs these signals appropriately to the engine ECU 18, the power transmission ECU 19, and the brake ECU 24.

[0050] It should be noted that, in reality, CC is implemented as one of the functions of ACC. However, in this embodiment, to facilitate understanding, the functions of CC and ACC are sometimes described separately.

[0051] Although not shown, the engine ECU 18, the power transmission ECU 19, the brake ECU 24, and the driving assistance device 30 each include, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, a working memory such as a RAM (Random Access Memory), and a communication circuit. In this case, for example, the functions of the various components of the driving assistance device 30 described below are implemented by the CPU executing the control program. It should be noted that all or part of the engine ECU 18, the power transmission ECU 19, the brake ECU 24, and the driving assistance device 30 may also be integrally formed.

[0052] The ACC operating unit 41 includes an ACC on / off switch for controlling ACC operation. It also includes setting switches for configuring various ACC and CC settings. By operating the setting switches, the driver can set, for example, a target inter-vehicle distance and a target vehicle speed. These switches can also be implemented using a user interface displayed on a display with a touchscreen.

[0053] The accelerator operation detection unit 43 detects the amount of depression of the accelerator pedal and outputs the detection result to the driving assistance device 30. The driving assistance device 30 sends a drive command to the engine ECU 18 and the power transmission ECU 19 based on the amount of depression of the accelerator pedal.

[0054] The brake operation detection unit 44 detects the amount of depression of the brake pedal for activating the service brake 21. Furthermore, the brake operation detection unit 44 detects whether the auxiliary brake lever for activating the retarder 22 or the exhaust brake 23 has been operated. The brake operation detection unit 44 then outputs the detection results regarding the brake pedal and the auxiliary brake lever to the driving assistance device 30. The driving assistance device 30 sends a braking command to the brake ECU 24 based on the amount of depression of the brake pedal. Furthermore, the driving assistance device 30 controls the on / off operation of the retarder 22 or the exhaust brake 23 based on the operation of the auxiliary brake lever.

[0055] Furthermore, the driving assistance device 30 outputs various types of information related to driving from the information output unit 50 .

[0056] <2> Structure of driving assistance system

[0057] Figure 3 3 is a block diagram showing the configuration of the driving assistance device 30 according to the present embodiment.

[0058] The driving assistance device 30 includes a target control value output unit 31 , an inter-vehicle distance detection unit 33 , a preceding vehicle determination unit 34 , and a lane width detection unit 35 .

[0059] The target control value output unit 31 includes an ACC unit 31a and a CC unit 31b. It should be noted that, as described above, CC is actually implemented as a function of ACC, but in this embodiment, the functions of CC and ACC are described separately for ease of understanding. Figure 3 As shown, the ACC portion 31a and the CC portion 31b may not be separated, and the CC portion 31b may be included in the ACC portion 31a.

[0060] The ACC unit 31a and CC unit 31b basically perform known ACC and CC processes, respectively. Specifically, the ACC unit 31a outputs target acceleration / deceleration for the vehicle to follow the preceding vehicle based on the relative speed and inter-vehicle distance between the vehicle and the preceding vehicle. This implements automatic following control. Meanwhile, the CC unit 31b outputs target acceleration for maintaining the vehicle's speed at a set constant speed. This implements constant speed driving control.

[0061] Automatic following control operates the drive system 10 and brake system 20 to bring the inter-vehicle distance within a predetermined target range and the relative speed close to zero when a preceding vehicle is present within a predetermined range. Constant speed control operates the drive system 10 and brake system 20 to bring the vehicle 1's travel speed close to a predetermined target value when a preceding vehicle is not present within a predetermined range.

[0062] The inter-vehicle distance detection unit 33 measures (detects) the inter-vehicle distance between the host vehicle 1 and the preceding vehicle based on information obtained from the front of the host vehicle 1 by millimeter-wave radar, cameras, etc., and outputs the measurement result to the ACC unit 31. It should be noted that the inter-vehicle distance detection unit 33 may also measure the inter-vehicle distance based on information from other sensors such as lidar.

[0063] The preceding vehicle determination unit 34 determines whether there is a preceding vehicle to be followed based on information on traffic conditions ahead of the host vehicle 1 obtained by millimeter-wave radar, cameras, etc. Specifically, if there is a vehicle ahead in the same lane as the host vehicle, it is determined that there is a preceding vehicle.

[0064] The lane width detection unit 35 detects the width of the lane in which the vehicle 1 is traveling based on information about the road conditions ahead of the vehicle 1 obtained by millimeter-wave radar, a camera, etc. Specifically, the lane width is detected by detecting curbs or lanes based on images obtained by the camera and calculating the length between them.

[0065] <3> Driving control actions of driving assistance systems

[0066] Next, the travel control operation of the driving assistance device 30 will be described. Figure 4 This is a flowchart for explaining the travel control operation of the driving assistance device 30 .

[0067] First, after the driver sets the ACC and CC settings in step S11 (e.g., after the ACC and CC are turned on), the driving assistance device 30 proceeds to step S12. In step S12, the preceding vehicle determination unit 34 determines whether there is a preceding vehicle. If so, the process proceeds to step S13; otherwise, the process proceeds to step S14.

[0068] In step S13, ACC is executed by the ACC unit 31a of the target control value output unit 31. Specifically, in step S13, the ACC unit 31a uses the inter-vehicle distance information to the preceding vehicle input from the inter-vehicle distance detection unit 33 and the relative speed information to the preceding vehicle obtained from the millimeter-wave radar or camera to output target acceleration / deceleration for the host vehicle to follow the preceding vehicle. The target acceleration / deceleration is appropriately transmitted to the engine ECU 18, the power transmission ECU 19, and the brake ECU 24.

[0069] In steps S14-S15-S16, the CC of the target control value output unit 31 is executed. Specifically, first, in step S14, the CC unit 31b determines whether the current vehicle speed v is less than a preset set speed (target speed). If the vehicle speed v is less than the set speed (target speed) (step S14: Yes), the process proceeds to step S15. Otherwise (step S14: No), the process returns to step S12.

[0070] In step S15, the lane width detection unit 35 detects the width of the lane in which the vehicle is traveling. Of course, the lane width detection unit 35 may always detect the lane width.

[0071] In the next step S16, the CC unit 31b outputs a target acceleration corresponding to the lane width. Specifically, the CC unit 31b first inputs vehicle speed information from a vehicle speed sensor (not shown), calculates the difference between the vehicle speed and the target vehicle speed set by the ACC operation unit 41, and then determines a target acceleration corresponding to the difference. This target acceleration is determined, for example, by referring to a table.

[0072] Furthermore, the CC unit 31b of this embodiment changes (corrects) the calculated target acceleration based on the lane width detected by the lane width detection unit 35. Specifically, the CC unit 31b changes (corrects) the target acceleration so that the target acceleration decreases as the lane width becomes narrower. The changed (corrected) target acceleration is transmitted to the engine ECU 18 and the power transmission ECU 19.

[0073] <4> Effects of implementation

[0074] As described above, according to this embodiment, when there is a leading vehicle to be followed, the target acceleration / deceleration for causing the vehicle to follow the leading vehicle is output. On the other hand, when there is no leading vehicle to be followed, the target acceleration for causing the vehicle's speed to become a set constant speed is output. In addition, the target acceleration is changed (corrected) according to the lane width.

[0075] Thus, when there is a leading vehicle to be followed, following control is maintained without reducing the responsiveness of following the leading vehicle, and when there is no leading vehicle to be followed, acceleration is controlled according to the lane width. Therefore, in a vehicle with both ACC and CC functions, automatic driving can be achieved in various driving environments without causing the driver to feel burdened or uneasy.

[0076] In other words, in the driving assistance method of this embodiment, it can be said that the target acceleration / deceleration for following the preceding vehicle does not depend on the lane width, but the target acceleration for constant speed driving depends on the lane width.

[0077] While ACC controls the vehicle speed to approach the set speed (i.e., CC) when there's no vehicle ahead, sudden acceleration on narrow roads can cause a sense of oppression. Especially for large vehicles like trucks, sudden acceleration on narrow roads can cause a sense of oppression not only for the driver but also for pedestrians and other nearby people.

[0078] In this embodiment, when the road width is narrow, the acceleration required to set the vehicle speed is corrected to be less than the base acceleration. This reduces the sense of pressure on the driver, pedestrians, and other nearby people caused by acceleration during the transition to constant speed driving. In this way, in a vehicle equipped with both ACC and CC functions, automated driving can be achieved that reduces the sense of pressure on the driver caused by acceleration during the transition to constant speed driving without compromising the ability to follow the vehicle ahead.

[0079] <5> Other implementation methods

[0080] The above embodiment is only a specific example of implementing the present invention, and the technical scope of the present invention should not be interpreted as limited thereby. That is, the present invention can be implemented in various forms within the scope of its gist or main features.

[0081] <5-1> In the above embodiment, the target acceleration is changed so that the narrower the lane width, the smaller the target acceleration (i.e., the target acceleration is subjected to a damping correction). However, the target acceleration correction amount may also be changed based on the difference between the set speed and the host vehicle speed. Specifically, the smaller the difference between the set speed and the host vehicle speed, the smaller the damping amount (correction amount) of the target acceleration. This prevents the undesirable situation where, if the damping correction continues, the host vehicle speed approaches the set speed and cannot reach the set speed.

[0082] <5-2> In addition to the above embodiment, the acceleration may be corrected so that the greater the ratio of vehicle width to lane width (vehicle width ÷ lane width), the lower the acceleration. This allows for less oppressive control that takes vehicle width into account.

[0083] <5-3> In addition to the above-described embodiment, when the lane width cannot be detected, the attenuation amount of the target acceleration may be set as the maximum attenuation amount.

[0084] <5-4> In the above embodiment, the vehicle 1 to which the driving support device and method of the present invention are applied is a tractor that can be coupled to a trailer 2 and tow. However, the vehicle to which the present invention is applied is not limited thereto and may be, for example, a passenger car or other vehicle.

[0085] This application is based on Japanese patent application (Japanese Patent Application No. 2020-033738) filed on February 28, 2020, the contents of which are incorporated herein by reference in their entirety.

[0086] Industrial Applicability

[0087] The driving assistance method and driving assistance device of the present disclosure are useful as a driving assistance device and driving assistance method that can reduce the driver's sense of pressure caused by acceleration without reducing the ability to follow the preceding vehicle in a vehicle having both ACC and CC functions.

[0088] Description of Reference Numerals

[0089] 1 vehicle

[0090] 2 trailers

[0091] 3 Vehicle body

[0092] 10. Drive System

[0093] 11 Engine

[0094] 12 Clutch

[0095] 13 Transmission

[0096] 14 Drive shaft

[0097] 15 Differential

[0098] 16 drive shaft

[0099] 17 wheels

[0100] 18 Engine ECU

[0101] 19 Powertrain ECU

[0102] 20 Braking System

[0103] 21 Service brake

[0104] 22 Reducer

[0105] 23 Exhaust brake

[0106] 24 Brake ECU

[0107] 30 Driving assistance devices

[0108] 31 Target control value output unit

[0109] 31a ACC Department

[0110] Section 31b CC

[0111] 33. Inter-vehicle distance detection department

[0112] 34. Front vehicle detection unit

[0113] 35 Lane Width Detection Unit

[0114] 41 ACC operation unit

[0115] 43 Accelerator operation detection unit

[0116] 44 Brake operation detection unit

[0117] 50 Information output unit

Claims

1. A driving assistance method for assisting driving of a vehicle, comprising: A preceding vehicle determination step is to determine whether there is a preceding vehicle that the vehicle should follow; A lane width detection step, detecting the width of the lane in which the vehicle is traveling; as well as The target control value output step outputs the target acceleration / deceleration or the target acceleration of the vehicle for automatic driving. In the target control value output step, When a determination result indicating that a preceding vehicle to be followed is obtained in the preceding vehicle determination step, outputting a target acceleration / deceleration for causing the host vehicle to follow the preceding vehicle based on the relative speed and inter-vehicle distance between the host vehicle and the preceding vehicle; On the other hand, when a determination result indicating that there is no preceding vehicle to be followed is obtained in the preceding vehicle determination step and the speed of the own vehicle is less than a set speed, a target acceleration for causing the speed of the own vehicle to become the set constant speed is calculated. Furthermore, the target acceleration is corrected and output based on the ratio of the lane width obtained in the lane width detection step to the vehicle width of the own vehicle.

2. The driving assistance method according to claim 1, wherein: The target acceleration / deceleration outputted in the target control value outputting step does not depend on the lane width, and the target acceleration depends on the lane width.

3. The driving assistance method according to claim 1, wherein: In the target control value output step, the target acceleration is changed so that the target acceleration decreases as the lane width becomes narrower.

4. The driving assistance method according to claim 3, wherein: In the target control value outputting step, the smaller the difference between the set constant vehicle speed and the host vehicle speed, the smaller the attenuation correction amount of the target acceleration based on the lane width.

5. A driving assistance device for assisting driving of a vehicle, comprising: A preceding vehicle determination unit determines whether there is a preceding vehicle that the vehicle should follow; A lane width detection unit detects the width of the lane in which the vehicle is traveling; as well as The target control value output unit outputs the target acceleration / deceleration or target acceleration of the vehicle for automatic driving. The target control value output unit, outputting target acceleration / deceleration for causing the host vehicle to follow the preceding vehicle based on the relative speed and inter-vehicle distance between the host vehicle and the preceding vehicle when the preceding vehicle determination unit determines that there is a preceding vehicle to be followed; On the other hand, when a determination result indicating that there is no preceding vehicle to be followed is obtained by the preceding vehicle determination unit and the speed of the own vehicle is less than a set speed, a target acceleration for making the speed of the own vehicle become the set constant speed is calculated. Furthermore, the target acceleration is corrected and output based on the ratio of the lane width obtained by the lane width detection unit to the vehicle width of the own vehicle.

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