Driving assistance systems

Abstract

The present invention provides a driver assistance device that can maintain good accuracy in determining the visibility of the area in front of the vehicle when the vehicle is traveling on a curve. [Solution] The processor performs the following: a first process of acquiring as the first curve range C1 the range that is expected to be within the field of view of the camera 21 when the vehicle is traveling on curve C, provided that there are no objects OB that reduce the recognition accuracy of at least a part of curve C; a second process of acquiring as the second curve range C2 the range from the acquired image that can be recognized as curve C; and a third process of determining whether the visibility of the forward area is good or bad based on the ratio of the second curve range C2 to the first curve range C1, and adjusting the target value so that the speed of the vehicle when visibility is not determined to be good is lower than the speed when visibility is not determined to be good.

Description

Technical Field

[0001] The present invention relates to a driving support device that supports a driving operation for adjusting the speed of a host vehicle.

Background Art

[0002] There has been proposed a driving support device that supports a driving operation for adjusting the speed of a host vehicle (see, for example, Patent Document 1 below). The processor of this driving support device (hereinafter referred to as the "conventional device") determines a target value of the speed of the host vehicle based on information acquired from various sensors, and has a speed adjustment function for controlling a driving device and / or a braking device so that the speed (measured value) of the host vehicle matches the target value. Thereby, even if the driver does not perform the operation of stepping on the accelerator pedal and the brake pedal, the speed of the host vehicle is automatically adjusted to an appropriate value.

[0003] Here, when the host vehicle enters a curve in a state where the speed of the host vehicle is set to be automatically adjusted by the above speed adjustment function, the processor of the conventional device sets a target value of the speed of the host vehicle so that the acceleration acting in the lateral direction of the host vehicle when traveling on the curve is below a threshold value. Thereby, the comfort (riding comfort, sense of security, etc.) of the driver (occupant) is kept good.

[0004] By the way, a scene is assumed in which there is an object (building, signboard, etc.) that reduces the visibility of the front region (region on the tip side of the curve) near the inner peripheral edge portion of the curve. The conventional device sets a target value of the speed of the host vehicle so that the speed of the host vehicle is lower when the visibility of the front region is poor than when the visibility of the front region is good in the curve.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] The processor in the conventional device described above is configured to determine the visibility of the area ahead on a curve based on map information. However, if the placement of objects that affect visibility in the area ahead changes, or if such objects are temporarily placed, and this information is not reflected in the map information, the accuracy of determining visibility in the area ahead on a curve may decrease.

[0007] One of the objectives of the present invention is to provide a driving assistance device that can maintain good accuracy in determining the visibility of the area in front of the vehicle when the vehicle is traveling on a curve.

[0008] To achieve the above objective, the driving assistance device (1) of the present invention includes a processor (10) configured to set a target value (spt) for the speed (sp0) of the vehicle (V0) and to control various devices of the vehicle so that the measured value of the vehicle's speed matches the target value. The driving assistance device also includes a camera (21) for acquiring an image of the area in front of the vehicle. The processor is capable of performing the following: a first process of acquiring a first curve range (C1) as the area that is expected to be within the field of view of the camera when the vehicle is traveling on a curve (C) and there are no objects (OB) that reduce the recognition accuracy of at least a part of the curve; a second process of acquiring a second curve range C2 as the area that can be recognized as the curve from the acquired image; and a third process of determining whether the visibility of the area in front is good or bad based on the ratio of the second curve range to the first curve range, and adjusting the target value so that the speed of the vehicle when visibility is not determined to be good is lower than the speed when visibility is not determined to be good.

[0009] The driving assistance device according to the present invention determines the visibility of the area ahead (the area at the tip of the curve) when driving on a curve, based on the range of the curve that is expected to be within the camera's field of view (first curve range) and the range of the curve in the image actually acquired by the camera (second curve range). In other words, in the present invention, map information is not used when determining the visibility of the area ahead on a curve. Therefore, according to the present invention, good accuracy in determining the visibility of the area ahead is maintained. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a block diagram of a driver assistance device according to one embodiment of the present invention. [Figure 2] Figure 2 is a plan view showing an example where there are no objects affecting the line of sight in the forward area near the inner edge of the curve (Figure 2(A)) and an example where such objects are present (Figure 2(B)). [Figure 3] Figure 3 is a flowchart of the program executed by the CPU to implement the speed adjustment function.

[0011] (Outline) The driver assistance device 1 according to one embodiment of the present invention is applied, for example, to a vehicle V0 equipped with an autonomous driving function (hereinafter referred to as "the vehicle"). The driver assistance device 1 includes a function (speed adjustment function) that automatically adjusts the speed sp0 of the vehicle. The speed adjustment function includes a function (curve deceleration function) that adjusts (decelerates) the speed of the vehicle when the vehicle is traveling on a curve so as to maintain a state of good comfort for the driver (occupants). Note that the speed adjustment function according to this embodiment may be one of a plurality of functions that constitute the autonomous driving function.

[0012] (Specific configuration) As shown in Figure 1, the driver assistance system 1 includes an ECU 10, an on-board sensor 20, a drive unit 30, and a braking unit 40.

[0013] The ECU10 includes a microcomputer equipped with a CPU10a, ROM10b, RAM10c, timer10d, and other components.

[0014] The on-board sensor 20 includes a camera 21. The camera 21 is equipped with an imaging device and an image analysis device. The imaging device incorporates a lens and an image sensor such as a CCD (charge coupled device) or CIS (CMOS image sensor). The imaging device is positioned at the top of the front windshield glass and directed forward. The imaging device captures the foreground of the vehicle at a predetermined frame rate and acquires image data. The imaging device transmits the image data to the image analysis device. The image analysis device analyzes the acquired image data and obtains information about objects located in front of the vehicle from the image. For example, the image analysis device recognizes (calculates) other vehicles located in front of the vehicle (preceding vehicle V1), information about the shape of the road (curve radius R), etc., and provides the calculation results to the ECU 10.

[0015] In addition, the on-board sensor 20 includes a speed sensor 22. The speed sensor 22 detects the rotational speed (wheel speed) of each wheel and calculates the vehicle's speed sp0 (measured value) based on the wheel speed. The speed sensor 22 provides the calculation result to the ECU 10.

[0016] The vehicle-mounted sensor 20 also includes a navigation system 23. The navigation system 23 acquires GPS signals from multiple satellites and obtains the vehicle's current location (latitude and longitude) based on these GPS signals. The navigation system 23 stores map information. This map information includes information indicating the degree of curvature (curve radius R).

[0017] In addition, the on-board sensor 20 includes a radar (not shown) that detects the distance between the vehicle and a three-dimensional object (preceding vehicle V1) located in front of the vehicle. Furthermore, the on-board sensor 20 includes a sensor (not shown) that acquires the acceleration G acting laterally on the vehicle.

[0018] The drive unit 30 applies driving force to the drive wheels. The drive unit 30 includes an engine ECU, an internal combustion engine, a transmission, and a driving force transmission mechanism that transmits driving force to the wheels. The engine ECU obtains information (target value) representing the target driving force from another ECU (ECU 10). The engine ECU drives the throttle valve of the internal combustion engine to match the driving force applied to the drive wheels to the target value.

[0019] Furthermore, if the vehicle to which the driver assistance system 1 is applied is a hybrid electric vehicle (HEV), the engine ECU can adjust the output (driving force) of either the internal combustion engine or the electric motor, or both, as the vehicle's power source. Also, if the vehicle to which the driver assistance system 1 is applied is an electric electric vehicle (BEV), an electric motor ECU that adjusts the output (driving force) of the electric motor, which is the vehicle's power source, is used instead of the engine ECU.

[0020] The braking system 40 applies braking force to the wheels (brake discs). The braking system 40 includes a brake ECU, brake calipers, etc. The brake calipers include actuators that press brake pads against the brake discs. The brake ECU obtains information (target value) representing the target braking force from other ECUs. The brake ECU drives the actuators of the brake calipers to match the braking force applied to the wheels (brake discs) to the target value.

[0021] (Speed ​​adjustment function) When a switch (not shown) used to activate the speed adjustment function is turned ON, the ECU10 controls the drive system and other components so that the speed sp0 reaches an appropriate value. The speed adjustment function includes a constant speed driving function and a follow function.

[0022] (Constant Speed ​​Driving Function) If there is no preceding vehicle V1 (another vehicle driving directly in front of the current vehicle), the ECU10 acquires a speed value (set value spset) that has been set in advance by the driver as the target value spt. The ECU10 then executes a constant speed driving process that controls the drive system and other components so that the measured speed sp0 matches the target value spt.

[0023] (Following Function) When there is a preceding vehicle V1, the ECU 10 sequentially determines (updates) the target value spt of the speed sp0 so that the inter-vehicle distance between the preceding vehicle V1 and the host vehicle is maintained at a predetermined value or more and the host vehicle follows and travels behind the preceding vehicle V1. The ECU 10 executes a following process to control the drive device or the like so that the measured value of the speed sp0 matches the target value spt.

[0024] (Curve Deceleration Function) When the ECU 10 executes speed adjustment control in a curve, it determines the upper limit value splmt of the target value spt of the speed sp0 of the host vehicle so that the lateral acceleration G acting on the host vehicle is below the threshold value Gth. Specifically, the ECU 10 calculates the time t required for the host vehicle to enter the curve based on the information obtained from the in-vehicle sensors 20 (such as the speed sensor 22 and the navigation system 23). When the time t is below the threshold value tth, the ECU 10 obtains the degree of curvature (curve radius R) of the curve based on the information obtained from the camera 21 and / or the map information of the navigation system 23. Here, the ECU 10 has a map (database) that prescribes the relationship between the curve radius R and the upper limit value splmt in advance. The ECU 10 refers to the map to obtain the upper limit value splmt corresponding to the curve that the host vehicle is about to enter. The ECU 10 maintains the state where the target value spt is below the upper limit value splmt until the host vehicle exits the curve.

[0025] Incidentally, for example, when a tall object OB (such as a building or a signboard) is installed near the inner peripheral edge of the curve C, the visibility of the front region (the region on the tip side of the curve C) may deteriorate. In this case, the driver's sense of uneasiness increases. When the host vehicle enters the curve C (t ≦ tth) and travels through the curve C (hereinafter referred to as the "specific scene") while the speed sp0 of the host vehicle is automatically adjusted by the speed adjustment function, if the visibility of the front region is poor, there is a high possibility that the speed sp0 of the host vehicle will be maintained at a lower speed than normal (when the visibility of the front region is good). Therefore, as described below, the ECU 10 determines the quality of the visibility of the front region based on the information acquired from the camera 21 in the above specific scene, and adjusts the target value spt according to the result.

[0026] Specifically, as shown in FIG. 2(A), when there is no object OB that reduces the recognition accuracy (recognition accuracy by the camera 21) of at least a part of the curve, the ECU 10 acquires, as the first curve range C1, the range (lateral size (width w1) of the range recognizable as the curve C) that is assumed to enter the angle of view AOV of the camera 21 (first process). Further, as shown in FIG. 2(B), the ECU 10 acquires, as the second curve range C2, the range (width w2) recognized as the curve C in the image obtained by the camera 21 shooting the foreground (second process). Next, the ECU 10 determines that the visibility of the front region is good when the ratio of the second curve range C2 to the first curve range C1 exceeds the threshold value. Specifically, the ECU 10 determines that the visibility of the front region is good when the width w2 is larger than the value obtained by subtracting a predetermined margin Δw from the width w1 (w2 > w1 - Δw). In this case, the ECU 10 assigns "1" to the coefficient k. On the other hand, when the ECU 10 does not determine that the visibility of the front region is good (w2 ≦ w1 - Δw), the ECU 10 assigns a predetermined value κ (for example, "0.5") smaller than "1" to the coefficient k (third process).

[0027] Next, referring to Figure 3, we will describe the program PR1 executed by the CPU 10a of the ECU 10 (hereinafter simply referred to as "CPU") to realize the speed adjustment function described above. When the speed adjustment function is enabled, the ECU 10 executes program PR1 at a predetermined interval.

[0028] (Program PR1) The CPU starts executing Program PR1 from step 100 and proceeds to step 101.

[0029] In step 101, the CPU tentatively determines the target value spt. In this step, the CPU tentatively determines the target value spt assuming that the vehicle is traveling on a straight road. That is, if there is no preceding vehicle V1, the CPU tentatively determines the set value spset as the target value spt. On the other hand, if there is a preceding vehicle V1, the CPU tentatively determines the target value spt such that the distance D between vehicles remains greater than or equal to the threshold Dth, and the vehicle follows the preceding vehicle V1. Next, the CPU proceeds to step 102.

[0030] In step 102, the CPU determines whether the time t until the vehicle enters the curve is less than or equal to the threshold tth, or whether the vehicle is currently traveling on a curve (whether the current scene corresponds to a specific scene). If the CPU determines that the current scene corresponds to a specific scene (102: Yes), it proceeds to step 103. On the other hand, if the CPU does not determine that the current scene corresponds to a specific scene (102: No), it proceeds to step 108.

[0031] In step 103, the CPU determines whether the target value spt (the tentatively determined value) exceeds the upper limit splmt. If the CPU determines that the target value spt exceeds the upper limit splmt (103: Yes), it proceeds to step 104. On the other hand, if the CPU does not determine that the target value spt exceeds the upper limit splmt (103: No), it proceeds to step 105.

[0032] In step 104, the CPU modifies the target value spt. That is, the CPU assigns an upper limit value splmt to the target value spt (the tentatively determined value). The CPU then proceeds to step 105.

[0033] In step 105, the CPU obtains the first curve range C1 and proceeds to step 106.

[0034] In step 106, the CPU obtains the second curve range C2 and proceeds to step 107.

[0035] In step 107, the CPU determines whether the visibility in the forward area is good or bad based on the first curve range C1(w1) and the second curve range C2(w2). If the CPU determines that the visibility in the forward area is good (w2>w1-Δw) (107:Yes), the process proceeds to step 108. Alternatively, the CPU determines whether the visibility in the forward area is good or bad. If the CPU does not determine that the visibility in the forward area is good (107:No), the process proceeds to step 109.

[0036] In step 108, the CPU assigns "1" to the coefficient k and proceeds to step 110.

[0037] In step 109, the CPU assigns a predetermined value κ (<1) to the coefficient k and proceeds to step 110.

[0038] In step 110, the CPU modifies the target value spt. Specifically, the CPU obtains the value obtained by multiplying the target value spt by the coefficient k as the target value spt (modified). Next, the CPU proceeds to step 111.

[0039] In step 111, the CPU controls the drive unit and other components so that the measured value of speed sp0 matches the target value spt (defensive). Next, the CPU proceeds to step 112, in which step 112, the execution of program PR1 is terminated.

[0040] (Effect) When driving through curve C, the driving support device 1 determines the visibility of the area ahead (the area at the tip of the curve) based on the range of curve C that is expected to be within the field of view AOV of camera 21 (first curve range C1) and the range of curve C in the image actually acquired by camera 21 (second curve range C2). In other words, in this embodiment, map information is not used when determining the visibility of the area ahead at curve C. Therefore, according to this embodiment, good accuracy in determining the visibility of the area ahead is maintained.

[0041] 1…Driving assistance system, 10…ECU, 20…On-board sensor, 30…Drive system, 40…Braking system

Claims

[Claim 1] A driver assistance system comprising a processor configured to set a target value for the vehicle's speed and to control various devices of the vehicle so that the measured value of the vehicle's speed matches the target value, Equipped with a camera to acquire images of the area in front of the vehicle, The aforementioned processor, A first process involves acquiring the range that is expected to be within the camera's field of view when the vehicle is traveling on a curve, provided that there are no objects that reduce the recognition accuracy of at least a part of the curve, as the first curve range. A second process involves obtaining the range of the acquired image that can be recognized as the curve as the second curve range, A third process involves determining the visibility of the forward area based on the ratio of the second curve range to the first curve range, and adjusting the target value so that the vehicle's speed when visibility is not determined to be good is lower than the speed when visibility is determined to be good. A driver assistance device configured to enable the following.

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