Patent Description:
There is a conventionally known invention in which a host vehicle is made to automatically follow a preceding vehicle (Patent Literature <NUM>). The invention disclosed in Patent Literature <NUM> detects the number of departure requests when the host vehicle is stopped due to waiting for a traffic signal, and sets a departure permission period according to the number of detected departure requests.

Patent Literature <NUM> describes a start assist system for motor vehicles including a long-range located system such as a radar system for determining the location of vehicles travelling ahead and a near-range locating system such as an ultrasonic system for determining the location of objects directly ahead of the host vehicle. Depending on a result of detection by the near-range locating system, an automatic travel control of a host vehicle so as to follow a preceding vehicle after a stop is either initiated or suppressed.

Patent Literature <NUM> describes an automatic travel control device for a vehicle suitable for travel control from high-speed travel to stop. For this purpose, both a long-distance radar and a short distance sensor are provided. The short distance sensor is capable of detecting an object in a wider range in a horizontal direction compared to the long-distance radar.

Patent Literature <NUM> describes a follow-up start control device for a vehicle that is configured to detect a stop and the start of a preceding vehicle. A follow-up automatic start control is executed or suppressed depending on a permission time that is set in accordance with a category of the road. A category of the road may be estimated when the presence of traffic jam is determined.

When the host vehicle departs following the preceding vehicle from a stopped state, it is required to detect an object that may enter in front of the host vehicle.

The present invention has been made in view of the above problem, and a purpose of the present invention is to provide a driving assistance method and a driving assistance device capable of detecting an object that may enter in front of the host vehicle, in an improved manner.

The present invention makes it possible to detect an object that may enter in front of the host vehicle, in an improved manner.

In the drawings, the same parts are denoted by the same reference numerals and the description thereof is omitted.

A configuration example of a driving assistance device <NUM> will be described with reference to <FIG>. The driving assistance device <NUM> is installed in a host vehicle provided with automatic driving functions. The automatic driving functions include ACC (adaptive cruise control), lane keeping, auto lane change, auto parking, and the like. In the present embodiment, the driving assistance device <NUM> is mainly used for the ACC. The ACC is an automatic driving function that automatically controls the acceleration and deceleration of a host vehicle with a speed set by a user as an upper limit, and makes the host vehicle follow a preceding vehicle. At this time, inter-vehicle control between the vehicles is also performed to maintain the distance between the vehicles according to the set speed.

Follow control includes control to make the host vehicle follow the preceding vehicle after detecting the preceding vehicle's departure when the host vehicle is stopped due to waiting for a traffic signal, a traffic jam, or the like.

As illustrated in <FIG>, the driving assistance device <NUM> includes a camera <NUM>, a radar <NUM>, a sonar <NUM>, a vehicle speed sensor <NUM>, a GPS receiver <NUM>, a switch <NUM>, a controller <NUM>, a steering actuator <NUM>, an accelerator pedal actuator <NUM>, and a brake actuator <NUM>.

A plurality of cameras <NUM> are installed at the front, the lateral sides, and the rear of the host vehicle, and also installed at the side mirrors thereof. The camera <NUM> has an imaging element such as a charge-coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). The camera <NUM> detects objects existing around the host vehicle (pedestrians, bicycles, two-wheeled vehicles, other vehicles, and so on), and information about the surroundings of the host vehicle (marking lines, traffic lights, signs, crosswalks, intersections, and so on). The camera <NUM> outputs captured images to the controller <NUM>.

A plurality of radars <NUM> are installed at the front, the front-lateral sides, and the rear-lateral sides of the host vehicle. The radar <NUM> emits radio waves to objects around the host vehicle and measures the distance and the direction to the objects by measuring the reflected waves. The radar <NUM> outputs the measured data to the controller <NUM>.

The sonar <NUM> is installed at the front bumper or front grille. The sonar <NUM> emits ultrasonic waves and measures the reflected waves to determine the distance and the direction to objects in the vicinity of the host vehicle (e.g., about <NUM> to <NUM>). The sonar <NUM> outputs the measured data to the controller <NUM>.

The vehicle speed sensor <NUM> detects the speed of the host vehicle and outputs the detected speed to the controller <NUM>.

The GPS receiver <NUM> detects the position information of the host vehicle on the ground by receiving radio waves from satellites. The position information of the host vehicle detected by the GPS receiver <NUM> includes latitude information and longitude information. Note that the method of detecting the position information of the host vehicle is not limited to the GPS receiver <NUM>. For example, positions may be estimated using a method called odometry. Odometry is a method of estimating the position of the host vehicle by determining the amount of travel of the host vehicle and the direction of the host vehicle according to the rotation angle and the rotation angular speed of the host vehicle. The position where the GPS receiver <NUM> is installed is not particularly limited, and as an example, the GPS receiver <NUM> is installed on the instrument panel of the host vehicle. The GPS receiver <NUM> outputs the detected position information to the controller <NUM>.

A plurality of switches <NUM> are installed in the steering wheel. The plurality of switches <NUM> include a switch for selecting a radio channel, a switch for adjusting a sound volume, a switch for starting the ACC, a switch for adjusting speed controlled by the ACC, a switch for setting the distance between the vehicles when the ACC is being carried out, a switch for starting follow travel when the preceding vehicle departs, and the like. In the present embodiment, the switch <NUM> is described as a physical switch; however, the switch <NUM> is not limited to this physical switch. The switch <NUM> may be a virtual switch. When the switch <NUM> is a virtual switch, the switch <NUM> may be displayed on a touch panel used in a navigation device.

The controller <NUM> is an Electronic Control Unit (ECU) having a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory), and a CAN (controller area network) communication circuit. A computer program is installed in the controller <NUM> for causing the controller <NUM> to function as the driving assistance device <NUM>. By executing the computer program, the controller <NUM> functions as multiple information processing circuits provided in the driving assistance device <NUM>. Here, an example will be described in which the multiple information processing circuits provided in the driving assistance device <NUM> are realized by software. In addition, it is also possible to configure the information processing circuit by preparing dedicated hardware for executing each information processing described below. In addition, the multiple information processing circuits may be configured by individual hardware. The controller <NUM> includes a lane detection unit <NUM>, a preceding vehicle detection unit <NUM>, a follow travel unit <NUM>, a stop determination unit <NUM>, and a detection range setting unit <NUM> as the multiple information processing circuits.

The lane detection unit <NUM> detects a lane in which the host vehicle is traveling using the image acquired from the camera <NUM>. Specifically, the lane detection unit <NUM> extracts the marking lines from the image and detects the lane in which the host vehicle is traveling. The lane detection unit <NUM> may further detect the lane in which the host vehicle is traveling by adding the position information of the host vehicle.

The preceding vehicle detection unit <NUM> detects a preceding vehicle that is present in front of the host vehicle using the image acquired from the camera <NUM>. Further, the preceding vehicle detection unit <NUM> detects the distance between the host vehicle and the preceding vehicle, the relative speed of the preceding vehicle to the host vehicle, and the like by using the data acquired from the radar <NUM>. In the present embodiment, the preceding vehicle is defined as a vehicle traveling in the same lane as the lane in which the host vehicle is traveling.

The follow travel unit <NUM> controls the host vehicle such that the host vehicle travels by automatically following the preceding vehicle. Specifically, when the user switches on the switch to start the ACC, the follow travel unit <NUM> controls the steering actuator <NUM>, the accelerator pedal actuator <NUM>, and the brake actuator <NUM> to make the host vehicle follow the preceding vehicle with the speed set in advance by the user as the upper limit. At this time, the follow travel unit <NUM> also performs inter-vehicle control between the vehicles so as to maintain the distance between the vehicles according to the set speed. The user can also specify the distance between the vehicles.

When a preceding vehicle is not detected when the user switches on the switch to start the ACC, the follow travel unit <NUM> makes the host vehicle travel at a constant speed based on the set speed. In addition, when the speed is not set, the follow travel unit <NUM> can automatically make the host vehicle travel at up to the legal speed of the road where the host vehicle is currently traveling.

The stop determination unit <NUM> determines whether the host vehicle has stopped. Specifically, when the speed of the host vehicle measured by the vehicle speed sensor <NUM> is <NUM>/h, the stop determination unit <NUM> determines that the host vehicle has stopped.

The detection range setting unit <NUM> sets a detection range. In the present embodiment, the detection range is defined as a range in which the camera <NUM> detects an object that may interfere with the follow control. An object that may interfere with the follow control is a vehicle that is cutting in, in a case where the host vehicle is traveling. Assume a scenario in which another vehicle cuts in between the host vehicle and the preceding vehicle when the host vehicle is traveling following the preceding vehicle. In this scenario, the follow travel unit <NUM> decelerates the host vehicle and then makes the host vehicle follow the vehicle that has cut in. Alternatively, the follow travel unit <NUM> may stop the host vehicle and cancel the follow control.

An object that may interfere with the follow control is a pedestrian or a bicycle in a case where the host vehicle is stopped. It is possible to say that a pedestrian or a bicycle is an object that may enter in front of the host vehicle when the host vehicle is stopped.

Next, the detection range set by the detection range setting unit <NUM> will be described with reference to <FIG> and <FIG>. The scenario illustrated in <FIG> is a scenario in which a host vehicle <NUM> is automatically traveling following a preceding vehicle <NUM>. In this scenario, the detection range setting unit <NUM> sets a detection range R1. The detection range R1 is the area on the lane where the host vehicle <NUM> is to travel. The size of the detection range R1 will be described. The length of the detection range R1 in the vehicle width direction is the vehicle width W1 of the host vehicle <NUM> as illustrated in <FIG>. The length of the detection range R1 in the traveling direction is from the leading end of the host vehicle <NUM> to the leading end of the preceding vehicle <NUM>.

The size of the detection range R1 is not limited to that illustrated <FIG>. As illustrated by the detection range R2 in <FIG>, the length in the vehicle width direction may be the width W2 of the lane in which the host vehicle <NUM> is traveling. In addition, the length in the traveling direction may be from the leading end of the host vehicle <NUM> to the rear end of the preceding vehicle <NUM>.

The detection ranges R1 to R2 described in <FIG> are areas that are set when the host vehicle <NUM> is automatically traveling following the preceding vehicle <NUM>. Next, the detection range when the host vehicle <NUM> is stopped will be described with reference to <FIG>. The scenario illustrated in <FIG> is a scenario in which the preceding vehicle <NUM> and the host vehicle <NUM> are stopped due to waiting for a traffic signal. After the preceding vehicle <NUM> has stopped, the follow travel unit <NUM> automatically stops the host vehicle <NUM> when having determined that the distance between the vehicles is to be less than a predetermined value. At this time, the follow travel unit <NUM> maintains the stopped state.

When the host vehicle <NUM> is stopped, the detection range setting unit <NUM> extends the detection range in the vehicle width direction as compared with when the host vehicle <NUM> is traveling. The extended detection range is illustrated in <FIG> as R3. The detection range R3 illustrated in <FIG> is wider in the vehicle width direction than the detection range R1 illustrated in <FIG> or the detection range R2 illustrated in <FIG>. This enables the controller <NUM> to detect an object (pedestrian <NUM>) that may enter in front of the host vehicle <NUM> in a wider area when the host vehicle <NUM> is stopped, as compared with when the host vehicle <NUM> is traveling. In addition, the controller <NUM> can more quickly detect an object that may enter in front of the host vehicle when the host vehicle <NUM> is stopped, as compared with when the host vehicle <NUM> is traveling.

In a case where the controller <NUM> detects a pedestrian <NUM> in the detection range R3 when the host vehicle <NUM> is stopped, it is possible to limit the behavior of the host vehicle <NUM>. The details will be described later.

The size of the detection range R3 will be described. The length in the vehicle width direction is about two times the vehicle width of the host vehicle <NUM>. This length is determined by considering the margin for detecting a pedestrian <NUM> before the host vehicle <NUM> departs. Accordingly, two times is merely an example, and the present invention is not limited thereto. The length in the traveling direction is from the leading end of the host vehicle <NUM> to the leading end of the preceding vehicle <NUM>. The length in the vehicle width direction may be <NUM> and the length in the traveling direction may be <NUM> although these values are not particularly limited.

Next, in the scenario illustrated in <FIG>, the behavior of the host vehicle <NUM> when a pedestrian <NUM> is detected and not detected in the detection range R3 will be described. First, a case where a pedestrian <NUM> is not detected in the detection range R3 will be described. Even when the preceding vehicle <NUM> departs, the host vehicle <NUM> does not depart automatically. The host vehicle <NUM> does not depart automatically unless a user's departure instruction (follow departure instruction) is input. The follow departure instruction is input by operating a switch for starting follow travel or by operating an accelerator pedal. In a case where the follow travel unit <NUM> receives the follow departure instruction from the user when the preceding vehicle <NUM> departs, the follow travel unit <NUM> automatically causes the host vehicle <NUM> to depart.

Next, a case where a pedestrian <NUM> is detected in the detection range R3 will be described. In this case, even when the follow departure instruction is input from the user, the follow travel unit <NUM> prohibits the host vehicle <NUM> from departing following the preceding vehicle <NUM> while the pedestrian <NUM> is detected. Thereafter, when the pedestrian <NUM> is no longer detected in the detection range R3, the follow travel unit <NUM> may automatically cause the host vehicle <NUM> to depart.

According to the invention, when a pedestrian <NUM> is detected in the detection range R3, the follow travel unit <NUM> cancels the follow departure system. In this case, the host vehicle <NUM> does not automatically depart even when the follow departure instruction is input from the user and the pedestrian <NUM> is no longer detected in the detection range R3. Thus, when a pedestrian <NUM> is detected after the host vehicle <NUM> has stopped, the departure of the host vehicle <NUM> following the preceding vehicle is prevented in the area where the pedestrian <NUM> may pass in front of the host vehicle <NUM>. Further, since the user cannot use the follow departure system, the user has to manually make the host vehicle <NUM> depart. Thus, it is possible to make the host vehicle <NUM> depart in the state where the user is made to check ahead of the host vehicle <NUM>. The stopped state is maintained even when the follow departure system is cancelled.

Next, an operation example of the driving assistance device <NUM> will be described with reference to the flowchart of <FIG>.

In step S101, the stop determination unit <NUM> uses the speed of the host vehicle <NUM> measured by the vehicle speed sensor <NUM> to determine whether or not the host vehicle <NUM> has stopped. When the speed of the host vehicle <NUM> is <NUM>/h (YES in step S101), the processing proceeds to step S103. When the speed of the host vehicle <NUM> is not <NUM>/h (NO in step S101), the series of processing ends.

In step S103, the detection range setting unit <NUM> extends the detection range in the vehicle width direction as compared with when the host vehicle <NUM> is traveling (see <FIG>).

The processing proceeds to step S105, and when a pedestrian <NUM> is detected in the extended detection range R3 (YES in step S105), the follow travel unit <NUM> prohibits the host vehicle <NUM> from departing following the preceding vehicle <NUM>. That is, the follow travel unit <NUM> cancels the follow departure system. Meanwhile, when a pedestrian <NUM> is not detected in the extended detection range R3 (NO in step S105), the follow travel unit <NUM> automatically causes the host vehicle <NUM> to depart so as to follow the preceding vehicle <NUM> in accordance with the follow departure instruction from the user.

As described above, the driving assistance device <NUM> according to the present embodiment provides the following operational effect.

The detection range setting unit <NUM> sets the detection range of a sensor for detecting an object in front of the host vehicle <NUM>. When the host vehicle <NUM> is stopped, the detection range setting unit <NUM> extends the detection range in the vehicle width direction as compared with when the host vehicle <NUM> is traveling following the preceding vehicle <NUM> (see <FIG>). This enables the controller <NUM> to detect an object (pedestrian <NUM>) that may enter in front of the host vehicle <NUM> in a wider area when the host vehicle <NUM> is stopped, as compared with when the host vehicle <NUM> is traveling. In addition, the controller <NUM> can more quickly detect an object that may enter in front of the host vehicle when the host vehicle <NUM> is stopped, as compared with when the host vehicle <NUM> is traveling.

In addition, the detection range when the host vehicle <NUM> is traveling is smaller than that when the host vehicle <NUM> is stopped. Accordingly, when the host vehicle <NUM> is traveling, the controller <NUM> can prevent control that is based on an object (an adjacent vehicle that is traveling, a tree, a pedestrian walking on sidewalk, or the like) other than an object that may interfere with the follow control. An adjacent vehicle that is traveling means a vehicle traveling in a lane adjacent to the lane where the host vehicle <NUM> is traveling.

When an object is detected in a detection range extended in the vehicle width direction, the follow travel unit <NUM> prohibits the host vehicle <NUM> from departing following the preceding vehicle <NUM>. Thus, when a pedestrian <NUM> is detected after the host vehicle <NUM> has stopped, the departure of the host vehicle <NUM> following the preceding vehicle <NUM> is prevented in the area where the pedestrian <NUM> may pass in front of the host vehicle <NUM>. Further, since the user cannot use the follow departure system, the user has to manually make the host vehicle <NUM> depart. Thus, it is possible to make the host vehicle <NUM> depart in the state where the user is made to check ahead of the host vehicle <NUM>.

Note that the controller <NUM> may determine whether or not the host vehicle <NUM> is traveling on a limited-access road based on the position information of the host vehicle <NUM>. A limited-access road is defined in Japan as a road on which only vehicles designated by the road administrator are allowed to travel. Atypical limited-access road is an express highway. When it is determined that the host vehicle <NUM> is traveling on a limited-access road and in a case where an object is detected in a detection range extended in the vehicle width direction, the controller <NUM> may prohibit the host vehicle <NUM> from departing following the preceding vehicle <NUM>. The detection of a pedestrian <NUM> or a bicycle on a limited-access road where there are usually no pedestrians <NUM> or bicycles may indicate that incorrect position information has been recognized due to a decrease in the accuracy of the GPS receiver <NUM>. In such a case, the controller <NUM> prohibits the host vehicle <NUM> from departing following the preceding vehicle <NUM>, which improves the reliability of the system.

Although a description has been given in which the detection range setting unit <NUM> extends the detection range by using the stopping of the host vehicle <NUM> as a trigger, this is not necessarily limited to extending the detection range at the moment when the host vehicle <NUM> has stopped. That is, after the host vehicle <NUM> has stopped, the detection range setting unit <NUM> may not change the detection range until a predetermined time elapses, and the detection range setting unit <NUM> may extend the detection range after a predetermined time has elapsed. This is achieved by setting two modes (first mode and second mode) as modes for permitting the host vehicle <NUM> to depart following the preceding vehicle <NUM>.

The first mode and second mode will be described. The first mode is a mode in which the departure of the host vehicle <NUM> following the preceding vehicle <NUM> is permitted in a case where the preceding vehicle <NUM> has departed before a first predetermined time elapses after the host vehicle <NUM> has stopped. The second mode is a mode in which the departure of the host vehicle <NUM> following the preceding vehicle <NUM> is permitted in a case where the preceding vehicle <NUM> has departed before a second predetermined time longer than the first predetermined time elapses. One example of the first predetermined time is <NUM> seconds and one example of the second predetermined time is <NUM> seconds. The first and second modes are set by the controller <NUM>. The detection range setting unit <NUM> does not change the detection range in the first mode, and may extend the detection range in the second mode.

A specific example will be described with reference to <FIG>. Scenario <NUM> illustrated in <FIG> is a scenario from when the host vehicle <NUM> has stopped until the first predetermined time (<NUM> seconds) elapses. That is, in scenario <NUM>, the host vehicle <NUM> is in the first mode. As illustrated in <FIG>, the detection range setting unit <NUM> does not change the detection range R1 in the first mode. Scenario <NUM> illustrated in <FIG> is a scenario from when the first predetermined time (<NUM> seconds) has elapsed until the second predetermined time (<NUM> seconds) elapses. That is, in scenario <NUM>, the host vehicle <NUM> is in the second mode. As illustrated in <FIG>, the detection range setting unit <NUM> extends the detection range R1 in the vehicle width direction in the second mode (the extended detection range is illustrated as R3).

The second mode has a departure permission time longer than that of the first mode. When the departure permission time is extended, the stopped time is also extended. Accordingly, in the second mode, the detection range is extended in the vehicle width direction, which makes it easier to detect an object. When the preceding vehicle <NUM> does not depart even after the second predetermined time has elapsed, the follow travel unit <NUM> cancels the follow departure system.

The detection range set by the detection range setting unit <NUM> in the present embodiment is the detection range of the camera <NUM>. An object detected by the camera <NUM> is at least either one of a pedestrian <NUM> and a bicycle. By limiting the means for detecting a pedestrian <NUM> or a bicycle in the detection range R3 extended in the vehicle width direction to the camera <NUM>, it is possible to exclude other vehicles in an adjacent lane near the lane in which the host vehicle <NUM> is traveling from being detection targets.

The controller <NUM> may detect a pedestrian <NUM> or a bicycle based on a change in the rear end of the preceding vehicle <NUM> shown in the camera image. When a pedestrian <NUM> or a bicycle passes in front of the host vehicle <NUM>, a change occurs in the image which shows the rear end thereof. When the image of the rear end has changed in this way, the controller <NUM> may determine that a pedestrian <NUM> or a bicycle is present. This enables the controller <NUM> to detect a pedestrian <NUM> or a bicycle whose shape is difficult to recognize as an object.

Each of the functions described in the above embodiment may be implemented by one or more processing circuits. The processing circuit includes a programmed processing device such as a processing device including an electrical circuit. The processing circuit also includes devices such as application specific integrated circuits (ASIC) arranged to perform the described functions and circuit components.

As described above, although the embodiment of the present invention has been described, it should not be understood that the arguments and drawings forming part of this disclosure are intended to limit the present invention. Various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art from this disclosure.

In the above embodiment, the sensor for detecting an object in the detection range set by the detection range setting unit <NUM> is described as the camera <NUM>; however, the sonar <NUM> may be added in addition to the camera <NUM>. The detection target of the camera <NUM> is a pedestrian <NUM> or a bicycle while the detection target of the sonar <NUM> is not particularly limited. The method of how the sonar <NUM> detects an object will be described. When the host vehicle <NUM> is stopped, in a case where the distance information in the lane where the host vehicle <NUM> is stopped changes by more than a predetermined value, it is determined that an object has been detected. It may also be determined that an object has been detected when the distance information suddenly changes. The sonar <NUM> is used only when the host vehicle <NUM> is stopped.

Claim 1:
A driving assistance method including a controller (<NUM>) which controls a host vehicle (<NUM>) such that the host vehicle (<NUM>) automatically travels following a preceding vehicle (<NUM>) which is in front of the host vehicle (<NUM>), wherein
the controller (<NUM>) sets a detection range of a sensor for detecting an object in front of the host vehicle (<NUM>), characterized in that
when the host vehicle (<NUM>) is stopped, the controller (<NUM>) extends the detection range in a vehicle width direction as compared with when the host vehicle (<NUM>) is traveling following the preceding vehicle (<NUM>), and
when an object other than vehicles is detected in the detection range extended in the vehicle width direction, the controller (<NUM>) cancels a system in which the host vehicle (<NUM>) departs following the preceding vehicle (<NUM>).