Patent Description:
An invention to cause a host vehicle to autonomously follow a preceding vehicle is known from the prior art (Patent Document <NUM>). In the invention disclosed in Patent Document <NUM>, when a host vehicle is stopped at a traffic light, the number of start requests is detected, and a start approval period is set in accordance with the detected number of start requests. Patent Document <NUM> discloses a driving assist method using a controller that uses a sensor to detect another vehicle that cuts in front of a host vehicle in a lane in which the host vehicle is traveling, comprising: setting, by the controller, a detection field of the sensor in front of the host vehicle.

When the host vehicle is stopped, it is desired to detect vehicles that may cut in front of the host vehicle.

In view of the problem described above, an object of the present invention is to provide a driving assist method and a driving assist device that are capable of detecting vehicles that may cut in front of the host vehicle when the host vehicle is stopped.

In a driving assist method according to one aspect of the present invention, the detection field of a sensor is set in front of a host vehicle; when the host vehicle is traveling, it is determined that another vehicle has cut in front of the host vehicle if the degree to which the other vehicle has entered into the detection field exceeds or equals a first prescribed value, and when the host vehicle is stopped, it is determined that the other vehicle has cut in front of the host vehicle if the degree exceeds or equals a second prescribed value that is smaller than the first prescribed value. In this method, the controller:.

By means of the present invention, it becomes possible to detect vehicles that may cut in front of a host vehicle when the host vehicle is stopped.

An embodiment of the present invention is described below with reference to the drawings. In the descriptions of the drawings, identical parts have been assigned the same reference numerals, and their descriptions have been omitted.

A configuration example of a driving assist device <NUM> will be described with reference to <FIG>. The driving assist device <NUM> is mounted on a host vehicle equipped with an autonomous driving function. The autonomous driving function includes ACC (Adaptive Cruise Control), lane keeping, automatic lane change, automatic parking, and the like, but in the present embodiment, the driving assist device <NUM> is primarily used for ACC. ACC is an autonomous driving function that automatically controls the acceleration/deceleration of a host vehicle, with the speed set in advance by a user as the upper limit, thereby causing the host vehicle to follow a preceding vehicle. Inter-vehicular distance control is also carried out so as to maintain an inter-vehicular distance corresponding to the speed set at this time.

Following control includes control for causing the host vehicle to follow a preceding vehicle after detecting the start of the preceding vehicle, when the host vehicle is stopped due to a traffic congestion, waiting for a traffic light, or the like.

As shown in <FIG>, the driving assist device <NUM> comprises camera <NUM>, radar <NUM>, sonar <NUM>, vehicle speed sensor <NUM>, GPS receiver <NUM>, switch <NUM>, controller <NUM>, steering actuator <NUM>, accelerator pedal actuator <NUM>, and brake actuator <NUM>.

A plurality of the cameras <NUM> are provided on the front, sides, rear, sideview mirrors, and the like, of the host vehicle. The camera <NUM> comprises an imaging element, such as a CCD (charge-coupled device), CMOS (complementary metal oxide semiconductor), and the like. The camera <NUM> detects objects in the vehicle surroundings (pedestrians, bicycles, two-wheeled vehicles, other vehicles, and the like) as well as information pertaining to the vehicle surroundings (road boundary lines, traffic lights, signs, pedestrian crossings, intersections, and the like). The camera <NUM> outputs captured images to the controller <NUM>.

A plurality of the radars <NUM> are provided on the front, sides, rear, etc., of the host vehicle. The radar <NUM> emits radio waves toward an object in the periphery of the host vehicle and measures the reflected waves, thereby measuring the distance and direction to the object. The radar <NUM> outputs the measurement data to the controller <NUM>.

The sonar <NUM> is installed on the front bumper or the front grill. The sonar <NUM> emits ultrasonic waves and measures the reflected waves, thereby measuring the direction of and distance to an object in the vicinity (for example, about <NUM>-<NUM>) of the host vehicle. The sonar <NUM> outputs 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> receives radio waves from a satellite to detect location information of the host vehicle on the ground. The location information of the host vehicle detected by the GPS receiver <NUM> includes latitude and longitude information. However, the method for detecting the host vehicle's location information is not limited to the use of a GPS receiver <NUM>. For example, the location may be estimated using a method called odometry. Odometry is a method for estimating the host vehicle position by calculating the amount and direction of movement of the host vehicle in accordance with the rotation angle and the rotational angular velocity of the host vehicle. The location where the GPS receiver <NUM> is installed is not particularly limited, but the GPS receiver <NUM> may be installed, for example, in the instrument panel of the host vehicle. The GPS receiver <NUM> outputs the detected position information to the controller <NUM>.

A plurality of the switches <NUM> are installed on the steering wheel. The plurality of switches <NUM> include a switch for selecting a radio channel, a switch for adjusting the volume, a switch for activating the ACC, a switch for adjusting the speed controlled by means of the ACC, a switch for setting the inter-vehicular distance when the ACC is activated, a switch for activating following travel when a preceding vehicle starts, and the like. The switches <NUM> are described as physical switches in the present embodiment, but the present invention is not limited thereto. The switches <NUM> may be virtual switches. If the switches <NUM> are virtual switches, the switches <NUM> may be displayed on a touch panel that is used for 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), a CAN (Controller Area Network) communication circuit, and the like. A computer program is installed in the controller <NUM> to cause it to function as the driving assist device <NUM>. By executing the computer program, the controller <NUM> functions as a plurality of information processing circuits included in the driving assist device <NUM>. Here, an example is shown in which the plurality of information processing circuits included in the driving assist device <NUM> is realized in software, but the information processing circuits may, of course, comprise dedicated hardware for executing each of the information processes shown below. In addition, the plurality of information processing circuits may be realized in discrete hardware. The controller <NUM> comprises, as the plurality of information processing circuits, a lane detection unit <NUM>, a preceding vehicle detection unit <NUM>, a following travel unit <NUM>, a stop determination unit <NUM>, and a cut-in determination unit <NUM>.

The lane detection unit <NUM> uses an image acquired by the camera <NUM> to detect the lane in which the host vehicle is traveling. Specifically, the lane detection unit <NUM> extracts partition lines from the image and detects the lane in which the host vehicle travels. The lane detection unit <NUM> may further add the position information of the host vehicle in order to detect the lane in which the host vehicle is traveling.

The preceding vehicle detection unit <NUM> uses an image acquired by the camera <NUM> to detect the presence of a preceding vehicle in front of the host vehicle. In addition, the preceding vehicle detection unit <NUM> uses data acquired from the radar <NUM> to detect the inter-vehicular distance between the host vehicle and the preceding vehicle, the relative speed of the preceding vehicle with respect to the host vehicle, etc. In the present embodiment, a preceding vehicle is defined as a vehicle traveling in the same lane as the lane in which the host vehicle is traveling.

The following travel unit <NUM> controls the host vehicle such that the host vehicle travels autonomously, following a preceding vehicle. Specifically, when the user turns on a switch for activating the ACC, the following travel unit <NUM> controls the steering actuator <NUM>, the accelerator pedal actuator <NUM>, and the brake actuator <NUM>, thereby causing the host vehicle to follow the preceding vehicle with the speed set in advance by the user as the upper limit. At this time, the following travel unit <NUM> also carries out inter-vehicular distance control so as to maintain an inter-vehicular distance that corresponds to the speed set at this time. The user may specify the inter-vehicular distance.

If a preceding vehicle is not detected when the user turns on a switch for activating the ACC, the following travel unit <NUM> causes the host vehicle to carry out constant speed travel at a set speed. If a speed is not set, the following travel unit <NUM> may cause the host vehicle to travel autonomously, with the legal speed limit of the road on which the host vehicle is currently traveling as the upper limit.

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

The cut-in determination unit <NUM> determines whether another vehicle has cut in between the preceding vehicle and the host vehicle. The cut-in determination unit <NUM> determines cut-ins in a plurality of scenarios. For example, the cut-in determination unit <NUM> determines cut-ins between the host vehicle and a preceding vehicle when the host vehicle is autonomously traveling and following the preceding vehicle. In addition, the cut-in determination unit <NUM> determines cut-ins ahead of the host vehicle when the host vehicle is stopped at a traffic light, etc. Scenarios in which the host vehicle is stopped are twofold. One is a scenario in which the host vehicle is stopped behind a preceding vehicle. This scenario occurs in congested traffic, while waiting at a traffic light at an intersection, etc. The other is a scenario in which the host vehicle is stopped in a state in which there is no preceding vehicle. This scenario occurs when the host vehicle is stopped at the front of the line at an intersection.

One example of a determination method of the cut-in determination unit <NUM> will be described with reference to <FIG>. The scenario of <FIG> shows a host vehicle <NUM> traveling autonomously and following a preceding vehicle <NUM>. In addition, the scenario of <FIG> depicts an expressway, but is also applicable to roads other than expressways. R1 in <FIG> indicates an area for detecting another vehicle that cuts in between the preceding vehicle <NUM> and the host vehicle <NUM>. Area R1 indicates the detection field of the camera <NUM>. The size of area R1 will be described. The width in the vehicle width direction of area R1 is the vehicle width W1 of the host vehicle <NUM>, as shown in <FIG>. The length in the direction of travel of area R1 is measured from the front end of the host vehicle <NUM> to the rear end of the preceding vehicle <NUM>.

P1-P5 in <FIG> indicate the positions of another vehicle <NUM>. When the other vehicle <NUM> from position P1 cuts in between the host vehicle <NUM> and the preceding vehicle <NUM>, the movement trajectory of the other vehicle <NUM> will be described by the gentle curve indicated by positions P2 to P5. As the other vehicle <NUM> proceeds from position P4 to position P5, the rear surface of the other vehicle <NUM> enters area R1. <NUM> in <FIG> indicates the part of the rear surface of the other vehicle <NUM> that has entered area R1 (hereinafter referred to as rear surface <NUM>). The rear surface <NUM> is photographed by the camera <NUM>. The cut-in determination unit <NUM> calculates the area of the rear surface <NUM> acquired by the camera <NUM>. If the area of the rear surface <NUM> exceeds or equals a prescribed value, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in between the preceding vehicle <NUM> and the host vehicle <NUM>. In other words, unless the area of the rear surface <NUM> exceeds or equals the prescribed value, the cut-in determination unit <NUM> determines that a vehicle has not cut in between the preceding vehicle <NUM> and the host vehicle <NUM>.

A rear vehicle surface in the present embodiment is defined as a projected view of the vehicle as seen from behind. The prescribed value (third prescribed value) used for comparison with the area of the rear surface <NUM> is obtained by experimentation, simulation, etc..

The size of area R1 is not limited to that shown in <FIG>. For example, as indicated by area R2 in <FIG>, the width in the vehicle width direction may be the width W2 of the lane in which the host vehicle <NUM> is traveling. In this case, because the time it takes for the area of the rear surface <NUM> to exceed or equal the prescribed value is reduced, the cut-in determination unit <NUM> can determine a cut-in of the other vehicle <NUM> earlier as compared with the scenario shown in <FIG>. Specifically, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P5 in the scenario shown in <FIG>, whereas the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P4 in the scenario shown in <FIG>.

For example, as indicated by area R3 in <FIG>, the width in the vehicle width direction may be the width W3, which is greater than the width W2. The width W3 is set in consideration of a margin. In the scenario shown in <FIG>, because the time it takes for the area of the rear surface <NUM> to exceed or equal the prescribed value is further reduced, the cut-in determination unit <NUM> can determine a cut-in of the other vehicle <NUM> even earlier as compared with the scenario shown in <FIG>. Specifically, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P4 in the scenario shown in <FIG>, whereas the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P3 in the scenario shown in <FIG>.

A process carried out when a cut-in of the other vehicle <NUM> is detected in the scenarios shown in <FIG> will be described next. If a cut-in of the other vehicle <NUM> is detected, the controller <NUM> issues a warning to the user riding in the host vehicle <NUM>, decelerates the host vehicle <NUM>, or the like. Alternatively, the controller <NUM> may cancel the following control. The warning may be by means of voice or a display on a monitor.

In the present embodiment, determining that the other vehicle <NUM> has cut in is synonymous with detecting a cut-in of the other vehicle <NUM>.

One example of a method for determining a cut-in when the host vehicle <NUM> is stopped will now be described with reference to <FIG>. In the scenario shown in <FIG>, the preceding vehicle <NUM> and the host vehicle <NUM> are stopped at a traffic light. After the preceding vehicle <NUM> stops and it is determined that the inter-vehicular distance would become less than or equal to a prescribed value, the following travel unit <NUM> automatically stops the host vehicle <NUM>. At this time, the following travel unit <NUM> maintains the stopped state.

When the host vehicle <NUM> is stopped, the cut-in determination unit <NUM> determines cut-ins by means of a different method than one used when the host vehicle <NUM> is traveling. Specifically, when the host vehicle <NUM> is traveling, the cut-in determination unit <NUM> uses the area of the rear surface <NUM> of the other vehicle <NUM>, whereas when the host vehicle <NUM> is stopped, the cut-in determination unit <NUM> uses the area of a side surface <NUM> of the other vehicle <NUM>. P1-P4 in <FIG> indicate the positions of the other vehicle <NUM>. If the other vehicle <NUM> from position P1 cuts in between the host vehicle <NUM> and the preceding vehicle <NUM>, the movement trajectory of the other vehicle <NUM> will be described by the curve indicated by positions P2 to P4. When the movement trajectory (curve) of the other vehicle <NUM> shown in <FIG> and the movement trajectory (curve) of the other vehicle <NUM> shown in <FIG> are compared, the curvature of the curve of <FIG> is greater. This is because the inter-vehicular distance between the host vehicle <NUM> and the preceding vehicle <NUM> is relatively long during travel, and thus the angle at which the other vehicle <NUM> enters into the host vehicle's lane (the lane in which the host vehicle <NUM> is traveling) is small; whereas when the inter-vehicular distance is short during the stopped state, that the angle at which the other vehicle <NUM> enters into the host vehicle's lane is greater.

As a result, the side surface <NUM> of the other vehicle <NUM> entering area R1 is more easily detected by the camera <NUM>. In addition, the side surface <NUM> of the other vehicle <NUM> enters area R1 before the rear surface <NUM>. Thus, in the present embodiment, when the host vehicle <NUM> is stopped, a cut-in is determined using the area of the side surface <NUM> of the other vehicle <NUM>. It is thus possible to detect a cut-in earlier as compared with the case in which a cut-in is determined using the rear surface <NUM>. Because the side surface <NUM> is used when the host vehicle <NUM> is stopped, it is possible to reduce erroneous detection of the side surface of a vehicle that travels along an adjacent lane on a curve. An adjacent lane means a lane adjacent to the lane in which the host vehicle <NUM> travels.

In the scenario shown in <FIG>, if the other vehicle <NUM> proceeds from position P3 to position P4, the part of the side surface <NUM> of the other vehicle <NUM> enters area R1. The side surface <NUM> is photographed by the camera <NUM>. The cut-in determination unit <NUM> calculates the area of the side surface <NUM> acquired from the camera <NUM>. If the area of the side surface <NUM> exceeds or equals a prescribed value, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in between the preceding vehicle <NUM> and the host vehicle <NUM>.

The side surface of a vehicle in the present embodiment is defined as a projected view of the vehicle as seen from side. The prescribed value (fourth prescribed value) used for comparison with the area of the side surface <NUM> may be the same value as the prescribed value (third prescribed value) used for comparison with the area of the rear surface <NUM> or a different value. The definition of the size of area R1 shown in <FIG> is the same as the definition of the size of area R1 shown in <FIG>.

The size of area R1 is not limited that shown in <FIG>. For example, as indicated by area R2 in <FIG>, the width in the vehicle width direction may be the width W2 of the lane in which the host vehicle <NUM> is traveling. In this case, because the time it takes for the area of the side surface <NUM> to exceed or equal the prescribed value is reduced, the cut-in determination unit <NUM> can determine a cut-in of the other vehicle <NUM> earlier as compared with the scenario shown in <FIG>. Specifically, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P4 in the scenario shown in <FIG>, whereas the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P3 in the scenario shown in <FIG>.

For example, as indicated by area R3 in <FIG>, the width in the vehicle width direction may be the width W3, which is greater than the width W2. The width W3 is set in consideration of a margin. In the scenario shown in <FIG>, because the time it takes for the area of the side surface <NUM> to exceed or equal the prescribed value is further reduced, the cut-in determination unit <NUM> can determine a cut-in of the other vehicle <NUM> even earlier as compared with the scenario shown in <FIG>. Specifically, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P3 in the scenario shown in <FIG>, whereas the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in at position P2 in the scenario shown in <FIG>.

The process that is carried out when a cut-in of the other vehicle <NUM> is detected in the scenarios shown in <FIG> will now be described. If a cut-in of the other vehicle <NUM> is detected, the following travel unit <NUM> prohibits a following start even if the user inputs a following start instruction. In this case, because the user cannot use the following start system, it is necessary for the user to manually start the host vehicle <NUM>. It is thereby possible to start the host vehicle <NUM> after the user has checked the area ahead. The following travel unit <NUM> may issue a warning to the user when a following start is prohibited. When the preceding vehicle <NUM> starts and a cut-in of the other vehicle <NUM> is not detected, the following travel unit <NUM> automatically starts the host vehicle <NUM> in accordance with the user's following start instruction.

One operation example of the driving assist device <NUM> will now 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> in order to determine whether the host vehicle <NUM> has stopped. If the speed of the host vehicle <NUM> is <NUM>/h (YES is Step S101), the process proceeds to Step S103. When the speed of the host vehicle <NUM> is not <NUM>/h (NO in Step S101), the process proceeds to Step S109.

In Step S103, the cut-in determination unit <NUM> calculates the area of the side surface <NUM> of the other vehicle <NUM> acquired from the camera <NUM>. If the area of the side surface <NUM> exceeds or equals a prescribed value (YES in Step S103), the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in between the host vehicle <NUM> and the preceding vehicle <NUM>. The process then proceeds to Step S107, and the following travel unit <NUM> prohibits a following start. If, on the other hand, the area of the side surface <NUM> is smaller than the prescribed value (NO in Step S103), the cut-in determination unit <NUM> determines that a cut-in has not taken place. The process then proceeds to Step S105, and the following travel unit <NUM> automatically starts the host vehicle <NUM>.

In Step S109, the cut-in determination unit <NUM> calculates the area of the rear surface <NUM> of the other vehicle <NUM> acquired from the camera <NUM>. If the area of the rear surface <NUM> exceeds or equals a prescribed value (YES in Step S109), the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in between the host vehicle <NUM> and the preceding vehicle <NUM>. The process then proceeds to Step S113, and the controller <NUM> issues a warning to the user, decelerates the host vehicle <NUM>, or the like. If, on the other hand, the area of the rear surface <NUM> is smaller than the prescribed value (NO in Step S109), the cut-in determination unit <NUM> determines that a cut-in has not taken place. The process then proceeds to Step S111, and the following travel unit <NUM> causes the host vehicle <NUM> to follow the preceding vehicle <NUM>.

As described above, the following actions and effects can be achieved by means of the driving assist device <NUM> according to the present embodiment.

The controller <NUM> sets the detection field (areas R1-R3) of a sensor (camera <NUM>) for detecting another vehicle <NUM> between the host vehicle <NUM> and the preceding vehicle <NUM>. If the host vehicle <NUM> is traveling and following the preceding vehicle <NUM> and the area of the rear surface <NUM> of the other vehicle <NUM> detected within the detection field exceeds or equals a prescribed value, the controller <NUM> determines that the other vehicle <NUM> has cut in between the preceding vehicle <NUM> and the host vehicle <NUM>. The detection field is set between the host vehicle <NUM> and the preceding vehicle <NUM>.

If the host vehicle <NUM> is stopped and the area of the side surface <NUM> of the other vehicle <NUM> detected in the detection field exceeds or equals a prescribed value, the controller <NUM> determines that the other vehicle <NUM> has cut in between the preceding vehicle <NUM> and the host vehicle <NUM>. As described above, due to the difference in the characteristics between the traveling and stopped states (different angle of entry), when the host vehicle <NUM> is stopped, the side surface <NUM> of the other vehicle <NUM> entering the detection field is more easily detected by the camera <NUM>. In addition, the side surface <NUM> of the other vehicle <NUM> enters the detection field before the rear surface <NUM>. By determining a cut-in by means of the side surface <NUM>, it is possible to detect a cut-in more quickly when the host vehicle <NUM> is stopped as opposed to when the host vehicle <NUM> is traveling.

The controller <NUM> may determine whether the host vehicle <NUM> is on an automobiles-only road based on location information of the host vehicle <NUM>. An automobiles-only road is defined in Japan as a road dedicated for the exclusive use of automobiles on which only those automobiles designated by the road administrator are allowed to drive. A representative automobiles-only road is an expressway. The cut-in determination unit <NUM> may determine a cut-in only when it is determined that the host vehicle <NUM> is on an automobiles-only road. By determining cut-ins only on straight roads or curved roads of limited curvature, such as automobiles-only roads, erroneous cut-in determinations can be prevented.

If a cut-in of the other vehicle <NUM> is detected when the host vehicle <NUM> is traveling and following the preceding vehicle <NUM>, the controller <NUM> issues a warning to the user, decelerates the host vehicle <NUM>, or the like. If a cut-in of the other vehicle <NUM> is detected when the host vehicle <NUM> is stopped, the following travel unit <NUM> prohibits the host vehicle <NUM> from starting and following the preceding vehicle <NUM>. By means of the present embodiment, because a cut-in can be quickly detected, sudden braking is reduced. In addition, it is possible to prevent a following start.

Another example of a determination method of the cut-in determination unit <NUM> will be described.

When the host vehicle <NUM> is traveling and following the preceding vehicle <NUM>, the cut-in determination unit <NUM> may determine the presence or absence of a cut-in based on changes in the rear surface of the preceding vehicle <NUM> captured in a camera image. If the other vehicle <NUM> cuts in, part of the rear surface of the preceding vehicle <NUM> is obscured by the other vehicle <NUM> as seen by the camera <NUM>. As a result, a change in the image of the rear surface of the preceding vehicle <NUM> occurs. If a change in the image of the rear surface of the preceding vehicle <NUM> occurs, the cut-in determination unit <NUM> may determine that the other vehicle <NUM> has cut in between the preceding vehicle <NUM> and the host vehicle <NUM>.

If the host vehicle <NUM> is stopped behind the preceding vehicle <NUM> and the distance from the front end of the other vehicle <NUM> to the host vehicle <NUM> detected within the detection field of the camera <NUM> (areas R1-R3 shown in <FIG>) is less than or equal to a prescribed value, the cut-in determination unit <NUM> may determine that the other vehicle <NUM> has cut in between the preceding vehicle <NUM> and the host vehicle <NUM>. The distance from the front end of the other vehicle <NUM> to the host vehicle <NUM> means the shortest distance between the host vehicle <NUM> and the bumper of the other vehicle <NUM>. In addition, the prescribed value (fifth prescribed value) referred to here is different than the prescribed value (fourth prescribed value) that was used in comparisons with the side surface <NUM>. By make a determination using this distance, a cut-in can be quickly detected.

The cut-in determination unit <NUM> may determine a cut-in of the other vehicle <NUM> in accordance with the degree of entry of the other vehicle <NUM> into the detection field of the camera <NUM>. The degree of entry into the detection field is defined as the area of overlap of the other vehicle <NUM> with the detection field. The area of overlap of the other vehicle <NUM> with the detection field is defined as the area of overlap of the other vehicle <NUM> as seen directly overhead.

If the host vehicle <NUM> is traveling and it is determined that the degree of entry of the other vehicle <NUM> into the detection field exceeds or equals a prescribed value (first prescribed value), the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. In addition, if the host vehicle <NUM> is stopped and it is determined that the degree of entry of the other vehicle <NUM> into the detection field exceeds or equals a second prescribed value that is smaller than the first prescribed value, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. Specific examples will be described with reference to <FIG> and <FIG>.

Note position P5 in <FIG> and position P4 in <FIG>. The degree of entry of the other vehicle <NUM> into the detection field (area R1) at position P5 in <FIG> is about <NUM>% of the total area as seen from above. And the degree of entry of the other vehicle <NUM> into the detection field (area R1) at position P4 in <FIG> is approximately <NUM>% of the total area as seen from above. In Modified Example <NUM>, if the host vehicle <NUM> is traveling and it is determined that the degree of entry of the other vehicle <NUM> into the detection field (area R1) exceeds or equals the first prescribed value (<NUM>%, as one example), the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. On the other hand, if the host vehicle <NUM> is stopped and it is determined that the degree of entry of the other vehicle <NUM> into the detection field (area R1) exceeds or equals a second prescribed value (<NUM>%, as one example) that is smaller than the first prescribed value, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. The numerical values of <NUM>% and <NUM>% described above are merely examples, and no limitation thereto is implied. As long as the condition that the second prescribed value is smaller than the first prescribed value is satisfied, the numerical values of the first prescribed value and the second prescribed value may be any value.

By means of Modified Example <NUM>, it becomes possible to detect the other vehicle <NUM> that may cut in front of the host vehicle <NUM> when the host vehicle <NUM> is stopped. In addition, the threshold value for determining a cut-in of the other vehicle <NUM> is smaller when the host vehicle <NUM> is stopped as opposed to when the host vehicle <NUM> is traveling. That is, because the second prescribed value is smaller than the first prescribed value, a cut-in can be more quickly detected when the host vehicle <NUM> is stopped as opposed to when the host vehicle <NUM> is traveling. Setting the second prescribed value smaller than the first prescribed value is similarly applied in the above-described embodiment, Modified Example <NUM>, and Modified Example <NUM> described further below. That is, in the embodiment described above, the controller <NUM> sets the first prescribed value to the third prescribed value, which is the area of the rear surface of the other vehicle <NUM> detected with the detection field, and sets the second prescribed value to the fourth prescribed value, which is the area of the side surface of the other vehicle <NUM> detected within the detection field.

In the scenario of <FIG>, the length of area R1 was described as the distance in the direction of travel from the front end of the host vehicle <NUM> to the rear end of the preceding vehicle <NUM>. However, the length of area R1 is not limited thereto. As shown in <FIG>, the length of area R1 may be a distance in the direction of travel that does not reach the rear end of the preceding vehicle <NUM>. However, the length of area R1 is preferably greater than the distance in the direction of travel over which an emergency brake is applied by the autonomous driving function. It thus becomes possible to detect a cut-in before the emergency brake is applied.

The method for determining a cut-in when area R1 is as shown in <FIG> will now be described. The scenario shown in <FIG> depicts the scenario of <FIG> at a subsequent time. In the scenarios of <FIG>, the host vehicle <NUM> is traveling. As shown in <FIG>, when the host vehicle <NUM> is traveling and it is determined that the area of the rear surface of the other vehicle <NUM> detected within area R1 exceeds or equals a prescribed value (sixth prescribed value), the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. The area of the rear surface of the other vehicle <NUM> detected within area R1 means the area of overlap of the other vehicle <NUM> with area R1, as described in Modified Example <NUM>.

As shown in <FIG>, the length of area R1 in the direction of travel when the host vehicle <NUM> is stopped also may be a length that does not reach the rear end of the preceding vehicle <NUM>, in the same manner as in <FIG>. However, in <FIG>, as in <FIG>, the length of area R1 in the direction of travel is preferably greater than the distance over which the emergency brake is applied by the autonomous driving function. The method for determining a cut-in when area R1 is as shown in <FIG> will now be described. The scenario shown in <FIG> is the scenario shown in <FIG> at a subsequent time. In the scenarios of <FIG>, the host vehicle <NUM> is stopped. As shown in <FIG>, when the host vehicle <NUM> is stopped and it is determined that the area of the rear surface of the other vehicle <NUM> detected within area R1 exceeds or equals a seventh prescribed value that is smaller than the sixth prescribed value, the cut-in determination unit <NUM> determines that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. The area of the rear surface of the other vehicle <NUM> detected within area R1 means the area of overlap of the other vehicle <NUM> with area R1, as described in Modified Example <NUM>.

By means of Modified Example <NUM>, it becomes possible to detect when another vehicle <NUM> may cut in front of the host vehicle <NUM> when the host vehicle <NUM> is stopped. In addition, the threshold value for determining a cut-in of the other vehicle <NUM> is smaller when the host vehicle <NUM> is stopped as opposed to when the host vehicle <NUM> is traveling. That is, because the seventh prescribed value is smaller than the sixth prescribed value, a cut-in can be detected more quickly when the host vehicle <NUM> is stopped as opposed to when the host vehicle <NUM> is traveling.

Each of the functions described in the embodiments above may be implemented by means of one or more processing circuits. The processing circuits include programmed processing devices, such as processing devices including electronic circuits. Moreover, the processing circuits include devices such as circuit components and application-specific integrated circuits (ASIC) arranged to execute the described functions.

Various alternative embodiments, examples, and operating techniques should be apparent to those skilled in the art, in accordance with the invention as defined by the claims.

When the host vehicle <NUM> is stopped, lane markings (so-called white lines) may not be detected because of vehicles in the vicinity of the host vehicle <NUM>. In such cases, the controller <NUM> may set the detection field of the camera <NUM> using virtual lane markings based on past detection results. The lane width of the virtual lane markings may be the vehicle width of the host vehicle <NUM>, obtained by adding a margin to the vehicle width of the host vehicle <NUM>, or may be a width in accordance with the road type.

The cut-in determination unit <NUM> may determine a cut-in based on the area of the side surface of the other vehicle <NUM>. For example, when the host vehicle <NUM> is traveling and it is determined that the area of the side surface of the other vehicle <NUM> that overlaps in the detection field exceeds or equals a prescribed value (eighth prescribed value), it may be determined that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. In addition, when the host vehicle <NUM> is stopped and the area of the side surface of the other vehicle <NUM> that overlaps the detection field exceeds or equals a ninth prescribed value that is smaller than the eighth prescribed value, the cut-in determination unit <NUM> may determine that the other vehicle <NUM> has cut in front of the host vehicle <NUM>. As a result, it is possible to detect a cut-in more quickly when the host vehicle <NUM> is stopped as opposed to when the host vehicle <NUM> is traveling.

Claim 1:
A driving assist method using a controller that uses a sensor to detect another vehicle (<NUM>) that cuts in front of a host vehicle (<NUM>) in a lane in which the host vehicle (<NUM>) is traveling, comprising:
setting, by the controller, a detection field (R1) of the sensor in front of the host vehicle (<NUM>),
characterized by
determining, by the controller, that the other vehicle (<NUM>) has cut in front of the host vehicle (<NUM>) when the host vehicle (<NUM>) is traveling and a degree to which the other vehicle (<NUM>) has entered into the detection field (R1) exceeds or equals a first prescribed value, and
determining, by the controller, the other vehicle (<NUM>) has cut in front of the host vehicle (<NUM>) when the host vehicle (<NUM>) is stopped and the degree exceeds or equals a second prescribed value that is smaller than the first prescribed value;
wherein the controller
controls the host vehicle (<NUM>) to travel follow a preceding vehicle (<NUM>) that is ahead of the host vehicle (<NUM>),
sets the detection field (R1) of the sensor between the host vehicle (<NUM>) and the preceding vehicle (<NUM>),
sets the first prescribed value to a third prescribed value, which is an area of a rear surface (<NUM>) of the other vehicle (<NUM>) detected within the detection field (R1), and
sets the second prescribed value to a fourth prescribed value, which is an area of a side surface (<NUM>) of the other vehicle (<NUM>) detected within the detection field (R1).