Vehicle control device, vehicle control method, and vehicle control computer program

Abstract

To provide a vehicle controller capable of preventing a vehicle from deviating from its own lane on which the vehicle is traveling, without causing the vehicle's driver to feel insecure.SOLUTION: A vehicle controller includes a detection unit 31 that detects a lane defining line which defines an own lane on which a vehicle 10 travels, a calculation unit 32 that calculates a deviation index value, which represents a possibility that the vehicle 10 may deviate from the own lane, on the basis of a positional relationship between the lane defining line and vehicle 10, a control unit 33 that determines based on the deviation index value whether a predetermined condition for deviation is satisfied, and that, when the condition for deviation is satisfied, implements deviation prevention control for the vehicle 10 so as to prevent the vehicle 10 from deviating from the own lane, and an alteration unit 34 that alleviates the condition for deviation according to a manipulation performed by the driver of the vehicle 10 in order to prevent the vehicle 10 from deviating from the own lane before the predetermined condition for deviation is satisfied, and diminishes the control quantity of the vehicle 10 at the time of the implementation of deviation prevention control.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a vehicle control device, a vehicle control method, and a computer program for vehicle control. [Background technology]

[0002] Technology that automatically prevents a vehicle from departing from its lane while traveling (Lane Departure Prevention, LDP) is being researched (see Patent Document 1).

[0003] The cruise control device described in Patent Document 1 calculates an index value of the risk of the vehicle deviating from the road, and when the index value exceeds a threshold value, performs cruise control to reduce the risk of deviation by correcting the vehicle. When the driver performs a steering operation in a direction that reduces the risk of deviation, this cruise control device increases the control amount of the vehicle's corrective movement compared to when the driver does not perform a steering operation in a direction that reduces the risk. Furthermore, this cruise control device increases the control amount of the corrective movement by reducing the threshold value for the index value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2014-144745 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the above technology, the more the driver performs a steering operation to reduce the risk of lane departure, the greater the control amount of the vehicle's corrective motion, and therefore the amount of change in the behavior of the vehicle to continue traveling within its own lane, particularly the amount of change in the vehicle's orientation, increases. Therefore, in some cases, when lane departure prevention control is performed, the vehicle's orientation may change too much, which may cause the driver to feel uneasy.

[0006] Therefore, an object of the present invention is to provide a vehicle control device that can prevent the vehicle from deviating from the lane in which the vehicle is traveling without making the driver of the vehicle feel uneasy. [Means for solving the problem]

[0007] According to one embodiment, there is provided a vehicle control device that includes a detection unit that detects lane markings that define a lane in which the vehicle is traveling, a calculation unit that calculates a departure index value that indicates a possibility that the vehicle will deviate from the lane based on a positional relationship between the lane markings and the vehicle, a control unit that determines whether a predetermined departure condition is satisfied based on the departure index value and, if the departure condition is satisfied, executes departure prevention control on the vehicle to prevent the vehicle from deviating from the lane, and a change unit that relaxes the departure condition and reduces a control amount of the vehicle when the departure prevention control is executed in response to an operation by the driver of the vehicle to prevent the vehicle from deviating from the lane, which was performed before the predetermined departure condition was satisfied.

[0008] In this vehicle control device, it is preferable that the change unit tightens the departure conditions in response to a driver's operation to interrupt departure prevention control while departure prevention control is being executed, and increases the control amount of the vehicle when departure prevention control is being executed.

[0009] In addition, it is preferable that the modification unit increases a departure prevention operation count, which indicates the number of times that operation has been performed, by a predetermined amount each time an operation is performed to prevent the vehicle from deviating from the vehicle's lane, and when the value of the departure prevention operation count exceeds the predetermined number, relaxes the predetermined departure condition and reduces the amount of control of the vehicle when departure prevention control is executed.

[0010] In this case, it is preferable that the change unit changes the predetermined increase amount according to the situation around the vehicle when an operation to prevent the vehicle from departing from the own lane is performed.

[0011] According to another embodiment, there is provided a vehicle control method including: detecting lane markings that define a lane in which the vehicle is traveling; calculating a departure index value that indicates a possibility that the vehicle will deviate from the lane based on a positional relationship between the lane markings and the vehicle; determining whether a predetermined departure condition is satisfied based on the departure index value; and, if the departure condition is satisfied, executing departure prevention control on the vehicle to prevent the vehicle from deviating from the lane; and, in response to an operation by the driver of the vehicle to prevent the vehicle from deviating from the lane performed before the predetermined departure condition is satisfied, relaxing the departure condition and reducing a control amount of the vehicle when the departure prevention control is executed.

[0012] According to yet another embodiment, there is provided a computer program for controlling a vehicle, which causes a processor mounted on a vehicle to detect lane markings that define a lane in which the vehicle is traveling, calculate a departure index value indicating a possibility that the vehicle will deviate from the lane based on a positional relationship between the lane markings and the vehicle, determine whether a predetermined departure condition is satisfied based on the departure index value, and if the departure condition is satisfied, execute departure prevention control for the vehicle to prevent the vehicle from deviating from the lane, and relax the departure condition and reduce the control amount of the vehicle when the departure prevention control is executed in response to an operation by the driver of the vehicle to prevent the vehicle from deviating from the lane performed before the predetermined departure condition is satisfied. Effect of the Invention

[0013] The vehicle control device according to the present disclosure has an effect of preventing the vehicle from deviating from the vehicle's own lane while traveling, without making the driver of the vehicle feel uneasy. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of a vehicle control system in which a vehicle control device is implemented. [Diagram 2] 1 is a hardware configuration diagram of an electronic control device that is an embodiment of a vehicle control device. [Diagram 3] FIG. 2 is a functional block diagram of a processor of an electronic control unit related to vehicle control processing. [Figure 4] FIG. 13 is a diagram showing the relationship between the departure prevention operation count and a first distance threshold which is one of the departure conditions. [Diagram 5] 4 is an operation flowchart of a vehicle control process according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a vehicle control device, a vehicle control method executed by the vehicle control device, and a computer program for controlling the vehicle will be described with reference to the drawings. The vehicle control device determines whether a predetermined departure condition is satisfied based on a departure index value indicating the possibility that the vehicle will deviate from the lane in which the vehicle is traveling. If the predetermined departure condition is satisfied, the vehicle control device executes departure prevention control for the vehicle to prevent the vehicle from deviating from the lane. Furthermore, in response to an operation by the driver of the vehicle to prevent the vehicle from deviating from the lane performed before the predetermined departure condition is satisfied, the vehicle control device relaxes the departure condition and reduces the control amount of the vehicle when the departure prevention control is executed.

[0016] FIG. 1 is a schematic diagram of a vehicle control system in which a vehicle control device is implemented. FIG. 2 is a hardware configuration diagram of an electronic control device that is one embodiment of the vehicle control device. The vehicle control system 1 is mounted on a vehicle 10 that is an example of a host vehicle, and is capable of controlling the vehicle 10 to be driven automatically. For this purpose, the vehicle control system 1 has a camera 2, a GPS receiver 3, a storage device 4, and an electronic control unit (ECU) 5 that is an example of a vehicle control device. The camera 2, the GPS receiver 3, the storage device 4, and the ECU 5 are communicatively connected via an in-vehicle network that complies with a standard such as a controller area network. The vehicle control system 1 may further have a distance measurement sensor (not shown) such as a LiDAR sensor or a radar. The vehicle control system 1 may further have a wireless communication terminal (not shown) for wireless communication with other devices.

[0017] The camera 2 is an example of a sensor capable of detecting objects around the vehicle 10. The camera 2 has a two-dimensional detector configured with an array of photoelectric conversion elements sensitive to visible light, such as a CCD or a C-MOS, and an imaging optical system that forms an image of the area to be photographed on the two-dimensional detector. The camera 2 is attached, for example, in the passenger compartment of the vehicle 10 so as to face the front of the vehicle 10. The camera 2 photographs the area in front of the vehicle 10 at every predetermined photographing period, and generates an image showing the area in front of the vehicle 10. The image obtained by the camera 2 is an example of a sensor signal, and may be a color image or a gray image. The vehicle 10 may be provided with two or more cameras with different photographing directions or focal lengths.

[0018] Every time the camera 2 generates an image, it outputs the generated image to the ECU 5 via the in-vehicle network.

[0019] The GPS receiver 3 is an example of a positioning device, and receives GPS signals from GPS satellites at predetermined intervals and measures the vehicle's own position based on the received GPS signals. The GPS receiver 3 outputs positioning information representing the measurement result of the vehicle's own position based on the GPS signals to the ECU 5 via the in-vehicle network at predetermined intervals. The vehicle 10 may have a receiver that complies with a satellite positioning system other than the GPS receiver 3. In this case, the receiver measures the vehicle's own position.

[0020] The storage device 4 is an example of a storage unit, and includes, for example, a hard disk device, a non-volatile semiconductor memory, or an optical recording medium and an access device therefor. The storage device 4 stores a high-precision map, which is an example of map information. The high-precision map includes information used for autonomous driving control for each road section within an area represented on the high-precision map. The information used for autonomous driving control includes, for example, information representing road markings such as lane markings or stop lines for each road section, information representing road signs, and information representing features around the road.

[0021] Furthermore, the storage device 4 may have a processor for executing an update process of the high-precision map, a process related to a read request of the high-precision map from the ECU 5, and the like. In this case, the storage device 4 transmits a request to acquire a high-precision map to a map server via a wireless communication terminal (not shown) together with the current position of the vehicle 10, for example, every time the vehicle 10 moves a predetermined distance. Then, the storage device 4 receives map information including a high-precision map for a predetermined area around the current position of the vehicle 10 from the map server via the wireless communication terminal, and stores the high-precision map. Furthermore, when the storage device 4 receives a read request of the high-precision map from the ECU 5, it extracts an area that includes the current position of the vehicle 10 and is relatively narrower than the above-mentioned predetermined area from the stored high-precision map, and outputs the area to the ECU 5 via the in-vehicle network.

[0022] The ECU 5 executes a process for assisting the driver of the vehicle 10. In this embodiment, when the vehicle 10 is about to deviate from the lane in which the vehicle 10 is traveling, the ECU 5 executes deviation prevention control for preventing the deviation.

[0023] 2, the ECU 5 has a communication interface 21, a memory 22, and a processor 23. The communication interface 21, the memory 22, and the processor 23 may each be configured as a separate circuit, or may be integrated into a single integrated circuit.

[0024] The communication interface 21 has an interface circuit for connecting the ECU 5 to an in-vehicle network. Every time the communication interface 21 receives an image from the camera 2, it passes the received image to the processor 23. Every time the communication interface 21 receives positioning information from the GPS receiver 3, it passes the positioning information to the processor 23. Furthermore, the communication interface 21 passes the high-precision map read from the storage device 4 to the processor 23.

[0025] The memory 22 is another example of a storage unit, and includes, for example, a volatile semiconductor memory and a non-volatile semiconductor memory. The memory 22 stores various data used in the vehicle control process executed by the processor 23 of the ECU 5. For example, the memory 22 stores a departure condition for determining whether or not to execute departure prevention control. The memory 22 also stores various information used in calculating the departure index value, such as a parameter set that defines a discriminator for detecting lane markings. The memory 22 also stores parameters of the camera 2, such as the focal length, shooting direction, and installation position (including installation height) of the camera 2. The memory 22 also stores a high-precision map read from the storage device 4. The memory 22 also temporarily stores an image received from the camera 2 and positioning information received from the GPS receiver 3. The memory 22 also temporarily stores various data generated during the vehicle control process. Such data includes a departure prevention operation count that indicates the number of departure prevention operations performed by the driver before the execution of departure control, and an interruption operation count that indicates the number of interruption operations of departure prevention control performed while the departure control is being executed.

[0026] The processor 23 includes one or more central processing units (CPUs) and their peripheral circuits. The processor 23 may further include other arithmetic circuits, such as a logic arithmetic unit, a numerical arithmetic unit, or a graphic processing unit. The processor 23 executes vehicle control processing for the vehicle 10.

[0027] 3 is a functional block diagram of the processor 23 related to the vehicle control process. The processor 23 has a detection unit 31, a calculation unit 32, a control unit 33, and a change unit 34. Each of these units in the processor 23 is, for example, a functional module realized by a computer program running on the processor 23. Alternatively, each of these units in the processor 23 may be a dedicated arithmetic circuit provided in the processor 23.

[0028] The detection unit 31 detects lane markings that divide the lane in which the vehicle 10 is traveling from an image generated by the camera 2. To this end, the detection unit 31 detects surrounding vehicles by inputting the image acquired from the camera 2 to a classifier. As such a classifier, the detection unit 31 may use a deep neural network (DNN) for object detection having a convolutional neural network (CNN) type architecture, such as a Single Shot MultiBox Detector (SSD) or Faster R-CNN. Alternatively, the detection unit 31 may use a DNN having a self attension network (SAN) type architecture as such a classifier. Alternatively, the detection unit 31 may use a DNN for semantic segmentation, such as a Fully Convolutional Network or U-net, as such a classifier. Alternatively, the detection unit 31 may use a classifier based on another machine learning method, such as an AdaBoost classifier, as such a classifier. Such a classifier is trained in advance according to a predetermined learning method such as backpropagation using a large number of teacher images showing lane markings so as to detect lane markings from an image or to distinguish individual pixels showing lane markings from other pixels. The classifier outputs information indicating the area showing the detected lane markings in the input image.

[0029] The detection unit 31 notifies the calculation unit 32 and the control unit 33 of information indicating the area on the image where the lane markings are represented.

[0030] The calculation unit 32 calculates a departure index value indicating the possibility that the vehicle 10 will deviate from the own lane, based on the positional relationship between the lane markings and the vehicle 10. In this embodiment, the calculation unit 32 calculates, as the departure index value, the distance between the left and right lane markings that separate the vehicle 10 from the own lane (hereinafter referred to as the lateral distance).

[0031] Here, the positions on the image correspond one-to-one to the orientations as viewed from the camera 2. Therefore, the calculation unit 32 estimates the positions of the lane markings corresponding to the reference positions on the image, with the camera 2 as a reference, for the left and right lane markings, based on the horizontal reference positions of the pixels representing the left and right lane markings at the positions closest to the bottom edge of the image, and the parameters of the camera 2, such as the focal length, the shooting direction, and the installation height. Furthermore, the calculation unit 32 calculates the distances from the camera 2 to the left and right lane markings, based on the estimation results, the extension direction of the lane markings, and the shooting direction of the camera 2. The calculation unit 32 then calculates the lateral distances for the left and right sides of the vehicle 10 by subtracting the distances from the mounting position of the camera 2 to the side of the vehicle 10 from the distances from the camera 2 to the lane markings.

[0032] The calculation unit 32 notifies the control unit 33 and the change unit 34 of the lateral distances to the left and right of the vehicle 10 that have been calculated as the departure index values.

[0033] The control unit 33 determines whether a predetermined departure condition is satisfied based on the departure index value, and executes departure prevention control when the predetermined departure condition is satisfied. For example, the predetermined departure condition is that either one of the left and right lateral distances, which are the departure index value, becomes equal to or less than a first distance threshold (e.g., 5 cm), and the trajectory of the vehicle 10 predicted from that time point onwards intersects with a lane marking that divides the vehicle's own lane. In the following, the time point when either one of the left and right lateral distances becomes equal to or less than the first distance threshold is called an attention time point. Therefore, every time the control unit 33 receives the left and right lateral distances from the calculation unit 32, the control unit 33 compares the lateral distances with the first distance threshold. Then, the control unit 33 detects the time point when either the left or right lateral distance becomes equal to or less than the first distance threshold as an attention time point. After the attention time point, the control unit 33 predicts the change in the lateral distance for a predetermined future period from that time point onwards based on the change in the lateral distance for a certain period in the past immediately prior to the current time. At this time, the control unit 33 predicts the change in the lateral distance in a predetermined future period by applying a prediction filter such as a Kalman filter to the change in the lateral distance in a certain period in the recent past. Alternatively, the control unit 33 may predict the change in the lateral distance in a predetermined future period by applying a predetermined extrapolation process to the change in the lateral distance in a certain period in the recent past. Then, when the predicted value of the lateral distance becomes zero at any point in time within the predetermined period, the control unit 33 determines that the predicted trajectory of the vehicle 10 intersects with the lane markings that divide the vehicle's lane. In other words, the control unit 33 determines that a predetermined departure condition is satisfied.

[0034] Alternatively, the control unit 33 may obtain the trajectory of the vehicle 10 during a certain period of time based on the positions of the vehicle 10 at each of a plurality of time points within the certain period of time immediately preceding the attention time point. The control unit 33 may then predict the trajectory of the vehicle 10 during a predetermined future period of time based on the trajectory. Furthermore, the control unit 33 may compare the trajectory of the vehicle 10 during a predetermined future period of time with the lane markings that mark the vehicle's own lane, which are shown on the high-precision map, to determine whether the predicted trajectory of the vehicle 10 intersects with the lane markings that mark the vehicle's own lane. This allows the control unit 33 to more accurately determine whether the vehicle 10 is likely to deviate from the vehicle's own lane.

[0035] In this case, the control unit 33 detects the position of the vehicle 10 at the time of generating the image by comparing the image showing the surroundings of the vehicle 10 generated by the camera 2 with the high-precision map. For example, the control unit 33 assumes the position and attitude of the vehicle 10 and projects the features on or around the road detected from the image onto the high-precision map, or projects the features on or around the road around the vehicle 10 shown on the high-precision map onto the image. The features on or around the road can be, for example, road markings such as lane markings or stop lines, or curbs. The classifier used to detect the lane markings may be trained in advance to detect these features as well. Therefore, the control unit 33 can detect these features by inputting the image into the classifier. The control unit 33 estimates the position and attitude of the vehicle 10 when the features detected from the image and the features shown on the high-precision map most closely match as the self-position of the vehicle 10.

[0036] The control unit 33 may determine the position where the feature is projected on the high-precision map or image by using the assumed initial values ​​of the position and attitude of the vehicle 10 and the parameters of the camera 2, such as the focal length, the installation height, and the shooting direction. As the initial values ​​of the position and attitude of the vehicle 10, the position of the vehicle 10 measured by the GPS receiver 3 at the time closest to the time of image generation, or the position where the previously detected position and attitude of the vehicle 10 are corrected using odometry information, is used. Then, the control unit 33 calculates the degree of match between the feature on or around the road detected from the image and the corresponding feature shown on the high-precision map (for example, the inverse of the sum of the squares of the distance between the corresponding features).

[0037] The control unit 33 repeats the above process while changing the assumed position and attitude of the vehicle 10. Then, the control unit 33 estimates the assumed position and attitude when the degree of agreement is maximized as the actual self-position of the vehicle 10.

[0038] The control unit 33 may detect the position of the vehicle 10 as described above for each of the multiple images generated within a certain period in the recent past, thereby determining the trajectory of the vehicle 10 during that certain period. Furthermore, the control unit 33 may predict the trajectory of the vehicle 10 during a certain period in the future by applying a prediction filter such as a Kalman filter to the trajectory of the vehicle 10 during the certain period in the recent past, or by applying a predetermined extrapolation process.

[0039] When the ECU 5 is controlling the automatic driving of the vehicle 10, the ECU 5 may request the driver to take over driving of the vehicle 10 via a notification device (not shown) provided in the vehicle cabin at a caution time.

[0040] Furthermore, after the attention point, when the left and right lateral distances become greater than the first distance threshold plus a predetermined offset distance, the control unit 33 may determine that the departure condition is not satisfied.

[0041] According to another modification, the control unit 33 may determine that a predetermined departure condition is satisfied when a period during which either the left or right lateral distance is equal to or less than the first distance threshold continues for a predetermined time or longer.

[0042] When the departure condition is satisfied, the control unit 33 executes departure prevention control. As the departure prevention control, the control unit 33 corrects the current steering angle of the steering wheel by a predetermined steering amount in a direction in which the vehicle 10 moves toward the center of the own lane. The control unit 33 then controls the steering wheel according to the corrected steering angle, thereby preventing the vehicle 10 from departing from the own lane. This predetermined steering amount is one example of a control amount for the vehicle 10. Note that, in the departure prevention control, the control unit 33 may also perform control to decelerate the vehicle 10 in addition to correcting the steering angle. In this case, the control unit 33 sets a braking amount that decelerates the vehicle 10 at a predetermined deceleration, and controls the brakes according to the set braking amount. The braking amount is another example of a control amount for the vehicle 10.

[0043] As will be described in detail later, the predetermined steering amount is adjusted based on the steering operation by the driver when the departure prevention control is executed or immediately before the execution of the departure prevention control, thereby suppressing anxiety caused to the driver when the departure prevention control is executed.

[0044] After starting deviation prevention control, when the left and right lateral distances become greater than the first distance threshold plus a predetermined offset distance, the controller 33 ends deviation prevention control.

[0045] The change unit 34 relaxes the departure condition in response to an operation by the driver to prevent the vehicle 10 from departing from the own lane (hereinafter, may be referred to as a departure prevention operation) performed before the departure condition is satisfied. Furthermore, the change unit 34 reduces the control amount of the vehicle 10 when the departure prevention control is executed.

[0046] For example, when the lateral distance on either the left or right side is equal to or less than the second distance threshold and the vehicle 10 operates the steering wheel in a direction returning to the center of the own lane before the departure condition is satisfied, the change unit 34 determines that the driver has performed a departure prevention operation. Then, the change unit 34 increments the departure prevention operation count stored in the memory 22 by 1. The second distance threshold is set to a value greater than the first distance threshold, for example, 10 cm. In addition, the change unit 34 may determine that the vehicle 10 has been steered in a direction returning to the center of the own lane when the left lateral distance becomes equal to or less than the second distance threshold and the steering wheel is operated in a direction in which the left lateral distance increases, that is, toward the right. In this case, the change unit 34 may determine whether the steering wheel has been operated in a direction in which the vehicle 10 has returned to the center of the own lane, based on the steering angle received from the steering control device or the change in the left lateral distance. Similarly, when the lateral distance on the right side becomes equal to or less than the second distance threshold, the change unit 34 determines that the steering has been operated in a direction that increases the lateral distance on the right side, i.e., toward the left, and that the steering has been operated in a direction that returns the vehicle 10 to the center of the own lane.

[0047] The change unit 34 refers to the departure prevention operation count stored in the memory 22 and determines whether or not to change the departure condition and the control amount.

[0048] For example, when the departure prevention operation count exceeds a predetermined number, the change unit 34 changes the departure condition to ease the departure condition and reduces the control amount of the departure prevention control. In this case, for example, the change unit 34 increases the first distance threshold by a predetermined distance. Also, the change unit 34 reduces the predetermined steering amount, which is the control amount of the departure prevention control, by a predetermined angle. This makes it easier to satisfy the departure condition, so that the execution of the departure prevention control is started at an earlier timing. Also, by starting the departure prevention control earlier, the grace period until the vehicle 10 deviates from the own lane is longer, so that the vehicle 10 is prevented from deviating from the own lane even with a smaller control amount.

[0049] Furthermore, the modification unit 34 may tighten the specified departure conditions and increase the amount of control of the vehicle when departure prevention control is being executed in response to the driver's operation to interrupt departure prevention control (hereinafter sometimes referred to as the interruption operation) while departure prevention control is being executed.

[0050] For example, when the driver rotates the steering wheel in a direction opposite to the direction of correction of the steering angle of the steering wheel while deviation prevention control is being executed, the change unit 34 determines that the driver has performed an interruption operation. In this case, the change unit 34 may also determine whether or not an interruption operation has been performed based on the steering angle received from the steering control device. When the change unit 34 detects an interruption operation by the driver, the change unit 34 increments the interruption operation count stored in the memory 22 by one.

[0051] The change unit 34 refers to the interruption operation count stored in the memory 22 and determines whether or not to change the deviation condition and the control amount.

[0052] For example, when the interruption operation count exceeds a predetermined number, the change unit 34 changes the departure conditions to make them stricter and increases the control amount of the departure prevention control. In this case, for example, the change unit 34 decreases the first distance threshold by a predetermined distance. Also, the change unit 34 increases the predetermined steering amount, which is the control amount of the departure prevention control, by a predetermined angle. This makes it more difficult to satisfy the departure conditions, and delays the timing at which execution of the departure prevention control is started. Also, since the control amount increases in accordance with the later start of the departure prevention control, the vehicle 10 is prevented from deviating from its own lane even if the departure conditions are changed to be stricter.

[0053] After the departure prevention operation count exceeds a predetermined number of times, each time the value of the departure prevention operation count increases by a predetermined number of additional changes (for example, one to several times), the change unit 34 may further relax the departure condition and further reduce the control amount of the departure prevention control. That is, each time the value of the departure prevention operation count increases by a predetermined number of additional changes, the change unit 34 increases the first distance threshold by a predetermined distance and reduces the steering amount by a predetermined angle. However, it is preferable that the change unit 34 does not change the first distance threshold so that it exceeds a preset upper limit value. This prevents the departure prevention control from being excessively executed. Furthermore, it is preferable that the change unit 34 does not reduce the steering amount of the departure prevention control below a predetermined lower limit value. This prevents the departure prevention control from being substantially not executed.

[0054] Similarly, after the interruption operation count exceeds a predetermined number of times, the change unit 34 may further tighten the departure condition and further increase the control amount of the departure prevention control each time the value of the interruption operation count increases by a predetermined number of additional changes. That is, each time the value of the interruption operation count increases by a predetermined number of additional changes, the change unit 34 decreases the first distance threshold by a predetermined distance and increases the steering amount by a predetermined angle. However, it is preferable that the change unit 34 does not change the first distance threshold below a preset lower limit value. This prevents the departure prevention control from being unable to be executed. Furthermore, it is preferable that the change unit 34 does not increase the steering amount of the departure prevention control above a predetermined upper limit value. This prevents the vehicle 10 from suddenly changing its direction when the departure prevention control is executed.

[0055] Fig. 4 is a diagram showing the relationship between the deviation prevention operation count and the first distance threshold, which is one of the deviation conditions. In Fig. 4, the horizontal axis represents the deviation prevention operation count value, and the vertical axis represents the first distance threshold. Graph 400 shows the relationship between the deviation prevention operation count value and the first distance threshold.

[0056] As shown in graph 400, the first distance threshold is kept constant until the value of the departure prevention operation count exceeds a predetermined number N. Thereafter, each time the value of the departure prevention operation count increases, the first distance threshold becomes larger. Accordingly, the control amount (e.g., steering amount) of the departure prevention control gradually decreases. Then, when the first distance threshold reaches its upper limit value ThU, the first distance threshold is kept constant thereafter, even if the value of the departure prevention operation count increases.

[0057] 5 is an operational flowchart of the vehicle control process. The processor 23 executes the vehicle control process in accordance with the following operational flowchart.

[0058] The detection unit 31 of the processor 23 detects lane markings that define the vehicle's own lane from the image generated by the camera 2 (step S101). The calculation unit 32 of the processor 23 then calculates a departure index value based on the positional relationship between the detected lane markings and the vehicle 10 (step S102). Furthermore, the control unit 33 of the processor 23 determines whether or not a departure condition is satisfied based on the departure index value (step S103).

[0059] If the departure condition is satisfied (step S103-Yes), the control unit 33 executes departure prevention control (step S104). Then, the change unit 34 of the processor 23 determines whether or not the driver has performed an interruption operation to interrupt the departure prevention control while the departure prevention control is being executed (step S105). If the driver has not performed the interruption operation (step S105-No), the processor 23 ends the vehicle control process. On the other hand, if the driver has performed the interruption operation (step S105-Yes), the change unit 34 changes the departure condition to be stricter, and increases the control amount of the vehicle 10 when the departure prevention control is executed (step S106). Then, the processor 23 ends the vehicle control process.

[0060] Furthermore, in step S103, if the departure condition is not satisfied (step S103-No), the change unit 34 determines whether or not the driver performed a departure prevention operation to prevent the vehicle 10 from departing from the own lane before the departure condition is satisfied (step S107). If the driver has not performed a departure prevention operation (step S107-No), the processor 23 ends the vehicle control process. On the other hand, if the driver has performed a departure prevention operation (step S107-Yes), the change unit 34 makes changes to ease the departure condition and reduces the control amount of the vehicle 10 when the departure prevention control is executed (step S108). Then, the processor 23 ends the vehicle control process.

[0061] As described above, the vehicle control device executes deviation prevention control to prevent the vehicle from deviating from the own lane when a predetermined deviation condition is satisfied. Then, the vehicle control device eases the deviation condition in response to a deviation prevention operation of the vehicle by the driver performed before the deviation condition is satisfied, and reduces the control amount of the vehicle during execution of the deviation prevention control. In this way, the vehicle control device adjusts the deviation condition in response to the driver's operation, so that the timing of starting the deviation prevention control can be matched to the driver's sense. Furthermore, when the deviation condition is eased and the deviation prevention control becomes easier to execute, the vehicle control device reduces the control amount in the deviation prevention control, so that the vehicle can be prevented from performing abrupt operations during the deviation prevention control. As a result, the vehicle control device can prevent the driver from feeling uneasy. Furthermore, the vehicle control device tightens the deviation condition in response to an interruption operation by the driver during execution of the deviation prevention control, and increases the control amount of the vehicle during execution of the deviation prevention control. In this way, when departure conditions become stricter and departure prevention control becomes more difficult to implement, the control amount in departure prevention control is increased, so that this vehicle control device can reliably prevent the vehicle from departing from its own lane even if departure prevention control is started late.

[0062] According to a modified example, the change unit 34 may change the increment of the departure prevention operation count or the interruption operation count according to the situation around the vehicle 10. For example, the smaller the radius of curvature of the road on which the vehicle 10 is traveling when the driver performs the departure prevention operation, the smaller the increment of the departure prevention operation count. Similarly, the smaller the radius of curvature of the road on which the vehicle 10 is traveling when the driver performs the interruption operation, the smaller the increment of the interruption operation count. In this case, the change unit 34 may specify the radius of curvature of the road on which the vehicle 10 is traveling by referring to the latest detection result of the position of the vehicle 10 and the high-precision map.

[0063] In addition, the deviation index value may be inaccurate under conditions where it is difficult to detect lane markings, such as when it is raining, snowing, or foggy. Therefore, when the surrounding conditions of the vehicle 10 when the driver performs a deviation prevention operation or an interruption operation are conditions where it is difficult to detect lane markings, the change unit 34 may set the increase in the deviation prevention operation count or the interruption operation count to a value smaller than normal (for example, 0 to 0.5). Note that, when the rainfall measured by a rainfall sensor mounted on the vehicle 10 is equal to or greater than a predetermined rainfall threshold, the change unit 34 determines that the surrounding conditions of the vehicle 10 are conditions where it is difficult to detect lane markings. Alternatively, the change unit 34 may determine that the surrounding conditions of the vehicle 10 are conditions where it is difficult to detect lane markings when the ECU 5 receives a signal from the wipers of the vehicle 10 indicating that the wipers are operating, or when the fog lamps are on.

[0064] This modification reduces the influence of the driver performing an operation different from his / her original preference due to the circumstances around the vehicle 10. Therefore, the change unit 34 can suppress the timing for starting execution of deviation prevention control from being changed so as to deviate from the timing preferred by the driver.

[0065] A computer program for realizing the functions of the processor 23 of the ECU 5 according to any of the above embodiments or any of the variations thereof may be provided in a form recorded on a computer-readable portable recording medium, such as a semiconductor memory, a magnetic recording medium or an optical recording medium.

[0066] As described above, those skilled in the art can make various modifications to the embodiments within the scope of the present invention. [Explanation of symbols]

[0067] 1 Vehicle Control System 10 Vehicles 2 Camera 3 GPS receiver 4. Storage Devices 5 Electronic Control Unit (ECU) 21 Communication Interface 22 Memory 23 Processors 31 Detection unit 32 Calculation section 33 Control Unit 34 Changes

Claims

1. A detection unit that detects lane markings that define a lane in which a vehicle is traveling; a calculation unit that calculates a departure index value indicating a possibility that the vehicle will deviate from the host lane based on a positional relationship between the lane marking and the vehicle; a control unit that determines whether a predetermined departure condition is satisfied based on the departure index value, and, when the predetermined departure condition is satisfied, executes departure prevention control on the vehicle to prevent the vehicle from departing from the own lane; a change unit that relaxes the predetermined departure condition and reduces a control amount of the vehicle when the departure prevention control is executed, in response to an operation by a driver of the vehicle to prevent the vehicle from departing from the own lane, performed before the predetermined departure condition is satisfied; A vehicle control device having the above configuration.

2. 2. The vehicle control device according to claim 1, wherein the change unit tightens the predetermined departure condition in response to an operation by the driver to interrupt the departure prevention control while the departure prevention control is being executed, and increases the control amount of the vehicle when the departure prevention control is being executed.

3. 2. The vehicle control device according to claim 1, wherein the change unit increases a departure prevention operation count, which indicates the number of times an operation has been performed, by a predetermined increment each time an operation is performed to prevent the vehicle from departing from the own lane, and when the value of the departure prevention operation count exceeds a predetermined number, relaxes the predetermined departure condition and reduces the control amount of the vehicle when the departure prevention control is executed.

4. The vehicle control device according to claim 3 , wherein the change unit changes the predetermined increase amount depending on a situation around the vehicle when an operation is performed to prevent the vehicle from departing from the own lane.

5. Detecting lane markings that define the lane in which the vehicle is traveling; calculating a deviation index value representing a possibility that the vehicle will deviate from the own lane based on a positional relationship between the lane marking and the vehicle; determining whether a predetermined departure condition is satisfied based on the departure index value; When the predetermined departure condition is satisfied, a departure prevention control is executed on the vehicle to prevent the vehicle from departing from the own lane; relaxing the predetermined departure condition and reducing a control amount of the vehicle when the departure prevention control is executed in response to an operation by a driver of the vehicle to prevent the vehicle from departing from the own lane, the operation being performed before the predetermined departure condition is satisfied; A vehicle control method comprising:

6. Detecting lane markings that define the lane in which the vehicle is traveling; calculating a deviation index value representing a possibility that the vehicle will deviate from the own lane based on a positional relationship between the lane marking and the vehicle; determining whether a predetermined departure condition is satisfied based on the departure index value; When the predetermined departure condition is satisfied, a departure prevention control is executed on the vehicle to prevent the vehicle from departing from the own lane; relaxing the predetermined departure condition and reducing a control amount of the vehicle when the departure prevention control is executed in response to an operation by a driver of the vehicle to prevent the vehicle from departing from the own lane, the operation being performed before the predetermined departure condition is satisfied; A vehicle control computer program for causing a processor mounted on the vehicle to execute the above-mentioned steps.

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