Lane deviation prevention method and lane deviation prevention device

Abstract

A lane deviation prevention method according to the present invention is such that: it is estimated whether there is a high probability of a lane deviation operation, which is an operation where a driver intentionally causes a host vehicle to deviate from the lane in which the vehicle is traveling, being performed (S3); in accordance with whether there is a high probability of the lane deviation operation being performed, one or more steering parameters representing a state of a steering operation by the driver are selected (S5, S6); when at least one from among determination conditions based on each of the selected steering parameters is met, an override operation by the driver is detected (S7); and when the override operation is detected, control of the steering angle as based on a steering command value that suppresses deviation of the host vehicle is stopped (S8). The number or types of steering parameters selected when it is estimated that there is a high probability of the lane deviation operation being performed is greater than the number or types of steering parameters selected when it is estimated that there is a low probability of the lane deviation operation being performed.

Description

Lane departure prevention method and lane departure prevention apparatus

[0001] The present invention relates to a lane departure prevention method and a lane departure prevention apparatus.

[0002] The travel control system described in the following Patent Document 1 determines whether an override condition is satisfied by the logical OR of conditions using two parameters representing the state of a steering system.

[0003] Japanese Patent No. 6535482

[0004] Detecting an override operation by the logical OR of conditions using a plurality of parameters as in Patent Document 1 mentioned above has the advantage of enabling early detection of the override operation, but on the other hand, it is prone to erroneous detection. An object of the present invention is to adjust the trade-off between early detection of an override operation and erroneous determination in detecting an override operation based on a steering parameter representing a steering operation state by a driver.

[0005] In the lane departure prevention method according to one aspect of the present invention, a steering command value for suppressing departure of the host vehicle from the travel lane of the host vehicle is calculated, a steering angle of the host vehicle is controlled based on the steering command value, and it is estimated whether or not there is a high possibility that a lane departure operation, which is an operation by a driver to intentionally cause the host vehicle to depart from the travel lane, will be performed. One or more steering parameters representing a steering operation state by the driver are selected according to whether there is a high possibility that the lane departure operation will be performed. When at least one of each determination condition respectively based on the selected steering parameters is satisfied, an override operation by the driver is detected. When an override operation is detected, control of the steering angle based on the steering command value is stopped to enable the steering angle operation by the driver. The number or type of steering parameters selected when it is estimated that there is a high possibility that a lane departure operation will be performed is greater than the number or type of steering parameters selected when it is estimated that there is a low possibility that a lane departure operation will be performed.

[0006] In another embodiment of the present invention, a lane departure prevention method detects an override operation by the driver when all of the determination conditions based on the selected steering parameters are met. The number or types of steering parameters selected when it is estimated that there is a high probability of a lane departure operation is less than the number or types of steering parameters selected when it is estimated that there is a low probability of a lane departure operation.

[0007] According to the present invention, in detecting override operations based on steering parameters representing the state of steering operations by the driver, the trade-off between early detection and misjudgment of override operations can be adjusted. The objectives and advantages of the present invention are embodied and achieved using the elements and combinations thereof set forth in the claims. Both the above general description and the following detailed description should be understood as merely illustrative and explanatory, and not as limiting the invention in the sense of the claims.

[0008] This is a schematic diagram of an example of a lane departure prevention device according to the embodiment. This is a block diagram of an example of the controller's functional configuration. (a) to (e) are timing charts illustrating an example of operation when there is a high probability of lane departure. (a) to (e) are timing charts illustrating an example of operation when there is a low probability of lane departure. This is a flowchart of an example of a lane departure prevention method according to the embodiment.

[0009] (First Embodiment) (Configuration) Figure 1 is a schematic configuration diagram of an example of a lane departure prevention device according to the embodiment. The vehicle 1 is equipped with a lane departure prevention device 10 that prevents the vehicle 1 from deviating from the lane in which the vehicle 1 is traveling (hereinafter sometimes referred to as the "driving lane"). In the following description, the control of the lane departure prevention device 10 that prevents the vehicle 1 from deviating from the driving lane may be referred to as "lane departure prevention control".

[0010] The lane departure prevention device 10 includes a vehicle speed sensor 11, a steering angle sensor 12, a camera 13, an object detection sensor 14, a steering torque sensor 15, a controller 16, and a steering angle control actuator 17. The vehicle speed sensor 11 detects the vehicle speed V of the vehicle 1. The steering angle sensor 12 detects the steering angle θs of the steering wheel.

[0011] Camera 13 captures an image of the area around the vehicle 1, including the area in front of the vehicle 1, generates an image, and outputs the generated image to the controller 16. Object detection sensor 14 is a sensor that detects objects around the vehicle 1. For example, object detection sensor 14 may be a laser radar, millimeter-wave radar, LIDAR (Light Detection and Ranging, Laser Imaging Detection and Ranging), or ultrasonic sensor. Object detection sensor 14 may be equipped with multiple different types of these sensors.

[0012] The steering torque sensor 15 detects the steering torque Ts, which is the torque input to the steering shaft by the driver. The vehicle speed sensor 11, the steering angle sensor 12, the object detection sensor 14, and the steering torque sensor 15 output the detection result information to the controller 16.

[0013] The controller 16 is an electronic control unit (ECU) that performs lane departure prevention control for the vehicle 1. For example, the controller 16 performs lane departure prevention control by driving the steering angle control actuator 17 based on the detection signals from the vehicle speed sensor 11, the steering angle sensor 12, the object detection sensor 14, and the steering torque sensor 15, and the captured image generated by the camera 13.

[0014] The controller 16 includes a processor 16a and peripheral components such as a storage device 16b. The processor 16a may be, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The storage device 16b may include a semiconductor storage device, a magnetic storage device, an optical storage device, etc. The functions of the controller 16 described below are realized, for example, by the processor 16a executing a computer program stored in the storage device 16b.

[0015] The controller 16 may be formed by dedicated hardware for performing the information processing described below. For example, the controller 16 may include functional logic circuits set in a general-purpose semiconductor integrated circuit. For example, the controller 16 may have a programmable logic device (PLD) such as a field-programmable gate array (FPGA). The steering angle control actuator 17 controls the steering direction and steering amount of the steering mechanism of the vehicle 1 in accordance with the control signal from the controller 16.

[0016] Next, lane departure prevention control by the controller 16 will be described. Based on the vehicle speed V detected by the vehicle speed sensor 11, the steering angle θs of the steering wheel detected by the steering angle sensor 12, and the lane markings included in the image of the area in front of the vehicle 1 captured by the camera 13, the controller 16 calculates a steering command value to suppress the vehicle 1 from deviating from its driving lane. The controller 16 controls the steering angle of the vehicle 1 based on the steering command value. In the following description, the steering command value calculated by the lane departure prevention control to suppress the vehicle 1 from deviating from its driving lane may be referred to as the "steering command value by lane departure prevention control".

[0017] Furthermore, the controller 16 detects steering parameters that represent the state of steering operations performed by the driver. For example, the controller 16 may detect the following steering parameters: the steering angle θs performed by the driver, the deviation of the steering angle θs from the steering angle command value θc calculated as a steering command value, the steering angular velocity which is the first time derivative of the steering angle θs, the steering angular acceleration which is the second time derivative of the steering angle θs, the steering torque Ts, and the steering torque velocity which is the first time derivative of the steering torque Ts.

[0018] The controller 16 determines whether predetermined conditions regarding steering parameters are met. If the predetermined conditions are met, the controller 16 detects an override operation by the driver. When an override operation is detected, the controller 16 stops controlling the steering angle based on the steering command value by the lane departure prevention control and allows the driver to control the steering angle. If no override operation is detected, the controller 16 continues to control the steering angle based on the steering command value by the lane departure prevention control.

[0019] Thus, when detecting override operations based on judgment conditions related to steering parameters, override operations can be detected early by detecting the override operation when at least one of the multiple judgment conditions based on each of the multiple steering parameters is met (i.e., when the result of the logical OR operation of these multiple judgment conditions is "true"). However, on the other hand, there is a problem that false detections are more likely to occur.

[0020] Therefore, the controller 16 of the embodiment estimates whether the current situation in which the vehicle 1 is located is likely to be such that the driver is likely to intentionally deviate the vehicle 1 from its lane. In the following description, the operation in which the driver intentionally deviates the vehicle 1 from its lane may be referred to as a "lane departure operation." For example, the controller 16 may estimate that situations in which the vehicle 1 changes lanes from a merging lane to a main lane, situations in which there is an obstacle in the direction of travel of the vehicle 1, and situations in which an oncoming vehicle is approaching the vehicle 1 are likely to be situations in which a lane departure operation is likely to occur. The main lane and the merging lane are examples of the "first lane" and "second lane" described in the claims, respectively.

[0021] The controller 16 selects a greater number or variety of steering parameters when it estimates that a lane departure operation is more likely to occur than when it estimates that a lane departure operation is less likely to occur. The controller 16 detects an override operation when at least one of the determination conditions based on each of the selected steering parameters is met.

[0022] In this way, by making it easier to detect override operations only in scenarios where there is a high probability that the driver will intentionally deviate from the lane, it is possible to suppress the false detection of override operations even when the lane departure operation is not intentional, while detecting override operations earlier and promptly discontinuing lane departure prevention control without interfering with the driver's actions. This allows for a suitable adjustment of the trade-off between early detection of override operations and false judgments.

[0023] Next, the functional configuration of the controller 16 will be explained with reference to Figure 2. The controller 16 comprises a steering command value calculation unit 20, a steering control unit 21, a deviation operation determination unit 22, a determination method determination unit 23, and an override determination unit 24. The steering command value calculation unit 20 calculates a steering command value to suppress the deviation of the vehicle 1 from its driving lane, based on the vehicle speed V detected by the vehicle speed sensor 11, the steering angle θs of the steering wheel detected by the steering angle sensor 12, and the lane marking lines included in the image of the area in front of the vehicle 1 captured by the camera 13.

[0024] For example, the steering command value calculation unit 20 may calculate a steering angle command value θc that specifies a target steering angle as the steering command value. For example, the steering command value calculation unit 20 may calculate the steering angle command value θc by the following calculation method. First, the steering command value calculation unit 20 calculates the yaw angle, which is the angle between the direction of travel of the vehicle 1 and the lane marking line that intersects with the direction of travel of the vehicle 1 first among the left and right lane marking lines (hereinafter referred to as the "target marking line"). The steering command value calculation unit 20 calculates the forward gaze distance L by multiplying a predetermined head time T by the vehicle speed V. Based on the steering angle θs and yaw angle detected by the steering angle sensor 12, the steering command value calculation unit 20 calculates the amount of lateral movement during travel of the forward gaze distance L, and adds this to the current lateral position (distance to the target marking line) to calculate the lateral position at the forward gaze point.

[0025] The steering command value calculation unit 20 calculates the difference obtained by subtracting a predetermined control threshold from the absolute value of the lateral position at the forward gaze point as the lateral position deviation ΔY. The steering command value calculation unit 20 determines that there is a high possibility of deviating from the target boundary line when the lateral position deviation ΔY is 0 or greater, and that there is a low possibility of lane departure when the lateral position deviation ΔY is less than 0.

[0026] The steering command value calculation unit 20 calculates the target yaw moment M based on the following equation (1), where I is the yaw moment of inertia. M = (2 × I × ΔY) / (L × T ２ ) …(1) The steering command value calculation unit 20 calculates the target yaw acceleration by multiplying the target yaw moment M by the yaw inertia moment coefficient, and calculates the target yaw rate γt by multiplying the target yaw acceleration by the vehicle head time T. The steering command value calculation unit 20 calculates the steering angle command value θc based on the following equation (2): θc = γt × (wheelbase) × (1 + (V / V Ｃｈ ) ２ ) × 180 / (V × M ＰＩ ) ... (2) Here, V Ｃｈ This is the vehicle's characteristic speed, M ＰＩ This is a predetermined coefficient. Note that the characteristic speed of the vehicle V Ｃｈ These are parameters of the known Ackermann equations and represent the self-steering characteristics of a vehicle.

[0027] Alternatively, the steering command value calculation unit 20 may calculate steering torque as the steering command value. For example, the steering command value calculation unit 20 may calculate steering torque as the steering command value, where the force to steer to the left increases as the vehicle 1 approaches the right lane marking, and may calculate steering torque as the steering command value, where the force to steer to the right increases as the vehicle 1 approaches the left lane marking.

[0028] The steering control unit 21 controls the steering angle of the vehicle 1 based on the steering command value. The lane departure operation determination unit 22 estimates, based on the detection signal from the object detection sensor 14 and the captured image generated by the camera 13, whether the current situation in which the vehicle 1 is located is likely to be such that a lane departure operation, which is a steering operation in which the driver intentionally deviates the vehicle 1 from the driving lane, is to be performed.

[0029] For example, the lane departure determination unit 22 may estimate that situations in which the vehicle 1 changes lanes from a merging lane to a main lane, situations in which there is an obstacle in the direction of travel of the vehicle 1, and situations in which an oncoming vehicle approaches the vehicle 1 are situations in which there is a high probability of lane departure, and may estimate that situations other than these are situations in which there is a low probability of lane departure.

[0030] The lane departure determination unit 22 sets the value of the intentional departure possibility flag Fp to "True" if it estimates that the current situation in which the vehicle 1 is located is one in which there is a high probability of lane departure, and sets the value of the intentional departure possibility flag Fp to "False" if it estimates that the current situation in which the vehicle 1 is located is one in which there is a low probability of lane departure.

[0031] The determination method determination unit 23 determines a determination method for the override determination unit 24 to determine whether an override operation has occurred, according to the intentional deviation possibility flag Fp. Specifically, if it is estimated that the situation is unlikely to result in a lane departure operation (intentional deviation possibility flag Fp = False), the determination method determination unit 23 selects a first determination method as the determination method for the override determination unit 24. If it is estimated that the situation is likely to result in a lane departure operation (intentional deviation possibility flag Fp = True), the determination method determination unit 23 selects a second determination method as the determination method for the override determination unit 24. When the first determination method is selected, the determination method determination unit 23 sets the value of the determination method flag Fd to "False", and when the second determination method is selected, it sets the value of the determination method flag Fd to "True".

[0032] The override determination unit 24 selects one or more steering parameters according to the determination method flag Fd, and detects an override operation by the driver when at least one of the determination conditions based on the selected steering parameters is met. For example, a determination condition based on the steering angle θs may be a condition that is met when the steering angle θs used to steer in the direction approaching the target lane marking line (the lane marking line that intersects the direction of travel of the vehicle 1 first among the left and right lane marking lines) (hereinafter sometimes referred to as "deviation direction") is equal to or greater than a determination threshold set for the steering angle θs (hereinafter referred to as "steering angle threshold θt").

[0033] For example, a determination condition based on steering torque Ts may be a condition that is met when the steering torque Ts applied to the steering shaft in the direction of steering in the direction of deviation is equal to or greater than a determination threshold set for the steering torque Ts (hereinafter referred to as "steering torque threshold Tt").

[0034] Furthermore, for example, a determination condition based on steering angle θs and steering angle command value θc may be a condition that is met when the deviation of the steering angle θs from the steering angle command value θc is greater than or equal to a determination threshold. Also, each of the determination conditions based on steering angular velocity, steering angular acceleration, and steering torque velocity may be a condition that is met when the steering angular velocity, steering angular acceleration, and steering torque velocity for steering in the direction of deviation are greater than or equal to a determination threshold set for each steering parameter.

[0035] When detecting an override operation, the override determination unit 24 selects a greater number or variety of steering parameters when the second determination method is selected (determination method flag Fd = True) than when the first determination method is selected (determination method flag Fd = False). For example, when the first determination method is selected in a situation where the likelihood of lane departure operation is low, the override determination unit 24 may select only the steering torque Ts as the steering parameter used to determine the detection of an override operation. In this case, the override determination unit 24 detects an override operation when the steering torque Ts applied to the steering shaft in the direction of steering in the direction of departure is greater than or equal to the steering torque threshold Tt. That is, in a situation where the likelihood of lane departure operation is low, only a single steering parameter may be selected.

[0036] On the other hand, if the second determination method is selected in a situation where there is a high probability of lane departure, for example, the override determination unit 24 may select both the steering angle θs and the steering torque Ts as steering parameters to determine whether an override operation has occurred. In this case, the override determination unit 24 detects an override operation if the steering angle θs that steers in the direction of departure is greater than or equal to the steering angle threshold θt, or if the steering torque Ts applied to the steering shaft in the direction of departure is greater than or equal to the steering torque threshold Tt.

[0037] Furthermore, the override determination unit 24 may set the determination threshold set for each steering parameter to a lower value when the second determination method is selected compared to when the first determination method is selected.

[0038] Note that, for example, when the second determination method is selected in a situation where there is a high possibility that a lane departure operation will be performed, the override determination unit 24 may determine detection of an override operation if at least a determination condition based on the steering angle θs is satisfied. Further, for example, when the first determination method is selected in a situation where there is a low possibility that a lane departure operation will be performed, the override determination unit 24 may determine detection of an override operation when both the determination condition based on the steering angle θs and the determination condition related to the steering torque Ts are satisfied.

[0039] When the override determination unit 24 detects an override operation, the steering control unit 21 stops the control of the steering angle based on the steering command value obtained by the lane departure prevention control, and enables the operation of the steering angle by the driver's override operation. On the other hand, when the override determination unit 24 does not detect an override operation, the steering control unit 21 continues the control of the steering angle based on the steering command value obtained by the lane departure prevention control.

[0040] Figures 3(a) to 3(e) and Figures 4(a) to 4(e) are timing charts for explaining an example of changes in the intentional departure possibility flag Fp, the determination method flag Fd, the steering angle θs, the steering torque Ts, and the override determination result in the lane departure prevention control according to the embodiment. Figures 3(a) to 3(e) and Figures 4(a) to 4(e) are timing charts for the case where there is a high possibility that a lane departure operation will be performed and the case where there is a low possibility, respectively. Here, an example is shown in which both the steering angle θs and the steering torque Ts are selected when there is a high possibility that a lane departure operation will be performed, and only the steering torque Ts is selected when there is a high possibility that a lane departure operation will be performed.

[0041] Reference is made to Figures 3(a) to 3(e). When the departure operation determination unit 22 estimates that there is a high possibility that a lane departure operation will be performed at time point t1, the intentional departure possibility flag Fp and the determination method flag Fd are switched from False to True (Figures 3(a), 3(b)), and the determination method by the override determination unit 24 is switched from the first determination method to the second determination method.

[0042] At time point t2, a steering angle θs for steering in the direction of departure exceeds the steering angle threshold θt (FIG. 3(c)), and at time point t3, the steering torque Ts applied to the steering shaft in the direction of steering toward the departure exceeds the steering torque threshold Tt (FIG. 3(d)). When there is a high possibility that a lane departure operation will be performed, the override operation is detected if either one of the determination condition based on the steering angle θs and the determination condition based on the steering torque Ts is satisfied, so the override determination unit 24 detects the override operation at time point t2 (FIG. 3(e)).

[0043] Thereafter, at time point t4, the steering torque Ts becomes less than the steering torque threshold Tt (FIG. 3(d)), so the determination condition based on the steering torque Ts is not satisfied. At time point t5, the steering angle θs becomes less than the steering angle threshold θt (FIG. 3(c)), so the determination condition based on the steering angle θs is not satisfied. The override determination unit 24 stops detecting the override operation at time point t6, which is a time point after a predetermined dead time DT has elapsed from time point t5 when all the determination conditions based on the selected steering parameters (the steering angle θs and the steering torque Ts in this example) have changed to a state where none of the conditions are satisfied (FIG. 3(e)).

[0044] Note that the override determination unit 24 may stop detecting the override operation at time point t5 when all the determination conditions based on the selected steering parameters have changed to a state where none of the conditions are satisfied. When the departure operation determination unit 22 estimates that the possibility of a lane departure operation being performed is low at the subsequent time point t7, the intentional departure possibility flag Fp and the determination method flag Fd are switched from True to False (FIG. 3(a), FIG. 3(b)).

[0045] Refer to Figures 4(a) to 4(e). If the lane departure operation determination unit 22 does not estimate that there is a high probability of lane departure operation, the determination method flag Fd is maintained at False (Figures 3(a) and 3(b)), and the determination method by the override determination unit 24 is maintained at the first determination method. For this reason, the override determination unit 24 does not detect an override operation even if the steering angle θs exceeds the steering angle threshold θt at time t2, and detects an override operation at time t3 when the steering torque Ts exceeds the steering torque threshold Tt. In this way, when there is a high probability of lane departure operation (Figure 3(e)), an override operation can be detected early.

[0046] Subsequently, at time t8, which is the time after a predetermined dead time DT has elapsed from time t4, when all the judgment conditions based on the selected steering parameter (steering torque Ts only) have become unsatisfied, the detection of override operations is stopped (Figure 4(e)). The override determination unit 24 may also stop detecting override operations at time t4, when the state changes to one where all the judgment conditions based on the selected steering parameter (steering torque Ts only) are no longer satisfied.

[0047] (Operation) Figure 5 is a flowchart of an example of a lane departure prevention method according to the embodiment. In step S1, the steering command value calculation unit 20 calculates a steering command value to suppress the vehicle 1 from deviating from its driving lane. In step S2, the steering control unit 21 controls the steering angle of the vehicle 1 based on the steering command value.

[0048] In step S3, the lane departure operation determination unit 22 estimates whether or not there is a high probability of lane departure operation occurring. If there is no high probability of lane departure operation occurring (step S4: N), the process proceeds to step S6. If there is a high probability of lane departure operation occurring (step S4: Y), the process proceeds to step S5.

[0049] In step S5, the determination method determination unit 23 selects a second determination method as the determination method by the override determination unit 24. In the case of the second determination method, a larger number or types of steering parameters are selected than in the case of the first determination method. The process then proceeds to step S7. In step S6, the determination method determination unit 23 selects a first determination method as the determination method by the override determination unit 24. In the case of the first determination method, a smaller number or types of steering parameters are selected than in the case of the second determination method. The process then proceeds to step S7.

[0050] In step S7, the override determination unit 24 determines whether an override operation has been detected, depending on whether at least one of the determination conditions related to the steering parameters selected in step S5 or S6 is met. If no override operation is detected (step S7: N), the process proceeds to step S9. If an override operation is detected (step S7: Y), the process proceeds to step S8.

[0051] In step S8, the steering control unit 21 stops controlling the steering angle based on the steering command value from the lane departure prevention control and enables the driver to control the steering angle through override operations. In step S9, the steering control unit 21 continues to control the steering angle based on the steering command value from the lane departure prevention control.

[0052] (Second Embodiment) Next, the lane departure prevention device 10 of the second embodiment will be described. The configuration of the lane departure prevention device 10 of the second embodiment is the same as that of the lane departure prevention device 10 of the first embodiment, and the functional configuration of the controller 16 of the second embodiment is the same as that of the controller 16 of the second embodiment. For this reason, redundant explanations regarding identical or similar configurations and functions will be omitted.

[0053] In the second embodiment, the override determination unit 24 selects one or more steering parameters according to the determination method flag Fd, and detects an override operation by the driver when all of the determination conditions based on the selected steering parameters are met (i.e., when the result of the logical AND operation of these multiple determination conditions is "true"). When detecting an override operation, the override determination unit 24 selects fewer steering parameters or types when the second determination method is selected than when the first determination method is selected.

[0054] For example, the override determination unit 24 may determine that an override operation has occurred if the second determination method is selected in a situation where there is a high probability of lane departure operation, and at least the determination condition based on the steering angle θs is met. Alternatively, the override determination unit 24 may determine that an override operation has occurred if the first determination method is selected in a situation where there is a low probability of lane departure operation, and both the determination condition based on the steering angle θs and the determination condition related to the steering torque Ts are met.

[0055] The override determination unit 24 stops detecting override operations after a dead time DT has elapsed from the point when the state changes from the state in which override operations are detected to a state in which any one of the determination conditions based on the selected steering parameters is no longer met.

[0056] (Effects of the Embodiment) (1) In the lane departure prevention method, steering command values ​​are calculated to suppress the departure of the vehicle 1 from the driving lane, the steering angle of the vehicle 1 is controlled based on the steering command values, it is estimated whether or not there is a high probability of a lane departure operation, which is an operation by the driver that causes the vehicle 1 to deviate from the driving lane, and one or more steering parameters representing the state of the driver's steering operation are selected according to whether or not there is a high probability of a lane departure operation, and when at least one of the judgment conditions based on each of the selected steering parameters is met, an override operation by the driver is detected, and when an override operation is detected, the control of the steering angle based on the steering command value is stopped, and the driver's steering angle operation is enabled. The number or type of steering parameters selected when it is estimated that there is a high probability of a lane departure operation is greater than the number or type of steering parameters selected when it is estimated that there is a low probability of a lane departure operation. This makes it possible to adjust the trade-off between early detection of an override operation and false judgment in the detection of an override operation based on steering parameters representing the state of the driver's steering operation.

[0057] (2) The detection of override operations may be stopped after a period of inactivity has elapsed from the point when the state changes from one in which an override operation is detected to a state in which all of the judgment conditions based on each of the selected steering parameters are no longer met. This can suppress frequent changes in the detection results of override operations.

[0058] (3) The judgment condition may be a condition that is met when the selected steering parameter is equal to or greater than the judgment threshold set for each steering parameter. The judgment threshold set when there is a high probability of lane departure operation may be lower than the judgment threshold set when there is a low probability of lane departure operation. This allows for adjustment of the trade-off between early detection of override operation and false judgment.

[0059] (4) The steering parameter selected when the likelihood of lane departure is low may be a single steering parameter. This can suppress the occurrence of misjudgments. (5) One or more of the following may be selected as steering parameters: steering command value, steering angle, steering angular velocity, steering angular acceleration, steering torque, and time derivative of steering torque. This can detect override operations. (6) When vehicle 1 changes lanes from the second lane merging into the first lane to the first lane, when there is an obstacle in the direction of vehicle 1's travel, or when an oncoming vehicle approaches vehicle 1, it may be estimated that the likelihood of lane departure is higher than in other cases. This can estimate the likelihood of lane departure.

[0060] (7) If there is a high probability that lane departure will occur, an override operation may be detected when at least the steering torque determination condition is met as a determination condition for steering parameters. This allows for early detection of an override operation based on steering torque, which is detected earlier than the change in steering angle. (8) An override operation by the driver may be detected when all of the determination conditions based on each of the selected steering parameters are met. The number or types of steering parameters selected when there is an estimated high probability that lane departure will occur may be less than the number or types of steering parameters selected when there is an estimated low probability that lane departure will occur. This allows for adjustment of the trade-off between early detection of an override operation and false detection.

[0061] (Modified Version) (1) The lane departure operation determination unit 22 may determine a first situation in which there is a high probability that a lane departure operation will occur, a second situation in which there is a higher probability that a lane departure operation will occur than in the first situation, and a third situation in which there is a low probability that a lane departure operation will occur. For example, in a situation in which the vehicle 1 changes lanes from a merging lane to a main lane, the lane departure operation determination unit 22 may recognize the lane width W1 of the merging lane at the current position of the vehicle 1 traveling in the merging lane from the image of the area in front of the vehicle 1 taken by the camera 13. The lane departure determination unit 22 may determine that the current situation in which the vehicle 1 is located is the second situation when the lane width W1 is less than the first lane width threshold, determine that the current situation in which the vehicle 1 is located is the third situation when the lane width W1 is greater than the second lane width threshold which is greater than the first lane width threshold, and determine that the current situation in which the vehicle 1 is located is the first situation when the lane width W1 is greater than or equal to the first lane width threshold and less than or equal to the second lane width threshold.

[0062] Furthermore, for example, in a situation where an obstacle exists in the direction of travel of the vehicle 1, the deviation operation determination unit 22 may recognize the occupied width W2 of the roadway occupied by the obstacle from the image of the area in front of the vehicle 1 captured by the camera 13. The deviation operation determination unit 22 may determine that the current situation in which the vehicle 1 is located is a third situation when the occupied width W2 is less than a first occupied width threshold, determine that the current situation in which the vehicle 1 is located is a second situation when the occupied width W2 is greater than a second occupied width threshold which is greater than the first occupied width threshold, and determine that the current situation in which the vehicle 1 is located is a first situation when the occupied width W2 is greater than or equal to the first occupied width threshold and less than or equal to the second occupied width threshold.

[0063] Furthermore, for example, in a situation where an oncoming vehicle is approaching the vehicle 1, the deviation operation determination unit 22 may recognize the lateral distance G between the oncoming vehicle and the vehicle 1 from the image of the area in front of the vehicle 1 captured by the camera 13. The deviation operation determination unit 22 may determine that the current situation in which the vehicle 1 is located is a second situation when the lateral distance G is less than a first distance threshold, determine that the current situation in which the vehicle 1 is located is a third situation when the lateral distance G is greater than a second distance threshold which is greater than the first distance threshold, and determine that the current situation in which the vehicle 1 is located is a first situation when the lateral distance G is greater than or equal to the first distance threshold and less than or equal to the second distance threshold.

[0064] In the first embodiment, the override determination unit 24 selects a greater number or variety of steering parameters to be used to determine the detection of an override operation in the second situation than in the first situation. Furthermore, it selects a greater number or variety of steering parameters to be used to determine the detection of an override operation in the first situation than in the third situation.

[0065] In the second embodiment, the override determination unit 24 selects fewer steering parameters or types of steering parameters to be used to determine the detection of an override operation in the second situation than in the first situation. Furthermore, it selects fewer steering parameters or types of steering parameters to be used to determine the detection of an override operation in the first situation than in the third situation. This allows for adjustment of the trade-off between early detection and false determination of an override operation depending on the degree of possibility of lane departure.

[0066] (2) The override determination unit 24 may set the determination threshold set for each steering parameter to a lower value in the second situation than in the first situation. Also, it may set the determination threshold set for each steering parameter to a lower value in the first situation than in the third situation. This allows the trade-off between early detection of override operation and false determination to be adjusted according to the degree of possibility of lane departure.

[0067] All examples and conditional terms set forth herein are intended for educational purposes to help the reader understand the concepts given by the inventors for the advancement of the invention and the art, and should be interpreted without limitation to the examples and conditions specifically described herein, as well as the configuration of examples relating to demonstrating the superiority and inferiority of the invention. Although embodiments of the invention are described in detail, it should be understood that various changes, substitutions, and modifications are possible without departing from the spirit and scope of the invention.

[0068] 1...Vehicle, 10...Lane Departure Prevention Device, 11...Vehicle Speed ​​Sensor, 12...Steering Angle Sensor, 13...Camera, 14...Object Detection Sensor, 15...Steering Torque Sensor, 16...Controller, 16a...Processor, 16b...Storage Device, 17...Steering Angle Control Actuator, 20...Steering Command Value Calculation Unit, 21...Steering Control Unit, 22...Deviation Operation Determination Unit, 23...Determination Method Determination Unit, 24...Override Determination Unit

Claims

1. A method for preventing lane departure, characterized by: calculating a steering command value to suppress the departure of the vehicle from its driving lane; controlling the steering angle of the vehicle based on the steering command value; estimating whether there is a high probability of a lane departure operation being performed, which is an operation by the driver to intentionally deviate the vehicle from its driving lane; selecting one or more steering parameters that represent the state of the driver's steering operation depending on whether there is a high probability of a lane departure operation being performed; detecting an override operation by the driver when at least one of the judgment conditions based on each of the selected steering parameters is met; stopping the control of the steering angle based on the steering command value when an override operation is detected, thereby enabling the driver to operate the steering angle; and the number or type of steering parameters selected when it is estimated that there is a high probability of a lane departure operation being performed is greater than the number or type of steering parameters selected when it is estimated that there is a low probability of a lane departure operation being performed.

2. The lane departure prevention method according to claim 1, characterized in that the detection of the override operation is stopped after a period of inactivity has elapsed from the point in time when the state changes from the state in which the override operation is detected to a state in which all of the determination conditions based on each of the selected steering parameters are not met.

3. The lane departure prevention method according to claim 1, characterized in that the determination condition is a condition that is met when the selected steering parameter is equal to or greater than a determination threshold set for each steering parameter, and the determination threshold set when there is a high probability that the lane departure operation will occur is lower than the determination threshold set when there is a low probability that the lane departure operation will occur.

4. The lane departure prevention method according to claim 1, characterized in that the steering parameter selected when the likelihood of the lane departure operation occurring is low is a single steering parameter.

5. The lane departure prevention method according to claim 1, characterized in that one or more of the steering command value, steering angle, steering angular velocity, steering angular acceleration, steering torque, and time derivative of the steering torque are selected as the steering parameters.

6. The lane departure prevention method according to claim 1, characterized in that it is estimated that the likelihood of the lane departure operation occurring is higher than in other cases when the vehicle changes lanes from a second lane merging into the first lane to the first lane, when there is an obstacle in the direction of travel of the vehicle, or when an oncoming vehicle approaches the vehicle.

7. A method for preventing lane departure according to claim 1, characterized in that a first situation in which there is a high probability that the lane departure operation will occur and a second situation in which the probability of the lane departure operation occurring is higher than that of the first situation, and the number or type of steering parameters selected in the second situation is greater than the number or type of steering parameters selected in the first situation.

8. The lane departure prevention method according to claim 3, characterized in that a first situation in which there is a high probability that the lane departure operation will occur and a second situation in which the probability of the lane departure operation occurring is higher than that of the first situation, and the determination threshold set in the second situation is lower than the determination threshold set in the first situation.

9. The lane departure prevention method according to claim 1, characterized in that, if there is a high probability that the lane departure operation will occur, the override operation is detected when at least the determination condition relating to steering torque is met as a determination condition relating to steering parameters.

10. A method for preventing lane departure, characterized by: calculating a steering command value to suppress the departure of the vehicle from its driving lane; controlling the steering angle of the vehicle based on the steering command value; estimating whether there is a high probability of a lane departure operation being performed, which is an operation by the driver to intentionally deviate the vehicle from its driving lane; selecting one or more steering parameters that represent the state of the driver's steering operation depending on whether there is a high probability of a lane departure operation being performed; detecting an override operation by the driver when all of the respective judgment conditions based on the selected steering parameters are met; stopping the control of the steering angle based on the steering command value when an override operation is detected, thereby enabling the driver to operate the steering angle; and the number or type of steering parameters selected when it is estimated that there is a high probability of a lane departure operation being performed is less than the number or type of steering parameters selected when it is estimated that there is a low probability of a lane departure operation being performed.

11. The lane departure prevention method according to claim 11, characterized in that, when there is a high probability that the lane departure operation will occur, the override operation is detected when at least the determination condition relating to steering torque is met as a determination condition relating to steering parameters.

12. The lane departure prevention method according to 11, characterized in that, if the likelihood of the lane departure operation being performed is low, the override operation is detected when both the determination condition for steering torque and the determination condition for steering angle are met as determination conditions for the steering parameters.

13. A lane departure prevention device comprising a controller that performs the following: a process of calculating a steering command value to suppress the departure of the vehicle from its driving lane; a process of controlling the steering angle of the vehicle based on the steering command value; a process of estimating whether or not there is a high probability of a lane departure operation being performed, which is an operation by the driver that causes the vehicle to intentionally deviate from its driving lane; a process of selecting one or more steering parameters that represent the state of the driver's steering operation, depending on whether or not there is a high probability of a lane departure operation being performed; a process of detecting an override operation by the driver when at least one of the judgment conditions based on each of the selected steering parameters is met; and a process of stopping the control of the steering angle based on the steering command value and enabling the driver to operate the steering angle when an override operation is detected, wherein the number or type of steering parameters selected when it is estimated that there is a high probability of a lane departure operation being performed is greater than the number or type of steering parameters selected when it is estimated that there is a low probability of a lane departure operation being performed.

14. A lane departure prevention device comprising a controller that performs the following: a process of calculating a steering command value to suppress the departure of the vehicle from its driving lane; a process of controlling the steering angle of the vehicle based on the steering command value; a process of estimating whether or not there is a high probability of a lane departure operation being performed, which is an operation by the driver that causes the vehicle to intentionally deviate from its driving lane; a process of selecting one or more steering parameters that represent the state of the driver's steering operation, depending on whether or not there is a high probability of a lane departure operation being performed; a process of detecting an override operation by the driver when all of the respective judgment conditions based on the selected steering parameters are met; and a process of stopping the control of the steering angle based on the steering command value and enabling the driver to operate the steering angle when an override operation is detected, wherein the number or type of steering parameters selected when it is estimated that there is a high probability of a lane departure operation being performed is less than the number or type of steering parameters selected when it is estimated that there is a low probability of a lane departure operation being performed.

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