JP5853552B2 - Vehicle travel control device - Google Patents

Description

  The present invention relates to an apparatus for controlling traveling of a vehicle.

  2. Description of the Related Art Conventionally, a vehicular travel control device that performs lane tracking control for assisting a driver so that the host vehicle travels following a lane is known. For example, in the technique described in Patent Document 1, when the driver's steering operation intervenes for the purpose of correcting the track of the host vehicle in the traveling lane during the lane tracking control, the traveling target point is set in the traveling lane. By updating the vehicle in accordance with the change in the lateral position of the host vehicle, the track of the host vehicle can be corrected smoothly and the driver's uncomfortable feeling is reduced.

Japanese Patent Laid-Open No. 2007-261451

  However, when the driver intends to move from the outside of the lane toward the center of the lane due to the intervention of the steering operation, the driver needs to make fine adjustments to the steering operation. If it is not stable, the position of the host vehicle may fluctuate. Therefore, there is a problem that it is not easy to return to the center of the lane and the burden on the steering operation of the driver increases.

  The present invention has been made paying attention to the above problem, and during the lane tracking control, when the driver performs the steering operation for the purpose of moving toward the center of the lane, the burden of the steering operation of the driver is reduced. An object of the present invention is to provide a vehicular travel control device that can be reduced.

To achieve the above object, in the vehicle control system according to an embodiment of the present invention, in the lane keeping control, if it is determined that there is a return intention to lane center of the driver based on the steering state of the driver The driving target point was set at the center of the lane.

  Therefore, since the travel target point is set at the center of the lane according to the determined return intention, it is not necessary for the driver to make fine adjustments to the steering operation, and the host vehicle can be more easily directed toward the center of the lane. The burden of the driver's steering operation can be reduced.

1 is a system diagram illustrating a configuration of a vehicle steering system to which a vehicular travel control apparatus according to a first embodiment is applied. It is a block diagram which shows the structure of the control system of the traveling control apparatus for vehicles of Example 1. FIG. 4 is a flowchart illustrating a control process by the vehicle travel control apparatus according to the first embodiment. It is a figure explaining the effect | action of the vehicle travel control apparatus of Example 1 (when steering operation intervenes in the direction approaching one lane marking or the curve outer side). It is a figure explaining the effect | action of the vehicle travel control apparatus of Example 1 (when steering operation intervenes in the direction approaching a lane center, and there is no return intention to a lane center). It is a figure explaining the effect | action of the vehicle travel control apparatus of Example 1 (when the arrival point SP separated by the predetermined distance L0 ahead exceeds the lane center lm). It is a figure explaining the effect | action of the vehicle travel control apparatus of Example 1 (when arrival point SP 'which left | separated the predetermined distance L0 + Lc ahead exceeds the lane center lm).

[Example 1]
The vehicle travel control apparatus according to the first embodiment performs lane tracking control for causing the host vehicle to track the traveling lane. For this purpose, steering control is performed by applying a steering torque to a steering force transmission system. First, the configuration will be described. FIG. 1 is a schematic configuration diagram of a vehicle steering system to which the vehicle travel control apparatus according to the first embodiment is applied. As shown in FIG. 1, a steering mechanism 2 having a steering gear 2c is disposed on the front wheels 1L and 1R of the vehicle. The steering gear 2c is a general rack and pinion type, and the steering mechanism 2 includes a rack connected to the steering shafts of the front wheels 1L and 1R, a pinion meshing with the rack, and a steering provided with the pinion to the steering wheel 2a. And a steering shaft 2b that is rotated by torque.

  A steering actuator 3 that constitutes an automatic steering mechanism for automatically steering the front wheels 1L and 1R is disposed above the pinion of the steering shaft 2b. The steering actuator 3 includes a driven gear attached coaxially to the steering shaft 2b, a drive gear meshing with the driven gear, and an automatic steering motor that rotationally drives the drive gear. It is provided so that it can be generated. The steering actuator 3 drives the automatic steering motor in accordance with the drive signal from the control unit 10, whereby the steering mechanism 2 is controlled and steering is performed. A clutch mechanism is interposed between the automatic steering motor and the drive gear, and the clutch mechanism is engaged only during automatic steering control. Otherwise, the clutch mechanism is not engaged and the automatic steering motor is engaged. This rotational force is not input to the steering shaft 2b.

  The steering shaft 2b is provided with each sensor for detecting a steering state amount (steering torque T, steering angle θ), which is a parameter indicating the state of the steering operation of the driver (driver). Specifically, a steering torque sensor 4a that detects a steering torque T input to the steering shaft 2b by the driver's operation of the steering wheel 2a between the steering wheel 2a and the steering actuator 3, and rotation of the steering shaft 2b A steering angle sensor 4 b that detects the steering angle θ of the steering wheel 2 a from the corner is provided, and detection signals thereof are output to the control unit 10.

  The vehicle is provided with each sensor for detecting a vehicle motion state amount that is a parameter indicating the motion state of the vehicle. Specifically, a lateral acceleration sensor 5a that detects a lateral acceleration Gy that occurs in the host vehicle MC, a yaw rate sensor 5b that detects a yaw rate ψ 'that occurs in the host vehicle MC, the rotational speed of the wheels and the rotation on the output side of the transmission. A vehicle speed sensor 5 c that detects the vehicle speed V of the host vehicle MC by detecting the number is provided, and these detection signals are output to the control unit 10. Note that means for estimating the vehicle motion state quantity may be provided instead of each sensor for detecting the vehicle motion state quantity. For example, instead of providing the lateral acceleration sensor 5a, the lateral acceleration Gy may be estimated and calculated from the vehicle speed V and the steering angle θ.

  The vehicle is provided with a front monitoring camera 6a as a front external environment recognition sensor for detecting the position (traveling position) of the host vehicle MC in the traveling lane (the lane in which the host vehicle MC travels) l1. The front monitoring camera 6a is a monocular camera composed of, for example, a CCD camera or the like, and is configured so as to be able to photograph a traveling road several meters to several tens meters ahead of the host vehicle MC. The captured image of the front monitoring camera 6a is output to the control unit 10. The vehicle also detects a three-dimensional object (obstacle) around the host vehicle MC, and a front external field recognition sensor for detecting the degree of approach (distance) of the three-dimensional object (obstacle) to the host vehicle MC. A laser radar 6b is provided. The detection signal of the laser radar 6 b is output to the control unit 10. Note that not only the laser radar but also a stereo camera or the like may be used.

  The control unit 10 calculates the target trajectory M * that the host vehicle MC should travel on the travel path based on the supplied detection signals and calculated values. Further, the target steering angle θ * necessary for the host vehicle MC to travel along the target locus M * is calculated, and the actual steering angle θ detected by the steering angle sensor 4b matches the target steering angle θ *. Then, a drive signal is output to the steering actuator 3 to generate a steering angle at the front wheels 1L and 1R which are steered wheels of the vehicle. A target steering torque T * for traveling along the target locus M * is obtained, and the current supplied to the automatic steering motor of the steering actuator 3 is controlled, so that the steering torque T generated in the steering shaft 2b is the target steering. Control may be performed so as to match the torque T *.

  FIG. 2 is a block diagram showing a schematic configuration of a control system provided in the control unit 10. As shown in FIG. 2, the control unit 10 includes a lane recognition unit 101, a steering torque detection unit 102, a steering angle detection unit 103, a vehicle motion state detection unit 104, an obstacle recognition unit 105, and a driver intervention determination. Unit 106, lane center return intention determination unit 107, target trajectory calculation unit 108, target lateral position setting unit 109, and steering control unit 110.

  The lane recognition unit 101 detects, for example, a lane marker (lane marking line ln) such as a white line in the vicinity of the host vehicle MC from the image in front of the host vehicle MC taken by the front monitoring camera 6a to recognize the travel lane l1 and travel. The direction (yaw angle φ) of the host vehicle MC with respect to the lane 11 (specifically, the tangent to the lane division line ln), the lateral position (lateral position Y) of the host vehicle MC with respect to the reference travel line in the travel lane 11, and the travel lane The road curvature ρ of l1 is calculated.

The road curvature ρ is calculated as follows, for example. The lane recognition unit 101 first virtually sets a real space from the image taken by the front monitoring camera 6a, and arranges the host vehicle MC and the left and right lane markings ln on the real space. The origin is a curve representing the lane line ln with the x-axis in the traveling direction of the host vehicle MC and the y-axis in the left-right direction perpendicular to the traveling direction as a point on the road surface directly below the center position of the front monitoring camera 6a. Is approximated by a quadratic curve, that is, y = ax ² + bx + c, and 1 / 2a is calculated as the road curvature ρ at the position of the host vehicle MC. The quadratic curve approximation method may be obtained by, for example, extracting three points on the lane line ln and obtaining a quadratic curve passing through the three points, or extracting several points on the lane line ln. It may be calculated by the least square method.

  The lateral position Y is calculated as follows, for example. The lane recognition unit 101 extracts information that can be used as a reference travel line (for example, a center line, a side line, a guide rail, or the like drawn on the road surface) from the image captured by the front monitoring camera 6a, and extracts this information. A reference travel line is assumed based on the obtained information. In the first embodiment, the central portion (lane center lm) of the travel lane 11 is used as a reference travel line, and the lateral displacement (lateral distance) of the host vehicle MC from the reference travel line (lane center lm) is defined as a lateral position Y. To do. Specifically, based on the arrangement of the host vehicle MC and the reference travel line (lane center lm) set in the virtual real space, the lateral position of the host vehicle MC (origin) with respect to the lane center lm is determined from the lateral distance. Y is calculated.

  The steering torque detector 102 detects the steering torque T as a steering state quantity based on the input from the steering torque sensor 4a. The steering angle detection unit 103 detects the steering angle θ as the steering state quantity based on the input from the steering angle sensor 4b, and calculates the steering angular velocity (driver's steering speed) θ ′ based on the steering angle θ. The vehicle motion state detection unit 104 detects the lateral acceleration Gy, the yaw rate ψ ′, and the vehicle speed V as the motion state amount of the vehicle based on the inputs from the lateral acceleration sensor 5a, the yaw rate sensor 5b, and the vehicle speed sensor 5c. If the detected vehicle traveling state data has left and right directionality, either the left or right direction (for example, the left direction) may be set in advance as a positive direction. For example, the yaw rate ψ ′, the lateral acceleration Gy, the steering angle θ, and the yaw angle φ are positive when turning left, and the lateral position Y is positive when deviating leftward from the center lm of the traveling lane. To do.

  The obstacle recognizing unit 105 detects a three-dimensional object around the host vehicle MC (such as another vehicle in the lane 11 where the host vehicle MC travels or another vehicle in the lane 12 adjacent thereto) from the detection signal of the laser radar 6b. The position (lateral position x and front-rear position y) is detected, thereby grasping the congestion of the road around the host vehicle MC. Specifically, it is determined that the vehicle is congested when the lateral position (perpendicular to the traveling lane) position x of an adjacent vehicle existing within a predetermined range before and after the host vehicle MC is smaller than a predetermined value. For example, this is the case when the lane width is narrow and the density of the traveling lane 11 and the adjacent lane 12 is high, or when the adjacent vehicle is extremely close to the lane 11 side of the host vehicle MC even if the lane width is wide. Further, when the distance from the host vehicle MC to the surrounding three-dimensional object (an obstacle such as another vehicle) is short (the position of the three-dimensional object is within a predetermined range from the host vehicle MC), for example, a road such as a curb, a gutter or a wall When the distance between the boundary and the own vehicle MC is short, when a parked vehicle is present and the own vehicle MC approaches this, or when the oncoming vehicle approaches the own vehicle MC, it is determined that the vehicle is congested. .

  The target trajectory calculation unit 108 sets a travel target point GP of the host vehicle MC based on inputs from the lane recognition unit 101 and the target lateral position setting unit 109, and the target travel line of the host vehicle MC based on the travel target point GP. (Target locus M *) is calculated. Specifically, first, the target lateral position Y * of the host vehicle MC in the traveling lane 11 set by the target lateral position setting unit 109 described later (target value of the lateral separation amount of the host vehicle MC with respect to the lane center lm). Is read. Then, at the point P that is separated from the host vehicle MC by a predetermined distance L0 in the direction along the travel lane 11, the host vehicle MC should travel to a position that is laterally separated from the center lm by the target lateral position Y *. A target point GP is set. In the first embodiment, the travel distance when the host vehicle MC travels along the travel lane l1 at the current vehicle speed V for a predetermined time as the point P that is separated by a predetermined distance L0 in front of the host vehicle MC (front gazing point). Set a point ahead by distance). Similarly, when the detected travel lane 11 (the lane division line ln or the lane center lm) is curved, the travel target point GP is located at the position P that is laterally separated from the lane center lm by the target lateral position Y *. Set. In other words, a point obtained by extending the target lateral position Y * from the host vehicle MC in the direction of the traveling lane l1 by the predetermined distance L0 is defined as the traveling target point GP. The predetermined distance L0 is changed according to the vehicle speed V, the width of the traveling lane 11 and the road curvature ρ, and the degree of approach of the adjacent vehicle.

  When the travel target point GP is set, the target locus M * is determined on the assumption that the route of the host vehicle MC toward the travel target point GP is, for example, an arc. From the traveling direction of the host vehicle MC and the position of the travel target point GP on the point P, the curvature radius of the target locus M * is calculated as the target radius r *. The circular arc includes a case where the target radius r is infinite, that is, a straight line. Further, a target steering angle θ * for realizing the target radius r * is calculated based on the calculated target radius r *, vehicle speed V, and vehicle characteristic parameters of the host vehicle MC.

  The steering control unit 110 performs control for causing the steering actuator 3 to generate a steering torque T and causing the host vehicle MC to follow the traveling lane 11 independently of the driver's steering operation. Based on the input from the target trajectory calculation unit 108, a command is output to the steering actuator 3 and the steering control is performed, so that the travel target point GP (target lateral position Y *) travels along the target trajectory M *. To control the vehicle. Specifically, for example, based on the two-wheel model, the vehicle body slip angle β is calculated from the detected steering angle θ, the vehicle speed V, and the vehicle characteristic parameters of the vehicle MC. Subsequently, the self-aligning torque Tsa is calculated based on the vehicle body slip angle β, the detected yaw rate ψ ′, the steering angle θ, the vehicle speed V, and the vehicle characteristic parameters. Then, the calculated self-aligning torque Tsa is multiplied by a gain to calculate the first current It1. Further, the second current It2 is calculated by PD control so that the detected steering angle θ becomes the target steering angle θ *, and this is added to the first current It1 to calculate the control current It. The steering control unit 110 calculates a target steering angle θ * and a control current It for each control cycle, and outputs a drive signal to the steering actuator 3 based on the value of the control current It to generate a steering torque. The target yaw rate V / r * may be obtained from the target radius r * and the vehicle speed V, and the steering angle following the target yaw rate may be feedforward / feedback controlled, and is not particularly limited.

  Based on the input from the steering torque detection unit 102, the driver intervention determination unit 106 determines whether or not the driver has performed a steering operation during lane tracking control. Specifically, when the steering state amount (the magnitude of the steering torque T in the first embodiment | T |) exceeds a predetermined first threshold value (threshold value T1), it is determined that the driver has performed the steering operation, and the steering is performed. If the state quantity (| T |) is equal to or less than the first threshold value (threshold value T1), it is determined that the driver is not performing a steering operation. Note that the presence or absence of the driver's steering intervention may be determined using a steering state quantity (steering angle θ, steering angular velocity θ ′, etc.) other than the steering torque T. For example, the intervention of the steering operation may be determined based on the differential value θ ′ (that is, the steering speed) of the steering angle θ. Further, the intervention of the steering operation may be determined based on the duration of the steering torque T greater than a certain value. Further, the threshold value T1 for the steering torque T may be set and determined in combination.

  The lane center return intention determination unit 107 is configured to inform the driver of the lane center based on inputs from the lane recognition unit 101, the steering torque detection unit 102, the steering angle detection unit 103, the vehicle motion state detection unit 104, and the obstacle recognition unit 105. It is determined whether or not there is an intention to return to lm. Specifically, (1) the steering direction of the driver is the direction from the outside of the travel lane 11 (either the left or right side of the lane center lm) toward the lane center lm, and the steering state quantity (Example) 1 when the magnitude of the steering torque T | T |) exceeds a predetermined second threshold value T2 (> T1) larger than the first threshold value T1, or (2) in an estimated vehicle expected trajectory S. When the predetermined front arrival point SP exceeds the lane center lm from the outside of the travel lane l1, it is determined that the driver intends to return to the lane center lm.

  (1) When the driver's steering direction is the direction toward the lane center lm, the lane center return intention determination unit 107 determines the driver's lane center lm based on the steering torque T input from the steering torque detection unit 102. Determine your intention to return to Specifically, if the magnitude of the steering torque T exceeds the threshold value T2, it is determined that the driver intends to return. If the magnitude of the steering torque T is equal to or less than the threshold value T2, the driver does not intend to return. Is determined. In addition to the steering torque T, a steering angle θ, a steering angular velocity θ ′, or the like may be used as the steering state amount used for determining the return intention. Further, the intervention of the steering operation may be determined based on the duration of the steering torque T greater than a certain value. Further, the threshold value T2 for the steering torque T may be set and determined in combination. Further, in order to determine whether the driver's steering direction is a direction from the outside of the lane toward the center side, the direction (sign) of the steering torque T may be used, or the direction of change of the steering angle θ (steering angular velocity). The sign of θ ′ may be used.

  (2) Further, the lane center return intention determination unit 107 determines the driver's intention to return to the lane center lm based on the predicted trajectory S of the vehicle. First, the predicted trajectory S of the vehicle is estimated for each control cycle from the vehicle motion state quantity and the like. The estimated trajectory S is estimated as follows, for example. Since the travel locus of the vehicle is determined by the vehicle motion, the vehicle motion state such as the vehicle position, posture, vehicle speed V, yaw rate ψ ′, and the like (such as the steering angle and the driving force difference between the left and right wheels). The predicted trajectory S is calculated from the actual behavior of the vehicle in accordance with a control input for controlling the movement of the vehicle. Specifically, the lateral movement amount (based on the current vehicle position and traveling direction) at a point separated by a distance L ahead of the host vehicle MC is expressed as 0.5 × L ^ 2 × V × ψ ′. It is calculated by the following formula. Since this is a linear approximation, it may be determined strictly as an arc. Then, the expected trajectory S is obtained by changing the distance L from 0 to an arbitrary distance and superimposing it on the traveling road. The yaw angle φ and lateral position Y of the host vehicle MC with respect to the traveling lane l1 and the road curvature ρ of the traveling lane l1 indicate which position the estimated trajectory S is located with respect to the traveling lane l1 and which direction it is heading. It can be used as a parameter for determination. Since the travel locus is determined by the vehicle motion, it is preferable to consider the lateral acceleration and the yaw rate ψ ′ (or the vehicle motion model and the steering angle θ) as the lateral motion of the vehicle.

  Then, in the predicted trajectory S, the predicted arrival point SP that is separated from the current position of the vehicle forward by a predetermined distance L0 (similar to that used for calculating the target trajectory M *) along the travel lane 11 exceeds the lane center lm. (That is, when the vehicle moves to the side opposite to the current vehicle position side across the lane center lm), it is determined that the driver intends to return to the lane center lm. Note that when the predicted arrival point SP after a predetermined time from the current time exceeds the lane center lm in the predicted trajectory S of the vehicle, it may be determined that the driver intends to return to the lane center lm.

  Here, the lane center return intention determination unit 107 corrects the predicted arrival point SP ahead based on the steering angular velocity θ ′. Specifically, when the magnitude of the steering angular velocity θ ′ exceeds a predetermined threshold value, the correction distance Lc is added to the predetermined distance L0 for a predetermined time, whereby the predicted arrival point SP is set to a position SP ′ ahead. To correct. The predetermined time is preferably set until the steering angular velocity θ ′ becomes substantially zero or the sign of the steering angular velocity θ ′ is reversed (starts moving in the reverse direction).

  Further, the predicted arrival point SP is corrected based on the road curvature ρ of the traveling lane l1. Specifically, when the travel lane l1 curves in the same direction as the driver's steering operation, the predicted arrival point SP is set to a position SP ′ ahead by adding the correction distance Lc to the predetermined distance L0. to correct. When the driving lane l1 curves in the direction opposite to the driver's steering operation, the expected distance SP is further rearward (side closer to the host vehicle MC) by subtracting the correction distance Lc from the predetermined distance L0. It corrects to position SP '. More specifically, when the road curvature ρ is greater than or equal to a predetermined value (for example, greater than 0), the greater the road curvature ρ of the traveling lane 11 in the same direction as the driver's steering operation (the smaller the radius of curvature), the greater the predetermined value. While the correction distance Lc to be added to the distance L0 is set longer, the correction distance Lc to be subtracted from the predetermined distance L0 is set longer as the road curvature ρ of the travel lane l1 is larger in the opposite direction to the driver's steering operation.

  Further, when it is determined that the surroundings of the host vehicle MC are congested by obstacles such as other vehicles, the predicted arrival point SP is corrected to a more forward position SP ′ as described above. The expected arrival point SP may be corrected by means other than adding / subtracting the correction distance Lc, for example, by multiplying by a correction coefficient.

  The target lateral position setting unit 109 sets / changes the target lateral position Y * in the target trajectory calculation unit 108 based on inputs from the lane recognition unit 101, the driver intervention determination unit 106, and the lane center return intention determination unit 107. Specifically, when the device is started up or when the lane tracking control is resumed after being interrupted for some reason (for example, by turning right or left or changing lanes), the current target position Y * The horizontal position Y0 (detected in step 1) is set. In this case, the target trajectory calculation unit 108 is a position that is laterally separated from the lane center lm by the current lateral position Y0 (at the start of control) at a point P that is separated from the host vehicle MC by a predetermined distance L0. The travel target point GP is set to When the lane tracking control is interrupted as described above, the host vehicle MC is in a stage where the host vehicle MC has sufficiently entered the original lane 11 or the adjacent lane l2, for example, equivalent to one tire. It is preferable that the lane tracking control is restarted when the vehicle enters the inside of the lane line ln.

  The target lateral position setting unit 109 does not update the set target lateral position Y * while it is determined that there is no intervention of the driver's steering operation during lane tracking control. That is, even if the host vehicle MC moves left and right and the lateral position Y changes, the target lateral position Y * remains fixed at the set value Y0 unless it is determined that there has been steering intervention by the driver. I won't let you. On the other hand, if it is determined that the driver has intervened in the steering operation, the target lateral position Y * is set to the detected lateral position Y as long as it is determined that the driver does not intend to return to the center lane lm. Update. That is, the value of the lateral position Y (the distance between the lane center lm and the host vehicle MC in the control period) detected at each control period (sampling cycle) is set as the target lateral position Y *. Thus, the target lateral position Y * is updated in accordance with the change in the distance (lateral position Y) between the lane center lm and the host vehicle MC. Thereafter, when it is not determined that there has been an intervention of the driver's steering operation, the target lateral position Y * updated at that time, that is, the value of the lateral position Y detected when it was last determined that there was a steering intervention. The target lateral position Y * is fixed.

  Further, when it is determined that the driver has intervened in the steering operation, if it is determined that the driver intends to return to the lane center lm, the target lateral position Y * is set to 0 (lane center lm). To do. In this case, the target trajectory calculation unit 108 sets the travel target point GP at the center lm of the lane at the point P that is separated from the host vehicle MC by a predetermined distance L0 in the direction along the travel lane 11.

Next, the processing procedure of the arithmetic processing performed in the control unit 10 will be described with reference to the flowchart of FIG. This calculation process is executed as a timer interrupt process every predetermined time (for example, 10 msec).
First, in step S1, the current position of the vehicle and the road shape are acquired. Specifically, the lane recognition unit 101 calculates the lateral displacement Y of the host vehicle MC from the center lm of the lane, the yaw angle φ of the host vehicle MC with respect to the travel lane l1, and the road curvature ρ of the travel lane l1.
Next, the process proceeds to step S2, and the obstacle recognition unit 105 acquires the positions of surrounding obstacles.
Next, the process proceeds to step S3, and the vehicle motion state quantity is acquired. Specifically, the vehicle motion state detection unit 104 detects the yaw rate ψ ′, the lateral acceleration Gy, and the vehicle speed V.
Next, the process proceeds to step S4, where the steering angle detector 103 detects the steering angle θ and calculates the steering angular velocity θ ′. For example, the steering angular velocity θ ′ is calculated based on the read previous value and current value of the steering angle θ.
Next, the process proceeds to step S5, where the steering torque detector 102 detects the steering torque T.
Next, the process proceeds to step S6, where the driver intervention determination unit 106 determines the presence or absence of the driver's steering operation. Specifically, when the magnitude | T | of the steering torque T exceeds the first threshold value T1, it is determined that the driver has performed the steering operation, and the process proceeds to step S7, where | T | is equal to or less than T1. Then, it is determined that the driver is not performing the steering operation, and the process proceeds to step S12.
In steps S7 to S9, the lane center return intention determination unit 107 determines whether or not the driver intends to return to the lane center lm.
In step S7, it is determined whether or not the driver's steering direction is a direction from the outside of the travel lane 11 toward the center lm side. If YES, the process proceeds to step S8, and if NO, the process proceeds to step S9. .
In step S8, it is determined whether or not the magnitude | T | of the steering torque T exceeds the second threshold value T2. If YES, it is determined that the driver intends to return to the center lm of the lane. The process proceeds to S10, and if NO, the process proceeds to Step S9.
In step S9, it is determined whether or not the arrival point SP ahead in the predicted trajectory S of the vehicle exceeds the lane center lm. If YES, it is determined that the driver intends to return to the lane center lm. The process proceeds to S10, and if NO, it is determined that there is no return intention, and the process proceeds to Step S11.
In step S10, the target lateral position setting unit 109 sets (changes) the target lateral position Y * to 0 (lane center lm), and the process proceeds to step S12.
In step S11, the target lateral position setting unit 109 sets the target lateral position Y * to the lateral position Y detected in step S1, and the process proceeds to step S12.
In step S12, the target trajectory calculation unit 108 sets the travel target point GP based on the target lateral position Y *, calculates the target trajectory M * and the target steering angle θ * based on the travel target point GP, and then proceeds to step S13. Transition.
In step S13, the steering control unit 110 outputs a drive signal to the steering actuator 3 so as to realize the target locus M * and the target steering angle θ * calculated in step S12.

[Action]
Next, the operation based on the control process will be described. FIGS. 4-7 is a figure for demonstrating the effect | action of the vehicle travel control apparatus of Example 1, and is the top view which looked at the vehicle MC which is drive | working the lane 11 from the sky. In the figure, the magnitude of the arrow in the yaw direction of the vehicle MC intuitively indicates the magnitude of the steering torque T generated by the driver's steering operation.

During lane tracking control, a target travel line (target trajectory M *) of the host vehicle MC is determined from the travel target point GP for each control period (step S12), and the steering actuator 3 performs automatic steering based on the target travel line (S13). . The host vehicle MC travels on the target trajectory M * (calculated from the travel target point GP) in a certain control cycle for the control cycle, and on the newly calculated target trajectory M * in the next control cycle. Drive for the control period. In this way, the host vehicle MC follows a smooth trajectory so as to continuously follow the travel target point GP, thereby performing lane tracking control.
During lane tracking control, if there is no intervention of the driver's steering operation, the flow proceeds from step S1 to S6 → S12 → S13, the target lateral position Y * is set to a fixed value without updating, and the travel target point GP is set. The distance from the center lm of the lane is kept constant (S12). Therefore, when the lane center lm changes for each control cycle, the position of the travel target point GP also changes accordingly, but the distance (lateral position Y) from the lane center lm is kept constant, so that the host vehicle MC Runs following the reference running line (lane center lm).

When the driver operates the steering wheel 2a for the purpose of correcting the track of the host vehicle MC in the traveling lane l1 during the lane tracking control, the flow proceeds to steps S1 to S6 → S7, and the driver's lane It is determined whether or not there is an intention to return to the center lm (S7 to S9).
If it is determined that the driver does not intend to return to the lane center lm during the steering operation, steps S1 to S6 → S7 → S9 → S11 → S12 → S13 (or steps S1 to S6 → S7 → S8 → S9 → S11). → S12 → S13). During the intervention of the steering operation, the distance (target lateral position Y *) of the travel target point GP from the lane center lm is determined between the lane center lm and the host vehicle MC for each control cycle. It is updated according to the variation of the distance (lateral position Y) (S11). For each control cycle, the target trajectory M * is determined based on the updated target lateral position Y *, and steering control is performed.

  As shown in FIG. 4, when a steering operation intervenes in one control cycle in a direction approaching one lane marking line ln (on the same side as the own vehicle with respect to the lane center lm) or in a direction outside the curve, The target lateral position Y * is set to the lateral position Y detected in the control cycle, the target trajectory M * is determined based on the set target lateral position Y *, and the target steering angle θ * corresponding to the target trajectory M * is realized. Steering control is performed. Thus, in order to update the target lateral position Y * for each control cycle, the actual trajectory of the vehicle under control is gradually approaching the one lane line ln according to the driver's steering operation, Or it will gradually go to the outside of the curve.

  As shown in FIG. 5, when a steering operation intervenes in a direction approaching the lane center lm in a certain control cycle and there is no intention to return to the lane center lm, that is, the driver approaches the lane center lm. When fine adjustment is in progress (for example, the steering angle θ is small and the steering torque T is small), the target lateral position Y * is set to the lateral position Y detected in the control cycle, and the target is set based on the set target lateral position Y *. The trajectory M * is determined, and steering control is performed so as to realize the target steering angle θ * corresponding to the target trajectory M *. Since the target lateral position Y * is updated at each control cycle, the actual trajectory of the vehicle being controlled gradually approaches the lane center lm according to the driver's steering operation.

As described above, since a relatively weak automatic steering force is generated so that the host vehicle MC is directed in the traveling direction of the travel lane l1, it is easy to keep the vehicle posture with respect to the travel lane l1 constant.
When the determination that the steering operation is present is completed, the process proceeds again from step S1 to S6 → S12 → S13. Therefore, the lateral position Y detected in the control cycle (S1) when the intervention of the steering operation is completed is the target lateral position Y. * Is fixed (S12), a target locus M * is determined based on the target lateral position Y *, and steering control is performed. As described above, since normal lane tracking control is activated immediately after the intervention of the steering operation, the driver adjusts the target lateral position Y * as described above in a state in which the vehicle behavior is stable and the steering is reduced. Can be done by operation.

If it is determined that the driver intends to return to the lane center lm during the steering operation, steps S1 to S6 → S7 → S8 → S10 → S12 → S13 (or steps S1 to S6 → S7 → S8 → S9 → S10). → S12 → S13, or steps S1 to S6 → S7 → S9 → S10 → S12 → S13). During the intervention of the steering operation, the distance of the travel target point GP from the lane center lm (target lateral position Y *) ) Is set to 0 (S10). In each control cycle, a target locus M * is determined based on the set target lateral position Y * = 0, and steering control is performed.
Specifically, when the steering operation intervenes in a direction approaching the center lm of the lane and the magnitude | T | of the steering torque T exceeds the second threshold T1, or when the estimated trajectory S is reached in the forward direction When the point SP exceeds the lane center lm, the target lateral position Y * is set to 0 in each control cycle, the target trajectory M * is determined based on the set target lateral position Y * = 0, and the target trajectory M * Steering control is performed so as to realize the target steering angle θ * according to the above. Therefore, the trajectory of the actual host vehicle MC being controlled quickly approaches the lane center lm.

Thus, for example, when the lane following control is performed with the target lateral position Y * corrected from the center lm of the lane to the outside, the corrected steering of the driver from the outside of the lane to the inside (lane center direction). Is determined, the driver's intention to return to the lane center lm is determined, and if it is determined that there is a return intention, the target lateral position Y * is set to the lane center lm. Therefore, in order to return the target lateral position Y * to the lane center lm, it is not necessary for the driver to perform fine correction steering (fine adjustment of the steering operation), so that the center of the lane can be more easily set regardless of changes in the road shape. You can head closer. Note that the target lateral position Y * may be set to the lane center lm as soon as it is determined that the return intention is intended, or after the determination that the return intention is intended, the target lateral position Y * gradually becomes the lane center over a predetermined time. You may set so that it may transfer to lm.
Specifically, based on a second steering operation intervention determination threshold value T2 that is larger than a threshold value (first threshold value T1) for determining steering operation intervention for simply (fine) adjusting the target lateral position Y *. The driver intends to return to the center lm of the lane. Thus, since the return intention determination to the lane center lm is performed based on the steering state quantity (steering torque T or the like), the return intention can be determined more easily.

  In addition, as shown in FIG. 6, the arrival point SP, which is separated from the current position by a predetermined distance L0 in the predicted trajectory S of the host vehicle MC estimated from the vehicle motion state quantity or the like, is beyond the lane center lm. (Left from the center of the lane when traveling to the right, right from the center of the lane when traveling toward the left. Note that “lane center lm” is not a strict center line but may have a predetermined width including the center line.) If this happens, it is determined that the driver intends to return to the center of the lane. As described above, since the return determination to the lane center lm is performed based on the actual vehicle behavior and the running road shape, the steering state quantity (steering torque T or the like) is unlikely to occur due to the influence of disturbance such as a single slope (cross slope). Even in the situation, it is possible to more reliably determine the intention to return to the lane center lm.

  Further, as shown in FIG. 7, in estimating the predicted arrival point SP that is separated from the current position of the host vehicle MC by a predetermined distance L0 forward along the travel lane 11 in the predicted trajectory S of the host vehicle MC, By adding the correction distance Lc to the predetermined distance L0 for a predetermined time after the state where the magnitude of θ ′ exceeds the predetermined threshold is detected, the predicted arrival point SP is corrected to the position SP ′ ahead. . As a result, even when the driver's steering operation (steering angle θ) is small and the curvature of the predicted locus S is small (the radius of curvature is large), the predicted arrival point SP ′ exceeds the lane center lm on the opposite side. It becomes easy to move. That is, when the magnitude of the steering angular velocity θ ′ exceeds the threshold value, the sensitivity of the driver's intention to return to the lane center lm is improved for a predetermined time. For this reason, for example, from the time when the steering operation amount (steering angle θ) is small, it is possible to quickly determine whether or not the driver intends to return to the lane center lm. In this way, by reflecting the amount of change in the steering operation in the return intention determination parameter (predetermined distance L0) and correcting it, the return intention to the lane center lm can be determined more accurately.

  Further, when the road curvature ρ of the traveling lane 11 is equal to or greater than a predetermined value, the correction distance Lc to be added to the predetermined distance L0 is set longer as the road curvature ρ is larger in the same direction as the driver's steering operation. The correction distance Lc to be subtracted from the predetermined distance L0 is set longer as ρ is larger in the opposite direction to the driver's steering operation. As a result, even when the driving lane 11 is curved in the same direction as the driver's steering operation, and the degree of the curve is large, the predicted arrival point SP ′ easily moves to the opposite side beyond the lane center lm. The sensitivity of the driver's intention to return to the center lm of the lane is improved. That is, as the road curvature ρ increases in the same direction as the driver's steering operation, the amount of steering operation required to return the vehicle to the inside (lane center side) from the target locus increases. Therefore, when the parameter (predetermined distance L0) used for the determination of the return intention is a fixed value, the accuracy required for the steering operation required for the determination of the return intention to the lane center lm is required (the road curvature ρ is the driving If it is larger in the direction opposite to the person's steering operation, the opposite is true). On the other hand, in the first embodiment, the determination parameter is changed to a direction in which the sensitivity of the return intention determination becomes higher as the road curvature ρ is larger in the same direction as the driver's steering operation, depending on the road condition. As a result, in a situation where the amount of steering operation required to return to the lane center lm becomes large, even if the driver's steering operation intended for return is somewhat inaccurate, the switching of the travel target point GP (to the lane center lm) is performed. ) Will be performed quickly, and the driver will be able to travel with peace of mind. In this way, by reducing the influence on the return intention determination by the traveling environment, it is possible to determine the return intention to the lane center lm more reliably.

  Further, when the surroundings of the host vehicle MC are congested with obstacles such as other vehicles, the predicted arrival point SP is corrected to a more forward position SP ′ by adding the correction distance Lc to the predetermined distance L0. . Thereby, the sensitivity of the driver's intention to return to the lane center lm is improved. That is, when it is determined that the surroundings of the host vehicle MC are congested, it is estimated that the driver wants to return the traveling position to the lane center lm due to a change in surrounding road conditions. Therefore, in such a case, it is determined that there is a return intention even if the driver does not complete the correction of the travel target point GP accurately. As a result, the switching of the travel target point GP (return to the lane center lm) is performed quickly, so that the driver can travel with peace of mind.

〔effect〕
Hereinafter, effects of the vehicle travel control apparatus of the first embodiment will be listed.
(1) Lateral position detection means (lane recognition unit 101) for detecting the current lateral position Y of the host vehicle MC in the lane 11 where the host vehicle MC travels, and the driver's steering state quantity (steering torque T, steering angle θ) Steering state detection means (steering torque detection unit 102, steering angle detection unit 103), and vehicle motion state detection means (vehicle) for detecting the motion state quantity (yaw rate ψ ′, vehicle speed V, etc.) of the host vehicle MC. The movement state detection unit 104) sets the target lateral position Y * of the host vehicle MC in the lane 11 where the host vehicle MC travels, and controls and detects the host vehicle MC to travel the target lateral position Y *. When the steering state quantity (steering torque T) exceeds the first threshold value (threshold value T1), the target lateral position Y * is updated in accordance with the detected lateral position Y, and then the detected steering state quantity is When the threshold value is 1 or less, the lateral position Y detected at that time Lane tracking control means for fixing the target lateral position Y * (driver intervention determination unit 106, target lateral position setting unit 109, target locus calculation unit 108, steering control unit 110), and detected steering state amount (steering torque T) Alternatively, the vehicle has lane center return intention determination means (lane center return intention determination unit 107) that determines the driver's intention to return to the lane center lm based on the vehicle motion state quantity (yaw rate ψ ', vehicle speed V), and lane tracking control. The means (target lateral position setting unit 109) sets the target lateral position Y * to the lane center lm when it is determined that the driver intends to return to the lane center lm, and the lane center return intention determination means The steering direction of the person is from the outside of the lane 11 toward the center lm, and the detected steering state amount (steering torque T) exceeds the second threshold (threshold T2) larger than the first threshold. Or detected vehicle movement When a predetermined forward arrival point (expected arrival point) SP in the predicted trajectory S of the host vehicle MC estimated from the state quantity (yaw rate ψ ′, vehicle speed V) exceeds the lane center lm, the driver moves toward the lane center lm. It is determined that there is a return intention.
Therefore, during the lane tracking control, when the driver intervenes in the steering operation for the purpose of moving toward the center lm of the lane, the driver does not need to make fine adjustments in the steering operation, and the lane center is more easily controlled. Since it is possible to head toward lm, the burden on the steering operation of the driver can be reduced.

(2) The steering state detection means (steering angle detection unit 103) detects the steering speed (steering angular speed θ ′) of the driver, and the lane center return intention determination means (lane center return intention determination unit 107) is detected. When the magnitude of the steering speed exceeds a predetermined threshold, the front arrival point SP is corrected to a more forward position for a predetermined time.
Therefore, since the intention to return to the lane center lm can be determined more accurately or quickly, the burden on the driver's steering operation can be further reduced.

(3) Curvature detection means (lane recognition unit 101) for detecting the curvature ρ of the lane 11 on which the host vehicle MC travels is provided, and the lane center return intention determination means (lane center return intention determination unit 107) As ρ is larger in the same direction as the driver's steering direction, the position of the front arrival point SP is corrected to a more forward position.
Therefore, since the intention to return to the lane center lm can be determined more reliably or quickly, the burden on the driver's steering operation can be further reduced.

(4) Provided with obstacle detection means (obstacle recognition unit 105) for detecting the position of obstacles around the host vehicle MC, the lane center return intention determination means (lane center return intention determination unit 107) is detected. When the position of the obstacle is within a predetermined range from the host vehicle MC, the position of the front arrival point SP is corrected to a more forward position.
Therefore, since the intention to return to the lane center lm can be determined more quickly, the burden on the steering operation of the driver can be further reduced.

[Other Examples]
As mentioned above, although this invention has been demonstrated based on Example 1, it is not restricted to the said Example but another structure is also included in this invention.
For example, the vehicle travel control device of the present invention can be applied to any vehicle equipped with any steering mechanism or automatic steering mechanism (steering actuator) as long as it can perform steering control. For example, the steering actuator for automatically steering the wheel may be an actuator of a power steering device that generates a steering assist torque in the steering mechanism. In addition, a steering reaction force actuator that generates a steering reaction torque on the steering shaft (steering wheel) may be used, and the vehicle travel control device automatically applies the steering reaction torque to the traveling lane by applying the steering reaction torque to the steering force transmission system. It may be a control device that supports a driver's steering operation in order to follow the vehicle. Further, the means (steering actuator) for performing the steering control is not limited to the one that applies the steering torque to the steering force transmission system, and for example, a driving / braking actuator that generates a driving force or a braking force on each wheel is used. Steering control may be realized by controlling the braking / driving force.
In the first embodiment, the lane center lm is used as a reference in order to detect the current lateral position Y or set the target lateral position Y *. However, the present invention is not limited to this. For example, the (left and right) lane markings ln are It may be a reference, or a ratio of the distance of the host vehicle MC from the lane line ln to the road width of the lane (calculated from the left and right lane line ln) may be used as a reference.

101 Lane recognition unit (lateral position detection means)
102 Steering torque detector (steering state detector)
103 Steering angle detector (steering state detector)
104 Vehicle motion state detection unit (vehicle motion state detection means)
106 Driver intervention determination unit (lane tracking control means)
107 Lane center return intention determination unit (lane center return intention determination means)
108 Target locus calculation unit (lane tracking control means)
109 Target lateral position setting unit (lane tracking control means)
110 Steering control unit (lane tracking control means)
l1 Lane MC

Claims (4)

Lateral position detecting means for detecting the current lateral position of the host vehicle in the lane in which the host vehicle is traveling;
Steering state detection means for detecting the amount of steering state of the driver ;
Setting a target lateral position of the host vehicle in the lane which the vehicle is traveling, to control the vehicle to travel the target lateral position, when the pre-Symbol steering state quantity exceeds the first threshold value, it is detected updates the target lateral position to suit the lateral position, then, before Symbol the steering state quantity falls below the first threshold, the lane keeping control for fixing the target lateral position of the detected lateral position that time Means and
The lane tracking control means is configured to detect the target when the driver's steering direction is a direction from the outside of the lane toward the center and the steering state quantity exceeds a second threshold value that is larger than the first threshold value. A vehicle travel control device characterized in that the lateral position is set at the center of the lane. Lateral position detecting means for detecting the current lateral position of the host vehicle in the lane in which the host vehicle is traveling;
Steering state detection means for detecting the amount of steering state of the driver;
Vehicle motion state detection means for detecting the amount of motion state of the host vehicle;
The target lateral position of the host vehicle in the lane in which the host vehicle is traveling is set, the host vehicle is controlled to travel in the target lateral position, and the detected lateral state is detected when the steering state quantity exceeds a predetermined threshold. Lane tracking control means for updating the target lateral position in accordance with the position, and then fixing the target lateral position to the lateral position detected at that time when the steering state quantity is equal to or less than the predetermined threshold;
Curvature detection means for detecting the curvature of the lane in which the host vehicle travels,
The lane tracking control means is
When a predetermined forward arrival point in the predicted trajectory of the host vehicle estimated from the vehicle motion state quantity exceeds the lane center, the target lateral position is set at the lane center,
The vehicle travel control apparatus , wherein the front arrival point is corrected to a more forward position as the curvature is larger in the same direction as the driver's steering direction . Lateral position detecting means for detecting the current lateral position of the host vehicle in the lane in which the host vehicle is traveling;
Steering state detection means for detecting the amount of steering state of the driver;
Vehicle motion state detection means for detecting the amount of motion state of the host vehicle;
The target lateral position of the host vehicle in the lane in which the host vehicle is traveling is set, the host vehicle is controlled to travel in the target lateral position, and the detected lateral state is detected when the steering state quantity exceeds a predetermined threshold. Lane tracking control means for updating the target lateral position in accordance with the position, and then fixing the target lateral position to the lateral position detected at that time when the steering state quantity is equal to or less than the predetermined threshold;
An obstacle detection means for detecting the position of an obstacle around the host vehicle,
The lane tracking control means is
When a predetermined forward arrival point in the predicted trajectory of the host vehicle estimated from the vehicle motion state quantity exceeds the lane center, the target lateral position is set at the lane center,
The vehicle travel control device , wherein when the position of the obstacle is within a predetermined range from the host vehicle, the front arrival point is corrected to a more forward position. In the vehicle travel control device according to claim 2 or 3 ,
The steering state detecting means detects the steering speed of the driver,
The vehicle lane tracking control means corrects the front arrival point to a more forward position for a predetermined time when the magnitude of the steering speed exceeds a predetermined threshold value .

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