Vehicle lane keeping control system

Abstract

To provide a lane keeping control device for a vehicle that is able to restart lane keeping control at an early stage without a driver's intervention after a slip of the vehicle is detected and the lane keeping control is automatically cancelled.SOLUTION: A lane keeping control device 1 for a vehicle switches from a lane keeping mode to a slip handling mode when a slip of an own vehicle M is detected; and restarts the lane keeping mode after performing steering control so that the own vehicle M takes a stable posture.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a lane keep control device for a vehicle that controls an electric power steering and causes the vehicle to travel along a set target path.

Background Art

[0002] In recent years, when a vehicle is running, a lane keep control technology for a vehicle is known as a driving support that recognizes a road lane line with a camera, controls the steering of the vehicle, and maintains the center of the lane and suppresses lane departure. For example, Patent Document 1 discloses a technology of a lane keep control system that can accurately detect the road surface condition or road surface μ of the running road surface of a vehicle and perform more accurate lane keep control according to the detection result.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when a vehicle slips (skids) while running on a road with a low μ road surface such as a snowy road or an ice burn, a lane keep control device for a vehicle such as a conventional lane keep control system causes the vehicle to deviate from the normal route of lane keep and enter an incorrect steering state. Therefore, when the vehicle falls into a slip state, the conventional lane keep control device automatically cancels the lane keep control when it detects that it is outside the operating design domain (ODD) range and performs control to transfer to the driver.

[0005] However, with conventional lane-keeping control systems, once lane-keeping control is canceled, it cannot be restarted until the vehicle reaches a stable driving state. Therefore, if the vehicle slips due to a slip or other reason and the system automatically cancels lane-keeping control, the driver must intervene to restart lane-keeping.

[0006] Therefore, in view of the above circumstances, the present invention aims to provide a vehicle lane keeping control device that can detect vehicle slippage, automatically cancel lane keeping control, and then quickly resume lane keeping control without driver intervention. [Means for solving the problem]

[0007] A vehicle lane keeping control device according to one aspect of the present invention sets a target path that the vehicle should travel, calculates a control amount for the electric power steering motor based on at least the amount of deviation from the target path, and controls the vehicle to travel along the target path, The steering control unit is When the vehicle's sideways slip is detected, the system switches from lane-keeping mode to slip-response mode. If the skid is nearing its end, the system detects the longitudinal attitude of the vehicle relative to the lane, and performs steering control based on a target steering angle for the vehicle to return to the target path. If the longitudinal attitude of the vehicle relative to the lane falls below a threshold that allows the vehicle to correct its direction to the target path without slipping, the system detects the lateral position of the vehicle relative to the lane width, and performs steering control to correct the lateral position of the vehicle relative to the lane width based on the amount of positional deviation between the vehicle trajectory estimated using a second forward gaze point that is further forward than the first forward gaze point in the vehicle's longitudinal direction used in the lane-keeping mode and the target path. If the lateral position of the vehicle relative to the lane width falls within a predetermined threshold, the system terminates the slip-response mode. The lane-keeping mode is then restarted. Furthermore, a vehicle lane keeping control device according to one aspect of the present invention sets a target path that the vehicle should travel, calculates a control amount for the electric power steering motor based on at least the amount of deviation from the target path, and controls the vehicle to travel along the target path, comprising: a motor drive unit that drives the electric power steering motor; a yaw rate sensor that detects the yaw rate acting on the vehicle; a steering angle sensor that detects the steering angle of the steering wheel; a wheel speed sensor that detects the rotational speed of each wheel of the vehicle (front, rear, left, and right); an acceleration sensor that detects the acceleration of the vehicle (front, rear, left, and right); and the corner of the vehicle The system includes a gyro sensor that detects speed or angular acceleration, a forward recognition device that recognizes the left and right lane markings in front of the vehicle to recognize the shape of the road, and a steering control device that receives various vehicle information from the yaw rate sensor, steering angle sensor, wheel speed sensor, acceleration sensor, gyro sensor, and forward recognition device, and controls the motor drive unit based on the various vehicle information. When the steering control device detects a sideways slip of the vehicle from the various vehicle information, it switches from lane keeping mode to slip response mode, executes the slip response mode, performs steering control to bring the vehicle into a stable position, and then resumes lane keeping mode. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a vehicle lane keeping control device that can detect vehicle slippage, automatically cancel lane keeping control, and then quickly resume lane keeping control without driver intervention. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram showing the configuration of the vehicle's lane-keeping control system, which is part of the vehicle's steering system. [Figure 2] Front view showing the vehicle equipped with a forward recognition system. [Figure 3] Functional block diagram of the steering control unit. [Figure 4] An explanatory diagram showing an example of the characteristics of steering torque and basic current value of an electric power steering motor. [Figure 5] Diagram illustrating feedforward control [Figure 6] Diagram illustrating lateral position feedback control [Figure 7] Diagram illustrating yaw angle feedback control [Figure 8] Flowchart showing an example of control in slip-response mode. [Figure 9] A diagram showing a vehicle slipping while traveling in the driving lane on a straight road. [Figure 10] This diagram shows the state in which a vehicle that has slipped corrects its attitude relative to the driving lane through steering control in slip-response mode. [Figure 11] This diagram shows a state where steering control is performed based on the difference in position between the vehicle trajectory estimated using the forward gaze point and the target path. [Modes for carrying out the invention]

[0010] An embodiment of one aspect of the present invention will be described in detail below with reference to the drawings. In the drawings used in the following description, the scale of each component is different in order to make each component recognizable on the drawing, and the present invention is not limited to the number of components, the shape of the components, the ratio of the sizes of the components, and the relative positional relationship of each component as shown in these drawings.

[0011] As shown in Figure 1, the vehicle's lane-keeping control device 1 is equipped with an electric power steering device 2. The electric power steering device 2 is configured to allow the steering angle to be set independently of the driver input.

[0012] The lane-keeping control device 1 has a steering shaft 3 that is rotatably supported on a vehicle frame (not shown) via a steering column 4a. One end of the steering shaft 3 extends toward the driver's seat, and the other end extends toward the engine compartment (not shown).

[0013] A steering wheel 4 is disposed at the driver's seat side end of the steering shaft 3. A pinion shaft 5 is disposed at the end of the steering shaft 3 extending toward the engine room side.

[0014] In an engine room (not shown), a steering gear box 6 is disposed which extends in the vehicle width direction. A rack shaft support mechanism 13 is provided in the steering gear box 6. In the rack shaft support mechanism 13, a rack shaft 7 is inserted and supported in the steering gear box 6 so as to be reciprocally movable.

[0015] Also, both the left and right ends of the rack shaft 7 project from the ends of the steering gear box 6 respectively. At the ends of the rack shaft 7, front knuckles 9 are connected via tie rods 8.

[0016] The front knuckles 9 support the left and right wheels 10L, 10R as steering wheels so as to be rotatable. The front knuckles 9 are supported by the vehicle body frame so as to be steerable.

[0017] When the steering wheel 4 is operated, the steering shaft 3 and the pinion shaft 5 are rotated. By the rotation of the pinion shaft 5, the rack shaft 7 moves in the left - right direction. By the movement of the rack shaft 7, the front knuckle 9 rotates about a kingpin shaft (not shown). Thereby, the left and right wheels 10L, 10R are steered in the left - right direction.

[0018] An assist transmission mechanism 11 is provided on the pinion shaft 5. The assist transmission mechanism 11 is connected to an electric power steering motor (electric motor) 12.

[0019] The electric motor 12 performs assist of the steering torque applied to the steering wheel 4 and addition of a steering torque such that a set steering angle (target steering angle) is obtained. The electric motor 12 is driven by a motor drive unit 21. At this time, a target current as an output value for driving and controlling the electric motor 12 from a steering control unit 20 is output to the motor drive unit 21.

[0020] A forward recognition device 30 is connected to the steering control unit 20. The forward recognition device 30 recognizes the shape of the road ahead, including the left and right lane markings (white lines, etc.), and acquires lane marking position information.

[0021] The forward recognition device 30 consists of a pair of cameras 31 and 32 and a stereo image processing device (not shown). The pair of cameras 31 and 32 have image sensors such as CCD and CMOS. These cameras 31 and 32 are mounted, for example, at a certain distance apart in the front near the ceiling inside the vehicle (see Figure 2).

[0022] These two cameras 31 and 32 capture stereo images of objects outside the vehicle from different viewpoints. A stereo image processing device (not shown) then processes the two image data from the pair of cameras 31 and 32. The stereo image processing device calculates distance information from the corresponding positional displacement for the stereo image pair captured in the direction of travel of the vehicle M. The stereo image processing device then generates a distance image.

[0023] The steering control unit 20 receives various vehicle information from sensors such as the yaw rate sensor 22, steering angle sensor 23, wheel speed sensor 24, steering torque sensor 25, acceleration sensor 26, and gyro sensor 27.

[0024] The yaw rate sensor 22 detects the yaw rate acting on the vehicle M. The steering angle sensor 23 detects the steering angle of the steering wheel 4. The wheel speed sensor 24 detects the rotational speed of each wheel of the vehicle M (front, rear, left, and right) and detects the driving speed (vehicle speed V). The steering torque sensor 25 detects the operating force of the steering wheel 4. The acceleration sensor 26 detects the acceleration of the vehicle M in the front, rear, left, and right directions. The gyro sensor 27 detects the angular velocity or angular acceleration of the vehicle M.

[0025] As shown in Figure 3, the steering control unit 20 mainly consists of a motor basic current setting unit 20a, a feedforward control unit 20b, a lateral position feedback control unit 20c, a yaw angle feedback control unit 20d, a lateral position feedback gain setting unit 20e, a yaw angle feedback gain setting unit 20f, and an electric power steering motor current value calculation unit 20g.

[0026] The lane keeping control device 1, in recognizing lane marking data, evaluates the change in brightness in the width direction of the road based on the knowledge that the lane markings are brighter than the road surface.

[0027] The lane-keeping control device 1 then identifies the positions of the left and right lane markings on the image plane. The real-space position (x,y,z) of these lane markings is calculated using a well-known coordinate transformation formula based on the position (i,j) on the image plane and the disparity calculated with respect to this position, that is, based on distance information.

[0028] The real-world coordinate system, set based on the position of the vehicle M, is, for example, based on the road surface directly below the center of the pair of stereo cameras 31 and 32 as the origin, with the vehicle width direction as the x-axis, the vehicle height direction as the y-axis, and the vehicle length direction (distance direction) as the z-axis (see Figure 5).

[0029] In this case, the xz plane (y=0) coincides with the road surface if the road is flat. The road model is represented by dividing the lane of the vehicle M on the road into multiple sections in the distance direction, and approximating and connecting the left and right lane lines in each section to a predetermined value.

[0030] The steering control unit 20 sets the motor base current Ipsb according to the driver's steering torque Td based on each input signal.

[0031] The steering control unit 20 calculates the feedforward control amount Iff of the electric motor 12 required to travel along the target path (in this embodiment, midway between the left lane markings and the right lane markings) by feedforward control based on the shape of the travel path.

[0032] The steering control unit 20 estimates the vehicle trajectory of its own vehicle M and calculates the amount of positional deviation Δx between the estimated vehicle trajectory and the target path at a pre-set forward gaze point.

[0033] The steering control unit 20 calculates a lateral position feedback control amount Ifb that controls the vehicle to eliminate the deviation amount Δx and travel along the target path.

[0034] The steering control unit 20 calculates a yaw angle feedback control amount Ifby to adjust the yaw angle of the vehicle M to a yaw angle that aligns with the target path.

[0035] The steering control unit 20 sets the lateral feedback gain of the lateral feedback control amount Ifb to be larger when the road width Wr is wider than when the road width Wr is narrower, with respect to each control amount of the feedback control.

[0036] On the other hand, the steering control unit 20 sets the yaw angle feedback gain of the yaw angle feedback control amount Ifby to be larger when the road width Wr is narrow than when the road width Wr is wide.

[0037] The steering control unit 20 calculates the electric motor current value Icmd by adding the above values. Based on this, the steering control unit 20 outputs the electric motor current value Icmd to the motor drive unit 21 to drive and control the electric motor 12.

[0038] The motor basic current setting unit 20a receives the vehicle speed V from the wheel speed sensor 24. The motor basic current setting unit 20a also receives the steering torque Td from the steering torque sensor 25.

[0039] The motor basic current setting unit 20a sets the electric motor basic current value Ipsb by referring to a pre-set characteristic map of steering torque Td-electric motor basic current value Ipsb, as shown in Figure 4.

[0040] The motor basic current setting unit 20a then outputs the electric motor basic current value Ipsb to the electric power steering motor current value calculation unit 20g.

[0041] The feedforward control unit 20b receives image information recognized from the forward recognition device 30. Then, for example, it calculates the feedforward control amount (current value) Iff of the electric motor 12 required to travel along the target path using equation (1) below, and outputs it to the electric power steering motor current value calculation unit 20g.

[0042] Iff = Giff·κ …(1)

[0043] Here, κ represents the lane curvature, for example, as shown in equation (2) below.

[0044] κ = (κl + κr) / 2 …(2)

[0045] In equation (2), κl is the curvature component due to the left dividing line, and κr is the curvature component due to the right dividing line.

[0046] These curvature components κl and κr of the left and right dividing lines are specifically determined by using the coefficients of quadratic terms calculated by the quadratic least squares method for each point constituting the left and right dividing lines, as shown in Figure 5.

[0047] For example, when approximating the boundary lines with a quadratic equation of x = A·z² + B·z + C, the value of 2·A is used as the curvature component. Note that the curvature components κl and κr of these boundary lines can also be the curvature of the respective boundary lines themselves.

[0048] Furthermore, Giff in equation (1) represents the feedforward gain that has been set in advance through experiments, calculations, etc. Thus, the feedforward control unit 20b is provided as a feedforward control means.

[0049] The lateral position feedback control unit 20c receives image information recognized from the forward recognition device 30. The lateral position feedback control unit 20c also receives vehicle speed V from the wheel speed sensor 24. Furthermore, the lateral position feedback control unit 20c receives steering angle θp from the steering angle sensor 23.

[0050] Then, the lateral position feedback control amount (current value) Ifb is calculated using equation (3) below. This lateral position feedback control amount Ifb is output to the electric power steering motor current value calculation unit 20g.

[0051] Ifb = Gifb · Δx …(3)

[0052] Here, Gifb is the gain that has been set in advance through experiments or calculations. Also, Δx is calculated by equation (4) below, as shown in Figure 6.

[0053] Δx=(xl+xr) / 2-xv …(4)

[0054] In equation (4), xv is the x-coordinate of the estimated vehicle trajectory at the z-coordinate of the forward gaze point (0, zv) of the vehicle M, and zv, which is the forward gaze distance (z-coordinate) of the forward gaze point (0, zv), is calculated in this embodiment as zv = T·V. Here, T is a predetermined forecast time, which is set to, for example, 1.2 seconds.

[0055] Therefore, xv can be calculated based on the driving conditions of the vehicle M, using the vehicle's specifications, the vehicle's inherent stability factor As, etc., for example, by equation (5) below. xv=(1 / 2)·(1 / (1+As·V2))·(θp / Lw)·(T·V)2 …(5)

[0056] Here, Lw is the wheelbase. Also, in equation (4), xl is the x-coordinate of the left lane line at the z-coordinate of the forward gaze point (0, zv), and xr is the x-coordinate of the right lane line at the z-coordinate of the forward gaze point (0, zv).

[0057] Furthermore, the above-mentioned xv can also be calculated using the vehicle speed V and yaw rate (dθ / dt) in the following equation (6). Alternatively, it can be calculated based on image information using the following equation (7). xv=(1 / 2)·((dθ / dt) / V)·(V·T)2 …(6) xv = (1 / 2)·κ·(V·T)² …(7)

[0058] Thus, the lateral position feedback control unit 20c is provided as a lateral position feedback control means. The yaw angle feedback control unit 20d receives image information recognized from the forward recognition device 30.

[0059] Then, for example, the following equation (8) is used to calculate the yaw angle feedback control amount (current value) Ifby, which is used to feedback control the yaw angle of the vehicle M to a yaw angle along the target path. The yaw angle feedback control amount (current value) Ifby is then output to the electric power steering motor current value calculation unit 20g.

[0060] Ifby=Gifby·(θtl+θtr) / 2 …(8)

[0061] Here, Gifby is a gain that has been set in advance through experiments and calculations. θtl is the inclination of the vehicle M relative to the left lane marking based on image information from the forward recognition device 30. θtr is the inclination of the vehicle M relative to the right lane marking based on image information from the forward recognition device 30 (see Figure 7). The lane-to-lane yaw angle Ψ is calculated using the formula Ψ = (θtl + θtr) / 2.

[0062] These θtl and θtr can, for example, be the coefficients of the linear term calculated by the quadratic least squares method for each point of the dividing line obtained from the image information (i.e., the value of B when the dividing line is approximated by the equation x = A·z² + B·z + C).

[0063] Thus, the yaw angle feedback control unit 20d is provided as a yaw angle feedback control means. The yaw angle of the vehicle M may also be detected by the change in yaw angle input from the yaw rate sensor 22.

[0064] The lateral position feedback gain setting unit 20e receives image information recognized from the forward recognition device 30. Based on the image information, it calculates the road width Wr from, for example, the distance between the left lane line and the right lane line, and compares the road width Wr with a pre-set reference width C.

[0065] As a result of this comparison, if the road width Wr is wider than the reference width C (Wr > C), and it can be determined that the road is wide, such as a highway, then a high value of lateral feedback gain Gfb1 is set as the lateral feedback gain Gfb that is multiplied by the lateral feedback control amount Ifb.

[0066] Conversely, if the road width Wr is less than or equal to the reference width C (Wr ≤ C), and it can be determined that the road is a narrow road such as a general road, then a small value of the lateral feedback gain Gfb2 is set as the lateral feedback gain Gfb that is multiplied by the lateral feedback control amount Ifb.

[0067] That is, Gfb1 > Gfb2, and when the road width Wr is wide, the influence of the lateral position feedback control amount Ifb is set to be stronger than when the road width Wr is narrow. The lateral position feedback gain Gfb thus set is output to the electric power steering motor current value calculation unit 20g. In this way, the lateral position feedback gain setting unit 20e is provided as a lateral position feedback gain setting means.

[0068] The yaw angle feedback gain setting unit 20f receives image information recognized from the forward recognition device 30. Based on the image information, it calculates the road width Wr from, for example, the distance between the left lane markings and the right lane markings, and compares the road width Wr with a pre-set reference width C.

[0069] As a result of this comparison, when it can be determined that the running lane width Wr is wider than the reference width C (Wr > C), such as on a highway, a small yaw angle feedback gain Gfby1 is set as the yaw angle feedback gain Gfby to be multiplied by the yaw angle feedback control amount Ifby.

[0070] Conversely, when it can be determined that the running lane width Wr is less than or equal to the reference width C (Wr ≤ C), such as on a general road, a large yaw angle feedback gain Gfby2 is set as the yaw angle feedback gain Gfby to be multiplied by the yaw angle feedback control amount Ifby.

[0071] That is, Gfby1 < Gfby2, and when the running lane width Wr is narrow, the degree of influence of the yaw angle feedback control amount Ifby is set stronger than when the running lane width Wr is wide. The yaw angle feedback gain Gfby thus set is output to the electric power steering motor current value calculation unit 20g. In this way, the yaw angle feedback gain setting unit 20f is provided as yaw angle feedback gain setting means.

[0072] The electric power steering motor current value calculation unit 20g receives the electric motor basic current value Ipsb from the motor basic current setting unit 20a. The electric power steering motor current value calculation unit 20g receives the feedforward control amount Iff from the feedforward control unit 20b.

[0073] The electric power steering motor current value calculation unit 20g receives the lateral position feedback control amount Ifb from the lateral position feedback control unit 20c. The electric power steering motor current value calculation unit 20g receives the yaw angle feedback control amount Ifby from the yaw angle feedback control unit 20d.

[0074] The electric power steering motor current value calculation unit 20g receives the lateral position feedback gain Gfb from the lateral position feedback gain setting unit 20e. The electric power steering motor current value calculation unit 20g also receives the yaw angle feedback gain Gfby from the yaw angle feedback gain setting unit 20f.

[0075] Then, for example, the electric motor current value Icmd is calculated using equation (9) below and output to the motor drive unit 21 to drive and control the electric motor 12.

[0076] Icmd=Ipsb+Iff+Gfb·Ifb+Gfby·Ifby …(9)

[0077] As described above, the steering control unit 20 of the lane keeping control device 1 performs lane keeping control of the vehicle M.

[0078] Specifically, the steering control unit 20 detects information about the lane in which the vehicle M is traveling (position and curvature of the left and right lane markings, etc.) and information about the position of the vehicle M relative to the lane (distance to the left and right lane markings, road width, lane-to-lane yaw angle of the vehicle's attitude angle relative to the lane, etc.) from the left and right lane marking information detected by the forward recognition device 30, as lane information.

[0079] Based on this lane information, the vehicle M performs lane-keeping control, such as lane centering control and lane departure prevention control. Since the lane-keeping control examples of the steering control unit 20 are well known, details of those control examples will be omitted.

[0080] In this embodiment, if the vehicle M slips (skids sideways) during lane keeping control, the steering control unit 20 executes the control example shown in the flowchart of Figure 8.

[0081] The steering control unit 20 of the lane keeping control device 1 detects whether the vehicle M is slipping (skidding) (S1). At this time, the steering control unit 20 determines whether the vehicle M is slipping relative to the target path based on the yaw rate input from the yaw rate sensor 22, the steering angle θp input from the steering angle sensor 23, the vehicle speed V input from the wheel speed sensor 24, the acceleration in the longitudinal, lateral, and forward directions input from the acceleration sensor 26, and the yaw rate input from the gyro sensor 27.

[0082] Specifically, the steering control unit 20 determines that the vehicle M is slipping when the lane-to-lane yaw angle Ψ{=(θtl+θtr) / 2} becomes greater than a predetermined threshold (first threshold) T1, for example, as shown in Figure 9. In Figure 9, an example of a slipping state is shown when the vehicle M is traveling in the lane of a straight road.

[0083] Furthermore, the steering control unit 20 may determine that the vehicle M is slipping if, for example, the value calculated from the steering angle θp input from the steering angle sensor 23 and the wheel speed (vehicle speed V) input from the wheel speed sensor 24 differs significantly from the values ​​of the acceleration input from the acceleration sensor 26 and the angular acceleration input from the gyro sensor 27.

[0084] Furthermore, the steering control unit 20 may determine that the vehicle M is slipping if, for example, the value of the yaw rate input from the yaw rate sensor 22 differs significantly from the value calculated from the steering angle θp and the wheel speed (vehicle speed V).

[0085] Furthermore, the steering control unit 20 may determine, for example, that the vehicle M is slipping if, based on the image information recognized by the forward recognition device 30, neither the left nor the right lane marking is detected, and the vehicle M is moving toward the detected lane marking in its direction of travel.

[0086] The steering control unit 20 then repeatedly detects slippage of the vehicle M during lane keeping control. When the steering control unit 20 detects slippage of the vehicle M, it terminates (turns off) the lane keeping control (S2).

[0087] Next, slip-response control is started (ON) (S3). That is, the steering control unit 20 switches from lane-keeping control in lane-keeping mode to slip-response control in slip-response mode and executes the control.

[0088] In slip-responsive control, the steering control unit 20 detects the slip state of the vehicle M (S4). At this time, the steering control unit 20 detects the slip state from the behavior of the vehicle M in the direction of travel with respect to the vehicle speed V and steering angle θp. At this time, the steering control unit 20 detects the slip state of the vehicle M from values ​​such as the lane-to-lane yaw angle Ψ, steering angle θp, wheel speed (vehicle speed V), longitudinal acceleration, angular acceleration, and yaw rate.

[0089] The steering control unit 20 then determines whether the vehicle M's slip is nearing its end (S5). The steering control unit 20 detects that the vehicle M's slip is nearing its end by, for example, a decrease in the lane-to-lane yaw angle Ψ, or a decrease in the difference between values ​​such as acceleration, angular acceleration, and yaw rate calculated from the vehicle speed V and steering angle θp.

[0090] If the vehicle M's slip is not nearing its end, the steering control unit 20 returns to step S4 for detecting the vehicle M's slip state and repeatedly executes the determination routine in step S5.

[0091] The steering control unit 20 detects the direction of travel of the vehicle M when the vehicle M's slip is about to end (S6). The steering control unit 20 detects the direction of the z-axis, which is the vehicle length direction of the vehicle M relative to the driving lane, for example, determined from the left and right lane markings. That is, the steering control unit 20 detects the forward and backward attitude of the vehicle M, which is the direction of travel of the vehicle M relative to the driving lane.

[0092] Then, the steering control unit 20 performs steering control so that the yaw angle of the vehicle M returns to the target path (S7). The steering control unit 20 drives the motor drive unit 21 to assist the steering torque applied to the steering wheel 4 by the electric motor 12. In other words, the steering control unit 20 controls the vehicle M so that the steering angle (target steering angle) θp returns to the direction of the target path.

[0093] Subsequently, the steering control unit 20 determines whether the lane-to-lane yaw angle Ψ is less than or equal to a predetermined threshold (second threshold) T2 (S8). Note that the predetermined threshold T2 is a smaller value than the predetermined threshold (first threshold) T1. The steering control unit 20 corrects (turns) the longitudinal attitude of the vehicle M relative to the lane by steering, for example, as shown in Figure 10.

[0094] The steering control unit 20 then repeatedly executes the determination routine in step S8 until the lane-to-lane yaw angle Ψ becomes less than or equal to a predetermined threshold T2. The predetermined threshold T2 is set to the lane-to-lane yaw angle Ψ that allows the vehicle M to correct its direction within a range that allows it to change its attitude without slipping relative to the target path of the driving lane. Step S8 may also be a routine that determines, for example, whether both the left and right lane markings have been detected from the image information recognized by the forward recognition device 30.

[0095] The steering control unit 20 detects the lateral position of the vehicle M relative to the road width Wr when the yaw angle Ψ of the vehicle M relative to the lane falls below a predetermined threshold T2 (S9). The steering control unit 20 detects the lateral position of the vehicle M relative to the road width Wr, which is determined from the distance between the left lane markings and the right lane markings, using image information recognized from the forward recognition device 30.

[0096] Then, the steering control unit 20 performs steering control to correct the lateral position of the vehicle M with respect to the road width Wr (S10). At this time, as shown in Figure 11, the steering control unit 20 performs steering control based on the amount of positional deviation Δx1 between the vehicle trajectory estimated using a second forward gaze point P2 on the z-axis, which is at a longer distance toward the direction of travel than the first forward gaze point P1 on the z-axis, which is the vehicle length direction of the vehicle M during lane keeping control, and the target path.

[0097] In other words, the steering control unit 20 performs steering control to gently return the lateral position of its own vehicle M toward the target path because the amount of deviation Δx1 here is smaller than the amount of deviation Δx0 between the vehicle trajectory estimated using the first forward gaze point P1 during lane keeping control and the target path.

[0098] The steering control unit 20 then determines whether the lateral position of the vehicle M with respect to the road width Wr is within a predetermined threshold (S11). The threshold here (the third threshold) is set to the lateral position of the vehicle M that does not result in a sharp steering angle even when lane keeping control of the vehicle M is resumed. Based on the image information recognized from the forward recognition device 30, the steering control unit 20 repeatedly executes the determination routine in step S5 until the lateral position of the vehicle M is within the predetermined threshold.

[0099] The steering control unit 20 terminates (turns off) the slip-response control (S12) when the lateral position of the vehicle M falls within a predetermined threshold. Then, the steering control unit 20 starts (turns on) the lane-keeping control and terminates this control. In other words, the steering control unit 20 switches from the slip-response control mode to the lane-keeping control mode.

[0100] As described above, if the lane keeping control device 1 of this embodiment detects a slip (sideways skid) of the vehicle M while lane keeping is being performed, it temporarily cancels the lane keeping control, switches to a slip-response mode (control), restores the vehicle M to a stable position, and then performs lane keeping control again.

[0101] Furthermore, while the vehicle's lane-keeping control device 1 is executing the slip-response mode, it gradually returns the vehicle M to the target path in the center of the lane to prevent it from going outside the lane, and returns the vehicle M to a stable driving posture, thereby restarting lane-keeping control as soon as possible.

[0102] In the embodiment described above, the shape of the road surface was explained as being recognized based on images from a pair of cameras 31 and 32, but it may also be determined based on image information from a monocular camera, a color camera, etc. Furthermore, the steering control may be performed based on the detected value of the vehicle's position by a GPS mounted on the vehicle.

[0103] The steering control unit 20 of the lane-keeping control device 1 has a processor that includes a central processing unit (CPU), memory devices such as ROM and RAM. Furthermore, all or some of the configurations of the processor's multiple circuits may be executed by software. For example, the CPU may read and execute various programs corresponding to each function stored in the ROM.

[0104] Furthermore, all or part of the processor's functions may be comprised of logic circuits or analog circuits, and the processing of various programs may be implemented using electronic circuits such as FPGAs.

[0105] The inventions described in the above embodiments are not limited to those forms, and various modifications can be made in the implementation stage without departing from the gist of the invention. Furthermore, each of the above embodiments includes inventions at various stages, and various inventions can be extracted by appropriate combinations of the multiple constituent elements disclosed.

[0106] For example, if the problem described can be solved and the effects described can be obtained even if some of the constituent elements shown in each form are removed, then the configuration with the removed constituent elements can be extracted as an invention. [Explanation of Symbols]

[0107] 1... Lane keeping control device 2…Electric power steering system 3… Steering axis 4… Steering wheel 4a... Steering column 5...Pinion shaft 6… Steering gearbox 7... Rack axis 8...Tie rod 9…Front knuckle 10L,10R…Left and right wheels 11... Assist transmission mechanism 12…Electric power steering motor (electric motor) 12… Electric motor 13... Rack axis support mechanism 20... Steering control unit 20a...Motor basic current setting section 20b...Feedforward control unit 20c... Lateral position feedback control unit 20d...Yaw angle feedback control unit 20e...Horizontal position feedback gain setting section 20f...Yaw angle feedback gain setting section 20g...Electric power steering motor current value calculation unit 21…Motor drive unit 22... Yaw rate sensor 23... Steering angle sensor 24...Wheel speed sensor 25... Steering torque sensor 26…Accelerometer 27…Gyro sensor 30…Front recognition device 31, 32… Camera M... My vehicle P1, P2... Forward-looking points T1...First threshold T2...Second threshold Ψ,(θtl+θtr) / 2…Lane-to-lane yaw angle θp… Steering angle V…Vehicle speed Wr... Road width Δx0, Δx1… amount of displacement

Claims

1. In a vehicle lane-keeping control device that sets a target path for the vehicle to travel, calculates a control amount for the electric power steering motor based on at least the amount of deviation from the target path, and controls the vehicle to travel along the target path, The steering control unit is When the vehicle detects a skid, it switches from lane-keeping mode to slip-response mode. If the skid is nearing its end, the longitudinal attitude of the vehicle relative to the lane is detected, and steering control is performed based on the target steering angle for the vehicle to return to the direction of the target path. If the longitudinal attitude of the vehicle, which is the direction of travel relative to the driving lane, falls below a threshold that allows the vehicle to correct its direction to the target path without slipping, the lateral position of the vehicle relative to the width of the driving lane is detected, and steering control is performed to correct the lateral position of the vehicle relative to the width of the driving path based on the amount of positional deviation between the vehicle trajectory estimated using a second forward gaze point that is further on the direction of travel than the first forward gaze point in the vehicle's longitudinal direction used in the lane-keeping mode, and the target path. A vehicle lane keeping control device characterized in that, when the lateral position of the vehicle with respect to the width of the road falls within a predetermined threshold, the slip response mode is terminated and the lane keeping mode is restarted.

2. A vehicle lane keeping control device that sets a target path on which the vehicle should travel, calculates a control amount for an electric power steering motor based on at least the amount of deviation from the target path, and controls the vehicle to travel along the target path, A motor drive unit that drives the aforementioned electric power steering motor, A yaw rate sensor that detects the yaw rate acting on the vehicle, A steering angle sensor that detects the steering angle of the steering wheel, A wheel speed sensor that detects the rotational speed of each wheel (front, rear, left, and right) of the vehicle, An acceleration sensor that detects acceleration in the front, rear, left, and right directions of the vehicle, A gyro sensor that detects the angular velocity or angular acceleration of the vehicle, A forward recognition device that recognizes the left and right lane markings ahead and recognizes the shape of the road, A steering control device receives various vehicle information from the yaw rate sensor, steering angle sensor, wheel speed sensor, acceleration sensor, gyro sensor, and forward recognition device, and controls the motor drive unit based on the various vehicle information. Equipped with, The steering control device is characterized in that, when it detects a skid of the vehicle from the various vehicle information, it switches from lane keeping mode to slip response mode, executes the slip response mode, performs steering control to bring the vehicle into a stable position, and then restarts the lane keeping mode.

3. The lane-keeping control device for a vehicle according to claim 2, characterized in that the steering control device determines the side slip of the vehicle when the yaw angle of the vehicle relative to the lane becomes greater than a first threshold.

4. The lane-keeping control device for a vehicle according to claim 3, characterized in that the steering control device performs steering control so that the vehicle maintains a stable posture until the yaw angle of the vehicle relative to the lane becomes less than or equal to a second threshold which is smaller than the first threshold.

5. The steering control device is characterized in that it performs steering control using a second forward gaze point that is at a longer distance on the side of the vehicle's movement than the first forward gaze point in the lane-keeping mode.

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