JP2015189410A - Lane deviation prevention controller for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unnecessary variation of steering force, caused by hunting, etc. in lane deviation control without excessive operation of steering, and to reliably suppress deterioration of a feeling of steering.SOLUTION: Based on a lane-width-direction lateral position xv, a yaw angle θyaw, and a vehicle speed V, a lane deviation expected time Tttlc is calculated, and a target yaw rate γt is calculated. A target yaw moment Mzt is calculated based on the target yaw rate γt and an actual yaw rate γ, and a target torque Tp is calculated depending on the target yaw moment Mzt. The target torque Tp compensates for a friction torque in a steering system by adding a friction compensating torque Tfric in a direction in which the actual yaw rate γ approaches the target yaw rate γt. However, when a vehicle is directed in a direction deviated from a lane, only in the case of γ≤γt, the friction compensating torque Tfric is added, and in the case of γ>γt, the friction compensating torque Tfric is set to 0.

Description

  The present invention relates to a lane departure prevention control device for a vehicle that performs control to prevent departure from a lane by applying a yaw moment to the vehicle by operating an actuator when the vehicle is likely to deviate from a traveling lane. .

  In recent years, various devices that support driving have been developed and put into practical use in vehicles, and a lane departure prevention control device that prevents departure from a lane is one of such devices. For example, in Japanese Patent Laid-Open No. 7-105498 (hereinafter referred to as Patent Document 1), the distance to the intersection between the estimated traveling path of the host vehicle and the side edge of the lane, and the angle formed between the estimated traveling path and the side edge at the intersection Based on the above, there is disclosed a technology of a vehicle traveling state determination device that predicts a departure state from a lane and performs automatic correction steering to prevent the departure based on the prediction.

JP 7-105498 A

  By the way, the value of the friction torque in the steering system of the vehicle is affected by temperature, secular change (wear, etc.), variation between solids, and the like, and it is difficult to estimate the true value of the friction torque with high accuracy sequentially. When compensating for steering control by estimating the friction torque of such a steering system and compensating the steering control, if the estimated value of the friction torque of the steering system is less than the true value, a steering delay occurs, resulting in a lane departure. There is a risk that it cannot be prevented. On the contrary, when the estimated value of the friction torque of the steering system is larger than the true value, the steering is overcut. In lane departure prevention control employing such steering control, hunting of the steering torque for departure prevention occurs due to the steering compensation error as described above, especially when the compensation is excessively greater than the true value, and the driver's steering feeling deteriorates. There is a risk of it. In other words, if the steering compensation is immediately performed in the switchback direction when the actual turning amount exceeds the target turning amount while preventing departure from the lane, the driver feels that the rudder is missing in the departure direction, and again When the actual turning amount falls below the target turning amount, a torque is applied again in the departure prevention direction, causing a change in steering force, which gives the driver an uncomfortable feeling. Furthermore, by outputting a constant torque without considering the difference between the target turning amount and the actual turning amount, unnecessary steering force fluctuations can be suppressed, but the actual turning amount exceeds the target turning amount. In some cases, the actual turning amount may greatly exceed the target turning amount due to excessive steering.

  The present invention has been made in view of the above circumstances, and it is possible to reliably prevent deterioration in steering feeling by preventing unnecessary fluctuations in steering force such as hunting in lane departure control without causing excessive steering. An object of the present invention is to provide a lane departure prevention control device for a vehicle.

  According to one aspect of the vehicle lane departure prevention control apparatus of the present invention, lane detection means for detecting a lane in which the vehicle is traveling, and prediction of departure from the lane based on vehicle position information and a traveling state in the lane are performed. Deviation prediction means, target turn amount calculation means for calculating a target turn amount to be added to the vehicle necessary to prevent a departure from the lane based on the departure prediction from the lane, and according to the target turn amount A steering means that operates by inputting a control amount, and a correction amount of the control amount is set in advance based on a change in the actual turning amount caused by the operation of the steering means, and the target turning amount and the actual turning amount Control amount correction means for correcting the control amount by adding the correction amount to the control amount, and control for changing the correction by the control correction means depending on whether the vehicle is in the lane departure direction or not correction And a further means.

  According to the vehicle lane departure prevention control device according to the present invention, it is possible to prevent unnecessary fluctuations in steering force such as hunting in the lane departure control without causing excessive steering, and to reliably suppress deterioration in steering feeling. Is possible.

1 is a configuration explanatory diagram of a vehicle steering system according to an embodiment of the present invention. FIG. It is a flowchart of the lane departure prevention control program which concerns on one Embodiment of this invention. 5 is a flowchart of a steering system friction compensation processing routine according to an embodiment of the present invention. It is explanatory drawing of the own vehicle on the XZ coordinate which concerns on one Embodiment of this invention, a lane, and each parameter. FIG. 5A is a time chart showing an example of friction compensation torque set by control according to an embodiment of the present invention, FIG. 5A shows a yaw angle signal in a departure direction, and FIG. The target yaw rate is shown, and FIG. 5C shows the friction compensation torque that is set.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes an electric power steering device as a steering means whose steering angle can be set independently of a driver input. In the electric power steering device 1, a steering shaft 2 is attached to a vehicle body frame (not shown) on a steering column. 3, one end of which is extended to the driver's seat side, and the other end is extended to the engine room side. A steering wheel 4 is fixed to an end portion of the steering shaft 2 on the driver's seat side, and a pinion shaft 5 is connected to an end portion extending to the engine room side.

  A steering gear box 6 extending in the vehicle width direction is disposed in the engine room, and a rack shaft 7 is inserted into and supported by the steering gear box 6 so as to be reciprocally movable. A rack (not shown) formed on the rack shaft 7 is engaged with a pinion formed on the pinion shaft 5 to form a rack and pinion type steering gear mechanism.

  The left and right ends of the rack shaft 7 protrude from the end of the steering gear box 6, and a front knuckle 9 is connected to the end via a tie rod 8. The front knuckle 9 rotatably supports left and right wheels 10L and 10R as steering wheels and is supported by a vehicle body frame so as to be steerable. Accordingly, when the steering wheel 4 is operated and the steering shaft 2 and the pinion shaft 5 are rotated, the rack shaft 7 is moved in the left-right direction by the rotation of the pinion shaft 5, and the front knuckle 9 is moved by the movement to the kingpin shaft (not shown). And the left and right wheels 10L, 10R are steered in the left-right direction.

  Further, an electric power steering motor (electric motor) 12 is connected to the pinion shaft 5 via an assist transmission mechanism 11, and assists and sets the steering torque applied to the steering wheel 4 by the electric motor 12. The steering torque is added so that the target turning amount (for example, the target yaw rate) is reached. The electric motor 12 is driven by the motor drive unit 21 by outputting a target torque Tp as a control output value from a steering control unit 20 described later to the motor drive unit 21.

  The steering control unit 20 has an electric power steering control function that assists the driver's steering force, a lane keep control function that causes the vehicle to travel along the target traveling path, and a lane that prevents deviation from the lane line (left and right white lines) of the lane. In this embodiment, the configuration of the lane departure prevention control function will be described.

  The steering control unit 20 is connected to a forward recognition device 31 as a lane detection unit that detects a lane line (left and right white lines) and acquires lane information from the lane line and vehicle attitude angle / position information with respect to the lane. A vehicle speed sensor 32 that detects the vehicle speed V, a steering angle sensor 33 that detects the steering angle (actual steering angle) θp, a yaw rate sensor 34 that detects the yaw rate γ, and a cant angle detection sensor 35 that detects the cant angle θca of the lane are connected. Has been.

  The front recognition device 31 is, for example, a set of CCD cameras that are mounted at a predetermined interval in front of a ceiling in a vehicle interior and that captures an object outside the vehicle from different viewpoints, and a stereo image that processes image data from the CCD camera. And a processing device.

  The processing of image data from the CCD camera in the stereo image processing device of the forward recognition device 31 is performed as follows, for example. First, distance information is obtained from a set of stereo image pairs taken in the traveling direction of the host vehicle captured by the CCD camera from the corresponding positional deviation amount, and a distance image is generated.

  In recognition of white line data, based on the knowledge that the white line is brighter than the road surface, the brightness change in the width direction of the road is evaluated, and the positions of the left and right white lines on the image plane are specified on the image plane. To do. The position (x, y, z) of the white line in the real space is known based on the position (i, j) on the image plane and the parallax calculated with respect to this position, that is, based on the distance information. Calculated from the coordinate conversion formula. In the present embodiment, for example, as shown in FIG. 4, the coordinate system of the real space set based on the position of the host vehicle is the road surface directly below the center of the stereo camera, and the vehicle width direction is the X axis. (Left direction is “+”), vehicle height direction is Y-axis (upward direction is “+”), and vehicle length direction (distance direction) is Z-axis (front direction is “+”). At this time, the XZ plane (Y = 0) coincides with the road surface when the road is flat. The road model is expressed by dividing the lane of the host vehicle on the road into a plurality of sections in the distance direction, and connecting the left and right white lines in each section with a predetermined approximation. In the present embodiment, the example of recognizing the shape of the lane based on images from a pair of CCD cameras has been described. However, the lane shape is obtained based on image information from a monocular camera and a color camera. May be.

Further, the cant angle detection sensor 35 calculates the cant angle θca, for example, by the following equation (1).
θca = sin ⁻¹ ((G′−G) / g) (1)
Here, G is a lateral acceleration value detected by a lateral acceleration sensor (not shown), G ′ is a calculated lateral acceleration value calculated by, for example, the following equation (2), and g is gravitational acceleration.
G ′ = (1 / (1 + As · V ² )) · (V ² / Lw) · θp (2)
Here, As is a vehicle-specific stability factor, and Lw is a wheelbase.

  In addition, the cant angle θca may be obtained from map information or the like of a navigation system (not shown).

  Then, the steering control unit 20 calculates the vehicle position in the width direction of the lane (the vehicle lateral position in the lane width direction) xv based on the above-described lane line position information and each sensor signal, and the yaw angle θyaw of the vehicle with respect to the lane The lane departure predicted time Tttlc deviating from the lane is calculated based on the vehicle lateral position xv in the lane width direction, the yaw angle θyaw, and the vehicle speed V, and from the lane based on the yaw angle θyaw and the estimated lane departure time Tttlc. A target yaw rate γt for preventing deviation is calculated, a target yaw moment Mzt to be added to the vehicle necessary to prevent deviation from the lane is calculated based on the target yaw rate γt and the actual yaw rate γ, and the target yaw moment Mzt The target torque Tp as a control amount to be output to the electric power steering apparatus 1 is calculated according to the above. When the vehicle is in the lane departure direction, the yaw rate γ exceeds the target yaw rate γt. If the yaw rate γ does not exceed the target yaw rate γt, the friction compensation torque Tfric for compensating for the friction torque of the steering system added to the target torque Tp is zero. In addition to adding the compensation torque Tfric, when the vehicle is not in the lane departure direction, the friction compensation torque Tfric is added to compensate for the yaw rate γ approaching the target yaw rate γt, and the friction compensated target torque Tp is motorized. Output to the drive unit 21. The predicted lane departure time Tttlc is also output to the warning control device 40, and the warning control device 40 compares the predicted lane departure time Tttlc with a preset threshold value, so that the predicted lane departure time Tttlc is obtained. When it becomes shorter than the threshold, a lane departure warning is issued to the driver by an audible alarm such as a voice or a chime sound or a visual alarm such as a monitor display. As described above, the steering control unit 20 is configured to have the functions of a departure prediction unit, a target turning amount calculation unit, a control amount correction unit, and a control correction change unit. In the present embodiment, the target yaw rate γt and the target yaw moment Mzt are set as the target turning amount, and the yaw rate γ from the yaw rate sensor 34 is set as the actual turning amount.

Hereinafter, lane departure prevention control executed by the steering control unit 20 will be described based on the flowchart of FIG.
First, in step (hereinafter abbreviated as “S”) 101, the left and right white line approximation processing acquired by the forward recognition device 31 is executed.

The white line on the left side of the host vehicle is approximated by the following equation (3) by the method of least squares.
x = AL · z ² + BL · z + CL (3)
The white line on the right side of the host vehicle is approximated by the following equation (4) by the method of least squares.
x = AR · z ² + BR · z + CR (4)
In the above equations (3) and (4), “AL” and “AR” indicate the curvatures in the respective curves, the curvature κ of the left white line is 2 · AL, and the right white line The curvature κ is 2 · AR. In the equations (3) and (4), “BL” and “BR” indicate the inclination of the respective curves in the width direction of the host vehicle, and “CL” and “CR” indicate the respective curves. The position in the width direction of the vehicle is shown (see FIG. 4).

Next, the process proceeds to S102, and the lane yaw angle θyaw of the host vehicle is calculated by the following equation (5).
θyaw = (BL + BR) / 2 (5)

Next, proceeding to S103, the vehicle lateral position xv in the lane width direction, which is the vehicle position from the center of the lane, is calculated by the following equation (6).
xv = (CL + CR) / 2 (6)

Next, in S104, the lane-to-vehicle distance L is calculated by the following equation (7).
L = ((CL-CR) -TR) / 2-xv (7)
Here, TR is a tread of a vehicle, and in the embodiment of the present invention, the tire position is used as a lane departure criterion.

Next, the process proceeds to S105, and a predicted lane departure time Tttlc that deviates from the lane is calculated by, for example, the following equation (8).
Tttlc = L / (V · sin (θyaw)) (8)

  Then, the process proceeds to S106, where the predicted lane departure time Tttlc is output to the alarm control device 40, and the warning control device 40 compares the predicted lane departure time Tttlc with a preset threshold value to predict the lane departure. When the time Tttlc becomes shorter than the threshold value, a lane departure warning is issued to the driver by an audible alarm such as a voice or a chime sound or a visual alarm such as a monitor display.

Next, the process proceeds to S107, and the target yaw rate γt for preventing the departure from the lane is calculated by the following equation (9).
γt = −θyaw / Tttlc (9)

Next, the process proceeds to S108, and based on the target yaw rate γt calculated in S107 described above, a target yaw moment Mzt to be added to the vehicle necessary to prevent deviation from the lane is calculated by the following equation (10).
Mzt = Kp · (γt−γ) + Ki · ∫ (γt−γ)
+ Kd · d (γt−γ) / dt (10)
Here, Kp is a proportional gain, Ki is an integral gain, and Kd is a differential gain.

  Next, proceeding to S109, a steering system friction compensation torque Tfric, which will be described later with reference to the flowchart of FIG.

Then, the process proceeds to S110, where the target torque Tp is calculated by the following equation (11) and output to the motor drive unit 21.
Tp = K · Mzt + Tfric (11)
Here, K is a preset torque conversion gain.

Next, the steering system friction compensation process executed in S109 described above will be described with reference to the flowchart of FIG.
First, in S201, it is determined whether or not the in-lane yaw angle θyaw of the host vehicle is in the departure direction. If it is not in the departure direction, the process proceeds to S202, and the absolute value of the yaw rate | γ | and the absolute value of the target yaw rate | γt | Compare.

  As a result of this determination, if | γ | ≦ | γt |, the process proceeds to S203, and in the case of a left turn (sign “+”), friction compensation is performed to increase the value of the yaw rate γ toward the target yaw rate γt. On the other hand, + Tfc is set to the value of the torque Tfric (Tfric = + Tfc). On the other hand, when turning right (sign “−”), the value of the friction compensation torque Tfric is decreased in order to decrease the value of the yaw rate γ toward the target yaw rate γt. Set -Tfc to the value (Tfric = -Tfc) and exit the routine. Note that Tfc is a positive compensation torque value set in advance by experiment, calculation, etc., and may be a value variably set by an actual steering angle θp, an estimated value of friction torque estimated from the steering torque, or the like. .

  If the determination result of S202 is | γ |> | γt |, the process proceeds to S204, and in the case of a left turn (sign “+”), the value of the yaw rate γ should be decreased toward the target yaw rate γt. -Tfc is set to the value of the friction compensation torque Tfric (Tfric = -Tfc). On the other hand, in the case of right turn (symbol "-"), the yaw rate γ is increased toward the target yaw rate γt. Set + Tfc to the value of the friction compensation torque Tfric (Tfric = + Tfc) and exit the routine.

  As a result of the determination in S201 described above, when it is determined that the lane yaw angle θyaw of the host vehicle is the departure direction and it is determined that the departure prevention control is being executed, the process proceeds to S205, and the absolute value | γ | of the yaw rate and the target The absolute value of the yaw rate | γt | is compared.

  As a result of the determination in S205, if | γ | ≦ | γt |, the process proceeds to S206, and the value of the yaw rate γ is directed to the target yaw rate γt in the case of left turn (symbol “+”) as in S203 described above. In order to increase the friction compensation torque Tfric, the value of + Tfc is set (Tfric = + Tfc). On the other hand, in the case of right turn (symbol “−”), the value of the yaw rate γ is decreased toward the target yaw rate γt. Therefore, -Tfc is set to the value of the friction compensation torque Tfric (Tfric = -Tfc) and the routine is exited.

  If | γ |> | γt | is determined as a result of the determination in S202, the process proceeds to S207, and compensation in a direction in which the absolute value of the yaw rate decreases in order to bring the yaw rate γ closer to the target yaw rate γt is prohibited. In other words, the routine exits the routine by setting the value of the friction compensation torque Tfric to 0 to prohibit the compensation by the friction compensation torque Tfric that controls the steering back direction.

  An example of the yaw rate γ (actual yaw rate γ) from the yaw rate sensor 34, the target yaw rate γt, and the set friction compensation torque Tfric in the lane departure prevention control described above will be described with reference to the time chart of FIG. The description of FIG. 5 shows an example in which the target yaw rate γt in the left turn (“+” sign) direction is input.

  First, as shown in FIG. 5 (a), the departure prevention control is activated in a state where the vehicle is in the direction of departure from the lane and the yaw angle θyaw is directed, and at time t1, as shown in FIG. 5 (b). When the target yaw rate γ is input, the actual yaw rate γ is increased.

  As shown in FIG. 5 (a), since the vehicle is heading in the direction of departure from the lane, as shown in FIG. 5 (b), the target yaw rate γt is input by the departure prevention control until time t5. From time t1 to time t5, γ ≦ γt from time t1 to time t2, γ> γt from time t2 to time t3, and γ ≦ γt from time t3 to time t4. Γ> γt between time t4 and time t5.

  As shown in FIG. 5 (a), after the time t5, the vehicle is not in the direction of departure from the lane, so that the input of the target yaw rate γt by the departure prevention control is lost, as shown in FIG. 5 (b). Γ> γt between time t5 and time t6, γ ≦ γt between time t6 and time t7, and γ> γt after time t7.

  In the relationship between the target yaw rate γt and the actual yaw rate γ shown in FIG. 5B, in this embodiment, in order to basically compensate the friction torque of the steering system, as shown in FIG. Like the friction compensation torque Tfric after time t5, the friction compensation torque Tfric is added in the direction in which the actual yaw rate γ approaches the target yaw rate γt to compensate the friction torque of the steering system, and the friction feeling felt by the driver is stabilized. Steering feeling can be improved.

  However, when the vehicle is in the departure direction and the departure prevention control is activated, such as between the time t1 and the time t5, when the steering satisfying γ ≦ γt is controlled in the increasing direction. In the case where only the friction compensation torque Tfric is added and the steering is controlled in the return direction so that γ> γt, the friction compensation torque Tfric is set to zero. In this way, by adding the friction compensation torque Tfric only when the steering is controlled in the increasing direction, the steering is controlled in the increasing direction and in the returning direction without causing excessive steering. In this case, unnecessary fluctuations in the steering torque caused by the addition of the friction compensation torque Tfric can be prevented, and it is possible to reliably prevent the steering feeling from deteriorating due to the occurrence of steering torque hunting.

1 Electric power steering device (steering means)
2 Steering shaft 4 Steering wheel 5 Pinion shaft 10L, 10R Wheel 12 Electric motor 20 Steering control unit (deviation prediction means, target turning amount calculation means, control amount correction means, control correction change means)
21 motor drive unit 31 forward recognition device (lane detection means)
32 Vehicle speed sensor 33 Steering angle sensor 34 Yaw rate sensor 35 Cant angle detection sensor 40 Alarm control device

Claims (3)

Lane detection means for detecting the lane in which the vehicle is traveling;
Deviation prediction means for predicting deviation from the lane based on vehicle position information and driving conditions in the lane,
A target turning amount calculating means for calculating a target turning amount to be added to the vehicle necessary to prevent the departure from the lane based on the predicted departure from the lane;
Steering means that is operated by inputting a control amount corresponding to the target turning amount;
A correction amount for the control amount is set in advance based on a change in the actual turning amount caused by the operation of the steering means, and the target turning amount is compared with the actual turning amount to set the correction amount to the control amount. Control amount correction means for correcting by adding,
Control correction changing means for changing the correction by the control correction means depending on whether the vehicle is in a lane departure direction or not.
A lane departure prevention control device for a vehicle, comprising:   The control correction changing means sets the correction amount to 0 when the vehicle is in a lane departure direction and the actual turning amount exceeds the target turning amount, while the actual turning amount is If the target turning amount does not exceed the target turning amount, the correction amount is added in the direction in which the actual turning amount approaches the target turning amount, and if the vehicle is not in the lane departure direction, the actual turning amount is 2. The vehicle lane departure prevention control device according to claim 1, wherein the correction amount is added in a direction approaching the target turning amount.   3. The vehicle lane departure prevention control device according to claim 1, wherein the correction amount set by the control amount correction unit is a compensation torque of a friction torque in the steering unit.

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