JP2002193126A - Lane follow-up control device of vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lane follow-up control device for a vehicle capable of judging driver steering intervention with small steering torque when the vehicle substantially rectilinearly runs with good accuracy without a torque sensor. SOLUTION: This lane follow-up control device for the vehicle is provided with a control unit 10 for outputting a control command for generating steering torque following up the running lane to a motor 6 for automatic steering provided on an automatic steering mechanism 13. In the case where the absolute value |ρ| of road curvature is the threshold ρth or less and the absolute value |Gy| of lateral acceleration is the threshold Gyth or more, the driver steering intervention is decided, and steering intervention processing is conducted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle lane-following control device for controlling a vehicle to follow a running lane with a steering torque of a steering actuator without operating a driver.

[0002]

2. Description of the Related Art There is known a lane-following control device which detects a road environment such as a lane in which a vehicle travels by a camera or the like and automatically steers a front wheel by a steering actuator.

In such a lane-following control device, as a method of determining the driver's steering intervention during automatic driving,
For example, as disclosed in Japanese Patent Application Laid-Open No. H10-194150, there is known an apparatus that determines a driver's steering intervention by detecting a driver's steering torque using a torque sensor.

Japanese Patent Application Laid-Open No. 10-203 discloses a technique for detecting a steering angle or a steering angular velocity to determine the intervention of steering.
No. 394 publication.

[0005]

However, the one that determines the driver's steering intervention using the above-described torque sensor has the following problems.

(1) If the torque sensor is laid out between the wheel and the steering actuator, an input (road reaction torque) from the road surface to the steered wheel is detected. Although it is necessary to lay out the torque sensor, it is difficult to lay out the torque sensor around the steering column, for example, near the combination switch in terms of securing space.

(2) When a torque sensor is installed in a steering system, if the torsional rigidity is reduced to improve detection accuracy, it often becomes a problem in improving the steering feeling.

(3) The driver's steering intervention is determined by calculating a target torque corresponding to the deviation between the target steering angle and the actual steering angle, and the difference between the target torque and the actually detected torque exceeds the determination threshold. When the lane following performance is increased, a large torque is required even at the moment, so that the erroneous determination is made to prevent the erroneous determination even when the target torque becomes large. Must be set large. As a result, there is a problem that it is not possible to determine the driver intervention with a small torque.

On the other hand, as a method of determining the driver's steering intervention without using the torque sensor, there is a method of determining that the driver's steering intervention is performed when the deviation between the command steering angle and the actual steering angle exceeds a predetermined value. The command steering angle defined here is
Refers to the amount calculated to cause the vehicle to follow the road. Generally, the command steering angle is calculated based on the dynamic characteristics of the vehicle to be controlled. Therefore, the curvature of the road, the vehicle speed, the lateral displacement relative to the lane, and the yaw relative to the lane. Calculated from the corner. In particular, a lateral displacement associated with the lateral displacement of the vehicle or a feedback component of the yaw angle is always included.

This method can be used only when the command steering angle exists in the control law, and the control law in which the command steering angle exists is a servo control that matches the command steering angle with the actual steering angle. Therefore, these deviations hardly occur during the control (the controllability deteriorates when the deviation is allowed in the servo control). Therefore, there is a difficulty in setting the threshold value of the deviation. In other words, if the threshold value is set to a large value, a large steering force is required to determine that the intervention is performed, and if the threshold value is set to a small value, erroneous cancellation due to the intervention determination frequently occurs during the control. .

Further, as a method for determining the driver's steering intervention without using the torque sensor, there is a method for determining the steering intervention using the steering angular velocity. According to this method, if the threshold value is set to a large value, it is not possible to determine that the steering intervention is performed even when the driver performs the steering intervention during substantially straight traveling (the steering angular velocity is slow). Further, if the threshold value is set to a small value, erroneous cancellation due to intervention determination frequently occurs during control. That is, it is difficult to quickly release the control without giving the driver an uncomfortable feeling while ensuring the performance of the lane following control.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. It is an object of the present invention to perform driver steering intervention using a small steering torque when a vehicle is traveling substantially straight without using a torque sensor. It is an object of the present invention to provide a vehicle lane-following control device capable of accurately determining the vehicle lane.

[0013]

In order to achieve the above object, according to the first aspect of the present invention, at least the traveling lane information detected by the traveling lane information detecting means and the steering angle detected by the steering angle detecting means are used. A lane tracking control device for a vehicle that includes a steering torque control unit that outputs a command to generate a steering torque that follows a traveling lane to a steering actuator provided in a steering mechanism; Means, a lateral acceleration detecting means for detecting a lateral acceleration generated by the vehicle, and driver steering when the road curvature is equal to or less than a first predetermined value and the lateral acceleration is equal to or more than a second predetermined value. A driver steering intervention determining means for determining that the vehicle is in an intervention state; Or wherein the steering intervention processing means for performing reduction processing of the control degree, was provided.

According to a second aspect of the present invention, in the vehicle lane following control device according to the first aspect, the driver steering intervention determining means determines a boundary value for determining whether or not the traveling road is a substantially straight road by a first value. Is a means set as a predetermined value of.

According to a third aspect of the present invention, in the vehicle lane following control apparatus according to the first or second aspect, the driver steering intervention determining means generates in response to a disturbance that can be constantly generated in the vehicle. It is a means for setting the maximum value of the lateral acceleration as a second predetermined value.

[0016]

According to the first aspect of the present invention, at the time of traveling by the lane following control, the steering torque control means detects at least the traveling lane information detected by the traveling lane information detection means and the steering angle detection means. Based on the steering angle, a command to generate a steering torque that follows the traveling lane is output to a steering actuator provided in the steering mechanism.

If the driver intervenes in the course of traveling by the lane following control, the driver steering intervention determining means determines that the road curvature by the road curvature detecting means is equal to or less than a first predetermined value and the lateral acceleration detecting means When the lateral acceleration due to the vehicle is greater than or equal to the second predetermined value, it is determined that driver steering intervention is being performed. When the driver intervention intervention determining means determines that steering intervention is being performed, the steering torque control is released. Or a prohibition or control degree reduction process is performed.

That is, it can be determined that the vehicle is traveling substantially straight, based on the condition that the road curvature is equal to or less than the first predetermined value. When the vehicle travels substantially straight, the lateral acceleration detected by the lateral acceleration detecting means is substantially "0". However, when the vehicle moves from the substantially straight traveling state to the steering intervention state by the driver, the absolute value of the lateral acceleration increases. The excessive occurrence of the lateral acceleration can be regarded as the driver's steering intervention. That is, the second predetermined value that is the threshold value for setting the lateral acceleration can be set to a small value.

Therefore, the driver steering intervention using a small steering torque can be accurately determined when the vehicle is traveling substantially straight ahead, even though the driver steering intervention does not use the torque sensor.

According to the second aspect of the present invention, the driver steering intervention determining means sets a boundary value as to whether or not the traveling road is a substantially straight road as the first predetermined value.

That is, in addition to the logic used in the present invention, for example, "the steering speed is set to a predetermined value (30 to 40 deg /
sec) or more, it is determined to be an intervention. "However, there are cases in which it is difficult to determine if the steering is performed slowly, such as steering intervention during straight running, with this logic.

Therefore, the present logic can be limited to straight traveling by setting the boundary value for determining whether or not the traveling road is a substantially straight road to the first predetermined value. As a result, in the driver steering intervention determination, it can be positioned as a complement to the logic or the like based on the steering speed.

According to the third aspect of the present invention, in the driver steering intervention determining means, the maximum value of the lateral acceleration generated in response to the disturbance that can steadily occur in the vehicle is set as the second predetermined value. .

Accordingly, the disturbance that can be constantly generated with respect to the vehicle when traveling straight ahead includes a road surface cant (inclination), and the maximum value of the lateral acceleration that can be generated in response to this is defined as the second predetermined value. Therefore, erroneous determination of driver steering intervention due to steady disturbance can be reliably prevented.

In other words, it is a prerequisite that the lane following control is executed with the control corresponding to the road surface cant as an upper limit. That is, there is a disturbance such as a cross wind besides the steering intervention as the suddenly generated lateral acceleration that is not stationary, but does not correspond to such a sudden disturbance such as the cross wind.

[0026]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A description will be given based on a first embodiment corresponding to the invention according to the third aspect to the invention according to the third aspect.

(First Embodiment) First, the configuration will be described. FIG. 1A is a diagram showing a schematic side view of a vehicle on which the lane tracking control device of the first embodiment is mounted, and FIG. 1B is an overall system diagram showing the lane tracking control device of the first embodiment.

In FIG. 1B, 1FR and 1FL indicate front wheels, 1RL and 1RL indicate rear wheels, and front wheels 1FR and 1FL.
Is provided with a general rack and pinion type steering mechanism. The steering mechanism includes a rack 2 connected to a steering shaft (tie rod) of the front wheels 1FR and 1FL, a pinion 3 meshing with the rack 2, and a steering shaft 5 for rotating the pinion 3 by a steering torque given to a steering wheel 4. It has.

An automatic steering mechanism 1 which constitutes a steering actuator for automatically steering the front wheels 1FR, 1FL is provided above the pinion 3 in the steering shaft 5.
3 are provided. The automatic steering mechanism 13 includes a driven gear 14 mounted coaxially with the steering shaft 5, a drive gear 15 meshing with the driven gear 14, and an automatic steering motor 16 for driving the drive gear 15 to rotate. Note that a clutch mechanism 17 is interposed between the automatic steering motor 16 and the drive gear 15, and the clutch mechanism 17 is engaged only during automatic steering control, and otherwise, the clutch mechanism 17 is in a non-engaged state. As a result, the rotational force of the automatic steering motor 16 is not input to the steering shaft 5.

Various sensors are mounted on the vehicle. In the figure, reference numeral 21 denotes a steering angle sensor (steering angle detecting means) which detects a steering angle θ from the rotation angle of the steering shaft 5 and outputs the detected steering angle θ to the control unit 10. A vehicle speed sensor 22 is attached to the output side of an automatic transmission (not shown), and the vehicle speed V detected by the vehicle speed sensor 22 is also output to the control unit 10. Further, a lateral acceleration sensor 23 is attached as lateral acceleration detecting means for detecting lateral acceleration generated in the vehicle. The lateral acceleration Gy detected by the lateral acceleration sensor 23 is also output to the control unit 10.

Further, as shown in FIG. 1 (a), a monocular camera 25 such as a CCD camera is installed on a fixed portion such as an inner mirror stay in the vehicle interior to capture the situation in front of the vehicle, and to store the captured image data. Is output to the camera controller 26. This camera controller 26 (traveling lane information detecting means and road curvature detecting means) is, for example, disclosed in
As described in JP-A-102499, a white line near the own vehicle is detected by a process such as binarization of image data of the monocular camera 25, and a relative lateral position of the vehicle with respect to a road at a predetermined vehicle forward gazing point. Calculate the displacement y, the yaw angle φ with respect to the tangent to the white line of the vehicle, and the road curvature ρ ahead of the traveling lane,
These are output to the control unit 10.

The control unit 10 is constituted by a discretized digital system such as a microcomputer (not shown), and based on the input yaw angle φ, relative lateral displacement y, and road curvature ρ, the most optimal a target steering angle theta ^* is calculated, so as to match the actual steering angle theta detected by the steering angle sensor 21 to the target steering angle theta ^*, it calculates a supply current iM for the automatic steering motor 16, the supply current iM Is subjected to a current limiting process, pulse width modulated, converted into a pulse current, and output to a motor 16 for automatic steering to thereby control the duty of the motor 16 for automatic steering.

Next, the operation will be described.

[Steering Control Processing] FIG. 2 is a flowchart showing a steering control processing procedure executed by the control unit 10, and each step will be described below. In addition,
This steering control process is executed as a timer interrupt process every predetermined time (for example, 10 msec).

First, in step S1, the steering angle sensor 2
1, the steering angle θ detected by the lateral acceleration sensor 23, the lateral acceleration Gy detected by the lateral acceleration sensor 23, the vehicle speed V detected by the vehicle speed sensor 18, the yaw angle φ detected by the camera controller 26, the relative lateral displacement y, and the road curvature ρ are read. It is.

In the next step S2, the following equation (1) is calculated based on the yaw angle φ, the relative lateral displacement y and the road curvature ρ to calculate the current target steering angle θ ^* (n). The previous target steering angle θ ^* (n−1) stored in the current target steering angle storage area is updated and stored in the previous target steering angle storage area, and the current target steering angle θ ^* (n) is stored in the current target steering angle storage area. The data is updated and stored in the target steering angle storage area. θ ^* (n) = Ka · φ + Kb · y + Kc · ρ (1) where Ka, Kb, and Kc are control gains that vary depending on the vehicle speed, and the target steering angle θ ^* (n) is rightward steering. Positive value at time, negative value at left steering.

Next, the process proceeds to step S3, in which a calculation according to the following equation (2) is performed, and PID control for matching the actual steering angle θ to the target steering angle θ ^* (n) is performed. Motor supply current iM to motor 16 for automatic steering
Is calculated and updated and stored in the motor supply current storage area. iM = Kvi (Kp + Ki / s + Kd · s) (θ ^* −θ) (2) where Kvi is a control gain for converting a voltage value to a current value, Kp is a proportional gain, Ki is an integral gain, and Kd is Differential gain. The reason that the motor supply current iM is calculated by the equation (2) is that the actual steering angle θ is calculated from the target steering angle θ ^* by a subtractor.
Is calculated, and the deviation Δθ between the two is calculated and supplied to an arithmetic unit to perform a PID control operation to obtain a target motor control voltage V ^*.
Is calculated, and the target motor control voltage V ^* is supplied to the voltage-current converter, so that the target motor control voltage V ^* has the control gain K
A motor control current iM is calculated by multiplying vi and a feedback control system for supplying the motor supply current iM to the automatic steering motor 16 is considered, and an equivalent operation is performed.

Next, the process proceeds to step S4, where it is determined whether the driver is in a steering intervention state (driver steering intervention determining means). In the case of the present invention, since the determination is made only when the traveling road is sufficiently straight, first, when the absolute value of the road curvature | ρ | is larger than the threshold value ρth (first predetermined value), it is determined that the intervention is performed. Not
The process proceeds to a normal process (step S5). Even when the absolute value of the road curvature | ρ | is equal to or smaller than the threshold value ρth,
If the absolute value of the lateral acceleration | Gy | is smaller than the threshold value Gyth (second predetermined value), the process proceeds to the normal process (step S5) without determining that the intervention is involved. That is, the absolute value of the road curvature | ρ
Is less than or equal to the threshold value ρth, and the absolute value of the lateral acceleration | Gy
When | is equal to or greater than the threshold value Gyth, it is determined that driver steering intervention has occurred, and the process proceeds to steering intervention processing (step S6). Here, the threshold value ρth is a boundary value indicating whether or not the traveling road is a substantially straight road. The threshold value Gyth is the maximum value of the lateral acceleration generated in response to disturbance (road cant) that can constantly occur in the vehicle.

If YES (non-steering intervention) is determined in step S4, the process proceeds to step S5, and step S5
Then, a pulse current modulated in pulse width in accordance with the motor supply current iM is output to the automatic steering motor 16 (steering torque control means).

If NO (steering intervention) is determined in step S4, the process proceeds to step S6, where the control is canceled or the control start is prohibited as steering intervention processing (steering intervention processing means).

[Steering Control Action] When the vehicle is traveling by the lane following control, in the flowchart of FIG. 2, step S 1 → step S 2 → step S 3 → step S 4 → step S
5, the target steering angle θ ^* (n) is calculated based on the yaw angle φ, the relative lateral displacement y, and the road curvature ρ, and the PID control for matching the actual steering angle θ to the target steering angle θ ^* (n) is performed. To supply the motor supply current i to the motor 16 for automatic steering.
M is calculated, the motor supply current iM is modulated into a pulse current, and a pulse current for generating a steering torque that follows the traveling lane is output to the automatic steering motor 16 provided in the automatic steering mechanism 13.

If the driver intervenes in the middle of the traveling by the lane following control, the absolute value of the road curvature | ρ | is equal to or less than the threshold value ρth and the absolute value of the lateral acceleration | Gy | in step S4 of FIG. Is greater than or equal to the threshold value Gyth, it is determined that driver intervention is being performed, and the process proceeds to step S6. In step S6, control cancellation or control start is prohibited as steering intervention processing.

That is, under the condition that the absolute value of the road curvature | ρ | is equal to or smaller than the threshold value ρth, it can be determined that the vehicle is traveling substantially straight. When the vehicle travels substantially straight, the lateral acceleration Gy detected by the lateral acceleration sensor 23 is substantially “0”.
When the vehicle shifts from the substantially straight traveling state to the steering intervention state by the driver, the absolute value | Gy | of the lateral acceleration Gy increases, and the excessive occurrence of the lateral acceleration Gy can be regarded as the driver's steering intervention. it can. That is, even if the threshold value Gyth of the absolute value of the lateral acceleration | Gy | is set to a small value, the driver's steering intervention can be determined.

Next, the effects will be described.

(1) The absolute value of the road curvature | ρ |
And the absolute value of the lateral acceleration | Gy |
When th is greater than or equal to th, it is determined that driver steering intervention is being performed, and steering intervention processing is performed.Thus, driver steering intervention determination that does not use a torque sensor, but small steering when the vehicle is traveling substantially straight ahead. The driver steering intervention by the torque can be accurately determined.

(2) Since the threshold value ρth of the absolute value of the road curvature | ρ | is used as the boundary value for determining whether or not the running road is a substantially straight road, the steering intervention determination logic based on the road curvature ρ and the lateral acceleration Gy When traveling straight ahead.

That is, the driver steering intervention is determined by:
In addition to this logic, for example, “the steering speed is a predetermined value (30
If it exceeds 40 deg / sec), it will be judged as intervention. "
However, there is a case where it is difficult to determine when the steering is performed slowly, such as the steering intervention during the straight running, with this logic. Therefore, this logic can be positioned as a complement to the steering intervention determination logic based on the steering speed. (3) Since the maximum value of the lateral acceleration generated in response to the disturbance that can constantly occur in the vehicle is set to the threshold value Gyth of the absolute value of the lateral acceleration | Gy | An erroneous determination of driver steering intervention due to a road surface cant that is obtained disturbance can be reliably prevented.

In other words, it is a precondition that the lane following control in the first embodiment is executed with the upper limit of the control corresponding to the road surface cant. That is, it is not stationary,
As the lateral acceleration Gy generated suddenly, there is a disturbance such as a side wind outside the steering intervention, but the idea is that it does not correspond to such a sudden disturbance such as the side wind.

(Other Embodiments) The present invention has been described with reference to the first embodiment. However, the specific structure is not limited to the first embodiment and is described in claims 1 to 3. The present invention includes any design changes that do not depart from the gist of the present invention.

For example, in the first embodiment, the lateral acceleration sensor 23 has been described as an example of the lateral acceleration detecting means. However, a means for estimating and calculating the lateral acceleration Gy from the vehicle speed V and the steering angle θ may be used.

Further, in the first embodiment, only the example of the driver steering intervention determination logic using the road curvature ρ and the lateral acceleration Gy effective when traveling straight ahead has been described. However, the steering speed (dθ) is included in the driver steering intervention determination logic. / Dt) is a predetermined value (3
It is also possible to add a logic for determining that the driver steering intervention is performed when the vehicle speed exceeds 0 to 40 deg / sec) or more, and to complement each other, so that the driver steering intervention determination is surely performed not only for straight traveling but also for turning. .

In the first embodiment, an example has been described in which, when it is determined that driver intervention is being performed, control release or control initiation is prohibited as steering intervention processing. You may make it small compared with.

[Brief description of the drawings]

FIG. 1 is a schematic side view and a whole system diagram of a vehicle equipped with a lane tracking control device of a first embodiment.

FIG. 2 is a flowchart illustrating a steering control process performed by a control unit of the first embodiment.

[Explanation of symbols]

1FR, 1FL Front wheel 1RL, 1RL Rear wheel 2 Rack 3 Pinion 4 Steering wheel 5 Steering shaft 10 Control unit (steering torque control means) 13 Automatic steering mechanism (Steering actuator) 14 Driven gear 15 Drive gear 16 Automatic steering motor 17 Clutch mechanism 21 Steering angle sensor (steering angle detecting means) 22 Vehicle speed sensor 23 Lateral acceleration sensor (lateral acceleration detecting means) 25 Monocular camera 26 Camera controller (traveling lane information detecting means and road curvature detecting means)

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) // B62D 101: 00 B62D 101: 00 111: 00 111: 00 113: 00 113: 00 137: 00 137: 00 (72 Inventor Masayasu Shimakage 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture, Nissan Motor Co., Ltd. (72) Inventor Hiroshi Kawazoe 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture, Nissan Motor Co., Ltd. F-term (reference) in Nissan Motor Co., Ltd. 2 Takaracho, Kanagawa-ku, Yokohama 3D032 CC20 CC30 DA03 DA23 DA27 DA29 DA32 DA81 DA84 DB12 DC38 DD10 DD17 DE09 EA01 EB04 EC22 EC27 EC34 GG01

Claims (3)

[Claims] 1. A steering torque that follows a traveling lane to a steering actuator provided in a steering mechanism based on at least traveling lane information detected by traveling lane information detecting means and a steering angle detected by steering angle detecting means. A lane following control device for a vehicle including a steering torque control unit that outputs a command to generate a road curvature detection unit that detects a curvature of a traveling road; a lateral acceleration detection unit that detects a lateral acceleration generated by the vehicle; When the road curvature is equal to or less than a first predetermined value and the lateral acceleration is equal to or more than a second predetermined value, driver steering intervention determining means for determining that driver steering intervention is being performed; and Means for canceling or prohibiting the steering torque control or reducing the degree of control when it is determined that the intervention is the steering intervention. Lane keeping control apparatus for a vehicle, characterized in that the. 2. The vehicle lane following control device according to claim 1, wherein the driver steering intervention determining means sets a boundary value as to whether or not the traveling road is a substantially straight road as a first predetermined value. A lane following control device for a vehicle. 3. The vehicle lane following control device according to claim 1, wherein the driver steering intervention determining means determines a maximum value of a lateral acceleration generated in response to a disturbance that can be constantly generated in the vehicle. A lane following control device for a vehicle, characterized in that the means is set as a second predetermined value.