Vehicle controller and vehicle control method

Abstract

To ensure steering stability in course of curve travel even when lane recognition based on a camera image fails during the curve travel.SOLUTION: A vehicle controller includes: a lane recognition unit that recognizes lane information in an advancing direction from an image; a curvature calculation unit that calculates curvature information on a travel route from the lane information; a turning radius calculation unit that calculates a turning radius of an own vehicle from a vehicle speed and steering angle; an LKAS processing unit that obtains a deviation of a vehicle position from the travel route and calculates a steering angle which causes the vehicle position to approach the travel route; an assist torque calculation unit that calculates a steering assist torque with which the calculated steering angle is sustained; and a vehicle control unit that outputs a command, which causes the calculated steering assist torque to be generated, to an electric power steering system. When lane recognition fails, the LKAS processing unit calculates the steering angle which causes the turning radius to approach the curvature based on the curvature information stored before lane recognition fails. The vehicle control unit outputs the command, which is based on the steering angle calculated by the LKAS processing unit, to the electric power steering system only within a predetermined period since the failure of the lane recognition.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a vehicle control device and a vehicle control method that assists in keeping the vehicle in its lane while the vehicle is traveling. [Background technology]

[0002] A Lane Keep Assist System (hereinafter referred to as "LKAS") is a function that helps the vehicle keep in its lane while traveling by recognizing the lane the vehicle is traveling in based on images captured by an onboard camera and generating an appropriate assist torque in the electric power steering. There are two types of LKAS: one that generates assist torque only when the vehicle is about to deviate from its lane, and one that constantly generates assist torque to keep the vehicle centered in the lane. The latter type of LKAS needs to be able to handle not only straight road driving but also curved driving.

[0003] Therefore, in Patent Document 1, for example, claim 1 states that "A steering force assist device which reduces the driver's steering force when turning a curve by applying a steering torque to the steering wheel in accordance with the curve conditions of the lane ahead in the vehicle's traveling direction, characterized in that the steering force assist device comprises: curvature calculation means for calculating the curvature of the lane ahead in the traveling direction; vehicle speed detection means for detecting the vehicle speed of the vehicle; control torque calculation means for calculating a control torque based on the curvature calculated by the curvature calculation means and the vehicle speed detected by the vehicle speed detection means; and control means for controlling the steering actuator so that the control torque calculated by the control torque calculation means is generated in a direction that helps the vehicle turn the curve." Based on the curvature of the curve ahead and the vehicle speed, an assist torque is generated that results in a steering angle corresponding to the curvature.

[0004] However, Patent Document 1 does not mention assist torque control in the case where lane recognition failure occurs while driving around a curve, when the lane cannot be recognized from the camera image due to the effects of backlight, smoke, thick fog, snow, rain, etc., i.e., when the curvature of the curve ahead cannot be recognized.

[0005] When the system-led vehicle control becomes difficult, the driver generally takes over control of the vehicle. Patent Document 2 is known as a conventional technique of this type.

[0006] In the document, paragraph 0007 states, "When the driver is notified of a warning to the driver that the automatic lane change function will be stopped and a request to take over operation is requested due to a departure from the ODD (Note: operational design area), it is expected that the vehicle's behavior may become unstable due to the driver panicking in response to the notification and overriding the vehicle with excessive steering operation or excessive braking / accelerating operation." The solution section of the abstract states, "...when the vehicle deviates from the system operational design area, the upper limit of the steering torque or steering angle, which is set according to the vehicle speed, is changed to a value lower than the normal value within the system operational design area."

[0007] In this way, Patent Document 2 attempts to ensure driving stability when the steering role is transferred from the system to the driver by limiting the effects of excessive steering by a panicked driver immediately after the steering role is transferred from the system to the driver. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 11-147473 [Patent Document 2] Patent Publication No. 2022-171709 Summary of the Invention [Problem to be solved by the invention]

[0009] However, even in Patent Document 2, it cannot be said that sufficient consideration has been given to measures against failure to recognize lanes during steering control by LKAS, and there is a risk that restricting the driver's steering may actually make it easier for the vehicle to deviate from its lane.

[0010] Therefore, an object of the present invention is to provide a vehicle control device and a vehicle control method that ensures driving stability while traveling around a curve even if lane recognition based on camera images is lost while traveling around a curve. [Means for solving the problem]

[0011] In order to solve the above problem, a vehicle control device that assists in keeping the vehicle in its lane while the vehicle is traveling includes a lane recognition unit that recognizes lane information in the traveling direction based on image information from an on-board camera, a curvature calculation unit that calculates curvature information of a traveling route based on the lane information, a turning radius calculation unit that calculates a turning radius of the host vehicle based on vehicle speed information from a vehicle speed sensor and steering angle information from a steering angle sensor, an LKAS processing unit that calculates a deviation between the vehicle position and the traveling route and calculates a steering angle at which the vehicle position approaches the traveling route, and a steering assist system that maintains the steering angle calculated by the LKAS processing unit. and a vehicle control unit that outputs a command to generate the steering assist torque calculated by the assist torque calculation unit to an electric power steering, wherein when lane recognition by the lane recognition unit fails, the LKAS processing unit calculates a steering angle at which the turning radius approaches a curvature based on curvature information stored before the lane recognition failure, and the vehicle control unit outputs a command based on the steering angle calculated by the LKAS processing unit to the electric power steering only within a predetermined period from the lane recognition failure. Effect of the Invention

[0012] According to the vehicle control device and vehicle control method of the present invention, even if lane recognition based on camera images is lost while traveling around a curve, driving stability while traveling around a curve can be ensured. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a functional block diagram of the vehicle system according to the first embodiment. [Diagram 2] An example of mapping lane information from a lane image. [Diagram 3] An example of calculating the curvature at each point of a driving path from lane information. [Figure 4] 6 is a graph showing the transition of the coefficient of the LKAS assist torque before and after lane recognition failure. [Diagram 5] 4 is a control flowchart when LKAS is executed. [Figure 6] FIG. 11 is a functional block diagram of a vehicle system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a vehicle control device and a vehicle control method of the present invention will be described with reference to the drawings. EXAMPLES

[0015] First, a vehicle system 1 including a vehicle control device 10 according to a first embodiment of the present invention will be described with reference to FIGS.

[0016] 1 is a functional block diagram of a vehicle system 1 according to the embodiment 1. As shown in the figure, the vehicle system 1 according to the embodiment is a system including a vehicle control device 10, a camera sensor 20, a vehicle speed sensor 30, a steering angle sensor 40, an electric power steering device 50, and an alarm device 60.

[0017] The camera sensor 20 is an in-vehicle camera that is installed so as to be able to capture an image of the area ahead of the vehicle, and outputs image information I P The vehicle speed sensor 30 outputs vehicle speed information I V The steering angle sensor 40 outputs steering angle information I A is output to the vehicle control device 10.

[0018] The electric power steering 50 is a mechanism that generates an assist torque to assist the driver in steering in response to a command from the vehicle control device 10, and when the LKAS is executed, it controls the steering system so that the vehicle runs in the center of the lane without the driver steering. The notification device 60 is a device that notifies the driver of a change in the steering subject in response to a command from the vehicle control device 10 when the steering subject is handed over from the system to the driver, and specifically includes a liquid crystal display or lamp that notifies visually, a speaker that notifies audibly, etc.

[0019] <Vehicle control device 10> The vehicle control device 10 includes a lane recognition unit 11, a curvature calculation unit 12, a turning radius calculation unit 13, an LKAS processing unit 14, an assist torque calculation unit 15, and a vehicle control unit 16. Specifically, the vehicle control unit 10 is a computer including a calculation unit such as a CPU, a storage device such as a semiconductor memory, and hardware such as a communication device. The calculation unit executes a predetermined program to realize each of the above-mentioned functions, but the following description will be given while omitting such well-known techniques as appropriate.

[0020] The lane recognition unit 11 recognizes image information I acquired from the camera sensor 20. P Then, lane recognition processing is performed on the image, and the lane image P R In addition, the lane recognition unit 11 obtains the lane image P R Then, a mapping transformation is performed on the lane information I R The mapping transformation executed here is to obtain the lane image P R This corresponds to the generation of a bird's-eye view of the lane ahead of the vehicle. P From lane image P R It also has the ability to determine that a lane recognition failure has occurred if a lane recognition image cannot be generated.

[0021] The curvature calculation unit 12 calculates the driving path I C The curvature information Crv[x] of each point is transformed into the lane information IR For example, the lane information I shown in FIG. R In the case where the lane information I R Route I is a path connecting the center points of the road width indicated by C and calculates the array of curvature information Crv[x] by sequentially obtaining the curvature at a position a distance x from the front end of the host vehicle.

[0022] The turning radius calculation unit 13 uses the vehicle speed information I V and steering angle information I from the steering angle sensor 40 A Based on this, the current turning radius r of the host vehicle is calculated.

[0023] The LKAS processing unit 14 detects the center of the lane (travel route I C ) and after a predetermined control period (e.g., 100 ms), the vehicle position is determined to be on the same path as the travel route I C An example of this calculation method is to calculate the steering angle so that the lane center (traveling path I) is approached based on the curvature and turning radius r at the current vehicle position. C ) steering angle position is calculated.

[0024] The assist torque calculation unit 15 calculates a steering assist torque for maintaining the steering angle position calculated by the LKAS processing unit 14.

[0025] The vehicle control unit 16 outputs a command to the electric power steering 50 to generate the assist torque calculated by the assist torque calculation unit 15. As a result, the electric power steering 50 generates an assist torque suitable for keeping the host vehicle traveling in the center of the lane, and appropriately assists the driver's steering. In addition, when lane recognition is failed, the vehicle control unit 16 notifies the driver via the notification device 60 that the LKAS processing has been released.

[0026] <Control when lane recognition is not possible> In unfavorable imaging environments such as backlight, rain, snow, thick fog, and smoke, the lane recognition unit 11 may not recognize the image information I P From Lane Information I RIn some cases, lane recognition failure may occur, in which the vehicle cannot recognize the lane. In this case, the LKAS processing unit 14 estimates the curvature at the current driving position using the curvature information Crv[x] generated by the curvature calculation unit 12 before the lane recognition failure, using the following formula: In the following formula, v is the vehicle speed detected by the vehicle speed sensor 30, and t is the elapsed time from the time of lane recognition failure.

[0027] Curvature of current running position = Crv [v × t] By using this formula to calculate the curvature of the current driving position, even after lane recognition failure, the LKAS processing unit 14 can calculate a steering angle that matches the turning radius and curvature, and continue LKAS processing.

[0028] However, the curvature information Crv[x] generated before the lane recognition failure has an end, and the curvature information Crv[x] near the end is unreliable, so that when the lane recognition failure occurs, it is necessary to immediately shift to the driver's steering control. Therefore, in the assist torque calculation unit 15 of this embodiment, the original output is multiplied by a coefficient k(t) described later to reduce the influence of the LKAS processing after the lane recognition failure.

[0029] In the graph of Fig. 4, the horizontal axis indicates time, and the vertical axis indicates the magnitude of the coefficient k(t) of the LKAS assist torque. As shown here, the coefficient k(t) is 1 before the time when the lane recognition failure occurs (time 0), the coefficient k(t) gradually decreases from 1 to 0 during the period from time 0 to time t1, and the coefficient k(t) after time t1 is 0. Note that time t1 is a variable time, and increases or decreases, for example, in proportion to the amount of data of the curvature information Crv[x] and inversely proportional to the vehicle speed v.

[0030] The reason for setting the coefficient k(t) as shown in Figure 4 is as follows. (1) Before the lane recognition failure, the LKAS processing unit 14 can normally perform LKAS processing, and therefore the coefficient k(t) is set to 1 to set the main body of lane keeping control to the LKAS processing unit 14. Note that even if the coefficient k(t) is 1, the driver's steering is effective, and therefore, if an object has fallen in the center of the lane, the driver can steer the vehicle to avoid the center of the lane. (2) Although the lane recognition failure is notified to the driver by the alarm device 60, the driver may not be able to steer in time immediately after the alarm. In addition, the reliability of the curvature information Crv[x] is high immediately after the occurrence of lane recognition failure, so the reliability of the LKAS processing based on the curvature information Crv[x] is also considered to be high. Therefore, the coefficient k(t) is increased immediately after the occurrence of lane recognition failure so that steering by the LKAS processing unit 14 can be substantially continued even if the driver does not steer. (3) If it is just before time t1, a sufficient amount of time has passed since the lane recognition failure notification, and it is highly likely that the driver has started steering. In addition, it is close to the end of the curvature information Crv[x] prepared before the lane recognition failure, and the reliability of the LKAS processing based on the curvature information Crv[x] is also considered to be low. Therefore, at this point in time, the coefficient k(t) just before time t1 is made small in order to suppress the influence of the unreliable LKAS processing. (4) After time t1, the curvature information Crv[x] no longer exists, so the LKAS processor 14 cannot continue steering. Therefore, in order to have the driver take sole responsibility for steering control after time t1, the coefficient k(t) after time t1 is set to 0.

[0031] <Flowchart> Next, the flow of LKAS control will be described in detail using the flowchart in Fig. 5. Note that Fig. 5 illustrates the process for one control period (e.g., 100 ms), and the process in Fig. 5 is repeated during execution of LKAS control.

[0032] First, in step S1, the lane recognition unit 11 receives image information I P From lane image P R (See Figure 2(a)).

[0033] In step S2, the lane recognition unit 11 judges whether lane recognition is defective. R If the lane image P RIf the vehicle cannot recognize the lane, the process proceeds to step S6. Note that this does not deny the implementation of a function for assuming that the vehicle ahead is traveling in the center of the lane and setting a virtual lane when the lane is obscured by the vehicle ahead.

[0034] In step S3, the lane recognition unit 11 recognizes the lane image P R From Lane Information I R (See Figure 2.)

[0035] In step S4, the curvature calculation unit 12 calculates the curvature of each point on an imaginary driving line in the center of the lane, and stores the curvature information Crv[x] (see FIG. 3).

[0036] In step S5, the LKAS processing unit 14 calculates a steering assist torque such that the vehicle travels in the center of the lane. After that, the assist torque calculation unit 15 transmits an instruction value corresponding to the steering assist torque to the vehicle control unit 16. As a result, the vehicle control unit 16 updates the control value of the assist torque of the electric power steering 50 and ends the current control cycle.

[0037] On the other hand, in step S6, the vehicle control unit 16 notifies the driver via the notification device 60 of the occurrence of the lane recognition failure and the start of LKAS deactivation.

[0038] In step S7, the turning radius calculation unit 13 calculates the turning radius from the outputs of the vehicle speed sensor 30 and the steering angle sensor 40, and the LKAS processing unit 14 estimates the curvature at the current location from the curvature information Crv[x] based on the vehicle speed and the elapsed time since the occurrence of the lane recognition failure.

[0039] In step S8, the LKAS processing unit 14 calculates the difference between the obtained current curvature and the turning radius, and if there is a discrepancy, the assist torque calculation unit 15 calculates the assist torque in the direction in which the two coincide with each other.

[0040] In step S9, the assist torque calculation unit 15 calculates a steering assist torque by multiplying the original steering assist torque based on the LKAS processing unit 14 obtained in step S8 by the current coefficient k(t). Then, the vehicle control unit 16 updates the control value of the assist torque of the electric power steering 50 based on the steering assist torque multiplied by the coefficient k(t).

[0041] In step S10, the LKAS processor 14 determines whether the coefficient k(t) of the LKAS output has become 0, indicating a complete shift to driver-driven steering control. If the coefficient k(t) is 0, the process proceeds to step S11, and if the coefficient k(t) is not 0, the process in FIG. 5 is terminated.

[0042] In step S11, the LKAS processing unit 14 cancels the LKAS processing. That is, from then on, steering is controlled only by the driver. At this time, the vehicle control unit 16 may notify the notification device 60 that the LKAS processing has ended.

[0043] By using the processing of FIG. 5 described above to retain the curvature of the road ahead of the vehicle just before lane recognition failure and the curvature of the road ahead of that, an assist torque is generated for a predetermined period of time so that the steering angle corresponds to the curvature of the road ahead of the vehicle after lane recognition failure, thereby reducing the probability of lane departure and increasing steering stability.

[0044] Therefore, according to the vehicle control device of this embodiment, even if lane recognition based on the camera image while traveling around a curve is lost, it is possible to ensure driving stability while traveling around a curve. EXAMPLES

[0045] Next, a vehicle control device 10 according to a second embodiment of the present invention will be described with reference to the functional block diagram of Fig. 6. Note that a duplicated description of points common to the first embodiment will be omitted.

[0046] As shown in Fig. 6, the vehicle system 1 of this embodiment is a system in which map information from a Global Navigation Satellite System (GNSS) 70 is input to a curvature calculation unit 12 of a vehicle control device 10. Therefore, in the curvature calculation unit 12 of this embodiment, the lane information I generated by the lane recognition unit 11 is input to the curvature calculation unit 12 of this embodiment in the same manner as in the first embodiment. R In addition to being able to generate curvature information Crv[x] using R ' can also be used to generate curvature information Crv'[x].

[0047] Therefore, even in a situation where lane recognition is impaired and the method of Example 1 is unable to generate a sufficient amount of curvature information Crv[x], the LKAS processing unit 14 of this example can continue stable LKAS processing by using curvature information Crv'[x] based on map information. [Explanation of symbols]

[0048] 1: Vehicle system 10: Vehicle control device 11: Lane recognition unit 12: Curvature calculation part 13: Turning radius calculation section 14: LKAS processing section 15: Assist torque calculation section 16: Vehicle control unit 20: Camera sensor 30: Vehicle speed sensor 40: Steering angle sensor 50: Electric power steering 60: Notification device 70:GNSS

Claims

1. A vehicle control device that assists in lane keeping while a vehicle is traveling, A lane recognition unit that recognizes lane information in a traveling direction based on image information from an on-board camera; a curvature calculation unit that calculates curvature information of a travel route based on the lane information; a turning radius calculation unit that calculates a turning radius of the host vehicle based on vehicle speed information from a vehicle speed sensor and steering angle information from a steering angle sensor; an LKAS processing unit that calculates a deviation between a vehicle position and the driving route and calculates a steering angle that brings the vehicle position closer to the driving route; an assist torque calculation unit that calculates a steering assist torque for maintaining the steering angle calculated by the LKAS processing unit; a vehicle control unit that outputs a command to generate the steering assist torque calculated by the assist torque calculation unit to an electric power steering; When lane recognition by the lane recognition unit fails, The LKAS processing unit calculates a steering angle at which the turning radius approaches a curvature based on curvature information stored before the lane recognition failure, The vehicle control device is characterized in that the vehicle control unit outputs a command based on the steering angle calculated by the LKAS processing unit to the electric power steering only within a predetermined period after a lane recognition failure.

2. The vehicle control device according to claim 1, When lane recognition by the lane recognition unit fails, The vehicle control device is characterized in that the assist torque calculation unit calculates a steering assist torque by multiplying the steering assist torque for maintaining the steering angle calculated by the LKAS processing unit by a decreasing coefficient, and outputs the steering assist torque to the vehicle control unit.

3. The vehicle control device according to claim 1, When lane recognition by the lane recognition unit fails, The vehicle control device is characterized in that the vehicle control unit notifies a driver of the release of LKAS processing via an annunciation device.

4. The vehicle control device according to any one of claims 1 to 3, When lane recognition by the lane recognition unit fails, The vehicle control device is characterized in that the curvature calculation unit calculates curvature information of a driving route based on lane information in map information acquired from a GNSS.

5. A vehicle control method for assisting a vehicle in keeping its lane while the vehicle is traveling, comprising: A lane recognition step of recognizing lane information in a traveling direction based on image information from an on-board camera; a curvature calculation step of calculating curvature information of a travel route based on the lane information; a turning radius calculation step of calculating a turning radius of the host vehicle based on vehicle speed information from a vehicle speed sensor and steering angle information from a steering angle sensor; an LKAS processing step of calculating a deviation between the vehicle position and the driving route and calculating a steering angle at which the vehicle position approaches the driving route; an assist torque calculation step of calculating a steering assist torque for maintaining the steering angle calculated in the LKAS processing step; A vehicle control step of outputting a command to generate the steering assist torque calculated in the assist torque calculation step to an electric power steering, When lane recognition in the lane recognition step fails, In the LKAS processing step, a steering angle at which the turning radius approaches a curvature based on curvature information stored before the lane recognition failure is calculated; The vehicle control method is characterized in that, in the vehicle control step, a command based on the steering angle calculated in the LKAS processing step is output to the electric power steering only within a predetermined period after the failure of lane recognition.

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