Vehicle travelling control device and method

This application claims priority to Japanese Patent Application No. 2023-205303 filed on Dec. 5, 2023, incorporated herein by reference in its entirety.

The present disclosure relates to a vehicle traveling control device and a method for a vehicle such as an automobile, and more particularly to a vehicle traveling control device and a method for restraining a vehicle from departing off a road.

A lane departure restraining device is known as a traveling control device for a vehicle such as an automobile. According to the lane departure restraining device, when there is a risk of lane departure of a vehicle, the lane departure of the vehicle is restrained with automatic braking or warning, but when a steering operation is performed by a driver, neither automatic braking nor warning is performed.

For example, Japanese Unexamined Patent Application Publication No. 2009-116693 described below describes a technique for changing a condition for canceling warning according to a driver's alertness level when the driver performs a steering operation in a situation where there is a risk that a vehicle may depart from its lane.

According to this type of lane departure restraining device, when the driver actively tries to cause the vehicle to depart from a lane by performing a steering operation even in a situation where there is a risk that the vehicle may depart from the lane, it is possible to prevent automatic braking and warning from being performed unnecessarily.

Even when a driver performs a steering operation in a situation where there is a risk that a vehicle may depart from the lane, it does not necessarily mean that the driver is actively trying to cause the vehicle to depart from the lane. When the driver is not actively trying to cause the vehicle to depart from the lane, automatic braking and warning may not be canceled even when the driver performs a steering operation.

Especially when there is a risk that the vehicle may depart off a road, by determining whether the direction of the steering operation by the driver is a direction based on a steering operation of causing the vehicle to depart from the road, it is possible to determine whether the driver is actively trying to cause the vehicle to depart from the lane.

The present disclosure provides vehicle traveling control device and method that are improved such that even when a driver performs a steering operation in a situation where there is a risk that a vehicle may depart off a road, the risk of the departure can be reduced if the steering operation is not a steering operation of actively causing the vehicle to depart from a lane.

According to the present disclosure, there is provided a vehicle traveling control device () comprising a steering operation detection device (driving operation sensor) that detects a driver's steering operation, an object information acquisition device () that acquires information on an object around a vehicle (), an automatic braking device () that automatically brakes the vehicle, and a control unit (driving support ECU) that controls the automatic braking device.

The control unit (driving support ECU) is configured to activate the automatic braking device to perform automatic braking for automatically braking the vehicle (S, S) in a case where it is determined based on the information on the object acquired by the object information acquisition device that there is a risk that the vehicle may depart off a road (S) and also determining, based on the steering operation detected by the steering operation detection device, that a steering operation in a direction in which the vehicle departs off the road is performed (S).

Furthermore, according to the present disclosure, there is provided a vehicle traveling control method comprising acquiring information on an object around a vehicle () and determining, based on the acquired information on the object, a risk of departure that the vehicle may depart off a road (S), and activating an automatic braking device to perform automatic braking of automatically braking the vehicle (S, S) when it is determined that there is a risk of departure (S).

The vehicle traveling control method further detects a driver's steering operation, performs no automatic braking (S) when it is determined that the steering operation has been performed in a direction other than a direction in which the vehicle departs off a road (S) even in a case where it is determined that there is a risk of departure (S), and performs automatic braking (S, S, S) when it is determined that there is a risk of departure (S) and it is also determined that the steering operation has been performed in the direction in which the vehicle departs off the road (S).

According to the above-described vehicle traveling control device and method, the information on the object around the vehicle is acquired, and the risk of departure of the vehicle off the road is determined based on the acquired information on the object. Furthermore, automatic braking is performed when it is determined that there is a risk that the vehicle may depart off the road and it is determined that a steering operation in a direction in which the vehicle departs off the road has been performed.

Even in a case where the driver performs a steering operation in a situation where there is a risk that the vehicle may depart off a road, it may be regarded that the steering operation is not a steering operation which is actively tried to control a vehicle traveling direction by the driver when a direction of the steering operation is a direction in which the vehicle is caused to depart off the road. According to the above-described vehicle traveling control device and method, automatic braking is performed in this case, so that the risk that the vehicle departs off the road can be reduced as compared with a case where automatic braking is not performed regardless of a steering direction when a steering operation is performed like a conventional vehicle traveling control device.

Note that the risk of the departure of the vehicle off the road is reduced by automatically braking the vehicle, and an automatic steering operation which counters a driver's steering operation, that is, automatic steering of a steering wheel is not performed. Therefore, even when there occurs a situation in which a direction of departure of the vehicle off the road and/or a direction of the steering operation is not properly determined, an inadequate automatic steering operation caused by the above situation is not performed, so that the traveling direction of the vehicle is not inappropriately controlled.

According to an aspect of the present disclosure, the control unit (driving support ECU) is configured to perform automatic braking (S, S, S) in a case where it is determined that the risk of departure is equal to or more than a first departure reference value (S), and also it is determined that a related value of the steering operation is equal to or more than a first steering reference value (S).

According to the above aspect, automatic braking is performed when it is determined that the risk of departure is equal to or more than the first departure reference value and also it is determined that the related value of the steering operation is equal to or more than the first steering reference value. Therefore, no automatic braking is performed when it is determined that the related value of the steering operation is less than the first steering reference value regardless of determination of the risk of departure being more than the first departure reference value, so that it can be avoided to perform automatic braking unnecessarily.

Note that the related value of the steering operation is an index value for determining whether a steering operation has been performed by the driver, and it may be a steering torque, a steering angle, or the like.

According to another aspect of the present disclosure, the vehicle traveling control device () further comprises a driving state information acquisition device (monitor camera) that acquires information on a driving state of the driver, wherein the control unit (driving support ECU) is configured to determine, based on the driving state information acquired by the driving state information acquisition device, whether the driver's driving state is a distracted driving state (S), when determining that the driver's driving state is not a distracted driving state, the control unit performing automatic braking (S, S, S) in a case where it is determined that the risk of departure is equal to or more than the first departure reference value (S) and also it is determined that the related value of the steering operation is equal to or more than the first steering reference value (S, S), and when determining that the driver's driving state is a distracted driving state, the control unit performing automatic braking in a case where it is determined that the risk of departure is equal to or more than the first departure reference value (S) and also it is determined that the related value of the steering operation is equal to or more than a second steering reference value smaller than the first steering reference value (S, S).

In general, when the driver is in a distracted driving state, the related value of the steering operation is smaller than that when the driver is in an alert state. Therefore, when the driving state of the driver is the distracted driving state, a reference value for determining, based on the related value of the steering operation, whether a steering operation has been performed by a driver may be smaller than that when the driver is in an alert state.

According to the above aspect, in a case where it is determined that the driver's driving state is not a distracted driving state, automatic braking is performed when it is determined that the risk of departure is equal to or more than the first departure reference value and also it is determined that the related value of the steering operation is equal to or more than the first steering reference value. On the other hand, in a case where it is determined that the driver's driving state is a distracted driving state, automatic braking is performed when it is determined that the risk of departure is equal to or more than the first departure reference value and also it is determined that the related value of the steering operation is equal to or more than the second steering reference value smaller than the first steering reference value.

Therefore, as compared with a case where the steering reference value is constant regardless of whether the driver is in a distracted driving state, it is possible to appropriately determine, based on the related value of the steering operation, whether the steering operation has been performed by the driver even in a situation where the driver's driving state is a distracted driving state.

Furthermore, in another aspect of the present disclosure, when performing automatic braking, the control unit (driving support ECU) is configured to perform automatic braking at a first deceleration (S) when it is determined that the risk of departure is less than a second departure reference value larger than the first departure reference value (S, S), and perform automatic braking at a second deceleration higher than the first deceleration (S) when it is determined that the risk of departure is equal to or more than the second departure reference value (S, S).

In general, in order to reduce the risk of off-road departure of the vehicle by automatic braking, the deceleration of the vehicle by automatic braking may be higher as the risk of off-road departure of the vehicle is higher.

According to the above aspect, when it is determined that the risk of departure is less than the second departure reference value larger than the first departure reference value, automatic braking is performed at the first deceleration, and when it is determined that the risk of departure is equal to or more than the second departure reference value, automatic braking is performed at the second deceleration higher than the first deceleration. Therefore, as compared with a case where the deceleration of the vehicle by automatic braking is constant regardless of the degree of the risk of departure, it is possible to appropriately control the deceleration of the vehicle by automatic braking.

In the present application, “off-road” means the side of a non-traveling area with respect to the boundary between a traveling area where vehicles can travel and a non-traveling area where vehicles cannot travel. “Off-road departure” means that a reference position preset for vehicles shifts from the traveling area to the non-traveling area. Lanes on which vehicles travel, roadside strips on which vehicles are allowed to travel, evacuation lanes, etc. may be regarded as traveling areas. On the other hand, areas outside roads, roadside strips on which vehicles are not allowed to travel, etc. may be regarded as non-traveling areas.

In the above description, in order to facilitate understanding of the present disclosure, with respect to configurations of the disclosure corresponding to embodiments described below, names and/or signs to be used in the embodiments are appended in parentheses for the configurations. However, components of the present disclosure are not respectively limited to components of the embodiments corresponding to the names and/or signs appended in parentheses. Other objects, other features, and attendant advantages of the present disclosure will be readily understood from the description of the embodiments of the present disclosure which will be made below with reference to the drawings.

A vehicle traveling control device and a vehicle traveling control method according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

As shown in, a traveling control deviceaccording to an embodiment of the present disclosure is applied to a vehicleand includes a driving support ECU. The vehicleis a vehicle capable of performing autonomous driving, and includes a drive ECU, a braking ECU, an electric power steering ECU, and a meter ECU. ECU means an electronic control unit that includes a microcomputer as a main part. Note that in the following description, electric power steering is referred to as EPS.

The microcomputer of each ECU includes CPU, ROM, RAM, a readable/writable nonvolatile memory (N/M), an interface (I/F), and the like. The CPU implements various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are connected to one another via a controller area network (CAN)such that they can perform data exchange (communication) among them. Therefore, detection values of sensors (including switches) connected to a specific ECU are also transmitted to other ECUs.

The driving support ECUis a central control device that performs traveling control for driving support such as lane departure restraining control and inter-vehicle distance control. In the embodiment, the driving support ECUexecutes the lane departure restraining control in cooperation with other ECUs as described in detail later. The traveling control of the embodiment is executed as a part of the lane departure restraining control.

A camera sensor, a radar sensor, a monitor camera, and a switchare connected to the driving support ECU. The camera sensorand the radar sensoreach include a plurality of camera devices and a plurality of radar devices. The camera sensorand the radar sensorfunction as an object information acquisition devicethat acquires object information around the vehicle.

Although not shown in the figures, each camera device of the camera sensorincludes a camera unit for imaging the surroundings of the vehicle, and a recognizer for analyzing image data obtained through the imaging of the camera unit to recognize white lines on roads and objects such as other vehicles. The recognizer supplies information regarding recognized objects to the driving support ECUat predetermined time intervals.

Each radar device of the radar sensorincludes a radar transceiver and a signal processor (not shown). The radar transceiver emits radio waves in the millimeter wave band (hereinafter referred to as “millimeter waves”), and receives millimeter waves (that is, reflected waves) reflected by three-dimensional objects (for example, other vehicles, bicycles, etc.) existing in a radiation range. Based on the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, and the period of time from transmission of the millimeter waves to reception of the reflected waves, and the like, the signal processor supplies information representing the distances between the own vehicle and three-dimensional objects, the relative speeds between the own vehicle and the three-dimensional objects, the relative positions (directions) of the three-dimensional objects with respect to the own vehicle, etc. to the driving support ECUat predetermined time intervals. Note that light detection and ranging (LiDAR) may be used instead of or in addition to the radar sensor.

The monitor camerais installed on a dashboard or steering column, and includes a camera unit for imaging the driver's face, and an image processor for processing image data of the driver's face obtained through the imaging of the camera unit. The image processor supplies information on the image data of the driver's face to the driving support ECUat predetermined time intervals. Therefore, the monitor camerafunctions as a driver monitor camera.

The CPU of the driving support ECUdetermines a driver's unalertness level based on a driver's eye closing rate per minute, an eye opening status, an eye blinking frequency, an eye movement, etc. based on the information of the image data of the driver's face. The unalertness level is a level indicating a driver's state in which the driver is distracted and unsuitable for driving due to lack of sleep or the like. The method for determining the unalertness level is not particularly limited, and any method known in the art may be adopted. Furthermore, when the unalertness level is determined, at least one of the driver's grip pressure on a steering wheel, press force on an armrest, a heart rate, myoelectric information, and a brain wave pattern may be taken into consideration.

The switchis provided at a position where it can be operated by the driver like a steering wheel (not shown in), and is configured to be operated by the driver. The driving support ECUexecutes the lane departure restraining control when the switchis set to ON as described in detail later.

A drive devicefor accelerating the vehicleby applying driving force to drive wheelsis connected to the drive ECU. The drive ECUnormally controls the drive devicesuch that the driving force generated by the drive devicechanges according to the driving operation by the driver, and upon reception of a command signal from the driving support ECU, the drive ECUcontrols the drive devicebased on the command signal.

A braking devicefor applying braking force to wheelsto decelerate the vehicleby braking is connected to the braking ECU. The braking ECUnormally controls the braking device such that the braking force generated by the braking devicechanges according to the braking operation by the driver, and upon reception of a command signal from the driving support ECU, the braking ECUcontrols the braking devicebased on the command signal, thereby performing automatic braking.

Therefore, the braking ECUand the braking devicecooperate with each other to function together as an automatic braking device. Note that when braking force is applied to the wheels by the lane departure restraining control or the like, a braking lamp (not shown in) is turned on.

An EPS deviceis connected to the EPS ECU. The EPS ECUcontrols a steering assist torque to reduce a steering burden on a driver by controlling the EPS devicein a manner known in the art based on a steering torque Ts and a vehicle speed V detected by a driving operation sensorand a vehicle condition sensordescribed later. Furthermore, the EPS ECUcan turn a steering wheelas necessary by controlling the EPS device. Therefore, the EPS ECUand the EPS devicefunction as an automatic steering device for automatically steering the steering wheel, as necessary.

A touch panel type displayfor displaying a control status, etc. by the driving support ECU, and a warning devicefor issuing an alarm are connected to the meter ECU. The displaymay be, for example, a multi-information display on which meters and various kinds of information are displayed, or may be a display of a navigation device. The displaymay display the status of lane departure restraining control when receiving a signal from the driving support ECU.

The warning deviceis activated when it is determined that there is a risk that the vehiclemay depart off the road, and issues an alarm as one of the lane departure restraining control, that is, issues an alarm indicating that there is a risk that the vehiclemay depart off the road. The warning devicemay be any of a warning device for emitting a visual alarm such as an alarm lamp, a warning device for emitting an audible alarm such as an alarm buzzer, and a warning device for emitting a bodily sensitive alarm such as a vibration of a seat, or it may be any combination of these devices.

The driving operation sensorand the vehicle condition sensorare also connected to the CAN. Information detected by the driving operation sensorand the vehicle condition sensor(referred to as sensor information) is transmitted to the CAN. The sensor information transmitted to the CANcan be used in each ECU as appropriate. Note that the sensor information is information on a sensor connected to a specific ECU, and may be transmitted from the specific ECU to the CAN.

The driving operation sensorincludes a drive operation amount sensor for detecting an operation amount of an accelerator pedal, a braking operation amount sensor for detecting master cylinder pressure or depression force on a brake pedal, and a brake switch for detecting whether the brake pedal is operated. Furthermore, the driving operation sensorincludes a steering angle sensor for detecting a steering angle θ, a steering torque sensor for detecting a steering torque Ts, a turn signal switch for indicating whether a turn signal lever is operated, and a direction of the operation, and the like.

The vehicle condition sensorincludes a vehicle speed sensor for detecting the vehicle speed V of the vehicle, a front-back acceleration sensor for detecting an acceleration in a front-back direction of the vehicle, a lateral acceleration sensor for detecting an acceleration in a lateral direction of the vehicle, and a yaw rate sensor for detecting a yaw rate of the vehicle, and the like.

In a first embodiment, ROM of the driving support ECUstores a lane departure and steering determination control program corresponding to a flowchart shown in. Furthermore, in the first embodiment, the ROM of the driving support ECUstores an automatic braking control program for lane departure restraint corresponding to a flowchart shown in. A traveling control method according to the first embodiment is performed by executing the lane departure and steering determination control and the automatic braking control of the lane departure restraint according to the flowcharts shown in, respectively.

Lane Departure and Steering Determination Control ()

Next, the lane departure and steering determination control in the first embodiment will be described with reference to the flowchart shown in. The lane departure and steering determination control according to the flowchart shown inis repeatedly executed at predetermined time intervals by CPU of the driving support ECUin a situation where the switchis set to ON. Note that a flag F is reset to 0 at the start time of the lane departure and steering determination control.

First, in step S, the CPU determines whether the absolute value of the steering torque Ts is equal to or more than a reference value Tsc, that is, whether the driver is performing a steering operation. If a negative determination is made, the present control proceeds to step S, and if an affirmative determination is made, the present control proceeds to step S. Note that the reference value Tsc may be a positive constant, or may be a positive value that is variably set according to the vehicle speed V such that the reference value Tsc is smaller as the vehicle speed V is higher.