阅读说明：本技术 车用行驶控制装置 (Vehicle travel control device ) 是由 定村哲志 于 2021-03-24 设计创作，主要内容包括：提供了一种车用行驶控制装置,该行驶控制装置包括：被配置成获取车道信息的车道信息获取单元；转向控制单元,该转向控制单元被配置成通过执行车道行驶控制来控制车辆的转向以使车辆沿着车道行驶；以及车速控制单元,该车速控制单元被配置成通过执行定速行驶控制和/或自适应巡航控制来控制车速,在定速行驶控制中使车辆以设定车速行驶,在自适应巡航控制中使车辆以等于或低于设定车速的速度行驶来跟随前车。车速控制单元被配置成通过设定车速上限值在车辆转弯期间控制车速,该车速上限值根据是否正在执行车道行驶控制而被设定为不同的值。(Provided is a travel control device for a vehicle, including: a lane information acquisition unit configured to acquire lane information; a steering control unit configured to control steering of the vehicle to cause the vehicle to travel along the lane by performing lane travel control; and a vehicle speed control unit configured to control a vehicle speed by performing a constant speed running control in which the vehicle is caused to run at a set vehicle speed and/or an adaptive cruise control in which the vehicle is caused to run at a speed equal to or lower than the set vehicle speed to follow a preceding vehicle. The vehicle speed control unit is configured to control the vehicle speed during turning of the vehicle by setting a vehicle speed upper limit value, which is set to a different value depending on whether or not lane travel control is being performed.)

1. A travel control device for a vehicle, the travel control device comprising:

a lane information acquisition unit configured to acquire lane information that is information of a lane in which a vehicle is traveling;

a steering control unit configured to control steering of the vehicle to cause the vehicle to travel along the lane by performing lane travel control; and

a vehicle speed control unit configured to control a vehicle speed by performing constant-speed running control in which the vehicle is caused to run at a set vehicle speed and/or adaptive cruise control in which the vehicle is caused to run at a speed equal to or lower than the set vehicle speed to follow a preceding vehicle,

wherein the vehicle speed control unit is configured to control the vehicle speed during the vehicle turning by setting a vehicle speed upper limit value, and

the vehicle speed upper limit value is set to a different value depending on whether the lane travel control is being executed.

2. The running control apparatus according to claim 1, wherein the vehicle speed control unit sets the vehicle speed upper limit value lower when the lane running control is being executed than when the lane running control is not being executed.

3. The travel control device according to claim 2, wherein the lane information acquisition unit is configured to acquire a curvature of the lane,

the vehicle speed control unit is configured to determine the vehicle speed upper limit value based on a prescribed lateral acceleration limit value, and

the lateral acceleration limit value is set to a larger value as the curvature of the lane becomes larger.

4. The running control apparatus according to claim 3, wherein the vehicle speed control unit sets the lateral acceleration limit value smaller when the lane running control is being executed than when the lane running control is not being executed.

5. The running control apparatus according to claim 3 or 4, wherein the vehicle speed control unit sets a lateral acceleration limit value when the lane running control is being executed to a value smaller than a lateral acceleration limit value when the lane running control is not being executed, for a case where a curvature of the lane is larger than a prescribed curvature.

6. The running control apparatus according to claim 5, wherein the vehicle speed control unit sets a lateral acceleration limit value when the lane running control is being executed to be less than or equal to 3m/s²The value of (c).

7. The running control apparatus according to claim 3 or 4, wherein the vehicle speed control unit sets the lateral acceleration limit value when the lane running control is being executed to the same value as the lateral acceleration limit value when the lane running control is not being executed, for a case where the curvature of the lane is less than or equal to a prescribed curvature.

8. The running control apparatus according to claim 3 or 4, wherein the lane information acquisition unit is configured to acquire a curvature of the lane from a current position of the vehicle on the lane to a future position where the vehicle runs in the future, and

the vehicle speed control unit is configured to limit fluctuation of the vehicle speed upper limit value based on a curvature of the lane at the future position.

9. The running control apparatus according to claim 8, wherein the vehicle speed control unit limits an increase in the upper limit value of the vehicle speed due to the stop of the lane running control, for a case where the lane running control that has been executed is stopped while the vehicle is running on a curvature increase section where a curvature at a future position of the lane is larger than a curvature at a current position.

10. The running control apparatus according to claim 8, wherein the vehicle speed control unit restricts a decrease in the upper limit value of the vehicle speed due to the activation of the lane running control, for a case where the lane running control that has been stopped is activated while the vehicle is running on a curvature-decreasing section having a curvature at a future position of the lane that is smaller than a curvature at a current position.

11. The running control apparatus according to claim 1, wherein the vehicle speed control unit sets the vehicle speed upper limit value higher when the lane running control is being executed than when the lane running control is not being executed.

Technical Field

The present disclosure relates to a vehicle travel control device that controls the steering and the vehicle speed of a vehicle.

Background

In a vehicle control apparatus that performs adaptive cruise control to follow a preceding vehicle, the lateral acceleration of the own vehicle may be controlled to be within a prescribed allowable range to ensure safe running of the vehicle. Specifically, when the lateral acceleration reaches the upper limit of the allowable range, control is performed to limit the vehicle speed. Therefore, if speed limiting is performed during subsequent traveling, the speed of the host vehicle may be controlled to be lower than that of the preceding vehicle so that the inter-vehicle distance between the host vehicle and the preceding vehicle gradually becomes larger, which may cause discomfort to the driver. To avoid this, it has been proposed to provide a vehicle control device configured to allow a larger increase in lateral acceleration on a curve when the vehicle is traveling following a leading vehicle than when the vehicle is not following the leading vehicle (see JP 2018-024360A).

In the vehicle control device described in JP2018-024360A, when the vehicle is traveling following a preceding vehicle, as long as the preceding vehicle is identified, it is allowed to increase the lateral acceleration on a curvature increasing section of the curve. However, when the vehicle speed is controlled to follow the front vehicle by the adaptive cruise control, there are two cases: a case where lane travel control (such as lane keeping assist control) that controls the trajectory (steering) of the host vehicle is executed so that the vehicle travels along a lane; and a case where the lane travel control is not performed (i.e., only the vehicle speed is controlled). The driver may have different feelings from the behavior of the vehicle during turning depending on whether or not the lane travel control is being performed. Therefore, there is a space for improving the vehicle speed control during turning of the vehicle by considering whether the lane travel control is being executed during turning.

Disclosure of Invention

In view of such a background, an object of the present invention is to provide a running control apparatus for a vehicle that can execute appropriate vehicle speed control during turning of the vehicle according to whether or not lane running control is being executed.

Means for accomplishing this task

To achieve the object, one embodiment of the present invention provides a travel control device 1 for a vehicle, including: a lane information acquisition unit 31 configured to acquire lane information that is information of a lane in which the vehicle is traveling; a steering control unit 32 configured to control steering of the vehicle to cause the vehicle to travel along the lane by performing lane travel control LKAS, RDM; and a vehicle speed control unit 33 configured to control a vehicle speed V by executing a constant speed running control CC in which the vehicle is caused to run at a set vehicle speed Vs and/or an adaptive cruise control ACC in which the vehicle is caused to run at a speed equal to or lower than the set vehicle speed to follow a preceding vehicle, wherein the vehicle speed control unit is configured to control the vehicle speed during turning of the vehicle by setting a vehicle speed upper limit value Vm and set the vehicle speed upper limit value to a different value depending on whether or not lane running control is being executed.

According to this configuration, the upper limit value of the vehicle speed during turning of the vehicle is set to different values according to whether or not the road running control is being executed, and therefore, it is possible to execute appropriate vehicle speed control during turning of the vehicle according to whether or not the road running control is being executed.

Preferably, when the lane running control LKAS, RDM is being executed, the vehicle speed control unit 33 sets the vehicle speed upper limit value Vm lower than when the lane running control is not being executed.

According to this configuration, when the steering control unit is performing the lane travel control, the ability to follow (or keep) the lane can be improved. Therefore, it is possible to suppress anxiety that the driver may feel when turning performed by the lane travel control. When the driver performs the steering operation, an increase in the distance to the preceding vehicle due to the vehicle speed limitation can be suppressed, that is, the ability to follow the preceding vehicle provided by the vehicle speed control performed by the vehicle speed control unit can be enhanced, so that the comfort of the driver can be improved.

Preferably, the lane information acquiring unit 31 is configured to acquire the curvature of the lane, and the vehicle speed control unit 33 is configured to determine the vehicle speed upper limit value Vm based on the prescribed lateral acceleration limit values Gm1, Gm2, and set the lateral acceleration limit value to a larger value as the curvature of the lane becomes larger.

According to this configuration, the vehicle speed upper limit value is set based on the lateral acceleration limit value that increases as the curvature of the lane acquired by the lane information acquisition unit becomes larger. Therefore, when the lane travel control is performed by the steering control unit, the vehicle can be turned without excessively reducing the vehicle speed. Therefore, comfortable and highly convenient vehicle speed control can be performed within a range tolerable by the occupant.

Preferably, when the lane running control LKAS, RDM is being executed, the vehicle speed control unit 33 sets the lateral acceleration limit values Gm1, Gm2 to be smaller than when the lane running control is not being executed.

According to this configuration, the ability to follow the lane can be improved. Therefore, the occupant can feel easy when the vehicle turns under the lane travel control. When the driver performs the steering operation, an increase in the distance to the preceding vehicle due to the vehicle speed limitation can be suppressed, that is, the ability to follow the preceding vehicle provided by the vehicle speed control performed by the vehicle speed control unit can be enhanced.

Preferably, the vehicle speed control unit 33 sets the lateral acceleration limit value Gm2 when the lane travel control LKAS, RDM is being executed to a value smaller than the lateral acceleration limit value Gm1 when the lane travel control is not being executed, for a case where the curvature of the lane is larger than the prescribed curvature.

According to this configuration, the lateral acceleration limit value when the lane travel control is being performed is set small for a case where the curvature of the lane is larger than the prescribed curvature, whereby it is possible to suppress anxiety that the occupant may feel.

Preferably, the vehicle speed control unit 33 sets the lateral acceleration limit value Gm2 to be less than or equal to 3m/s while lane travel control LKAS, RDM is being performed²The value of (c).

According to this configuration, the lateral acceleration during execution of the lane travel control (during which the attention of the occupant to the steering operation is relatively low) is maintained to not more than 3m/s²This ensures that the anxiety of the occupant due to the lateral acceleration can be suppressed.

Preferably, the vehicle speed control unit 33 sets the lateral acceleration limit value Gm2 when the lane travel control LKAS, RDM is being executed to the same value as the lateral acceleration limit value Gm1 when the lane travel control is not being executed, for a case where the curvature of the lane is less than or equal to the prescribed curvature.

According to this configuration, it is possible to prevent an excessive decrease in the vehicle speed, which would deteriorate the convenience and comfort of the vehicle speed control, for the case where the curvature is less than or equal to the prescribed curvature.

Preferably, the lane information acquiring unit 31 is configured to acquire a curvature of a lane from a current position of the vehicle on the lane to a future position where the vehicle will travel in the future, and the vehicle speed control unit 33 is configured to limit the fluctuation of the vehicle speed upper limit value Vm based on the curvature of the lane at the future position.

According to this configuration, by limiting the fluctuation of the vehicle speed upper limit value based on the curvature at the future position, it is possible to suppress frequent fluctuation of the vehicle speed upper limit value. Thereby, it is possible to suppress discomfort that the occupant may feel, which improves the marketability of the vehicle equipped with the running control apparatus.

Preferably, the vehicle speed control unit 33 limits an increase in the vehicle speed upper limit value Vm due to the stop of the lane travel control, for a case where the already-executed lane travel control LKAS, RDM is stopped while the vehicle is traveling on a curvature increase section where the curvature at the future position of the lane is larger than the curvature at the current position.

According to this configuration, since the vehicle speed control unit limits the increase of the upper limit value of the vehicle speed (and thus the increase of the vehicle speed) in the above situation, undesired acceleration of the vehicle before deceleration is prevented, so that the marketability of the vehicle can be improved.

Preferably, the vehicle speed control unit 33 limits the decrease of the vehicle speed upper limit value Vm due to the activation of the lane travel control, for a case where the already stopped lane travel control LKAS, RDM is activated while the vehicle is traveling on a curvature decrease section where the curvature at the future position of the lane is smaller than the curvature at the current position.

According to this configuration, since the vehicle speed control unit limits the reduction of the upper limit value of the vehicle speed (and thus the reduction of the vehicle speed) in the above situation, undesired deceleration of the vehicle before acceleration is prevented, so that the marketability of the vehicle can be improved.

Preferably, when the lane running control LKAS, RDM is being executed, the vehicle speed control unit 33 sets the vehicle speed upper limit value Vm higher than when the lane running control is not being executed.

According to this configuration, when the lane travel control is being performed, the ability to follow the preceding vehicle can be improved. Further, when the driver performs the steering operation, the vehicle speed is limited at a lower vehicle speed upper limit value than when the lane travel control is being performed by the steering control unit, thereby reducing the burden on the driver to perform the steering operation.

Therefore, according to the present invention, it is possible to provide a running control apparatus for a vehicle that can perform appropriate vehicle speed control during turning of the vehicle according to whether or not lane running control is being performed.

Drawings

Fig. 1 is a functional configuration diagram of a vehicle mounted with a running control apparatus according to an embodiment of the invention;

fig. 2 is a flowchart of vehicle speed control executed by the running control apparatus according to the embodiment;

FIG. 3 is a flowchart of a first curve vehicle speed control of the vehicle speed control shown in FIG. 2;

FIG. 4 is a flowchart of a second curve vehicle speed control of the vehicle speed control shown in FIG. 2;

FIG. 5 is a graph showing the relationship between the radius of curvature of the lane and the lateral acceleration limit value;

FIG. 6 is an operation explanatory diagram of vehicle speed control according to the embodiment;

FIG. 7 is an operation explanatory diagram of vehicle speed control according to the embodiment;

FIG. 8 is an operation explanatory diagram of vehicle speed control according to the embodiment;

FIG. 9 is an operation explanatory diagram of vehicle speed control according to the embodiment;

FIG. 10 is an operation explanatory diagram of vehicle speed control according to the embodiment;

FIG. 11 is an operation explanatory diagram of vehicle speed control according to the embodiment; and

fig. 12 is an operation explanatory diagram of vehicle speed control according to the embodiment.

Detailed Description

Next, an embodiment of the travel control device 1 according to the present invention will be described with reference to the drawings.

As shown in fig. 1, a running control apparatus 1 is mounted in a vehicle constituted by a four-wheeled automobile, and constitutes a part of a vehicle system 2. The vehicle system 2 includes: a powertrain 3, a brake device 4, a steering device 5, an external environment detection device 6, a vehicle sensor 7, a communication device 8, a navigation device 9 (map device), a driving operation device 10, a notification device 11, an ACC switch 12, an LKAS switch 13, and a control device 15. The above-described components of the vehicle system 2 are connected to each other so that signals CAN be transmitted therebetween via a communication device such as a Controller Area Network (CAN). In the present embodiment, the control device 15 specifically implements the travel control device 1.

The powertrain 3 is a device configured to apply driving force to the vehicle. The power train 3 includes, for example, a power source and a transmission. The power source includes at least one of an internal combustion engine such as a gasoline engine and a diesel engine, and an electric motor. The brake device 4 is a device configured to apply a braking force to the vehicle. For example, the brake device 4 includes: a brake caliper configured to press a brake pad against a brake rotor; and an electric cylinder configured to supply oil pressure to the caliper. The steering device 5 is a device that changes the steering angle of the wheels. For example, the steering device 5 includes: a rack and pinion mechanism configured to steer (turn) wheels; and a motor configured to drive the rack and pinion mechanism. The drive train 3, the brake device 4 and the steering device 5 are controlled by a control device 15.

The external environment detection device 6 is a device that detects an object or the like outside the vehicle. The external environment detection device 6 includes a sensor that detects electromagnetic waves such as visible light from the vehicle surroundings to detect an object or the like outside the vehicle. Such sensors may include, for example: one or more radars 17, one or more lidar (lidar)18, and one or more external cameras 19. Further, the external environment detection device 6 may include a device configured to receive a signal from outside the vehicle and detect an object outside the vehicle based on the received signal. The external environment detection device 6 outputs the detection result to the control device 15.

Each radar 17 emits radio waves such as millimeter waves to the vehicle surroundings, and captures radio waves reflected by objects around the vehicle, thereby detecting the position (distance and direction) of the object. The respective radar 17 may be mounted at any suitable location on the vehicle. The one or more radars 17 include at least one front radar configured to emit radio waves in a forward direction of the vehicle. Each laser radar 18 emits light such as infrared light to the vehicle surroundings, and captures light reflected by an object around the vehicle, thereby detecting the position (distance and direction) of the object. Each lidar 18 may be mounted at any suitable location on the vehicle.

The one or more external cameras 19 are arranged to capture images of the vehicle surroundings to detect objects around the vehicle, for example nearby vehicles and pedestrians, guardrails, curbs, walls, intermediate road strips, and road markings used on road surfaces conveying various information, such as lane boundaries and road shape. Each external camera 19 may be composed of, for example, a digital camera using a solid-state imaging element such as a CCD or a CMOS. Each external camera 19 may be mounted at any suitable location on the vehicle. The one or more external cameras 19 include at least a front camera that captures images in front of the vehicle. Preferably, said one or more external cameras 19 further comprise: a rear camera configured to capture an image behind the vehicle; and a pair of side cameras configured to capture images of the left and right sides of the vehicle. Each external camera 19 may be, for example, a stereo camera.

The vehicle sensor 7 includes: a vehicle speed sensor 20 configured to detect a vehicle speed; a lateral acceleration sensor 21 configured to detect a lateral acceleration G of the vehicle; a yaw rate sensor (not shown) configured to detect an angular velocity about a vertical axis of the vehicle; and a direction sensor (not shown) configured to detect a direction of the vehicle.

The communication device 8 enables the control device 15 to communicate with the navigation device 9, the vehicles present around the host vehicle, and/or an external server. The control device 15 can perform wireless communication with the vehicles around the host vehicle via the communication device 8. Further, the control device 15 may communicate with a server that provides map information, traffic control information, and the like via the communication device 8.

The navigation device 9 is a device configured to acquire a current position of the vehicle and provide route guidance to a destination or the like while displaying the current position on a map. The navigation device 9 includes: the device comprises a GNSS receiving unit, a map storage unit, a navigation interface, a route determining unit and the like. The GNSS receiving unit identifies the position (latitude and longitude) of the vehicle based on a signal received from a satellite (positioning satellite). The map storage unit is composed of a known storage device such as a flash memory or a hard disk, and stores map information.

The map information preferably includes: road types (such as expressways, toll roads, national roads, and county roads), the number of lanes of each road, the center position of each lane (three-dimensional coordinates including longitude, latitude, and height), and lane shape information (including width, curvature (radius of curvature R)), of each lane. Note that the map storage unit may be configured as a part of the control device 15, or as a part of a server device that can communicate with the map storage unit via the communication device 8. Also, the map information may include traffic control information, traffic congestion information, and the like acquired via the communication device 8. Here, the curvature indicates the degree of bending, and for example, the smaller the curvature radius of the curve, the larger the curvature of the lane.

The driving operation device 10 is configured to receive an input operation performed by a driver to control the vehicle. The driving operation device 10 includes, for example: a steering wheel, an accelerator pedal, and a brake pedal. The steering operation device 10 may further include a shift lever, a parking brake lever, and the like. Each of these operation members included in the driving operation device 10 is provided with a sensor that detects an operation amount of the operation member. The driving operation device 10 outputs a signal indicating the operation amount of the corresponding operation member to the control device 15.

The notification device 11 is configured to notify a vehicle occupant (such as a driver) of various information by display and/or voice. The notification device 11 includes, for example, a touch panel display, a speaker, and the like. In another embodiment, the notification means 11 may be configured as part of the navigation means 9.

The ACC switch 12 is a switch configured to receive an instruction relating to a vehicle speed V from an occupant regarding automated driving, and includes a main switch 22, a vehicle speed setting switch 23, and a vehicle distance setting switch 24. The main switch 22 is configured to receive an instruction to start or stop Adaptive Cruise Control (ACC) from an occupant. In the adaptive cruise control, a vehicle (own vehicle) is controlled to travel at a speed equal to or lower than a set vehicle speed Vs so as to follow a preceding vehicle traveling ahead of the own vehicle in the same lane. The vehicle speed setting switch 23 is configured to receive an input of a set vehicle speed Vs from the occupant. During the adaptive cruise control, the set vehicle speed Vs is used as an upper limit value of the vehicle speed V. The vehicle distance setting switch 24 is configured to receive an input of the set vehicle distance Ds from the occupant. The set vehicle distance Ds is a minimum vehicle distance between the host vehicle and the preceding vehicle during the adaptive cruise control.

The LKAS switch 13 is a switch configured to receive a command related to steering of the vehicle regarding automated driving from an occupant, and is specifically configured to receive a command to activate (start) or deactivate a Lane Keeping Assist System (LKAS) from the occupant. The LKAS, when enabled, performs lane travel control to cause the vehicle to travel along the lane.

The ACC switch 12 and the LKAS switch 13 may each be composed of a mechanical switch or a Graphical User Interface (GUI) switch displayed on a touch panel, and are provided at appropriate positions in the vehicle cabin. The ACC switch 12 may be configured as a part of an input interface or a navigation interface of the notification apparatus 11.

The control device 15 is composed of an Electronic Control Unit (ECU) including a CPU, a nonvolatile memory such as a ROM, a volatile memory such as a RAM, and the like. The CPU executes operation processing according to a program to cause the control device 15 to execute various types of vehicle control. The control device 15 may be composed of one piece of hardware, or may be composed of a unit including a plurality of pieces of hardware.

The control device 15 includes: an external environment recognition unit 31, a steering control unit 32, a vehicle speed control unit 33, and a notification control unit 34. The external environment recognition unit 31 includes a lane recognition unit 35. The external environment recognition unit 31 recognizes an obstacle, a road shape, a presence or absence of a pedestrian, a road sign, and the like around the vehicle based on the detection result of the external environment detection device 6. Specifically, the lane recognition unit 35 of the external environment recognition unit 31 recognizes a lane in which the vehicle is traveling from the image captured by the external camera 19 or the like, and acquires lane information indicating the shape of the recognized lane. The steering control unit 32 controls steering of the vehicle via the steering device 5 to perform lane keeping assist control. The vehicle speed control unit 33 controls the vehicle speed V via the powertrain 3 and the brake device 4 to perform the adaptive cruise control. The notification control unit 34 controls the notification operation of the notification device 11.

The control device 15 performs at least level 1 automated driving control (which may be hereinafter simply referred to as automated driving) by combining various vehicle controls including lane keeping assist control and adaptive cruise control. The automated driving level is based on the definition of SAE J3016 (trademark), and is defined with respect to the degree of intervention of the driver in the driving operation and the monitoring of the vehicle surroundings.

In the level 0 automated driving (i.e., manual driving), the control device 15 does not control the vehicle, and the driver performs all driving operations. That is, the powertrain 3, the brake device 4, the steering device 5, and the like are operated in accordance with the input of the driver to the driving operation device 10. Also, it should be noted that in the manual driving, the drive control of the powertrain 3 according to the depression amount of the accelerator pedal, and the drive control of the steering device 5 according to the input torque of the steering wheel (steering torque) are performed by the control device 15 to generate the steering assist force.

In the level 1 automated driving, the control device 15 performs a part of the driving operations, and the driver performs the remaining driving operations. For example, level 1 automated driving includes: constant speed running control, Adaptive Cruise Control (ACC), and lane keeping assist control (LKAS). That is, in the level 1 automated driving, the control device 15 performs steering, acceleration, and deceleration of the vehicle.

In the present embodiment, when receiving an instruction to execute the adaptive cruise control via the ACC switch 12, the vehicle speed control unit 33 executes the adaptive cruise control to control the vehicle speed V so that the vehicle travels at a speed equal to or lower than the set vehicle speed Vs, thereby following the preceding vehicle.

In another embodiment, instead of or together with the ACC switch 12, a Cruise Control (CC) switch may be provided so that, upon receiving a cruise control execution instruction, the vehicle speed control unit 33 executes a constant speed running control to control the vehicle speed V so that the vehicle runs at the set vehicle speed Vs. The adaptive cruise control and the constant speed running control are vehicle speed controls that adaptively control the vehicle speed V according to the lane information. The vehicle speed control unit 33 may have any configuration as long as the configuration can perform such adaptive vehicle speed control.

Here, the lane information includes information on the shape of a lane in which the vehicle is traveling (this may be referred to as a own lane or a traveling lane hereinafter), such as whether the lane is straight or curved, and lane curvatures at respective points of a plurality of points on the lane ahead of the vehicle. A straight lane is, for example, a lane with a radius of curvature R greater than or equal to 2000m, while a curved lane is, for example, a lane with a radius of curvature R less than 2000 m. "each point on the lane" refers to each of the current position of the vehicle, a future position at which the vehicle will travel in the future (e.g., after a prescribed time), and a plurality of positions between the current position and the future position. In the present embodiment, the future position is a position where the vehicle will travel 10 seconds later. In another embodiment, the future location may be a location where the vehicle will travel 2 seconds later, a location a defined distance ahead of the host vehicle (e.g., 200m ahead), or the like.

In the present embodiment, when receiving an instruction to perform lane keeping assist control via the LKAS switch 13, the steering control unit 32 performs lane keeping control to control steering of the vehicle via the steering device 5 so that the vehicle travels along the lane (own lane) recognized by the external environment recognition unit 31. The lane recognized by the external environment recognition unit 31 may be a lane recognized by the lane recognition unit 35 from a forward image captured by the external camera 19. Alternatively or additionally, the external environment recognition unit 31 may acquire information of the own lane from the navigation device 9 or from the outside of the vehicle via the communication device 8.

In another embodiment, a road deviation suppression (RDM) switch may be provided instead of or in addition to the LKAS switch 13, so that when an RDM execution instruction is received via the RDM switch, the steering control unit 32 executes road deviation suppression control to control steering of the vehicle via the steering device 5 so that the vehicle is prevented from leaving the road (or lane). It is only necessary for the steering control unit 32 to execute at least one of lane keeping assist control or road deviation suppression control, each of which controls the steering of the vehicle, as lane travel control.

Next, a process of vehicle speed control performed by the vehicle speed control unit 33 of the control device 15 will be described with reference to fig. 2. When receiving an instruction to execute the adaptive cruise control from the ACC switch 12, the vehicle speed control unit 33 starts the vehicle speed control shown in fig. 2.

First, the vehicle speed control unit 33 starts acquiring ACC information (step ST 1). The ACC information includes a set vehicle speed Vs and a set vehicle distance Ds. The set vehicle speed Vs may be, for example, a value set or changed via the vehicle speed setting switch 23 or a value of the actual vehicle speed Va upon receiving an instruction to execute the adaptive cruise control from the main switch 22, which may be selected depending on the situation. Further, the vehicle speed control unit 33 starts acquiring the lane information (step ST 2). The lane information includes the aforementioned shape of the traveling lane in front of the vehicle. The acquisition of the ACC information and the lane information in step ST1 and step ST2 is performed continuously from time to time.

Next, the vehicle speed control unit 33 determines whether the driving lane is straight (step ST 3). It is determined whether the traveling lane is straight based on both the curvature radius Rp at the current position and the curvature radius Rf at the future position. For example, if the curvature radius Rp at the current position and the curvature radius Rf at the future position are both greater than or equal to 2000m, it is determined that the lane is straight, and otherwise it is determined that the lane is curved.

If it is determined that the traveling lane is straight (ST 3: YES), the vehicle speed control unit 33 sets the set vehicle speed Vs to the target vehicle speed Vt (step ST 4). The vehicle speed control unit 33 determines in step ST5 whether the ACC is turned off, that is, whether an instruction to stop the adaptive cruise control is received from the ACC switch 12, and if the ACC is not turned off (ST 5: no), the vehicle speed control unit 33 repeats the processing from step ST 3. If the ACC has been turned off (ST 5: YES), the vehicle speed control unit 33 ends the vehicle speed control.

If it is determined in step ST3 that the traveling lane is not straight (ST 3: NO), the vehicle speed control unit 33 determines whether or not LKAS is turned off, that is, whether or not the lane traveling control is in a non-execution state (step ST 6). If the LKAS has been turned off (ST 6: YES), the vehicle speed control unit 33 performs a first curve vehicle speed control (step ST7), and if the LKAS has been turned on (ST 6: NO), the vehicle speed control unit 33 performs a second curve vehicle speed control (step ST 8). The first curve vehicle speed control and the second curve vehicle speed control will be described in detail with reference to fig. 3 and 4.

In the first curve vehicle speed control, the vehicle speed control unit 33 executes the process shown in fig. 3. First, the vehicle speed control unit 33 acquires the vehicle speed upper limit value Vm from the first table (step ST 11). Note that, in the second curve vehicle speed control shown in fig. 4, the vehicle speed control unit 33 first acquires the vehicle speed upper limit value Vm from the second table (step ST 31). The vehicle speed upper limit value Vm set in the first table and the vehicle speed upper limit value Vm set in the second table are determined based on the LKAS off lateral acceleration limit value Gm1 set in the first table and the LKAS on lateral acceleration limit value Gm2 described below, respectively.

Fig. 5 shows the LKAS closing lateral acceleration limit Gm1 set in the first table and the LKAS opening lateral acceleration limit Gm2 set in the second table. These two lateral acceleration limit values Gm (Gm1, Gm2) are set to increase as the curvature radius R of the traveling lane becomes smaller (i.e., as the curvature of the lane becomes larger).

This is because, when the vehicle is running along a sharp curve with a small radius of curvature R, the occupant can tolerate the lateral acceleration G even if the lateral acceleration G increases to a relatively large value. In other words, if the vehicle speed V is reduced to reduce the lateral acceleration G, the occupant is likely to feel uneasy, and the convenience of the vehicle speed control is reduced. Therefore, the setting is made such that a larger lateral acceleration G is allowed when the vehicle travels along a sharp curve having a smaller radius of curvature R than when the vehicle travels along a gentle curve having a larger radius of curvature R, thereby enhancing the convenience of vehicle speed control.

When the LKAS is on, an upper limit value of the lateral acceleration G is set (Gul). The LKAS opening lateral acceleration upper limit value Gul is set to have a constant magnitude regardless of the magnitude of the radius of curvature R. As for the curvature radius R being smaller than the prescribed value Rth, the LKAS-on lateral acceleration upper limit Gm2 is set to the LKAS-on lateral acceleration upper limit Gul, whereby the LKAS-on lateral acceleration limit Gm2 is smaller than the LKAS-off lateral acceleration limit Gm 1.

For example, LKAS opening lateral acceleration upper limit Gul may be set to 3m/s². Thus, the LKAS opening lateral acceleration limit Gm2 is set to be less than or equal to 3m/s for any curve having any curvature radius R²The value of (c). The LKAS opening lateral acceleration limit value Gm2 is set to the same value as the LKAS closing lateral acceleration limit value Gm1 for a radius of curvature R greater than or equal to a predetermined value Rth.

The vehicle speed upper limit Vm is set in the first table and the second table, respectively, based on the lateral acceleration limit values Gm1, Gm2 set as described above. Each of the first table and the second table takes the form of a map in which the vehicle speed upper limit value Vm is set in accordance with the magnitude of the curvature radius R.

Therefore, mutually different lateral acceleration limit values Gm (Gm1, Gm2) are set in the first table and the second table in accordance with the curvature radius R of the traveling lane, and a vehicle speed upper limit value Vm is set in each of the first table and the second table in accordance with the corresponding lateral acceleration limit value Gm (Gm1, Gm 2). That is, the vehicle speed upper limit value Vm is set to mutually different values in the first table and the second table, and one of the first table and the second table is referred to in accordance with the determination in step ST6 of fig. 2, thereby setting the vehicle speed upper limit value Vm to a different value in accordance with whether or not lane travel control (LKAS) is being performed. Specifically, the vehicle speed upper limit value Vm is set lower in the second table that is referred to when the lane travel control is being executed than in the first table that is referred to when the lane travel control is not being executed.

For example, the vehicle speed upper limit value Vm is a value used as a target vehicle speed Vt that decelerates the vehicle when the vehicle enters a curve. Therefore, when the vehicle enters a curve, the vehicle speed upper limit value Vm is set by using the minimum value of the curvature radius R from the current position to the future position, that is, the curvature radius Rf at the future position, so that sufficient deceleration is achieved by the time when the vehicle enters the curve. Also, in the case where the vehicle is advancing from a curve to a straight lane, if the curvature radius Rf at the future position is used to set the vehicle speed upper limit value Vm, it may cause the vehicle to run at an excessive speed at the current position. Therefore, when the vehicle also travels along the curvature decreasing section, the minimum value of the curvature radius R from the current position to the future position (in this case, the curvature radius Rp at the current position) is used.

Referring again to fig. 3, after acquiring the vehicle speed upper limit value Vm from the first table in step ST11, the vehicle speed control unit 33 determines whether the set vehicle speed Vs is lower than or equal to the vehicle speed upper limit value Vm (step ST 12). If the set vehicle speed Vs is lower than or equal to the vehicle speed upper limit value Vm (step ST 12: YES), the vehicle speed control unit 33 sets the set vehicle speed Vs to the target vehicle speed Vt, and performs vehicle speed control (step ST 13). If the set vehicle speed Vs is higher than the vehicle speed upper limit Vm (step ST 12: NO), the vehicle speed control unit 33 sets the vehicle speed upper limit Vm to the target vehicle speed Vt, and performs vehicle speed control (step ST 14).

Subsequently, the vehicle speed control unit 33 determines in step ST15 whether LKAS is off, that is, whether a state in which a command to perform the lane keeping assist control is not input from the LKAS switch 13 is continued. If the LKAS is still kept closed (ST 15: Yes), the vehicle speed control unit 33 determines whether the driving lane is straight (step ST 16). If the traveling lane is straight (ST 16: YES), the vehicle speed control unit 33 ends the first curve vehicle speed control and proceeds to step ST4 of FIG 2.

If a command to perform lane keeping assist control is received from the LKAS switch 13, and it is thus determined in step ST15 to turn on LKAS (ST 15: no), the vehicle speed control unit 33 determines whether the curvature radius Rf at a future position is smaller than a prescribed value Rth (step ST 17). This determination is made in order to determine whether the driving lane is curved with a large curvature so that it is necessary to limit the LKAS-on lateral acceleration limit Gm2 to a value smaller than the LKAS-off lateral acceleration limit Gm1, as shown in fig. 5.

If the curvature radius Rf at the future position is greater than or equal to the prescribed value Rth (ST 17: NO), the vehicle speed control unit 33 proceeds to the second curve vehicle speed control in FIG. 2 (step ST 8). In the case where the curvature radius Rf at the future position is smaller than the prescribed value Rth (ST 17: YES), the vehicle speed control unit 33 determines whether the vehicle is traveling on the curvature-reduced section of the curve (step ST 18). It is determined whether the vehicle is traveling on the curvature-reduced section based on the curvature radius Rp at the current position and the curvature radius Rf at the future position. Specifically, when the curvature radius Rf at the future position is larger than the curvature radius Rp at the current position, it is determined that the vehicle is traveling on the curvature-reduced section. Conversely, when the curvature radius Rf at the future position is smaller than the curvature radius Rp at the current position, it is determined that the vehicle is traveling on the curvature increasing section of the curve. Further, when the curvature radii Rf, Rp are the same, the curvature constant section where the vehicle is traveling on the curve is determined.

If it is determined in step ST18 that the vehicle is not traveling the curvature decreasing road section of the lane (ST 18: NO), the vehicle speed control unit 33 proceeds to the second curve vehicle speed control in FIG 2 (step ST 8). If it is determined in step ST18 that the vehicle is traveling on the curvature decreasing section of the lane (ST 18: YES), the vehicle speed control unit 33 maintains the value of the target vehicle speed Vt (step ST 19). Then, the vehicle speed control unit 33 acquires the vehicle speed upper limit value Vm from the second table (step ST20), and determines whether the vehicle speed upper limit value Vm matches the actual vehicle speed Va (step ST 21). The vehicle speed control unit 33 repeats the processing from step ST19 until the result of the determination in step ST21 is yes. If the vehicle speed upper limit value Vm obtained from the second table increases to such an extent that the vehicle speed upper limit value Vm matches the actual vehicle speed Va as the curvature of the traveling lane decreases (ST 21: YES), the vehicle speed control unit 33 proceeds to the second curve vehicle speed control in FIG 2 (step ST 8).

In this way, when the LKAS is turned on (ST 15: no), if the curvature radius Rf at the future position is larger than the curvature radius Rp at the current position (ST 18: yes), the vehicle speed control unit 33 does not immediately use the vehicle speed upper limit value Vm acquired from the second table, which is smaller in value than the vehicle speed upper limit value Vm acquired from the first table, but limits the decrease of the target vehicle speed Vt (or maintains the target vehicle speed Vt) until the vehicle speed upper limit value Vm acquired from the second table is increased to make the determination result of step ST21 yes.

Next, the second curve vehicle speed control will be described with reference to fig. 4. As mentioned above, the vehicle speed control unit 33 first acquires the vehicle speed upper limit value Vm from the second table (step ST 31). Thereafter, the vehicle speed control unit 33 determines whether the set vehicle speed Vs is lower than or equal to a vehicle speed upper limit Vm (step ST 32). If the set vehicle speed Vs is lower than or equal to the vehicle speed upper limit value Vm (step ST 32: YES), the vehicle speed control unit 33 sets the set vehicle speed Vs to the target vehicle speed Vt, and performs vehicle speed control (step ST 33). If the set vehicle speed Vs is higher than the vehicle speed upper limit Vm (step ST 32: NO), the vehicle speed control unit 33 sets the vehicle speed upper limit Vm to the target vehicle speed Vt, and performs vehicle speed control (step ST 34).

Subsequently, the vehicle speed control unit 33 determines in step ST35 whether LKAS is on, that is, a state in which a command to stop the lane keeping assist control is not input from the LKAS switch 13 is continued. If LKAS is still kept on (ST 35: Yes), the vehicle speed control unit 33 determines whether the driving lane is straight (step ST 36). If the traveling lane is straight (ST 36: YES), the vehicle speed control unit 33 ends the second curve vehicle speed control and proceeds to step ST4 of FIG 2.

If a command to stop the lane keeping assist control is received from the LKAS switch 13, and thus it is determined in step ST35 to turn off the LKAS (ST 35: no), the vehicle speed control unit 33 determines whether the curvature radius Rf at a future position is smaller than a prescribed value Rth (step ST 37). This determination is made in order to determine whether the driving lane is curved with a large curvature so that it is necessary to limit the LKAS-on lateral acceleration limit Gm2 to a value smaller than the LKAS-off lateral acceleration limit Gm1, as shown in fig. 5.

If the curvature radius Rf at the future position is greater than or equal to the prescribed value Rth (ST 37: NO), the vehicle speed control unit 33 proceeds to the first curve vehicle speed control in FIG. 2 (step ST 7). In the case where the curvature radius Rf at the future position is smaller than the prescribed value Rth (ST 37: YES), the vehicle speed control unit 33 determines whether the vehicle is traveling on the curvature increased section of the curve (step ST 38). As described above, it is determined whether the vehicle is traveling on the increased curvature section based on the curvature radius Rp at the current position and the curvature radius Rf at the future position.

If it is determined in step ST38 that the vehicle is not traveling the curvature increasing section of the lane (ST 38: NO), the vehicle speed control unit 33 proceeds to the first curve vehicle speed control in FIG 2 (step ST 7). If it is determined in step ST38 that the vehicle is traveling in the curvature increasing section of the lane (ST 38: YES), the vehicle speed control unit 33 maintains the value of the target vehicle speed Vt (step ST 39). Then, the vehicle speed control unit 33 acquires the vehicle speed upper limit value Vm from the first table (step ST40), and determines whether the vehicle speed upper limit value Vm matches the actual vehicle speed Va (step ST 41). The vehicle speed control unit 33 repeats the processing from step ST39 until the result of the determination in step ST41 is yes. If the vehicle speed upper limit value Vm obtained from the second table decreases to the extent that the vehicle speed upper limit value Vm matches the actual vehicle speed Va as the curvature of the traveling lane increases (ST 41: YES), the vehicle speed control unit 33 proceeds to the first curve vehicle speed control in FIG 2 (step ST 7).

In this way, the LKAS is turned off (ST 35: no), if the curvature radius Rf at the future position is smaller than the curvature radius Rp at the current position (ST 38: yes), the vehicle speed control unit 33 does not immediately use the vehicle speed upper limit value Vm obtained from the first table, which is higher in value than the vehicle speed upper limit value Vm obtained from the second table, but limits the increase of the target vehicle speed Vt until the vehicle speed upper limit value Vm obtained from the first table is decreased to make the determination result of step ST41 yes.

Therefore, by performing the processing from step ST18 to step ST21 of fig. 3 and the processing from step ST38 to step ST41 of fig. 4, the vehicle speed control unit 33 limits the fluctuation of the vehicle speed upper limit value Vm based on the curvature radius Rf at the future position. Thereby, discomfort that the occupant may feel due to frequent fluctuations of the vehicle speed upper limit value Vm can be suppressed, and the marketability of the vehicle equipped with the running control apparatus 1 can be improved. This will be described in more detail later with reference to specific examples.

The vehicle speed control unit 33 executes vehicle speed control according to the above-described processing.

Next, the behavior of the vehicle under the vehicle speed control performed by the vehicle speed control unit 33 as described above will be described with reference to fig. 6 to 12. Fig. 6 to 12 show various driving situations of the vehicle.

Fig. 6 shows the situation in which the vehicle enters a curve with LKAS on. In this case, as the vehicle advances, the maximum curvature increases (the curvature radius R decreases) from the current position to the future position (in this example, the point 10 seconds after the vehicle will travel). Thus, as the vehicle advances, the target lateral acceleration Gt limited by the LKAS-on lateral acceleration limit value Gm2 acquired from the second table increases, while the target vehicle speed Vt limited by the vehicle speed upper limit value Vm decreases. The actual lateral acceleration Ga increases following the target lateral acceleration Gt, while the actual vehicle speed Va decreases following the target vehicle speed Vt. The changes in the target lateral acceleration Gt and the target vehicle speed Vt end at a point P1 located before the start point of the curvature constant section where the maximum curvature is constant from the current position to the future position, and thereafter, the target lateral acceleration Gt and the target vehicle speed Vt have constant values.

Fig. 7 shows the situation in which the vehicle enters a curve with LKAS off. In this case, as the vehicle advances, the maximum curvature from the current position to the future position increases (the minimum curvature radius R decreases). Thus, the target lateral acceleration Gt limited by the LKAS closing lateral acceleration limit value Gm1 acquired from the first table increases more than in the case of fig. 6, while the target vehicle speed Vt limited by the vehicle speed upper limit value Vm decreases at a smaller deceleration than in the case of fig. 6. As in the case of fig. 6, the actual lateral acceleration Ga increases following the target lateral acceleration Gt, the actual vehicle speed Va decreases following the target vehicle speed Vt, and the changes in the target lateral acceleration Gt and the target vehicle speed Vt end at the point P1.

Fig. 8 shows the situation in which the vehicle enters a curve with LKAS off and LKAS is open at the curvature increasing section. In this case, as the vehicle advances, the maximum curvature from the current position to the future position increases (the curvature radius R decreases). At the point P2 where LKAS is on, the target lateral acceleration Gt is reduced in a stepwise manner by switching from the value limited in accordance with the LKAS closing lateral acceleration limit Gm1 to the value limited in accordance with the LKAS opening lateral acceleration limit Gm2, and therefore, the target vehicle speed Vt is also reduced in a stepwise manner. Thereby, the deceleration thereafter becomes large, and the actual lateral acceleration Ga and the actual vehicle speed Va change to approach the respective target values. At the point P1 where the maximum curvature from the current position to the future position becomes constant, the changes of the target lateral acceleration Gt and the target vehicle speed Vt end, and thereafter, the target lateral acceleration Gt and the target vehicle speed Vt have constant values. The actual vehicle speed Va matches the target vehicle speed Vt at a point P1, and does not change thereafter, but since the curvature of the lane increases thereafter, the actual lateral acceleration Ga increases at a point P3 as the starting point of the curvature constant section to match the target lateral acceleration Gt.

Fig. 9 shows a case where the LKAS is opened from the off state when the vehicle is traveling on the curvature constant section of the curve. In this case, at the point P4 where LKAS is on, the target lateral acceleration Gt is decreased in a stepwise manner by switching from the value limited in accordance with the LKAS closing lateral acceleration limit Gm1 to the value limited in accordance with the LKAS opening lateral acceleration limit Gm2, and therefore, the target vehicle speed Vt is also decreased in a stepwise manner. Thereby, the deceleration becomes large, and the actual lateral acceleration Ga and the actual vehicle speed Va change to approach the respective target values. The deceleration by the adaptive cruise control continues to a point P5 at which point P5 the actual vehicle speed Va matches the target vehicle speed Vt, after which the vehicle speed V becomes constant without acceleration or deceleration.

Fig. 10 shows a case where the LKAS is closed from the on state when the vehicle is traveling on the curvature constant section of the curve. In this case, at the point P6 where LKAS is closed, the target lateral acceleration Gt is increased in a stepwise manner by switching from the value limited in accordance with the LKAS opening lateral acceleration limit Gm2 to the value limited in accordance with the LKAS closing lateral acceleration limit Gm1, and therefore, the target vehicle speed Vt is also increased in a stepwise manner. Thereby, the acceleration becomes large, and the actual lateral acceleration Ga and the actual vehicle speed Va change to approach the respective target values. The acceleration by the adaptive cruise control continues to the point P7 at which point P7 the actual vehicle speed Va matches the target vehicle speed Vt, after which the vehicle speed V becomes constant without acceleration or deceleration.

Fig. 11 shows a situation in which the vehicle is driving from a straight lane to a curve, and LKAS is turned off from the on state slightly before the vehicle enters the curve, i.e., LKAS is turned off during deceleration of the vehicle. In this case, as the future position of the vehicle enters the curvature increasing section of the curve from before the vehicle enters the curve, the target lateral acceleration Gt limited by the LKAS-on lateral acceleration limit value Gm2 acquired from the second table starts to increase, and the target vehicle speed Vt limited by the vehicle speed upper limit value Vm acquired from the second table starts to decrease, with the curvature radius R of the lane gradually decreasing (i.e., it is determined that the vehicle is traveling the curvature increasing section of the curve). Thereafter, at a point P8 where LKAS is closed, the target lateral acceleration Gt is increased in a stepwise manner by switching from a value limited in accordance with the LKAS opening lateral acceleration limit Gm2 to a value limited in accordance with the LKAS closing lateral acceleration limit Gm 1. Further, if the processing from step ST39 to step ST41 in fig. 4 is not provided, the vehicle speed upper limit value Vm acquired from the second table is switched to the vehicle speed upper limit value Vm acquired from the first table, which is larger than the vehicle speed upper limit value Vm acquired from the second table, and therefore, the target vehicle speed Vt is increased to a high value in a stepwise manner.

However, from the point P8 onward, the vehicle speed upper limit value Vm (and thus the target vehicle speed Vt) acquired from the first table gradually decreases as the vehicle travels, because the future position of the vehicle is on the curvature increasing section of the curve. Therefore, in the case where the LKAS is turned off from the on state while the vehicle is decelerated by the vehicle speed control unit 33, if no measure is taken, the vehicle speed control unit 33 accelerates the vehicle in accordance with an increase in the target vehicle speed Vt in a stepwise manner, and then decelerates the vehicle in accordance with a gradual decrease in the target vehicle speed Vt. Such vehicle speed control, which would result in frequent changes in the behavior of the vehicle, would reduce the marketability of the vehicle.

In the present embodiment, since the processing from step ST39 to step ST41 is provided, when LKAS is turned off slightly at the point P8 before the vehicle enters the curve (and therefore, when the vehicle is decelerating by the vehicle speed control unit 33), the target vehicle speed Vt is maintained at the value of the vehicle speed upper limit value Vm acquired from the second table until the vehicle reaches the point P9 at which the vehicle speed upper limit value Vm acquired from the first table matches the actual vehicle speed Va. That is, the increase of the vehicle speed upper limit value Vm (a shaded portion in fig. 11) due to the stop of the LKAS is restricted. Therefore, in the above-described situation, the vehicle speed control unit 33 limits the increase of the vehicle speed upper limit value Vm so as to prevent undesired acceleration of the vehicle before deceleration, so that the marketability of the vehicle can be improved.

Fig. 12 shows a situation in which the vehicle is driving on a curve towards a straight lane with LKAS off and the LKAS is switched on during acceleration of the vehicle on a section of the curve where the curvature of the curve decreases. In this case, the target lateral acceleration Gt limited according to the LKAS closing lateral acceleration limit value Gm1 acquired from the first table decreases from the point P10 at which the curvature decreasing link starts, while the target vehicle speed Vt limited according to the vehicle speed upper limit value Vm acquired from the first table increases from the point P10. Thereafter, at a point P11 where LKAS is on, the target lateral acceleration Gt is decreased in a stepwise manner by switching from a value limited in accordance with the LKAS closing lateral acceleration limit Gm1 to a value limited in accordance with the LKAS opening lateral acceleration limit Gm 2. Further, if the processing from step ST19 to step ST21 in fig. 3 is not provided, the vehicle speed upper limit value Vm acquired from the first table is switched to the vehicle speed upper limit value Vm acquired from the second table, which is lower than the vehicle speed upper limit value Vm acquired from the first table, and therefore, the target vehicle speed Vt is reduced to a low value in a stepwise manner.

However, from the point P11 onward, the vehicle speed upper limit value Vm (and thus the target vehicle speed Vt) acquired from the second table gradually increases as the vehicle travels, because the vehicle is on a curvature-decreasing section where the curvature radius R of the curve gradually increases. Therefore, for the case where LKAS is not executed when the vehicle enters the curvature decreasing section and then is turned on while the vehicle is traveling on the curvature decreasing section (i.e., during acceleration of the vehicle), if nothing is done, the vehicle speed control unit 33 will decelerate the vehicle in a stepwise manner in accordance with the decrease in the target vehicle speed Vt and then accelerate the vehicle in accordance with the gradual increase in the target vehicle speed Vt. Such vehicle speed control, which would result in frequent changes in the behavior of the vehicle, would reduce the marketability of the vehicle.

In the present embodiment, since the processing from step ST19 to step ST21 is provided, when LKAS is turned on at the point P11 while the vehicle is traveling on the curvature decreasing road section of the curve (and therefore, when the vehicle is accelerating by the vehicle speed control unit 33), the target vehicle speed Vt is maintained at the value of the vehicle speed upper limit value Vm acquired from the first table until the vehicle reaches the point P12 at which the vehicle speed upper limit value Vm acquired from the second table matches the actual vehicle speed Va. That is, the decrease of the vehicle speed upper limit value Vm (a portion shown by hatching in fig. 12) due to the opening of the LKAS is restricted. Therefore, in the above-described situation, the vehicle speed control unit 33 limits the decrease of the vehicle speed upper limit value Vm so as to prevent an undesired deceleration of the vehicle before acceleration, so that the marketability of the vehicle can be improved.

Note that, in the section from the point P11 to the point P12, the actual lateral acceleration Ga is larger than the target lateral acceleration Gt. This means that in this section, the steering of the vehicle control performed by the control device 15 may not provide sufficient steering power, and may require the user to perform steering operation to intervene.

Next, the effects provided by the vehicle speed control performed as above will be described below. As described above, the vehicle speed upper limit value Vm is set to different values depending on whether or not LKAS is executed. Therefore, the vehicle speed upper limit value Vm during the turning of the vehicle is set to different values depending on whether or not the LKAS is executed, and therefore, the vehicle speed control unit 33 can execute appropriate vehicle speed control depending on whether only the vehicle speed is controlled or both the vehicle speed and the trajectory (steering) of the vehicle are controlled.

For the case where only the vehicle speed V is controlled, the driver performs a steering operation while knowing the shape of the traveling lane (road), and therefore, even if the vehicle speed V is maintained at a relatively high speed, the degree of discomfort felt by the driver is low. On the other hand, in the case of controlling both the vehicle speed V and the steering, the driver's attention to the steering is relatively low, and therefore, the driver tends to feel uneasy from the vehicle turning with a large lateral acceleration G. In the present embodiment, when LKAS is being executed, the vehicle speed control unit 33 sets the vehicle speed upper limit Vm lower than when LKAS is not being executed, as described above. Thus, when the steering control unit 32 is executing LKAS, the target vehicle speed Vt is limited according to a lower vehicle speed upper limit value Vm than when the driver is performing the steering operation, so that the ability to follow the lane is improved. This also suppresses the anxiety that the driver may feel when turning by LKAS. When the driver performs the steering operation, the vehicle speed V is allowed to be higher than when the steering control unit 32 is performing LKAS, and thus, an increase in distance from the preceding vehicle due to the vehicle speed limitation can be suppressed, that is, the ability to follow the preceding vehicle provided by the vehicle speed control performed by the vehicle speed control unit 33 can be enhanced, so that the comfort of the driver can be improved.

When the vehicle speed V is low, the occupant is less likely to feel uneasy even if the lateral acceleration G is high, and tends to endure a larger lateral acceleration G than when the vehicle speed V is high. In the present embodiment, the vehicle speed control unit 33 determines the vehicle speed upper limit Vm based on the prescribed lateral acceleration limit Gm (Gm1, Gm2), and sets the lateral acceleration limit Gm (Gm1, Gm2) to a larger value as the curvature radius R of the lane becomes smaller, as shown in fig. 5. Thus, the vehicle speed upper limit Vm is set based on the lateral acceleration limit Gm (Gm1, Gm2) that becomes larger as the curvature of the lane acquired by the external environment recognition unit 31 becomes larger. Therefore, when the steering control unit 32 is executing LKAS, the vehicle is allowed to turn without excessively lowering the vehicle speed V. Therefore, it is possible to perform comfortable and highly convenient vehicle speed control within a control range that can be tolerated by the occupant.

As shown in fig. 5, when LKAS is being executed, the vehicle speed control unit 33 sets the lateral acceleration limit value Gm smaller than when LKAS is not being executed. Thereby, the ability to follow the lane is improved, and therefore, the occupant can feel ease when the vehicle turns with LKAS being performed. When the driver performs the steering operation, the allowable lateral acceleration G is larger than when the steering control unit 32 is performing LKAS, and thus, an increase in the distance to the preceding vehicle due to the vehicle speed limitation can be suppressed, that is, the ability to follow the preceding vehicle provided by the vehicle speed control performed by the vehicle speed control unit 33 can be enhanced, so that the comfort of the driver can be improved.

When the curvature radius R of the lane is smaller than the prescribed value Rth, that is, when the curvature of the lane is larger than the prescribed curvature, the lateral acceleration G tends to increase to such an extent that the occupant feels uncomfortable. In the present embodiment, as shown in fig. 5, when the curvature radius R of the lane is smaller than the predetermined value Rth, the vehicle speed control unit 33 sets the LKAS-on lateral acceleration limit Gm2 smaller than the LKAS-off lateral acceleration limit Gm 1. Thus, even if the curvature of the lane is greater than or equal to the predetermined curvature, the occupant can be prevented from feeling uneasy.

As described above, the vehicle speed control unit 33 sets the LKAS-on lateral acceleration limit Gm2 to 3m/s or less²The value of (c). Thereby, the lateral acceleration while LKAS is being performed (at which the attention of the occupant to the steering operation is relatively low) is maintained to not more than 3m/s²This ensures that the anxiety of the occupant due to the lateral acceleration G can be suppressed.

When the radius of curvature R is greater than or equal to the prescribed value Rth, the lateral acceleration G cannot reach a level at which the occupant feels uncomfortable. In the present embodiment, as shown in fig. 5, when the curvature radius R of the lane is greater than or equal to the predetermined value Rth, the vehicle speed control unit 33 sets the LKAS-on lateral acceleration limit value Gm2 to the same value as the LKAS-off lateral acceleration limit value Gm 1. Therefore, when the curvature is less than or equal to the prescribed curvature, it is possible to prevent the vehicle speed V from being excessively reduced, which would deteriorate the convenience and comfort of the vehicle speed control.

The foregoing has described the specific embodiments, but the present invention is not limited to the above-described embodiments, and may be modified or changed in various ways.

For example, when LKAS is being executed, the vehicle speed control unit 33 may set the vehicle speed upper limit Vm higher than when LKAS is not being executed. Thereby, the ability to follow the leading vehicle while LKAS is being performed may be improved. Further, when the driver performs the steering operation, the target vehicle speed Vt is limited according to the vehicle speed upper limit value Vm lower than that when the steering control unit 32 is performing the LKAS, thereby reducing the burden on the driver to perform the steering operation.

Further, the specific structure, arrangement, number, and the like of each member or portion, and the specific content and order of processing may be appropriately changed within the scope of the present invention. Also, not all the components shown in the foregoing embodiments are essential, but these components may be selectively employed as appropriate.