Driving support device

Abstract

A driving support device achieves natural acceleration like manual driving when performing a lane change based on autonomous driving. The driving support device includes a vehicle control unit that controls the operation of its own vehicle (1). The vehicle control unit executes first following control for controlling the acceleration and deceleration of its own vehicle so that its own vehicle follows a first preceding vehicle traveling ahead of its own vehicle in the same lane as its own vehicle. When starting a lane change of its own vehicle during the execution of the first following control, during the implementation of the lane change, the first following control is prohibited, and second following control for controlling the acceleration and deceleration of its own vehicle so that its own vehicle follows a second preceding vehicle traveling ahead of its own vehicle in the lane of the lane change destination is executed.

Description

Technical Field

[0001] The present invention relates to a driving support device. Background Art

[0002] In recent years, vehicles capable of performing autonomous driving under predetermined conditions have been developed. When implementing autonomous driving in such a vehicle, the acceleration, steering, and braking of the vehicle are automatically performed.

[0003] For example, when there is another vehicle traveling in front of the vehicle, the acceleration and deceleration (acceleration / deceleration) of the vehicle are controlled so that the vehicle follows the other vehicle. In addition, when overtaking another vehicle is requested by the driver or the system, a lane change based on autonomous driving is performed.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2019-18694

[0007] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2018-103833

[0008] Patent Document 3: Japanese Unexamined Patent Application Publication No. 2017-202742 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] In a lane change based on manual driving, basically, the acceleration and deceleration of the vehicle are controlled so that the vehicle follows the preceding vehicle in the lane of the lane change destination. Therefore, in a lane change based on autonomous driving, when the following object is switched from the preceding vehicle in the lane before the lane change to the preceding vehicle in the lane of the lane change destination during the lane change, it is difficult to achieve natural acceleration as in manual driving (see paragraph 0013 of Patent Document 1).

[0011] On the other hand, in the vehicle described in Patent Document 1 or 2, in a lane change based on autonomous driving, both the preceding vehicle in the lane before the lane change and the preceding vehicle in the lane of the lane change destination are used as following objects, and the acceleration and deceleration of the vehicle are controlled based on the lower value of the target accelerations calculated for both preceding vehicles. However, when the target acceleration calculated with the preceding vehicle in the lane before the lane change as the following object is selected, the acceleration and deceleration of the vehicle are controlled so that the vehicle follows the preceding vehicle in the lane before the lane change during the lane change.

[0012] In addition, Patent Document 3 describes that when performing a lane change based on autonomous driving, the target inter-vehicle distance from the preceding vehicle in the lane before the lane change is increased to increase the acceleration of the vehicle during the lane change. However, in this case as well, the preceding vehicle in the lane before the lane change is selected as the following object during the lane change, so it is difficult to achieve natural acceleration as in manual driving.

[0013] In view of the above problems, an object of the present invention is to achieve natural acceleration as in manual driving when performing a lane change based on autonomous driving.

[0014] Technical solution for solving the problem

[0015] The gist of the present disclosure is as follows.

[0016] (1) A driving support device includes a vehicle control unit that controls the operation of its own vehicle. The vehicle control unit performs first following control for controlling the acceleration and deceleration of its own vehicle so that its own vehicle follows a first preceding vehicle traveling in front of its own vehicle in the same lane. When starting a lane change of its own vehicle during the execution of the first following control, during the execution of the lane change, the first following control is prohibited, and second following control for controlling the acceleration and deceleration of its own vehicle so that its own vehicle follows a second preceding vehicle traveling in front of its own vehicle in the lane of the lane change destination is executed.

[0017] (2) According to the driving support device described in (1) above, the vehicle control unit brakes its own vehicle when a predetermined parameter determined based on the relative relationship between its own vehicle and the first preceding vehicle becomes equal to or less than a threshold value.

[0018] (3) According to the driving support device described in (2) above, the threshold value during the lane change is smaller than the threshold value before the lane change.

[0019] (4) According to the driving support device described in (2) or (3) above, it further includes: a target acceleration calculation unit that calculates the target acceleration of its own vehicle; and an upper limit value calculation unit that calculates the upper limit value of the target acceleration. The target acceleration calculation unit limits the target acceleration in the second following control to a value equal to or less than the upper limit value, and the vehicle control unit controls the acceleration and deceleration of its own vehicle so that the acceleration of its own vehicle becomes the target acceleration.

[0020] (5) The driving support device according to (4) above, the upper limit value calculation unit calculates an allowable limit value based on the inter-vehicle distance between the host vehicle and the first preceding vehicle and the relative speed between the host vehicle and the first preceding vehicle at the start of the lane change in such a manner that braking of the host vehicle with respect to the first preceding vehicle is not performed during the lane change, and calculates the upper limit value as a value equal to or less than the allowable limit value.

[0021] (6) The driving support device according to (5) above, the upper limit value calculation unit changes the difference between the allowable limit value and the upper limit value based on the inter-vehicle distance between the host vehicle and the first preceding vehicle during the lane change.

[0022] (7) The driving support device according to (5) or (6) above, the upper limit value calculation unit changes the difference between the allowable limit value and the upper limit value based on the lateral position of the host vehicle during the lane change.

[0023] (8) The driving support device according to any one of (1) to (7) above further includes a target acceleration calculation unit that calculates the target acceleration of the host vehicle, and the vehicle control unit controls the acceleration and deceleration of the host vehicle so that the acceleration of the host vehicle becomes the target acceleration. The target acceleration calculation unit calculates the target acceleration in such a manner that the inter-vehicle distance between the host vehicle and the second preceding vehicle becomes the target inter-vehicle distance during the second following control. When the inter-vehicle distance between the host vehicle and the second preceding vehicle at the start of the lane change is less than a predetermined set inter-vehicle distance, the target inter-vehicle distance in the second following control is gradually increased from the inter-vehicle distance between the host vehicle and the second preceding vehicle at the start of the lane change to the set inter-vehicle distance.

[0024] Advantages of the Invention

[0025] According to the present invention, it is possible to achieve natural acceleration like manual driving when performing a lane change based on autonomous driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 FIG. schematically shows a part of the configuration of a vehicle provided with the driving support device according to the first embodiment of the present invention.

[0027] Figure 2 FIG. shows an example of a target detection device provided in a vehicle.

[0028] Figure 3 FIG. is a functional block diagram of the ECU in the first embodiment.

[0029] Figure 4This is a diagram showing a situation where a vehicle changes lanes in order to overtake other vehicles.

[0030] Figure 5A This is a flowchart showing a control routine for target acceleration calculation processing in the first embodiment.

[0031] Figure 5B This is a flowchart showing a control routine for target acceleration calculation processing in the first embodiment.

[0032] Figure 6 This is a flowchart showing a control routine for the first target deceleration calculation processing in the first embodiment.

[0033] Figure 7 This is a flowchart showing a control routine for the second target deceleration calculation processing in the first embodiment.

[0034] Figure 8 This is a flowchart showing a control routine for acceleration / deceleration control in the first embodiment.

[0035] Figure 9 This is a flowchart showing a control routine for the first target deceleration calculation processing in the second embodiment.

[0036] Figure 10 This is a functional block diagram of the ECU in the third embodiment.

[0037] Figure 11 This is a flowchart showing a control routine for upper limit value calculation processing in the third embodiment.

[0038] Figure 12 This is a diagram schematically showing the transition of the deviation rate during lane change.

[0039] Figure 13 This is a diagram showing an example of a map for determining an inhibition gain based on the lateral position of the vehicle and the inter-vehicle distance between the vehicle and the first preceding vehicle.

[0040] Figure 14 This is a flowchart showing a control routine for target acceleration calculation processing in the third embodiment.

[0041] Figure 15 This is a flowchart showing a control routine for target inter-vehicle distance setting processing in the fourth embodiment.

[0042] Reference Numeral Explanation

[0043] 1 Vehicle;

[0044] 10 Electronic Control Unit (ECU);

[0045] 15 Vehicle Control Unit;

[0046] C1 First leading vehicle;

[0047] C2 Second leading vehicle. Detailed implementation mode

[0048] Hereinafter, with reference to the accompanying drawings, the implementation modes of the present invention will be described in detail. In addition, in the following description, the same components are denoted by the same reference numerals.

[0049] <First implementation mode>

[0050] First, with reference to Figures 1 - 8 , the first implementation mode of the present invention will be described.

[0051] <Description of the whole vehicle>

[0052] Figure 1 is a diagram schematically showing a part of the configuration of a vehicle 1 provided with a driving support device according to the first implementation mode of the present invention. In the vehicle 1, it is possible to implement automatic driving that automatically controls part or all of the acceleration, steering, and braking of the vehicle 1. In addition, automatic driving is also called autonomous driving.

[0053] As Figure 1 shown, the vehicle 1 includes an object detection device 2, a vehicle state detection device 3, a GNSS receiver 4, a map database 5, a navigation device 6, an actuator 7, an input / output device 8, and an electronic control unit ((Electronic Control Unit (ECU)) 10. The object detection device 2, the vehicle state detection device 3, the GNSS receiver 4, the map database 5, the navigation device 6, the actuator 7, and the input / output device 8 are communicably connected to the ECU 10 via an in-vehicle network based on a standard such as CAN (Controller Area Network).

[0054] The object detection device 2 detects objects (other vehicles, signs, white lines, falling objects, etc.) existing around the vehicle 1 (own vehicle). Specifically, the object detection device 2 detects the presence or absence of objects around the vehicle 1, the distance from the vehicle 1 to the object, and the relative speed between the vehicle 1 and the object. The object detection device 2 includes, for example, a camera, a lidar (LIDAR (Laser Imaging Detection And Ranging)), a millimeter-wave radar, an ultrasonic sensor (sonar), etc. The output of the object detection device 2 is sent to the ECU 10.

[0055] Figure 2 is a diagram showing an example of the object detection device 2 provided in the vehicle 1. In Figure 2In the example, the vehicle 1 is equipped with an external camera 21, a lidar 22, a millimeter-wave radar 23, and an ultrasonic sensor (sonar) 24 as the target detection device 2.

[0056] The external camera 21 captures the surroundings of the vehicle 1 to generate an image of the surroundings of the vehicle 1. For example, the external camera 21 is arranged in front of the vehicle 1 (e.g., the back of the interior mirror in the vehicle, the front bumper, etc.) so as to capture the front of the vehicle 1. In addition, the external camera 21 can be a stereoscopic camera capable of ranging.

[0057] The lidar 22 irradiates laser light to the surroundings of the vehicle 1 and receives the reflected light of the laser. Thereby, the lidar 22 can detect the presence or absence of a target around the vehicle 1, the distance from the vehicle 1 to the target, and the relative speed between the vehicle 1 and the target. For example, the lidar 22 is arranged at the front and rear of the vehicle 1 (e.g., the front bumper and the rear bumper of the vehicle 1).

[0058] The millimeter-wave radar 23 transmits millimeter waves to the surroundings of the vehicle 1 and receives the reflected waves of the millimeter waves. Thereby, the millimeter-wave radar 23 can detect the presence or absence of a target around the vehicle 1, the distance from the vehicle 1 to the target, and the relative speed between the vehicle 1 and the target. For example, the millimeter-wave radar 23 is arranged at the front and rear of the vehicle 1 (e.g., the front bumper and the rear bumper of the vehicle 1).

[0059] The ultrasonic sensor 24 transmits ultrasonic waves to the surroundings of the vehicle 1 and receives the reflected waves of the ultrasonic waves. Thereby, the ultrasonic sensor 24 can detect the presence or absence of a target around the vehicle 1, the distance from the vehicle 1 to the target, and the relative speed between the vehicle 1 and the target. For example, the ultrasonic sensor 24 is arranged on both sides of the vehicle 1 (e.g., the left and right front fenders of the vehicle 1).

[0060] In addition, the positions and numbers of the external camera 21, the lidar 22, the millimeter-wave radar 23, and the ultrasonic sensor 24 are not limited to the above. In addition, some of them can also be omitted.

[0061] The vehicle state detection device 3 detects the state quantities of the vehicle 1. Among the state quantities of the vehicle 1, include the speed (vehicle speed), acceleration, steering angle, yaw rate, etc. of the vehicle 1. The vehicle state detection device 3 includes, for example, a vehicle speed sensor, an acceleration sensor, a steering angle sensor, a yaw rate sensor, etc. The output of the vehicle state detection device 3 is sent to the ECU 10.

[0062] The GNSS receiver 4 captures multiple positioning satellites and receives the radio waves transmitted from the positioning satellites. The GNSS receiver 4 calculates the distance to the positioning satellites based on the difference between the transmission time and the reception time of the radio waves, and detects the current position of the vehicle 1 (for example, the latitude and longitude of the vehicle 1) based on the distance to the positioning satellites and the positions (orbital information) of the positioning satellites. The output of the GNSS receiver 4 is sent to the ECU 10. In addition, GNSS (Global Navigation Satellite System) is a general term for satellite positioning systems such as GPS in the United States, GLONASS in Russia, Galileo in Europe, QZSS in Japan, BeiDou in China, and IRNSS in India. Therefore, the GNSS receiver 4 includes a GPS receiver.

[0063] The map database 5 stores map information. The map information stored in the map database 5 can also be updated regularly using communication with the outside of the vehicle 1, SLAM (Simultaneous Localization and Mapping) technology, etc. The ECU 10 obtains the map information from the map database 5.

[0064] The navigation device 6 sets the driving route of the vehicle 1 to the destination based on the current position of the vehicle 1 detected by the GNSS receiver 4, the map information of the map database 5, the input made by the driver, etc. The driving route set by the navigation device 6 is sent to the ECU 10. In addition, the GNSS receiver 4 and the map database 5 can also be incorporated into the navigation device 6.

[0065] The actuator 7 makes the vehicle 1 move. For example, the actuator 7 includes a driving device (at least one of an engine and a motor) for accelerating the vehicle 1, a brake actuator for braking the vehicle 1, a steering motor for steering the vehicle 1, etc. The ECU 10 controls the actuator 7 in order to implement the autonomous driving of the vehicle 1.

[0066] The input / output device 8 performs input / output of information between the driver and the vehicle 1. The input / output device 8 includes, for example, a display for displaying information, a speaker for generating sound, an operation button or an operation switch for the driver to perform an input operation, a microphone for receiving the driver's voice, etc. The output of the ECU 10 is transmitted to the driver via the input / output device 8, and the input from the driver is sent to the ECU 10 via the input / output device 8. The input / output device 8 is also referred to as a Human-Machine Interface (HMI).

[0067] The ECU 10 executes various controls of the vehicle. As Figure 1As shown in the figure, the ECU 10 includes a communication interface 11, a memory 12, and a processor 13. The communication interface 11 and the memory 12 are connected to the processor 13 via signal lines. In addition, in this embodiment, one ECU 10 is provided, but multiple ECUs can also be provided for each function.

[0068] The communication interface 11 has an interface circuit for connecting the ECU 10 to the in-vehicle network. The ECU 10 communicates with the object detection device 2, the vehicle state detection device 3, the GNSS receiver 4, the map database 5, the navigation device 6, the actuator 7, and the input / output device 8 via the communication interface 11.

[0069] The memory 12 includes, for example, a volatile semiconductor memory and a non-volatile semiconductor memory. The memory 12 stores programs, data, etc. used when the processor 13 performs various processes.

[0070] The processor 13 has one or more CPUs (Central Processing Unit) and its peripheral circuits. In addition, the processor 13 can also have an arithmetic circuit such as a logic operation unit or a numerical operation unit.

[0071] <Driver assistance device>

[0072] In this embodiment, the ECU 10 functions as a driver assistance device for performing driver assistance of the vehicle 1. Figure 3 It is a functional block diagram of the ECU 10 in the first embodiment. In this embodiment, the ECU 10 includes a vehicle control unit 15, a target acceleration calculation unit 16, and a target deceleration calculation unit 17. The vehicle control unit 15, the target acceleration calculation unit 16, and the target deceleration calculation unit 17 are functional modules implemented by the processor 13 of the ECU 10 executing the programs stored in the memory 12 of the ECU 10.

[0073] The vehicle control unit 15 controls the operation of the vehicle 1. In this embodiment, when the driver selects the autonomous driving mode as the driving mode of the vehicle 1, the autonomous driving of the vehicle 1 is implemented under predetermined conditions. The vehicle control unit 15 accelerates, steers, and brakes the vehicle 1 when implementing the autonomous driving of the vehicle 1. Specifically, the vehicle control unit 15 uses the actuator 7 to accelerate, steer, and brake the vehicle 1 in such a way that the vehicle 1 travels safely along a pre-determined driving path.

[0074] The target acceleration calculation unit 16 calculates the target acceleration of the vehicle 1, and the vehicle control unit 15 controls the acceleration and deceleration of the vehicle 1 in such a way that the acceleration of the vehicle 1 becomes the target acceleration. The target deceleration calculation unit 17 calculates the target deceleration of the vehicle 1, and the vehicle control unit 15 brakes the vehicle 1 in such a way that the deceleration of the vehicle 1 becomes the target deceleration as needed.

[0075] Figure 4 This is a diagram showing the situation where the lane change of vehicle 1 is carried out in order to overtake other vehicles. As Figure 4 shown, when there is a first leading vehicle C1 traveling in front of vehicle 1 in the same lane as vehicle 1, the vehicle control unit 15 executes first following control to control the acceleration and deceleration of vehicle 1 in such a way that vehicle 1 follows the first leading vehicle C1. In the first following control, the target acceleration calculation unit 16 calculates the target acceleration of vehicle 1 based on the inter-vehicle distance between vehicle 1 and the first leading vehicle C1 in such a way that vehicle 1 follows the first leading vehicle C1.

[0076] On the other hand, when there is no first leading vehicle C1, the vehicle control unit 15 executes constant speed control to control the acceleration and deceleration of vehicle 1 in such a way that the speed of vehicle 1 becomes the set speed. In the constant speed control, the target acceleration calculation unit 16 calculates the target acceleration of vehicle 1 based on the speed of vehicle 1 in such a way that the speed of vehicle 1 becomes the set speed. The first following control and the constant speed control are also collectively referred to as Adaptive Cruise Control (ACC).

[0077] In addition, when a lane change of vehicle 1 is requested by the driver or the system, the vehicle control unit 15 performs a lane change based on autonomous driving. For example, when a lane change for overtaking the first leading vehicle C1 is requested by the driver or the system, the vehicle control unit 15 controls the steering of vehicle 1 in such a way that vehicle 1 moves to the lane of the lane change destination (in this case, the overtaking lane).

[0078] When performing a lane change, it is necessary to control not only the steering of vehicle 1 but also the acceleration and deceleration of vehicle 1. As Figure 4 shown, sometimes, when performing a lane change in order to overtake the first leading vehicle C1, there is a second leading vehicle C2 traveling in front of vehicle 1 in the lane of the lane change destination. In the case of performing a lane change based on manual driving in this situation, generally, the driver controls the acceleration and deceleration of vehicle 1 with the second leading vehicle C2 as the following object instead of the first leading vehicle C1.

[0079] Therefore, in the present embodiment, when the vehicle control unit 15 starts the lane change of vehicle 1 during the execution of the first following control, during the execution of the lane change, the first following control is prohibited, and the second following control is executed to control the acceleration and deceleration of vehicle 1 in such a way that vehicle 1 follows the second leading vehicle C2. Thereby, it is possible to achieve a natural acceleration like manual driving when performing a lane change based on autonomous driving.

[0080] In the second following control, the target acceleration calculation unit 16 calculates the target acceleration of the vehicle 1 based on the inter-vehicle distance between the vehicle 1 and the second preceding vehicle C2 so that the vehicle 1 follows the second preceding vehicle C2. In addition, when the first following control is prohibited during a lane change, the target acceleration calculation unit 16 stops calculating the target acceleration for following the first preceding vehicle C1. Thereby, an increase in the calculation load caused by setting both the first preceding vehicle C1 and the second preceding vehicle C2 as following objects can be avoided.

[0081] On the other hand, when there is no second preceding vehicle C2 during a lane change, the vehicle control unit 15 executes a constant-speed control for controlling the acceleration and deceleration of the vehicle 1 so that the speed of the vehicle 1 becomes the set speed. As described above, in the constant-speed control, the target acceleration calculation unit 16 calculates the target acceleration of the vehicle 1 based on the speed of the vehicle 1 so that the speed of the vehicle 1 becomes the set speed.

[0082] However, even if the acceleration and deceleration of the vehicle 1 are controlled as described above, a situation may occur where the vehicle 1 needs to brake due to deceleration of the preceding vehicle or the like. Therefore, the vehicle control unit 15 brakes the vehicle 1 when a predetermined parameter determined based on the relative relationship between the vehicle 1 and the preceding vehicle (the first preceding vehicle C1 or the second preceding vehicle C2) becomes equal to or less than a threshold value.

[0083] In the present embodiment, the vehicle control unit 15 brakes the vehicle 1 when a first target deceleration becomes equal to or less than a threshold value, where the first target deceleration is the deceleration required to make the relative speed between the vehicle 1 and the first preceding vehicle C1 zero at a predetermined minimum inter-vehicle distance. In addition, the vehicle control unit 15 brakes the vehicle 1 when a second target deceleration becomes equal to or less than a threshold value, where the second target deceleration is the deceleration required to make the relative speed between the vehicle 1 and the second preceding vehicle C2 zero at a predetermined minimum inter-vehicle distance.

[0084] The first target deceleration and the second target deceleration are calculated as negative values by the target deceleration calculation unit 17. In addition, the calculations of the first target deceleration and the second target deceleration performed by the target deceleration calculation unit 17 are for avoiding a collision with the preceding vehicle, and are clearly distinguished from the calculation of the target acceleration for following the preceding vehicle.

[0085] <Target Acceleration Calculation Process>

[0086] Hereinafter, with reference to Figures 5A - 8 the following flowchart, the control of the acceleration and deceleration of the vehicle 1 described above will be described in detail. Figure 5A and Figure 5BIt is a flowchart showing a control routine for target acceleration calculation processing in the first embodiment. This control routine is repeatedly executed by the ECU 10 at a predetermined execution interval during the execution of the autonomous driving of the vehicle 1.

[0087] First, in step S101, the target acceleration calculation unit 16 determines whether the vehicle 1 is performing a lane change. The start timing of the lane change is defined, for example, as when the driver agrees to the lane change via the input / output device 8, when the turn signal of the vehicle 1 is turned on for the lane change, when the start of the lane change is notified to the driver via the input / output device 8, or when the vehicle control unit 15 starts the steering operation for vehicle change. On the other hand, the end timing of the lane change is defined as when the front end of the vehicle 1 reaches the lane boundary line, when the entire vehicle 1 enters the lane of the lane change destination, when the steering operation for the lane change performed by the vehicle control unit 15 ends, or when the turn signal of the vehicle 1 is turned off.

[0088] When it is determined in step S101 that the vehicle 1 is not performing a lane change, this control routine proceeds to step S102. In step S102, the target acceleration calculation unit 16 determines whether there is a first preceding vehicle traveling in front of the vehicle 1 in the same lane based on the output of the target detection device 2. For example, the first preceding vehicle is selected as the closest other vehicle among the other vehicles traveling in the same lane as the vehicle 1 within a predetermined range in front of the vehicle 1.

[0089] When it is determined in step S102 that there is a first preceding vehicle, this control routine proceeds to step S103. In step S103, the target acceleration calculation unit 16 calculates the target acceleration of the vehicle 1 based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle so that the vehicle 1 follows the first preceding vehicle. For example, the target acceleration calculation unit 16 calculates the target acceleration TA of the vehicle 1 according to the following formula (1) based on the inter-vehicle distance d1 between the vehicle 1 and the first preceding vehicle, the target inter-vehicle distance d ta and the relative speed V r1 (speed of vehicle 1 - speed of first preceding vehicle).

[0090] TA = (d1 - d ta ) · K1 - V r1 · K2...(1)

[0091] Here, K1 and K2 are respectively predetermined positive coefficients. The inter-vehicle distance d1 and the relative speed V r1 are respectively calculated based on the output of the target detection device 2. The target inter-vehicle distance d ta is set, for example, as a preset set inter-vehicle distance.

[0092] The set inter-vehicle distance is determined in advance by the driver via the input / output device 8. For example, the driver selects a preference for the inter-vehicle distance from a plurality of set modes (such as short mode, medium mode, and long mode), and based on the selected set mode, determines the set inter-vehicle distance according to the speed of the vehicle 1. In addition, the set inter-vehicle distance can also be automatically determined according to the speed of the vehicle 1, etc. Additionally, the set inter-vehicle distance can also be a predetermined fixed value.

[0093] As can be seen from the above formula (1), the target acceleration calculation unit 16 calculates the target acceleration TA in such a way that the inter-vehicle distance d1 becomes the target inter-vehicle distance d ta and the relative speed V r1 becomes zero. In addition, the inter-vehicle distance d1 can also be expressed as the time until the vehicle 1 reaches the current position of the first preceding vehicle (Time-Headway (THW)), that is, the value obtained by dividing the inter-vehicle distance between the vehicle 1 and the first preceding vehicle by the speed of the vehicle 1. In this case, the target inter-vehicle distance d ta is also determined as time. Additionally, the second term on the right side of the above formula (1) can also be omitted. After step S103, this control routine ends.

[0094] On the other hand, when it is determined in step S102 that there is no first preceding vehicle, this control routine proceeds to step S104. In step S104, the target acceleration calculation unit 16 calculates the target acceleration of the vehicle 1 in such a way that the speed of the vehicle 1 becomes the set speed, based on the speed of the vehicle 1. For example, the target acceleration calculation unit 16 calculates the target acceleration TA of the vehicle 1 according to the following formula (2) based on the speed V of the vehicle 1 and the set speed V set .

[0095] TA = (V set - V) · K3...(2)

[0096] Here, K3 is a predetermined positive coefficient.

[0097] The speed of the vehicle 1 is detected by the vehicle state detection device 3 (specifically, a vehicle speed sensor), and the set speed V set is determined in advance by the driver via the input / output device 8. In addition, the set speed V set can also be automatically determined based on the legal maximum speed of the road on which the vehicle 1 is traveling, etc. A positive value is calculated as the target acceleration TA when the speed V of the vehicle 1 is lower than the set speed V set , and a negative value is calculated as the target acceleration TA when the speed V of the vehicle 1 is higher than the set speed V set . After step S104, this control routine ends.

[0098] On the other hand, when it is determined in step S101 that the lane change of vehicle 1 is being performed, this control routine proceeds to step S105. In step S105, the target acceleration calculation unit 16 determines, based on the output of the target detection device 2, whether there is a second preceding vehicle traveling ahead of vehicle 1 in the lane of the lane change destination. For example, the second preceding vehicle is selected as the nearest other vehicle among the other vehicles traveling in the lane of the lane change destination within a predetermined range ahead of vehicle 1.

[0099] When it is determined in step S105 that there is a second preceding vehicle, this control routine proceeds to step S106. In step S106, the target acceleration calculation unit 16 calculates the target acceleration of vehicle 1 based on the inter-vehicle distance between vehicle 1 and the second preceding vehicle so that vehicle 1 follows the second preceding vehicle. For example, the target acceleration calculation unit 16 calculates the target acceleration TA of vehicle 1 according to the following equation (3) similar to the above equation (1) based on the inter-vehicle distance d2 between vehicle 1 and the second preceding vehicle, the target inter-vehicle distance d ta and the relative speed V r2 (speed of vehicle 1 - speed of the second preceding vehicle).

[0100] TA = (d2 - d ta )·K1 - V r2 ·K2…(3)

[0101] The inter-vehicle distance d2 and the relative speed V r2 are respectively calculated based on the output of the target detection device 2. As can be seen from the above equation (3), the target acceleration calculation unit 16 calculates the target acceleration TA so that the inter-vehicle distance d2 becomes the target inter-vehicle distance d ta and the relative speed V r2 becomes zero. In addition, the inter-vehicle distance d2 can also be expressed as the time until vehicle 1 reaches the current position of the second preceding vehicle (Time-Headway (THW)), that is, the value obtained by dividing the inter-vehicle distance between vehicle 1 and the second preceding vehicle by the speed of vehicle 1. In this case, the target inter-vehicle distance d ta is also determined as time. In addition, the second term on the right side of the above equation (3) can also be omitted. After step S106, this control routine ends.

[0102] On the other hand, when it is determined in step S105 that there is no second preceding vehicle, this control routine proceeds to step S107. In step S107, the target acceleration calculation unit 16 calculates the target acceleration of vehicle 1 based on the speed of vehicle 1 in the same way as in step S104 so that the speed of vehicle 1 becomes the set speed. After step S107, this control routine ends.

[0103] <First target deceleration calculation process>

[0104] Figure 6 This is a flowchart showing a control routine for the first target deceleration calculation process in the first embodiment. This control routine is repeatedly executed by the ECU 10 at a predetermined execution interval during the execution of the autonomous driving of the vehicle 1.

[0105] First, in step S201, the target deceleration calculation unit 17, similar to Figure 5A step S101 of, determines whether there is a first preceding vehicle based on the output of the target detection device 2. When it is determined in step S201 that there is a first preceding vehicle, this control routine proceeds to step S202.

[0106] In step S202, the target deceleration calculation unit 17 calculates the first target deceleration required to make the relative speed between the vehicle 1 and the first preceding vehicle zero at a predetermined minimum inter-vehicle distance. For example, the target deceleration calculation unit 17 calculates the first target deceleration TD1 based on the relative speed V r1 between the vehicle 1 and the first preceding vehicle and the inter-vehicle distance d1 between the vehicle 1 and the first preceding vehicle according to the following formula (4).

[0107] TD1 = -(V r1 ) 2 / {α·(d1 - d low )}…(4)

[0108] Here, α is a predetermined coefficient (for example, 1 to 2) determined according to the deceleration mode of the vehicle 1, and is set to 2 when braking the vehicle 1 at a constant deceleration. d low is a predetermined minimum inter-vehicle distance, for example, 3 m to 5 m. The first target deceleration TD1 is calculated as a negative value, and the larger its absolute value, the more sharply the vehicle 1 decelerates.

[0109] Next, in step S203, the target deceleration calculation unit 17 determines whether the first target deceleration TD1 is equal to or less than the threshold value G brk . The threshold value G brk is determined in advance as a negative value considering the braking performance of the vehicle 1 and the like.

[0110] When it is determined in step S203 that the first target deceleration TD1 is equal to or less than the threshold value G brk , this control routine proceeds to step S204. In step S204, the target deceleration calculation unit 17 sets the first braking flag F1 to 1. That is, the first braking flag F1 is set to 1 when braking of the vehicle 1 with respect to the first preceding vehicle is required. After step S204, this control routine ends.

[0111] On the other hand, when it is determined in step S201 that there is no first leading vehicle or when it is determined in step S203 that the first target deceleration TD1 is greater than the threshold G brk in the case, this control routine proceeds to step S205. In this case, since there is no need to brake vehicle 1 with respect to the first leading vehicle, in step S205, the target deceleration calculation unit 17 sets the first braking flag F1 to zero. After step S205, this control routine ends.

[0112] In addition, the target deceleration calculation unit 17 may also determine in step S203 whether the inter-vehicle distance between vehicle 1 and the first leading vehicle is the threshold G brk below. That is, the predetermined parameter determined based on the relative relationship between vehicle 1 and the first leading vehicle may also be the inter-vehicle distance between vehicle 1 and the first leading vehicle.

[0113] <Second target deceleration calculation process>

[0114] Figure 7 is a flowchart of a control routine showing the second target deceleration calculation process in the first embodiment. This control routine is repeatedly executed by the ECU 10 at a predetermined execution interval during the autonomous driving of vehicle 1.

[0115] First, in step S301, the target deceleration calculation unit 17 is the same as Figure 5B in step S105 of, based on the output of the target detection device 2, determines whether there is a second leading vehicle. When it is determined in step S301 that there is a second leading vehicle, this control routine proceeds to step S302.

[0116] In step S302, the target deceleration calculation unit 17 calculates the second target deceleration required to make the relative speed between vehicle 1 and the second leading vehicle zero at a predetermined minimum inter-vehicle distance. For example, the target deceleration calculation unit 17 is based on the relative speed V between vehicle 1 and the second leading vehicle r2 and the inter-vehicle distance d2 between vehicle 1 and the second leading vehicle, and calculates the second target deceleration TD2 according to the following formula (5) which is the same as the above formula (4).

[0117] TD2 = -(V r2 ) 2 / {α·(d2 - d low )}…(5)

[0118] The second target deceleration TD2 is calculated as a negative value, and the larger its absolute value, the more sharply vehicle 1 decelerates.

[0119] Next, in step S303, the target deceleration calculation unit 17 determines whether the second target deceleration TD2 is the threshold value G brk The following is the threshold value G brk is determined in advance as a negative value in consideration of the braking performance of the vehicle 1 and the like

[0120] In the case where it is determined in step S303 that the second target deceleration TD2 is the threshold value G brk or less, this control routine proceeds to step S304. In step S304, the target deceleration calculation unit 17 sets the second braking flag F2 to 1. That is, the second braking flag F2 is set to 1 when braking of the vehicle 1 with respect to the second preceding vehicle is required. After step S304, this control routine ends

[0121] On the other hand, in the case where it is determined in step S301 that there is no second preceding vehicle or in the case where it is determined in step S303 that the second target deceleration TD2 is greater than the threshold value G brk this control routine proceeds to step S305. In this case, since braking of the vehicle 1 with respect to the second preceding vehicle is not required, in step S305, the target deceleration calculation unit 17 sets the second braking flag F2 to zero. After step S305, this control routine ends

[0122] In addition, the target deceleration calculation unit 17 may also determine in step S303 whether the inter-vehicle distance between the vehicle 1 and the second preceding vehicle is the threshold value G brk or less. That is, the predetermined parameter determined based on the relative relationship between the vehicle 1 and the second preceding vehicle may also be the inter-vehicle distance between the vehicle 1 and the second preceding vehicle

[0123] <Acceleration / Deceleration Control>

[0124] Figure 8 is a flowchart showing a control routine of the acceleration / deceleration control in the first embodiment. This control routine is repeatedly executed by the ECU 10 at a predetermined execution interval during the execution of the autonomous driving of the vehicle 1

[0125] First, in step S401, the vehicle control unit 15 determines whether the first braking flag F1 is 1. In the case where it is determined that the first braking flag F1 is 1, this control routine proceeds to step S402

[0126] In step S402, the vehicle control unit 15 determines whether the second braking flag F2 is 1. In the case where it is determined that the second braking flag F2 is 1, this control routine proceeds to step S403

[0127] In step S403, the vehicle control unit 15 determines whether the first target deceleration TD1 is less than or equal to the second target deceleration TD2. If it is determined that the first target deceleration TD1 is less than or equal to the second target deceleration TD2, this control routine proceeds to step S404. Additionally, if it is determined in step S402 that the second braking flag F2 is zero, this control routine skips step S403 and proceeds to step S404.

[0128] In step S404, the vehicle control unit 15 controls the acceleration and deceleration of the vehicle 1 based on the first target deceleration TD1. Specifically, the vehicle control unit 15 uses the actuator 7 to brake the vehicle 1 in such a way that the deceleration of the vehicle 1 becomes the first target deceleration TD1. After step S404, this control routine ends.

[0129] On the other hand, if it is determined in step S403 that the first target deceleration TD1 is greater than the second target deceleration TD2, this control routine proceeds to step S406. In step S406, the vehicle control unit 15 controls the acceleration and deceleration of the vehicle 1 based on the second target deceleration TD2. Specifically, the vehicle control unit 15 uses the actuator 7 to brake the vehicle 1 in such a way that the deceleration of the vehicle 1 becomes the second target deceleration TD2. After step S406, this control routine ends.

[0130] Additionally, if it is determined in step S401 that the first braking flag F1 is zero, this control routine proceeds to step S405. In step S405, the vehicle control unit 15 determines whether the second braking flag F2 is 1. If it is determined that the second braking flag F2 is 1, this control routine proceeds to step S406.

[0131] In step S406, as described above, the vehicle control unit 15 controls the acceleration and deceleration of the vehicle 1 based on the second target deceleration TD2. After step S406, this control routine ends.

[0132] On the other hand, if it is determined in step S405 that the second braking flag F2 is zero, this control routine proceeds to step S407. In step S407, the vehicle control unit 15 controls the acceleration and deceleration of the vehicle 1 based on the target acceleration TA. Specifically, the vehicle control unit 15 uses the actuator 7 to control the acceleration and deceleration of the vehicle 1 in such a way that the acceleration of the vehicle 1 becomes the target acceleration TA.

[0133] When the target acceleration TA is calculated in step S103 of Figure 5A , the vehicle control unit 15 performs the first following control. When the target acceleration TA is calculated in step S106 of Figure 5B , the vehicle control unit 15 performs the second following control. Additionally, when the target acceleration TA is inFigure 5A in step S104 of or Figure 5B when calculated in step S107, the vehicle control unit 15 performs constant speed control. After step S407, this control routine ends.

[0134] <Second Embodiment>

[0135] The driving support device according to the second embodiment is basically the same in configuration and control as the driving support device according to the first embodiment, except for the points described below. Therefore, hereinafter, the second embodiment of the present invention will be mainly described focusing on the parts different from the first embodiment.

[0136] As described above, the vehicle control unit 15 brakes the vehicle 1 when a predetermined parameter determined based on the relative relationship between the vehicle 1 and the first preceding vehicle becomes equal to or less than a threshold value. However, when the vehicle 1 changes lanes, the vehicle 1 moves in a manner that is laterally offset from the first preceding vehicle. Therefore, during a lane change, it is not necessary to ensure the same inter-vehicle distance as when following the first preceding vehicle.

[0137] Therefore, in the second embodiment, the above-mentioned threshold value during the lane change process is made smaller than the above-mentioned threshold value before the lane change. As a result, it is difficult for the vehicle 1 to brake with respect to the first preceding vehicle during the lane change process. As a result, it is possible to suppress the situation where the natural acceleration during the lane change is hindered due to the braking of the vehicle 1.

[0138] In the second embodiment, as in the first embodiment, the Figure 5A , Figure 5B , Figure 7 and Figure 8 control routine is executed. On the other hand, in the second embodiment, as the first target deceleration calculation process, instead of the Figure 6 control routine, the Figure 9 control routine is executed.

[0139] <First Target Deceleration Calculation Process>

[0140] Figure 9 is a flowchart showing a control routine of the first target deceleration calculation process in the second embodiment. This control routine is repeatedly executed by the ECU 10 at a predetermined execution interval during the automatic driving of the vehicle 1.

[0141] Steps S501 and S502 are executed in the same manner as steps S201 and S202 of Figure 6 . After step S502, in step S503, the target deceleration calculation unit 17 and Figure 5AIn step S101 similarly, it is determined whether the lane change of vehicle 1 is being implemented. When it is determined that the lane change is not being implemented, this control routine proceeds to step S504.

[0142] In step S504, the target deceleration calculation unit 17 sets the threshold value G brk as the first threshold value TH1. The first threshold value TH1 is determined in advance as a negative value in consideration of the braking performance of vehicle 1, etc. The first threshold value TH1 is set to be the same value as the threshold value G Figure 6 used for determining whether braking is required for the second preceding vehicle in step S203. brk of.

[0143] On the other hand, when it is determined in step S503 that the lane change is being implemented, this control routine proceeds to step S505. In step S505, the target deceleration calculation unit 17 sets the threshold value G brk as the second threshold value TH2. The second threshold value TH2 is determined in advance as a value smaller than the first threshold value TH1.

[0144] After step S504 or step S505, in step S506, the target deceleration calculation unit 17 determines whether the first target deceleration TD1 is below the threshold value G brk set in step S504 or step S505. When it is determined that the first target deceleration TD1 is below the threshold value G brk this control routine proceeds to step S507 and the first braking flag F1 is set to 1. On the other hand, when it is determined that the first target deceleration TD1 is greater than the threshold value G brk this control routine proceeds to step S508 and the first braking flag F1 is set to zero. After step S507 or step S508, this control routine ends.

[0145] <Third Embodiment>

[0146] The driving support device of the third embodiment is basically the same as the configuration and control of the driving support device of the first embodiment except for the points described below. Therefore, hereinafter, the third embodiment of the present invention will be described centering on the parts different from the first embodiment.

[0147] Figure 10This is a functional block diagram of the ECU 10 in the third embodiment. In the third embodiment, in addition to the vehicle control unit 15, the target acceleration calculation unit 16, and the target deceleration calculation unit 17, the ECU 10 further includes an upper limit value calculation unit 18. The vehicle control unit 15, the target acceleration calculation unit 16, the target deceleration calculation unit 17, and the upper limit value calculation unit 18 are functional modules implemented by the processor 13 of the ECU 10 executing programs stored in the memory 12 of the ECU 10.

[0148] As described above, when the vehicle control unit 15 performs a lane change of the vehicle 1 in the presence of the second preceding vehicle, it executes the second following control to control the acceleration and deceleration of the vehicle 1 so that the vehicle 1 follows the second preceding vehicle. On the other hand, the vehicle control unit 15 brakes the vehicle 1 when a predetermined parameter determined based on the relative relationship between the vehicle 1 and the first preceding vehicle becomes below a threshold value. Therefore, when accelerating the vehicle 1 to follow the second preceding vehicle, it may be necessary to brake the vehicle 1 with respect to the first preceding vehicle, and the acceleration of the vehicle 1 may be aborted during the lane change.

[0149] Thus, in the third embodiment, the upper limit value calculation unit 18 calculates the upper limit value of the target acceleration of the vehicle 1, and the target acceleration calculation unit 16 limits the target acceleration of the vehicle 1 in the second following control to the value at the upper limit position. Thereby, it is possible to suppress the case of braking with respect to the first preceding vehicle when the second following control is executed, and further, it is possible to suppress the case of unnatural acceleration during the lane change.

[0150] For example, the upper limit value calculation unit 18 calculates the allowable limit value based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle and the relative speed between the vehicle 1 and the first preceding vehicle at the start of the lane change in such a way that the vehicle 1 does not brake with respect to the first preceding vehicle during the lane change, and calculates the upper limit value as a value below the allowable limit value.

[0151] In the present embodiment, the vehicle control unit 15 brakes the vehicle 1 with respect to the first preceding vehicle when the first target deceleration calculated by the target deceleration calculation unit 17 becomes below the threshold value. Therefore, the upper limit value calculation unit 18 calculates the allowable limit value based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle and the relative speed between the vehicle 1 and the first preceding vehicle at the start of the lane change in such a way that the minimum value of the first target deceleration during the lane change is greater than the threshold value.

[0152] It is considered that when the vehicle 1 is accelerated during the lane change process, the first target deceleration (negative value) becomes the minimum before the vehicle 1 is about to move to the lane of the lane change destination. Therefore, in the present embodiment, the upper limit value calculation unit 18 calculates the allowable limit value in such a manner that the estimated value of the first target deceleration when the front end of the vehicle 1 reaches the lane boundary line (hereinafter referred to as "the first time point") is greater than the threshold value.

[0153] As described above, the threshold value G brk is determined in advance as a negative value in consideration of the braking performance of the vehicle 1 and the like. In addition, the estimated value of the first target deceleration at the first time point is represented by the left side of the following formula (6). Therefore, the upper limit value calculation unit 18 calculates the allowable limit value so as to satisfy the inequality of the following formula (6).

[0154] -1.0·ΔV1·|ΔV1| / {α·(Δd1 - d low )}>G brk …(6)

[0155] Here, as described above with respect to the above formula (4), α and d low are a predetermined coefficient and the minimum inter-vehicle distance respectively determined according to the deceleration mode of the vehicle 1. ΔV1 is the relative speed between the vehicle 1 and the first preceding vehicle at the first time point (the speed of the vehicle 1 - the speed of the first preceding vehicle), and is calculated according to the following formula (7). Δd1 is the inter-vehicle distance between the vehicle 1 and the first preceding vehicle at the first time point, and is calculated according to the following formula (8).

[0156] ΔV1 = {(a0 + a1) / 2}·Δt + ΔV0…(7)

[0157] Δd1 = Δd0 - ΔV0·Δt - (1 / 2)·{(a0 + a1) / 2}·Δt 2 …(8)

[0158] Here, ΔV0 is the relative speed between the vehicle 1 and the first preceding vehicle at the start of the lane change (the speed of the vehicle 1 - the speed of the first preceding vehicle). a0 is the acceleration of the vehicle 1 at the start of the lane change, and a1 is the acceleration of the vehicle 1 at the first time point. Δd0 is the inter-vehicle distance between the vehicle 1 and the first preceding vehicle at the start of the lane change.

[0159] Δt in the above formulas (7) and (8) is the time from the start of the lane change until the vehicle 1 moves to the lane of the lane change destination, for example, the time from the start of the lane change until the front end of the vehicle 1 reaches the lane boundary line. Δt is determined in advance as a constant, for example, 4 seconds to 8 seconds.

[0160] If it is assumed that the relative speed ΔV1 is greater than zero and β=(a0+a1) / 2, the following equation (9) is derived from the above equations (6) to (8). In addition, if the above value of β is substituted into the following equation (9), the following equation (9) is transformed into the following equation (10).

[0161]

[0162]

[0163] The variables on the right side of the above formula (10) are only the relative speed ΔV0 at the start of the lane change and the inter-vehicle distance Δd0 at the start of the lane change. Therefore, the upper limit value calculation unit 18 substitutes the relative speed and inter-vehicle distance at the start of the lane change into the right side of the above formula (10) and calculates the maximum value of the acceleration a1 that satisfies the above formula (10) as the allowable limit value.

[0164] When the allowable limit value calculated as described above is used as the target acceleration of the vehicle 1 in the second following control, it is basically unnecessary to brake the vehicle 1 to avoid a collision with the first leading vehicle in the lane change process. However, when the vehicle 1 rapidly approaches the first leading vehicle with the start of the lane change, the driver of the vehicle 1 may feel dangerous.

[0165] Generally, the closer vehicle 1 is to the first leading vehicle, the more hesitant the driver will be about sudden acceleration during lane changes. In addition, as vehicle 1 is laterally offset relative to the first leading vehicle due to the lane change, the risk of collision between vehicle 1 and the first leading vehicle is reduced. Therefore, in this embodiment, the upper limit value calculation unit 18 calculates the upper limit value as a value below the allowable limit value, and changes the difference between the allowable limit value and the upper limit value based on the inter-vehicle distance between vehicle 1 and the first leading vehicle and the lateral position of vehicle 1 during the lane change. Thereby, the driver's sense of security when implementing lane changes based on automatic driving can be improved. In addition, the lateral position of vehicle 1 refers to the position of vehicle 1 in the width direction of the lane in which vehicle 1 is traveling.

[0166] For example, the upper limit value calculation unit 18 determines the suppression gain (0 to 1) based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle during the lane change and the lateral position of the vehicle 1, and calculates the upper limit value by multiplying the suppression gain by the allowable limit value (upper limit value = allowable limit value × suppression gain). The suppression gain value increases as the inter-vehicle distance increases, and increases as the lateral position of the vehicle 1 is closer to the lane of the lane change destination.

[0167] <Upper limit value calculation process>

[0168] Figure 11It is a flowchart showing a control routine for calculating the upper limit value in the third embodiment. This control routine is repeatedly executed by the ECU 10 during the execution of the autonomous driving of the vehicle 1.

[0169] First, in step S601, the upper limit value calculation unit 18 determines whether the lane change of the vehicle 1 has started. For example, the upper limit value calculation unit 18 determines that the lane change has started when the driver agrees to the lane change via the input / output device 8, when the turn signal of the vehicle 1 is lit for the lane change, when the start of the lane change is notified to the driver via the input / output device 8, or when the steering operation for the vehicle change is started by the vehicle control unit 15.

[0170] If it is determined in step S101 that the lane change has not started, this control routine ends. On the other hand, if it is determined that the lane change has started, this control routine proceeds to step S602.

[0171] In step S602, the upper limit value calculation unit 18 calculates the allowable limit value based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle and the relative speed between the vehicle 1 and the first preceding vehicle at the start of the lane change. For example, as described above, the upper limit value calculation unit 18 calculates the maximum value of the acceleration a1 that satisfies the above formula (10) as the allowable limit value. In addition, the upper limit value calculation unit 18 may also use a map showing the relationship between "the inter-vehicle distance between the vehicle 1 and the first preceding vehicle and the relative speed between the vehicle 1 and the first preceding vehicle at the start of the lane change" and "the allowable limit value" to calculate the allowable limit value.

[0172] Next, in step S603, the upper limit value calculation unit 18 calculates the lateral position of the vehicle 1. For example, the upper limit value calculation unit 18 calculates the lateral position of the vehicle 1 as the deviation rate from the center line of the lane before the lane change.

[0173] Figure 12 It is a diagram schematically showing the change of the deviation rate during the lane change. The deviation rate OSR is calculated according to the following formula (11) based on the width W of the lane before the lane change and the deviation amount OS from the center line of the lane before the lane change. The deviation amount OS is calculated, for example, as Figure 12 shown as the distance between the center line of the lane and the front end of the vehicle 1.

[0174] OSR (%) = (2·OS / W)·100…(11)

[0175] The width W of the lane is obtained, for example, from the map information stored in the map database 5 or calculated based on the white line information detected by the object detection device 2. The deviation amount OS is calculated based on the positional relationship between the lane boundary line detected by the object detection device 2 and the vehicle 1, for example.

[0176] When not performing a lane change, the steering of vehicle 1 is controlled such that the front end (lateral center position) of vehicle 1 is located on the center line of the lane. Therefore, at the start of the lane change, the deviation amount OS becomes zero, and as a result, the deviation rate OSR becomes 0%. After that, as vehicle 1 approaches the lane of the lane change destination due to the lane change, the deviation rate becomes higher, and when the front end of vehicle 1 reaches the lane boundary line, the deviation rate becomes 100%.

[0177] After step S603, in step S604, the upper limit value calculation unit 18 calculates the inter-vehicle distance between vehicle 1 and the first preceding vehicle based on the output of the target detection device 2.

[0178] Next, in step S605, the upper limit value calculation unit 18 determines the suppression gain based on the lateral position of vehicle 1 and the inter-vehicle distance between vehicle 1 and the first preceding vehicle. For example, regarding the inter-vehicle distance between vehicle 1 and the first preceding vehicle, according to its value, it is classified into four ranges: long, medium, short, and extremely short in the order from long to short distance. And the upper limit value calculation unit 18 uses the mapping as shown in Figure 13 to determine the suppression gain. In this mapping, regarding the value of the suppression gain, the longer the inter-vehicle distance is, the larger the value is, and the higher the deviation rate is, the larger the value is.

[0179] In addition, in the mapping for determining the suppression gain, the value of the inter-vehicle distance between vehicle 1 and the first preceding vehicle itself can also be used. Also, the lateral position of vehicle 1 can be calculated as the distance between the center line of the lane and the front end or the center of gravity of vehicle 1 instead of the deviation rate.

[0180] Next, in step S606, the upper limit value calculation unit 18 calculates the upper limit value of the target acceleration by multiplying the allowable limit value by the suppression gain (upper limit value = allowable limit value × suppression gain).

[0181] Next, in step S607, the upper limit value calculation unit 18 determines whether the lane change of vehicle 1 has ended. For example, the upper limit value calculation unit 18 determines that the lane change has ended when the front end of vehicle 1 reaches the lane boundary line, when the entire vehicle 1 enters the lane of the lane change destination, when the steering operation for the lane change performed by the vehicle control unit 15 ends, or when the turn signal of vehicle 1 is turned off.

[0182] If it is determined in step S607 that the lane change has not ended, this control routine returns to step S603, and the suppression gain and the upper limit value are updated in steps S603 to S606. On the other hand, if it is determined in step S607 that the lane change has ended, this control routine ends.

[0183] In addition, step S603 may also be omitted. In step S605, the upper limit value calculation unit 18 determines the suppression gain based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle. That is, the upper limit value calculation unit 18 may also change the difference between the allowable limit value and the upper limit value based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle during the lane change process.

[0184] Alternatively, step S604 may also be omitted. In step S605, the upper limit value calculation unit 18 determines the suppression gain based on the lateral position of the vehicle 1. That is, the upper limit value calculation unit 18 may also change the difference between the allowable limit value and the upper limit value based on the lateral position of the vehicle 1 during the lane change process.

[0185] Alternatively, step S602 may also be omitted, and the allowable limit value used in step S606 is a predetermined fixed value. Alternatively, steps S603 to S605 may also be omitted. In step S606, the upper limit value calculation unit 18 sets the allowable limit value as the upper limit value. That is, it may also be that the upper limit value calculation unit 18 calculates the upper limit value based on the inter-vehicle distance between the vehicle 1 and the first preceding vehicle and the relative speed between the vehicle 1 and the first preceding vehicle at the start of the lane change in such a way that the vehicle 1 does not brake with respect to the first preceding vehicle during the lane change process.

[0186] <Target acceleration calculation process>

[0187] In addition, in the third embodiment, in the control routine of the target acceleration calculation process, instead of Figure 5B steps S105 to S107, Figure 14 steps S701 to S705 are executed.

[0188] Steps S701 to S703 are executed in the same manner as Figure 5B steps S105 to S107. After step S702 or step S703, this control routine proceeds to step S704. In step S704, the target acceleration calculation unit 16 determines whether the target acceleration calculated in step S702 or S703 is greater than the upper limit value calculated by the upper limit value calculation unit 18 through the Figure 11 control routine. If it is determined that the target acceleration is less than or equal to the upper limit value, this control routine ends.

[0189] On the other hand, if it is determined in step S704 that the target acceleration is greater than the upper limit value, this control routine proceeds to step S705. In step S705, the target acceleration calculation unit 16 changes the target acceleration to the upper limit value. That is, the target acceleration is limited to the upper limit value. After step S705, this control routine ends.

[0190] In addition, in the third embodiment, similar to the first embodiment,Figures 6 - 8 Control routine

[0191] <Fourth Embodiment>

[0192] The driving support device according to the fourth embodiment is basically the same in configuration and control as the driving support device according to the first embodiment, except for the points described below. Therefore, hereinafter, the fourth embodiment of the present invention will be described centering on the parts different from the first embodiment.

[0193] As described above, when the vehicle control unit 15 performs a lane change of the vehicle 1 in the presence of the second preceding vehicle, the second following control for controlling the acceleration and deceleration of the vehicle 1 in such a manner that the vehicle 1 follows the second preceding vehicle is executed. At this time, the target acceleration calculation unit 16 calculates the target acceleration of the vehicle 1 in such a manner that the inter-vehicle distance between the vehicle 1 and the second preceding vehicle becomes the target inter-vehicle distance.

[0194] However, there are times when a lane change of the vehicle 1 is required when the space between the second preceding vehicle and the vehicle following it is narrow. In this case, the lane change of the vehicle 1 is started in a state where the inter-vehicle distance between the vehicle 1 and the second preceding vehicle is short. As a result, when the second following control is executed, it is possible to require the vehicle 1 to decelerate suddenly simultaneously with the start of the lane change.

[0195] Therefore, in the fourth embodiment, when the inter-vehicle distance between the vehicle 1 and the second preceding vehicle at the start of the lane change is less than a preset set inter-vehicle distance, the target acceleration calculation unit 16 gradually increases the target inter-vehicle distance in the second following control from the inter-vehicle distance between the vehicle 1 and the second preceding vehicle at the start of the lane change to the set inter-vehicle distance. Thereby, even when the inter-vehicle distance from the second preceding vehicle at the start of the lane change is short, it is possible to avoid sudden deceleration of the vehicle 1 in the second following control.

[0196] <Target Inter-vehicle Distance Setting Process>

[0197] Figure 15 It is a flowchart showing a control routine of the target inter-vehicle distance setting process in the fourth embodiment. This control routine is repeatedly executed by the ECU 10 during the execution of the autonomous driving of the vehicle 1.

[0198] First, in step S801, the target acceleration calculation unit 16, similar to Figure 11 step S601 of, determines whether the lane change of the vehicle 1 has started. If it is determined that the lane change has not started, this control routine ends. On the other hand, if it is determined that the lane change has started, this control routine proceeds to step S802.

[0199] In step S802, the target acceleration calculation unit 16, similar toFigure 5B Similarly, in step S105, it is determined whether there is a second preceding vehicle. If it is determined that there is no second preceding vehicle, this control routine ends. On the other hand, if it is determined that there is a second preceding vehicle, this control routine proceeds to step S803.

[0200] In step S803, the target acceleration calculation unit 16 determines whether the inter-vehicle distance between vehicle 1 and the second preceding vehicle is less than a preset set inter-vehicle distance. As described above regarding the above formula (1), the set inter-vehicle distance is preset by the driver, automatically determined according to the speed of vehicle 1, etc., or a preset fixed value. If it is determined in step S803 that the inter-vehicle distance is equal to or greater than the set inter-vehicle distance, this control routine proceeds to step S804.

[0201] In step S804, the target acceleration calculation unit 16 sets the target inter-vehicle distance d ta to the set inter-vehicle distance d set . After step S804, this control routine ends.

[0202] On the other hand, if it is determined in step S803 that the inter-vehicle distance is less than the set inter-vehicle distance, this control routine proceeds to step S805. In step S805, the target acceleration calculation unit 16 sets the target inter-vehicle distance d ta to the current inter-vehicle distance d2 between vehicle 1 and the second preceding vehicle.

[0203] Next, in step S806, it is determined whether a small time has elapsed. The small time is preset, for example, 50 ms to 500 ms. When the small time has elapsed and the determination in step S806 is yes, this control routine proceeds to step S807.

[0204] In step S807, the target acceleration calculation unit 16 updates the target inter-vehicle distance d ta by adding a predetermined value A (for example, 1 m).

[0205] Next, in step S808, the target acceleration calculation unit 16 determines whether the target inter-vehicle distance d ta is equal to or greater than the set inter-vehicle distance d set . If it is determined that the target inter-vehicle distance d ta is less than the set inter-vehicle distance d set , this control routine proceeds to step S809.

[0206] In step S809, the target acceleration calculation unit 16 and Figure 11In step S607, similarly, it is determined whether the lane change has ended. If it is determined that the lane change has not ended, this control routine returns to step S806, and in step S807, the target inter-vehicle distance d ta is further increased.

[0207] When the result of the update is that the target inter-vehicle distance d ta reaches the set inter-vehicle distance d set at step S808, it is determined that the target inter-vehicle distance d ta is the set inter-vehicle distance d set or more. Then, this control routine proceeds to step S804. In step S804, the target acceleration calculation unit 16 sets the target inter-vehicle distance d ta to the set inter-vehicle distance d set . After step S804, this control routine ends.

[0208] On the other hand, if the lane change ends before the target inter-vehicle distance d ta reaches the set inter-vehicle distance d set , the determination in step S809 is yes, and this control routine ends.

[0209] In the fourth embodiment, similar to the first embodiment, the Figures 5A - 8 control routine is executed. At this time, the value of the target inter-vehicle distance set by the Figure 15 control routine is used to calculate the target acceleration in the second following control in Figure 5B step S106.

[0210] <Other Embodiments>

[0211] As described above, the preferred embodiments of the present invention have been explained. The present invention is not limited to these embodiments, and various modifications and changes can be made within the scope described in the claims. For example, during a lane change based on autonomous driving, the steering of vehicle 1 may be operated by the driver of vehicle 1, and only the acceleration and deceleration of vehicle 1 are controlled by the vehicle control unit 15.

[0212] In addition, the above-described embodiments can be executed in any combination. For example, when the second embodiment and the third embodiment are combined, as the value of the threshold G brk in the above formulas (6), (9), and (10), the second threshold TH2 in Figure 9 step S505 is used, and as the first target deceleration calculation process, instead of the Figure 6 control routine, the Figure 9 control routine is executed.

[0213] In addition, in the case of combining the second or third embodiment with the fourth embodiment, in the second or third embodiment, the target inter-vehicle distance in the second following control is calculated by Figure 15 the control routine of

Claims

1. A driving support device, comprising a vehicle control unit that controls the operation of its own vehicle, wherein the vehicle control unit executes a first following control for controlling the acceleration and deceleration of its own vehicle in such a manner that its own vehicle follows a first preceding vehicle traveling ahead of its own vehicle in the same lane, and when starting a lane change of its own vehicle during the execution of the first following control, during the implementation of the lane change, the first following control is prohibited, and a second following control for controlling the acceleration and deceleration of its own vehicle in such a manner that its own vehicle follows a second preceding vehicle traveling ahead of its own vehicle in the lane of the lane change destination is executed, the vehicle control unit brakes its own vehicle when a predetermined parameter determined based on the relative relationship between its own vehicle and the first preceding vehicle becomes equal to or less than a threshold value, the threshold value during the lane change is smaller than the threshold value before the lane change, the driving support device further comprises: a target acceleration calculation unit that calculates a target acceleration of its own vehicle; and an upper limit value calculation unit that calculates an upper limit value of the target acceleration, the target acceleration calculation unit limits the target acceleration in the second following control to a value equal to or less than the upper limit value, the vehicle control unit controls the acceleration and deceleration of its own vehicle in such a manner that the acceleration of its own vehicle becomes the target acceleration, the upper limit value calculation unit calculates the upper limit value as a value equal to or less than a tolerance limit value calculated based on the inter-vehicle distance between its own vehicle and the first preceding vehicle and the relative speed between its own vehicle and the first preceding vehicle at the start of the lane change in such a manner that braking of its own vehicle with respect to the first preceding vehicle is not performed during the lane change.

2. The driving support device according to claim 1, wherein the upper limit value calculation unit changes the difference between the tolerance limit value and the upper limit value based on the inter-vehicle distance between its own vehicle and the first preceding vehicle during the lane change.

3. The driving support device according to claim 1, wherein the upper limit value calculation unit changes the difference between the tolerance limit value and the upper limit value based on the lateral position of its own vehicle during the lane change.

4. The driving support device according to claim 1, wherein the target acceleration calculation unit calculates the target acceleration in the second following control in such a manner that the inter-vehicle distance between its own vehicle and the second preceding vehicle becomes a target inter-vehicle distance, and when the inter-vehicle distance between its own vehicle and the second preceding vehicle at the start of the lane change is less than a predetermined set inter-vehicle distance, the target inter-vehicle distance in the second following control is gradually increased from the inter-vehicle distance between its own vehicle and the second preceding vehicle at the start of the lane change to the set inter-vehicle distance.

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