Vehicle deceleration support device

Abstract

To provide a deceleration support device that is improved so that a driver is not disturbed by a hands-on request when decelerating a vehicle with automatic braking in such a state that a steering mode is the hands-off mode.SOLUTION: There is provided a deceleration support device which includes a control unit that is applied to a vehicle having a steering support device that requests hands-on to a driver when the vehicle speed or lateral acceleration of the vehicle exceeds a corresponding control reference value in such a state that the steering mode is the hands-off mode that performs automatic steering and decelerates the vehicle on the basis of a target deceleration rate by calculating the target deceleration rate on the basis of a travel condition of the vehicle when the vehicle deceleration is required. The control unit calculates the target deceleration rate (S60 to S80) so that neither the vehicle speed nor the lateral acceleration of the vehicle exceeds the corresponding control reference value when the vehicle deceleration is required in such a state that the steering mode is the hands-off mode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a deceleration assistance device for a vehicle such as an automobile. [Background technology]

[0002] One known deceleration support device for vehicles such as automobiles is one that automatically decelerates the vehicle to reduce its speed when it is determined that the vehicle's speed is excessively high while traveling along a lane, so that the vehicle can travel safely without straying from the lane.

[0003] For example, paragraphs

[0187] and

[0220] of the following Patent Document 1 describe a deceleration assistance device that controls vehicle speed to decrease when it is determined that the current vehicle speed is excessive compared to the speed required for the vehicle to travel safely around the curve in a situation where there is a curve in the road ahead of the vehicle. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 08-202990 Summary of the Invention

[0005] [Problem to be solved by the invention] Lane-keeping control devices are known as driving assistance devices for automobiles and other vehicles. They automatically steer the steering wheels without requiring the driver to operate the steering wheel, thereby keeping the vehicle in its lane. In these lane-keeping control devices, automatic steering is performed when the steering mode is in a hands-off mode. However, if the vehicle speed and lateral acceleration of the vehicle exceed preset reference values, the driver is notified that a hands-on steering request is required. Furthermore, if the driver is determined to be gripping the steering wheel, the steering mode is switched to a hands-on mode.

[0006] When the steering mode is the hands-off mode, the driver's ability to respond to driving operations is reduced compared to when the steering mode is the hands-on mode. Therefore, when the steering mode is the hands-off mode, it is possible to set the preset reference value to a smaller value compared to when the steering mode is the hands-on mode.

[0007] However, if the reference value is set to a small value, it becomes easier to determine that the vehicle speed and lateral acceleration of the vehicle exceed the reference value, which increases the likelihood that the driver will be notified of the hands-on requirement, increasing the risk that the driver will find the hands-on requirement annoying.

[0008] To provide an improved deceleration assist device that prevents a driver from feeling bothered by a request for hands-on steering even when a vehicle is decelerated by automatic braking in a situation where the steering mode is a hands-off mode.

[0009] [Means for solving the problems and effects of the invention] According to the present invention, the present invention is applied to a vehicle (102) equipped with a steering assist device (EPS·ECU 40, EPS device 42) configured to perform automatic steering (S80) by an automatic steering device (34) when the steering mode is a hands-off mode (S20), and to request the driver to put their hands on the steering wheel (S50) when one of the vehicle speed (V) and the lateral acceleration (Gy) of the vehicle exceeds a corresponding control reference value (Vm, Gym) in a situation where the steering mode is in the hands-off mode, and to perform automatic braking by an automatic braking device (EPS·ECU 40, EPS device 42), a driving condition detection device (target information acquisition device 16 and navigation device 80) that detects the driving condition of the vehicle, and a control unit (driving assistance ECU 10) configured to, when it is determined that the driving condition of the vehicle requires deceleration (S200, S230), calculate a target deceleration (Gbvt2, Gbgt2) based on the driving condition of the vehicle (S210, S240), and decelerate the vehicle by automatic braking so that the deceleration (Gb) of the vehicle becomes the target deceleration.

[0010] When the steering mode is hands-off mode and the vehicle is decelerated by automatic braking, the control unit (driving assistance ECU10) is configured to calculate a target deceleration (S120 to S190) so that neither the vehicle speed nor the vehicle lateral acceleration exceeds the corresponding control reference value. Furthermore, when the steering mode is hands-off mode (S120), the control unit (driving assistance ECU10) is configured to, when it determines (S130, S160) that one of the vehicle speed (V) and the vehicle lateral acceleration (Gy) is greater than the corresponding first reference value (V1, Gy1), calculate a target deceleration (Gbvt1, Gbgt1) as a target deceleration for making both the vehicle speed and the vehicle lateral acceleration equal to or less than the corresponding first reference value (S130-S190), and the first reference value (V1, Gy1) is set to a value smaller than the control reference value (Vm, Gym).

[0011] According to the deceleration assist device described above, when the steering mode is in the hands-off mode and the vehicle is decelerated by automatic braking, the target deceleration is calculated so that neither the vehicle speed nor the lateral acceleration of the vehicle exceeds the corresponding control reference value. Therefore, since neither the vehicle speed nor the lateral acceleration of the vehicle exceeds the corresponding control reference value, the vehicle speed and / or the lateral acceleration of the vehicle will not exceed the corresponding control reference value, and the driver will not be required to keep their hands on the steering wheel. This prevents the driver from feeling annoyed by the need to keep their hands on the steering wheel. Furthermore, according to the deceleration assist device, when the steering mode is a hands-off mode and it is determined that one of the vehicle speed and the lateral acceleration of the vehicle is greater than a corresponding first reference value, a target deceleration is calculated as a target deceleration for making both the vehicle speed and the lateral acceleration of the vehicle equal to or less than the corresponding first reference value, and the first reference value is smaller than the control reference value. Therefore, both the vehicle speed and the lateral acceleration of the vehicle are controlled to be equal to or less than the corresponding first reference value and do not exceed the corresponding control reference value. Therefore, the driver is not required to keep their hands on the steering wheel when the vehicle speed and / or the lateral acceleration of the vehicle exceeds the corresponding control reference value, and therefore it is possible to prevent the driver from feeling annoyed due to the need to keep their hands on the steering wheel.

[0013] [Mode of the Invention] The present invention One In one aspect, when the steering mode is a hands-on mode (S120), the control unit (driving assistance ECU10) is configured to, when it determines (S200, S230) that one of the vehicle speed (V) and the vehicle lateral acceleration (Gy) is greater than the corresponding second reference value (V2, Gy2), calculate a target deceleration (Gbvt2, Gbgt2) as a target deceleration for making both the vehicle speed and the vehicle lateral acceleration equal to or less than the corresponding second reference value, and the second reference value (V2, Gy2) is set to a value greater than the first reference value (V1, Gy1). Furthermore, in another aspect of the present invention, when the control unit (driving assistance ECU10) determines (S130) that the vehicle speed (V) is greater than a corresponding first reference value (V1) in a situation where the steering mode is hands-off mode (S120), it calculates a target deceleration (Gbvt1) based on a first vehicle speed for making the vehicle speed equal to or less than the corresponding first reference value (S140), and when the control unit (driving assistance ECU10) determines (S160) that the vehicle lateral acceleration (Gy) is greater than the corresponding first reference value (Gy1) in a situation where the steering mode is hands-off mode (S120), it calculates a target deceleration (Gbgt1) based on a first lateral acceleration for making the vehicle lateral acceleration equal to or less than the corresponding first reference value, and sets the higher of the target deceleration based on the first vehicle speed and the target deceleration based on the first lateral acceleration as the target deceleration (Gbt) when the steering mode is hands-off mode (S190).

[0014] In another aspect of the present invention, the vehicle is a vehicle in which adaptive vehicle distance control is performed.

[0015] In the above description, to facilitate understanding of the present invention, the names and / or symbols used in the embodiments described below are enclosed in parentheses for the configurations of the invention corresponding to those embodiments. However, each component of the present invention is not limited to the components of the embodiments corresponding to the names and / or symbols enclosed in parentheses. Other objects, features, and attendant advantages of the present invention will be easily understood from the following description of the embodiments of the present invention, which will be given with reference to the drawings. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a schematic configuration diagram showing a deceleration support device according to an embodiment; [Figure 2] 4 is a flowchart showing a steering mode control routine according to the embodiment. [Figure 3] 4 is a flowchart showing a deceleration support control routine according to the embodiment. [Figure 4]1A and 1B are diagrams showing a situation in which a vehicle travels straight ahead in a steering mode in a hands-off mode in the case of the prior art (A) and the case of the embodiment (B). [Figure 5] 1A and 1B are diagrams showing a situation in which a vehicle is traveling around a curve in a steering mode in a hands-off mode in the case of the prior art and in the case of an embodiment. [Figure 6] 10 is a flowchart showing a main part of a deceleration support control routine according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A deceleration assist device according to an embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

[0018] <Configuration> As shown in Fig. 1, a deceleration assistance device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driving assistance ECU 10. The vehicle 102 may be an autonomous vehicle, and includes a drive ECU 20, a braking ECU 30, an electric power steering ECU 40, and a meter ECU 50. The ECU refers to an electronic control unit that includes a microcomputer as its main component. In the following description, the electric power steering will be referred to as EPS.

[0019] The microcomputer of each ECU includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU performs various functions by executing instructions (programs, routines) stored in the ROM. Furthermore, these ECUs are interconnected via a Controller Area Network (CAN) 104 to enable data exchange (communication). Therefore, the detected values of sensors (including switches) connected to a specific ECU are transmitted to other ECUs.

[0020] The driving assistance ECU 10 is a central control device that performs driving assistance control such as deceleration assistance control, adaptive cruise control, and lane keeping control. In the embodiment, the driving assistance ECU 10 cooperates with other ECUs to perform deceleration assistance control, adaptive cruise control, and lane keeping control, as will be described in detail later. In this application, the adaptive cruise control and lane keeping control are abbreviated as ACC (Adaptive Cruise Control) and LTA (Lane Tracing Assist), respectively, as necessary.

[0021] The driving assistance ECU 10 is connected to a camera sensor 12, a radar sensor 14, and a switch 18. The camera sensor 12 and the radar sensor 14 each include a plurality of camera devices and a plurality of radar devices. The camera sensor 12 and the radar sensor 14 function as a target information acquisition device 16 that acquires information about targets around the vehicle 102.

[0022] Although not shown in the figure, each camera device of the camera sensor 12 includes a camera unit that captures images of the surroundings of the vehicle 102 and a recognition unit that analyzes image data captured by the camera unit to recognize targets such as white lines on the road and other vehicles. The recognition unit supplies information about the recognized targets to the driving assistance ECU 10 at predetermined time intervals.

[0023] Each radar device of the radar sensor 14 includes a radar transmitting / receiving unit and a signal processing unit (not shown). The radar transmitting / receiving unit emits millimeter-wave radio waves (hereinafter referred to as "millimeter waves") and receives millimeter waves reflected by a three-dimensional object (e.g., another vehicle, a guardrail, etc.) within the emission range (i.e., reflected waves). The signal processing unit supplies information indicating the distance between the vehicle and the three-dimensional object, the relative speed between the vehicle and the three-dimensional object, the relative position (direction) of the three-dimensional object with respect to the vehicle, etc. to the driving assistance ECU 10 at predetermined time intervals based on the phase difference between the transmitted millimeter waves and the received reflected waves, the attenuation level of the reflected waves, the time from transmitting the millimeter waves to receiving the reflected waves, etc. Note that a LiDAR (Light Detection and Ranging) may be used instead of or in addition to the radar sensor 14.

[0024] The switch 18 is provided in a position operable by the driver and is configured to be switched on and off by the driver. The switch 18 includes a deceleration assist switch, an ACC switch, and an LTA switch, which are not shown in Fig. 1, and when these switches are on, the deceleration assist control, ACC, and LTA are executed, respectively.

[0025] The ACC includes two types of control: constant speed cruise control and preceding vehicle following control. Constant speed cruise control is a control that adjusts the braking / driving force of the vehicle 102 so that the vehicle speed V of the vehicle 102 matches a target vehicle speed (set speed) Vt, without requiring any braking / driving operation by the driver. The preceding vehicle following control is a control that causes the host vehicle 102 to follow the preceding vehicle (the vehicle to be followed) while maintaining the inter-vehicle distance D between the host vehicle and the preceding vehicle at a target inter-vehicle distance Dt, without requiring any braking / driving operation by the driver. The preceding vehicle is a vehicle traveling immediately ahead of the host vehicle 102 in the area ahead of the host vehicle, and is determined based on target information acquired by the target information acquisition device 16. The target vehicle speed Vt and the target inter-vehicle distance Dt can be variably set by operating a setting controller not shown in FIG. 1.

[0026] LTA is a control that, when the steering mode is hands-off mode, sets a target trajectory for the vehicle and automatically steers the steering wheels using an automatic steering device so that the vehicle travels along the target trajectory. The target trajectory is set, for example, to the center line of the lane based on the white lines in the lane ahead of the vehicle 102, or to the trajectory of the preceding vehicle. The white lines in the lane are identified based on information ahead of the vehicle 102 acquired by the target information acquisition device 16. As will be described later, even if the LTA switch is on, if a predetermined condition is met, the driver is requested to put their hands on the steering wheel, and when the driver grips the steering wheel, the steering mode is switched to hands-on mode.

[0027] A drive unit 22 that accelerates the vehicle 102 by applying drive force to drive wheels not shown in Fig. 1 is connected to the drive ECU 20. The drive ECU 20 normally controls the drive unit 22 so that the drive force generated by the drive unit 22 changes in response to the driving operation by the driver, and when it receives a command signal from the driving assistance ECU 10, it controls the drive unit 22 based on the command signal. The drive unit 22 may be any drive unit known in the art.

[0028] The brake ECU 30 is connected to a brake device 32 that applies braking force to wheels (not shown in Fig. 1) to decelerate the vehicle 102 by braking. The brake ECU 30 normally controls the brake device 32 so that the braking force generated by the brake device 32 changes in response to the braking operation by the driver, and when it receives a command signal from the driving assistance ECU 10, it controls the brake device 32 based on the command signal to perform automatic braking. Thus, the brake ECU 30 and the brake device 32 function as an automatic brake device 34.

[0029] An EPS device 42 is connected to the EPS-ECU 40. The EPS-ECU 40 controls the steering assist torque and reduces the driver's steering burden by controlling the EPS device 42 in a manner known in the art based on the steering torque Ts and vehicle speed V detected by a driving operation sensor 60 and a vehicle state sensor 70, which will be described later. In addition, the EPS-ECU 40 can steer the steered wheels as needed by controlling the EPS device 42. Therefore, the EPS-ECU 40 and the EPS device 42 function as an automatic steering device 46 that automatically steers the steered wheels 44 as needed.

[0030] An alarm device 52 is connected to the meter ECU 50. When it is determined that a hands-on steering operation is required while the steering mode of the LTA is in the hands-off mode, the alarm device 52 notifies the driver that a hands-on steering operation is required. This notification may be made by displaying a warning such as "Please hold the steering wheel" on a display, and in addition to this display, a visual warning such as a warning lamp or an audible warning such as a buzzer may be issued.

[0031] The driving operation sensors 60 and the vehicle condition sensors 70 are connected to the CAN 104. Information detected by the driving operation sensors 60 and the vehicle condition sensors 70 (referred to as sensor information) is transmitted to the CAN 104. The sensor information transmitted to the CAN 104 can be used appropriately by each ECU. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted to the CAN 104 from that specific ECU.

[0032] Furthermore, the navigation device 80 is also connected to the CAN 104. The navigation device 80 includes a GPS receiver that detects the position of the vehicle 102, a storage device that stores map information and road information, and a communication device that acquires the latest map information and road information from an external device. The navigation device 80 functions as a device that acquires information about the current location of the vehicle 102, and outputs a signal indicating the current location of the vehicle on the map and information about its surroundings to the driving assistance ECU 10.

[0033] As can be seen from the above description, in the embodiment, the target information acquisition device 16 and the navigation device 80 function as a driving situation detection device when they acquire information about the roads around the vehicle 102 and the like.

[0034] In this embodiment, the ROM of the EPS-ECU 40 stores a steering mode control program, which corresponds to the flowchart shown in Fig. 2. The ROM of the driving assistance ECU 10 stores a deceleration assistance control program, which corresponds to the flowchart shown in Fig. 3.

[0035] <Steering mode control program (Fig. 2)> Next, the steering mode control in this embodiment will be described with reference to the flowchart shown in Fig. 2. The steering mode control according to the flowchart shown in Fig. 2 is repeatedly executed at predetermined time intervals by the CPU of the EPS·ECU 40 while the LTA switch is on, and ends when the LTA switch is turned off.

[0036] First, in step S10, the CPU determines whether the ACC switch is on, i.e., whether the ACC is being executed. If the CPU makes a negative determination, it proceeds to step S40 in the steering mode control, and if the CPU makes a positive determination, it proceeds to step S20 in the steering mode control.

[0037] In step S20, the CPU determines whether the steering mode is the hands-off mode. If the CPU determines that the steering mode is the hands-off mode, the steering mode control proceeds to step S70. If the CPU determines that the steering mode is the hands-off mode, the steering mode control proceeds to step S30.

[0038] In step S30, the CPU determines whether the vehicle speed V of the vehicle 102 exceeds a control reference value Vm (positive value) related to the vehicle speed. If the CPU makes a positive determination, it advances the steering mode control to step S50, and if the CPU makes a negative determination, it advances the steering mode control to step S40. The control reference value Vm may be the maximum vehicle speed allowed when the vehicle 102 is driven along a lane by automatic steering.

[0039] In step S40, the CPU determines whether the absolute value of the lateral acceleration Gy of the vehicle 102 exceeds a control reference value Gym (positive constant) related to the lateral acceleration. If the CPU makes a negative determination, it advances the steering mode control to step S80, and if the CPU makes a positive determination, it advances the steering mode control to step S50. The control reference value Gym may be the maximum absolute value of the lateral acceleration Gy that is allowed when the vehicle 102 is driven along a curved lane by automatic steering.

[0040] In step S50, the CPU determines that a need for hands-on steering has arisen when the steering mode is hands-off mode, and outputs a command signal to the meter ECU 50, thereby notifying the driver using the notification device 52 that a hands-on steering request is required.

[0041] In step S60, the CPU determines whether the driver is steering with his / her hands on. If the CPU makes a negative determination, it maintains the steering mode in the hands-off mode and returns the steering mode control to step S30. If the CPU makes a positive determination, it proceeds to step S70. In this case, for example, it may be determined that the driver is steering with his / her hands on when the touch sensor of the driving operation sensor 60 detects that the driver is gripping the steering wheel. Although not shown in FIG. 2, if a negative determination is made when the ACC switch is off, the steering mode control may return to step S40 instead of step S30.

[0042] In step S70, the CPU sets the steering mode to the hands-on mode and notifies the driver of this via the notification device 52. Therefore, LTA is not executed, and steering assist control is performed to assist the driver in manually steering the steered wheels 44, similar to lane keeping control.

[0043] In step S80, the CPU sets the steering mode to the hands-off mode and notifies the driver of this via the notification device 52. Thus, the LTA is executed, and the steering wheel 44 is automatically steered by the automatic steering device 46.

[0044] As can be seen from the above explanation, when both the vehicle speed V and the vehicle lateral acceleration Gy are equal to or less than the corresponding control reference values Vm and Gym (S30, S40), the automatic steering device 46 automatically steers the steering wheels so that the vehicle 102 travels along the lane. Therefore, the automatic steering device 46 functions as a steering assist device that performs LTA.

[0045] In addition, when the steering mode is hands-off mode (S20), if the EPS·ECU 40 determines that either the absolute value of the vehicle speed V or the lateral acceleration Gy of the vehicle 102 exceeds the corresponding control reference value, it notifies the driver of a hands-on request (S30 to S50).

[0046] <Deceleration support control program (Fig. 3)> Next, the deceleration assist control in this embodiment will be described with reference to the flowchart shown in Fig. 3. The deceleration assist control according to the flowchart shown in Fig. 3 is repeatedly executed at predetermined time intervals by the CPU of the driving assist ECU 10 while the deceleration assist switch is on, and ends when the deceleration assist switch is turned off. In the following description, the deceleration assist control will be referred to as "main control."

[0047] First, in step S110, the CPU determines whether the ACC switch and the LTA switch are on. If the CPU makes a negative determination, it temporarily terminates this control, but if the CPU makes a positive determination, it proceeds to step S120.

[0048] In step S120, the CPU determines whether the steering mode is the hands-off mode. If the CPU makes a negative determination, the control proceeds to step S200, and if the CPU makes a positive determination, the control proceeds to step S130.

[0049] In step S130, the CPU determines whether the vehicle speed V of the vehicle 102 is greater than a first reference value V1 (positive value) related to the vehicle speed. If the CPU makes a negative determination, it proceeds to step S150, and if the CPU makes a positive determination, it proceeds to step S140. The first reference value V1 is a value smaller than the control reference value Vm (step S30) related to the vehicle speed of the steering mode control.

[0050] In step S140, the CPU calculates a target deceleration Gbvt1 for preventing the vehicle speed from becoming excessive, that is, a first target deceleration Gbvt1 for keeping the vehicle speed V equal to or less than a first reference value V1 so that the vehicle speed V does not exceed the control reference value Vm. In contrast, in step S150, the CPU sets the first target deceleration Gbvt1 to 0.

[0051] In step S160, the CPU determines whether the absolute value of the lateral acceleration Gy of the vehicle 102 is greater than a first reference value Gy1 (positive constant) related to the lateral acceleration. If the CPU makes a negative determination, it proceeds to step S180, and if the CPU makes a positive determination, it proceeds to step S170. The first reference value Gy1 is smaller than the control reference value Gym (step S40) related to the lateral acceleration of the steering mode control.

[0052] In step S170, the CPU calculates a target deceleration for driving the vehicle around a curve to prevent excessive lateral acceleration, i.e., a first target deceleration Gbgt1 for keeping the absolute value of the lateral acceleration Gy equal to or less than a first reference value Gy1 so that the absolute value of the lateral acceleration Gy does not exceed a control reference value Gym. In contrast, in step S180, the CPU sets the first target deceleration Gbgt1 to 0.

[0053] In step S190, the CPU sets the larger value of the first target deceleration Gbvt1 and the first target deceleration Gbgt1 as the target deceleration Gbt of the vehicle 102. Note that MAX in step S190 in FIG. 3 and in step S260 described later means to select the larger value of the two values in parentheses.

[0054] In step S200, the CPU determines whether the vehicle speed V of the vehicle 102 is greater than a second reference value V2 (positive value) related to the ACC vehicle speed. If the CPU makes a negative determination, it proceeds to step S220, and if the CPU makes a positive determination, it proceeds to step S210. The second reference value V2 is a value greater than the first reference value V1 related to the vehicle speed (step S130), and is the target vehicle speed (set speed) Vt for the ACC constant speed cruise control. Furthermore, the second reference value V2 may be a value greater than the control reference value Vm related to the vehicle speed for the steering mode control (step S30).

[0055] As mentioned above, since the target vehicle speed Vt can be variably set, when the target vehicle speed Vt is changed, the second reference value V2 may be changed correspondingly while maintaining the above-mentioned magnitude relationship, and further the first reference value V1 and the control reference value Vm may be changed.

[0056] In step S210, the CPU calculates a second target deceleration Gbvt2 for making the vehicle speed V equal to or less than a second reference value V2 as a target deceleration for preventing the vehicle speed from becoming excessive. In contrast, in step S220, the CPU sets the second target deceleration Gbvt2 to 0.

[0057] Since the second reference value V2 is the target vehicle speed Vt for the constant speed cruise control of the ACC, steps S200 to S220 are executed as part of the ACC.

[0058] In step S230, the CPU determines whether the absolute value of the lateral acceleration Gy of the vehicle 102 is greater than a second reference value Gy2 (positive constant) related to lateral acceleration. If the CPU makes a negative determination, the control proceeds to step S250. If the CPU makes a positive determination, the control proceeds to step S240. The second reference value Gy2 is greater than the first reference value Gy1 related to lateral acceleration (step S160). Furthermore, the second reference value Gy2 may be greater than the control reference value Gym related to lateral acceleration of the steering mode control (step S40).

[0059] In step S240, the CPU calculates a second target deceleration Gbgt2 for making the absolute value of the lateral acceleration Gy equal to or less than a second reference value Gy2, as a target deceleration for allowing the vehicle to travel around a curve without excessive lateral acceleration. In contrast, in step S250, the CPU sets the second target deceleration Gbgt2 to 0.

[0060] In step S260, the CPU sets the target deceleration Gbt of the vehicle 102 to the larger value of the second target deceleration Gbvt2 and the second target deceleration Gbgt2.

[0061] In step S270, the CPU outputs a command signal to the brake ECU 30 to execute deceleration control for controlling the automatic braking device 34 so that the deceleration Gb of the vehicle 102 becomes the target deceleration Gbt.

[0062] As can be seen from the above explanation, according to the deceleration assist control of this embodiment, when the steering mode is the hands-off mode (S120), the vehicle speed V of the vehicle 102 is controlled to be substantially equal to or less than the first reference value V1 (S130 to S150). Because the first reference value V1 is smaller than the control reference value Vm (S30), the vehicle speed V of the vehicle 102 is prevented from exceeding the control reference value Vm. Therefore, a positive determination is made in step S30, and it is possible to prevent the driver from being notified of a hands-on requirement in step S50, thereby preventing the driver from feeling annoyed by being notified of a hands-on requirement.

[0063] For example, Figure 4 shows a situation in which a vehicle is traveling straight ahead in the steering mode of the hands-off mode. In the case of the conventional technology (A), if the preceding vehicle 106 suddenly accelerates, for example, the vehicle 102 also suddenly accelerates so that the inter-vehicle distance is maintained at a set value, and the vehicle speed V increases. Therefore, a hands-on request is notified every time the vehicle speed V exceeds the control reference value Vm.

[0064] In contrast, in the case of the embodiment (B), even if the preceding vehicle 106 suddenly accelerates and the vehicle 102 also tries to suddenly accelerate, the vehicle speed V is decelerated so that it becomes substantially equal to or less than the first reference value V1. Therefore, the vehicle speed V does not exceed the control reference value Vm, and therefore a hands-on request is not notified.

[0065] Furthermore, when the steering mode is the hands-off mode (S120), the absolute value of the lateral acceleration Gy of the vehicle 102 is controlled to be substantially equal to or less than the first reference value Gy1 (S160 to S180). Because the first reference value Gy1 is smaller than the control reference value Gym (S40), the absolute value of the lateral acceleration Gy of the vehicle 102 is prevented from exceeding the control reference value Gym. Therefore, a positive determination is made in step S40, and it is possible to prevent the driver from being notified of a hands-on request in step S50, thereby preventing the driver from feeling annoyed by being notified of a hands-on request.

[0066] For example, Figure 5 shows a situation in which a vehicle is traveling around a curve in the steering mode of the hands-off mode. In the case of the conventional technology (A), for example, when the vehicle 102 accelerates, the absolute values of the lateral acceleration Gy and centrifugal force Fy of the vehicle increase. Therefore, a hands-on request is notified every time the absolute value of the lateral acceleration Gy exceeds the control reference value Gym.

[0067] In contrast, in the case of embodiment (B), even in a situation where the vehicle 102 accelerates and the absolute values of the lateral acceleration Gy and centrifugal force Fy of the vehicle become high, the vehicle is decelerated so that the absolute value of the lateral acceleration Gy becomes substantially equal to or less than the first reference value Gy1. Therefore, the absolute value of the lateral acceleration Gy does not exceed the control reference value Vm, and therefore a hands-on request is not notified.

[0068] When the steering mode is the hands-on mode, the vehicle speed V of the vehicle 102 may exceed the control reference value Vm (S30), or the absolute value of the lateral acceleration Gy of the vehicle 102 may exceed the control reference value Gym (S40). However, when the steering mode is the hands-on mode, a negative determination is made in step S20 of the steering mode control, and step S50 is not executed. Therefore, the driver is not notified of the hands-on request, and the driver does not feel annoyed by being notified of the hands-on request.

[0069] According to the embodiment, a first target deceleration Gbvt1 for making the vehicle speed V equal to or less than a first reference value V1 and a first target deceleration Gbgt1 for making the absolute value of the lateral acceleration Gy equal to or less than a first reference value Gy1 are calculated. Furthermore, the higher of the first target deceleration Gbvt1 and the first target deceleration Gbgt1 is set as the target deceleration Gbt when the steering mode is the hands-off mode.

[0070] Therefore, it is possible to reliably keep both the absolute values of the vehicle speed V and the lateral acceleration Gy at or below the corresponding first reference values V1 and Gy1. Therefore, it is possible to reliably keep both the absolute values of the vehicle speed V and the lateral acceleration Gy at or below the corresponding control reference values Vm and Gym, so that even when the vehicle 102 accelerates while traveling around a curve, it is possible to effectively prevent the driver from being notified of a hands-on request.

[0071] Although the present invention has been described in detail above with reference to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the above-described embodiments, and that various other embodiments are possible within the scope of the present invention.

[0072] For example, in the above-described embodiment, if a negative determination is made in step S110, this control is temporarily terminated. However, as shown as a modified example in Fig. 6, if a negative determination is made in step S110, it is determined in step S115 whether the ACC switch is off and the LTA switch is on, and if a negative determination is made, this control is temporarily terminated, but if a positive determination is made, step S320 and subsequent steps may be executed.

[0073] Note that step S320 corresponds to step S120, steps S360 to S380 correspond to steps S160 to S180, and steps S430 to S450 correspond to steps S230 to S250. Also, in step S390, the target deceleration Gbt of the vehicle 102 is set to the first target deceleration Gbgt1, and in step S460, the target deceleration Gbt of the vehicle 102 is set to the second target deceleration Gbgt2.

[0074] According to this modification, when the ACC switch is off and the vehicle 102 is accelerating while traveling around a curve, it is possible to prevent the driver from being notified of a hands-on request.

[0075] Furthermore, in the above-described embodiment, both ACC and LTA are performed, but the deceleration assist device of the present invention may be applied to a vehicle that performs LTA but does not perform ACC. [Explanation of symbols]

[0076] 10... driving assistance ECU, 12... camera sensor, 14... radar sensor, 16... target information acquisition device, 18... switch, 20... drive ECU, 30... braking ECU, 34... automatic braking device, 40... EPS ECU, 46... automatic steering device, 50... meter ECU, 52... alarm device, 60... driving operation sensor, 70... vehicle state sensor, 100... deceleration assistance device, 102... vehicle

Claims

1. A deceleration assist device for a vehicle is applied to a vehicle equipped with a steering assist device configured to perform automatic steering by an automatic steering device when the steering mode is a hands-off mode, and to request a driver to keep their hands on the steering wheel when one of the vehicle speed and the lateral acceleration of the vehicle exceeds a corresponding control reference value when the steering mode is in the hands-off mode, the device including: an automatic braking device that performs automatic braking; a driving condition detection device that detects the driving condition of the vehicle; and a control unit configured, when it is determined that the driving condition of the vehicle is one requiring deceleration, to calculate a target deceleration based on the driving condition of the vehicle, and to decelerate the vehicle by automatic braking so that the deceleration of the vehicle becomes the target deceleration, the control unit is configured to calculate the target deceleration so that neither the vehicle speed nor the lateral acceleration of the vehicle exceeds the corresponding control reference value when decelerating the vehicle by automatic braking in a situation where the steering mode is a hands-off mode, Furthermore, when the steering mode is a hands-off mode, the control unit is configured to, when it determines that one of the vehicle speed and the lateral acceleration of the vehicle is greater than a corresponding first reference value, calculate the target deceleration as a target deceleration for making both the vehicle speed and the lateral acceleration of the vehicle equal to or less than the corresponding first reference value, and the first reference value is set to a value smaller than the control reference value.

2. In the vehicle deceleration assistance device described in claim 1, when the steering mode is a hands-on mode, the control unit is configured to, when it determines that one of the vehicle speed and the vehicle lateral acceleration is greater than a corresponding second reference value, calculate the target deceleration as a target deceleration for making both the vehicle speed and the vehicle lateral acceleration equal to or less than the corresponding second reference value, and the second reference value is set to a value greater than the first reference value.

3. 2. The vehicle deceleration assistance device according to claim 1, wherein the control unit is configured to, when the steering mode is a hands-off mode and the control unit determines that the vehicle speed is greater than the corresponding first reference value, calculate a target deceleration based on a first vehicle speed to make the vehicle speed equal to or less than the corresponding first reference value, and when the steering mode is a hands-off mode and the control unit determines that the lateral acceleration of the vehicle is greater than the corresponding first reference value, calculate a target deceleration based on a first lateral acceleration to make the lateral acceleration of the vehicle equal to or less than the corresponding first reference value, and set the higher of the target deceleration based on the first vehicle speed and the target deceleration based on the first lateral acceleration as the target deceleration when the steering mode is a hands-off mode.

4. 2. A vehicle deceleration assist system according to claim 1, wherein the vehicle is a vehicle for which adaptive vehicle-following distance control is performed.

Images