Vehicle Driving Control Device and Method

Abstract

The present invention provides an improved vehicle driving control device and method that, even when the deceleration support control switch is off, can execute deceleration support control without requiring the driver to operate a switch if the driver's alertness level falls below a threshold. [Solution] A vehicle driving control device including a deceleration control device that controls the deceleration of a vehicle, and a driving support ECU configured to execute deceleration support control by automatically decelerating the vehicle using the deceleration control device when it determines that it is necessary to decelerate the vehicle based on the vehicle's driving conditions while the deceleration support control switch is ON, wherein the driving support ECU executes deceleration support control (S200) when it determines that the driver's alertness level Aw is below a threshold Awb (S140) while the deceleration support control switch is OFF (S110).

Description

Technical Field

[0001] The present invention relates to a driving control device and method for vehicles such as automobiles, and more particularly to a driving control device and method for coping with a situation where a driver's wakefulness has decreased.

Background Art

[0002] As one of the driving control devices for vehicles such as automobiles, when it becomes difficult for the driver to continue driving due to a decrease in wakefulness or sudden illness during vehicle driving, a driving control device for dealing with driver abnormalities that automatically decelerates and stops the vehicle is known.

[0003] For example, in Patent Document 1 below, when it is determined that the driver is in an abnormal state where the ability to drive the vehicle is lost, while controlling the vehicle speed so as not to be lower than the lower limit vehicle speed determined according to the road shape, a driving control device that decelerates and stops the vehicle is described.

[0004] According to this type of driving control device, when the driver's wakefulness decreases and the driver cannot drive the vehicle, the vehicle can be automatically decelerated and stopped so that the vehicle does not continue to drive in an abnormal state.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] 〔Problems to be Solved by the Invention〕 Generally, a driver's wakefulness gradually decreases due to fatigue associated with long-term driving. Therefore, from a stage before the driver loses the ability to drive the vehicle, for example, when the driver's wakefulness drops below a preset threshold value, it is conceivable to perform deceleration assistance control that automatically decelerates the vehicle as necessary.

[0007] Deceleration support control is a control system that automatically slows down the vehicle to ensure its safety when there is an object in front of the vehicle that requires deceleration, such as a stationary vehicle. However, deceleration support control will not be executed unless the corresponding switch is turned on. Therefore, even in vehicles equipped with deceleration support control, if the deceleration support control switch is off, and the driver's alertness level is low and the driver is unable to turn the switch on, deceleration support control cannot be executed.

[0008] The present invention provides an improved vehicle driving control device and method that, even when the deceleration support control switch is off, can execute deceleration support control without requiring the driver to operate a switch if the driver's alertness level falls below a threshold.

[0009] [Means for solving the problem and the effects of the invention] According to the present invention, a vehicle driving control device (100) is provided, which includes a deceleration control device (80) for controlling the deceleration of a vehicle (102), and a control unit (driving support ECU 10) configured to perform deceleration support control (S50) by automatically decelerating the vehicle using the deceleration control device when it is determined that it is necessary to decelerate the vehicle based on the vehicle's driving conditions (S20) while the deceleration support control switch (18) is ON.

[0010] The control unit (driving support ECU 10) is configured to execute deceleration support control (S200) when it determines that the driver's level of alertness (Aw) is below a threshold (Awb) (S140) while the deceleration support control switch is off (S110).

[0011] Furthermore, according to the present invention, when it is determined that it is necessary to decelerate the vehicle (102) based on the driving conditions of the vehicle (102) while the deceleration support control switch (18) is ON (S20), a vehicle driving control method is provided which includes the step (S50) of executing deceleration support control to automatically decelerate the vehicle.

[0012] The vehicle driving control method further includes the step of executing deceleration support control (S200) when it is determined that the driver's level of alertness (Aw) is below a threshold (Awb) (S140) while the deceleration support control switch is off (S110).

[0013] According to the above-described driving control device and method, when the deceleration support control switch is ON and it is determined that the vehicle needs to be decelerated based on the vehicle's driving conditions, deceleration support control is executed to automatically decelerate the vehicle. Furthermore, when the deceleration support control switch is OFF and it is determined that the driver's level of alertness is below a threshold, deceleration support control is executed.

[0014] Therefore, even if the deceleration support control switch is off, if it is determined that the driver's alertness level is below a threshold, deceleration support control can be executed without requiring the driver to operate the switch.

[0015] [Aspects of the Invention] In one embodiment of the driving control device of the present invention, the control unit (driving support ECU 10) is configured to determine the need to reduce the vehicle speed based on the driver's driving conditions (S120), and to change at least one of the threshold and the level of alertness according to the need, such that the higher the need, the easier it is to determine that the level of alertness (Aw) is below the threshold (Awb) (S130, S135).

[0016] In one embodiment of the driving control method of the present invention, the driving control method further includes the steps of determining the need to reduce the vehicle speed based on the driver's driving conditions (S120), and changing at least one of the threshold and the level of alertness according to the need, such that the higher the need, the easier it is to determine that the level of alertness (Aw) is below a threshold (Awb).

[0017] According to the above-described apparatus and method, the need to reduce vehicle speed is determined based on the driver's driving conditions, and at least one of the threshold and the level of alertness is changed according to the need, such that the higher the need, the easier it is to determine that the level of alertness is below the threshold. Therefore, since the higher the need to reduce vehicle speed, the easier it is to determine that the level of alertness is below the threshold, deceleration support control can be started earlier when the need to reduce vehicle speed is higher, compared to when the threshold and level of alertness are not changed.

[0018] In another embodiment of the present invention, the control unit (driving support ECU 10) is configured to increase or decrease the threshold (Awb) according to the need, such that the threshold (Awb) becomes larger the greater the need (S130).

[0019] According to the above embodiment, the threshold is increased and modified according to the need, such that the threshold becomes larger the greater the need, so that the greater the need, the easier it is to determine that the level of arousal is below the threshold.

[0020] Furthermore, in another embodiment of the present invention, the control unit (driving support ECU 10) is configured to reduce or change the level of alertness (Aw) according to the need, such that the level of alertness decreases as the need for the above increases (S135).

[0021] According to the above embodiment, the level of arousal is reduced according to the need, so that the higher the need, the lower the level of arousal becomes. Therefore, the higher the need, the easier it is to determine that the level of arousal is below a threshold.

[0022] Furthermore, in another embodiment of the present invention, the control unit (driving support ECU 10) is configured to determine whether it is necessary to reduce the vehicle speed in order to drive the vehicle safely with respect to several items (A1 to A6) related to the driver's driving situation (S120), and to determine that the greater the number of items for which it is determined that it is necessary to reduce the vehicle speed, the higher the necessity is (S130, S135).

[0023] According to the above aspect, it is determined whether there is a need to reduce the vehicle speed in order to safely drive the vehicle for a plurality of items related to the driving situation of the driver. Further, the higher the number of items determined to require a reduction in vehicle speed, the higher the determination of the above necessity. Therefore, it is possible to determine whether the above necessity is high based on the number of items determined to require a reduction in vehicle speed.

[0024] Furthermore, in another aspect of the present invention, when the control unit (driving support ECU 10) determines that the arousal level (Aw) has become equal to or less than the threshold value (Awb) (S140), it proposes to the driver to execute deceleration support control (S150), and when the driver agrees to the proposal (S180), it is configured to execute deceleration support control (S200).

[0025] According to the above aspect, when it is determined that the arousal level has become equal to or less than the threshold value, the execution of deceleration support control is proposed to the driver, and when the driver agrees to the proposal, deceleration support control is executed. Therefore, it is possible to prevent the execution of deceleration support control without proposing it to the driver, and to prevent the execution of deceleration support control against the will of the driver.

[0026] Furthermore, in another aspect of the present invention, when the driver does not respond to the proposal within the reference response time (S190), the control unit (driving support ECU 10) is configured to execute deceleration support control (S200).

[0027] According to the above aspect, when the driver does not respond to the proposal within the reference response time, deceleration support control is executed. Therefore, when the reference response time elapses even if the driver does not respond to the proposal, deceleration support control can be executed.

[0028] Furthermore, in another aspect of the present invention, when the driver objects to the proposal (S160), the control unit (driving support ECU 10) is configured to reduce the increased threshold value (S170).

[0029] According to the above embodiment, when the driver objects to the proposal, the increased threshold is reduced. Therefore, when the driver objects to the proposal, the threshold is reduced, making it difficult to determine that the level of alertness is below the threshold.

[0030] Furthermore, in another embodiment of the present invention, the control unit (driving support ECU 10) is configured to determine that the level of alertness (Aw) is below a threshold (Awb) when the situation in which the level of alertness (Aw) is below a threshold (Awb) continues for a standard duration or longer (S140).

[0031] According to the above embodiment, the level of alertness is determined to be below the threshold when the situation in which the level of alertness is below the threshold continues for a standard duration or longer. Therefore, compared to the case where the level of alertness is determined to be below the threshold without considering the duration of that situation, the risk of incorrectly determining that the level of alertness is below the threshold can be reduced.

[0032] In the above description, to aid in understanding the present invention, the names and / or reference numerals used in the embodiments of the invention corresponding to those embodiments described later are indicated in parentheses. However, the components of the present invention are not limited to the components of the embodiments corresponding to the names and / or reference numerals indicated in parentheses. Other objects, other features and incidental advantages of the present invention will be readily apparent from the description of embodiments of the present invention, which will be described with reference to the following drawings. [Brief explanation of the drawing]

[0033] [Figure 1] This is a schematic diagram showing an embodiment of a vehicle driving control device according to the present invention. [Figure 2] This is a flowchart corresponding to the deceleration support control program in the first and second embodiments. [Figure 3] This is a flowchart corresponding to the driving control program when the driver's alertness level decreases in the first embodiment. [Figure 4]This is a flowchart corresponding to the deceleration control program in the event of driver abnormality in the first and second embodiments. [Figure 5] This is a flowchart corresponding to the driving control program when the driver's alertness level decreases in the second embodiment. [Figure 6] This diagram illustrates the operation of the first embodiment in a situation where the driver's level of alertness is reduced. [Figure 7] This diagram illustrates the operation of the second embodiment in a situation where the driver's level of alertness is reduced. [Figure 8] This figure shows an example of a screen displayed on the display unit during driving control when the driver's alertness level is low. [Figure 9] This figure shows an example of the temporal change of the "Yes" icon on the soft switch displayed on the indicator during driving control when the driver's alertness level is low. [Modes for carrying out the invention]

[0034] The vehicle driving control device and driving control method according to embodiments of the present invention will be described in detail below with reference to the attached figures.

[0035] As shown in Figure 1, the driving control device 100 according to an embodiment of the present invention is applied to a vehicle 102 and includes a driver assistance ECU 10. The vehicle 102 is a vehicle capable of autonomous driving and is equipped with a drive ECU 20, a brake ECU 30, an electric power steering ECU 40, and a meter ECU 50. ECU stands for Electronic Control Unit, which has a microcomputer as its main component. In the following description, electric power steering will be referred to as EPS.

[0036] Each ECU's microcomputer includes a CPU, ROM, RAM, read / write non-volatile memory (N / M), and an interface (I / F). The CPU implements various functions by executing instructions (programs, routines) stored in ROM. Furthermore, these ECUs are interconnected via CAN (Controller Area Network) 104, enabling data exchange (communication). Therefore, detection values ​​from sensors (including switches) connected to a specific ECU are transmitted to other ECUs.

[0037] The driver assistance ECU 10 is a central control unit that performs driving control for driver assistance, such as driving control when the driver's alertness level is low, deceleration support control, and deceleration control when the driver is abnormal. In the embodiment, the driver assistance ECU 10 works in cooperation with other ECUs, as will be described in detail later, to perform driving control when the driver's alertness level is low, etc. The deceleration support control in the embodiment is a control that automatically decelerates the vehicle in order to ensure the safety of the vehicle when there is a vehicle in front of the vehicle 102 that requires deceleration, such as a stationary vehicle or a curved road, that requires deceleration. However, the deceleration support control may be any control known in the art that automatically decelerates the vehicle when it is determined that it is necessary to decelerate the vehicle based on the vehicle's driving conditions.

[0038] The driver assistance ECU 10 is connected to a camera sensor 12, a radar sensor 14, a monitor camera 16, and a switch 18. The camera sensor 12 and the radar sensor 14 each include multiple camera devices and multiple radar devices, respectively. The camera sensor 12 and the radar sensor 14 function as a deceleration target detection device 15 that detects deceleration targets at least in front of the vehicle 102. The deceleration targets may include red lights, stop signs and road markings, intersections without traffic lights, stopped vehicles, curves, and preceding vehicles.

[0039] Each camera device of the camera sensor 12, although not shown in the figure, includes a camera unit that photographs the area around the vehicle 102 and a recognition unit that analyzes the image data obtained from the camera unit to recognize road markings, other vehicles, and other objects. The recognition unit supplies information about the recognized objects to the driver assistance ECU 10 at predetermined intervals.

[0040] Each radar device in the radar sensor 14 uses millimeter-wave radio waves to detect the distance between the vehicle and a three-dimensional object, the relative speed between the vehicle and the three-dimensional object, and the relative position (direction) of the three-dimensional object relative to the vehicle, and supplies this information to the driver assistance ECU 10 at predetermined intervals. Alternatively, LiDAR (Light Detection And Ranging) may be used instead of, or in addition to, the radar sensor 14.

[0041] The monitor camera 16 is mounted on the dashboard or steering column and includes a camera unit that captures the driver's face and an image processing unit that processes the image data of the driver's face obtained by the camera unit. The image processing unit supplies information of the driver's face image data to the driver assistance ECU 10 at predetermined intervals. Thus, the monitor camera 16 functions as a driver monitor camera.

[0042] The CPU of the driver assistance ECU 10 calculates the driver's alertness level Aw based on image data of the driver's face, including the driver's eye closure rate per minute, eye opening status, blinking frequency, or eye movements. The alertness level Aw decreases as the driver's attention becomes more distracted and unsuitable for driving due to sleep deprivation or other reasons. The method for calculating the alertness level is not particularly limited, and any method known in the art may be used. In addition, at least one of the driver's grip pressure on the steering wheel, pressure on the armrest, heart rate, electromyography information, and electroencephalogram pattern may be considered when calculating the alertness level. Furthermore, the alertness level Aw may be calculated by the control device of the monitor camera 16, and a signal indicating the alertness level may be input to the driver assistance ECU 10.

[0043] Switch 18 is positioned to be operable by the driver and is designed to be operated by the driver. Although not shown in Figure 1, switch 18 includes a driving control switch for when the driver's alertness is reduced, a deceleration support control switch, a deceleration control switch for when the driver is in an abnormal state, and an ACC switch. ACC is Adaptive Cruise Control and includes two types of control: constant speed driving control and preceding vehicle following control. The driver assistance ECU 10 executes the corresponding control when each switch on switch 18 is turned on, as will be described in detail later.

[0044] The drive ECU 20 is connected to a drive unit 22 that accelerates the vehicle 102 by applying driving force to the drive wheels 24. Normally, the drive ECU 20 controls the drive unit 22 so that the driving force generated by the drive unit 22 changes in accordance with the driver's driving operation, and when it receives a command signal from the driver assistance ECU 10, it controls the drive unit 22 based on the command signal.

[0045] The braking ECU 30 is connected to a braking device 32 that decelerates the vehicle 102 by applying braking force to the wheels 34. Normally, the braking ECU 30 controls the braking device 32 so that the braking force generated by the braking device 32 changes in accordance with the driver's braking operation. When it receives a command signal from the driver assistance ECU 10, it performs automatic braking by controlling the braking device 32 based on the command signal. Note that the wheels 34 include the drive wheels 24.

[0046] Therefore, the braking ECU 30 and the braking device 32 work together to function as an automatic braking system. Furthermore, the drive ECU 20, drive device 22, braking ECU 30, and braking device 32 function as a deceleration control device 80 that controls the vehicle's deceleration. Note that when braking force is applied to the wheels due to driving control when the driver's alertness level is low, brake lights (not shown in Figure 1) are illuminated.

[0047] An EPS device 42 is connected to the EPS / ECU 40. Based on the steering torque Ts and vehicle speed V detected by the driving operation sensor 60 and vehicle condition sensor 70 (described later), the EPS / ECU 40 controls the steering assist torque by controlling the EPS device 42 in a manner known in the art, thereby reducing the driver's steering burden. Furthermore, by controlling the EPS device 42, the EPS / ECU 40 can steer the steering wheels 44 as needed. Therefore, the EPS / ECU 40 and the EPS device 42 function as an automatic steering system that automatically steers the steering wheels as needed. Note that the steering wheels 44 are part of the wheels 34 and may also be drive wheels 24.

[0048] The meter ECU 50 is connected to a touch-panel display 52 and a speaker 54, which display the control status of the driver assistance ECU 10. The display 52 may be, for example, a multi-information display that displays meters and various other information, or it may be a display for a navigation system. When the display 52 receives a signal from the driver assistance ECU 10, it may display the control status, such as driving control when the driver's alertness level is low. The display 52 also displays visual warnings, and the speaker 54 emits audible warnings. Therefore, the display 52 and speaker 54 function as a notification device 56 that informs the driver of warnings and other information.

[0049] The driving operation sensor 60 and the vehicle condition sensor 70 are also connected to CAN 104. Information detected by the driving operation sensor 60 and the vehicle condition sensor 70 (referred to as sensor information) is transmitted to CAN 104. The sensor information transmitted to CAN 104 can be used as appropriate by each ECU. Note that the sensor information may be information from a sensor connected to a specific ECU and transmitted to CAN 104 from that specific ECU.

[0050] The driving operation sensor 60 includes a drive operation amount sensor for detecting the amount of operation of the accelerator pedal, a braking operation amount sensor for detecting master cylinder pressure or the force applied to the brake pedal, and a brake switch for detecting whether or not the brake pedal is operated. The driving operation sensor 60 also includes a steering angle sensor for detecting the steering angle, a steering torque sensor for detecting the steering torque, and the like.

[0051] The vehicle state sensor 70 includes a vehicle speed sensor for detecting the vehicle speed V of the vehicle 102, a longitudinal acceleration sensor for detecting the acceleration of the vehicle in the longitudinal direction, a lateral acceleration sensor for detecting the acceleration of the vehicle in the lateral direction, and a yaw rate sensor for detecting the yaw rate of the vehicle.

[0052] As will be explained in detail later, the driver assistance ECU 10 calculates the driver's alertness level Aw, and if it determines that the alertness level Aw is less than or equal to the threshold Awb when the deceleration support control switch is off and deceleration support control is not being performed, it performs deceleration support control.

[0053] Furthermore, the driver assistance ECU 10 determines the need to reduce the vehicle speed based on the driver's driving conditions, and modifies at least one of the threshold and the level of alertness so that the higher the need, the more likely it is to determine that the level of alertness Aw is below the threshold Awb. In particular, in the first embodiment described later, the driver assistance ECU 10 increases the threshold Awb, and in the second embodiment, it decreases the level of alertness Aw.

[0054] Furthermore, in the first and second embodiments, when the driver assistance ECU 10 determines that the driver's level of alertness Aw has fallen below the threshold Awb during driving control when the driver's alertness level is low, it uses the display 52 and speaker 54 to propose to the driver that deceleration support control be performed. The driver assistance ECU 10 performs deceleration support control when the driver agrees to the proposal or when the driver does not respond to the proposal within the standard response time.

[0055] [First Embodiment] In the first embodiment, the ROM of the driver assistance ECU 10 stores a deceleration support control program, a driving control program for when the driver's alertness level decreases, and a deceleration control program for when the driver is abnormal, respectively, corresponding to the flowcharts shown in Figures 2 to 4. The driving control method according to the first embodiment is executed by performing driving control for when the driver's alertness level decreases according to the flowchart shown in Figure 3.

[0056] <Deceleration support control (Figure 2)> Next, the deceleration support control in the first embodiment will be described with reference to the flowchart shown in Figure 2. The deceleration support control according to the flowchart shown in Figure 2 is repeatedly executed at predetermined intervals by the CPU of the driving support ECU 10 when the deceleration support switch of switch 18 is ON. In other words, the deceleration support control according to the flowchart shown in Figure 2 is not executed when the deceleration support switch of switch 18 is OFF. Note that the deceleration support control described below is an illustrative control and may be performed in any manner known in the art.

[0057] First, in step S10, the CPU determines whether or not ACC is being executed. If the determination is positive, this control process ends. If the determination is negative, that is, if it is determined that ACC is not being executed, this control process proceeds to step S20.

[0058] In step S20, the CPU determines whether or not there is a vehicle to be decelerated in front of the vehicle 102, that is, whether or not a vehicle to be decelerated has been detected by the vehicle to be decelerated detection device 15. If a negative determination is made, this control is terminated; if a positive determination is made, this control proceeds to step S30.

[0059] In step S30, the CPU determines whether or not a driving operation such as braking has been performed by the driver. If the determination is positive, this control is terminated; if the determination is negative, this control proceeds to step S40. If the determination is positive and deceleration control in step S50 (described later) has already been performed, the deceleration control is terminated.

[0060] In step S40, the CPU calculates a target deceleration Gbt to bring the vehicle's speed when it reaches the position of the deceleration target to a target speed Vt determined by the type of deceleration target. The target deceleration Gbt may be the deceleration required to safely drive or stop the vehicle when there is a deceleration target in front of the vehicle 102. If the deceleration target is a preceding vehicle, the position of the deceleration target is the position of the preceding vehicle when it is first detected.

[0061] The target vehicle speed Vt, which is determined by the type of deceleration target, is the speed Vf of the preceding vehicle when the deceleration target is the preceding vehicle. Furthermore, the target vehicle speed Vt is 0 when the deceleration target is a stopping object, i.e., a red light, a stop sign or road marking, or an intersection without traffic lights.

[0062] For example, if Vp is the vehicle speed of vehicle 102 when the deceleration target is detected, and Dr is the distance between vehicle 16 and the deceleration target, the target deceleration Gbt is calculated according to the following equation (1). Note that the distance Dr between vehicle 102 and the deceleration target is estimated based on the detection result of the deceleration target detection device 15. Gbt = (Vp - Vt)(Vp + Vt) / 2Dr (1)

[0063] In step S50, the CPU outputs a command signal to the deceleration control device 80 indicating the target deceleration Gbt. The deceleration control device 80 calculates the target braking force Fbt of the vehicle 102 based on the target deceleration Gbt and controls the vehicle's braking force Fb to become the target braking force Fbt, thereby controlling the vehicle's deceleration so that it reaches the target deceleration.

[0064] In step S60, the CPU determines whether the termination condition for deceleration support control has been met, that is, whether the deceleration control should be terminated. If a negative determination is made, this control is terminated; if a positive determination is made, in step S70, the deceleration control is terminated, and this control is terminated. Note that the termination condition for deceleration support control may be determined to have been met when the deceleration support switch of switch 18 is turned off, when it is determined that the vehicle speed V of vehicle 102 is less than or equal to the target vehicle speed Vt, or when it is determined that the duration of the deceleration control is te (a positive constant) or more.

[0065] <Driving control when the driver's alertness level is low (Figure 3)> Next, the driving control when the driver's alertness level decreases in the first embodiment will be described with reference to the flowchart shown in Figure 3. The driving control when the driver's alertness level decreases, as shown in the flowchart in Figure 3, is repeatedly executed at predetermined intervals by the CPU of the driver assistance ECU 10 when the switch for driving control when the driver's alertness level decreases (switch 18) is ON. At the start of the driving control when the driver's alertness level decreases, the threshold Awb is initialized to the standard value Awbs (a positive constant).

[0066] First, in step S110, the CPU determines whether ACC or deceleration support control is being executed. If the determination is positive, this control is terminated. If the determination is negative, that is, if it is determined that ACC and deceleration support control are not being executed, this control proceeds to step S120.

[0067] In step S120, the CPU determines whether it is necessary to reduce the vehicle speed V by checking whether the following six conditions A1 to A6 regarding the driver's driving situation are met. If a negative determination is made, that is, if it is determined that none of the following six conditions are met, the control proceeds to step S140. If a positive determination is made, the control proceeds to step S130. Note that the usual following distance, etc., may be determined by learning the driver's usual driving situation. Also, the items related to the driver's driving situation are not limited to the following six items. A1. The distance between your vehicle and the vehicle in front of you is smaller than the usual distance between vehicles. A2. The normal following distance between your vehicle and the vehicle in front of you is smaller than the standard following distance (a positive constant that varies depending on vehicle speed). A3. The range of vehicle speed fluctuation within the judgment time (positive constant) is greater than the standard fluctuation range. A4. The pedal operation is rougher than usual. A5. I am driving the vehicle during times when I don't normally drive it. A6. The vehicle is traveling on a road it does not normally use.

[0068] In step S130, the CPU determines that the greater the number of items for which the conditions are met, the greater the need to reduce the vehicle speed, and increases the threshold Awb accordingly. In this case, the amount by which the threshold Awb is increased for each item may be the same regardless of the item, or it may differ depending on the item.

[0069] In step S140, the CPU determines whether the driver's alertness level Aw has been determined to be below the threshold Awb for Nb (a positive integer) consecutive times or more, that is, whether the situation in which the alertness level is below the threshold has continued for a standard duration (a positive constant) or longer. If a negative determination is made, the control returns to step S110; if an affirmative determination is made, the control proceeds to step S150.

[0070] In step S150, the CPU outputs a command signal to the meter ECU 50, which, as shown in Figure 8, displays on the display 52 that it proposes the execution of deceleration support control, and also emits an audio message from the speaker 54 that proposes the execution of deceleration support control. Note that the emission of the audio message proposing the execution of deceleration support control may be omitted.

[0071] As shown in Figure 8, the display unit 52 may display, for example, a suggestion 90 such as "Do you want to perform deceleration support control?", as well as "Yes" and "No" soft switch icons 92 and 94 for the driver to respond to the suggestion by touch.

[0072] In step S160, the CPU determines whether the driver has objected to the suggestion to perform deceleration support control by touching the "No" icon 94. If the determination is negative, the control proceeds to step S180; if the determination is positive, the control proceeds to step S170.

[0073] In step S170, the CPU reduces the threshold Awb by a predetermined fixed reduction amount ΔAwb (a positive constant). Once step S170 is completed, the control returns to step S140. If the threshold Awb is reduced to less than the standard value Awbs, the threshold Awb is set to the standard value Awbs.

[0074] In step S180, the CPU determines whether the driver has agreed to the proposal to execute deceleration support control by touching the "yes" icon 92. If the determination is positive, the control proceeds to step S200; if the determination is negative, the control proceeds to step S190.

[0075] In step S190, the CPU determines whether a reference response time tr (a positive constant) has elapsed since the proposal to execute the deceleration support control in step S150 was initiated. If a negative determination is made, the control returns to step S160; if a positive determination is made, the control proceeds to step S200.

[0076] In this case, the display of the "Yes" icon 92 may be gradually changed as time elapses since the start of the proposal. For example, as shown in Figure 9, a part of the icon 92 may be highlighted, and the size of the highlighted part may increase as the elapsed time since the start of the proposal increases, until the entire icon 92 is highlighted when the elapsed time reaches the reference response time tr. When the size of the highlighted part of the icon 92 is gradually increased in this way, the driver can determine the elapsed time since the start of the proposal by the size of the highlighted part. Alternatively, instead of gradually increasing the size of the highlighted part, the color or brightness of the icon 92 may be gradually changed.

[0077] In step S200, the CPU starts the deceleration support control according to the flowchart shown in Figure 2 by switching the deceleration support switch of switch 18 to ON. Alternatively, the deceleration support control may be started without switching the deceleration support switch of switch 18 to ON.

[0078] <Deceleration control in case of driver malfunction (Figure 4)> Next, the deceleration control in the event of driver abnormality in the first embodiment will be described with reference to the flowchart shown in Figure 4. The deceleration control in the event of driver abnormality shown in the flowchart in Figure 4 is repeatedly executed at predetermined intervals by the CPU of the driver assistance ECU 10 when the driver abnormality deceleration control switch 18 is ON. Note that the driver abnormality deceleration control described below is illustrative and may be performed in any manner known in the art.

[0079] First, in step S310, the CPU determines whether the driver's alertness level Aw has been determined to be less than or equal to the first threshold Awe1 (a positive constant smaller than Awbs) for Ne1 (a positive integer) consecutive times or more. If a negative determination is made, this control is terminated; if a positive determination is made, this control proceeds to step S320.

[0080] In step S320, the CPU outputs a command signal to the meter ECU 50, which causes the display unit 52 to start displaying a warning such as "Please hold the steering wheel," and also starts emitting a warning sound from the speaker 54 or a buzzer (not shown).

[0081] In step S330, the CPU determines whether the driver's alertness level Aw has been determined to be less than or equal to the second threshold Awe2 (a positive constant smaller than Awe1) for Ne2 (a positive integer) consecutive times or more. If a negative determination is made, this control is terminated; if a positive determination is made, this control proceeds to step S340.

[0082] In step S340, the CPU outputs a command signal to the meter ECU 50, which causes the speaker 54 or buzzer (not shown) to start emitting a warning sound to the area around the vehicle 102.

[0083] In step S350, the CPU outputs a command signal to the deceleration control device 80, thereby decelerating the vehicle 102 at a deceleration rate higher than that used in the deceleration support control.

[0084] In step S360, the CPU determines whether the vehicle 102 has stopped. If the determination is negative, the control returns to step S350; if the determination is positive, the control proceeds to step S370.

[0085] In step S370, the CPU outputs a command signal to the deceleration control device 80, thereby applying braking force to the wheels for a predetermined period of time, and keeping the vehicle 102 in a stopped state.

[0086] Furthermore, in the case of driver malfunction, when controlling deceleration, in addition to decelerating the vehicle 102, the steering wheels 44 may be automatically steered by an automatic steering device so that the vehicle 102 moves to an area that is as safe as possible for itself and other vehicles.

[0087] [Second Embodiment] In the second embodiment, the ROM of the driver assistance ECU 10 stores a driving control program for when the driver's alertness level decreases, corresponding to the flowchart shown in Figure 5. The driving control method according to the second embodiment is executed by performing driving control when the driver's alertness level decreases according to the flowchart shown in Figure 5. The deceleration assistance control program and the deceleration control program for when the driver is abnormal in the second embodiment are the same as the deceleration assistance control program (Figure 2) and the deceleration control program for when the driver is abnormal (Figure 4) in the first embodiment.

[0088] <Driving control when the driver's alertness level is low (Figure 5)> As can be seen from comparing Figure 5 and Figure 3, if step S135 is executed instead of step S130, and a positive determination is made in step S160, the control is terminated without step S170 being executed. Except for these points, steps S110 to S200 are executed in the same manner as in the first embodiment.

[0089] In step S135, the CPU determines that the more items A1 to A6 are found to be met, the greater the need to reduce the vehicle speed, and reduces the Awakening Level Aw accordingly. In this case, the amount of reduction in Awakening Level Aw for each item may be the same regardless of the item, or it may differ depending on the item.

[0090] <Effects of the First and Second Embodiments> According to the first and second embodiments described above, when the deceleration support control switch (18) is ON, if it is determined that the vehicle needs to be decelerated based on the driving conditions of the vehicle 102 (S20), deceleration support control is executed to automatically decelerate the vehicle (S50). Furthermore, when the deceleration support control switch is OFF (S110), if it is determined that the driver's alertness level Aw is below the threshold Awb (S140), deceleration support control is executed (S200). Therefore, even when the deceleration support control switch is OFF, if it is determined that the driver's alertness level is below the threshold, deceleration support control can be executed without requiring the driver to operate the switch.

[0091] Furthermore, according to the first and second embodiments, the need to reduce the vehicle speed V is determined based on the driver's driving conditions for items A1 to A6 (S120), and at least one of the threshold and the level of alertness is changed according to the need, such that the higher the need, the easier it is to determine that the level of alertness Aw is below the threshold Awb (S130, S135). Therefore, the higher the need to reduce the vehicle speed, the easier it is to determine that the level of alertness is below the threshold, so compared to the case where the threshold and level of alertness are not changed, the higher the need to reduce the vehicle speed, the earlier deceleration support control can be started.

[0092] In particular, according to the first embodiment, the threshold Awb is increased according to the need to reduce the vehicle speed V, so that the threshold Awb becomes larger the greater the need to reduce the vehicle speed V (S130). Therefore, the greater the need, the easier it is to determine that the level of alertness is below the threshold.

[0093] For example, Figure 6 shows the operation of the first embodiment in a situation where the driver's alertness level Aw gradually decreases while the vehicle 102 is in motion. In Figure 6, at time t3, the alertness level Aw is below the standard threshold Awbs, and at time t4, the alertness level Aw is below the threshold Awe.

[0094] If it is determined that there is no need to reduce the vehicle speed (S120), the threshold Awb is not increased or changed, and is maintained at the standard threshold Awbs. Therefore, immediately after time t3, the execution of deceleration support control is proposed (S150), and if the driver does not object to the proposal, deceleration support control is started (S200).

[0095] In contrast, if, for example, at time t1 it is determined that there is a need to reduce the vehicle speed V (S120), the threshold Awb is increased and changed to be larger than the standard threshold Awbs. Therefore, at time t2a, which is earlier than time t3, it is determined that the level of alertness Aw is less than or equal to the standard threshold Awbs, and the execution of deceleration support control is proposed (S150). If the driver does not object to the proposal, the deceleration support control is started (S200). Thus, by increasing the threshold Awb, it becomes easier to determine that the level of alertness Aw is less than or equal to the threshold Awb, and the deceleration support control is started earlier.

[0096] Furthermore, according to the second embodiment, the level of alertness Aw decreases as the need to reduce the vehicle speed V increases (S135), so the higher the need, the easier it is to determine that the level of alertness is below a threshold.

[0097] For example, Figure 7 shows the operation of the second embodiment in a situation where the driver's alertness level Aw gradually decreases while the vehicle 102 is in motion. Similar to Figure 6, assume that at time t3, the alertness level Aw is below the standard threshold Awbs, and at time t4, the alertness level Aw is below the threshold Awe.

[0098] If it is determined that there is no need to reduce the vehicle speed (S120), the alertness level Aw is not reduced. Therefore, immediately after time t3, the execution of deceleration support control is proposed (S150), and if the driver does not object to the proposal, deceleration support control is started (S200).

[0099] In contrast, if, for example, at time t1, it is determined that it is necessary to reduce the vehicle speed (S120), the alertness level Aw is reduced, as shown by the dashed line in Figure 7. Therefore, at time t2b, which is earlier than time t3, it is determined that the alertness level Aw is below the standard threshold Awbs, and the execution of deceleration support control is proposed (S150). If the driver does not object to the proposal, the deceleration support control is started (S200). Thus, by reducing the alertness level Aw, it becomes easier to determine that the alertness level Aw is below the threshold Awb, and the deceleration support control is started earlier. Note that the alertness level Aw is not reduced in the case of deceleration control in the event of driver abnormality (Figure 4).

[0100] Furthermore, according to the first and second embodiments, it is determined whether or not it is necessary to reduce the vehicle speed V in order to drive the vehicle safely for several items A1 to A6 related to the driver's driving conditions (S120). Moreover, the more items for which it is determined that it is necessary to reduce the vehicle speed, the higher the perceived need is (S130, S135). Therefore, it is possible to determine whether or not the perceived need is high based on the number of items for which it is determined that it is necessary to reduce the vehicle speed.

[0101] Furthermore, according to the first and second embodiments, when it is determined that the alertness level Aw has fallen below the threshold Awb (S140), the driver is offered the option to perform deceleration support control (S150), and when the driver agrees to the offer (S180), the deceleration support control is performed (S200). Therefore, it is possible to prevent the deceleration support control from being performed without offering it to the driver, and to prevent the deceleration support control from being performed against the driver's will.

[0102] Furthermore, according to the first and second embodiments, if the driver does not respond to the proposal within the reference response time tr (S190), deceleration support control is executed (S200). Therefore, even if the driver does not respond to the proposal, deceleration support control can be executed once the reference response time has elapsed.

[0103] In particular, according to the first embodiment, when the driver objects to the proposal (S160), the increased threshold Awb is reduced (S170). Therefore, when the driver objects to the proposal, the threshold is reduced, making it difficult to determine that the level of alertness is below the threshold.

[0104] Furthermore, according to the first and second embodiments, when the state in which the level of arousal Aw is below the threshold Awb continues for a standard duration or longer, it is determined that the level of arousal is below the threshold (S140). Therefore, compared to the case in which the level of arousal is determined to be below the threshold without considering the duration of that state, the risk of incorrect determination of the level of arousal being below the threshold can be reduced.

[0105] Although the present invention has been described in detail above with respect to specific embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the embodiments described above, and that various other embodiments are possible within the scope of the present invention.

[0106] For example, in the first embodiment described above, the threshold Awb is increased according to the need to reduce the vehicle speed V, so that the threshold Awb becomes larger the greater the need to reduce the vehicle speed V (S130). In the second embodiment, the level of alertness is decreased according to the need to reduce the vehicle speed V, so that the level of alertness Aw becomes smaller the greater the need to reduce the vehicle speed (S135). However, the threshold may be increased according to the need to reduce the vehicle speed, so that the threshold becomes larger the greater the need to reduce the vehicle speed, and the level of alertness may also be decreased according to the need to reduce the vehicle speed, so that the level of alertness becomes smaller the greater the need to reduce the vehicle speed.

[0107] Furthermore, in the first and second embodiments described above, ACC and deceleration control in case of driver abnormality are performed. However, the vehicle driving control device of the present invention may also be applied to vehicles in which ACC or deceleration control in case of driver abnormality are not performed.

[0108] Furthermore, in the first and second embodiments described above, when the deceleration support control switch (18) is ON and it is determined that the vehicle needs to be decelerated based on the vehicle's driving conditions (S20), deceleration support control (Figure 3) is executed. Then, when the deceleration support control switch is OFF and it is determined that the driver's alertness level Aw is below the threshold Awb (S140), deceleration support control is executed (S200). However, the deceleration support control executed when the deceleration support control switch is OFF and it is determined that the driver's alertness level Aw is below the threshold Awb may differ from the deceleration support control shown in the flowchart in Figure 3. [Explanation of Symbols]

[0109] 10…Driver assistance ECU, 12…Camera sensor, 14…Radar sensor, 15…Deceleration target detection device, 16…Monitor camera, 22…Drive system, 32…Braking system, 80…Deceleration control device, 100…Driving control device, 102…Vehicle

Claims

1. A vehicle driving control device includes a deceleration control device that controls the deceleration of a vehicle, and a control unit configured to perform deceleration support control by automatically decelerating the vehicle using the deceleration control device when it determines that it is necessary to decelerate the vehicle based on the vehicle's driving conditions while the deceleration support control switch is on, The control unit is configured to execute the deceleration support control when it determines that the driver's level of alertness is below a threshold while the deceleration support control switch is off.

2. A vehicle driving control device according to claim 1, wherein the control unit is configured to determine the need to reduce the vehicle speed based on the driver's driving conditions, and to change at least one of the threshold and the level of alertness according to the need, such that the higher the need, the more likely it is to be determined that the level of alertness is below the threshold.

3. A vehicle driving control device according to claim 2, wherein the control unit is configured to increase or change the threshold value according to the need, such that the threshold value increases as the need increases.

4. A vehicle driving control device according to claim 2, wherein the control unit is configured to reduce or change the level of alertness according to the need, such that the level of alertness decreases as the need increases.

5. A vehicle driving control device according to claim 2, wherein the control unit is configured to determine whether it is necessary to reduce the vehicle speed in order to drive the vehicle safely with respect to a plurality of items relating to the driver's driving conditions, and determines that the greater the number of items for which it is determined that it is necessary to reduce the vehicle speed, the higher the necessity is.

6. A vehicle driving control device according to claim 1, wherein the control unit is configured to propose to the driver that the deceleration support control be performed when it determines that the level of alertness has fallen below the threshold, and to perform the deceleration support control when the driver agrees to the proposal.

7. A vehicle driving control device according to claim 6, wherein the control unit is configured to execute the deceleration support control when the driver does not respond to the proposal within a reference response time.

8. A vehicle driving control device according to claim 6, wherein the control unit is configured to reduce the increased threshold when the driver objects to the proposal.

9. A vehicle driving control device according to claim 1, wherein the control unit is configured to determine that the level of alertness is below the threshold when the state in which the level of alertness is below the threshold continues for a standard duration or longer.

10. A vehicle driving control method that includes the step of executing deceleration support control to automatically decelerate the vehicle when it is determined that it is necessary to decelerate the vehicle based on the vehicle's driving conditions while the deceleration support control switch is ON, Furthermore, a vehicle driving control method that includes the step of executing the deceleration support control when it is determined that the driver's level of alertness is below a threshold while the deceleration support control switch is off.

11. A vehicle driving control method according to claim 10, further comprising the steps of: determining the need to reduce the vehicle speed based on the driver's driving conditions; and changing at least one of the threshold and the level of alertness according to the need, such that the higher the need, the easier it is to determine that the level of alertness is below the threshold.

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