Driving support device

Abstract

To provide a driving support apparatus capable of reducing a possibility of a driver feeling uncomfortable when canceling deceleration assist control based on accelerator pedal (AP) operation by the driver.SOLUTION: A driving support apparatus includes: a surrounding sensor capable of acquiring surrounding information on a three-dimensional object around a vehicle and a road marking ahead of the vehicle; a vehicle state sensor capable of acquiring vehicle state information on a plurality of types of vehicle states in response to driving operation by a driver, including an AP operation amount in response to the driver's AP operation as one of the vehicle states; and a control unit configured to execute deceleration assist control to assist deceleration by automatically applying a braking force to the vehicle in the case that a predetermined start condition is satisfied, and to cancel the deceleration assist control by reducing the braking force in the case that a cancel condition which is satisfied when the AP operation is performed during execution of the deceleration assist control is satisfied. When the cancel condition is satisfied, the control unit reduces the braking force on the basis of the surrounding information and the vehicle state information.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a driving support device capable of executing deceleration support control for assisting the deceleration of a vehicle by automatically applying braking force to the vehicle.

Background Art

[0002] Patent Document 1 describes a driving support device that cancels the control when an accelerator pedal operation by the driver of the vehicle is detected during the execution of deceleration support control. When the amount of accelerator pedal operation is large, this driving support device cancels the deceleration support control by quickly reducing the deceleration control amount (braking force) compared to the case where the amount of accelerator pedal operation is small.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] According to the driving support device of Patent Document 1, the driver may feel discomfort when the deceleration support control is canceled. That is, when the driver's pedal operation becomes rough due to fatigue or the like, the amount of accelerator pedal operation may become large contrary to the driver's intention. For example, in a scene where the need for acceleration is relatively low, cases include stepping on the accelerator pedal deeper than intended when trying to step on it lightly, or accidentally stepping on the accelerator pedal instead of the brake pedal. In such cases, although the driver expects the deceleration support control to be released gently or the deceleration support control to continue, the deceleration control amount decreases quickly (i.e., the deceleration feeling drops quickly), so the driver may feel discomfort.

[0005] The present invention has been made to address the above-described problems. That is, one of the objects of the present invention is to provide a driving support device capable of reducing the possibility that a driver feels discomfort when canceling deceleration support control based on an accelerator pedal operation by the driver.

[0006] The driving support device according to the present invention (hereinafter referred to as "the device of the present invention") includes a surrounding sensor capable of detecting a three-dimensional object existing around the vehicle and road markings in front of the vehicle and acquiring information on the detected three-dimensional object and road markings as surrounding information, and a vehicle state sensor capable of detecting a plurality of types of vehicle states corresponding to driving operations by the driver of the vehicle and acquiring information on the detected vehicle states as vehicle state information, the vehicle state sensor including an accelerator pedal operation amount corresponding to an accelerator pedal operation by the driver as one of the detected vehicle states. When a predetermined start condition is satisfied, a deceleration support control is executed to assist in decelerating the vehicle by automatically applying a braking force to the vehicle, and when a release condition that is satisfied when the accelerator pedal operation is performed during the execution of the deceleration support control is satisfied, the deceleration support control is canceled by reducing the braking force so that the deceleration of the vehicle becomes zero. The driving support device is configured to include a control unit configured as described above. When the release condition is satisfied, the control unit is configured to reduce the braking force based on the surrounding information and the vehicle state information.

[0007] When the device of the present invention cancels the deceleration support control due to the satisfaction of the release condition (a condition that is satisfied when an accelerator pedal operation is performed by the driver during the execution of the deceleration support control), the device is configured to reduce the braking force based on the surrounding information and the vehicle state information. Therefore, compared with a configuration in which the braking force is reduced only based on the accelerator pedal operation amount, it is possible to appropriately reduce the braking force. Accordingly, even when the accelerator pedal operation amount becomes large contrary to the driver's intention, it is possible to reduce the possibility that the driver feels discomfort when the deceleration support control is canceled.

[0008] In one aspect of the present invention, when the release condition is satisfied, the control unit is configured to linearly decrease the braking force.

[0009] In one aspect of the present invention, when the release condition is satisfied, the control unit calculates an acceleration necessity degree, which is an index indicating the level of necessity for acceleration of the vehicle, based on the surrounding information and the vehicle state information, and when the acceleration necessity degree is low, the absolute value of the decreasing gradient of the braking force is made smaller than a predetermined reference gradient regardless of the value of the accelerator pedal operation amount, and when the acceleration necessity degree is high, the absolute value of the decreasing gradient is made larger when the accelerator pedal operation amount is large than when the accelerator pedal operation amount is small.

[0010] According to this configuration, in a scene where the necessity for acceleration is low, the braking force decreases relatively gently regardless of the value of the accelerator pedal operation amount. On the other hand, in a scene where the necessity for acceleration is high, the braking force decreases relatively steeply when the accelerator pedal operation amount is large compared to when the accelerator pedal operation amount is small. Therefore, a vehicle behavior that conforms to the driver's feeling can be realized.

[0011] In one aspect of the present invention, the vehicle state sensor includes, as the detected vehicle state, a steering angle corresponding to a steering operation by the driver and an operation state of a direction indicator corresponding to a direction indicator operation by the driver, and the control unit is configured to determine that the acceleration necessity degree is low when a predicted arrival time of the vehicle to a preceding vehicle or a traffic signal or a road sign that requires the vehicle to stop is equal to or less than a predetermined first time threshold, the magnitude of the steering angle is equal to or less than a predetermined first steering angle threshold, and the direction indicator is not operated.

[0012] According to this configuration, when the necessity for acceleration is low, it is determined that the acceleration necessity degree is low, so that the reliability of the acceleration necessity degree can be ensured.

[0013] In one aspect of the present invention, the vehicle state sensor includes, as the detected vehicle state, a steering angle corresponding to a steering operation by the driver and an operation state of a direction indicator corresponding to a direction indication operation by the driver. The control unit is configured to determine that the acceleration necessity is high in any of the following cases: a first case where a predicted arrival time of the vehicle to a preceding vehicle or a traffic signal or a road sign that requests a stop of the vehicle exceeds a predetermined second time threshold; a second case where there is no preceding vehicle, a magnitude of the steering angle is equal to or less than a predetermined first steering angle threshold, and the direction indicator is not operated; or a third case where there is a preceding vehicle, a magnitude of the steering angle exceeds a predetermined second steering angle threshold that is larger than the first steering angle threshold, and the direction indicator is operated in a direction corresponding to the steering operation.

[0014] According to this configuration, when the necessity of acceleration is high, it is determined that the acceleration necessity is high, so that the reliability of the acceleration necessity can be ensured.

[0015] In the above description, for the purpose of assisting the understanding of the invention, reference numerals used in the embodiments are attached in parentheses to the constituent elements of the invention corresponding to the embodiments. However, each constituent element of the invention is not limited to the embodiments defined by the reference numerals.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0017] Hereinafter, a driving support device according to an embodiment of the present invention (hereinafter, also referred to as "this embodiment device") will be described with reference to the drawings. This embodiment device is mounted on a vehicle. As shown in FIG. 1, this embodiment device includes a driving support ECU 10, and a surrounding sensor 20, a vehicle state sensor 30, a driving device 40, a braking device 50, and a steering device 60 connected thereto. The driving support ECU 10 includes a microcomputer as a main part. The microcomputer includes a CPU, a ROM, a RAM, an interface (I / F), etc., and the CPU realizes various functions by executing instructions (programs, routines) stored in the ROM. Hereinafter, the vehicle on which this embodiment device is mounted is referred to as "own vehicle".

[0018] The driving support ECU 10 is configured to acquire signals output from the sensors 20 and 30 every time a predetermined time elapses, and control the devices 40, 50, and 60 based on the acquired signals. Hereinafter, the driving support ECU 10 is also simply referred to as "ECU 10".

[0019] The surrounding sensor 20 includes a camera sensor 21 and a radar sensor 22. The camera sensor 21 is installed on the back surface of the inner mirror of the host vehicle. The camera sensor 21 captures an image of the scenery in front of the host vehicle, and based on the captured image data, detects a three-dimensional object existing in front of the host vehicle. The three-dimensional object includes a stationary object and a moving object. The stationary object is, for example, a traffic signal, a road sign, and a structure (such as a guardrail, a curb, and a median strip), and the moving object is, for example, another vehicle. When detecting a three-dimensional object, the camera sensor 21 calculates the relative relationship between the host vehicle and the three-dimensional object (the relative position and relative speed of the three-dimensional object with respect to the host vehicle). In particular, when the detected three-dimensional object is a traffic signal, the camera sensor 21 extracts the traffic signal existing in front of the driving route of the host vehicle from the detected traffic signals, and performs well-known image processing on the extracted traffic signal to identify the type of the lighting display (typically, the color of the light or the arrow signal) of the traffic signal.

[0020] In addition, the camera sensor 21 detects the road surface display in front of the host vehicle based on the image data. The road surface display includes road markings (such as a stop line and a road surface arrow) and lane lines. The camera sensor 21 calculates the shape of a lane (the area between two adjacent lane lines) based on the lane lines.

[0021] The radar sensor 22 is installed at the left and right corner parts of the front end of the host vehicle. The radar sensor 22 irradiates radio waves in the millimeter wave band to the surroundings of the host vehicle (more specifically, the range from the side to the front of the host vehicle). When a three-dimensional object exists within the irradiation range of the radio waves, the radar sensor 22 receives the reflected wave from the three-dimensional object. The radar sensor 22 calculates the relative relationship between the host vehicle and the three-dimensional object based on the irradiation timing of the radio waves and the reception timing, etc. In other words, the radar sensor 22 detects a three-dimensional object existing around the host vehicle.

[0022] The surrounding sensor 20 acquires the information regarding the three-dimensional object obtained by the camera sensor 21 and the radar sensor 22 respectively as surrounding information, and outputs the information to the ECU 10.

[0023] The vehicle state sensor 30 includes an accelerator pedal (AP) operation amount sensor 31, a vehicle speed sensor 32, an acceleration sensor 33, a steering angle sensor 34, and a turn signal sensor 35. The AP operation amount sensor 31 detects the accelerator pedal (AP) operation amount corresponding to the operation of the accelerator pedal (AP) by the driver. In the present embodiment, the stroke amount of the accelerator pedal is detected as the AP operation amount. However, for example, in addition to or instead of the stroke amount of the accelerator pedal, the depression speed of the accelerator pedal may be detected as the AP operation amount.

[0024] The vehicle speed sensor 32 detects the speed (vehicle speed) of the host vehicle. The acceleration sensor 33 detects the longitudinal acceleration (acceleration in the longitudinal direction) and the lateral acceleration (acceleration in the lateral direction orthogonal to the longitudinal direction) of the host vehicle. The steering angle sensor 34 detects the steering angle corresponding to the steering operation (operation of the steering wheel) by the driver. In the present embodiment, the steering angles when the steering wheel is steered clockwise and counterclockwise are defined as positive and negative values, respectively. The turn signal sensor 35 detects the operation state of the direction indicator (the turn signal lever WL in the present embodiment) corresponding to the direction indicator operation by the driver. Here, the operation state of the turn signal lever WL includes "the turn signal lever WL is operated in the right direction", "the turn signal lever WL is operated in the left direction", and "the turn signal lever WL is not operated".

[0025] The values and operation states detected by these sensors 31 to 35 all correspond to an example of the "vehicle state". That is, the vehicle state sensor 30 detects a plurality of types of vehicle states corresponding to the driving operations by the driver. The vehicle state sensor 30 acquires information on the detected vehicle state as vehicle state information and outputs the information to the ECU 10.

[0026] The drive device 40 is a device for applying a driving force for driving the host vehicle to its drive wheels. The ECU 10 controls the driving force applied to the drive wheels by controlling the operation of the drive device 40. Note that the type of the host vehicle is not particularly limited, and for example, it may be an engine vehicle, a hybrid vehicle (HEV: Hybrid Electric Vehicle), a plug-in hybrid vehicle (PHEV: Plug-in Hybrid Electric Vehicle), a fuel cell vehicle (FCEV: Fuel Cell Electric Vehicle), or a battery electric vehicle (BEV: Battery Electric Vehicle), etc.

[0027] The braking device 50 is a device for applying a braking force for braking the host vehicle to its wheels. The ECU 10 controls the braking force applied to the wheels by controlling the operation of the braking device 50.

[0028] The steering device 60 is a device for applying a steering torque for steering the steered wheels of the host vehicle to a steering mechanism (not shown). The ECU 10 controls the steering torque applied to the steering mechanism by controlling the operation of the steering device 60.

[0029] The ECU 10 executes deceleration assistance control when a predetermined start condition is satisfied. The start condition varies depending on the type of the three-dimensional object (hereinafter also referred to as the "control target") that is the target of the deceleration assistance control and the type of the situation (hereinafter also referred to as the "control situation") in which the deceleration assistance control is required. This will be specifically described below.

[0030] The start condition 1, which is the start condition when the control target is the preceding vehicle, is satisfied when the following conditions 1a to 1c are satisfied. (Condition 1a) The preceding vehicle is detected. (Condition 1b) The vehicle speed v of the host vehicle is greater than the vehicle speed of the preceding vehicle. (Condition 1c) The TTC for the control target is equal to or less than a predetermined threshold value TTCth.

[0031] Here, TTC is an abbreviation for Time To Collision, which means the time predicted to be required until the host vehicle collides with (reaches) the control target. TTC can be calculated by dividing the distance to the control target by the relative speed of the host vehicle with respect to the control target. When Start Condition 1 is satisfied, ECU 10 sets the vehicle speed of the preceding vehicle to the target vehicle speed vtgt, and performs deceleration assistance control so that v = vtgt at a position a predetermined distance d1 in front of the preceding vehicle (in other words, so that the relative speed becomes zero).

[0032] Start Condition 2, which is the start condition when the control target is a "traffic signal with a red light display" or a "road sign requiring a full stop of the host vehicle", is satisfied when the following Conditions 2a and 2b are satisfied (hereinafter, the above traffic signal is also simply referred to as a "red traffic signal", and the above road sign is also simply referred to as a "full stop sign"). (Condition 2a) A red traffic signal or a full stop sign is detected. (Condition 2b) The TTC for the control target is equal to or less than a predetermined threshold value TTCth.

[0033] When Start Condition 2 is satisfied, ECU 10 sets the vehicle speed zero to the target vehicle speed vtgt, and performs deceleration assistance control so that v = vtgt at a position a predetermined distance d2 in front of the red traffic signal or the full stop sign (typically, the position of the stop line). Note that the threshold value TTCth of Condition 1c and the TTCth of Condition 2b may be the same or different.

[0034] Start Condition 3, which is the start condition when the control situation is "before a right or left turn at an intersection", is satisfied when all of the following Conditions 3a to 3c are satisfied. Here, "before a right or left turn at an intersection" means a situation where the host vehicle is traveling with the intention of making a right or left turn at the intersection ahead. (Condition 3a) An intersection (traffic signal or intersection sign) is detected. (Condition 3b) The turn signal lever WL is being operated in the left direction and the left lateral distance dll (described later) is less than or equal to a predetermined distance threshold dlth, or the turn signal lever WL is being operated in the right direction and the right lateral distance dlr (described later) is less than or equal to a predetermined distance threshold dlth. (Condition 3c) The vehicle speed v is greater than a predetermined recommended vehicle speed vr1 (described later).

[0035] The left lateral distance dll and the right lateral distance dlr in Condition 3b are the distances in the lane width direction from the host vehicle to the left and right structures, respectively. The distance threshold dlth can be set in advance based on the maximum value of the left lateral distance dll (or the right lateral distance dlr) when the host vehicle is traveling in the leftmost (or rightmost) lane. Also, the recommended vehicle speed r1 in Condition 3c is the vehicle speed recommended to achieve a safe left or right turn at an intersection. When Conditions 3a to 3c are satisfied, it is highly likely that the host vehicle is traveling in the leftmost or rightmost lane to make a left or right turn at an intersection. When Start Condition 3 is satisfied, the ECU 10 sets the recommended vehicle speed vr1 as the target vehicle speed vtgt and executes deceleration assistance control so that v = vtgt at a position a predetermined distance d3 before the intersection. When a road surface arrow (strictly speaking, a road surface arrow indicating the traveling direction corresponding to the operation direction of the turn signal lever WL) is detected by the camera sensor 21, it is considered that the host vehicle is more likely to intend to make a left or right turn at the intersection compared to the case where no road surface arrow is detected. For this reason, in such a case, the ECU 10 may be configured to increase the magnitude of the deceleration by the deceleration assistance control.

[0036] Start Condition 4, which is the start condition when the control situation is "driving on a curved road", is satisfied when the following Conditions 4a and 4b are satisfied. (Condition 4a) The lateral acceleration Gl of the host vehicle exceeds a predetermined lateral acceleration threshold Glth. (Condition 4b) The vehicle speed v is greater than a predetermined recommended vehicle speed vr2 (described later).

[0037] The lateral acceleration threshold Glth of condition 4a is a value that can determine whether the driving lane of the host vehicle is curved or straight, and can be preset based on the distribution data of the lateral acceleration Gl when driving on lanes with various curvatures at vehicle speeds within a predetermined range. The recommended vehicle speed vr2 of condition 4b is the vehicle speed recommended to achieve safe driving on a curved road. The recommended vehicle speed vr2 may be a variable value according to the curvature of the curved road. When the start condition 4 is satisfied, the ECU10 sets the recommended vehicle speed vr2 as the target vehicle speed vtgt, and executes deceleration assistance control so that v = vtgt with a deceleration within a preset deceleration range.

[0038] The cancellation condition of the deceleration assistance control is satisfied when an AP operation is performed by the driver during the execution of the control. When the cancellation condition is satisfied, the ECU10 cancels the deceleration assistance control by reducing the braking force (strictly speaking, the magnitude of the braking force) so that the deceleration of the host vehicle becomes zero. At this time (when the cancellation condition is satisfied), the ECU10 sets the decrease gradient of the braking force (strictly speaking, the absolute value of the decrease gradient) based not only on the AP operation amount but also on the surrounding information and vehicle state information, and reduces the braking force according to the set decrease gradient. Fig. 2 shows the setting patterns of the absolute value |s| of the decrease gradient of the braking force. The horizontal axis of the graph in Fig. 2 represents the time t, and the vertical axis represents the braking force Fb. In the graphs of Fig. 2, the deceleration assistance control has started at time t1 in each case. The braking force increases linearly from time t1 to time t2, and is maintained at a constant value from time t2 to time t3. Also, the cancellation condition is satisfied at time t3, and the braking force decreases linearly at a predetermined decrease gradient respectively. The absolute value |s| of the decrease gradient is set to s1, s2, and s3 in pattern 1, pattern 2, and pattern 3 respectively. s1 to s3 are values preset based on experiments or simulations, and the relationship s1 < s2 < s3 holds. According to this configuration, the braking force decreases most gently (over time) in pattern 1 and most steeply (rapidly) in pattern 3 (t4 < t5 < t6).

[0039] When the release condition is satisfied, the ECU 10 calculates the required degree of acceleration. The required degree of acceleration is an index indicating the level of necessity for the acceleration of the host vehicle, and in this embodiment, it is classified into three types: low, medium, and high (described later). Based on the required degree of acceleration and the AP operation amount, the ECU 10 sets the absolute value |s| of the braking force reduction gradient as shown in the matrix of FIG. 3. According to this matrix, when the required degree of acceleration is "low", the absolute value |s| of the reduction gradient is set to s1 regardless of the value of the AP operation amount. On the other hand, when the required degree of acceleration is "high", when the AP operation amount is equal to or less than a predetermined first threshold value APth1, |s| is set to s1, when the AP operation amount is greater than the first threshold value APth1 and equal to or less than a predetermined second threshold value APth2 (>APth1), |s| is set to s2, and when the AP operation amount is greater than the second threshold value APth2, |s| is set to s3. That is, when the required degree of acceleration is "high", the absolute value |s| of the reduction gradient is set to a larger value step by step as the AP operation amount increases. In contrast, when the required degree of acceleration is "medium", when the AP operation amount is equal to or less than the first threshold value APth1, |s| is set to s1, and when the AP operation amount is greater than the first threshold value APth1, |s| is set to s2. According to this configuration, in a scene where the required degree of acceleration is low, the braking force decreases gently, while in a scene where the required degree of acceleration is high, the reduction gradient of the braking force becomes steep step by step as the AP operation amount increases. Therefore, it is possible to reduce the possibility that the driver feels discomfort when releasing the deceleration support control, and the deceleration support control can be released in a manner that conforms to the driver's feeling.

[0040] Note that when the release condition is satisfied, the ECU 10 releases the deceleration support control and executes an accelerator override based on the AP operation amount. The accelerator override is a control for controlling the driving force so that the acceleration of the host vehicle matches the required acceleration by the driver's AP operation.

[0041] The value s2 corresponds to an example of a "reference gradient". In the present embodiment, the value s2 is a value corresponding to the absolute value of the decreasing gradient set when the AP operation amount is medium (i.e., APth1 < AP operation amount ≤ APth2) in a conventional driving support device (i.e., a device configured to decrease the braking force based only on the AP operation amount when releasing the deceleration support control).

[0042] Also, the absolute value |s| of the decreasing gradient of each cell of the matrix is not limited to the setting shown in FIG. 3. For example, in cells c1 and c2, |s| = s3 may be set instead of |s| = s2.

[0043] Next, the acceleration necessity will be described. The method for determining the acceleration necessity differs depending on the type of the control target and the type of the control situation. Specific description will be given below. Since the calculation of the acceleration necessity is performed during the execution of the deceleration support control, descriptions of obvious conditions (for example, the condition that the control target is detected) are omitted except when particularly necessary.

[0044] 1. When the control target is the preceding vehicle When the following condition 1d is satisfied, the ECU10 determines that the acceleration necessity is "low" (the acceleration necessity is low). Condition 1d is satisfied when all of conditions 1d-1 to 1d-3 are satisfied. (Condition 1d) (Condition 1d-1) The TTC for the control target is less than or equal to a predetermined first threshold value TTCth1. (Condition 1d-2) The magnitude of the steering angle θ is less than or equal to a first steering angle threshold value θth1. (Condition 1d-3) The turn signal lever WL is not operated. Note that the first threshold value TTCth1 satisfies TTCth1 < TTCth.

[0045] Case 1 in FIG. 4 illustrates a situation in which deceleration assist control is being executed with a preceding vehicle Vp as the control target. The symbol L represents the driving lane. Although deceleration assist control is being executed at this point, the distance to the preceding vehicle Vp is still relatively short, and the vehicle speed v is greater than the vehicle speed vp (the vehicle speed of the preceding vehicle Vp), so TTC≦TTCth1 is satisfied. Furthermore, the steering angle θ≦first steering angle threshold θth1 is satisfied, and the turn signal lever WL is not operated. In this situation, if the driver accidentally depresses the accelerator pedal instead of the brake pedal to maintain a sufficient distance, the release condition is satisfied, and the ECU 10 calculates the degree of acceleration necessity. In Case 1, all of Conditions 1d-1 to 1d-3 are satisfied. Therefore, the ECU 10 determines that the degree of acceleration necessity is “low.” In this case, the braking force reduction gradient |s| is set to s1 regardless of the AP operation amount, so the braking force decreases gradually (the deceleration sensation decreases gradually). Therefore, even if the AP operation amount becomes large against the driver's intention due to an erroneous pedal depression, the possibility that the driver will feel uncomfortable can be reduced.

[0046] Furthermore, if any of the following conditions 1e, 1f, and 1g is satisfied, the ECU 10 determines that the degree of acceleration necessity is "high." Condition 1f is satisfied when all of conditions 1f-1 to 1f-3 are satisfied. Condition 1g is satisfied when all of conditions 1g-1 to 1g-3 are satisfied.

[0047] (Condition 1e) The TTC for the control object exceeds a predetermined second threshold TTCth2. The second threshold TTCth2 is <TTCth2<TTCthを満たす。「条件1gが成立した場合」は、「第1の場合」の一例に相当する。

[0048] (Condition 1f) (Condition 1f-1) No preceding vehicle is detected. (Condition 1f-2) The magnitude of the steering angle θ is equal to or smaller than a first steering angle threshold θth1. (Condition 1f-3) The turn signal lever WL is not operated. Note that "when Condition 1f is satisfied" corresponds to an example of "the second case".

[0049] Case 3 in FIG. 5 shows a scene where deceleration assistance control is being executed as a result of the host vehicle V traveling on the travel lane L at a relatively high speed. The vehicle Vp that was traveling in front of the host vehicle V is attempting to change lanes to the adjacent lane Ll because the host vehicle V is approaching from behind. The ECU 10 is configured not to detect the vehicle that was traveling in front of the host vehicle V as the preceding vehicle when it starts to leave the travel lane. Therefore, in Case 3, no preceding vehicle is detected. Note that the preceding vehicle can be defined as a vehicle whose inter-vehicle distance is equal to or less than a predetermined distance threshold di. Also, in Case 3, the steering angle θ ≤ the first steering angle threshold θth1 holds, and the turn signal lever WL is not operated. In this scene, when the driver depresses the accelerator pedal for the purpose of accelerating the host vehicle V, the release condition is satisfied, so the ECU 10 calculates the acceleration necessity. In Case 3, all of Conditions 1f-1 to 1f-3 are satisfied. Therefore, the ECU 10 determines that the acceleration necessity is "high". In this case, the decreasing gradient |s| of the braking force increases stepwise according to the AP operation amount (see FIG. 3). Accordingly, the driver can obtain a deceleration feeling corresponding to his / her AP operation. As a result, a smooth accelerator override can be realized.

[0050] (Condition 1g) (Condition 1g-1) A preceding vehicle is detected. (Condition 1g-2) The magnitude of the steering angle θ exceeds the second steering angle threshold θth2. (Condition 1g-3) The turn signal lever WL is operated in the direction corresponding to the steering operation. Note that the second steering angle threshold θth2 is larger than the first steering angle threshold θth1. "When Condition 1g is satisfied" corresponds to an example of "the third case".

[0051] Case 4 in FIG. 5 shows a scene where the host vehicle V is traveling on the travel lane L at a relatively high speed, and deceleration assistance control is being executed. In this scene, when the driver depresses the accelerator pedal for the purpose of overtaking the preceding vehicle Vp, since the release condition is satisfied, the ECU 10 calculates the acceleration necessity level. Before depressing the accelerator pedal, the driver operates the turn signal lever WL in the right direction and performs a steering operation in the right direction. Therefore, in Case 4, all of Conditions 1g-1 to 1g-3 are satisfied. Accordingly, the ECU 10 determines that the acceleration necessity level is "high". Therefore, similar to Case 3, the driver can obtain a deceleration feeling corresponding to his / her AP operation. As a result, smooth accelerator override can be realized.

[0052] On the other hand, when none of Conditions 1d to 1g are satisfied when the release condition is satisfied, the ECU 10 determines that the acceleration necessity level is "medium".

[0053] 2. When the control target is a red traffic signal or a stop sign When the following Condition 2d is satisfied, the ECU 10 determines that the acceleration necessity level is "low". (Condition 2d) The TTC for the control target is equal to or less than the first threshold value TTCth1.

[0054] Case 2 in FIG. 4 shows a scene where deceleration assistance control is being executed with the red traffic signal Sa or the stop sign Sb as the control target. The symbol L represents the travel lane. At this point, TTC≦TTCth1 is satisfied. In this scene, when the driver accidentally depresses the accelerator pedal when intending to decelerate the host vehicle V more by depressing the brake pedal, since the release condition is satisfied, the ECU 10 calculates the acceleration necessity level. In Case 2, since Condition 2d is satisfied, the ECU 10 determines that the acceleration necessity level is "low". In this case, similar to Case 1, even when the AP operation amount becomes larger contrary to the driver's intention due to accidental pedal misoperation, the possibility that the driver feels discomfort can be reduced.

[0055] Further, when the following condition 2e is satisfied, the ECU 10 determines that the acceleration necessity is "medium", and when the following condition 2f is satisfied, the ECU 10 determines that the acceleration necessity is "high". (Condition 2e) The TTC for the controlled object exceeds the first threshold value TTCth1 and is equal to or less than the second threshold value TTCth2. (Condition 2f) The TTC for the controlled object exceeds the second threshold value TTCth2.

[0056] 3. When the control situation is "before right or left turn at an intersection" The ECU 10 calculates the time required for the host vehicle to reach the intersection as TTC. When TTC ≦ TTCth1, the ECU 10 determines that the acceleration necessity is "low". When TTCth1 < TTC ≦ TTCth2, the ECU 10 determines that the acceleration necessity is "medium". When TTCth2 < TTC, the ECU 10 determines that the acceleration necessity is "high".

[0057] 4. When the control situation is "driving on a curved road" It is considered that the greater the lateral acceleration Gl when the host vehicle is driving on a curved road, the lower the necessity for acceleration. Therefore, when the lateral acceleration Gl is equal to or less than a predetermined first lateral acceleration threshold value Glth1, the ECU 10 determines that the acceleration necessity is "high". When the lateral acceleration Gl exceeds the first lateral acceleration threshold value Glth1 and is equal to or less than a predetermined second lateral acceleration threshold value Glth2 (> Glth1), the ECU 10 determines that the acceleration necessity is "medium". Further, when the lateral acceleration Gl exceeds the second lateral acceleration threshold value Glth2, the ECU 10 determines that the acceleration necessity is "low". Note that both the first and second lateral acceleration threshold values Glth1 and Glth2 are greater than Glth.

[0058] Next, a specific operation of the ECU 10 will be described. The CPU of the ECU 10 executes the routine shown in the flowchart of Fig. 6 while the ignition switch is on. At a predetermined timing, the CPU proceeds from step 600 to step 605, and determines whether deceleration support control is being executed due to the establishment of any one of start conditions 1 to 4. If deceleration support control is not being executed (S605: No), the CPU proceeds to step 695 and temporarily ends this routine. On the other hand, if deceleration support control is being executed (S605: Yes), the CPU proceeds to step 610.

[0059] In step 610, it is determined whether or not the driver has performed an AP operation based on vehicle state information (information related to the AP operation amount detected by the AP operation amount sensor 31). If the AP operation has not been performed (S610: No), the CPU proceeds to step 615, where it determines whether the vehicle speed v matches the target vehicle speed vtgt. If v=vtgt (S615: Yes), the CPU proceeds to step 620, where it ends the deceleration support control. On the other hand, if v>vtgt (S615: No), the CPU proceeds to step 625, where it continues the deceleration support control. After completing the processing of step 620 or 625, the CPU proceeds to step 695, where it temporarily ends this routine.

[0060] On the other hand, if the AP operation has been performed (S610: Yes), the CPU proceeds to step 630 to determine whether the AP operation amount is greater than the first threshold APth1. If the AP operation amount is less than or equal to APth1 (S630: No), the CPU proceeds to step 635 to set the absolute value |s| of the braking force decrease gradient to s1. On the other hand, if the AP operation amount is greater than APth1 (S630: Yes), the CPU proceeds to step 640.

[0061] In step 640, the CPU calculates the acceleration necessity based on the surrounding information and the vehicle state information. Then, the CPU proceeds to step 645 to determine whether the acceleration necessity is "high". If the acceleration necessity is "high" (S645: Yes), the CPU proceeds to step 650 to determine whether the AP operation amount is greater than the second threshold value APth2. If the AP operation amount > APth2 (S650: Yes), the CPU proceeds to step 655 to set the absolute value |s| of the deceleration gradient of the braking force to s3. On the other hand, if the AP operation amount ≦ APth2 (S650: No), the CPU proceeds to step 665 to set the absolute value |s| of the deceleration gradient of the braking force to s2.

[0062] On the contrary, if the acceleration necessity is not "high" (step 645: No), the CPU proceeds to step 660 to determine whether the acceleration necessity is "medium". If the acceleration necessity is "medium" (S660: Yes), the CPU proceeds to step 665 described above. On the other hand, if the acceleration necessity is not "medium" (that is, the acceleration necessity is "low") (S660: No), the CPU proceeds to step 635 described above.

[0063] When the processing of step 635, 655 or 665 is completed, the CPU proceeds to step 670 to cancel the deceleration assistance control by reducing the braking force at the set deceleration gradient. Also, an accelerator override is executed based on the AP operation amount detected in step 610. Then, the CPU temporarily ends this routine at step 695.

[0064] As described above, the driving support device according to the embodiment has been described. However, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the object of the present invention.

[0065] For example, whether to execute "control for changing the absolute value |s| of the decreasing gradient based on the AP operation amount and the degree of acceleration necessity" may be configured to be selectable by the driver's operation (typically, a touch panel operation or a switch operation). This configuration is particularly useful when the driver tends not to desire the intervention of the above control (desires vehicle behavior according to the AP operation amount).

[0066] Also, in the above embodiment, when the degree of acceleration necessity is high and the AP operation amount > APth2 (S650: Yes), the absolute value |s| of the decreasing gradient is uniformly set to s3 (a gradient that steeply decreases the braking force), but the configuration is not limited to this. When a relatively large braking force is applied by the deceleration assistance control (in other words, the magnitude of the deceleration is relatively large), if the braking force suddenly decreases, the deceleration may vary greatly and the driver may feel discomfort. Therefore, when "S650: Yes", the driving support device may be configured to set the absolute value |s| of the decreasing gradient to a value smaller than s3 (for example, s2) when the braking force applied to the host vehicle at the current time (that is, the time when the AP operation is performed) is greater than a predetermined braking force threshold. According to this configuration, when the braking force is relatively large in the case of "S650: Yes", the braking force decreases relatively gently. For this reason, it is possible to suppress the occurrence of a situation where the deceleration varies greatly, and as a result, it is possible to reduce the possibility that the driver feels discomfort. Note that the present invention is also applicable to an autonomous vehicle.

Explanation of Reference Numerals

[0067] 10: Driving support ECU, 20: Front sensor, 30: Vehicle state sensor, 40: Driving device, 50: Braking device, 60: Steering device

Claims

1. A surrounding sensor that detects a three-dimensional object existing around the vehicle and a road surface marking in front of the vehicle, and can acquire information on the detected three-dimensional object and road surface marking as surrounding information, A vehicle state sensor that detects a plurality of types of vehicle states according to a driving operation by a driver of the vehicle, and can acquire information on the detected vehicle states as vehicle state information, wherein the vehicle state sensor includes an accelerator pedal operation amount according to an accelerator pedal operation by the driver as one of the detected vehicle states, When a predetermined start condition is satisfied, deceleration assistance control is executed to assist in decelerating the vehicle by automatically applying a braking force to the vehicle. When a release condition that is satisfied when the accelerator pedal operation is performed during the execution of the deceleration assistance control is satisfied, the deceleration assistance control is released by reducing the braking force so that the deceleration of the vehicle becomes zero. A control unit configured as described above, Comprising, When the release condition is satisfied, the control unit is configured to linearly decrease the braking force based on the surrounding information and the vehicle state information. A driving assistance device.

2. In the driving assistance device according to Claim 1, When the release condition is satisfied, the control unit, Calculates an acceleration necessity degree, which is an index indicating the level of necessity for acceleration of the vehicle, based on the surrounding information and the vehicle state information, When the acceleration necessity degree is low, the absolute value of the decrease gradient of the braking force is made smaller than a predetermined reference gradient regardless of the value of the accelerator pedal operation amount. When the acceleration necessity degree is high, when the accelerator pedal operation amount is large, the absolute value of the decrease gradient is made larger compared to when the accelerator pedal operation amount is small. It is configured as described above. A driving assistance device.

3. In the driving assistance device according to Claim 2, The vehicle state sensor includes a steering angle according to a steering operation by the driver and an operation state of a direction indicator according to a direction indication operation by the driver as the detected vehicle states, The control unit, When the predicted arrival time of the vehicle to a preceding vehicle or a traffic signal or road sign that requires the vehicle to stop is equal to or less than a predetermined first time threshold, the magnitude of the steering angle is equal to or less than a predetermined first steering angle threshold, and the direction indicator is not operated, it is configured to determine that the acceleration necessity degree is low. A driving assistance device.

4. In the driving support device according to claim 2, the vehicle state sensor includes, as the detected vehicle state, a steering angle corresponding to a steering operation by the driver and an operation state of a direction indicator corresponding to a direction indicator operation by the driver, the control unit is configured to determine that the acceleration necessity is high in any of the following cases: that is, a first case where a predicted arrival time of the vehicle to a preceding vehicle or a traffic signal or a road sign that requires the vehicle to stop exceeds a predetermined second time threshold; a second case where the preceding vehicle does not exist, the magnitude of the steering angle is equal to or less than a predetermined first steering angle threshold, and the direction indicator is not operated; or a third case where the preceding vehicle exists, the magnitude of the steering angle exceeds a predetermined second steering angle threshold that is greater than the first steering angle threshold, and the direction indicator is operated in a direction corresponding to the steering operation, a driving support device.

5. In the driving support device according to claim 3, the control unit is configured to determine that the acceleration necessity is high in any of the following cases: that is, a first case where a predicted arrival time of the vehicle to a preceding vehicle or a traffic signal or a road sign that requires the vehicle to stop exceeds a predetermined second time threshold that is greater than the first time threshold; a second case where the preceding vehicle does not exist, the magnitude of the steering angle is equal to or less than a predetermined first steering angle threshold, and the direction indicator is not operated; or a third case where the preceding vehicle exists, the magnitude of the steering angle exceeds a predetermined second steering angle threshold that is greater than the first steering angle threshold, and the direction indicator is operated in a direction corresponding to the steering operation, a driving support device.

Images