JP2023087425A - Driving assist system - Google Patents

Abstract

To execute override within a permissible range of a driver's feeling of wrongness during implementation of steering support control.SOLUTION: A driving assist system includes override execution means that determines whether a condition for execution of override has been established during implementation of steering support control, and executes override when the condition for execution has been established, relational expression storage means that stores in advance a relational expression which stipulates a relationship between an input value relating to a driver's steering manipulation and an expected output value of an own vehicle which a driver expects, and feeling-of-wrongness factor arithmetic means that computes a feeling-of-wrongness factor, which is an index representing a degree to which a driver perceives a feeling of wrongness with respect to a behavior of the own vehicle, as a value which gets larger as an actual output value of the own vehicle relative to the input value is dissociated from the expected output value relative to the input value. The override execution means integrates feeling-of-wrongness factors computed during implementation of steering support control. When the integrated value is equal to or larger than a predetermined permissible threshold, the override execution means determines that the condition for execution has been established.SELECTED DRAWING: Figure 5

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving assistance device capable of executing a steering override that gives priority to a driver's steering operation during execution of steering assistance control.

2. Description of the Related Art Conventionally, there has been known a driving assistance device that is mounted on a vehicle and capable of executing steering assistance control for assisting a driver's steering operation (see Patent Literature 1). The driving assistance device acquires surrounding information from a camera sensor and/or a radar sensor, and also acquires a vehicle state and a driving operation state from various sensors (vehicle speed sensor, steering torque sensor, etc.). When the conditions for executing steering support control are satisfied, the driving support device calculates a target output value (typically, yaw rate, lateral acceleration, etc.) based on the acquired surrounding information, vehicle state, and driving operation state. Then, the steering angle (the angle at which the steered wheels of the vehicle are steered) required to match the current output value with the target output value is calculated as the target steering angle. Then, the torque required to match the steering angle of the steered wheels with the target steering angle (hereinafter also referred to as "control torque") is calculated, and the torque is applied to the steering mechanism of the vehicle, thereby steering the vehicle. perform assistive control;

In general, the driving support device cancels the steering support control and executes an override that gives priority to the driver's steering operation when the driver intends to drive based on his/her own steering operation during the execution of the steering support control. configured as possible. For example, the driving assistance device of Patent Document 1 overrides when an input value (for example, steering torque, steering angle, or steering angular velocity) based on a driver's steering operation during execution of steering assistance control exceeds a predetermined override threshold. is configured to run

Japanese Patent No. 6819876

However, in a configuration such as the driving support device of Patent Document 1 that determines whether or not to execute the override based only on the input value based on the driver's steering operation, the driver may feel uncomfortable. That is, when the driver performs a steering operation, the driver expects (anticipates) that the vehicle behaves in accordance with the steering operation. For example, when the driver performs a steering operation to rotate the steering wheel clockwise, the driver expects the vehicle to turn to the right at a degree corresponding to the amount of rotation of the steering wheel. However, since the control torque calculated by the driving support device is applied to the vehicle while the steering support control is being executed, the behavior of the vehicle may deviate from the behavior corresponding to the steering operation by the driver. . Therefore, in the above-described configuration (configuration for determining whether override can be executed based only on the input value based on the driver's steering operation), the behavior of the vehicle during the period until the override is executed is different from the behavior expected by the driver. A large deviation or a long-term deviation may occur, which may cause the driver to feel uncomfortable (in other words, the sense of discomfort may exceed the permissible range). Therefore, if the driver intends to drive based on his/her own steering operation during the execution of the steering assist control, it is desirable that the override is executed within the permissible range of discomfort.

The present invention has been made to address the problems described above. That is, one of the objects of the present invention is to provide a driving assistance system capable of executing an override within an allowable range of driver discomfort during execution of steering assistance control.

A driving support device according to the present invention (hereinafter referred to as "the device of the present invention") is
Surrounding information acquisition means (11) for acquiring, as surrounding information, information about a three-dimensional object existing in front of the own vehicle and lane markings defining a lane extending ahead of the own vehicle;
steering assistance control execution means (10, 20, 21, 22) for executing steering assistance control for assisting the steering operation of the driver of the host vehicle based on at least the surrounding information;
It is determined whether or not an override execution condition for canceling the steering assist control during execution of the steering assist control and giving priority to the driver's steering operation is satisfied (step 430), and if the execution condition is satisfied. If yes (step 430: Yes), override execution means (10, 20) for executing the override;
A relational expression (mx-b1 ≤ y a relational expression storage means (10) pre-stored with ≦mx+b2;
The actual output value (YR) of the own vehicle with respect to the input value (ST) is the input value (ST). a discomfort factor calculation means (10) for calculating a value that increases as it deviates from the expected output value for
Prepare.
The override execution means (10, 20)
The discomfort factor calculated during the execution of the steering assist control is integrated, and if the integrated value of the discomfort factor is equal to or greater than a predetermined allowable threshold (step 525: Yes), it is determined that the execution condition is established. (step 530, step 430: Yes),
is configured as

In the device of the present invention, whether or not override can be executed is determined based not only on the input value related to the driver's steering operation, but also on the actual output value (actual output value) of the own vehicle corresponding to the input value. Specifically, a discomfort factor (an index indicating the degree of discomfort felt by the driver with respect to the behavior of the vehicle) is calculated based on the input value and the actual output value, and the discomfort factor calculated during the execution of the steering support control is calculated. An integrated value of factors is calculated. This discomfort factor integrated value increases as the driver's discomfort increases, and increases as the driver's discomfort continues over a long period of time. The execution condition of the override is established when the integrated value of the discomfort factor becomes equal to or greater than the allowable threshold. According to this configuration, by appropriately setting the permissible threshold, it is possible to perform the override within the permissible range of the discomfort of the driver.

In the above description, in order to facilitate understanding of the invention, the symbols used in the embodiments are attached to the constituent elements of the invention corresponding to the embodiments in parentheses. are not limited to the embodiments defined by

1 is a schematic configuration diagram of a driving assistance device according to an embodiment of the present invention; FIG. 4 is a graph that defines the relationship between the driver steering torque and the yaw rate, and is a graph for explaining a case where the driver feels relatively little discomfort. 4 is a graph that defines the relationship between the driver's steering torque and the yaw rate, and is a graph for explaining a case where the driver's sense of discomfort is relatively large. 4 is a flowchart showing a routine executed by a CPU of a driving assistance ECU 10 included in the driving assistance device; 4 is a flowchart showing a routine (override determination process) executed by a CPU; It is a graph stored in ROM of driving assistance ECU10, and is a graph for demonstrating a discomfort small area|region and a discomfort large area|region.

(embodiment)
Hereinafter, a driving support device according to the present embodiment (hereinafter also referred to as "this embodiment device") will be described with reference to the drawings. As shown in FIG. 1, this embodiment includes a driving support ECU 10 and sensors 11 to 13 connected thereto, a steering ECU 20 and elements 21 and 22 connected thereto, a brake ECU 30 and elements connected thereto. 31, 32 and . These ECUs 10, 20 and 30 are each provided with a microcomputer as a main part, and are connected to each other via a CAN (Controller Area Network) (not shown) so as to be able to transmit and receive data. Note that ECU is an abbreviation for Electronic Control Unit. The microcomputer includes a CPU, storage devices such as ROM and RAM, and an interface (I/F), and the CPU executes instructions (programs) stored in the ROM to realize various functions. It's becoming Hereinafter, the vehicle equipped with this driving support device is referred to as "own vehicle". Further, hereinafter, the driving support ECU 10, the steering ECU 20 and the brake ECU 30 are also simply referred to as "ECU 10", "ECU 20" and "ECU 30", respectively.

The ECU 10 is connected to an ambient sensor 11 , a vehicle state sensor 12 and a driving operation sensor 13 .

The surrounding sensor 11 has a function of acquiring at least information on the road in front of the vehicle and information on three-dimensional objects existing on the road. Three-dimensional objects include, for example, moving objects such as pedestrians, bicycles, and automobiles, and fixed objects such as utility poles, trees, and guardrails.
The ambient sensor 11 includes, for example, a camera sensor and a radar sensor.
The camera sensor is equipped with a stereo camera that captures the landscape in front of the vehicle, and based on the image data obtained by capturing the shape of the road, the presence or absence of three-dimensional objects, and the relative relationship between the vehicle and the three-dimensional objects, etc. do. Also, the camera sensor recognizes lane markings extending on the road, and calculates the shape of the road and the positional relationship between the road and the vehicle. Note that the camera sensor may be provided with a monocular camera instead of the stereo camera.
The radar sensor emits radio waves in the millimeter wave band around the vehicle (at least a range including a front area of the vehicle), and receives reflected waves from the three-dimensional object when the three-dimensional object exists. The radar sensor detects the presence or absence of a three-dimensional object and the relative relationship between the vehicle and the three-dimensional object (the distance from the vehicle to the three-dimensional object, the direction of the three-dimensional object with respect to the vehicle, and the relative speed of the three-dimensional object with respect to the own vehicle), etc. are calculated.
That is, the surrounding sensor 11 acquires information about a three-dimensional object existing in front of the own vehicle and lane markings extending in front of the own vehicle.

Information calculated (obtained) by the surrounding sensor 11 is referred to as surrounding information. The ambient sensor 11 transmits ambient information to the ECU 10 every time a predetermined time elapses. Note that the surrounding sensor 11 does not necessarily have to include a camera sensor and a radar sensor, and may be configured to include only a camera sensor, for example. Information of a navigation system can also be used for the information representing the shape of the road on which the vehicle travels and the positional relationship between the road and the vehicle.

The vehicle state sensor 12 includes a vehicle speed sensor that detects the running speed of the own vehicle, a wheel speed sensor that detects the wheel speed, a longitudinal G sensor that detects the longitudinal acceleration of the own vehicle (acceleration in the longitudinal direction), and a lateral acceleration of the own vehicle ( A lateral G sensor that detects lateral acceleration) and a yaw rate sensor that detects the yaw rate of the host vehicle.

The driving operation sensor 13 includes a steering angle sensor that detects the steering angle, a steering torque sensor that detects the steering torque, a brake operation amount sensor that detects the amount of operation of the brake pedal, a brake switch that detects whether or not the brake pedal is operated, and , setting switches for setting each driving support control. By operating the setting switch, the driver can select whether or not to perform each driving support control, and can set control conditions (for example, vehicle speed).
The steering direction (horizontal direction) is specified by the sign of the steering angle and the steering torque. Also, the steering angular velocity can be calculated by differentiating the steering angle. The sign of the steering speed also identifies the steering direction. In this specification, the steering angle sensor and the steering torque sensor respectively detect the steering angle and the steering torque input based on the driver's steering operation.

The ECU 10 has a function of executing steering assistance control including collision avoidance steering assistance control and lane keeping assistance control as driving assistance control (described later).

The ECU 20 is a control device for the electric power steering system and is connected to the motor driver 21 . The motor driver 21 is connected to the steering motor 22 . The steering motor 22 is incorporated in a steering mechanism (not shown), a rotor is rotated by electric power supplied from the motor driver 21, and the rotation of the rotor steers left and right steerable wheels.
Under normal conditions, the ECU 20 causes the steering motor 22 to generate an assist torque corresponding to the steering torque (that is, the value detected by the steering torque sensor) based on the driver's steering operation. When the driver performs a steering operation, the sum of the "steering torque based on the driver's steering operation" and the "assist torque" is applied to the steering mechanism. Therefore, the sum of these is hereinafter referred to as "driver steering torque ST". The driver steering torque ST corresponds to an example of "an input value related to the driver's steering operation".
On the other hand, when receiving a steering control command transmitted from the ECU 10, the ECU 20 drives and controls the steering motor 22 according to the steering control command to steer the steered wheels. Specifically, the steering control command is a command transmitted when the steering support control is executed, and includes a signal representing the target steering angle. When the steering control command is received, the ECU 20 causes the steering motor 22 to generate the torque required to match the steering angle of the steered wheels with the target steering angle. This torque is applied to the steering mechanism when executing the steering assist control. Therefore, the torque is hereinafter referred to as "control torque CT".

The ECU 30 is connected to the brake actuator 31 . The brake actuator 31 is provided in a hydraulic circuit between a master cylinder (not shown) that pressurizes hydraulic oil by the force applied to the brake pedal and friction brake mechanisms 32 that are provided on the left and right front and rear wheels. The friction brake mechanism 32 includes a brake disc 32a fixed to the wheel and a brake caliper 32b fixed to the vehicle body. When activated, the brake pad is pressed against the brake disc 32a to generate a frictional braking force.

The brake actuator 31 is a known actuator that adjusts the hydraulic pressure supplied to the wheel cylinder built in the brake caliper 32b, and supplies the hydraulic pressure to the wheel cylinder according to the control command from the ECU 30 to apply braking force to the left, right, front and rear wheels. generate.

Based on the surrounding information acquired from the surrounding sensor 11, the ECU 10 detects the shape of the driving lane (the lane in which the vehicle is currently driving), the position and orientation of the vehicle within the driving lane, and the three-dimensional objects relative to the vehicle. Calculate the relative position of Note that a lane may be defined as the area between two adjacent lane markings. The ECU 10 executes the control when conditions for executing the steering assist control (described later) are satisfied. Further, the ECU 10 terminates or cancels the control when conditions for termination or cancellation (interruption) of the control (both of which will be described later) are satisfied during the execution of the steering assist control. The steering assist control will be described below by taking collision avoidance steering assist control and lane keeping assist control as examples. Note that the steering support control may also include other controls (for example, lane change support control).

(Collision avoidance steering support control)
Collision avoidance steering support control is control that applies a control torque to the steering mechanism so as to avoid collision with an obstacle when there is a high possibility of collision with the obstacle. Collision avoidance steering assist control includes emergency steering assist control (ESA) and automatic emergency steering control (AES). The emergency steering support control is triggered by the steering operation performed by the driver when there is a high possibility of colliding with an obstacle. This control assists the driver's steering operation so that the vehicle does not deviate from the lane markings. Automatic emergency steering control is a control that automatically operates without the driver's steering operation when there is a high possibility of collision with an obstacle.

Specifically, the ECU 10 calculates the turning radius of the vehicle based on the yaw rate detected by the yaw rate sensor and the vehicle speed detected by the vehicle speed sensor, and calculates the trajectory of the vehicle based on the turning radius. (Predict. Further, the ECU 10 determines whether the three-dimensional object is a moving object or a stationary object based on the change in the position of the three-dimensional object obtained from the surrounding information. Based on this, the trajectory of the three-dimensional object is calculated (predicted). Then, based on the trajectory of the own vehicle and the trajectory of the three-dimensional object, the own vehicle maintains the current running state and runs, and the three-dimensional object maintains the current moving state (if it is a stationary object, the stationary state). It is determined whether or not the own vehicle will collide with a three-dimensional object when moving by When the ECU 10 determines that the vehicle will collide with a three-dimensional object, the ECU 10 recognizes the three-dimensional object as an obstacle, and calculates a collision prediction time (TTC: Time To Collision), which is estimated to be required until the vehicle collides with the obstacle. Calculate as TTC can be calculated by dividing the distance from the own vehicle to the collision prediction point by the vehicle speed. When the TTC is equal to or less than a predetermined TTC threshold, the ECU 10 determines that there is a high possibility that the host vehicle will collide with an obstacle.

In this case, the ECU 10 calculates a target avoidance trajectory that the vehicle can take to avoid a collision with an obstacle. The target avoidance trajectory is a trajectory that minimizes the lateral acceleration of the vehicle among a plurality of trajectories that allow the vehicle to turn to avoid collision without interfering with obstacles. Since the method of calculating the target avoidance trajectory is well known, a detailed description thereof will be omitted (see, for example, Japanese Patent Application Laid-Open No. 2020-26207). When the collision avoidance steering support control is the emergency steering support control, the target avoidance trajectory is set within the driving lane.

When the collision avoidance steering support control is the automatic emergency steering control, the ECU 10 determines that the conditions for executing the control are satisfied when both of the following conditions 1A and 2A are satisfied.
(Condition 1A) There is a high possibility that the vehicle will collide with an obstacle.
(Condition 2A) A target avoidance trajectory is calculated.
On the other hand, when the collision avoidance steering support control is the emergency steering support control, the ECU 10 determines that the conditions for executing the control are satisfied when the following condition 3A is satisfied in addition to the conditions 1A and 2A.
(Condition 3A) A steering operation is being performed by the driver.
Note that condition 3A can be determined to be satisfied when the steering angle, steering torque and/or steering angular velocity are each equal to or greater than a predetermined threshold value.
However, the execution condition of the collision avoidance steering assist control is not limited to this.

When at least one of the conditions 1A and 2A is no longer satisfied, the ECU 10 determines that the condition for terminating the collision avoidance steering assist control is satisfied, and terminates the execution of the control. In addition, when at least one of the following conditions 4A to 6A is satisfied, the ECU 10 determines that the cancellation (suspension) condition of the collision avoidance steering support control is satisfied and cancels (suspends) the execution of the control. .
(Condition 4A) The driver is performing a brake operation.
(Condition 5A) Vehicle Stability Control (VSC) is being executed because the road surface has low friction.
(Condition 6A) Automatic brake control is being executed.
Here, the vehicle stabilization control is well-known control for suppressing side slip of the vehicle. Automatic brake control is well-known control that automatically applies braking force (braking force) to the vehicle when there is a high possibility that the vehicle will collide with an obstacle.
However, the end condition and cancellation condition of the collision avoidance steering support control are not limited to this.

(Lane keeping support control)
Lane Tracing Assist (LTA) is a control that applies a control torque to a steering mechanism so that the position of the own vehicle is maintained near a target travel line in the travel lane. The ECU 10 determines that the conditions for executing the lane keeping support control are satisfied when all of the following conditions 1B to 3B are satisfied.
(Condition 1B) Execution of lane keeping support control is selected by an LTA setting switch (not shown).
(Condition 2B) Adaptive Cruise Control (ACC) is being executed.
(Condition 3B) The camera sensor recognizes the lane marking.
However, the execution condition of the lane keeping support control is not limited to this.

When at least one of the conditions 1B to 3B is no longer satisfied, the ECU 10 determines that the condition for terminating the lane keeping support control is satisfied and terminates the execution of the control.

Next, overrides will be explained. Conventionally, whether or not override can be executed is determined based only on the input value based on the driver's steering operation, which may cause the driver to feel uncomfortable. A detailed description will be given with reference to FIGS. 2 and 3. FIG. 2 and 3 are both graphs defining the relationship between the driver steering torque ST [Nm] (x-axis) and the yaw rate YR [deg/sec] (y-axis). As described above, the driver steering torque ST is the sum of the "steering torque based on the driver's steering operation" and the "assist torque." The yaw rate YR is one kind of physical quantity that determines the behavior of the host vehicle.

In general, when a driver performs a steering operation, the driver expects (anticipates) that the behavior of the host vehicle corresponding to the steering operation will be realized. Specifically, when the driver steering torque ST increases (or decreases) due to the driver's own steering operation, the yaw rate YR increases (or decreases) substantially linearly as the driver steering torque ST increases (or decreases). ). A dashed line BL in the graphs of FIGS. 2 and 3 indicates an ideal relationship between the driver's steering torque ST and the yaw rate YR. When the value of the yaw rate YR for any given driver's steering torque ST is in the vicinity of the dashed line BL, the driver feels that the vehicle behaves in accordance with his/her own steering operation, and feels uncomfortable. Very little. On the other hand, when the value of the yaw rate YR for any given driver's steering torque ST is positioned away from the dashed line BL, the behavior of the own vehicle deviates (deviates) from the behavior corresponding to its own steering operation. I feel like I'm there, and I feel a sense of discomfort. In this embodiment, the dashed line BL is a straight line. However, if the dashed line BL has a shape that reflects the relationship between the driver's steering torque ST and the yaw rate YR expected by the driver, it is not limited to being a straight line. do not have.

Solid lines SL1 and SL2 in the graphs of FIGS. 2 and 3 show changes in the yaw rate YR when the driver performs a steering operation over a predetermined period during the execution of the steering assist control. Point S corresponds to the start of the period and point G corresponds to the end of the period. In this embodiment, when the driver performs a steering operation during execution of the steering assist control, a value obtained by adding the driver's steering torque ST to the control torque CT is applied to the steering mechanism. That is, the yaw rate YR on the solid lines SL1 and SL2 is the yaw rate of the host vehicle when the sum of the control torque CT and the driver's steering torque ST is applied to the steering mechanism. This yaw rate (that is, the yaw rate when the total value of the control torque CT and the driver's steering torque ST is applied to the steering mechanism) is the "actual output value of the own vehicle with respect to the input value related to the driver's steering operation". It corresponds to an example.

As shown in FIG. 2, the solid line SL1 moves in a region away from the broken line BL in a relatively short period of time from the point S to the point G in which it moves within the range D1. , the region changes in the vicinity of the dashed line BL. For this reason, it is considered that the driver feels a little discomfort during the period in which the range D1 is transited, but hardly feels discomfort during the rest of the period.
On the other hand, as shown in FIG. 3, the solid line SL2 transitions in a region spaced apart from the broken line BL over a relatively long period of the period from point S to point G (period of transition within range D2). are doing. For this reason, it is considered that the driver will feel discomfort for a relatively long period of time.

Therefore, in the conventional configuration for determining whether or not override can be executed based only on the input value based on the driver's steering operation, the behavior of the own vehicle during the period until the override is executed is different from the behavior expected by the driver. A large deviation or a long-term deviation may occur, which may cause the driver to feel uncomfortable (in other words, the sense of discomfort may exceed the permissible range).

Therefore, in the present embodiment, the ECU 10 performs override based on not only the input value (input value including assist torque) related to the driver's steering operation, but also the physical quantity (output value) that determines the behavior of the host vehicle. It is configured to determine whether or not it can be executed. Hereinafter, specific operations of the ECU 10 will be described with reference to FIGS. 4 and 5. FIG.

The CPU of the ECU 10 is configured to repeatedly execute the routines shown in the flowcharts of FIGS. 4 and 5 each time a predetermined period of time elapses while the ignition switch is in the ON state.

At a predetermined timing, the CPU starts processing from step 400 in FIG. is established, it is determined whether or not the steering support control is being executed. If the steering assist control is not being executed (step 410: No), the CPU proceeds to step 495 and once ends this routine. On the other hand, if steering support control is being executed (step 410: Yes), the CPU proceeds to step 420 to perform override determination processing.

After proceeding to step 420, the CPU starts the processing from step 500 in FIG. 5, proceeds to step 505, and determines whether or not the current time is included in the override effective period. That is, since the steering system dynamically fluctuates in a predetermined specific period after the start of the steering assist control, the detected value of the steering torque sensor tends to increase due to the influence of inertia and/or road friction, and the driver is forced to override. It's hard to tell if you want it or not. Therefore, it is configured not to determine whether or not the override can be executed during the specific period. The override effective period is a period obtained by excluding the specific period from the period during which the steering assist control is executed (that is, the period during which it can be appropriately determined whether or not the driver desires the override).

The specific period can be set for each type of steering assistance control. For example, after the start of the collision avoidance steering support control, the degree of fluctuation of the steering system is greater than that after the start of the lane keeping support control. Therefore, the specific period of the collision avoidance steering assistance control can be set longer than the specific period of the lane keeping assistance control (the specific period is set to zero because the influence of inertia is relatively small in the lane keeping assistance control). may be used.). In addition, when in-lane return support control (control to apply control torque to the steering mechanism so that the vehicle does not deviate from the lane) is performed after the end of the collision avoidance steering support control, the in-lane return support control is started. It may be configured not to determine whether or not the override can be executed even in another predetermined specific period including the time point at which the override is performed (for details, see Japanese Patent Application Laid-Open No. 2020-26207).

If the current time is not included in the override effective period (that is, included in the specific period) (step 505: No), the CPU proceeds to step 510 and sets the value of the override flag to 0. The override flag is a flag used to determine whether or not the override can be executed. If the value is 0, it indicates that the override is not executed (not permitted), and if the value is 1, the override is executed. indicates (permit). Thereafter, the CPU advances the process to step 595 to end the override determination process, and advances the process to step 430 in FIG. 4 (described later).

On the other hand, if the current time is included in the override effective period (step 505: Yes), the CPU proceeds to step 515 and refers to the graph in FIG. It is determined whether or not the YR value (actual output value) is located within the large discomfort region R2. Here, before describing the process of step 515, the graph of FIG. 6 will be described. This graph defines the relationship between the driver steering torque ST [Nm] (x-axis) and the yaw rate YR [deg/sec] (y-axis). The area in the graph is divided into a “discomfort small region R1” and a “discomfort large region R2”. The discomfort small area R1 is an area near the dashed line BL (that is, an area where the driver is less likely to feel discomfort) (see the gray area). If the formula of the dashed line BL is defined as y=mx (m: inclination), the discomfort small region R1 is a region that satisfies mx−b1≦y≦mx+b2. When the value of the yaw rate YR with respect to the driver's steering torque ST at the present time is located in the discomfort small region R1, the driver feels that the vehicle behaves in accordance with his/her own steering operation. Therefore, it can be said that the value of the yaw rate YR within the discomfort small region R1 is the output value (expected output value) of the own vehicle that the driver expects based on his/her own steering operation. In other words, the above inequality (mx-b1≤y≤mx+b2) that defines the discomfort small region R1 is defined as "the input value related to the steering operation of the driver and the expectation of the vehicle that the driver expects based on the steering operation. It corresponds to an example of "relational expression defining the relationship between the output value and Note that the constants b1 and b2 can be set in advance based on experiments or simulations. Although b1=b2 in the present embodiment, b1≠b2 may be satisfied. Further, hereinafter, the value of the yaw rate YR with respect to the current driver steering torque ST is also referred to as "coordinates (ST, YR)".

On the other hand, the discomfort large region R2 is a region away from the dashed line BL (that is, a region where the driver tends to feel discomfort) and satisfies y<mx−b1 or mx+b2<y. For example, if the coordinates (ST, YR) are located at positions P1, P2, or P3, respectively, these are all located within the discomfort large region R2, and the driver feels discomfort. Specifically, when the coordinates (ST, YR) are located at the position P1, the driver feels a sense of incongruity due to excessive turning of the own vehicle in response to the driver's steering operation, and the coordinates (ST, YR) YR) is located at the position P2, the steering operation by the driver is small due to the small degree of turning of the vehicle, which makes the driver feel uncomfortable. A sense of incongruity is felt when the own vehicle turns in the direction opposite to the direction in which it should turn by the steering operation of the person.

The ECU 10 stores the graph of FIG. 6 in its ROM. The CPU refers to the graph stored in the ROM and determines whether or not the current yaw rate YR value (coordinates (ST, YR)) relative to the driver's steering torque ST is located within the large discomfort area R2. do. It should be noted that the ECU 10 may be configured to store the above-described inequality defining the discomfort small region R1 in the ROM instead of the graph of FIG.

If the current coordinates (ST, YR) are located within the large discomfort area R2 (step 515: Yes), the CPU proceeds to step 520 to calculate the integrated value of the discomfort factor. The discomfort factor is an index that indicates the degree of discomfort felt by the driver with respect to the behavior (output, response) of the own vehicle. The greater the discomfort factor, the greater the degree of discomfort experienced by the driver. In this embodiment, the discomfort factor is defined as |ΔYR·ST| (“·” represents a multiplication sign). Here, ΔYR represents the distance in the y-axis direction between the coordinates (ST, YR) and the discomfort small region R1 (in other words, the deviation amount of the yaw rate YR from the region R1). For example, as shown in FIG. 6, when the current coordinates (ST, YR) are located at the position Pe, ΔYR is equal to the distance in the y-axis direction from the position Pe to the boundary line of the discomfort small region R1. On the other hand, ST is equal to the value of the x-coordinate. That is, the discomfort factor increases as the value of the coordinates (ST, YR) deviates from the small discomfort area R1.

Specifically, the CPU calculates the discomfort factor (=|ΔYR·ST|) based on the current coordinates (ST, YR) in step 520, and calculates the discomfort factor (initial value: zero) stored in the RAM. ) by that value. As a result, the integrated value of the discomfort factor (excluding the value reset at step 550 described later) calculated during the period from the start of the currently executed steering support control to the present time is calculated. The CPU stores the discomfort factor integrated value thus calculated in the RAM. In addition, the CPU resets (initializes) the value of the timer T if the value of the timer T is not the initial value (zero) (described later).

Note that the discomfort factor is not limited to this, and may be defined as |ΔST|, for example. Here, ΔST represents the distance in the x-axis direction between the coordinates (ST, YR) and the discomfort small region R1 (in other words, the deviation amount of the driver steering torque ST from the region R1).
In addition to the yaw rate YR, the physical quantity that determines the behavior of the own vehicle includes the lateral acceleration LA and the steering angle SA. Therefore, in place of the graph of FIG. 6, a graph defining the relationship between the driver steering torque ST and the lateral acceleration LA is used to divide a small sense of discomfort region R1 and a large sense of discomfort region R2, and the sense of discomfort factor is defined as |ΔLA·ST| may be specified. Here, ΔLA represents the distance in the y-axis direction between the coordinates (ST, LA) and the discomfort small region R1 (in other words, the deviation amount of the lateral acceleration LA from the region R1).
Alternatively, in place of the graph of FIG. 6, a graph defining the relationship between the driver steering torque ST and the steering angle SA is used to define a discomfort small region R1 and a discomfort large region R2, and define the discomfort factor as |ΔSA·ST|. You may Here, ΔSA represents the distance in the y-axis direction between the coordinates (ST, SA) and the discomfort small region R1 (in other words, the deviation amount of the steering angle SA from the region R1).
Furthermore, a discomfort factor incorporating two or more of the above physical quantities (yaw rate YR, lateral acceleration LA, and steering angle SA) may be defined by making them dimensionless.

Subsequently, the CPU advances the process to step 525 and determines whether or not the discomfort factor integrated value calculated in step 520 is equal to or greater than a predetermined allowable threshold. The permissible threshold is the upper limit of the permissible range of discomfort for the driver, and can be set in advance through experiments or simulations. If the integrated discomfort factor value is less than the allowable threshold (step 525 : No), the CPU proceeds to step 510 . At step 510, the CPU determines that the discomfort of the driver is still within the allowable range, and sets the value of the override flag to zero. Thereafter, the CPU advances the process to step 595 to end the override determination process, and advances the process to step 430 in FIG.

At step 430, the CPU determines whether the value of the override flag is one. If the value of the override flag is 0 (step 430: No), the CPU proceeds to step 440 and determines whether or not the aforementioned conditions for ending or canceling the steering assist control are satisfied. If the termination condition or cancellation condition is satisfied (step 440: Yes), the CPU proceeds to step 450 to terminate or cancel the steering assist control. Subsequently, the CPU advances the process to step 460 to reset the discomfort factor integrated value, and resets the value of the timer T if the value of the timer T is not the initial value. Then, the process proceeds to step 495 and the present routine is terminated.

On the other hand, if the termination condition or the cancellation condition is not satisfied (step 440: No), the CPU proceeds to step 495 and temporarily terminates this routine. That is, the steering assist control continues to be executed without executing the override while maintaining the discomfort factor integrated value (and the value of the timer T if the value of the timer T is not the initial value).

Execution of the steering support control is continued because the above process (the value of the override flag is 0 because the integrated value of the discomfort factor is less than the allowable threshold value and the condition for ending or canceling the steering support control is not satisfied). process) is repeated, and if the integrated discomfort factor value becomes equal to or greater than the allowable threshold value (step 525 : Yes), the CPU proceeds to step 530 . At step 530, the CPU determines that the driver's sense of discomfort has exceeded the permissible range (that is, the override execution condition is satisfied), and sets the value of the override flag to one. Thereafter, the CPU advances the process to step 595 to end the override determination process, and advances the process to step 430 in FIG.

If the value of the override flag is 1 (step 430: Yes), the CPU proceeds to step 450 and executes the override. That is, the steering assist control is canceled and the driver's steering operation is prioritized. Subsequently, the CPU advances the process to step 460 and resets the integrated discomfort factor value and the timer T value (if not the initial value). Then, the process proceeds to step 495 and the present routine is terminated.

On the other hand, when the current coordinates (ST, YR) move to the discomfort small area R1 in the course of repeating the above process (step 515: No), the CPU proceeds to step 535 and stores the coordinates in the RAM. It is determined whether or not the integrated discomfort factor value is positive. Here, "the sense of discomfort factor integrated value is positive" means that there is a period during which the coordinates (ST, YR) are located in the large sense of discomfort area R2 during the current execution of the steering support control. On the other hand, "the sense of discomfort factor integrated value is not positive" means that the sense of discomfort factor integrated value is zero. It means that it was located in the region R1 (that is, there was no period during which it was located in the region R2). Strictly speaking, even if the coordinates (ST, YR) are located in the large discomfort area R2, the discomfort factor is zero when the x-coordinate value (=ST) is zero. Such a situation is considered to occur temporarily in the course of the driver's steering operation. Since a certain situation is hard to imagine, such a situation shall not be considered in this embodiment.

If the discomfort factor integrated value is positive (step 535: Yes), the CPU advances the process to step 540, starts timer T (initial value: zero), and reads, "Coordinates (ST, YR) are discomfort small region R1. and the period during which the discomfort factor integrated value is positive" is started to count up. Subsequently, the CPU advances the process to step 545 and determines whether or not the value of the timer T has reached a predetermined time threshold value Tth (T≧Tth is established). The time threshold Tth is the upper limit of the effective time during which the discomfort factor integrated value can be used to determine whether or not the override can be executed. That is, when the value of the timer T reaches the time threshold value Tth, the discomfort factor integrated value becomes invalid and is reset (described later).
When the value of the timer T has not yet reached the time threshold Tth (step 545: No), the CPU advances the process to step 510 while retaining the integrated value of the discomfort factor and the value of the timer T, and resets the value of the override flag. Set to 0. Subsequent processing is as described above.

On the other hand, if the coordinates (ST, YR) are always located in the discomfort small region R1 during the current execution of the steering assist control (step 515: No), the CPU proceeds to step 535. In this case, the integrated discomfort factor value remains zero (initial value) (step 535: No), so the CPU proceeds to step 510 and sets the value of the override flag to zero. Subsequent processing is as described above.

If the coordinates (ST, YR) move again to the large discomfort area R2 before the value of the timer T reaches the time threshold Tth (step 515: Yes), the CPU proceeds to step 520, and The currently calculated discomfort factor is added to the currently calculated discomfort factor integrated value to update the discomfort factor integrated value. In addition, when the coordinates (ST, YR) move from the large discomfort area R2 to the small discomfort area R1 and then return to the large discomfort area R2, the CPU resets the value of the timer T. Subsequent processing is as described above.

On the other hand, when the value of the timer T reaches the time threshold value Tth (step 545 : Yes), the CPU proceeds to step 550 . At step 550, the CPU determines that the integrated value of the discomfort factor has become invalid, and resets the integrated value and the timer T value. Subsequently, the CPU advances the process to step 510 and sets the value of the override flag to zero. Subsequent processing is as described above.

As described above, in this embodiment, the override is performed based on not only the driver steering torque ST (that is, the input value related to the driver's steering operation) but also the yaw rate YR (the actual output value for the input value). Execution propriety is determined. Specifically, the discomfort factor is calculated based on the value of the yaw rate YR (that is, the coordinates (ST, YR)) with respect to the driver's steering torque ST at the present time. An integrated value is calculated. This discomfort factor integrated value increases as the driver's discomfort increases, and increases as the driver's discomfort continues over a long period of time. Override is executed when the integrated discomfort factor value is greater than or equal to the allowable threshold. According to this configuration, by appropriately setting the allowable threshold value, it is possible to perform the override within the allowable range of discomfort for the driver.

Although the driving assistance device according to the embodiment has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the object of the present invention.

For example, the shape of the discomfort small region R1 is not limited to the shape shown in the graph of FIG. For example, the width in the y-axis direction between the boundary line B1 on the +y-axis direction side of the discomfort small region R1 and the dashed line BL, and the width in the y-axis direction between the boundary line B2 on the −y-axis direction side and the dashed line BL are both may be curved such that it becomes narrower as the magnitude |ST| of the driver's steering torque ST approaches zero and becomes wider as |ST| increases. Alternatively, the formula of the dashed line BL may be a curved formula such that in the first quadrant, as the driver steering torque ST increases, the differential coefficient becomes smaller and converges to the predetermined yaw rate YR. In this case, the equation of the dashed line BL in the third quadrant is point-symmetrical to the equation of the dashed line BL in the first quadrant with respect to the origin.

Further, in the above embodiment, when the coordinates (ST, YR) move from the discomfort large region R2 to the discomfort small region R1, the period during which the coordinates (ST, YR) remain in the discomfort small region R1 reaches the time threshold Tth. However, the method of resetting the integrated value is not limited to this. For example, when the coordinates (ST, YR) move from the large discomfort area R2 to the small discomfort area R1, the ECU 10 may calculate the integrated value of the no discomfort factor. The non-discomfort factor is an index that indicates the degree to which the driver does not feel discomfort with respect to the behavior (output, response) of the host vehicle. The greater the no discomfort factor, the less discomfort the driver feels. The comfortable factor may be defined as |ΔYR| or |ΔST|, for example. Note that ΔYR in this case is the shorter value of the distances in the y-axis direction between the coordinates (ST, YR) in the discomfort small region R1 and the boundary line of the region R1, and ΔST is the discomfort small region R1. It is the shorter value of the distance in the x-axis direction between the coordinates (ST, YR) inside and the boundary line of the region R1. The ECU 10 may be configured to reset the integrated value of the factor of discomfort when the integrated value of the factor of no discomfort becomes equal to or greater than a predetermined threshold.

Furthermore, in the above embodiment, the discomfort factor is not calculated when the coordinates (ST, YR) are located within the discomfort small region R1, but the configuration is not limited to this. For example, if the coordinates (ST, YR) are located within the discomfort small region R1, it may be calculated that the discomfort factor is zero.

Furthermore, the configuration of the present invention can also be applied to steer-by-wire vehicles.

10: driving support ECU, 11: ambient sensor, 12: vehicle state sensor, 13: driving operation sensor, 20: steering ECU, 21: motor driver, 22: steering motor, 30: brake ECU, 31: brake actuator, 32: Friction brake mechanism

Claims (1)

Surrounding information acquisition means for acquiring, as surrounding information, information about three-dimensional objects existing in front of the own vehicle and lane markings defining lanes extending ahead of the own vehicle;
steering support control execution means for executing steering support control for supporting a steering operation of the driver of the own vehicle based on at least the surrounding information;
During execution of the steering assist control, it is determined whether or not an override execution condition for canceling the steering assist control and giving priority to the driver's steering operation is satisfied, and if the execution condition is satisfied, an override execution means for executing the override;
A relational expression storage that stores in advance a relational expression defining a relation between an input value related to the steering operation of the driver and an expected output value of the own vehicle that the driver expects based on the steering operation. means and
A discomfort factor, which is an index indicating the degree of discomfort felt by the driver with respect to the behavior of the own vehicle, is defined as the difference between the actual output value of the own vehicle for the input value and the expected output value for the input value. a discomfort factor calculation means for calculating a value that increases as the number increases;
with
The override execution means is
integrating the discomfort factors calculated during the execution of the steering assist control, and determining that the execution condition is satisfied when the integrated value of the discomfort factors is equal to or greater than a predetermined allowable threshold;
configured as
Driving assistance device.

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