Driving Support Devices

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

[Technical field]

[0001] The present invention relates to a driving assistance device capable of executing a steering override that prioritizes a steering operation by a driver while a steering assistance control is being executed. [Background technology]

[0002] Conventionally, there is known a driving assistance device that is mounted on a vehicle and can execute steering assistance control to assist the driver in steering (see Patent Document 1). The driving assistance device acquires surrounding information from a camera sensor and / or a radar sensor, and acquires the vehicle state and driving operation state from various sensors (vehicle speed sensor, steering torque sensor, etc.). When the execution condition of the steering assistance control is established, the driving assistance device calculates a target output value (typically, yaw rate and lateral acceleration, etc.) based on the acquired surrounding information, vehicle state, and driving operation state, and calculates a steering angle (angle at which the steered wheels of the vehicle are steered) required to make the current output value coincide with the target output value as a target steering angle. Then, the driving assistance device calculates a torque (hereinafter also referred to as "control torque") required to make the steering angle of the steered wheels coincide with the target steering angle, and executes the steering assistance control by applying the torque to a steering mechanism of the vehicle.

[0003] In general, a driving assistance device is configured to be able to execute an override that cancels the steering assistance control and prioritizes the steering operation of the driver when the driver intends to drive based on his / her own steering operation while the steering assistance control is being executed. For example, the driving assistance device of Patent Document 1 is configured to execute an override when an input value based on the steering operation of the driver (e.g., steering torque, steering angle, or steering angular velocity) exceeds a predetermined override threshold value while the steering assistance control is being executed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6819876 Summary of the Invention

[0005] However, in a configuration in which the execution of an override is determined based only on an input value based on the steering operation of the driver, as in the driving assistance device of Patent Document 1, the driver may feel a sense of incongruity. That is, when the driver performs a steering operation, the driver expects (anticipates) that the vehicle's behavior according to the steering operation will be realized. For example, when the driver performs a steering operation to rotate the steering wheel clockwise, the driver expects that the vehicle will turn to the right with a turning degree according to the amount of rotation of the steering wheel. However, during the execution of the steering assistance control, the control torque calculated by the driving assistance device is applied to the vehicle, so that the vehicle's behavior may deviate (deviation) from the behavior according to the steering operation of the driver. Therefore, in the above-mentioned configuration (a configuration in which the execution of an override is determined based only on an input value based on the steering operation of the driver), a situation may occur in which the vehicle's behavior deviates significantly or for a long period of time from the behavior expected by the driver during the period until the override is executed, and the driver may feel a sense of incongruity (in other words, the sense of incongruity may exceed the acceptable range). For this reason, if the driver intends to drive based on his / her own steering operation while the steering assist control is being executed, it is desirable that an override be executed within an acceptable range of discomfort.

[0006] The present invention has been made to address the above-mentioned problems. That is, one of the objects of the present invention is to provide a driving assistance device that can execute an override within an acceptable range of discomfort felt by the driver while steering assistance control is being executed.

[0007] The driving assistance device according to the present invention (hereinafter referred to as the "device of the present invention") comprises: a surrounding information acquisition means (11) for acquiring information on a three-dimensional object present in front of the vehicle and a lane marking extending in front of the vehicle as surrounding information; a steering assist control execution means (10, 20, 21, 22) for executing a steering assist control for assisting a steering operation of a driver of the host vehicle based on at least the surrounding information; an override execution means (10, 20) that determines whether an override execution condition for canceling the steering assist control during execution of the steering assist control and prioritizing the steering operation of the driver is satisfied (step 430), and executes the override if the execution condition is satisfied (step 430: Yes); a relational equation storage means (10) that prestores a relational equation (mx-b1≦y≦mx+b2) that defines a relationship between an input value (ST) related to the steering operation of the driver and an expected output value of the vehicle that the driver expects based on the steering operation; a discomfort factor calculation means (10) for calculating a discomfort factor, which is an index showing a degree of discomfort felt by the driver with respect to the behavior of the vehicle, as a value that increases as an actual output value (YR) of the vehicle with respect to the input value (ST) deviates from the expected output value with respect to the input value (ST); Equipped with. The override execution means (10, 20) The discomfort factor calculated during the execution of the steering assist control is accumulated, and if the accumulated value of the discomfort factor is equal to or greater than a predetermined allowable threshold value (step 525: Yes), it is determined that the execution condition is satisfied (step 530, step 430: Yes). It is structured as follows.

[0008] In the device of the present invention, whether or not to execute an override is determined based not only on an input value related to the driver's steering operation but also on the actual output value (actual output value) of the vehicle relative to the input value. Specifically, a discomfort factor (an index showing 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 an integrated value of the discomfort factor calculated during execution of steering assist control is calculated. This discomfort factor integrated value becomes larger the greater the driver's discomfort, and the longer the driver's discomfort continues. The condition for executing an override is met when the integrated value of the discomfort factor becomes equal to or greater than a tolerable threshold value. With this configuration, by appropriately setting the tolerable threshold value, it becomes possible to execute an override within an acceptable range of the driver's discomfort.

[0009] In the above description, in order to facilitate understanding of the invention, the symbols used in the embodiments are added in parentheses to the constituent elements of the invention corresponding to the embodiments, but each constituent element of the invention is not limited to the embodiment defined by the said symbols. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic configuration diagram of a driving assistance device according to an embodiment of the present invention. [Diagram 2] 1 is a graph defining the relationship between driver steering torque and yaw rate, and is a graph for explaining a case in which the driver feels a relatively small sense of discomfort. [Diagram 3] 1 is a graph defining the relationship between driver steering torque and yaw rate, and is a graph for explaining a case in which the driver feels a relatively large sense of discomfort. [Figure 4] 4 is a flowchart showing a routine executed by a CPU of a driving assistance ECU 10 provided in the driving assistance device. [Diagram 5] 13 is a flowchart showing a routine (override determination process) executed by a CPU. [Figure 6] 1 is a graph stored in the ROM of the driving assistance ECU 10, and is a graph for explaining a small discomfort region and a large discomfort region. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] (Embodiment) Hereinafter, a driving assistance device according to the present embodiment (hereinafter also referred to as "the present embodiment device") will be described with reference to the drawings. As shown in FIG. 1, the present embodiment device includes a driving assistance ECU 10 and sensors 11 to 13 connected thereto, a steering ECU 20 and elements 21 and 22 connected thereto, and a brake ECU 30 and elements 31 and 32 connected thereto. Each of these ECUs 10, 20, and 30 includes a microcomputer as a main part, and is connected to each other via a CAN (Controller Area Network) (not shown) so that they can transmit and receive data. Note that ECU is an abbreviation for Electronic Control Unit. The microcomputer includes a CPU, a storage device such as a ROM and a RAM, and an interface (I / F), and the CPU is adapted to realize various functions by executing instructions (programs) stored in the ROM. Hereinafter, a vehicle equipped with this driving assistance device is referred to as a "vehicle". Hereinafter, the driving assistance 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.

[0012] The ECU 10 is connected to an ambient sensor 11 , a vehicle state sensor 12 , and a driving operation sensor 13 .

[0013] The surroundings sensor 11 has a function of acquiring information about at least the road ahead of the vehicle and information about three-dimensional objects on the road. The three-dimensional objects include, for example, moving objects such as pedestrians, bicycles, and automobiles, as well as fixed objects such as utility poles, trees, and guardrails. The surroundings sensor 11 includes, for example, a camera sensor and a radar sensor. The camera sensor is equipped with a stereo camera, photographs the scenery in the front area, and calculates the shape of the road, the presence or absence of a three-dimensional object, and the relative relationship between the vehicle and the three-dimensional object based on the image data obtained by photographing. The camera sensor also recognizes dividing lines extending on the road, and calculates the shape of the road and the positional relationship between the road and the vehicle. The camera sensor may be equipped with a monocular camera instead of a stereo camera. The radar sensor irradiates millimeter wave band radio waves around the vehicle (at least a range including the area in front of the vehicle) and receives reflected waves from a three-dimensional object if one is present. The radar sensor calculates the presence or absence of a three-dimensional object and the relative relationship between the vehicle and the object (the distance from the vehicle to the object, the orientation of the object relative to the vehicle, and the relative speed of the object relative to the vehicle) based on the timing of irradiating and receiving the radio waves. That is, the surroundings sensor 11 acquires information about a three-dimensional object present in front of the host vehicle and a marking line extending in front of the host vehicle.

[0014] Information calculated (acquired) by the surrounding sensor 11 is referred to as surrounding information. The surrounding sensor 11 transmits the surrounding information to the ECU 10 every time a predetermined time has elapsed. 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. Also, information from a navigation system can be used for information indicating the shape of the road on which the vehicle is traveling and the positional relationship between the road and the vehicle.

[0015] The vehicle condition sensor 12 includes a vehicle speed sensor that detects the traveling speed of the vehicle, a wheel speed sensor that detects the wheel speed, a longitudinal G sensor that detects the longitudinal acceleration (acceleration in the longitudinal direction) of the vehicle, a lateral G sensor that detects the lateral acceleration (acceleration in the lateral direction) of the vehicle, and a yaw rate sensor that detects the yaw rate of the vehicle.

[0016] The driving operation sensors 13 include a steering angle sensor that detects a steering angle, a steering torque sensor that detects a steering torque, a brake operation amount sensor that detects an operation amount of a brake pedal, a brake switch that detects whether or not the brake pedal is operated, and a setting switch that sets each driving assistance control, etc. By operating the setting switch, the driver can select whether or not he / she wishes to execute each driving assistance control, and set the control conditions (e.g., vehicle speed). The steering direction (left / right direction) of the steering angle and steering torque is specified by their signs. In addition, the steering angular velocity can be calculated by differentiating the steering angle. The steering direction of the steering velocity is also specified by its sign. In this specification, the steering angle sensor and the steering torque sensor detect the steering angle and steering torque, respectively, that are input based on the driver's steering operation.

[0017] The ECU 10 has a function of executing steering assist control, which includes collision avoidance steering assist control and lane keeping assist control, as driving assist control (described later).

[0018] The ECU 20 is a control device for the electric power steering system, and is connected to a motor driver 21. The motor driver 21 is connected to a steering motor 22. The steering motor 22 is incorporated in a steering mechanism (not shown), and a rotor is rotated by power supplied from the motor driver 21, and the left and right steered wheels are steered by the rotation of the rotor. Under normal circumstances, the ECU 20 causes the steering motor 22 to generate an assist torque corresponding to the steering torque based on the driver's steering operation (i.e., the value detected by the steering torque sensor). 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. For this reason, hereinafter, this sum is referred to as the "driver steering torque ST." The driver steering torque ST corresponds to an example of the "input value related to the driver's steering operation." On the other hand, when ECU 20 receives a steering control command transmitted from ECU 10, it drives and controls steering motor 22 in accordance with the steering control command to steer the steered wheels. Specifically, the steering control command is a command transmitted when steering assist control is executed, and includes a signal indicating a target steering angle. When ECU 20 receives the steering control command, it causes steering motor 22 to generate a torque required to make the steering angle of the steered wheels coincide with the target steering angle. This torque is applied to the steering mechanism when steering assist control is executed. For this reason, hereinafter, this torque is referred to as "control torque CT."

[0019] The ECU 30 is connected to a 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 depression force of the brake pedal, and friction brake mechanisms 32 provided on the left, 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, and the hydraulic pressure of the hydraulic oil supplied from the brake actuator 31 activates a wheel cylinder built into the brake caliper 32b, thereby pressing the brake pad against the brake disc 32a to generate a friction braking force.

[0020] The brake actuator 31 is a known actuator that adjusts the hydraulic pressure supplied to a wheel cylinder built into the brake caliper 32b, and supplies hydraulic pressure to the wheel cylinder in response to a control command from the ECU 30 to generate braking forces on the front, rear, left, right, and right wheels.

[0021] Based on the surrounding information acquired from the surrounding sensor 11, the ECU 10 calculates the shape of the driving lane (the lane in which the vehicle is currently traveling), the position and orientation of the vehicle within the driving lane, and the relative position of a three-dimensional object with respect to the vehicle. Note that a lane may be defined as an area between two adjacent dividing lines. The ECU 10 executes steering assist control when an execution condition (described later) for the steering assist control is satisfied. Furthermore, the ECU 10 ends or cancels the steering assist control when an end condition or a cancellation (interruption) condition (both described later) for the steering assist control is satisfied during the execution of the steering assist control. The steering assist control will be described below using collision avoidance steering assist control and lane keeping assist control as examples. Note that the steering assist control may also include other controls (e.g., lane change assist control).

[0022] (Collision avoidance steering assist control) Collision avoidance steering assist control is a control that applies a control torque to a steering mechanism to avoid a collision with an obstacle when there is a high possibility of a collision with the obstacle. Collision avoidance steering assist control includes emergency steering assist control (ESA) and automatic emergency steering control (AES). Emergency steering assist control is executed when there is a high possibility of a collision with an obstacle and is triggered by a steering operation by the driver, and assists the driver's steering operation so that the host vehicle does not deviate from a marking line (strictly speaking, the left and right marking lines that define the driving lane). Automatic emergency steering control is a control that automatically operates even if the driver does not perform a steering operation when there is a high possibility of a collision with an obstacle.

[0023] Specifically, the ECU 10 calculates the turning radius of the host vehicle based on the yaw rate detected by the yaw rate sensor and the vehicle speed detected by the vehicle speed sensor, and calculates (predicts) the trajectory of the host vehicle based on the turning radius. The ECU 10 also 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 acquired from the surrounding information, and if the object is a moving object, calculates (predicts) the trajectory of the three-dimensional object based on the transition of the position of the three-dimensional object. Then, based on the trajectory of the host vehicle and the trajectory of the three-dimensional object, it determines whether the host vehicle will collide with the three-dimensional object if the host vehicle runs while maintaining the current running state and the three-dimensional object moves while maintaining the current moving state (if the object is stationary, the stationary state). If it is determined that the host vehicle will collide with the three-dimensional object, the ECU 10 recognizes the three-dimensional object as an obstacle and calculates the time that is predicted to be required until the host vehicle collides with the obstacle as the collision prediction time (TTC: Time To Collision). The TTC can be calculated by dividing the distance from the host 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.

[0024] In this case, the ECU 10 calculates a target avoidance trajectory that the host vehicle can take to avoid a collision with the obstacle. The target avoidance trajectory is a trajectory that minimizes the lateral acceleration of the host vehicle among multiple trajectories that can avoid a collision without interfering with the obstacle by turning the host vehicle. Since the calculation method of the target avoidance trajectory is well known, a detailed description thereof will be omitted (for example, refer to JP 2020-26207 A). Note that when the collision avoidance steering assist control is an emergency steering assist control, the target avoidance trajectory is set within the driving lane.

[0025] When the collision avoidance steering assist control is the automatic emergency steering control, the ECU 10 determines that the execution condition for the control is satisfied when both of the following conditions 1A and 2A are satisfied. (Condition 1A) There is a high possibility that the host vehicle will collide with an obstacle. (Condition 2A) A target avoidance trajectory has been calculated. On the other hand, when the collision avoidance steering assist control is emergency steering assist control, the ECU 10 determines that the execution condition for that control is satisfied when the following condition 3A is satisfied in addition to conditions 1A and 2A. (Condition 3A) Steering operation is being performed by the driver. It is possible to determine that condition 3A is 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 conditions for executing the collision avoidance steering assist control are not limited to this.

[0026] When at least one of conditions 1A and 2A is no longer satisfied, the ECU 10 determines that the termination condition of 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 (interruption) condition of the collision avoidance steering assist control is satisfied and cancels (interrupts) the execution of the control. (Condition 4A) The driver is applying the brakes. (Condition 5A) Vehicle Stability Control (VSC) is being executed due to low friction of the road surface. (Condition 6A) Automatic brake control is being executed. Here, the vehicle stabilization control is a well-known control for suppressing skidding of the vehicle, and the automatic brake control is a well-known control for automatically applying a braking force (braking force) to the host vehicle when there is a high possibility that the host vehicle will collide with an obstacle. However, the conditions for ending and canceling the collision avoidance steering assist control are not limited to this.

[0027] (Lane Keeping Assist Control) Lane Tracing Assist (LTA) is a control that applies a control torque to a steering mechanism so that the position of the vehicle is maintained near a target driving line in the driving lane. The ECU 10 determines that the execution conditions for the lane tracing assist control are satisfied when all of the following conditions 1B to 3B are satisfied. (Condition 1B) Execution of lane keeping assist 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 markings. However, the conditions for executing the lane keeping assist control are not limited to this.

[0028] When at least one of the conditions 1B to 3B is no longer satisfied, the ECU 10 determines that the termination condition for the lane keeping assist control is satisfied, and terminates the execution of the control.

[0029] Next, the override will be described. Conventionally, whether or not the override can be executed was determined based only on the input value based on the steering operation of the driver, which may cause the driver to feel uncomfortable. A specific description will be given with reference to Figs. 2 and 3. Figs. 2 and 3 are graphs that define 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 steering operation of the driver" and the "assist torque". The yaw rate YR is a type of physical quantity that determines the behavior of the vehicle.

[0030] In general, when a driver performs a steering operation, the driver expects (anticipates) that the behavior of the vehicle will be realized according to the steering operation. Specifically, when the driver steering torque ST increases (or decreases) due to the driver's steering operation, the driver expects that the yaw rate YR will increase (or decrease) approximately linearly with the increase (or decrease) of the driver steering torque ST. The dashed line BL in the graphs of FIG. 2 and FIG. 3 indicates an ideal relationship between the driver steering torque ST and the yaw rate YR. When the value of the yaw rate YR for an arbitrary driver steering torque ST is located near the dashed line BL, the driver feels that the vehicle is exhibiting a behavior according to the driver's steering operation, and the driver hardly feels uncomfortable. On the other hand, when the value of the yaw rate YR for an arbitrary driver steering torque ST is located at a position away from the dashed line BL, the driver feels that the behavior of the vehicle is deviating (deviation) from the behavior according to the driver's steering operation, and feels uncomfortable. In this embodiment, the dashed line BL is a straight line, but the dashed line BL is not limited to a straight line as long as the dashed line BL has a shape that reflects the relationship between the driver steering torque ST and the yaw rate YR that the driver expects.

[0031] The solid lines SL1 and SL2 in the graphs of FIG. 2 and FIG. 3 indicate the transition of the yaw rate YR when the driver performs a steering operation for a predetermined period during the execution of the steering assist control. Point S corresponds to the start point of the period, and point G corresponds to the end point of the period. In this embodiment, when the driver performs a steering operation during the execution of the steering assist control, a value obtained by adding the driver 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 steering torque ST is applied to the steering mechanism. This yaw rate (that is, the yaw rate when the sum of the control torque CT and the driver steering torque ST is applied to the steering mechanism) corresponds to an example of "the actual output value of the host vehicle with respect to the input value related to the driver's steering operation".

[0032] 2, the solid line SL1 moves in an area away from the broken line BL during a relatively short period within the range D1 from point S to point G, but moves in an area close to the broken line BL during the remaining period. For this reason, the driver may feel some discomfort during the period within the range D1, but will hardly feel any discomfort during the remaining period. 3, the solid line SL2 moves in an area away from the broken line BL for a relatively long period (the period moving within the range D2) from the point S to the point G. For this reason, it is considered that the driver feels a sense of discomfort for a relatively long period.

[0033] Therefore, in conventional configurations in which the determination of whether or not to execute an override is based solely on input values ​​based on the driver's steering operation, situations may arise in which the behavior of the vehicle deviates significantly or for a long period of time from the behavior expected by the driver during the period leading up to the override being executed, causing the driver to feel uncomfortable (in other words, the sense of discomfort may exceed the acceptable range).

[0034] Therefore, in this embodiment, the ECU 10 is configured to determine whether or not to execute an override based not only on input values ​​(input values ​​including assist torque) related to the steering operation of the driver, but also on physical quantities (output values) that determine the behavior of the vehicle. Specific operations of the ECU 10 will be described below with reference to Figs. 4 and 5.

[0035] The CPU of the ECU 10 is configured to repeatedly execute the routines shown in the flowcharts of FIG. 4 and FIG. 5 every time a predetermined time elapses while the ignition switch is in the ON state.

[0036] At a predetermined timing, the CPU starts processing from step 400 in Fig. 4 and proceeds to step 410, where it determines whether or not steering assist control is being executed based on whether or not the execution conditions for the above-mentioned steering assist control (in this embodiment, collision avoidance steering assist control or lane keeping assist control) are satisfied. If steering assist control is not being executed (step 410: No), the CPU proceeds to processing in step 495 and temporarily ends this routine. On the other hand, if steering assist control is being executed (step 410: Yes), the CPU proceeds to processing in step 420 and performs override determination processing.

[0037] When the CPU proceeds to step 420, it starts the process from step 500 in Fig. 5 and proceeds to step 505 to determine whether the current time is included in the override effective period. That is, since the steering system dynamically fluctuates during a predetermined specific period after the steering assist control is started, the detection value of the steering torque sensor is likely to become high due to the influence of inertia and / or road surface friction, making it difficult to determine whether the driver wants to override. For this reason, the system is configured not to determine whether or not an override can be executed during the specific period. The override effective period is the period during which the steering assist control is executed excluding the specific period (i.e., the period during which it can be appropriately determined whether or not the driver wants to override).

[0038] The specific period may be set for each type of steering assist control. For example, after the start of collision avoidance steering assist control, the degree of fluctuation of the steering system is greater than that after the start of lane keeping assist control. For this reason, the specific period of the collision avoidance steering assist control may be set longer than the specific period of the lane keeping assist control (the specific period may be set to zero because the effect of inertia is relatively small in lane keeping assist control). In addition, when lane return assist control (control for applying a control torque to the steering mechanism so that the host vehicle does not deviate from the lane) is performed after the end of collision avoidance steering assist control, the system may be configured not to determine whether or not to execute the override even in another predetermined specific period including the time when the lane return assist control is started (for details, see JP 2020-26207 A).

[0039] If the current time is not included in the override valid period (i.e., 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 when determining whether an override can be executed, and a value of 0 indicates that an override is not executed (not permitted), and a value of 1 indicates that an override is executed (permitted). The CPU then proceeds to step 595 to end the override determination process, and proceeds to step 430 in FIG. 4 (described later).

[0040] 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 determines whether the value (actual output value) of the yaw rate YR relative to the driver steering torque ST (input value) at the current time is located within the large discomfort region R2 by referring to the graph in FIG. 6. Before describing the process of step 515, the graph in 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 "small discomfort region R1" and a "large discomfort region R2". The small discomfort region R1 is the region near the broken line BL (i.e., the region where the driver is unlikely to feel discomfort) (see the gray part). When the equation of the broken line BL is defined as y=mx (m: gradient), the small discomfort region R1 is the region that satisfies mx-b1≦y≦mx+b2. When the value of the yaw rate YR relative to the driver steering torque ST at the current time is located in the small discomfort region R1, the driver feels that the vehicle is behaving in accordance with the driver's steering operation. Therefore, the value of the yaw rate YR in the small discomfort region R1 can be said to be the output value (expected output value) of the vehicle that the driver expects based on the driver's steering operation. In other words, the above inequality (mx-b1≦y≦mx+b2) that defines the small discomfort region R1 corresponds to an example of a "relationship that defines the relationship between the input value related to the driver's steering operation and the expected output value of the vehicle that the driver expects based on the steering operation". The constants b1 and b2 can be set in advance based on an experiment or simulation. In this embodiment, b1=b2, but b1≠b2 may also be satisfied. In addition, hereinafter, the value of the yaw rate YR relative to the driver steering torque ST at the current time is also referred to as "coordinate (ST, YR)".

[0041] On the other hand, the large discomfort area R2 is an area separated from the broken line BL (i.e., an area where the driver is likely to feel discomfort), and satisfies y < mx - b1 or mx + b2 < y. For example, when the coordinates (ST, YR) are located at positions P1, P2, or P3 respectively, since all of these are located within the large discomfort area R2, the driver feels discomfort. Specifically, when the coordinates (ST, YR) are located at position P1, the driver feels discomfort due to the excessive turning of the host vehicle with respect to the driver's steering operation; when the coordinates (ST, YR) are located at position P2, the driver feels discomfort due to the small degree of turning of the host vehicle with respect to the driver's steering operation; when the coordinates (ST, YR) are located at position P3, the driver feels discomfort due to the host vehicle turning in the direction opposite to the direction in which it should turn by the driver's steering operation.

[0042] The ECU 10 stores the graph of FIG. 6 in the ROM. The CPU refers to the graph stored in the ROM and determines whether the value of the yaw rate YR with respect to the driver steering torque ST at the current time (coordinates (ST, YR)) is located within the large discomfort area R2. Note that the ECU 10 may be configured to store the above inequality that defines the small discomfort area R1 in the ROM instead of the graph of FIG. 6.

[0043] If the current coordinate (ST, YR) is located within the large discomfort region R2 (step 515: Yes), the CPU proceeds to step 520 and calculates the integrated value of the discomfort factor. The discomfort factor is an index indicating the degree of discomfort felt by the driver with respect to the behavior (output, response) of the vehicle. The larger the discomfort factor, the greater the degree of discomfort felt by the driver. In this embodiment, the discomfort factor is defined as |ΔYR·ST| (where "·" represents a multiplication symbol). Here, ΔYR represents the distance in the y-axis direction between the coordinate (ST, YR) and the discomfort small region R1 (in other words, the amount of deviation of the yaw rate YR from the region R1). For example, as shown in FIG. 6, when the current coordinate (ST, YR) is located at position Pe, ΔYR is equal to the distance in the y-axis direction from 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 discomfort small region R1.

[0044] Specifically, in step 520, the CPU calculates an discomfort factor (=|ΔYR·ST|) based on the coordinates (ST, YR) of the current time, and adds that value to the discomfort factor (initial value: zero) stored in the RAM. This calculates an integrated value of the discomfort factors (excluding the values ​​reset in step 550, described later) calculated during the period from the start of the currently executed steering assist control to the current time. The CPU stores the discomfort factor integrated value calculated in this manner in the RAM. In addition, if the value of timer T is not the initial value (zero), the CPU resets (initializes) the value of timer T (described later).

[0045] The discomfort factor is not limited to this, and may be defined as |ΔST|, where ΔST represents the distance in the x-axis direction between the coordinate (ST, YR) and the discomfort small region R1 (in other words, the amount of deviation of the driver steering torque ST from the region R1). Moreover, the physical quantity that determines the behavior of the vehicle includes the lateral acceleration LA or the steering angle SA in addition to the yaw rate YR. Therefore, instead of the graph in Fig. 6, a small discomfort region R1 and a large discomfort region R2 may be partitioned in a graph that defines the relationship between the driver steering torque ST and the lateral acceleration LA, and the discomfort factor may be defined as |ΔLA·ST|. Here, ΔLA represents the distance in the y-axis direction between the coordinate (ST, LA) and the small discomfort region R1 (in other words, the amount of deviation of the lateral acceleration LA from the region R1). Alternatively, instead of the graph in Fig. 6, a small discomfort region R1 and a large discomfort region R2 may be partitioned in a graph defining the relationship between the driver steering torque ST and the steering angle SA, and the discomfort factor may be defined as |ΔSA·ST|, where ΔSA represents the distance in the y-axis direction between the coordinate (ST, SA) and the small discomfort region R1 (in other words, the amount of deviation of the steering angle SA from the region R1). Furthermore, a discomfort factor may be defined that incorporates two or more of the above physical quantities (yaw rate YR, lateral acceleration LA, and steering angle SA) by making them dimensionless.

[0046] Next, the CPU proceeds to step 525 and determines whether the discomfort factor integrated value calculated in step 520 is equal to or greater than a predetermined tolerance threshold. The tolerance threshold is an upper limit of an acceptable range of discomfort for the driver, and may be set in advance by experiment or simulation. If the discomfort factor integrated value is less than the tolerance threshold (step 525: No), the CPU proceeds to step 510. In step 510, the CPU determines that the driver's discomfort is still within the acceptable range, and sets the value of the override flag to 0. Thereafter, the CPU proceeds to step 595 to end the override determination process, and proceeds to step 430 in FIG. 4.

[0047] In step 430, the CPU determines whether the value of the override flag is 1. If the value of the override flag is 0 (step 430: No), the CPU proceeds to step 440 and determines whether the above-mentioned termination condition or cancellation condition of the steering assist control is satisfied. If the termination condition or cancellation condition is satisfied (step 440: Yes), the CPU proceeds to step 450 and terminates or cancels the steering assist control. Next, the CPU proceeds to step 460 and resets the discomfort factor integrated value, and resets the value of timer T if the value of timer T is not the initial value. Then, the CPU proceeds to step 495 and temporarily ends this routine.

[0048] On the other hand, if the termination condition or the cancellation condition is not satisfied (step 440: No), the CPU advances the process to step 495 and temporarily ends this routine. That is, the CPU continues to execute the steering assist control without executing the override while retaining the discomfort factor integrated value (and the value of the timer T if the value of the timer T is not the initial value).

[0049] If the discomfort factor integrated value becomes equal to or greater than the tolerance threshold during the process of repeating the above process (processing in which the execution of steering assist control is continued because the discomfort factor integrated value is less than the tolerance threshold and the override flag value is 0, and the termination condition or cancellation condition of the steering assist control is not satisfied), the CPU proceeds to step 530. In step 530, the CPU determines that the driver's discomfort has exceeded the tolerance range (i.e., the override execution condition is satisfied) and sets the value of the override flag to 1. The CPU then proceeds to step 595 to end the override determination process, and proceeds to step 430 in FIG. 4.

[0050] 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 given priority. Next, the CPU proceeds to step 460 and resets the discomfort factor integrated value and the value of the timer T (if not the initial value). Then, the CPU proceeds to step 495 and ends this routine.

[0051] In contrast, when the current coordinate (ST, YR) moves to the small discomfort region R1 during the process of repeating the above process (step 515: No), the CPU proceeds to step 535 and determines whether the discomfort factor integrated value stored in the RAM is positive. Here, "the discomfort factor integrated value is positive" means that there is a period during which the coordinate (ST, YR) was located in the large discomfort region R2 during the execution of the current steering assist control. On the other hand, "the discomfort factor integrated value is not positive" means that the discomfort factor integrated value is zero, which means that the coordinate (ST, YR) was always located in the small discomfort region R1 during the execution of the current steering assist control (i.e., there was no period during which it was located in the region R2). Strictly speaking, even if the coordinate (ST, YR) is located in the large discomfort region R2, if the value of the x coordinate (=ST) is zero, the discomfort factor is zero. Such an event is considered to occur temporarily while the driver is performing a steering operation; however, since it is difficult to imagine a situation in which the x-coordinate value is always zero during the period in which the coordinate (ST, YR) is located in the large discomfort region R2, such a event is not taken into consideration in this embodiment.

[0052] If the discomfort factor integrated value is positive (step 535: Yes), the CPU proceeds to step 540, starts a timer T (initial value: zero), and starts counting up the "period during which the coordinates (ST, YR) are located in the discomfort small region R1 and the discomfort factor integrated value is positive." The CPU then proceeds to step 545, and determines whether the value of the timer T has reached a predetermined time threshold Tth (T≧Tth is satisfied). The time threshold Tth is the upper limit of the effective time that can be used to determine whether or not the discomfort factor integrated value can be overridden. That is, when the value of the timer T reaches the time threshold Tth, the discomfort factor integrated value becomes invalid and is reset (described later). If the value of the timer T has not yet reached the time threshold value Tth (step 545: No), the CPU proceeds to step 510 while retaining the discomfort factor integrated value and the value of the timer T, and sets the value of the override flag to 0. The subsequent processing is as described above.

[0053] In contrast, if the coordinate (ST, YR) is always located in the discomfort small region R1 during the execution of the current steering assist control (step 515: No), the CPU proceeds to step 535. In this case, the discomfort factor integrated value remains zero (initial value) (step 535: No), so the CPU proceeds to step 510 and sets the value of the override flag to 0. The subsequent processing is as described above.

[0054] If the coordinates (ST, YR) move again into the large discomfort region R2 before the value of the timer T reaches the time threshold Tth (step 515: Yes), the CPU proceeds to step 520 and adds the discomfort factor calculated at the current time to the discomfort factor integrated value stored in the RAM to update the discomfort factor integrated value. In addition, if the coordinates (ST, YR) move from the large discomfort region R2 to the small discomfort region R1 and then return to the large discomfort region R2, the CPU resets the value of the timer T. Subsequent processing is as described above.

[0055] On the other hand, if the value of the timer T reaches the time threshold value Tth (step 545: Yes), the CPU proceeds to step 550. In step 550, the CPU determines that the discomfort factor integrated value has become invalid, and resets the integrated value and the value of the timer T. Next, the CPU proceeds to step 510, and sets the value of the override flag to 0. The subsequent processing is as described above.

[0056] As described above, in this embodiment, whether or not to execute an override is determined based not only on the driver steering torque ST (i.e., an input value related to the driver's steering operation) but also on the yaw rate YR (the actual output value for the input value). Specifically, a discomfort factor is calculated based on the value of the yaw rate YR for the current driver steering torque ST (i.e., the coordinates (ST, YR)), and an integrated value of the discomfort factor calculated during the current execution of steering assist control is calculated. This discomfort factor integrated value becomes larger as the driver's discomfort becomes greater, and becomes larger the longer the driver's discomfort continues. An override is executed when the discomfort factor integrated value becomes equal to or greater than a tolerable threshold value. According to this configuration, by appropriately setting the tolerable threshold value, an override can be executed within an acceptable range of the driver's discomfort.

[0057] 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.

[0058] For example, the shape of the discomfort small region R1 is not limited to the shape shown in the graph of FIG. 6. For example, the width in the y-axis direction between the boundary line B1 on the +y-axis side of the discomfort small region R1 and the broken line BL, and the width in the y-axis direction between the boundary line B2 on the -y-axis side and the broken line BL may be curved so that they become narrower as the magnitude |ST| of the driver steering torque ST approaches zero and become wider as |ST| increases. Alternatively, the equation of the broken line BL may be a curved equation in which the differential coefficient becomes smaller as the driver steering torque ST increases in the first quadrant and converges to a predetermined yaw rate YR. In this case, the equation of the broken line BL in the third quadrant is point-symmetric with the equation of the broken line BL in the first quadrant with respect to the origin.

[0059] In the above embodiment, when the coordinate (ST, YR) moves from the large discomfort region R2 to the small discomfort region R1, the discomfort factor integrated value is reset when the period during which the coordinate (ST, YR) remains in the small discomfort region R1 reaches the time threshold Tth, but the method of resetting the integrated value is not limited to this. For example, when the coordinate (ST, YR) moves from the large discomfort region R2 to the small discomfort region R1, the ECU 10 may calculate the integrated value of the no discomfort factor. The no discomfort factor is an index indicating the degree to which the driver does not feel discomfort with respect to the behavior (output, response) of the host vehicle. The larger the no discomfort factor, the less discomfort the driver feels. The no discomfort factor may be specified as, for example, |ΔYR| or |ΔST|. In this case, ΔYR is the shorter of the distances in the y-axis direction between the coordinate (ST, YR) in the discomfort small region R1 and the boundary line of the region R1, and ΔST is the shorter of the distances in the x-axis direction between the coordinate (ST, YR) in the discomfort small region R1 and the boundary line of the region R1. The ECU 10 may be configured to reset the discomfort factor integrated value when the integrated value of the no discomfort factor becomes equal to or greater than a predetermined threshold value.

[0060] 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 this is not the only possible configuration. For example, the discomfort factor may be calculated to be zero when the coordinates (ST, YR) are located within the discomfort small region R1.

[0061] Furthermore, the configuration of the present invention can also be applied to a steer-by-wire type vehicle. [Explanation of symbols]

[0062] 10: driving assistance ECU, 11: surrounding 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

[Claim 1] a surrounding information acquisition means for acquiring information on a three-dimensional object present in front of the vehicle and a lane marking extending in front of the vehicle as surrounding information; a steering assist control execution means for executing a steering assist control for assisting a steering operation of a driver of the host vehicle based on at least the surrounding information; an override execution means for determining whether or not an override execution condition for canceling the steering assist control during execution of the steering assist control and prioritizing the steering operation of the driver is satisfied, and for executing the override if the execution condition is satisfied; a relational equation storage means for storing in advance a relational equation that defines a relationship between an input value related to a steering operation of the driver and an expected output value of the vehicle that the driver expects based on the steering operation; a discomfort factor calculation means for calculating a discomfort factor, which is an index showing a degree of discomfort felt by the driver with respect to the behavior of the vehicle, as a value that increases as an actual output value of the vehicle corresponding to the input value deviates from the expected output value for the input value; Equipped with The override execution means includes: The discomfort factor calculated during the execution of the steering assist control is integrated, and it is determined that the execution condition is satisfied when the integrated value of the discomfort factor is equal to or greater than a predetermined allowable threshold value. It was configured as follows: Driving assistance device.

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