JP5780420B2 - Brake control device for vehicle - Google Patents

Description

  The present invention relates to a vehicular brake control device, and more particularly to a vehicular brake control device that can change a release mode of automatic braking in accordance with a driver's operation.

  2. Description of the Related Art Conventionally, a device that performs so-called automatic braking when the risk of collision between the host vehicle and an obstacle increases has been developed in order to avoid a collision between the host vehicle and the obstacle. Automatic braking refers to braking control that controls a vehicle braking device regardless of a driver's operation to generate an automatic braking force on the host vehicle.

  An example of an apparatus that performs automatic braking as described above is disclosed in Patent Document 1. The vehicular braking force generator disclosed in Patent Literature 1 determines whether or not the driver intends to steer in response to an operation of an accelerator pedal or the like by the driver. If it is determined that the driver is willing to steer, automatic braking is stopped. According to such a process, when the automatic braking is executed at an unnecessary timing, the unnecessary automatic braking can be stopped according to the driver's operation.

JP 2004-314848 A

  However, with the conventional technology, there is a case where the host vehicle cannot be properly braked. Specifically, in the vehicle braking force generator according to Patent Document 1, when the driver performs a steering operation, the generation of the braking force is released immediately (suddenly), and thus the vehicle behavior may become unstable. was there.

  On the other hand, if the generation of the braking force is continued after the steering operation in consideration of such a problem, the host vehicle may be decelerated too much, and, for example, the acceleration of the host vehicle 100 may be hindered in the situation shown in FIG. It is thought that there is. FIG. 4 is a diagram illustrating an example of a situation in which the host vehicle 100 cannot be braked appropriately with the conventional technology. In FIG. 4, the driver of the host vehicle 100 traveling in the traveling lane A performs a steering operation to change the lane to the adjacent lane B in order to avoid a collision with the preceding vehicle 200 traveling at a relatively slow speed. went. Here, when the succeeding vehicle 300 is traveling on the adjacent lane B from the rear of the host vehicle 100 at a relatively high speed, the host vehicle 100 needs to accelerate quickly so as not to hinder the travel of the subsequent vehicle 300.

  However, if the generation of the braking force is continued after the steering operation as described above, the host vehicle 100 may not be able to perform sufficient acceleration as shown in FIG. FIG. 5 is a graph showing a situation where the host vehicle 100 equipped with the conventional braking control device is not appropriately accelerated / brake controlled under the situation shown in FIG. (A) of FIG. 5 shows a time-dependent change of the accelerator opening degree of the own vehicle 100 provided with the conventional braking control apparatus. FIG. 5B shows a change over time of the braking force due to automatic braking generated in the host vehicle 100 equipped with a conventional braking control device. (C) of FIG. 5 shows the time-dependent change of the acceleration to the advancing direction of the own vehicle 100 provided with the conventional braking control apparatus. 5A to 5C all indicate the same time axis. As shown in FIG. 5B, if the generation of braking force by automatic braking is continued after the steering operation is performed (after time t2), the driver depresses the accelerator as shown in FIG. 5A. Even if the accelerator opening is increased, the host vehicle 100 cannot be accelerated quickly as shown in FIG. As described above, in the conventional technology, appropriate vehicle braking control cannot be performed in the situation shown in FIGS.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a vehicle brake control device that enables more appropriate vehicle brake control than before.

  In order to solve the above problems, the present application adopts the following configuration. That is, the first invention is a vehicle braking control device that automatically brakes a vehicle in accordance with the risk of collision between the host vehicle and an obstacle, and has a high risk of collision between the host vehicle and the obstacle. A collision determination means for determining whether or not the collision determination means determines that there is a high risk of a collision between the host vehicle and an obstacle, and an automatic braking means for automatically generating a braking force on the host vehicle; Braking force gradually decreasing means for gradually decreasing the magnitude of the braking force generated by the automatic braking means according to the steering operation of the driver of the host vehicle, and the braking force gradually decreasing means is configured to control the gradually decreasing speed of the braking force of the driver of the host vehicle. A braking control device for a vehicle characterized in that the braking control device is made faster in response to an operation.

  In a second aspect based on the first aspect, the braking force gradual decrease means determines the gradual decrease rate of the braking force when the driver of the host vehicle depresses the accelerator pedal after starting the gradual decrease of the braking force. It is characterized in that it is faster than when there is no operation to step on.

  In a third aspect based on the second aspect, the braking force gradual reduction means includes an operation of depressing the accelerator pedal by the driver of the own vehicle when the accelerator opening of the own vehicle is equal to or larger than a predetermined opening threshold. It is characterized by determining that it was.

  In a fourth aspect based on the second aspect, the braking force gradual reduction means is configured such that when the driver of the own vehicle depresses the accelerator pedal for a predetermined time or longer, the operation of depressing the accelerator pedal by the driver of the own vehicle is performed. It is determined that there was.

  According to the first invention, when there is a steering operation for avoiding a collision, when the driving of the vehicle is stabilized by gradually decreasing the braking force and the driver intends to accelerate the vehicle at that time Can quickly reduce the braking force and accelerate the host vehicle. Therefore, it is possible to control the braking of the vehicle more appropriately than the conventional technology. According to such a process, for example, after changing the lane to an adjacent lane so as to avoid a collision with a preceding vehicle, it is possible to suppress the risk of a rear-end collision from a subsequent vehicle.

  According to the second aspect of the present invention, the braking force is gradually increased only when there is an operation of depressing the accelerator pedal after starting to gradually reduce the braking force, that is, when the driver intends to accelerate the host vehicle. Control is performed. In other words, if the accelerator pedal has already been depressed when the braking force gradually starts to be reduced, that is, if it is not clear whether the driver intends to accelerate the vehicle, the braking force gradually decreases. There is no control to speed up. Therefore, the presence or absence of the driver's intention to accelerate can be detected more accurately, and more accurate braking control can be performed.

  According to the third invention, it is possible to easily determine whether or not the driver has depressed the accelerator by a simple process using the accelerator opening and the threshold value.

  According to the fourth aspect of the invention, the braking force can be gradually reduced only when the driver performs an operation of continuously depressing the accelerator pedal for a predetermined time (a so-called solid stepping operation).

An example of a block diagram showing a configuration of a vehicle brake control device 1 according to an embodiment of the present invention An example of the flowchart which shows the detail of the process which ECU20 which concerns on embodiment of this invention performs The graph which shows a mode that the own vehicle provided with the vehicle brake control apparatus 1 which concerns on embodiment of this invention is appropriately accelerated / brake-controlled under the condition shown in FIG. The figure which shows an example of the condition which cannot brake the own vehicle 100 appropriately by the prior art FIG. 4 is a graph showing a situation in which acceleration / brake control is not properly performed under the situation shown in FIG.

  Hereinafter, a vehicle brake control device 1 according to an embodiment of the present invention will be described. The vehicle braking control device 1 is a device that starts and releases automatic braking in accordance with the risk of collision between the host vehicle and an obstacle and the vehicle operation of the driver. Note that automatic braking refers to braking control that controls a vehicle braking device regardless of a driver's operation to generate an automatic braking force on the host vehicle.

  First, the configuration of the vehicle brake control device 1 will be described with reference to FIG. FIG. 1 is an example of a block diagram showing the configuration of the vehicle brake control device 1. As shown in FIG. 1, the vehicle brake control device 1 includes a radar device 11, an accelerator device 12, a steering sensor 13, an ECU 20, and a brake actuator 30.

  The radar device 11 is a device that detects an obstacle by transmitting an electromagnetic wave around the vehicle and receiving the electromagnetic wave reflected by the obstacle. The radar device 11 is typically an FM-CW millimeter-wave radar device, and is mounted, for example, at the front end of the host vehicle. When the radar device 11 detects an obstacle, the radar device 11 detects the obstacle information. Specifically, the radar device 11 detects, as obstacle information, a relative speed Vr (km / h) with respect to the host vehicle and a distance L (km) from the obstacle to the host vehicle. The radar apparatus 11 transmits data indicating the relative speed Vr and the distance L to the collision determination ECU 20. As a method for the radar device 11 to detect the relative speed Vr and the distance L, any conventionally known method may be used.

  The accelerator device 12 is a device that accepts an input operation from the driver of the host vehicle and accelerates the host vehicle. The driver performs the input operation by stepping on an accelerator pedal provided in the accelerator device 12. The accelerator device 12 transmits to the collision determination ECU 20 a value of the accelerator opening ω that increases or decreases according to the amount of depression of the accelerator pedal by the driver. It is assumed that the accelerator opening ω increases as the driver depresses the accelerator pedal deeper.

  The steering sensor 13 is a sensor device that detects the steering angle θ of the host vehicle. The steering angle θ is a parameter that changes according to the steering operation by the driver of the host vehicle. The steering sensor 13 transmits data indicating the detected steering angle θ to the collision determination ECU 20. In addition, as a method for the steering sensor 13 to detect the steering angle θ, any conventionally known method may be used.

  The ECU 20 is a control device that instructs the brake actuator 30 to execute and stop automatic braking based on information obtained from the radar device 11, the accelerator device 12, and the steering sensor 13. The ECU 20 is typically a control device including an information processing device such as a CPU (Central Processing Unit), a storage device such as a memory, an interface circuit, and the like. Details of the process executed by the collision determination ECU 20 will be described later.

  The brake actuator 30 is a device that automatically increases the braking force by the braking device mounted on the host vehicle. The brake actuator 30 is typically an actuator pump that pressurizes brake fluid in a wheel cylinder of a hydraulic brake device mounted on the host vehicle. The brake actuator 30 increases the braking force of the host vehicle by increasing the hydraulic pressure in the wheel cylinder of the hydraulic brake device in accordance with an instruction from the ECU 20 (regardless of the operation of the driver). The configuration of the brake actuator 30 is merely an example, and any device may be used as long as the device can automatically generate a braking force on the host vehicle in accordance with an instruction from the ECU 20.

  Next, processing executed by the ECU 20 will be described. The ECU 20 starts automatic braking based on information obtained from the radar device 11 or the like. Then, the ECU 20 releases the automatic braking based on information obtained from the accelerator device 12 and the steering sensor 13 or the like. Hereinafter, the process executed by the ECU 20 will be described in detail with reference to FIG. FIG. 2 is an example of a flowchart showing details of processing executed by the ECU 20 according to the embodiment of the present invention. For example, when the user turns on the operation of the automatic braking system by an input device (not shown) provided in the host vehicle, the ECU 20 executes the process of FIG. When the process of the flowchart of FIG. 2 is started, the ECU 20 first executes a process of step S1. Note that the ECU 20 repeatedly executes the processing from step S1 to step S14 shown below as one cycle while the automatic braking system is in the on state.

  In step S1, the ECU 20 determines whether an obstacle has been detected. Specifically, the ECU 20 determines whether obstacle information has been received from the radar device 11. When the obstacle information is received, the ECU 20 determines that an obstacle has been detected, and advances the process to step S2. On the other hand, when the obstacle information is not received, the ECU 20 determines that no obstacle is detected, and advances the process to step S14.

In step S2, the ECU 20 determines whether the risk of collision is high. The ECU 20 determines whether or not there is a high risk that the obstacle and the host vehicle collide. Specifically, the ECU 20 first calculates a time that is expected to be required until the obstacle collides with the host vehicle (hereinafter, referred to as a predicted collision time TTC). More specifically, the ECU 20 uses the relative speed Vr and the distance L received from the radar device 11 in step S1, and calculates the predicted collision time TTC based on the equation (1).
TTC = L / Vr (1)
Next, the ECU 20 determines whether or not the predicted collision time TTC is shorter than a predetermined threshold value TTCth. Then, when the predicted collision time TTC is shorter than a predetermined threshold value TTCth, the ECU 20 determines that there is a high risk of collision between the obstacle and the host vehicle, advances the process to step S3, and starts automatic braking. On the other hand, when the predicted collision time TTC is longer than the predetermined threshold value TTCth, the ECU 20 determines that the risk of collision between the obstacle and the host vehicle is low, and advances the processing to step S4. Note that the process of step S2 is an example, and the ECU 20 may determine whether or not there is a high risk of collision between the obstacle and the host vehicle.

  In step S3, the ECU 20 starts automatic braking. Specifically, the ECU 20 controls the brake actuator 30 so as to continuously generate the automatic braking force P. Note that the ECU 20 may arbitrarily set the value of the braking force P. When the ECU 20 completes the process of step S3, the process proceeds to step S14.

  In step S4, the ECU 20 determines whether or not automatic braking is being executed. When it is determined that automatic braking is being executed, the ECU 20 advances the process to step S5 and releases the automatic braking in a manner corresponding to the driver's operation. On the other hand, if the ECU 20 determines that automatic braking is not being executed, the ECU 20 advances the process to step S14.

  In step S5, the ECU 20 acquires the accelerator opening ω from the accelerator device 12, and stores it in the storage device. When the ECU 20 completes the process of step S5, the process proceeds to step S6.

  In step S6, the ECU 20 determines whether or not a steering operation for avoiding a collision (hereinafter referred to as an avoidance steering operation) has been performed by the driver of the host vehicle. For example, the ECU 20 always obtains and stores the steering angle θ from the steering sensor 13 in advance, and calculates the amount of change per unit time of the steering angle θ. And when the variation | change_quantity of the said steering angle (theta) is more than a predetermined threshold value from the time of the automatic braking start to the present time, it determines with there being an avoidance steering operation. Note that the above processing is an example, and any conventionally known method may be used as long as it can be determined whether or not an avoidance steering operation is performed. When it is determined that the avoidance steering operation has been performed, the ECU 20 advances the process to step S9 and determines whether or not the driver has performed an accelerator operation. On the other hand, if the ECU 20 determines that there is no avoidance steering operation, the process proceeds to step S7.

  In step S7, the ECU 20 sets the value of the braking force gradually decreasing speed F to α. The braking force gradual decrease rate F is a decrease amount per unit time of the braking force P when the automatic braking is released. That is, the larger the value of the braking force gradual decrease speed F, the faster the braking force P for automatic braking becomes smaller. Α is an arbitrary constant stored in advance in the storage device of the ECU 20. When the process of step S7 is completed, the ECU 20 advances the process to step S8 and controls the braking force according to the set braking force gradual decrease speed F.

  In step S8, the ECU 20 executes braking force gradual reduction control. Specifically, the ECU 20 updates and calculates a value obtained by subtracting a value corresponding to the value of the braking force gradual decrease speed F from the current value of the braking force P as a new braking force P, and adds the updated braking force P to the updated braking force P. An instruction signal for generating a corresponding braking force is transmitted to the brake actuator 30. When the ECU 20 completes the process of step S8, the process proceeds to step S14.

  In step S9, the ECU 20 calculates an opening change amount Δω. The opening change amount Δω is a change amount of the accelerator opening ω per unit time. For example, the ECU 20 calculates a value obtained by subtracting the accelerator opening ω stored in the previous processing cycle from the accelerator opening ω acquired in the current processing cycle as the opening change amount Δω. The value of the opening change amount Δω increases when the driver depresses the accelerator pedal. When the ECU 20 completes the process of step S9, the process proceeds to step S10.

  In step S10, the ECU 20 determines whether or not the opening change amount Δω is equal to or greater than the change amount threshold value Δωth. The change amount threshold value Δωth is a threshold value for determining whether or not the driver has performed an operation of depressing the accelerator pedal based on the opening amount change amount Δω. The change amount threshold value Δωth is an arbitrary constant stored in advance in the storage device of the ECU 20. If the ECU 20 determines that the opening change amount Δω is equal to or greater than the change amount threshold value Δωth, the ECU 20 advances the process to step S11. On the other hand, if the ECU 20 determines that the opening degree change amount Δω is smaller than the change amount threshold value Δωth, the process proceeds to step S12.

  In step S11, the ECU 20 determines whether or not the accelerator opening ω acquired in the current processing cycle is equal to or larger than the opening threshold ωth. The opening degree threshold value ωth is a threshold value for determining whether or not the driver has performed an operation of depressing the accelerator pedal based on the accelerator opening degree ω. The opening degree threshold value ωth is an arbitrary constant stored in advance in the storage device of the ECU 20. If the accelerator opening ω is greater than or equal to the opening threshold ωth, the ECU 20 determines that there has been an operation of depressing the accelerator pedal, and advances the process to step S13. On the other hand, if the ECU 20 determines that the accelerator opening ω is smaller than the opening threshold ωth, the ECU 20 advances the process to step S12.

  In step S12, the ECU 20 sets the value of the braking force gradual decrease speed F to β. β is a constant value smaller than α and is stored in the storage device of the ECU 20 in advance. When the processing of step S12 is completed, the ECU 20 advances the processing to step S8 and controls the braking force according to the set braking force gradual decrease rate F.

  In step S13, the ECU 20 sets the value of the braking force gradual decrease speed F to γ. γ is a constant value larger than β and is stored in the storage device of the ECU 20 in advance. When the processing of step S13 is completed, the ECU 20 advances the processing to step S8 and controls the braking force according to the set braking force gradual decrease rate F.

  According to the processing from step S6 to step S13, when the driver performs only the avoidance steering operation (Yes in step S6 and No in steps S10 and 11), when the driver does not perform the avoidance steering operation (in step S6). As compared with No), the braking force gradual decrease speed F is set to a relatively small value. Therefore, the braking force P for automatic braking is gradually reduced, and the traveling stability of the host vehicle can be ensured. On the other hand, when the driver performs an accelerator operation after performing the avoidance steering operation (Yes in steps S6, 10 and 11), when the driver performs only the avoidance steering operation (Yes in step S6 and in steps S10 and 11) The braking force gradually decreasing speed F is set to a relatively large value as compared with No). Therefore, the host vehicle can be quickly accelerated under a situation where the host vehicle needs to be accelerated by appropriately changing the value of the braking force gradually decreasing speed F in accordance with the driver's vehicle operation.

  In step S14, the ECU 20 determines whether or not the automatic braking system is set to an off state. When the ECU 20 determines that the automatic braking system is set to the off state, the ECU 20 ends the process of FIG. On the other hand, when it is determined that the automatic braking system is maintained in the on state, the ECU 20 returns the process to step S1 and repeatedly executes the processes of the above steps.

  The manner in which braking of the host vehicle is appropriately controlled by the vehicle brake control device 1 described above will be described with reference to FIG. FIG. 3 is a graph showing how the host vehicle including the vehicle brake control device 1 according to the embodiment of the present invention is appropriately accelerated / brake controlled under the situation shown in FIG. (A) of FIG. 3 shows a time-dependent change of the accelerator opening degree (omega) of the own vehicle 100 provided with the vehicle braking control apparatus 1 which concerns on this invention. FIG. 3B shows a change with time of the braking force P due to automatic braking generated in the host vehicle 100 including the vehicle braking control apparatus 1 according to the present invention. (C) of FIG. 3 shows the time-dependent change of the acceleration AC to the advancing direction of the own vehicle 100 provided with the vehicle brake control device 1 according to the present invention. Note that the horizontal axes in FIGS. 3A to 3C all indicate the same time axis.

  First, when the braking control is started at time t1, the value of the braking force P increases as shown in FIG. 3B, and accordingly, the acceleration AC of the host vehicle increases as shown in FIG. 3C. Decreases. Thereafter, when the driver performs the avoidance steering operation at time t2, as shown in FIG. 3B, the value of the braking force P is set to β, and the value of the braking force gradual decrease rate F is set to β. The value of decreases. Thereafter, at time t4, when it is determined that the driver has stepped on the accelerator to increase the accelerator opening by the processing from step S9 to step S11 ((a) of FIG. 3), the value of the braking force gradual decrease speed F is γ. And the value of the braking force P is rapidly reduced. Thus, when the driver's intention to accelerate is clear, the braking force P is rapidly reduced, so that the host vehicle 100 can be quickly accelerated as shown in FIG.

  As described above, according to the vehicle braking control device 1, the host vehicle can be appropriately braked in accordance with the driver's vehicle operation.

  In the process of step S11, the ECU 20 may advance the process to step S12 when the state where the accelerator opening ω is equal to or larger than the opening threshold ωth continues for a predetermined time or longer. According to such a process, when the driver continues to depress the accelerator pedal (so-called solid stepping operation), the braking force P can be reduced early.

  Further, the control method of the braking force P by the ECU 20 according to the above embodiment is an example. For example, the ECU 20 calculates a target deceleration necessary for avoiding a collision, and the deceleration of the host vehicle is the target deceleration. The magnitude of the braking force P may be controlled so as to match. When performing such control, the ECU 20 does not change the magnitude of the braking force gradual deceleration F, but instead reduces the target deceleration per unit time (hereinafter referred to as deceleration) according to the driver's steering operation and accelerator operation. May be changed). More specifically, when the ECU 20 determines that there is a steering operation when releasing the automatic braking, the ECU 20 determines that there is an operation of setting the deceleration gradually decreasing speed to a relatively large value and depressing the accelerator. In this case, the deceleration gradual reduction speed may be set to a relatively small value. According to such processing, the gradual decrease rate of the braking force can be changed in accordance with the driver's steering operation and accelerator operation, substantially as in the above-described embodiment.

  Moreover, although the said embodiment demonstrated the example which single ECU performs the process shown in FIG. 2, several ECU may perform the process of each step shown in FIG. 2 separately. For example, the process for determining the collision risk of the host vehicle 100 and the process for performing automatic brake control may be performed by separate ECUs.

  The vehicle brake control device according to the present invention is useful as a vehicle brake control device that enables more appropriate vehicle brake control than before.

DESCRIPTION OF SYMBOLS 1 Vehicle brake control apparatus 11 Radar apparatus 12 Accelerator apparatus 13 Steering sensor 20 ECU
30 Brake actuator 100 Own vehicle 200 Preceding vehicle 300 Following vehicle

Claims (2)

A vehicle braking control device that automatically brakes a vehicle according to the risk of collision between the host vehicle and an obstacle,
Collision determination means for determining whether or not there is a high risk of collision between the host vehicle and the obstacle;
Automatic braking means for automatically generating braking force on the host vehicle when the collision determination unit determines that the risk of collision between the host vehicle and an obstacle is high;
Braking force gradually decreasing means for gradually decreasing the magnitude of the braking force generated by the automatic braking means according to the steering operation of the driver of the host vehicle,
The braking force gradual decrease means is configured to reduce the braking force when the driver depresses the accelerator pedal for a predetermined time after starting the gradual decrease of the braking force, compared to when the accelerator pedal is not depressed. A vehicular braking control apparatus characterized by increasing a gradual decrease rate of power . A vehicle braking control device that automatically brakes a vehicle according to the risk of collision between the host vehicle and an obstacle,
Collision determination means for determining whether or not there is a high risk of collision between the host vehicle and the obstacle;
Automatic braking means for automatically generating braking force on the host vehicle when the collision determination unit determines that the risk of collision between the host vehicle and an obstacle is high;
Braking force gradually decreasing means for gradually decreasing the magnitude of the braking force generated by the automatic braking means according to the steering operation of the driver of the host vehicle,
The braking force gradual decrease means is configured to cause the accelerator opening of the host vehicle to be equal to or greater than a predetermined opening threshold by the depression operation of the accelerator pedal by the driver after starting the gradual decrease of the braking force , and the accelerator opening When the amount of change per unit time is equal to or greater than a predetermined change amount threshold value , the vehicle gradually increases the braking force gradually as compared to the case where the accelerator pedal is not depressed. Braking control device.

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