JP2019209700A - Collision avoidance device - Google Patents

Abstract

To improve brake characteristic from a point of view different from viscometric property of brake oil in an automatic parking brake using regenerative brake force obtained by a motor for drive of a vehicle together with vehicle brake force of the hydraulic brake device.SOLUTION: A collision avoidance device executes automatic braking of an own vehicle by using the regenerative brake force obtained via regenerative control of a drive motor 51 driving drive wheels W of the own vehicle together with the vehicle brake force of hydraulic brake mechanisms 40, 42 if a determination parameter obtained by dividing a distance between a target and the own vehicle by a relative speed of the own vehicle to the object is a prescribed threshold or less when encountering collision avoidance against the target existing in the frontward direction of the own vehicle 30. The threshold is set to have a smaller value in the case where regenerative brake ability of the drive motor is higher than prescribed standard ability compared to the case where the regenerative brake ability is lower than the standard ability.SELECTED DRAWING: Figure 4

Description

  The present disclosure relates to a technique for avoiding a collision between a host vehicle and a target in front of the host vehicle.

  Patent Document 1 improves the braking characteristics when the regenerative braking force obtained by the motor for driving the vehicle is used together with the vehicle braking force exerted by the hydraulic brake device in consideration of the fact that the viscosity characteristic of the brake oil changes with temperature. A braking method is proposed.

Japanese Patent Laying-Open No. 2015-226364

  Vehicle braking using the regenerative braking force of the motor is not limited to the case where the brake pedal is operated, but is also used for avoiding a collision between the host vehicle and a target in front of the vehicle. And in vehicle braking at the time of collision avoidance, there remains room for improvement of braking characteristics from a viewpoint different from the viscosity characteristics of brake oil.

  According to one form of the present disclosure, a collision avoidance device is provided. The collision avoidance device is a collision avoidance device (10) for avoiding a collision with a target existing in front of the host vehicle (30), and includes the interval between the target and the host vehicle. A target state acquisition unit (21) for acquiring a target state and a risk parameter indicating the degree of collision risk with the target are obtained using at least the interval, and whether or not the risk parameter is equal to or greater than a predetermined threshold. A collision determination unit (22) for determining the vehicle, and when the collision determination unit determines that the risk parameter is equal to or greater than the threshold, the regeneration of the drive motor (51) that drives the drive wheels (W) of the host vehicle A collision avoidance control unit (23) for executing automatic braking of the host vehicle by using a regenerative braking force obtained through control in combination with a vehicle braking force exerted by the hydraulic brake mechanism (40, 42). The collision determination , When the regenerative braking capacity of the drive motor is higher than the pre-defined reference capacity is set to a large value the threshold as compared with the case lower than the reference capacity.

  According to the collision avoidance device of this aspect, in a situation where the regenerative braking ability of the drive motor is higher than the reference ability, the threshold value larger than the threshold in the situation where the regenerative braking ability is lower than the reference ability is used. The judgment time of the target collision after the comparison with is delayed. By the way, if the regenerative braking capability of the drive motor is higher than the reference capability, a large regenerative braking force can be quickly used together with the automatic braking of the host vehicle. Therefore, even if the judgment of the target collision is delayed, the target collision can be avoided by the automatic braking in which the large regenerative braking force is quickly used together with the vehicle braking force of the hydraulic brake mechanism. Further, if the determination of the target collision is delayed, the vehicle operator can determine the approach to the target by himself before the target collision is determined, and the target collision can be avoided by his own brake operation. . Therefore, according to the collision avoidance device of this embodiment, it is possible to reduce the operating frequency of automatic braking using the regenerative braking force in combination with the vehicle braking force of the hydraulic brake mechanism.

It is a block diagram of a collision avoidance system provided with the collision avoidance device of a 1st embodiment. It is a figure for demonstrating the vehicle provided with a collision avoidance apparatus. It is a processing flow of the collision avoidance process which a collision avoidance system performs. It is explanatory drawing which shows the mode of the action | operation of automatic braking in contrast with the level of battery charge.

A. First embodiment:
The collision avoidance system 10 of the first embodiment is mounted on the host vehicle 30 as a collision avoidance device, and includes a sensor unit 11 and an ECU 20 as shown in FIG. The sensor unit 11 and the ECU 20 are connected by an in-vehicle network.

  The sensor unit 11 includes a millimeter wave sensor 12, an image sensor 14, a vehicle speed sensor 16, and a yaw rate sensor 18. As shown in FIG. 2, the millimeter wave sensor 12 is attached to the front portion of the host vehicle 30. The millimeter wave sensor 12 is configured, for example, as a so-called “millimeter wave radar” of the FMCW method, and transmits and receives a frequency-modulated millimeter wave radar wave. The range in which the millimeter wave sensor 12 transmits a millimeter wave is a range in which a target (for example, another vehicle, a pedestrian, a bicycle, etc.) existing in front of the host vehicle 30 can be included. The front of the host vehicle 30 includes right front and left front in addition to the front.

  As shown in FIG. 2, the image sensor 14 is attached in the vicinity of the upper end of the front shield 31. The image sensor 14 is a camera having a known configuration, and can capture a landscape in front of the host vehicle 30. The imaging range of the image sensor 14 is a range in which a target existing in front of the host vehicle 30 can be included.

  The vehicle speed sensor 16 (FIG. 1) acquires data on the moving speed of the host vehicle 30. The yaw rate sensor 18 acquires rotational angular velocity data of the host vehicle 30. Various data acquired by the sensor unit 11 is transmitted to the ECU 20 and used to calculate the interval between the target and the host vehicle 30, the relative speed of the host vehicle 30 with respect to the target, and the like.

  The ECU 20 includes a storage unit 29 and a CPU (not shown). ECU20 performs the collision avoidance process mentioned later by running the control program memorize | stored in the memory | storage part 29. FIG. The storage unit 29 has a known configuration such as a ROM or a RAM. FIG. 1 functionally shows a control program executed by the ECU 20. The ECU 20 is connected to the brake ECU 40 and the drive motor ECU 50 included in the host vehicle 30 through an in-vehicle network, and transmits and receives control signals to and from each other. The storage unit 29 determines that a target collision can occur in addition to information related to the host vehicle 30 such as the length and width of the host vehicle 30 and various preset threshold values used by the collision avoidance control unit 23 described later. In this case, the braking force and deceleration at the time of performing automatic braking (AEB: Autonomous Emergency Braking) of the host vehicle 30 are stored.

  The brake ECU 40 controls the drive of the hydraulic brake 42 and applies a vehicle braking force to the drive wheels W. The brake ECU 40 constitutes a hydraulic brake mechanism in the present disclosure together with the hydraulic brake 42. The drive motor ECU 50 performs drive control and regenerative control of the drive motor 51 to drive the drive wheels W via the power transmission mechanism 52 connected to the drive motor 51 or to regenerate the drive motor 51 to the drive wheels W. Apply braking force. The drive motor ECU 50 is connected to a battery 53 that supplies power to the drive motor 51 and charges regenerative power from the drive motor 51, and detects the current charge amount SOC of the battery 53, or a collision avoidance control unit of the ECU 20. In response to the control signal from 23, the regeneration control of the drive motor 51 is executed to charge the battery 53.

  The brake ECU 40 and the drive motor ECU 50 can transmit and receive data without going through the ECU 20. Based on the driver's brake pedal operation, the brake ECU 40 and the drive motor ECU 50 can brake the host vehicle 30 with only the vehicle braking force by the hydraulic brake 42, and the drive motor 51. The host vehicle 30 is braked together with the regenerative braking force. In addition, the brake ECU 40 and the drive motor ECU 50 cooperate with the ECU 20 to execute automatic braking of the host vehicle 30 when it is determined that a target collision can occur. The automatic braking will be described later.

  The ECU 20 includes a target state acquisition unit 21, a collision determination unit 22, and a collision avoidance control unit 23. These functional units are constructed by the ECU 20 executing a predetermined program.

  The target state acquisition unit 21 detects a target in front of the host vehicle based on a reflected wave that is a radar wave acquired by the millimeter wave sensor 12 and an interval between the detected target and the host vehicle 30 (hereinafter, referred to as a target wave). This interval is referred to as a target interval for convenience of citation of terms) and a relative speed of the vehicle 30 with respect to the target is calculated. That is, the target state acquisition unit 21 acquires the state of the target including the target interval. When detecting a target, a target existing in front of the host vehicle 30 may be detected based on a captured image that is data acquired by the image sensor 14 or data of both the captured image and the reflected wave. .

  The collision determination unit 22 compares a determination parameter TTC obtained by dividing the target interval acquired by the target state acquisition unit 21 by the relative speed of the host vehicle 30 with respect to the target with a threshold value described later, and based on the comparison result, the host vehicle 30 It is determined whether or not a target collision that collides with the target can occur. The determination parameter TTC is an example of a risk parameter that represents the degree of collision risk with a target. The risk of collision with the target increases as the risk parameter increases and increases as the determination parameter TTC decreases. Therefore, in determining whether the risk of collision with a target has increased, determining whether the determination parameter TTC is equal to or less than a predetermined threshold is synonymous with determining whether the risk parameter is equal to or greater than a predetermined threshold. It becomes. In addition, since the risk of collision with the target increases as the target gap becomes smaller, it is determined whether the risk of collision with the target has increased. It is also possible to do this.

  When the collision determination unit 22 determines that the host vehicle 30 can collide with the target, the collision avoidance control unit 23 performs braking so that the host vehicle 30 is decelerated by the vehicle braking force stored in the storage unit 29. The automatic braking described later is executed in cooperation with the ECU 40 and the drive motor ECU 50.

  The ECU 20 of the collision avoidance system 10 of the first embodiment executes the collision avoidance process shown in FIG. 3 repeatedly at predetermined intervals in cooperation with the brake ECU 40 and the drive motor ECU 50. When executing the collision avoidance process, the target state acquisition unit 21 of the ECU 20 first detects a target located in front of the host vehicle 30 (step S100). When the target is not detected by the target state acquisition unit 21, the collision avoidance process in this routine ends, and the target detection in step S100 is executed again after a predetermined time.

  When the target is detected in step S100, the collision determination unit 22 determines whether or not the regenerative braking ability of the drive motor 51 is higher than a predetermined reference ability (step S110). The regenerative braking capability of the drive motor 51 is such that the battery 53 can be charged because the charge amount SOC of the battery 53 is small, or the power requirement from a vehicle auxiliary machine such as an air conditioner (not shown in FIG. 1) is large. It will be high. Therefore, the determination in step S110 is a comparison target of the regenerative braking ability with the current charge amount SOC of the battery 53 obtained via the drive motor ECU 50 and the measurement required power obtained by measuring the required power from the vehicle auxiliary machine. This can be done by comparing with a reference value corresponding to the reference ability. For example, when the current charge amount SOC of the battery 53 is used, whether or not the current charge amount SOC is smaller than the reference charge amount SOCk defined in advance corresponding to the reference ability to be compared with the regenerative braking ability. Can be determined. In addition, when using the measurement required power obtained by measuring the required power of the vehicle auxiliary machine, whether or not the above measurement required power is larger than the reference required power defined in advance corresponding to the reference capacity to be compared with the regenerative braking capacity. What is necessary is just to determine. In the following description of the collision avoidance process, the case where the current charge amount SOC of the battery 53 is used will be described as an example. For convenience of terminology, the current charge amount SOC of the battery 53 is changed to the current charge amount. The quantity is referred to as SOCn.

  The target state acquisition unit 21 acquires the current charge amount SOCn of the battery 53 via the drive motor ECU 50, and determines whether or not the current charge amount SOCn is smaller than the reference charge amount SOCk (step S110). The reference charge amount SOCk is defined in a range of 90 to 97% of the full charge amount SOCf of the battery 53. The regulation of the reference charge amount SOCk is based on the fact that it is difficult to sufficiently increase the regenerative braking force of the drive motor 51 when the current charge amount SOCn of the battery 53 is greater than or equal to the reference charge amount SOCk.

  If it is determined in step S110 that the current charge amount SOCn is greater than the reference charge amount SOCk, the collision determination unit 22 sets the TTC threshold value to the threshold value T1 (step S120). The TTC threshold is a comparison target threshold of the determination parameter TTC obtained by dividing the target interval by the relative speed of the host vehicle 30 with respect to the target. On the other hand, when it is determined in step S110 that the current charge amount SOCn is equal to or less than the reference charge amount SOCk, the collision determination unit 22 sets the TTC threshold value to the second threshold value T2 that is smaller than the first threshold value T1 (step S130). That is, if the current charge amount SOCn is equal to or less than the reference charge amount SOCk, the regenerative braking force of the drive motor 51 can be sufficiently increased, and the regenerative braking capability of the drive motor 51 is higher than the predetermined reference capability. The TTC threshold is set to a second threshold T2 smaller than the first threshold T1 instead of the first threshold T1 (step S130). On the other hand, if the current charge amount SOCn is larger than the reference charge amount SOCk, it is difficult to sufficiently increase the regenerative braking force of the drive motor 51, and the regenerative braking ability of the drive motor 51 is smaller than the reference ability. In order to achieve early implementation, the TTC threshold is set to a first threshold T1 that is larger than the second threshold T2 (step S120). In the present embodiment, the second threshold value T2 is set to a threshold value that is smaller than the first threshold value T1 by about 10 to 20%, but various reduction degrees of the second threshold value T2 with respect to the first threshold value T1 may be set.

  Following the setting of the TTC threshold value, the target state acquisition unit 21 sequentially performs acquisition of the target state (step S140) and calculation of the determination parameter TTC (step S150). In the calculation of the target state, the target state acquisition unit 21 calculates the target interval detected based on the reflected wave that is the radar wave acquired by the millimeter wave sensor 12, and calculates the relative speed of the host vehicle 30 with respect to the target. Perform the calculation. The determination parameter TTC is calculated by dividing the target interval by the relative speed of the host vehicle 30 with respect to the target.

  Following the calculation of the determination parameter TTC, the collision determination unit 22 compares the determination parameter TTC calculated in step S150 with either the first threshold T1 set in step S120 or the second threshold T2 set in step S130 ( Step S160). That is, in step S110, when it is determined that the current charge amount SOCn is greater than the reference charge amount SOCk, the collision determination unit 22 compares the determination parameter TTC with the first threshold value T1. On the other hand, when it is determined in step S110 that the current charge amount SOCn is equal to or less than the reference charge amount SOCk, the collision determination unit 22 compares the determination parameter TTC with a second threshold value T2 that is smaller than the first threshold value T1.

  In step S160, if the determination parameter TTC is larger than the first threshold value T1 or the second threshold value T2, it can be determined that the possibility that the host vehicle 30 will collide with a target in front of it is low. Therefore, in this case, the brake operation is not performed (step S170), the collision avoidance process in this routine is finished, and step S100 is executed again after a predetermined time. On the other hand, if the determination parameter TTC is equal to or smaller than the first threshold value T1 or the second threshold value T2 in step S160, it can be determined that the host vehicle 30 can collide with a target ahead. Therefore, in this case, the collision avoidance control unit 23 cooperates with the brake ECU 40 and the drive motor ECU 50 in order to avoid the collision of the host vehicle 30 with the target in front of the vehicle, and the vehicle braking force by the hydraulic brake 42. Then, automatic braking of the host vehicle 30 is executed using the regenerative braking force of the drive motor 51 (step S180).

  In response to the first threshold value T1 set in step S120 or the second threshold value T2 set in step S130, the ECU 20 determines the magnitude and deceleration of the braking force (collision avoidance braking force) necessary for avoiding a collision with the target. It is stored in the storage unit 29. Therefore, the collision avoidance control unit 23 can obtain the collision avoidance braking force corresponding to the first threshold value T1 or the second threshold value T2 by the vehicle braking force by the hydraulic brake 42 and the regenerative braking force through the regeneration control of the drive motor 51. Thus, a control signal is transmitted to brake ECU40 and drive motor ECU50. At this time, the collision avoidance control unit 23 obtains in advance the magnitude of the regenerative braking force of the drive motor 51 that can be generated from the drive motor ECU 50 in advance, and obtains from the hydraulic brake 42 the braking force that is insufficient with the obtained regenerative braking force. To be able to. If the obtained regenerative braking force is larger than the collision avoidance braking force, the vehicle braking force of the hydraulic brake 42 may be set to zero, and the collision avoidance braking force may be exhibited only by the regenerative braking force of the drive motor 51. By such automatic braking, the host vehicle 30 is decelerated and stopped in front of the target, and the collision avoidance process in this routine ends. Then, step S100 is executed again after a predetermined time. During automatic braking in step S180, a constant braking force of the collision avoidance braking force, for example, 20 to 30% of the collision avoidance braking force is exerted by the vehicle braking force by the hydraulic brake 42, and the collision occurs. The shortage of the avoidance braking force may be supplemented with the regenerative braking force obtained by the regenerative control of the drive motor 51.

  The state of automatic braking in step S180 is shown in FIG. 4 separately for the case where the current charge amount SOCn is larger than the reference charge amount SOCk and the case where the current charge amount SOCn is less than or equal to the reference charge amount SOCk. The thick line in FIG. 4 shows the actual current charge amount SOCn, determination parameter TTC, and deceleration acceleration, and the thin line shows the full charge amount SOCf, the reference charge amount SOCk, the first threshold value T1, the second threshold value T2, and the like. Yes.

  As shown in the upper part of FIG. 4, when the current charge amount SOCn is larger than the reference charge amount SOCk, the comparison target threshold value of the determination parameter TTC is the first threshold value T1 that is larger than the second threshold value T2. Therefore, since the elapsed time t1 until the determination parameter TTC becomes equal to or less than the first threshold value T1 is shortened, the determination timing that the collision with the target can occur is advanced, and the automatic braking of the host vehicle 30 is performed at the elapsed time t1. Is executed (step S180). The automatic braking at the elapsed time t1 is electric power in which the current charge amount SOCn is larger than the reference charge amount SOCk and approximates the full charge amount SOCf. Therefore, although the regenerative braking force of the drive motor 51 is less than the reference capability, the elapsed time The vehicle braking force of the hydraulic brake 42 complements the vehicle braking immediately from time t1. And since the regenerative braking force of the drive motor 51 is below reference | standard capability, the deceleration acceleration (deceleration G) of the own vehicle 30 based on braking force increases gradually.

  As shown in the lower part of FIG. 4, when the current charge amount SOCn is equal to or less than the reference charge amount SOCk, the comparison target threshold value of the determination parameter TTC is a second threshold value T2 that is smaller than the first threshold value T1. Therefore, the elapsed time t2 until the determination parameter TTC becomes equal to or less than the second threshold T2 is longer than the elapsed time t1 when the current charge amount SOCn is greater than the reference charge amount SOCk, and a collision with the target may occur. The determination timing is delayed. Then, automatic braking of the host vehicle 30 is executed at the delayed elapsed time t2 (step S180). In the automatic braking at the elapsed time t2, since the current charge amount SOCn is equal to or less than the reference charge amount SOCk, the regenerative braking force of the drive motor 51 is higher than the reference capability, so that the large regenerative braking force is quickly used together. Automatic braking. Therefore, even if the judgment of the target collision is delayed, the target collision can be avoided by the automatic braking in which the large regenerative braking force of the drive motor 51 is quickly used together with the vehicle braking force of the hydraulic brake 42 at the delayed elapsed time t2. Can be achieved. Since the regenerative braking force of the drive motor 51 is higher than the reference capability, the deceleration acceleration (deceleration G) of the host vehicle 30 based on the braking force is compared with the case where the regenerative braking force of the drive motor 51 is less than the reference capability. Thus, it quickly rises and the time required for collision avoidance is also short. In addition, since the determination of the target collision is delayed until the elapsed time t2, the vehicle operator of the host vehicle 30 himself / herself determines whether the target vehicle 30 is approaching the target and determines the hydraulic pressure by his own brake operation. The target collision can be avoided by the vehicle braking force of the brake 42. Therefore, according to the collision avoidance system 10 of the present embodiment, it is possible to reduce the operating frequency of automatic braking using the vehicle braking force of the hydraulic brake mechanism including the hydraulic brake 42 together with the regenerative braking force of the drive motor 51.

B. Other embodiments:
(1) In the above embodiment, the two threshold values of the first threshold value T1 and the second threshold value T2 are used as the TTC threshold value. However, the present invention is not limited to this. For example, the TTC threshold value may be set to three or more values so that the TTC threshold value becomes smaller than the first threshold value T1 as the reference charge amount SOCk is smaller than the reference charge amount SOCk.

  The present disclosure is not limited to the above-described embodiment, and can be realized with various configurations without departing from the spirit of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in each embodiment described in the summary section of the invention are intended to solve part or all of the above-described problems, or one of the above-described effects. In order to achieve part or all, replacement or combination can be appropriately performed. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

  DESCRIPTION OF SYMBOLS 10 ... Collision avoidance system, 20 ... ECU, 21 ... Target state acquisition part, 22 ... Collision determination part, 23 ... Collision avoidance control part, 30 ... Own vehicle, 40 ... Brake ECU, 42 ... Hydraulic brake, 50 ... Drive motor ECU, 51 ... drive motor, 53 ... battery, T1 ... first threshold, T2 ... second threshold, W ... drive wheel

Claims (3)

A collision avoidance device (10) for avoiding a collision with a target existing in front of the host vehicle (30),
A target state acquisition unit (21) for acquiring a state of the target including an interval between the target and the host vehicle;
A collision determination unit (22) for determining a risk parameter representing a degree of collision risk with the target using at least the interval, and determining whether the risk parameter is equal to or greater than a predetermined threshold;
When the risk determination unit determines that the risk parameter is equal to or greater than the threshold, the regenerative braking force obtained through the regenerative control of the drive motor (51) that drives the drive wheels (W) of the host vehicle is A collision avoidance control unit (23) for performing automatic braking of the host vehicle in combination with the vehicle braking force exerted by the hydraulic brake mechanism (40, 42);
The collision determination unit
When the regenerative braking capability of the drive motor is higher than a predetermined reference capability, the threshold value is set to a larger value than when the drive motor is lower than the reference capability.
Collision avoidance device. The collision avoidance device according to claim 1,
The target state acquisition unit acquires the relative speed of the host vehicle with respect to the target in addition to the interval,
The collision determination unit
After using the determination parameter obtained by dividing the interval by the relative speed as the risk parameter, instead of determining whether the risk parameter is equal to or greater than a predetermined threshold, whether the determination parameter is equal to or smaller than a predetermined threshold Determine whether
When the regenerative braking ability of the drive motor is higher than a predetermined reference ability, the threshold is set to a smaller value than when the drive motor is lower than the reference ability.
Collision avoidance device. The collision avoidance device according to claim 2,
The collision determination unit
When the charge amount of the battery that supplies power to the drive motor is smaller than a predetermined reference charge amount, the threshold value is set to a smaller value than when the charge amount is larger than the reference charge amount.
Collision avoidance device.

Images