JP5507433B2 - Driving assistance device - Google Patents

Description

  The present invention relates to a driving support device that stops a host vehicle in front of an obstacle that may collide with an automatic brake, and more particularly to control of a start timing of an automatic brake for stopping the host vehicle with high distance accuracy at a low cost.

  In general, in the field of automobiles (vehicles), it is important to reduce damage caused by collisions, but it is more important to avoid (prevent) collisions.

  The collision avoidance method includes a method of changing the course of the own vehicle by controlling the steering, and a method of automatically stopping the own vehicle in front of the obstacle by an automatic brake. This is effective when the object is stationary.

  As a driving assistance device that avoids a collision by automatic braking, conventionally, a distance to an obstacle is detected by a millimeter wave radar, and a predicted collision time is determined based on the detected distance and a relative speed between the host vehicle and the obstacle. There has been proposed a collision prevention support device that calculates TTC and starts automatic braking with the timing when the predicted collision time TTC is reduced to the time (braking limit time) when the host vehicle is stopped by automatic braking as the optimal timing ( For example, see Patent Document 1 (paragraphs [0050]-[0051], [0054], FIG. 1, FIG. 3, etc.).

JP 2009-208559 A

  By the way, when avoiding a collision by automatic braking, according to the technical guidelines for collision avoidance, it is necessary to automatically stop in a state where the distance from the obstacle is short (a state of 1 m or less for the time being).

  In the conventional apparatus, if it is attempted to avoid such a collision by securing such a short distance by automatic braking, it is necessary to employ position control feedback and control the stop position with high accuracy by this position control feedback. In this case, an expensive and high-performance brake unit (for example, a VSC (stability control) unit with a position control feedback function) capable of position control feedback is required, which increases the cost.

  An object of the present invention is to stop an own vehicle in front of an obstacle with high distance accuracy at low cost by an automatic brake that does not require position control feedback.

In order to achieve the above-described object, the driving support device of the present invention is a driving support device that stops the host vehicle at a predetermined distance from an obstacle that may collide in front of the host vehicle by automatic braking. A delay time setting means for setting a time obtained by an experiment as an effective delay time from the generation of an automatic brake start command until the actual braking force of the automatic brake is applied to the host vehicle, and the brake of the automatic brake Divide the difference between the initial deceleration at the start of force application and the effective deceleration corresponding to the target deceleration for which the deceleration of the host vehicle is set by a preset jerk based on the braking characteristics of the host vehicle. and the transient time calculating means, a deceleration stop time calculation means for calculating a deceleration stop time until the vehicle is stopped at a deceleration of the effective deceleration to calculate the transient time by the actual Time obtained by adding the advance time for setting the stop position of the host vehicle at the automatic brake of the braking time to a position a predetermined distance before the obstacle to the braking time including the delay time, the transition time, and the deceleration stop time. For the required time calculation means for calculating the required time for automatic braking and the timing at which the predicted time for collision between the host vehicle and the obstacle becomes the required time so that the host vehicle stops before a predetermined distance from the obstacle. And determining means for determining the automatic brake start command timing (claim 1).

  According to the first aspect of the present invention, the effective delay time from the timing of the start command of the automatic brake to the time when the braking force of the automatic brake is actually applied to the host vehicle is set by the delay time setting means. The transient time until the deceleration of the host vehicle reaches the effective deceleration that actually reaches the target deceleration by the automatic braking of the target deceleration is calculated by the transient time calculating means. Further, the deceleration stop time calculating means calculates the deceleration stop time until the host vehicle stops due to the deceleration of the effective deceleration.

  The braking time including the effective delay time, the transition time, and the deceleration stop time is the time from the start of automatic braking until the host vehicle stops at the effective deceleration, and the predicted collision time TTC is equal to this time. When the automatic brake start command is generated at the timing, the own vehicle stops at the position where the distance from the obstacle is 0 by the automatic brake based on the start command. Therefore, the required time calculation means calculates the time required for the automatic brake by adding the advance time for setting the stop position of the vehicle at the automatic brake of the brake time to a position a predetermined distance before the obstacle. The time is calculated, and the timing at which the predicted collision time TTC becomes the required time is determined as the automatic brake start command timing by the determining means, and the automatic brake is started from this start command timing.

  Therefore, in the case of the present invention, it is possible to reduce the cost without performing the stop position control with the expensive position control feedback than the automatic brake from the determined start command timing, and based on the preceding time from the obstacle. It is possible to automatically stop the own vehicle with high accuracy at a position in front of the obstacle by a predetermined distance (for example, a position where the distance from the obstacle is 1 m or less), thereby avoiding a collision with the obstacle.

It is a block diagram of one embodiment of a driving support device of the present invention. It is explanatory drawing of the time change of the deceleration of the automatic brake of the driving assistance device of FIG. It is explanatory drawing of the time change of the speed (vehicle speed) of the own vehicle of FIG. It is a flowchart for operation | movement description of FIG.

  An embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a block diagram of a driving support apparatus of the present invention provided in a host vehicle 1 that stops by an automatic brake, and this driving support apparatus has obstacles around the vehicle 1 (mainly stationary obstacles). For example, in the present embodiment, a radar 2 such as a laser radar or a millimeter wave radar is provided in front of the host vehicle 1 in order to detect other parked vehicles, pillars, walls, and the like in a parking lot.

  The radar 2 measures the distance from the own vehicle 1 to the obstacle by transmitting and receiving pulse waves, and uses distance measurement data (distance data) and information on the relative speed of the obstacle over time, such as CAN. Is sent to the arithmetic processing unit 4 formed by a pre-crash system ECU (PSC ECU) having a microcomputer configuration.

  The arithmetic processing unit 4 also includes vehicle speed detected by a wheel speed sensor (not shown), acceleration / deceleration information obtained by differentiating the vehicle speed, and setting information for target deceleration (required deceleration) of the automatic brake. It is sent from the device or the like via the in-vehicle network 3.

  The arithmetic processing unit 4 executes the set automatic brake control program to execute the delay time setting means, transient time calculation means, deceleration stop time calculation means, required time calculation means, determination means, and collision prediction time TTC of the present invention. Based on the received information, the automatic brake start timing is searched and determined from a state in which the distance from the obstacle of the host vehicle 1 is sufficiently longer than the predicted collision time TTC. At this time, in the present embodiment, necessary calculations and the like are repeated at a calculation period (for example, every 50 ms) of the collision prediction time TTC until the traveling of the host vehicle 1 stops. The automatic braking is started after the vehicle speed becomes slower than a predetermined speed (for example, about 20 km / h to 30 km / h). This is because the collision prediction time TTC becomes too long at a higher vehicle speed.

In the calculation for each calculation period of the collision prediction time TTC, the latest speed (vehicle speed or relative speed) of the host vehicle 1 input from the in-vehicle network 3 at the start of the calculation or immediately before the calculation is the initial speed V0 [m / s. ] The latest deceleration is set to the initial deceleration A0 [m / s ² ], and roughly, the braking avoidance limit time for the own vehicle 1 to stop immediately before the obstacle by the automatic braking and the margin of the stop position are provided. For this purpose, the advance time is calculated by a simple calculation using a data map, and the start timing of the automatic brake is determined from the required time of the automatic brake obtained by adding the advance time to the braking avoidance limit time. Note that A0 <0 (denotes deceleration).

2 and 3 show the deceleration [m / s ² ] of the automatic brake of the host vehicle 1 calculated every calculation cycle of the predicted collision time TTC, the speed of the host vehicle 1 (vehicle speed or relative speed with respect to an obstacle) [ m / s] is shown by a solid line, and the processing of each means of the arithmetic processing unit 4 will be described below with reference to these time change examples. In FIG. 2, the vertical axis is the acceleration [m / s ² ] axis, and the negative direction is the deceleration.

  The means for calculating the predicted collision time TTC repeatedly calculates the predicted collision time TTC [s] at which the host vehicle 1 reaches the position of the obstacle at the current relative speed from the distance between the host vehicle 1 and the obstacle and the current relative speed. To do.

  The delay time setting means sets an effective delay time from the start of automatic braking until the braking force of the hydraulic brake or electric brake is actually applied to the host vehicle 1.

  If the effective delay time is T0 [s] in FIGS. 2 and 3, this time T0 is, for example, a control delay time until the brake hydraulic pressure increases and the hydraulic brake or the electric brake actually starts. Obtained in advance and stored in a memory or the like. At that time, in order to set the effective delay time T0 to a predetermined time regardless of the vehicle speed or the like, particularly in the case of a hydraulic brake, the brake hydraulic pressure is always maintained at a level just before the brake is actually applied by precharge control. It is desirable. When the precharge control is not performed, for example, the effective delay time T0 is set for each vehicle speed range of the host vehicle 1 and held as map data, and the effective delay time T0 corresponding to the vehicle speed is calculated at the start of calculation of the predicted collision time TTC. What is necessary is just to read and set from a map.

  Then, the delay time setting means sets the effective delay time T0 read from the map or the like for each calculation period of the collision prediction time TTC. 2 and 3, there is no deceleration change due to automatic braking in the own vehicle 1 during the effective delay time T0 at times t0 to t1, and the deceleration of the own vehicle 1 is maintained at the initial deceleration A0. The initial deceleration A0 is, for example, deceleration due to engine braking caused by the driver removing his / her foot from the accelerator pedal. The speed (vehicle speed) of the host vehicle 1 decreases as shown in FIG. 3 due to the deceleration of the initial deceleration A0. If the speed when the effective delay time T0 has elapsed is V1 [m / s], the speed V1 is When the effective delay time T0 has elapsed, the vehicle speed of the host vehicle 1 decreases to a vehicle speed (V0 + V1) [m / s] that is lower than the initial speed V0 by | V1 |. Note that V1 <0 (denotes deceleration).

The transient time calculation means is an effective deceleration (effective maximum deceleration Amax [in this embodiment) in which the deceleration of the host vehicle 1 actually reaches by automatic braking of the set target deceleration (maximum deceleration in this embodiment). m / s ² ] in the data map, and based on the setting of the target deceleration of automatic braking, from the initial deceleration A0, a jerk (deceleration [m / s ^2] of the time differential value [m ^{/ s} 3]) Figure 2 for decelerating the effective maximum deceleration Amax at a slope of, for calculating the transient time T1 [s] time t1~t2 in FIG. the transition time T1 Is obtained from a simple calculation of T1 = (Amax−A0) / J, where the jerk is J [m / s ³ ], and the vehicle speed V2 [m / s], which is a decrease in the vehicle speed during the transition time T1. Is expressed by the following equation (2) That. It should be noted, is a Amax <0, J <0, V2 <0.

  The deceleration stop time calculating means calculates a deceleration stop time until the host vehicle 1 stops due to the deceleration of the target deceleration. Assuming that the deceleration stop time is T2 [s], in this embodiment, the deceleration stop time T2 is the effective maximum deceleration Amax, and the host vehicle 1 changes from the vehicle speed V0 + V1 + V2 [m / s] to the vehicle speed 0 [m / s]. T2 = (V0 + V1 + V2) / Amax.

  The required time calculation means sets the stop position of the host vehicle 1 with the automatic brake of the braking time Tbrk to a predetermined distance before the obstacle during the braking time Tbrk [s] including the delay time T0, the transition time T1 and the deceleration stop time T2. A time obtained by adding an advance time Td [s] to be described later is calculated as a required time Treq [s] for automatic braking.

  That is, when the automatic braking of the host vehicle 1 is started at time t1 in the state of the initial deceleration A0 and the initial speed V0, the vehicle speed of the host vehicle 1 is 0 [m / s], as is apparent from FIGS. Thus, the braking time Tbrk from time t1 to time t3 is required until the host vehicle 1 stops. The braking time Tbrk is expressed by the following equation (3).

  The braking time Tbrk is a braking avoidance limit time. When automatic braking is started at the timing t2 when the predicted collision time TTC becomes the braking time Tbrk, the stop position of the host vehicle 1 has a distance (interval) of 0 [ m] and there is no margin for collision avoidance.

  Therefore, in order to set the stop position of the vehicle 1 by the automatic brake to an appropriate predetermined distance D [m], for example, a distance of 0.5 m from the obstacle, the start timing of the automatic brake is set to the collision prediction time. The vehicle is moved forward from time t2 when the TTC reaches the braking time Tbrk, and the host vehicle 1 is stopped before the obstacle D [m] by automatic braking.

  If the advance time for stopping at the front D [m] is Td, the advance time Td is the time at which the host vehicle 1 travels the distance D at the initial acceleration A0 and the initial vehicle speed V0 before starting the automatic braking. Correspondingly, the distance D is expressed by the following equation (4).

Here, (4) of the second term of the "A0 · Td ^2/2", since little effect on small calculation result, the second term regarded as 0 [m], the number of distance D following 5 You may approximate by (5) Formula.

  Therefore, the required time calculating means calculates the advance time Td from the equation (4) or (5), specifically, for example, as Td = D / V0 from the equation (5). Further, a time obtained by adding the advance time Td to the braking time Tbrk is calculated as a required time (required time) Treq [s] for automatic braking. The required time Treq is expressed by the following equation (6).

  Note that the delay time based on the communication delay of control information necessary for the calculation of the equation (6), the phase delay due to the filter, and the like is set as Tcomd [s], and the required time Treq of the automatic brake is expressed by the following equation (7) ). Although the delay time Tcomd may be a fixed time, it may be changed depending on the vehicle speed (relative speed). Therefore, the delay time Tcomd is stored as map data of the vehicle speed, and may be read and set from the map data according to the vehicle speed. Good.

  The determination means determines the timing at which the predicted collision time TTC between the host vehicle 1 and the obstacle repeatedly calculated by the calculation means for the predicted collision time TTC becomes the required time Treq as the start command timing of the automatic brake, and this start command timing In addition, the arithmetic processing unit 4 instructs the brake control unit 5 of FIG. 1 formed by the stability control (VSC) ECU of the microcomputer configuration via the in-vehicle network 3 to start automatic braking.

  FIG. 4 shows an example of processing procedures such as the above-described calculations for each calculation period of the predicted collision time TTC by the calculation processing unit 4, and the effective delay time T0 set by the delay time setting means and the transient time calculated by the transient time calculation means. Based on T1, the deceleration stop time T2 calculated by the deceleration stop time calculation means, the required time calculation means first calculates a braking time Tbrk which is a braking avoidance limit time (step S1). Next, the required time calculation means calculates the advance time Td from the equation (4) or (5) (step S2), and also calculates the delay time Tcomd as necessary (based on the setting specification or the like) ( Step S3).

  Then, the required time calculating means calculates the required time Treq for automatic braking by adding the advance time Td or the advance time Td and the delay time Tcomd to the braking time Tbrk (step S4).

  Next, the determination means determines whether or not the predicted collision time TTC is TTC ≦ Treq with respect to the required time Treq (step S5), and the distance from the vehicle 1 to the obstacle is long, and the possibility of collision is determined. TTC> Treq while NO is low, the process is terminated by passing through step S5 with NO, and when the host vehicle 1 approaches the obstacle and TTC ≦ Treq, the predicted collision time TTC becomes the required time Treq. The timing is detected (YES in step S5), and an automatic brake start command is output to the brake control unit 5 (step S6).

  Then, the brake control unit 5 which is instructed to start the automatic brake for avoiding the collision by the start command of the automatic brake starts the control of the automatic brake, and by the control of the automatic brake, By applying a hydraulic brake or an electric brake having a predetermined deceleration (effective maximum deceleration Amax) by the control, the host vehicle 1 is positioned at a position before a predetermined distance D (for example, 0.5 m) of the obstacle by the braking time Tbrk. Stop.

  Therefore, in the case of the present embodiment, the host vehicle 1 does not perform stop position control with expensive position control feedback, and is configured to achieve a cost reduction before the predetermined distance D (for example, 0.5 m) of the obstacle. It is possible to automatically stop at a precise position and avoid collision with obstacles.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit thereof. For example, the predetermined distance D may be set appropriately. It may be a distance exceeding 1 m.

  Based on the effective delay time T0 set by the delay time setting means, the transient time T1 calculated by the transient time calculation means, and the deceleration stop time T2 calculated by the deceleration stop time calculation means, the braking time Tbrk calculated by the required time calculation means is For example, a map is prepared by developing a map of each time T0, T1, T2 on a three-dimensional map with deceleration (acceleration), speed (vehicle speed) as x and y axes, and braking time Tbrk as z axis. It may be calculated from the above. Similarly, the advance time Td may be calculated from a three-dimensional map having, for example, deceleration (acceleration), speed (vehicle speed) as the x and y axes, and advance time Td as the z axis.

  The arithmetic processing unit 4 may be incorporated in the radar 4, for example, and the processing procedure of the arithmetic processing unit 4 may be any.

  Furthermore, the present invention can be similarly applied to a case where the radar 2 searches for the surroundings such as behind the host vehicle 1 and stops by automatic braking.

  The present invention can be applied to driving assistance for various vehicles that are stopped by an automatic brake.

DESCRIPTION OF SYMBOLS 1 Own vehicle 2 Radar 4 Arithmetic processing part 5 Brake control part

Claims (1)

A driving support device that stops the vehicle immediately before a predetermined distance from an obstacle with a possibility of collision in front of the vehicle by automatic braking,
A delay time setting means for setting a time obtained by an experiment as an effective delay time from the generation of an automatic brake start command until the braking force of the automatic brake is actually applied to the host vehicle;
The difference between the initial deceleration at the start of applying the braking force of the automatic brake and the effective deceleration corresponding to the target deceleration for which the deceleration of the host vehicle is set is preset based on the braking characteristics of the host vehicle. A transient time calculating means for calculating a transient time by dividing by a jerk ,
A deceleration stop time calculating means for calculating a deceleration stop time until the host vehicle stops due to the deceleration of the effective deceleration;
Add to the braking time including the effective delay time, the transition time, and the deceleration stop time, at least the advance time for setting the stop position of the vehicle at the automatic brake of the brake time to a position before a predetermined distance of the obstacle. Required time calculating means for calculating the time required as the time required for automatic braking;
Determining means for determining the timing at which the predicted time of collision between the host vehicle and the obstacle becomes the required time as a start command timing of an automatic brake for the host vehicle to stop before a predetermined distance from the obstacle; A driving support device characterized by that.

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