JP2011121491A - Driving support device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving support device improving determining accuracy in a collision determination. <P>SOLUTION: The driving support device determines the possibility of a collision between one's own vehicle and the other vehicle. The device includes a first calculator for calculating a collision predicting time TTC by using a relative distance Dr and a relative speed Vr between the one's own vehicle and the other vehicle; a second calculator for calculating a second collision predicting time TTC<SB>2nd</SB>by using the relative distance Dr, the relative speed Vr and relative acceleration Ar between the one's own vehicle and the other vehicle; and a collision determinator for determining the possibility of the collision between the one's own vehicle and the other vehicle by using at least one of the collision predicting time TTC and the second collision predicting time TTC<SB>2nd</SB>only when the second collision predicting time TTC<SB>2nd</SB>is the actual number. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a driving support device.

  Various devices have been developed to assist a vehicle driver, for example, a collision prevention device. In order to prevent a collision, the collision prevention device detects a preceding vehicle and provides support such as automatic braking and warning when it is determined that there is a high possibility of a collision due to the relationship between the host vehicle and the preceding vehicle. . In the support device described in Patent Literature 1, at least one of the time until the host vehicle and the obstacle contact, the relative distance between the host vehicle and the obstacle, the relative speed, and the relative acceleration is compared with a threshold value. Determine whether to provide support.

JP 2006-256494 A

  Depending on the relative acceleration between the host vehicle and the preceding vehicle, the possibility of a collision may be zero. However, if the determination is made based only on the time until the host vehicle comes in contact with the obstacle, the relative distance, or the relative speed, there is a risk of erroneous determination that there is a possibility of a collision, even though there is no possibility of a collision. is there.

  Then, this invention makes it a subject to provide the driving assistance device which improves the determination precision in collision determination.

Driving support apparatus according to the present invention is a driving support apparatus determines the possibility of collision between the own vehicle and another vehicle by using the relative distance D _r and the relative velocity V _r between the host vehicle and another vehicle, a first calculating means for calculating equation estimated collision time TTC by (1) below, using the relative distance D _r, the relative velocity V _r and the relative acceleration a _r between the host vehicle and another vehicle, the following equation (2 ) a second calculating means for calculating a second estimated collision time lengths _{TTC 2nd} Accordingly, the second time-to-collision _{TTC 2nd} only if real, using at least one of the estimated collision time lengths TTC and the second time-to-collision _{TTC 2nd} A collision determination means for determining the possibility of a collision between the host vehicle and another vehicle is provided.

In this driving support device, the first calculation means calculates the predicted collision time TTC by the equation (1) using the relative distance _Dr and the relative speed V _r between the host vehicle and the other vehicle, and the second calculation means vehicle and the relative distance to other vehicles _{D r,} second collision prediction time by equation (2) using the relative velocity _{V r} and the relative acceleration _{a r} calculates a _{TTC 2nd.} In this equation (2), when V _r ² −2A _r D _r inside the square root sign √ is a negative value, the second collision prediction time TTC _2nd is an imaginary number, and there is no value as the second collision prediction time TTC _2nd . This suggests that the host vehicle and other vehicles will never collide. Therefore, in the driving assistance device, there is no possibility of a collision when the second collision prediction time TTC _2nd is an imaginary number. Therefore, the collision determination unit only detects the collision prediction time TTC and the second collision prediction time TTC _2nd when the second collision prediction time TTC _2nd is a real number. The possibility of a collision between the host vehicle and another vehicle is determined using at least one of the second predicted collision times TTC _2nd . As described above, in the driving assistance device, when the second collision prediction time TTC _2nd is an imaginary number, the collision determination is not performed, so that the collision is possible when there is absolutely no possibility of the collision in consideration of the relative acceleration. It is possible to prevent an erroneous determination that there is a property, and to improve the determination accuracy. Further, since the collision determination is not performed when the second collision prediction time TTC _2nd is an imaginary number, the processing load can be reduced.

In the above-described driving support device of the present invention, it is preferable that the driving support for preventing the collision is performed only when the collision determination unit determines that there is a possibility of a collision when the second predicted collision time TTC _2nd is a real number. is there.

In this driving support device, since driving support for preventing a collision is performed only when it is determined that there is a possibility of a collision when the second collision prediction time TTC _2nd is a real number, there is absolutely no possibility of a collision. In such a case (when the second collision prediction time TTC _2nd is an imaginary number), it is possible to prevent unnecessary driving assistance and to prevent the driver from feeling uncomfortable due to unnecessary driving assistance.

In the driving assistance device of the present invention, the collision determination means uses the constant α to obtain at least one of the predicted collision time TTC and the second predicted collision time TTC _2nd only when the following conditional expression (3) is not satisfied. It is preferable to determine the possibility of collision between the host vehicle and another vehicle.

When _{V ^r} 2 _-2A ^r _D ^r of the inner square No. √ in formula (2) as described above is a negative value is second collision prediction time _{TTC 2nd} is imaginary, further, the constant α is provided as hysteresis , relative acceleration _{a r} is the larger than _V ^r 2 / _2D ^r _-α and is not performed collision determination. Therefore, in the driving assistance device, the collision determination unit does not determine the possibility of a collision when the conditional expression (3) is satisfied, and does not determine the collision predicted time TTC and the second collision when the conditional expression (3) is not satisfied. The possibility of collision is determined using at least one of the predicted times TTC _2nd . As described above, in the driving assistance device, it is possible to prevent hunting in the imaginary number determination by providing hysteresis and determining whether the second collision predicted time TTC _2nd is an imaginary number.

According to the present invention, when the second collision prediction time TTC _2nd is an imaginary number, the determination accuracy in the collision determination can be improved by not performing the collision determination.

It is a block diagram of the collision prevention apparatus which concerns on this Embodiment. Are explanatory views of a possible method of determining a collision in ECU of Fig. 1, (a) is an example of time change of the TTC, (b) the time change of _{A r} and _V ^r 2 / _2D ^r _-α It is an example. It is a flowchart which shows the flow of the process in ECU of FIG.

  Embodiments of a driving assistance apparatus according to the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected about the element which is the same or it corresponds in each figure, and the overlapping description is abbreviate | omitted.

  In the present embodiment, the driving support device according to the present invention is applied to a collision prevention device mounted on a vehicle. The collision prevention apparatus according to the present embodiment determines the possibility of collision between the host vehicle and the preceding vehicle, and performs intervention support control (automatic braking, warning) when there is a possibility of collision.

  With reference to FIG.1 and FIG.2, the collision prevention apparatus 1 which concerns on this Embodiment is demonstrated. FIG. 1 is a configuration diagram of a collision prevention apparatus according to the present embodiment. FIG. 2 is an explanatory diagram of a method of determining the possibility of collision in the ECU of FIG.

The collision prevention apparatus 1 is capable of collision using a predicted collision time TTC [Time To Collision] that considers the relative distance and relative speed between the host vehicle and the preceding vehicle and a second predicted collision time TTC _2nd that also considers relative acceleration. Determine sex. In particular, the collision prevention apparatus 1 determines that there is no possibility of a collision even in a situation where there is a possibility of a collision when the TTC is small and there is a possibility of a collision when the TTC _2nd is an imaginary number (hence, intervention support control). Suppression of the operation). The collision prevention apparatus 1 includes a millimeter wave radar 10, a brake actuator 20, an alarm device 21, and an ECU [Electronic Control Unit] 30.

  The millimeter wave radar 10 is a radar for detecting a preceding vehicle using millimeter waves. The millimeter wave radar 10 is attached to the front center of the host vehicle. The millimeter wave radar 10 transmits the millimeter wave forward from the own vehicle while scanning the millimeter wave in the left-right direction, and receives the reflected millimeter wave. Then, the millimeter wave radar 10 transmits the millimeter wave transmission / reception information (transmission angle, transmission time, reception angle, reception time, reception intensity, etc. centered on the traveling direction of the host vehicle) as a radar signal to the ECU 30.

  The brake actuator 20 is an actuator that adjusts the brake hydraulic pressure of the wheel cylinder of each wheel. When the brake actuator 20 receives the brake control signal from the ECU 30, the brake actuator 20 operates according to the target brake hydraulic pressure indicated by the brake control signal, and adjusts the brake hydraulic pressure of the wheel cylinder.

  The alarm device 21 is a device that outputs an alarm sound for notifying the driver that there is a possibility of a collision. When receiving a warning signal from the ECU 30, the warning device 21 outputs a warning sound according to the warning signal.

  The ECU 30 includes a CPU [Central Processing Unit], various memories, and the like, and performs overall control of the collision prevention apparatus 1. The ECU 30 receives a radar signal from the millimeter wave radar 10 at regular time intervals. Then, the ECU 30 uses the radar signal to perform preceding vehicle recognition processing, collision determination processing, and intervention support control, transmits a brake control signal to the brake actuator 20 as necessary, and transmits an alarm signal to the alarm device 21. To do. In the present embodiment, the collision determination process in the ECU 30 corresponds to the first calculation means, the second calculation means, and the collision determination means described in the claims.

The preceding vehicle recognition process will be described. The ECU 30 determines the presence / absence of a preceding vehicle ahead of the host vehicle based on millimeter wave transmission / reception information (particularly, information on a reflection point with reception information) at regular intervals. When there is a preceding vehicle, the ECU 30 calculates the relative distance _Dr between the host vehicle and the preceding vehicle based on the speed of the millimeter wave and the time from transmission to reception of the millimeter wave. Further, the ECU 30 calculates the relative speed V _r between the host vehicle and the preceding vehicle by using the frequency change (Doppler effect) of the reflected millimeter wave. Further, the ECU 30, by differentiating the relative velocity time, calculates a relative acceleration A _r between the preceding vehicle and the subject vehicle. Note that the relative velocity V _r and the relative acceleration A _r, if the host vehicle and the preceding vehicle is approaching a negative value, if away a positive value.

The collision determination process will be described. When the preceding recognizes the preceding vehicle by the vehicle recognition processing, the ECU 30, at regular time intervals, using the relative distance D _r and the relative velocity V _r between the subject vehicle and the preceding vehicle, calculates a TTC by formula (1) To do. TTC is the time required for the host vehicle and the preceding vehicle to collide when the current relative speed _Vr continues. Further, the ECU 30, at regular time intervals, using the relative distance _{D r} and the relative velocity _{V r} and the relative acceleration _{A r} between the subject vehicle and the preceding vehicle, calculates a _{TTC 2nd} by equation (2). TTC _2nd is the time required for the host vehicle and the preceding vehicle to collide when the current relative acceleration _Ar continues.

TTC _2nd is, _{V ^r} 2 _-2A ^r _D ^r of the square root No. √ internal in the formula (2) is imaginary in the case of a negative value. Since the imaginary TTC _2nd is absolutely impossible, it is implied that the collision will never occur in consideration of the relative acceleration _Ar (for example, a situation where the host vehicle and the preceding vehicle are separated from each other). Thus, when TTC _2nd is an imaginary number, it is determined that there is no possibility of collision even in a situation where it is determined that TTC is small and there is a possibility of collision. Since TTC _2nd has a positive value and a negative value even in the case of a real number, the positive value is valid and the negative value is ignored.

In ECU 30, using the relative distance _{D r} and the relative velocity _{V r} and the relative acceleration _{A r,} it determines whether the condition (3) is satisfied. When the conditional expression (3) is satisfied, TTC _2nd is an imaginary number, so the ECU 30 determines that there is no possibility of a collision. On the other hand, when the conditional expression (3) is not satisfied, the ECU 30 determines whether or not TTC is smaller than the TTC control threshold value. When TTC is smaller than the TTC control threshold, the ECU 30 determines that there is a possibility of collision between the host vehicle and the preceding vehicle. On the other hand, when TTC is equal to or greater than the TTC control threshold, the ECU 30 determines that there is no possibility of collision between the host vehicle and the preceding vehicle. The TTC control threshold value is a threshold value for determining the possibility of a collision using the TTC, and is a value set in advance by an actual vehicle experiment or simulation.

Condition (3) above with consideration of the suitability constant alpha, a condition _{that V ^r} 2 _-2A ^r _D ^r of the inner square No. √ becomes a negative value. The reason for adding such adaptation constant alpha, a hysteresis is provided in the imaginary determination of the TTC _2nd, values D _r, V _r, the small changes in A _r are imaginary / real in this imaginary determination extremely short period This is to prevent repeated determination (anti-hunting). Thereby, it is possible to prevent the intervention support control from repeatedly operating / inactivating in a very short time. The adaptation constant α is a hysteresis in the imaginary number determination, and is a value set in advance by an implementation experiment or simulation.

Figure 2 is the (a) shows an example of time change C1 in TTC, 2 time variation of _{A r} in the conditional expression (3) to (b) corresponding to FIG. 2 (a) C2 and _V ^{r 2} An example of the time change C3 of / 2D _r -α is shown. When the collision determination is performed using only the TTC as in the past, it is determined that there is a possibility of a collision after the time T1 when the TTC decreases with time and the TTC becomes smaller than the TTC control threshold. However, in the section S2, _{A r} has become larger than _V ^r 2 / _2D ^r _-α, it satisfied the condition (3) is the situation where unlikely collision and consider _{A r.} Therefore, in section S1 from time T1 to time T2 when section S2 ends, it is determined that there is no possibility of collision although TTC is smaller than the TTC control threshold, and intervention support control is suppressed. Then, after time T2 when the section S2 ends, it is determined that there is a possibility of collision, and the intervention support control is activated.

In addition, since it is possible to determine whether TTC _2nd is an imaginary number or a real number by the determination based on the conditional expression (3), it is not necessary to actually calculate the value of TTC _2nd .

The intervention support process will be described. When it is determined that there is a possibility of collision in the collision determination process, the ECU 30 sets a target deceleration for avoiding the collision based on the relative distance _Dr , the relative speed _Vr, and the relative acceleration _Ar. . Then, the ECU 30 sets a target brake hydraulic pressure of each wheel cylinder necessary for achieving the target deceleration, and transmits the target brake hydraulic pressure to the brake actuator 20 as a brake control signal. Further, the ECU 30 transmits an alarm signal for outputting an alarm sound to the alarm device 21.

  With reference to FIG.1 and FIG.2, the operation | movement in the collision prevention apparatus 1 is demonstrated. In particular, the processing in the ECU 30 will be described along the flowchart of FIG. FIG. 3 is a flowchart showing the flow of processing in the ECU of FIG.

  The millimeter wave radar 10 transmits the millimeter wave that is reflected while scanning the millimeter wave in front of the host vehicle and receives the reflected millimeter wave, and transmits the millimeter wave transmission / reception information to the ECU 30 as a radar signal. . The ECU 30 receives the radar signal, and acquires millimeter wave transmission / reception information.

At certain time intervals, the ECU 30 determines whether there is a preceding vehicle ahead of the host vehicle, based on the millimeter wave transmission / reception information (S1). When the preceding vehicle is determined to exist, the ECU 30, based on the reception information of the millimeter-wave for that preceding vehicle, and calculates the relative distance _{D r,} the relative velocity _{V r,} the relative acceleration _{A r} (S1). When there is no preceding vehicle, the ECU 30 performs the preceding vehicle recognition process after a certain time without performing the subsequent processes.

Then, the ECU 30, using the relative distance _{D r} and the relative velocity _{V r,} calculates the TTC by formula (1) (S2). Further, the ECU 30, using the relative distance _{D r,} the relative velocity _{V r} and the relative acceleration _{A r,} calculates a _{TTC 2nd} by formula (2) (S3).

Then, the ECU 30, using the relative distance _{D r,} the relative velocity _{V r} and the relative acceleration _{A r,} determines whether the condition (3) is satisfied (S4). If it is determined in S4 that the conditional expression (3) is satisfied, the ECU 30 determines that there is no possibility of a collision with the preceding vehicle.

  When it is determined that the conditional expression (3) is not satisfied in S4, the ECU 30 determines whether or not TTC is smaller than the TTC control threshold (S5). If it is determined in S5 that TTC is equal to or greater than the TTC control threshold, ECU 30 determines that there is no possibility of a collision with the preceding vehicle. If it is determined in S5 that TTC is smaller than the TTC control threshold, the ECU 30 determines that there is a possibility of a collision with the preceding vehicle. The ECU 30 sets a target deceleration for avoiding a collision, transmits a target brake hydraulic pressure necessary for achieving the target deceleration to the brake actuator 20 as a brake control signal, and outputs an alarm sound. Is sent to the alarm device 21 (S6). When this brake control signal is received, the brake actuator 20 operates based on the brake control signal and pressurizes the brake hydraulic pressure of the wheel cylinder. As a result, an automatic brake is actuated on the host vehicle and decelerates. When the alarm signal is received, the alarm device 21 outputs an alarm sound based on the alarm signal.

According to the collision preventing apparatus 1, when the TTC _2nd is an imaginary number, it is determined that there is no possibility of a collision even in a situation where it is determined that there is a possibility of a collision by the TTC. It is possible to prevent erroneous determination as being present and improve determination accuracy. As a result, unnecessary automatic braking and alarm output can be prevented, and the driver does not feel discomfort due to unnecessary automatic braking and alarm output. Moreover, in the collision prevention apparatus 1, when TTC _2nd is an imaginary number, the collision determination by TTC is not performed, so that the processing load can be reduced.

Moreover, in the collision prevention apparatus 1, since the collision determination is performed by combining TTC that does not consider relative acceleration and TTC _2nd that considers relative acceleration, the determination accuracy can be improved. Incidentally, when the collision determination is performed only by the TTC, the relative acceleration is not taken into consideration in the determination, and thus it is not possible to determine a situation where the TTC _2nd is an imaginary number. On the other hand, when the collision determination is performed using only TTC _2nd , the relative acceleration cannot be directly detected. Therefore, it is necessary to perform processing such as time differentiation.

Furthermore, in the collision prevention apparatus 1, since the imaginary number determination of TTD _2nd is performed in consideration of the adaptation constant α, hunting can be prevented and unnecessary automatic braking and warning can be prevented. As a result, the driver does not feel uncomfortable due to unnecessary automatic braking and alarm output for a very short period of time.

  As mentioned above, although embodiment which concerns on this invention was described, this invention is implemented in various forms, without being limited to the said embodiment.

  For example, in the present embodiment, the present invention is applied to a collision prevention device that performs driving assistance (automatic braking, warning) when there is a possibility of collision, but it is applied to other driving assistance devices such as a device that performs only collision determination. May be. Further, as driving assistance, only one of automatic braking and warning may be performed, or other driving assistance such as information provision may be performed.

Further, in the present embodiment, only when TTC _2nd is a real number (actually, when conditional expression (3) is not satisfied), the TTC threshold is determined to determine the possibility of collision. However, TTC _2nd The possibility of collision may be determined using TTC _2nd only when is a real number, or the possibility of collision may be determined using both TTC and TTC _2nd . Also, various other determination methods can be applied to the collision determination. For example, instead of determining with one threshold value, the possibility of a collision is determined step by step using a plurality of threshold values.

In the present embodiment, the conditional expression (3) is used to determine whether the TTC _2nd is implemented or imaginary after taking the adaptation constant α into account, but it may be determined using a conditional expression that does not take into account the adaptation constant α. Alternatively, it may be determined by the value of TTC _2nd itself.

  In this embodiment, millimeter wave radar is applied as means for detecting the preceding vehicle. However, other detection means such as a laser radar or a camera may be applied. In the case of a laser radar or camera, if a preceding vehicle can be detected based on radar information or image information, the relative distance from the preceding vehicle is calculated, the relative speed is calculated by time differentiation, and the relative speed is calculated. The relative acceleration is calculated by differentiating the speed with time. Alternatively, information on the position and speed of the preceding vehicle may be acquired by inter-vehicle communication, and the relative distance, relative speed, and relative acceleration may be calculated using the acquired information.

  DESCRIPTION OF SYMBOLS 1 ... Collision prevention device, 10 ... Millimeter wave radar, 20 ... Brake actuator, 21 ... Alarm device, 30 ... ECU

Claims (3)

A driving support device for determining the possibility of a collision between the host vehicle and another vehicle,
Using the relative distance D _r and the relative velocity V _r between the host vehicle and another vehicle, a first calculating means for calculating the estimated collision time lengths TTC by the following formula (1),
The relative distance _{D r} between the host vehicle and another vehicle, using the relative velocity _{V r} and the relative acceleration _{A r,} a second calculating means for calculating a second estimated collision time lengths _{TTC 2nd} by the following equation (2),
Only when the second predicted collision time TTC _2nd is a real number, a collision that determines the possibility of a collision between the host vehicle and another vehicle using at least one of the predicted collision time TTC and the second predicted collision time TTC _2nd A driving support apparatus comprising: a determination unit.

The driving support for preventing a collision is performed only when the collision determination unit determines that there is a possibility of a collision when the second predicted collision time TTC _2nd is a real number. Driving assistance device. The collision determination means uses the constant α and uses only at least one of the predicted collision time TTC and the second predicted collision time TTC _2nd only when the following conditional expression (3) is not satisfied. The driving support device according to claim 1, wherein a possibility of a collision with a vehicle is determined.

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