JP2007030655A - Automatic braking device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To control braking of an own vehicle to an operation state in timing suitable for the type (basically, the vehicle weight) of a preceding vehicle in order to appropriately ensure an inter-vehicle distance between the own vehicle and the preceding vehicle when braking in the system to control the braking of the own vehicle based on the inter-vehicle and the relative speed (detected value). <P>SOLUTION: An automatic braking device for the vehicle is equipped with a means 12 (S4 in Fig.2) measuring the inter-vehicle distance between the own vehicle and the preceding vehicle, a means 16 (S6 in Fig.2) setting a limit inter-vehicle distance between the own vehicle and the preceding vehicle to react the braking of the preceding vehicle, a means 14 (S7 to S8 in Fig.2 or S9 to S19, S21 in Fig.3) estimating the type of vehicle of the preceding vehicle or the vehicle weight, the means 16 (S22 in Fig.2 or S20 in Fig.3) correcting the set value of the limit inter-vehicle distance based on the estimation, and the means 16 (S23 to S25 in Fig.2) controlling the braking device of the own vehicle to the operation state when the measured value of the inter-vehicle distance is smaller than the set value of the limit inter-vehicle distance of the time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an automatic braking device for a vehicle, and relates to an automatic braking device suitable for a large vehicle such as a truck.

In order to ensure safe traveling of a vehicle, a system is known that controls braking of the host vehicle based on the inter-vehicle distance and relative speed (detected value) between the host vehicle and the preceding vehicle (Patent Document 1). When the trigger switch is on and the vehicle speed of the host vehicle exceeds the vehicle speed of the preceding vehicle, the target deceleration is calculated from a uniform equation using the inter-vehicle distance and relative speed as variables, and the target deceleration and maximum deceleration are calculated. Based on the comparison, if the target deceleration is equal to or less than the maximum deceleration, the vehicle's braking device (brake actuator) is controlled so as to obtain the target deceleration, while if the target deceleration exceeds the maximum deceleration, The vehicle brake actuator is controlled so as to obtain the maximum deceleration.
JP2003-104184A

  Assuming that the system is installed in a truck or other large vehicle, if the vehicle ahead is a lightweight passenger vehicle, the deceleration of the vehicle is smaller than the deceleration of a lightweight passenger vehicle, and the inter-vehicle distance is likely to be clogged. Become. For this reason, it is desirable to actuate braking of the vehicle early. However, if a uniform calculation formula for obtaining the target deceleration is set on the assumption that the front car is a passenger car, the braking of the host vehicle will always operate quickly. It can give a strange feeling to the person.

An object of this invention is to provide an effective means for coping with such a problem .

  1st invention WHEREIN: In the automatic braking device of a vehicle, the means to measure the distance between the own vehicle and the preceding vehicle, The means to set the limit distance between the own vehicle and the preceding vehicle which can respond to the braking of the preceding vehicle, Means for estimating the vehicle type or vehicle weight of the preceding vehicle, means for correcting the set value of the limit inter-vehicle distance based on the estimate, and the own vehicle when the measured value of the inter-vehicle distance is smaller than the set value of the limit inter-vehicle distance at that time Means for controlling the braking device in an operating state.

  According to a second aspect of the present invention, in the automatic braking device for a vehicle according to the first aspect of the invention, the means for setting the limit inter-vehicle distance between the host vehicle and the preceding vehicle that can handle sudden braking of the preceding vehicle is a relative speed with respect to the preceding vehicle. The limit inter-vehicle distance is set according to the relative speed with respect to the preceding vehicle.

  According to a third aspect of the present invention, in the automatic braking device for a vehicle according to the first aspect, the means for estimating the vehicle type or the vehicle weight of the preceding vehicle comprises means for receiving vehicle information from the preceding vehicle. The vehicle type or vehicle weight is estimated from vehicle information from the preceding vehicle.

  According to a fourth aspect of the present invention, in the automatic braking device for a vehicle according to the first aspect, the means for estimating the vehicle type or the vehicle weight of the front vehicle scans the rear surface of the front vehicle in the vehicle width direction around a fixed point of the own vehicle. Means for calculating the vehicle width of the preceding vehicle from the measured value of the scan angle and the inter-vehicle distance, and the vehicle type or vehicle weight of the preceding vehicle is estimated from the calculated value of the vehicle width. .

  According to a fifth aspect of the present invention, in the automatic braking device for a vehicle according to the fourth aspect, the means for scanning the rear surface of the front vehicle in the vehicle width direction around the fixed point of the own vehicle changes the irradiation angle in the vertical direction of the scan. It is characterized by being repeated.

  According to a sixth invention, in the automatic braking device for a vehicle according to the fourth invention, a means for setting a reference value for distinguishing the vehicle type or the vehicle weight, based on a comparison between this reference value and a calculated value of the vehicle width Means for determining the vehicle type or vehicle weight of the preceding vehicle.

  In a seventh aspect of the automatic braking device for a vehicle according to the first aspect of the invention, when the measured value of the inter-vehicle distance is smaller than the set value of the limit inter-vehicle distance at that time, the braking device of the own vehicle is controlled to be in an operating state. The means includes means for obtaining a relative speed with respect to the preceding vehicle and means for obtaining a braking deceleration according to the relative speed, and the braking device of the own vehicle is controlled to an operating state according to the braking deceleration. It is characterized by that.

  According to an eighth aspect of the present invention, in the automatic braking device for a vehicle according to the second or seventh aspect, the means for obtaining the relative speed with the preceding vehicle is a unit time of a calculated value of the inter-vehicle distance as the relative speed with the preceding vehicle. It is a means for obtaining the amount of change per hit.

  In the first invention, the vehicle type or vehicle weight of the preceding vehicle is estimated, and the set value of the limit inter-vehicle distance is corrected based on the estimation. For example, if the host vehicle is a large vehicle and the front vehicle is a lightweight passenger car, when the limit inter-vehicle distance setting value is greatly corrected, the timing at which the measured inter-vehicle distance value becomes smaller than the limit inter-vehicle distance setting value Get faster. In other words, the braking device of the own vehicle is controlled to operate from the region where the measured value of the inter-vehicle distance is large, and the inter-vehicle distance is reduced regardless of the difference between the deceleration of the own vehicle and the deceleration of the preceding vehicle. Properly secured without clogging. If your vehicle is a large vehicle and the vehicle in front is also a large vehicle, the limit inter-vehicle distance setting value will be corrected to be smaller than in the case of a passenger car with a light vehicle ahead, and the measured value of the inter-vehicle distance will be less than the limit inter-vehicle distance setting value. Therefore, the distance between the two vehicles is delayed, so that the distance between the vehicles is appropriately secured without causing the driver to feel uncomfortable.

  In the second aspect of the invention, the limit inter-vehicle distance is not constant, and is set according to the relative speed with the preceding vehicle. Therefore, it is possible to appropriately cope with the braking state (rapid braking, slow braking) of the preceding vehicle. It becomes.

  In the third invention, by receiving the vehicle information from the preceding vehicle, it is possible to estimate the vehicle type or the vehicle weight of the preceding vehicle from the vehicle information. Of course, it is a premise that the preceding vehicle is provided with vehicle information transmitting means that can estimate the vehicle type and vehicle weight, and ideally, it is desirable to obtain vehicle information that can estimate the inertial mass of the preceding vehicle. Thus, it becomes possible to control the braking device of the own vehicle to the operating state at a timing suitable for the inertial mass of the preceding vehicle.

  In the fourth invention, the vehicle width of the front vehicle is calculated from the scan angle and the measured value of the inter-vehicle distance on the rear surface of the front vehicle, and the vehicle type or vehicle weight of the front vehicle is estimated from this calculated value. For example, when the calculated value of the vehicle width is large, the preceding vehicle can be determined as a large vehicle such as a truck, and when the calculated value of the vehicle width is small, the preceding vehicle can be determined as a passenger car.

  In the fifth aspect of the invention, since the scanning is repeated while changing the irradiation angle in the vertical direction, the vehicle type or vehicle weight of the preceding vehicle is accurately estimated based on a plurality of calculated values of the difference in vehicle width. Is possible.

  In the sixth invention, by comparing the calculated value of the vehicle width with the reference value, for example, when the calculated value of the vehicle width is equal to or larger than the reference value, the preceding vehicle is a large vehicle such as a truck, and the calculated value of the vehicle width is the reference value. When the value is lower than the value, the vehicle ahead can be easily determined as a passenger car.

  In the seventh aspect of the invention, the braking device of the host vehicle is controlled so as to obtain a braking deceleration according to the relative speed with the preceding vehicle, so that the braking state (sudden braking, slow braking) of the preceding vehicle is prevented. And an appropriate braking force can be generated.

  In the eighth aspect of the invention, the relative speed with respect to the preceding vehicle can be easily obtained only by measuring the inter-vehicle distance without depending on the vehicle speed sensor.

  An example of application to a large vehicle (for example, a truck) according to an embodiment of the present invention will be described based on the drawings. In FIG. 1, 10 is a large vehicle (own vehicle), 30 is a front vehicle, and an automatic braking device is mounted on the own vehicle 10 (large vehicle). The automatic braking device includes a radar device 11, an inter-vehicle distance measuring unit 12, a forward vehicle information receiving unit 13, a vehicle type or vehicle weight estimating unit 14 of the preceding vehicle 30, a vehicle speed detecting unit 15, a control start distance calculating unit 16, The braking deceleration calculating means 17 and the braking device 18 of the own vehicle are included.

  The radar device 11 irradiates an electromagnetic wave such as a millimeter wave or a pulse wave of laser light in front of the vehicle, and measures the arrival time of the reflected wave. The radar device 11 is installed on the front surface of the vehicle, and is supported so that the direction of the radar device 11 can be rotated in the left-right direction and the up-down direction with respect to the center of the vehicle width. The inter-vehicle distance measuring means 12 calculates the inter-vehicle distance from the preceding vehicle 30 from the measured value of the arrival time of the reflected wave based on the output of the radar device 11. The forward vehicle information receiving means 13 is configured as a part of a communication device using wireless communication, a cellular phone communication network, or the like, and receives transmission data of the forward vehicle 30.

  The vehicle type or vehicle weight estimation unit 14 of the preceding vehicle 30 performs scanning by the radar device 11 when vehicle information (reception data) that can estimate the vehicle type or vehicle weight of the preceding vehicle 30 cannot be obtained from the front vehicle information receiving unit 13. While controlling (scan), the vehicle width of the forward vehicle 30 is obtained from the scan angle from the radar device 11 and the calculated value (inter-vehicle distance) from the inter-vehicle distance measuring means 12, and from this vehicle width, By estimating the vehicle weight, a correction distance (correction value of the limit inter-vehicle distance) corresponding to this estimation is obtained. The radar device 11 is controlled by the vehicle type or vehicle weight estimating means 14 of the front vehicle 30 and scans the rear portion of the front vehicle 30 in the vehicle width (left and right) direction around a fixed point.

  Based on the output of the inter-vehicle distance measuring unit 12, the control start distance calculating unit 16 obtains the amount of change per unit time of the measured value of the inter-vehicle distance as the relative speed between the host vehicle 10 and the preceding vehicle 30, and based on this relative speed. Set the limit inter-vehicle distance. The limit inter-vehicle distance is the maximum inter-vehicle distance that can cope with the braking of the front vehicle 30 and is given a set value according to the relative speed with the front vehicle 30.

  The vehicle type or vehicle weight estimation unit 14 of the preceding vehicle 30 receives the received data, the preceding vehicle 30 when vehicle information (reception data) that can estimate the vehicle type or vehicle weight of the preceding vehicle 30 is obtained from the preceding vehicle information receiving unit 13. The inertial mass of the forward vehicle 30 is estimated from the relative speed of the vehicle 10 and the vehicle speed (detection value) of the host vehicle 10 to obtain a correction distance (correction value of the limit inter-vehicle distance) corresponding to this estimation.

  The control start distance calculation means 16 is based on the correction distance from the vehicle type or vehicle weight estimation means 14 of the preceding vehicle 30 (correction value based on scanning by the radar device 11 or correction value based on front vehicle information) = While setting the limit inter-vehicle distance (set value) + correction value, by comparing the measured value of the inter-vehicle distance and the control start distance, if the inter-vehicle distance <the control start distance, the operation command to the braking device 18 of the host vehicle is When the inter-vehicle distance is equal to or greater than the control start distance, a stop (release) command to the braking device 18 of the own vehicle is output.

  Based on the output of the control start distance calculation means 16, the deceleration calculation means 17 can obtain a deceleration according to the relative speed of the braking device 18 of the own vehicle with the preceding vehicle 30 when the inter-vehicle distance <the control start distance. Control to the operating state. In the deceleration calculation means 17, it is conceivable to control the braking device 18 of the own vehicle to an operation state in which the maximum deceleration is always obtained on the assumption that the forward vehicle 30 is suddenly braked.

  2 and 3 are flowcharts for explaining the operation (control contents) of the automatic braking device, which is activated by turning on the engine key switch, and performs a predetermined initialization in S1. Thereafter, the processes after S2 are repeated while the vehicle speed> 0 [km / h]. In S2, the radar apparatus 11 irradiates electromagnetic waves forward, and measures the arrival time T of the reflected wave. In S3, it is determined from the measurement of the arrival time T of the reflected wave whether the preceding vehicle is “present”. If the determination of S3 is yes, the process proceeds to S4. If the determination of S3 is no, the process jumps to S28.

In S4, based on the output of the radar device 11, the inter-vehicle distance Ld between the host vehicle 10 and the preceding vehicle 30 is calculated from the arrival time T of the reflected wave. Vehicle distance Ld, when the electromagnetic wave propagation velocity between 3 × 10 ^8, obtained from ^{Ld = 3 × 10 8 × (} T / 2) ( Fig. 7, reference). In S5, the amount of change per unit time of the inter-vehicle distance Ld (measured value) is calculated as the relative speed with the preceding vehicle 30. In S6, the limit inter-vehicle distance corresponding to the relative speed (change amount per unit time of inter-vehicle distance Ld) with the preceding vehicle 30 is set by searching map data (not shown).

  In S7, vehicle information from the preceding vehicle 30 is received. When the reception data is obtained, the inertial mass of the forward vehicle 30 is estimated. The inertial mass of the front vehicle 30 is obtained from the vehicle speed (detected value) of the host vehicle 10 and the relative speed between the front vehicle 30 and the vehicle speed of the front vehicle 30 and the vehicle weight of the front vehicle 30 (received data). ). In S8, it is determined whether or not the estimation of the inertial mass based on the output of the forward vehicle information receiving means 13 is completed. When the determination of S8 is yes, the process proceeds to S22, while when the determination of S8 is no, the process proceeds to S9 (see FIG. 3).

  In S22, a correction value (distance) corresponding to the inertial mass (estimated value) of the preceding vehicle 30 is obtained by searching map data (not shown), and control start distance = limit inter-vehicle distance (set value) + correction value. Set. In S23, it is determined whether the following distance (measured value) <control start distance. When the determination of S23 is yes, the process proceeds to S24 and S25, while when the determination of S23 is no, the process proceeds to S26 and S27. In S24 and S25, the brake flag is set to 1, and a search value (front vehicle) obtained from a predetermined value (maximum deceleration signal) or map data (see FIG. 5) as an operation signal to the braking device 18 of the own vehicle. On the other hand, in S26 and S27, the brake flag is reset to 0 and a stop (release) signal is given to the braking device 18 of the own vehicle.

In S9, the irradiation angle α of the radar apparatus 11 in the vertical direction is set to 0 ° (the inclination angle with respect to the horizontal line on the vehicle is 0 °). In S10, the radar device 11 scans the rear surface of the front vehicle 30 in the vehicle width direction. The radar apparatus 11 measures the scan angles β ₁ and β ₂ corresponding to the vehicle width of the front vehicle 30 by scanning from the center of the vehicle width (horizontal line passing through the center on the vehicle) to the left and right (FIG. 6). ,reference). Further, the inter-vehicle distance Ld at the irradiation angle α = 0 ° is measured (see FIG. 7). In S11, the vehicle width Lw = Ld × (tan β ₁ + tan β ₂ ) of the front vehicle 30 is obtained from the scan angles β ₁ and β ₂ and the inter-vehicle distance Ld.

  In S12, whether or not Lw ≧ reference value is determined by comparing the vehicle width Lw of the forward vehicle 30 (calculated value in S11) with a reference value (for example, 3 m) for distinguishing the vehicle type or vehicle weight of the forward vehicle 30. judge. If the determination in S12 is yes, the process jumps to S21, and the preceding vehicle 30 is estimated as a large vehicle. On the other hand, if the determination in S12 is no, the process proceeds to S13.

In S13, the irradiation angle α = α ₁ (eg, 1.2 °) in the vertical direction of the radar apparatus 11 is set (see FIG. 7). In S14, the scanning angle β ₁ ′, β ₂ ′ corresponding to the vehicle width of the front vehicle 30 is measured by causing the radar device 11 to scan the rear surface of the front vehicle 30 in the vehicle width direction. Further, by measuring the inter-vehicle distance Ld ′ at the irradiation angle α = α ₁ , the vehicle width Lw ′ = Ld ′ × (tan β _{1 of the} preceding vehicle is obtained from the scan angles β ₁ ′, β ₂ ′ and the inter-vehicle distance Ld ′. '+ Tanβ ₂ '). In S15, LW ′ ≧ reference value is obtained by comparing the vehicle width Lw ′ (calculated value in S14) of the preceding vehicle 30 with a reference value (for example, 3 m) for distinguishing the vehicle type or vehicle weight of the preceding vehicle 30. Determine if. When the determination of S15 is yes, the process jumps to S21, and the preceding vehicle 30 is estimated as a large vehicle, while when the determination of S15 is no, the process proceeds to S16.

In S16, the irradiation angle α = α ₂ (for example, 2.3 °) in the vertical direction of the radar apparatus 11 is set. In S17, the radar apparatus 11 scans the rear surface of the front vehicle 30 in the vehicle width direction, thereby measuring scan angles β ₁ ″ and β ₂ ″ corresponding to the vehicle width of the front vehicle 30. Further, by measuring the inter-vehicle distance Ld ″ at the irradiation angle α = α ₂ , the vehicle width Lw ″ = Ld ″ × (tan β _{1 of the} preceding vehicle is obtained from the scan angles β ₁ ″, β ₂ ″ and the inter-vehicle distance Ld ″. “+ Tanβ ₂ ”). In S18, whether or not LW ″ ≧ reference value is determined by comparing the vehicle width Lw ″ of the preceding vehicle (calculated value in S17) with a reference value (for example, 3 m) for distinguishing the vehicle type or vehicle weight of the preceding vehicle. judge. If the determination in S18 is yes, the process jumps to S21 and the preceding vehicle 30 is estimated as a large vehicle, while if the determination in S18 is no, the process proceeds to S19, and the preceding vehicle 30 is estimated as a passenger car.

  In S20, a correction value (distance) corresponding to the estimation of S19 or S21 is obtained by searching map data (not shown), and the control start distance is calculated by adding to the limit inter-vehicle distance of S6 (see FIG. 4). Thereafter, the processing returns to S2 through the processing of S23 to S27. If the determination in S3 is no, it is determined in S28 whether the brake flag = 1. When the determination of S28 is yes, the process proceeds to S29 and S30, while when the determination of S28 is no, the process returns to S2. In S29, the brake flag is reset to zero. In S30, a stop (release) signal is given to the braking device 18 of the own vehicle. After the processing of S29 and S30, the process returns to S2.

  With such a configuration, the vehicle weight or vehicle type of the preceding vehicle 30 is estimated based on the reception of the preceding vehicle information or the scan of the radar device 11, and a correction value corresponding to the estimation is added to the limit inter-vehicle distance. When the inertial mass of the forward vehicle 30 is small as in a passenger car, the correction value added to the limit inter-vehicle distance becomes large, and the braking device 18 of the own vehicle is controlled to be in an operating state earlier from a region where the inter-vehicle distance measurement value is large. Therefore, regardless of the difference between the deceleration of the host vehicle 10 and the deceleration of the forward vehicle 30, the inter-vehicle distance is appropriately secured without becoming too clogged. When the inertial mass of the forward vehicle 30 is large as in a large vehicle, the correction value added to the limit inter-vehicle distance is small, and the timing at which the measured value of the inter-vehicle distance becomes smaller than the control start distance is relatively delayed. The vehicle is properly secured without spreading too much and does not give the driver a sense of incongruity (see FIG. 4).

When the vehicle weight is obtained from the preceding vehicle information, the braking device 18 of the own vehicle can be controlled to be activated at a timing suitable for the inertial mass of the preceding vehicle 30. When vehicle information that can estimate the inertial mass from the preceding vehicle 30 is not obtained, the vehicle width of the preceding vehicle 30 is measured and the calculated vehicle width and the reference value are calculated. If the calculated value of the vehicle width is equal to or greater than the reference value, the forward vehicle 30 is simply determined to be a large vehicle such as a truck, and if the calculated vehicle width is less than the reference value, the forward vehicle 30 is determined to be a passenger car (estimated). ) In the control of FIG. 3, the scan of the radar device 11 is repeated while changing the irradiation angle in the vertical direction, and therefore includes the rear surface shape of the forward vehicle 30 based on a plurality of calculated values of different vehicle widths. It is possible to accurately estimate the vehicle type in the form. The reference value to be compared with the measured value of the vehicle width is naturally controlled according to the measured value of the inter-vehicle distance. The irradiation angles α ₁ and α _{2 in} the vertical direction of the radar apparatus 11 may be controlled according to the measured value of the inter-vehicle distance instead of a fixed predetermined value.

1 is a schematic configuration diagram of a system according to an embodiment of the present invention. It is a flowchart explaining the control content of a system similarly. It is a flowchart explaining the control content of a system similarly. It is a characteristic view explaining the contents of control of a system similarly. It is a characteristic view explaining the contents of control of a system similarly. It is explanatory drawing which similarly concerns on the control content of a system. It is explanatory drawing which similarly concerns on the control content of a system.

Explanation of symbols

10 Own car (large car)
DESCRIPTION OF SYMBOLS 11 Radar apparatus 12 Inter-vehicle distance measuring means 13 Forward vehicle information receiving means 14 Estimating means of vehicle type or vehicle weight of preceding vehicle 15 Vehicle speed detecting means 16 Control opening distance calculating means 17 Braking deceleration calculating means 18 Braking deceleration calculating means 18 apparatus

Claims (8)

  Means for measuring the inter-vehicle distance between the host vehicle and the preceding vehicle, means for setting a limit inter-vehicle distance between the host vehicle and the preceding vehicle that can handle braking of the preceding vehicle, means for estimating the vehicle type or vehicle weight of the preceding vehicle, Means for correcting the set value of the limit inter-vehicle distance based on the estimation, and means for controlling the braking device of the own vehicle to be in an operating state when the measured value of the inter-vehicle distance is smaller than the set value of the limit inter-vehicle distance at that time An automatic braking device for a vehicle.   The means for setting the limit inter-vehicle distance between the host vehicle and the preceding vehicle that can handle the braking of the preceding vehicle comprises means for determining the relative speed with the preceding vehicle, and the limit inter-vehicle distance is the relative speed with the preceding vehicle. The automatic braking device according to claim 1, wherein the automatic braking device is set according to   The means for estimating the vehicle type or vehicle weight of the preceding vehicle comprises means for receiving vehicle information from the preceding vehicle, wherein the vehicle type or vehicle weight of the preceding vehicle is estimated from the vehicle information from the preceding vehicle. The automatic braking device according to claim 1, wherein   The means for estimating the vehicle type or vehicle weight of the preceding vehicle is a means for scanning the rear surface of the preceding vehicle in the vehicle width direction around a fixed point of the own vehicle, and calculating the vehicle width of the preceding vehicle from the scan angle and the measured value of the inter-vehicle distance. The automatic braking device according to claim 1, wherein the vehicle type or the vehicle weight of the preceding vehicle is estimated from a calculated value of the vehicle width.   5. The automatic control device according to claim 4, wherein the means for scanning the rear surface of the front vehicle around the fixed point of the own vehicle in the vehicle width direction is repeated while changing the irradiation angle in the vertical direction of the scan.   Means for setting a reference value for discriminating the vehicle type or vehicle weight, and means for determining the vehicle type or vehicle weight of the preceding vehicle based on a comparison between the reference value and the calculated value of the vehicle width. The automatic braking storage according to claim 4.   When the measured value of the inter-vehicle distance is smaller than the set value of the limit inter-vehicle distance at that time, the means for controlling the braking device of the own vehicle to the operating state is a means for obtaining a relative speed with respect to the preceding vehicle, and according to the relative speed The automatic braking device according to claim 1, further comprising a means for obtaining a braking deceleration, wherein the braking device of the host vehicle is controlled to an operating state corresponding to the braking deceleration.   The means for obtaining a relative speed with respect to the preceding vehicle is a means for obtaining an amount of change per unit time of a calculated value of the inter-vehicle distance as a relative speed with respect to the preceding vehicle. Automatic braking device.

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