JP2005186936A - Automatic braking control device of vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a vehicle to travel according to an operator's intention when the vehicle detects an obstacle ahead and stops by automatic braking. <P>SOLUTION: When the vehicle comes to a substantial stop state by automatic braking, this automatic braking control device determines a braking force for maintaining the stop state of the vehicle, and brakes and controls the vehicle with the determined braking force. When the vehicle starts travel again and vehicle speed reaches a predetermined value or higher, the automatic braking control device releases the braking force. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an automatic braking control device for a vehicle that automatically applies braking according to the situation at the time when an obstacle ahead of the vehicle is detected.

  Conventionally, in order to prevent a collision or rear-end collision, an obstacle ahead of the host vehicle is detected, and if the distance between the obstacle and the host vehicle gets closer, the distance (threshold) that is judged as dangerous is determined. There has been proposed a technique for issuing some warning to the driver or automatically braking when approaching beyond.

For example, Japanese Patent Application Laid-Open No. 6-298022 discloses a device that performs automatic braking based on a distance (inter-vehicle distance) from a front object (preceding vehicle) obtained by radar, a relative speed, and the own vehicle speed. More specifically, in this device, a first threshold value that can prevent a rear-end collision with a preceding vehicle by braking based on the host vehicle speed, an inter-vehicle distance, and a relative speed, and a second threshold that can prevent a rear-end collision with a preceding vehicle by a steering operation. The threshold value is calculated. Even if the detected inter-vehicle distance is smaller than the first threshold value, braking is not performed when the distance is larger than the second threshold value. Like to do. As a result, the rear-end collision is prevented as intended by the driver.
JP-A-6-298022

  However, in the conventional automatic braking control device including the device described in the above publication, the automatic braking continues to operate even after the vehicle stops due to the automatic braking. Even if the accelerator operation is performed, there is a problem that the vehicle is difficult to move forward (sometimes it does not move).

  On the other hand, a method of releasing automatic braking after operating for a certain period of time can be considered, but since automatic braking is performed regardless of the driver's intention, the driver automatically brakes when the vehicle stops due to automatic braking. Even if the vehicle is started before the vehicle is released, there is an inconvenience that the vehicle cannot start because automatic braking continues to operate.

  On the other hand, when the vehicle is stopped by automatic braking and then the automatic braking is released after operating for a certain period of time, if the road surface is not flat, the vehicle starts to move, which may cause a secondary collision. is there.

  As another countermeasure, there is a method of releasing automatic braking when it is detected that the driver has stepped on the accelerator. However, in this method, the driver mistakenly presses the accelerator when the vehicle is decelerated by the automatic braking. When the pedal is depressed and the depression of the accelerator pedal is detected, there is a problem that the automatic braking is released when the automatic braking must be performed.

  The present invention has been made in view of the above-described conventional problems, and after the vehicle has been stopped by automatic braking, the automatic braking control of the vehicle that can appropriately release the automatic braking according to the driver's intention. It is an object to provide an apparatus.

  As shown in FIG. 1, the present invention has an obstacle detection means for detecting an obstacle ahead of the vehicle, and automatically brakes the vehicle when the obstacle is detected under a predetermined condition. In the automatic braking control device for a vehicle, stop determination means for determining that the vehicle has substantially stopped after the automatic braking is activated, and a braking force lower than the full braking force used for the automatic braking, Braking force determining means for determining a braking force for maintaining the stop state of the vehicle, and braking the vehicle with the braking force determined by the braking force determining means when the stop determining means determines that the vehicle has stopped Braking force control means for controlling, travel determination means for determining that the vehicle has started traveling and the vehicle speed has reached a predetermined value, and when the travel determination means determines that the vehicle has started traveling again Solve the braking force By having a release means that is obtained by solving the above problems.

  According to the present invention, after the vehicle is stopped by automatic braking, the braking force for maintaining the stopped state of the vehicle is smaller than the braking force for avoiding the collision with the obstacle. Set as the minimum braking force necessary to maintain the vehicle, and if the driver tries to start the vehicle again, the braking will be released immediately and the start will be smooth to respond to the driver's intention Vehicle travel is possible.

  According to the present invention, when the vehicle is stopped by automatic braking, a braking force that can maintain the stopped state is applied to the vehicle, and when the driver detects an intention to start the vehicle, the braking force is controlled. Since the power is completely released, the vehicle can be driven in accordance with the driver's accelerator operation.

  In addition, when the braking force is determined according to the road surface gradient state, it is possible to reliably prevent the vehicle from moving when the vehicle stops.

  In a preferred embodiment, the automatic braking control device for the vehicle further includes a gradient state detecting unit that detects a gradient state of the road surface, and the braking force determining unit stops the vehicle based on the detected gradient state. It is to determine the braking force for maintaining the state. Thus, since the braking force is determined according to the road surface gradient, even when the road surface is steep, it is possible to reliably maintain the stop state of the vehicle.

  Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a schematic configuration diagram of an automatic braking control apparatus to which the present invention is applied.

  In FIG. 2, a control device (ECU) 10 includes an on / off signal of a brake switch 14 for detecting that the driver has depressed the brake pedal 12, and a steering angle for detecting a steering angle α of the steering wheel 17. A signal from the sensor 18, a signal from the accelerator sensor 16 for detecting that the accelerator pedal 15 has been depressed, a signal from the radar (obstacle detection means) 20 for detecting the distance Lc to the obstacle, the own vehicle A signal from the wheel speed sensors 22 to 28 for detecting the vehicle speed V, a signal from the yaw rate sensor 30 as information for obtaining the yaw rate γ, a signal from the gradient sensor 31 for detecting the road surface gradient, and the magnitude of the impact due to the collision Signals from the G sensor 32 and the G switch 33 for detecting the vehicle speed by the acceleration G of the vehicle are input.

  The control device 10 determines the obstacle information based on these inputted signals, and when it is determined that a warning is necessary, the control device 10 issues an instruction of slow braking for warning to the brake actuator 34, and an alarm. 36 is activated, and the brake lamp 38 is lit to notify the following vehicle of the gentle braking (because the driver applies the gentle braking even though the brake pedal 12 is not depressed). Furthermore, when the vehicle still approaches an obstacle, the control device 10 issues a full braking instruction to the brake actuator 34 to avoid a collision. Then, when the vehicle is substantially stopped, a braking force for maintaining the stopped state of the vehicle is determined, an instruction is issued to the brake actuator 34, and the stop is maintained with the braking force. Further, when the driver depresses the accelerator pedal 15 in order to drive the vehicle again and the vehicle speed becomes equal to or higher than a predetermined value, a signal is issued to the brake actuator 34 to release the braking force.

  That is, the control device 10 calculates the vehicle speed V based on signals from the wheel speed sensors 22 to 28, and determines that the vehicle has started to travel and a stop determination unit that determines that the vehicle has substantially stopped. In addition to serving as a travel determination unit, it serves as a braking force determination unit, a braking force control unit, and a release unit that releases the braking force.

  Next, the control in the first embodiment of the present invention will be described with reference to the flowcharts of FIGS.

  First, at step 100, the signal of the radar 20 is input. This signal is processed in the control device 10, and a distance (relative distance) Lc to the obstacle is obtained. In step 102, the control device 10 obtains the host vehicle speed V from the signals of the wheel speed sensors 22 to 28, and calculates the approach speed (relative speed) Vob of the obstacle from the information of the relative distance Lc. Also, the expected arrival time Tc is calculated from these information and the detected distance Lc.

  In this embodiment, it is determined whether or not the obstacle is an oncoming vehicle, and the expected arrival time Tc is calculated in two ways according to the result.

  That is, as shown in FIG. 6, first, at step 102a, it is determined whether or not the relative speed Vob is equal to or lower than the host vehicle speed V. Here, when Vob ≦ V holds, it is determined that the obstacle is either a fixed obstacle or another vehicle ahead traveling in the same direction as the own vehicle, and the process proceeds to step 102b, where the expected arrival is reached. The time Tc is calculated as the following equation (1).

Tc = Lc / Vob (1)
On the other hand, if Vob ≦ V is not satisfied in step 102a, it means that the relative speed Vob is larger than the own vehicle speed V, and therefore an obstacle is approaching the own vehicle. Will be. Accordingly, it is determined that the obstacle is an oncoming vehicle, and in step 102c, the expected arrival time Tc is calculated by the following equation (2).

Tc = Lc / {(1 + α) × V−α × Vob} (2)
Here, α is an oncoming vehicle correction coefficient, and 0 <α <1.

  Returning to FIG. 3, in step 104, the steering angle α signal from the steering angle sensor 18 is input, and the yaw rate γ signal is input from the yaw rate sensor 30. Then, the turning radius R is calculated from the vehicle speed V and the yaw rate γ. Note that the turning radius R = (own vehicle speed V / yaw rate γ).

  Next, at step 106, a full braking threshold Wb is determined, which is a threshold value for applying the full braking when the estimated arrival time Tc is below this value.

  This is determined by the graph of FIG. 7 using the reciprocal ρ of the turning radius R calculated above. In FIG. 7, the horizontal axis represents the reciprocal ρ of the turning radius R, the center 0 represents the case where the turning radius is infinite, that is, the case of straight travel, the right side represents the right curve, and the left side represents the left curve. The vertical axis is the threshold value Wb. If the reciprocal ρ of the turning radius R is now ρ1, the corresponding value Wb1 on the graph is the threshold value (full braking threshold) Wb in this case.

  Next, at step 108, a slow braking threshold Wr is determined, which is a threshold value that the slow braking for warning is performed when the expected arrival time Tc falls below this value. This is also determined by the graph of FIG. 8 using the reciprocal ρ of the turning radius R calculated above, as with the full braking threshold Wb.

  In FIG. 8, the fact that a plurality of graphs are drawn indicates that the timing of the gentle braking can be corrected earlier or later depending on the driver's preference or the like. Which graph is used is selected in advance by the driver by a dial or the like. Moreover, although the graphs of FIGS. 7 and 8 are represented by curves, they may be represented by broken lines.

  Next, in step 110, the vehicle acceleration G representing the magnitude of the impact at the time of actual collision is calculated based on signals from the G sensor 32 and the G switch 33.

  Turning to the control flow of FIG. 4, in step 112, it is determined whether or not the driver is going to start the vehicle after the vehicle has been temporarily stopped by full braking in order to avoid a collision with an obstacle. That is, it is determined whether or not the vehicle speed V is greater than the low vehicle speed threshold V0 and the stop flag Fs is once turned on. When this condition is not satisfied, the process proceeds to the next step 114.

  In step 114, it is determined whether or not the vehicle is almost stopped due to full braking. That is, it is determined whether the vehicle speed V is smaller than the vehicle speed detection lower limit value V1 (V1 <V0). If this condition is not satisfied, the process proceeds to the next step 116.

  In step 116, it is determined whether or not a large impact is applied to the vehicle due to a collision or the like despite full braking. That is, whether or not the acceleration G calculated in step 110 exceeds the impact threshold G0 and is within the full braking flag effective period Tff indicating that it is necessary to continue full braking as it is when full braking is performed. Judge. If these conditions are not satisfied, the process proceeds to the next step 118.

  In step 118, it is determined whether or not it is within the full braking duration Tf during which full braking continues. If it is not within the full braking duration Tf, the routine proceeds to the next step 120.

  In step 120, it is determined whether the obstacle is still approaching and full braking is required. That is, it is determined whether the expected arrival time Tc is less than the full braking threshold Wb and is within the warning flag effective period Tkf. If these conditions are not satisfied, the process proceeds to step 122 in FIG.

  In step 122, it is determined whether or not the driver is performing a collision avoidance operation by stepping on the brake pedal 12 or operating the steering wheel 17. That is, it is determined whether or not the steering speed dα, which is the speed at which the brake switch 14 is turned on or the steering wheel 17 is operated, exceeds the steering speed threshold (threshold value) dα0 (whether or not it is a sudden steering wheel). If these conditions are not satisfied, the process proceeds to the next step 124.

  In step 124, it is determined whether or not it is within the slow braking duration Tk during which the slow braking continues. If it is not within the slow braking duration Tk, the process proceeds to the next step 126.

  In step 126, it is determined whether or not the flag FLG indicating that the gentle braking is once released is turned on when the slow braking duration Tk has elapsed within the warning flag effective period Tkf. If the flag FLG is off, the process proceeds to the next step 128.

  In step 128, it is determined whether or not a gentle braking for warning is necessary, that is, whether or not the driver is performing an avoidance operation despite the presence of an obstacle in the range where the gentle braking is necessary. That is, the expected arrival time Tc interrupts the slow braking threshold Wr, is smaller than the slow braking threshold Wr, and the brake switch 14 is off (that is, the driver is not stepping on the brake pedal 12, and the avoidance operation is performed by braking). It is determined whether or not the steering speed dα of the steering wheel 17 is smaller than the steering speed threshold dα0 (that is, the driver does not avoid the steering operation). As a result, when the gentle braking is not necessary, the process proceeds to the next step 130.

  In step 130, if the automatic braking control has been performed until then, the automatic braking control is canceled, and the operation of the alarm 36 and the brake lamp 38 is canceled. If the automatic braking control is not originally performed, nothing is actually performed here.

  If it is determined in step 128 that the gentle braking is necessary, the process proceeds to step 132, and the slow braking duration and the warning flag effective period indicated by Tk and Tkf in FIG. 9 are calculated. Then, in step 134, slow braking is started, the alarm 36 and the brake lamp 38 are activated, and the flag FLG is turned on.

  If it is determined in step 122 that the driver has performed braking or avoidance operation by the steering wheel 17 as a result of the slow braking for warning, the routine proceeds to step 136, where the slow braking duration Tk and the warning flag Fk are reset. . Then, the slow braking is released, the operation of the alarm 36 and the brake lamp 38 is released, and the flag FLG is turned off.

  If the driver does not perform the avoidance operation despite the gentle braking, and it is determined in step 124 that it is within the slow braking duration Tk, the slow braking is continued as it is.

  Further, as indicated by To in FIG. 9, even if the warning flag is within the valid period Tkf, if the slow braking duration period Tk has elapsed, it is determined in step 126 that the gentle braking has been performed so far. If it is determined as ON, the routine proceeds to step 136 where the gentle braking is once released.

  Thereafter, if it is determined in step 120 that the obstacle is still approaching and full braking is necessary, in step 138, the full braking duration Tf and the full braking flag effective period Tff are determined from the graph of FIG. In the next step 140, the full braking is started and the alarm 36 and the brake lamp 38 are activated.

  If it is determined in step 118 that the current time is within the full braking duration Tf, full braking is continued as it is.

  If it is determined in step 116 that the acceleration G of the vehicle is greater than the impact threshold G0 and within the full braking flag effective period Tff in spite of continuing full braking, it is determined that a collision has occurred. In step 142, the full braking duration Tf and the full braking flag effective period Tff are extended to infinity, and in order to avoid damage and harm due to the secondary collision, the full braking is continued in step 144, and the alarm 36 and the brake lamp 38 are Continue operation.

  On the other hand, if it is determined in step 114 that the vehicle speed V has decreased due to full braking and has become smaller than the vehicle speed detection lower limit value V1, it is determined that the vehicle is almost stopped, and the process proceeds to step 146. The stop flag Fs is turned on, and in the next step 148, full braking on the front wheel side is released and full braking is continued only on the rear wheel side. As a result, the vehicle stop state is maintained, but the force to stop the vehicle is lower than when the front wheels are fully braked. In other words, in this state, since the driving force is small in the manner in which the driver depresses the accelerator pedal 15 in the normal running state, the braking force of the rear wheels is large, and the vehicle stop state is maintained. At this time, when the driver really depresses the accelerator pedal 15 in order to move the vehicle, the driving force becomes greater than the braking force of the rear wheels, and the vehicle starts to move. This is just like starting with the parking brake pulled. In other words, in this embodiment, “braking force for full braking only on the rear wheels” is determined as “braking force for maintaining the vehicle stop state” in the claims.

  In step 112, if it is determined that the vehicle speed V is greater than the low vehicle speed threshold V0 and the stop flag is once turned on, the driver has an intention to start the vehicle. It is determined that the vehicle speed V has become higher than the low vehicle speed threshold V0 (although braking of the rear wheels is applied), the stop flag Fs is temporarily turned off in step 150, and full braking of all the wheels is performed in step 152. (In fact, since the full braking of the front wheels has already been released, the full braking of the rear wheels is released here). As a result, all full braking is released, the vehicle can be started easily, and normal running is possible. Note that this braking release is executed gradually (in order not to give the driver a sense of incongruity) because the vehicle is already started.

  In the present embodiment, when an obstacle approaches and the full braking threshold Wb is interrupted, the full braking on the front wheel side is released immediately before stopping after the four-wheel full braking is applied to avoid the collision, Since the braking force is weakened, the turning of the vehicle due to the sudden stop impact can be reduced.

  In this embodiment, full braking is maintained only on the rear wheel side immediately before the vehicle stops, but conversely, full braking may be maintained only on the front wheel side. Alternatively, the braking hydraulic pressure may be set lower than full braking on both the front wheel side and the rear wheel side (for example, both are set to 1/2 of the full braking time).

  Next, the control of the second embodiment will be described.

  In the first embodiment described above, the braking force is uniformly reduced regardless of the road surface state. However, when the road surface is not flat and the slope is steep, the braking force is considered in consideration of the slope state. Need to control. In the second embodiment, the braking force is controlled in accordance with the gradient state by detecting the gradient state of the road surface using a gradient sensor or the like.

  The second embodiment is different from the first embodiment in that the road surface gradient is calculated from the input signal from the gradient sensor 31 at any position between step 100 and step 110 in the flowchart of FIG. In addition to adding (not shown) and replacing step 148 in the flowchart of FIG. 4 as shown in FIG. 11, the hydraulic pressure corresponding to the road surface gradient state (for maintaining the vehicle stop state without excess or deficiency) This is the addition of two steps 160 and 162 for performing braking control with a hydraulic pressure Pd that can generate a braking force).

  The gradient sensor 31 is not particularly limited. If the vehicle has a pitch rate sensor, the gradient sensor 31 may be used, or the G sensor 32 and the G sensor that are already provided even if they are not dedicated sensors. The switch 33 may also be used as a gradient sensor, and the output thereof may be used. Further, if the altitude and road surface gradient are included as road information of the navigation system, that information is used as information from the gradient sensor 31. You can also.

  In step 114 of the flowchart of FIG. 11, when the vehicle speed V falls below the vehicle speed detection lower limit value V1, it is determined that the host vehicle is almost stopped, and in step 146, the stop flag is temporarily turned on.

  In the next step 160, the braking hydraulic pressure Pd of the front and rear wheels is determined from the road gradient D with reference to the map of FIG. As shown in FIG. 12, as the characteristics of the map, the braking hydraulic pressure Pd is the lowest when the road surface gradient D is 0, and is set higher when the road surface gradient D becomes larger. In addition, when the slope is Dr. at the front, the ground contact load on the front wheel side is high, so the braking hydraulic pressure Pdf at the front wheel is increased, and when the slope is at the rear, the control oil pressure Pdr on the rear wheel is increased. Make effective use of the force to stop the vehicle.

  Next, in step 162, hydraulic control of the four wheels is started with the hydraulic pressure Pd determined above. As a result, the force for stopping the vehicle is kept lower than when the four wheels are fully braked while maintaining the stop state of the vehicle. Further, since the hydraulic pressures of the front and rear wheels are distributed in accordance with the direction of the gradient, a large force acts to stop the vehicle when the gradient is tight, so that the vehicle does not start even at a steep gradient.

  Since other points are the same as those in the first embodiment, description thereof is omitted.

Block diagram showing the gist of the present invention Schematic configuration diagram of an automatic braking control device to which the present invention is applied The flowchart which shows control of a 1st embodiment. Similarly, a flowchart showing the control of the first embodiment. Similarly, a flowchart showing the control of the first embodiment. Similarly, a flowchart showing the control of the first embodiment. Diagram showing full braking threshold Diagram showing slow braking threshold Diagram showing slow braking duration and warning flag effective period Diagram showing full braking duration and full braking flag effective period Flowchart showing the control of the second embodiment Diagram showing the relationship between road surface gradient and control oil pressure

Explanation of symbols

10. Control device (ECU)
DESCRIPTION OF SYMBOLS 12 ... Brake pedal 14 ... Brake switch 15 ... Accelerator pedal 16 ... Accelerator sensor 17 ... Steering 18 ... Steering angle sensor 20 ... Radar (obstacle detection means)
22, 24, 26, 28 ... wheel speed sensor 30 ... yaw rate 31 ... gradient sensor 32 ... G sensor 33 ... G switch 34 ... brake actuator 36 ... alarm 38 ... brake lamp

Claims (5)

In an automatic braking control device for a vehicle having an obstacle detecting means for detecting an obstacle in front of the vehicle and automatically braking the own vehicle when an obstacle is detected under a predetermined condition,
Stop determination means for determining that the vehicle has substantially stopped after the automatic braking is activated;
Braking force determining means for determining a braking force that is lower than the full braking force used for the automatic braking and that maintains the stop state of the vehicle;
Braking force control means for controlling braking of the vehicle with a braking force for maintaining the stopped state of the vehicle when it is determined by the stop determination means that the vehicle has stopped;
Traveling determination means for determining that the vehicle starts traveling and the vehicle speed is equal to or higher than a predetermined value;
Release means for releasing the braking force when it is determined by the travel determination means that the vehicle starts traveling again and the vehicle speed is equal to or higher than a predetermined value;
An automatic braking control device for a vehicle, comprising: Comprising a slope state detecting means for detecting the slope state of the road surface;
The braking force determining means determines a braking force for maintaining the stopped state of the vehicle based on the detected gradient state;
The automatic braking control device for a vehicle according to claim 1. The release means releases the braking force after the vehicle has been temporarily stopped by full braking to avoid a collision with the obstacle, and when the driver exceeds a predetermined vehicle speed to start the vehicle. about,
The automatic braking control device according to claim 1. The braking for avoiding the collision with the obstacle is full braking on the four wheels, and the braking in the stopped state is full braking only on the front wheel side or only on the rear wheel side,
The automatic braking control device according to claim 1. The braking for avoiding a collision with the obstacle is full braking on the four wheels, and the braking in the stopped state is braking with a braking hydraulic pressure lower than the full braking,
The automatic braking control device according to claim 1.

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