JP2011025815A - Vehicular contact avoidance supporting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular contact avoidance supporting device which favorably estimates road friction coefficients to control the support for avoiding contact with an obstacle. <P>SOLUTION: When a first road friction coefficient μ1 based on a braking force relative to right and left rear wheels 24L, 24R or right and left front wheels 22R, 22L is different from a second road friction coefficient μ2 based on a braking force relative to right and left front wheels 22R, 22L and right and left rear wheels 24L, 24R, a vehicular contact avoidance support control means 20 of a vehicular contact avoidance supporting device 14 controls the support for contact avoidance based on the second road friction coefficient μ2. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vehicle contact avoidance assisting device that assists in avoiding contact with an obstacle according to the positional relationship between the obstacle ahead of the vehicle and the vehicle.

  Conventionally, a road surface friction coefficient estimating device that estimates a road surface friction coefficient during vehicle travel is known (Patent Document 1). In Patent Document 1, in the anti-skid control (side slip prevention control), the road surface friction coefficient is estimated based on the braking force of the left and right front wheels or the left and right rear wheels (for example, the summary of Patent Document 1, paragraphs [0101], [0105] ]reference).

  In addition, a plurality of ultrasonic sensors arranged in an arc along the front bumper of the own vehicle and cameras arranged on the left and right sides of the own vehicle, the obstacle data in front of the vehicle and the obstacles on the side of the vehicle are There has been proposed a vehicle control device that obtains data and detects an area where the vehicle can proceed while avoiding contact with the obstacle, that is, a contact avoidance area, from these data (Patent Document 2).

  Further, Patent Document 3 discloses a vehicle control device (vehicle posture stabilization device) that stabilizes the behavior of a vehicle based on a yaw rate deviation calculated by comparing a reference yaw rate (also referred to as a reference yaw rate) and an actual yaw rate. Has been proposed.

JP 2002-160622 A (summary, paragraphs [0101] and [0105]) JP 2008-049959 A (paragraph [0019]) JP 2007-276564 A (paragraph [0008])

  As described above, in Patent Document 1, on the premise of anti-skid control, the road surface friction coefficient is estimated based on the braking force of the left and right front wheels or the left and right rear wheels. However, in the assistance control for avoiding contact with an obstacle, there are cases where it is preferable to estimate the road surface friction coefficient based on the braking force of all four wheels (left and right front wheels and left and right rear wheels).

  The present invention has been made in view of such problems, and provides a vehicle contact avoidance assist device capable of preferably estimating a road surface friction coefficient in assist control for avoiding contact with an obstacle. Objective.

  A vehicle contact avoidance assistance device according to the present invention provides assistance for avoiding contact with an obstacle according to the positional relationship between the obstacle ahead of the vehicle and the vehicle, and includes a left and right front wheel and a left and right rear wheel. First road friction coefficient estimating means for estimating a first road friction coefficient by applying braking force to the left and right front wheels or the left and right rear wheels prior to deceleration of the vehicle by applying braking force to the vehicle A contact between the vehicle and the obstacle based on a relative position between the relative position detecting means for detecting a relative position between the vehicle and the obstacle, and an obstacle in front of the vehicle detected by the relative position detecting means; Contact margin value calculating means for calculating a margin value, and vehicle contact avoidance assist for performing contact avoidance assist control with the obstacle based on the first road surface friction coefficient when the contact margin value is equal to or less than a predetermined value. Control means; The second road surface friction coefficient is estimated based on the braking force applied to the left and right front wheels and the left and right rear wheels during deceleration of the vehicle by applying braking force to the left and right front wheels and the left and right rear wheels. Two road surface friction coefficient estimating means, and the vehicle contact avoidance assist control means, when the first road surface friction coefficient and the second road surface friction coefficient are different, based on the second road surface friction coefficient, Control is performed.

  According to the present invention, the braking force is applied to the front wheels or the rear wheels prior to the deceleration of the vehicle by applying the braking force to the left and right front wheels and the left and right rear wheels (applying the braking force to decelerate the vehicle). Thus, the road surface friction coefficient (first road surface friction coefficient) is estimated. This makes it possible to estimate the road surface friction coefficient while making it difficult for the driver to be aware of the deceleration of the vehicle due to the application of braking force. Further, during deceleration of the vehicle by applying braking force to the left and right front wheels and the left and right rear wheels, a road surface friction coefficient (second road surface friction coefficient) is estimated along with the deceleration. When the second road surface friction coefficient is different from the first road surface friction coefficient, the support control is performed based on the second road surface friction coefficient. For this reason, even if the road surface state (road surface friction coefficient) changes during vehicle deceleration accompanying the contact avoidance support control, the support control according to the change can be performed. Furthermore, while assisting contact avoidance, the road surface friction coefficient (second road surface friction coefficient) is estimated by the braking force applied to the left and right front wheels and the left and right rear wheels, so the road surface friction coefficient can be calculated more accurately while maintaining deceleration. Can be estimated.

  The second road surface friction coefficient estimating means is based on a deceleration of the vehicle generated by a braking force applied to the left and right front wheels and the left and right rear wheels generated during the assistance control by the vehicle contact avoidance assistance control means. Two road surface friction coefficients may be estimated.

  The vehicle contact avoidance assistance control means is configured such that the second road friction coefficient estimated by the second road friction coefficient estimation means is smaller than the first road friction coefficient estimated by the first road friction coefficient estimation means. Further, support control for a low road surface friction coefficient may be performed.

  The vehicle contact avoidance assistance control means is configured such that the second road friction coefficient estimated by the second road friction coefficient estimation means is larger than the first road friction coefficient estimated by the first road friction coefficient estimation means. Further, support control for a high road surface friction coefficient may be performed.

  When the assist control is automatic brake control that automatically applies a braking force to the left and right front wheels and the left and right rear wheels, the high road surface friction is determined by the braking force application characteristic for the low road surface friction coefficient. Compared with the braking force application characteristic for the coefficient, the application of the automatic braking force may be started when the contact margin value is large, and the maximum value of the automatic braking force may be small. Thereby, when the road surface friction coefficient is low, the vehicle can be decelerated while stabilizing the vehicle body by applying a small automatic braking force early. In addition, when the road surface friction coefficient is high, it is possible to avoid applying unnecessary braking force by applying automatic braking force later.

  When the second road surface friction coefficient is smaller than the first road surface friction coefficient, the support control for the high road surface friction coefficient is switched to the support control for the low road surface friction coefficient, and in the support control for the low road surface friction coefficient, The maximum value of the braking force application characteristic for the low road surface friction coefficient may be set according to the second road surface friction coefficient. As a result, it is possible to perform optimum deceleration without applying an unnecessary brake exceeding the deceleration that can be generated by the tire.

  When the second road surface friction coefficient is larger than the first road surface friction coefficient, the assist control for the low road surface friction coefficient is switched to the support control for the high road surface friction coefficient, and in the support control for the high road surface friction coefficient, The maximum value of the braking force application characteristic for the high road surface friction coefficient may be decreased. In the braking force application characteristic for the low road surface friction coefficient, automatic application of the braking force is started earlier than the braking force application characteristic for the high road surface friction coefficient. For this reason, when the support control for the low road surface friction coefficient is switched to the support control for the high road surface friction coefficient, an early braking force is already applied. Therefore, it is possible to sufficiently decelerate the vehicle even if the maximum value of the braking force application characteristic for the high road surface friction coefficient is reduced, and when the braking force application characteristic for the high road surface friction coefficient is used as it is. The driver's uncomfortable feeling due to the large braking force acting can be reduced.

  When the assist control is a steering assist control that automatically generates torque for the steering, the assist control for the low road surface friction coefficient has a lower torque than the assist control for the high road surface friction coefficient. May be given continuously.

  According to the present invention, the braking force is applied to the front wheels or the rear wheels before the vehicle is decelerated (the braking force is applied to decelerate the vehicle) by applying the braking force to the left and right front wheels and the left and right rear wheels. A road surface friction coefficient (first road surface friction coefficient) is estimated. This makes it possible to estimate the road surface friction coefficient while making it difficult for the driver to be aware of the deceleration of the vehicle due to the application of braking force. Further, during deceleration of the vehicle by applying braking force to the left and right front wheels and the left and right rear wheels, a road surface friction coefficient (second road surface friction coefficient) is estimated along with the deceleration. When the second road surface friction coefficient is different from the first road surface friction coefficient, the support control is performed based on the second road surface friction coefficient. For this reason, even if the road surface state (road surface friction coefficient) changes during vehicle deceleration accompanying the contact avoidance support control, the support control according to the change can be performed. Furthermore, during the contact avoidance assistance, the road surface friction coefficient (second road surface friction coefficient) is estimated based on the braking force applied to the left and right front wheels and the left and right rear wheels, so that the road surface friction coefficient can be estimated more accurately.

It is a typical block block diagram of the vehicle carrying the vehicle contact avoidance assistance device which concerns on one Embodiment of this invention. It is relative position explanatory drawing, such as a lateral distance detected by a radar. It is explanatory drawing which shows the braking force provision characteristic for low μ, and the braking force provision characteristic for high μ. It is explanatory drawing which shows the case where it switches from the braking force provision characteristic for low μ to the braking force provision characteristic for high μ. It is explanatory drawing which shows the case where it switches from the braking force provision characteristic for high μ to the braking force provision characteristic for low μ. It is a flowchart of the automatic brake control in the said embodiment. It is a flowchart of the deceleration assistance control in the said embodiment. It is a figure which shows the relationship between the deceleration of a vehicle and a 2nd road surface friction coefficient. It is a figure which shows the relationship between the steering amount in steering assist control, the variation | change_quantity per unit time, the steering assist torque for low μ, and the steering assist torque for high μ. It is explanatory drawing of the automatic brake control and steering assist control of the vehicle in which the vehicle contact avoidance assistance device was incorporated.

A. Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

1. Configuration of Vehicle 10 FIG. 1 is a schematic block diagram of a vehicle 10 (also referred to as “vehicle”) in which a vehicle contact avoidance support device 14 (hereinafter also referred to as “support device 14”) according to an embodiment of the present invention is incorporated. It is a block diagram.

  The support device 14 includes an ECU (electronic control unit) 20 having various functional units (various functional units) realized by the CPU executing a program stored in the memory. The ECU 20 performs VSA control as the functional unit. Part 94 and contact avoidance support control part 100 are provided.

  The VSA control unit 94 includes a reference yaw rate calculation unit 96 and a slip state determination unit 98.

  The contact avoidance support control unit 100 includes a steering assist control unit 90 and an automatic brake control unit 92.

  The vehicle 10 includes a front wheel 22 {right front wheel (FRW) 22R, left front wheel (FLW) 22L}, rear wheel 24 {right rear wheel (RRW) 24R, left rear wheel (RLW) 24L} (hereinafter, referred to as front wheel 22 and Together with the rear wheel 24, it is also referred to as “wheels 22, 24”.) Wheel speed sensors 61 to 64 are attached to the wheels 22 and 24, respectively, and the wheel speed Vw is taken into the ECU 20 from the wheel speed sensors 61 to 64. The ECU 20 constantly updates the average value of these four wheel speeds Vw as the vehicle speed Vs that is the speed of the vehicle 10.

  Each of the wheels 22 and 24 is provided with brake actuators 51 to 54 each constituted by a disc brake or the like that generates a braking force. Each braking force (braking hydraulic pressure) of the brake actuators 51 to 54 is independently controlled by four pressure regulators (not shown) in the hydraulic control device 44.

  The hydraulic control device 44 generates a braking hydraulic pressure corresponding to the depression amount θb of the brake pedal 40 detected by the depression amount sensor 42 and does not depend on the brake pedal 40 output from the automatic brake control unit 92 constituting the ECU 20. The four pressure regulators (not shown) generate braking hydraulic pressures according to the braking force command value Fb (so-called braking force command value by so-called brake-by-wire), and output it to the brake actuators 51 to 54. .

  When the depression amount θb is input from the depression amount sensor 42 and the braking force command value Fb is input from the automatic brake control unit 92 based on the depression operation of the brake pedal 40 by the driver, the hydraulic control device 44 The brake hydraulic pressure is generated in accordance with whichever is greater.

  Therefore, when the braking hydraulic pressure transmitted to each of the brake actuators 51 to 54 is controlled independently during braking, anti-lock brake control that suppresses locking of the wheels 22 and 24 can be performed.

  Further, the driving force is transmitted from the engine 34 through the transmission (T / M) 36 to the front wheels 22 (22R, 22L) among the four wheels 22, 24. The rear wheels 24 (24R, 24L) function as driven wheels that rotate as the vehicle 10 travels.

  The engine 34 has its rotational speed (engine rotational speed) controlled through a throttle actuator 32 that adjusts the throttle opening of a throttle valve 33 provided in the engine 34.

  The throttle opening of the throttle valve 33 is adjusted through the engine ECU 30 and the throttle actuator 32 according to the operation angle (accelerator angle, operation amount) θa of the accelerator pedal 26 detected by the operation amount sensor 28.

  The steering device 88 constituting the support device 14 basically includes a steering handle 70 (steering wheel) that is rotated (steered) by a driver, and a steering angle sensor that detects the steering angle θs of the steering handle 70. 72, a steering actuator 76 constituting a power steering device, and a steering mechanism 74 having a rack and pinion mechanism for steering the left and right front wheels 22.

  In this case, in the steering device 88, the rotation operation of the steering handle 70 by the driver is transmitted to the pinion constituting the steering mechanism 74 through the steering shaft and the connecting shaft, and the rack reciprocates due to the rotation of the pinion. The movement is transmitted to the front wheels 22 through the tie rods, so that the vehicle 10 is steered.

  When the steering of the vehicle 10 is executed, the steering angle θs associated with the rotation operation of the steering handle 70 by the driver is input to the steering actuator 76, so that the driving force of the steering actuator 76, that is, steering is performed. A steering assist force depending on the operation of the handle 70 is transmitted to the front wheels 22 through the rack of the steering mechanism 74.

  On the other hand, a steering assist command value Fs (herein referred to as a steer-by-wire steering assist command value, also referred to as an avoidance steering assist command value) output from a steering assist control unit 90 constituting the ECU 20 is input to the steering actuator 76. Thus, a steering assist torque TQ (steer torque) corresponding to the steering assist command value Fs is output to the steering mechanism 74. Note that a change in gear ratio or the like may be commanded instead of the steering assist command value Fs. Note that the steering assist is not limited to processing by steer-by-wire, and may be processing for changing the gear ratio of the steering mechanism 74 and processing for changing the assist value of the electric power steering device (EPS device).

  The steering mechanism 74 outputs a steering assist force corresponding to the steering assist torque TQ corresponding to the steering assist command value Fs to the front wheels 22, so that the front wheels 22 rotate the front wheels 22 by the amount of steering corresponding to the steering assist force. It can be steered.

  The steering assist command value Fs is basically generated so as to assist the driver with the turning operation of the steering handle 70 when trying to avoid contact with an obstacle ahead of the vehicle 10. To do.

  In the present embodiment, the steering assist torque TQ that is additionally generated in the steering direction is used, but the steering assist torque TQ that acts as a reaction force against the steering handle 70 is used. May be. In this case, the steering assist torque TQ (reaction force) in the direction to be steered is reduced, and the steering assist torque TQ (reaction force) in the direction not to be steered is increased to assist the operation of the steering handle 70. To do.

  The support device 14 further includes a yaw rate sensor 82 that detects a yaw rate Yr generated in the vehicle 10 (rotational force around the central axis when the vehicle 10 is viewed from directly above), and is generated in the vehicle 10. A lateral G sensor 84 that detects lateral G (lateral acceleration) and a longitudinal G sensor 85 that detects longitudinal G (longitudinal acceleration) generated in the vehicle 10 are provided.

  Further, the support device 14 is provided with an alarm device 86 that generates an alarm, and generates an alarm that prompts the driver to depress the brake pedal 40 (brake operation) and rotate the steering handle 70 (steering operation). To do. The alarm for the driver is generated using alarm means such as a lamp, chime, buzzer, speaker, etc. of the alarm device 86. Although an alarm may be generated by the alarm device 86, a reaction force is applied to the steering handle 70 and a reaction force is applied to the accelerator pedal 26 with or without an alarm from the alarm device 86. An alarm can also be generated by applying or applying a reaction force to the brake pedal 40.

  Further, the support device 14 is provided with a radar 80 in the front grill portion or the like. The radar 80 transmits an electromagnetic wave such as a millimeter wave toward the front of the vehicle 10 as a transmission wave, detects the size of an obstacle (for example, a preceding vehicle, etc.) based on the reflected wave, and the obstacle vehicle. The direction from 10 (own vehicle) is detected, and at the same time, the relative distance L between the obstacle and the own vehicle (inter-vehicle distance if the obstacle is a vehicle), the relative speed Vr between the obstacle and the own vehicle. It operates as a relative position detecting means for detecting the like. Note that a laser radar, a stereo camera, or the like can be employed instead of the millimeter wave radar as a relative position detecting means for detecting a relative position with respect to an obstacle.

  The contents such as the relative position detected by the radar 80 will be described with reference to FIG.

  As is well known, the radar 80 and the ECU 20 connected to the radar 80 first have a relative distance from the vehicle 10 (the own vehicle, depicted in two places with different positions in FIG. 2) to the vehicle 12 ahead. L can be detected. Further, the radar 80 and the ECU 20 can detect the vehicle width Wo of the vehicle 12 ahead. Note that the vehicle width Wm of the host vehicle 10 is stored in advance in a memory (storage unit) in the ECU 20 and the radar 80. Next, the radar 80 and the ECU 20 can detect the relative speed Vr of the vehicle 10 with respect to the vehicle 12. Further, the ECU 20 can calculate a contact margin time TTC (Time To Contact) as a contact margin value from the relative distance L and the relative speed Vr from the vehicle 10 to the preceding vehicle 12 as TTC = L / Vr. . The contact margin value is a parameter for determining the possibility of contact between the obstacle ahead of the host vehicle and the host vehicle. The larger the contact margin value, the lower the possibility of contact. The smaller the setting, the higher the possibility of contact. As the contact margin value, an inter-vehicle distance or the like can be used in addition to the contact margin time TTC.

In this case, the ECU 20 determines, for example, the vehicle 10 based on the vehicle width Wm of the vehicle 10 (own vehicle) itself, the vehicle width Wo of the vehicle 12 ahead detected by the radar 80, and a predetermined margin width α (margin lateral distance). The target lateral avoidance distance Dt required when 10 (the host vehicle) avoids contact with the vehicle 12 ahead and overtakes it is calculated by the following equation (1).
Dt = (Wo / 2) + αα + 10 (Wm / 2) (1)

  The lateral avoidance distance (referred to as lateral distance or offset) Do increases in order for the vehicle 10 (own vehicle) to overtake by avoiding contact with the forward vehicle 12, and the forward vehicle on the own vehicle center axis 10c. This is a case where the other vehicle center axis 12c overlaps, that is, a vehicle 12 ahead is present in front of the vehicle 10 (own vehicle).

  Even when the vehicle 12 ahead is present in front of the vehicle 10 (own vehicle), when the vehicle 10 catches up with another vehicle 12 traveling on the same route on the road 200, the vehicle 10 If the vehicle 10 moves in the vehicle width direction (lateral direction) by the above-mentioned target lateral avoidance distance Dt when passing the side of the vehicle 12 ahead of the vehicle by changing the course and exiting ahead of the vehicle 12, It is possible to pass through the side of the vehicle 12 ahead, leaving a lateral distance corresponding to the margin width α. The distance (deviation) in the vehicle width direction between the host vehicle central axis 10c and the other vehicle central axis 12c of the vehicle 12 ahead is also referred to as an offset (offset amount) Do as described above.

2. Various Controls The vehicle 10 incorporating the support device 14 according to an embodiment of the present invention is basically configured as described above. Next, various controls will be described. In the present embodiment, vehicle posture stabilization control by the VSA control unit 94, contact avoidance automatic brake control by the automatic brake control unit 92, and contact avoidance steering assist control (steering assist control) by the steering assist control unit 90 are performed.

(1) Vehicle posture stabilization control The VSA control unit 94 determines that the slip state Slc of the vehicle 10 is larger than the threshold value Slcth and the vehicle 10 is in a turning state, and there is a certain difference between the reference yaw rate Ys and the actual yaw rate Yr. It is configured to operate.

  Here, when the slip state Slc is detected, the slip between the road surface and the wheels 22 and 24 with respect to the rear wheels 24 (24R and 24L) from the slip state determination unit 98 of the VSA control unit 94 through the automatic brake control unit 92. A slip state determination braking force command value Fbs for determining the state Slc is output for a predetermined time of ms order.

  Based on the longitudinal force of the left and right rear wheels 24 and the support load of the left and right rear wheels 24 at this time, as shown in Patent Document 1, the road surface friction coefficient μ for the left and right rear wheels 24 is obtained. When the road surface friction coefficient μ is larger than a predetermined friction coefficient threshold value μth, it is determined that the slip state Slc is smaller than the threshold value Slcth (when the road surface friction coefficient μ is large, the slip surface is difficult to slip because the road surface is difficult to slip). Is judged to be small.)

  Note that the slip state Slc may be obtained as a road surface friction coefficient μ for the left and right front wheels 22, and further, the same output as the vehicle speed Vs when the output of the slip state determination braking force command value Fbs is started. The difference or ratio of the vehicle speed Vs at the time when the vehicle speed Vs is finished is obtained on the road having a known different road surface friction coefficient μ in advance, and the vehicle speed Vs when the output of the slip state determination braking force command value Fbs is started and the output It can also be determined by comparing with the difference or ratio of the vehicle speed Vs when the operation is finished.

  When it is determined that the slip state Slc is greater than the threshold value Slcth (the road surface is slippery) and the vehicle 10 is turning, the VSA controller 94 determines how much the driver is going to turn from the steering angle θs and the vehicle speed Vs. The reference yaw rate Ys shown is calculated by the reference yaw rate calculation unit 96 based on the vehicle motion model and the like. The reference yaw rate Ys is set as a target value and compared with the actual yaw rate Yr detected by the yaw rate sensor 82 in real time.

  When the actual yaw rate Yr is larger than the reference yaw rate Ys (Yr> Ys), it is determined that there is a possibility of oversteering, in other words, there is a possibility that the vehicle will spin too much due to a sudden handle or the like. Automatic braking is applied to the inner and outer wheels to generate outward force. For example, when the vehicle is turning left, the right front wheel 22R is braked via the automatic brake control unit 92 via the brake actuator 51, and a force in the right turning direction is generated.

  On the other hand, if the actual yaw rate Yr is smaller than the reference yaw rate Ys (Yr <Ys), it may be understeered. In other words, it may be determined that there is a possibility that the vehicle cannot bend completely on a curved road or the like and swell outside. In addition, the throttle opening of the throttle valve 33 is reduced through the throttle actuator 32 to suppress the engine output, and an inward force for bending the vehicle 10 is generated by braking the inner wheel in the rear wheel 24 as necessary. For example, when the vehicle is turning left, the left rear wheel 24L is braked via the automatic brake control unit 92 via the brake actuator 51 to generate a force in the left turning direction.

  As described above, if the braking hydraulic pressure transmitted to the brake actuators 51 to 54 when the vehicle 10 turns is controlled independently under the control of the VSA control unit 94, the difference between the braking forces of the left and right wheels 22L, 24L, 22R, 24R. The yaw moment of the vehicle 10 is arbitrarily controlled to avoid the occurrence of understeer during turning, the occurrence of oversteer and spin, and the behavior of the vehicle 10 can be stabilized.

(2) Automatic brake control The automatic brake control is a control that performs automatic braking (deceleration support) when a contact margin value with respect to an obstacle ahead of the vehicle 10 becomes a predetermined value or less.

  The automatic brake control unit 92 determines whether or not automatic braking (deceleration support) is necessary based on a contact margin time TTC (TTC = L / Vr) as a contact margin value for an obstacle ahead of the vehicle 10. You may judge based on the relative distance L with the obstacle (a front vehicle is also included) ahead of the vehicle 10. FIG.

  In this case, the threshold of the contact allowance time TTC is, for example, a constant time (a time of about 1 [s] to 3 [s]) regardless of the vehicle speed Vs, but the threshold of the relative distance L is the vehicle speed. The smaller the Vs, the smaller the distance (short distance, around 70 [m] to 30 [m]) is set as the threshold. Of course, the threshold of the contact allowance time TTC may be changed depending on the vehicle speed Vs, the steering state of the steering handle 70 by the driver, and the like.

  The smaller the contact allowance time TTC is, the greater the possibility of contact with the obstacle. Therefore, when the contact allowance time TTC is smaller than a predetermined threshold value (predetermined value TH1 to be described later), the vehicle 10 and the obstacle are contacted. In order to avoid this, automatic braking (deceleration support control) is performed.

  Specifically, the automatic brake control unit 92 applies a braking force command value Fb that applies an appropriate braking force to the brake actuators 51 to 54 in order to generate the deceleration D necessary for relaxing the contact margin time TTC. Is calculated and output to the hydraulic control device 44. As a result, a braking hydraulic pressure corresponding to the braking force command value Fb is generated by the hydraulic control device 44, and the braking force is applied to the wheels 22 and 24 through the brake actuators 51 to 54 by the generated braking hydraulic pressure.

  When the automatic brake control unit 92 determines that the accelerator pedal 26 is depressed from the operation amount θa of the accelerator pedal 26, the automatic brake control unit 92 simultaneously controls the throttle actuator 32 and operates the throttle valve 33 in the closing direction by a predetermined amount. (Throttle-by-wire) may be used (see the dotted arrow line from the ECU 20 to the throttle actuator 32 in FIG. 1).

  In this embodiment, the braking force characteristic (braking force applying characteristic) applied by the automatic brake control unit 92 is used for a low road surface friction coefficient (hereinafter also referred to as “low μ”) and a high road surface friction coefficient (hereinafter referred to as “high”). μ ”). That is, as shown in FIG. 3, depending on the road surface friction coefficient μ, a low μ braking force application characteristic Clow (hereinafter also referred to as “characteristic Clow”) or a high μ braking force application characteristic High (hereinafter “characteristic”). Also referred to as “Chich”).

  As shown in FIG. 3, the characteristic Clow for low μ has a target deceleration Dtgt [target braking force target value Dtgt [when the contact margin time TTC is relatively large (the contact margin time TTC is equal to or less than a predetermined value TH1). G] is increased, and the brake actuators 51 to 54 are operated to apply braking force to the wheels 22R, 22L, 24R, and 24L. On the other hand, the characteristic High for High μ increases the target deceleration Dtgt and activates the brake actuators 51 to 54 when the contact margin time TTC is relatively small (the contact margin time TTC is equal to or less than the predetermined value TH2). The braking force is applied to the wheels 22R, 22L, 24R, 24L.

  In the characteristic Clow for low μ, the contact allowance time TTC decreases from the predetermined value TH1 (toward the left side in FIG. 3), and once the target deceleration Dtgt starts to increase, it temporarily increases to its maximum value Dlmax. Thereafter, the target deceleration Dtgt is gradually decreased and lowered to a predetermined value Dll. On the other hand, in the characteristic High for High, the contact margin time TTC becomes shorter (toward the left side in FIG. 3), and when the target deceleration Dtgt starts to increase from the predetermined value TH2, it increases to its maximum value Dhmax. Maintains the maximum value Dhmax.

  Note that, as shown in FIG. 3, the low μ characteristic Clow generates a braking force with a longer contact margin time TTC than the high μ characteristic High. Further, the maximum value Dhmax for high μ is higher than the maximum value Dlmax for low μ. Further, until the contact margin time TTC reaches the predetermined value TH3, the low μ braking force application characteristic Clow has a larger target deceleration Dtgt than the high μ braking force application characteristic High, but the contact margin time TTC is larger. Both target decelerations Dtgt are equal at a predetermined value TH3. When the contact margin time TTC becomes shorter than the predetermined value TH3, the target deceleration Dtgt of the high μ braking force application characteristic High becomes larger than the low μ braking force application characteristic Clow. This is because a road surface with a high μ can be decelerated more rapidly with a larger deceleration (easily decelerated) than a road surface with a low μ.

  In this embodiment, before the automatic braking (deceleration support control), the braking force is applied to the left and right rear wheels 24 to estimate the road surface friction coefficient μ (first road surface friction coefficient μ1). That is, the first road surface friction coefficient μ1 is estimated when the contact margin time TTC reaches the predetermined value TH0. The application of the braking force here is for the purpose of estimating the first road surface friction coefficient μ1, and is not intended for the deceleration of the vehicle 10. As the first road surface friction coefficient μ1, there are two, a low μ and a high μ, but they may be divided into finer sections. Further, the first road surface friction coefficient μ1 may be estimated by applying a braking force to the left and right front wheels 22 instead of the left and right rear wheels 24.

  Thereafter, when the contact allowance time TTC becomes equal to or less than the predetermined value TH1 (in the case of low μ) or equal to or less than the predetermined value TH2 (in the case of high μ), the automatic brake control unit 92 sets all four wheels ( A braking force is applied to the left and right front wheels 22 and the left and right rear wheels 24). Meanwhile, the road surface friction coefficient μ (second road surface friction coefficient μ2) is continuously estimated based on the braking force applied to the wheels 22 and 24. Similar to the first road surface friction coefficient μ1, the second road surface friction coefficient μ2 is also divided into two, low μ and high μ, but may be divided into finer sections.

  When the first road friction coefficient μ1 related to the left and right rear wheels 24 and the second road friction coefficient μ2 related to the wheels 22 and 24 are different, the automatic brake control unit 92 controls according to the second road surface friction coefficient μ2. Switch the power application characteristics. In addition, after switching to the braking force application characteristic according to the second road surface friction coefficient μ2, if the new second road surface friction coefficient μ2 is different from the previous second road surface friction coefficient μ2, the new second road surface friction coefficient μ2 Switching to the braking force application characteristic according to

  In FIG. 4, when the first road surface friction coefficient μ1 is low μ and the subsequent second road surface friction coefficient μ2 is high μ, the braking force application characteristic Clow for low μ (solid line in FIG. 4) is shown. An example of a state of switching to a braking force imparting characteristic High for high μ (dotted line in FIG. 4) is shown.

  As shown in FIG. 4, when the characteristic Clow for low μ is switched to the characteristic High for high μ, the maximum value Dhmax of the characteristic High for High μ is also referred to as “maximum value Dhmax (new)” for convenience. ) Is set lower than the maximum value Dhmax in FIG. 3 (also referred to as “maximum value Dhmax (old)” for convenience). That is, unlike FIG. 3, the high μ characteristic “Chi” in FIG. 4 does not use the dotted line portion, and the contact margin time TTC is equal to or less than the predetermined value TH3 and reaches the maximum value Dhmax (new). This is due to the following reason. That is, when the contact margin time TTC at the time of switching from the low μ characteristic Clow to the high μ characteristic High is equal to or less than the predetermined value TH3, the contact margin time TTC has been between the predetermined value TH1 and TH3 until then. In the meantime, the characteristic Clow for low μ is used. When the contact margin time TTC is between the predetermined values TH1 and TH3, the target deceleration Dtgt is set higher for the low μ characteristic Clow than for the high μ characteristic High. Then, when the contact margin time TTC is from the predetermined value TH1 to TH3, the braking force is applied accordingly. In other words, if only the characteristic High for High μ was used, the target deceleration Dtgt had to be increased to the maximum value Dhmax (old), but it was only maintained at the maximum value Dhmax (new). The vehicle 10 can be sufficiently decelerated.

  In FIG. 5, when the first road surface friction coefficient μ1 is high and the subsequent second road surface friction coefficient μ2 is low μ, the braking force application characteristic High for high μ (dotted line in FIG. 5). Shows an example in which is switched to a low μ braking force application characteristic Clow (solid line in FIG. 5).

  As shown in FIG. 5, when the high μ characteristic Chigh is switched to the low μ characteristic Clow, the maximum value Dlmax of the low μ characteristic Crow (also referred to as “maximum value Dlmax (new)” for convenience). ) Can be set lower than the maximum value Dlmax (also referred to as “maximum value Dlmax (old)” for convenience) in FIGS. 3 and 4 according to the value of the second road surface friction coefficient μ2. Optimum deceleration can be achieved by limiting the deceleration D that can be generated by the tire to the estimated road surface with the second friction coefficient μ2 {in this case, the maximum value Dlmax (new)}. Further, as will be described later, this is also because hysteresis characteristics are provided in the determination switching (high μ⇔low μ) of the second road surface friction coefficient μ2.

  FIG. 6 is a flowchart of automatic brake control according to this embodiment. In step S1, the automatic brake control unit 92 determines the contact allowance time TTC. In step S2, the automatic brake control unit 92 determines whether the contact allowance time TTC is equal to or less than a predetermined value TH0. If the contact allowance time TTC is not less than or equal to the predetermined value TH0 (S2: NO), the process returns to step S1. When the contact margin time TTC is equal to or less than the predetermined value TH0 (S2: YES), in step S3, the automatic brake control unit 92 determines the first road surface friction coefficient based on the deceleration D associated with the braking force applied to the left and right rear wheels 24. Estimate μ1. As the first road surface friction coefficient μ1, for example, the road surface friction coefficient μ estimated by the slip state determination unit 98 may be used, or the automatic brake control unit 92 may estimate the road surface friction coefficient μ independently. Further, as described above, the first road surface friction coefficient μ1 may be estimated by applying a braking force to the left and right front wheels 22 instead of the left and right rear wheels 24. In subsequent step S4, the automatic brake control unit 92 performs the deceleration support control for assisting the deceleration of the vehicle 10 according to the road surface friction coefficient μ.

  FIG. 7 is a flowchart showing details of the deceleration support control. In step S11, the automatic brake control unit 92 determines the contact allowance time TTC. When the process of FIG. 7 is the first, step S11 may be omitted by using the determination result of step S1 of FIG.

  In step S12, the automatic brake control unit 92 determines whether the contact allowance time TTC is equal to or less than a predetermined value TH1. If the contact allowance time TTC is not less than or equal to the predetermined value TH1 (S12: NO), it is determined that the vehicle 10 does not need to be decelerated, and the current step S4 is terminated. When the contact allowance time TTC is equal to or shorter than the predetermined value TH1 (S12: YES), the process proceeds to step S13.

  In step S13, the automatic brake control unit 92 determines whether the contact allowance time TTC is equal to or less than a predetermined value TH3. When the contact allowance time TTC is equal to or less than the predetermined value TH3 (S13: YES), the process proceeds to step S15. When the contact allowance time TTC is not less than or equal to the predetermined value TH3 (S13: NO), in step S14, the automatic brake control unit 92 determines whether or not the anti-lock brake control is being executed {ABS (Anti-lock Brake System) Determine if the function is active. When the ABS function is in operation (S14: YES), it can be determined that the brake pedal 40 is depressed so that automatic braking force does not need to be applied. Therefore, in this case, the process proceeds to step S16 without applying automatic braking force (S15). When the ABS function is not in operation (S14: NO), the process proceeds to step S15.

  In step S15, the automatic brake control unit 92 applies a braking force to all four wheels (each of the left and right front wheels 22 and the left and right rear wheels 24). The braking force to be applied uses the braking force imparting characteristic High for high μ or the braking force imparting characteristic Clow for low μ depending on whether the first road surface friction coefficient μ1 is low μ or high μ, and the current contact margin time A braking force according to TTC is applied to all the wheels 22, 24.

  In step S <b> 16, the automatic brake control unit 92 calculates the deceleration D of the vehicle 10. As the deceleration D, the longitudinal G (deceleration G) detected by the longitudinal G sensor 85 can be used.

  In step S17, the automatic brake control unit 92 estimates the second road surface friction coefficient μ2 based on the deceleration D determined in step S16. The second road surface friction coefficient μ2 is estimated using the characteristics shown in FIG.

  FIG. 8 shows a reference estimation characteristic Cr, a first estimation characteristic Cl, a second estimation characteristic C2, and a road surface condition determination threshold THμ. The reference estimation characteristic Cr is a determination characteristic serving as a reference for estimating the second road surface friction coefficient μ2 based on the deceleration D, but is not actually used in the present embodiment. The first estimation characteristic C1 is a characteristic for estimating the second road surface friction coefficient μ2 based on the deceleration D when the current determination is high μ. The second estimation characteristic C2 is a characteristic for estimating the second road surface friction coefficient μ2 based on the deceleration D when the current determination is low μ. The road surface condition determination threshold value THμ (hereinafter also referred to as “threshold value THμ”) (for example, 0.4) is a threshold value for determining whether the second road surface friction coefficient μ2 is high μ or low μ. In FIG. 8, when the threshold value is equal to or higher than THμ, it is determined as high μ, and when it is lower than the threshold value THμ, it is determined as low μ.

  In step S18 of FIG. 7, the automatic brake control unit 92 determines the state of the second road surface friction coefficient μ2. As shown in FIG. 8, according to the reference estimation characteristic Cr, when the deceleration D is a predetermined value THr (for example, 0.4) or more, the road surface state is high μ, and when the deceleration D is less than the predetermined value THr. The road surface condition is low μ. Basically, the second road surface frictional resistance μ2 and the deceleration D that can be generated are the same.

  When the current determination is high μ and the deceleration D is less than a predetermined value THa (for example, 0.3) in the state where the first estimated characteristic C1 is used, in step S19, the automatic brake controller 92 determines whether the ABS function Determine if is in operation. When the ABS function is in operation (S19: YES), in step S20, the automatic brake control unit 92 switches the determination to low μ. When the ABS function is not operating (S19: NO), in step S21, the automatic brake control unit 92 keeps the determination at a high μ and maintains the current braking force application characteristics. In this way, when changing from high μ to low μ, it is determined in step S19 whether or not the ABS function is operating, and switching to low μ is performed only when the ABS function is operating. This is for avoiding erroneous determination of low μ during slow deceleration at high μ (predetermined value THa or less).

  In step S18, when the current determination is high μ and the deceleration D is equal to or greater than the predetermined value THa in the state where the first estimation characteristic C1 is used, in step S21, the automatic brake control unit 92 determines that the determination is high μ. Leave.

  In step S18, when the current determination is low μ and the deceleration D is equal to or greater than a predetermined value THb (for example, 0.5) in a state where the second estimated characteristic C2 is used, automatic brake control is performed in step S22. The unit 92 switches the determination to high μ, and when the deceleration D is less than the predetermined value THb, in step S21, the automatic brake control unit 92 keeps the determination at low μ. Therefore, by using the first estimation characteristic C1 and the second estimation characteristic C2, switching of determination is less likely to occur than when the reference estimation characteristic Cr is used. In other words, in the present embodiment, a hysteresis characteristic is provided for determination switching between high μ and low μ.

  Returning to FIG. 6, in step S5, the automatic brake control unit 92 determines whether or not the contact allowance time TTC is equal to or less than the predetermined value TH1. When the contact margin time TTC is equal to or less than the predetermined value TH1, the process returns to step S4 in order to continue the deceleration support control. If the contact allowance time TTC is not less than or equal to the predetermined value TH1 (S5: NO), the vehicle 10 is considered to be sufficiently away from the obstacle (such as the vehicle 12), so the deceleration support control is terminated and the current process is terminated.

(3) Steering assist control In addition to the contact margin time TTC, the steering assist control unit 90 is a midpoint obtained from the steering angle sensor 72 (steering angle θ when the vehicle 10 is considered to travel linearly for a predetermined time). Is determined in consideration of the steering angle θs from the steering angle θ, the steering angular velocity dθs / dt obtained by time differentiation of the steering angle θs, the lateral G detected by the lateral G sensor 84, and the yaw rate (actual yaw rate) Yr detected by the yaw rate sensor 82. Is done. That is, with the steering angle θs, the steering angular velocity dθs / dt, the lateral G, the yaw rate Yr, etc. as variables, the driver's avoidance operation situation SE is a predetermined function SE = SE (θs, dθs / dt, lateral G , Yr), and when it is determined that this value is a value that requires the avoidance assist operation (threshold value Thse) or a value that is lower than this, the avoidance steering assist control is activated.

  In this case, the reference yaw rate Ys calculated according to the steering angle θs and the vehicle speed Vs is changed to the assist yaw rate Ya by the steering assist control unit 90.

  When calculating the assist yaw rate Ya, the difference between the above-described target lateral avoidance distance Dt and the lateral distance D (the amount of deviation between the vehicle center axis 10c and the other vehicle center axis 12c) is multiplied by a predetermined gain to assist. Calculate the lateral acceleration. Further, the assist yaw rate Ya is calculated by dividing the assist lateral acceleration by the vehicle speed Vs.

  The steering assist control unit 90 outputs to the steering actuator 76 an avoidance steering assist command value Fse that generates the assist yaw rate Ya calculated in this way.

  As a result, a steering assist torque corresponding to the avoidance steering assist command value Fse is applied from the steering actuator 76 to the steering mechanism 74, whereby the turning behavior of the vehicle 10 is controlled and assisted by the assist yaw rate Ya.

  FIG. 9 shows the steering angle θs and the change amount Δθs per unit time, the steering assist torque TQ when the road surface is low μ (hereinafter also referred to as “assist torque TQl”), and the steering when the road surface is high μ. The relationship with the assist torque (hereinafter also referred to as “assist torque TQh”) is shown.

  As shown in FIG. 9, the assist torque TQl for low μ is continuously generated at a relatively low value, whereas the assist torque TQ for high μ is instantaneously generated at a relatively high value. Generated. More specifically, the assist torque TQl is a function {TQl = F1 (θs, Δθs)} of the steering angle θs and the change amount Δθs, whereas the assist torque TQh is a function {TQh = F2 of the change amount Δθs. (Δθs)}. This is to prevent the vehicle 10 from slipping when the steering angle θs is excessively increased when the road surface friction coefficient μ is low, and when the steering angle θs is increased when the road surface friction coefficient μ is high, Since the vehicle 10 can be steered without slipping, it is considered to improve the initial difficulty of turning by the steering actuator 76 with the assistance only when the steering handle 70 is started.

  As described above, an example of the operation condition of the vehicle posture stabilization control by the VSA control unit 94, an example of the operation condition of the contact avoidance automatic brake control by the automatic brake control unit 92, and the contact avoidance steering assist control by the steering assist control unit 90 ( Although an example of the operating condition of the avoidance steering assist control has been described, the steering assist control unit 90 performs steering by controlling the steering angle of the front wheels 22 that are the steering wheels through the steering actuator 76 and the steering mechanism 74. The VSA control unit 94 controls the spin due to oversteer and the bulge due to understeer by generating a yaw moment in the reverse direction. As a result, the VSA control unit 94 controls steering and braking. Therefore, in practice, the automatic brake control unit 92, The steering assist control unit 90 and the VSA control unit 94 may operate simultaneously.

(4) Application Example of Automatic Brake Control and Steering Assist Control FIG. 10 shows an example of a scene where the automatic brake control and steering assist control of the present embodiment are applied. When the contact allowance time TTC between the vehicle (own vehicle) 10 and the stopped vehicle (other vehicle) 12 reaches a predetermined value TH0 at time t1, the automatic brake control unit 92 applies braking force to the left and right rear wheels 24. Is used to estimate the first road surface friction coefficient μ1. Note that the first road surface friction coefficient μ1 may be estimated based on the braking force applied to the left and right front wheels 22.

  When the contact margin time TTC reaches the predetermined value TH1 at time t2, the automatic brake control unit 92 starts automatic braking (deceleration support control). Then, the second road surface friction coefficient μ2 is continuously estimated based on the braking force (front and rear G) for all the wheels (left and right front wheels 22, left and right rear wheels 24). As a result, when the determination of the second road surface friction coefficient μ2 is different from the determination of the first road surface friction coefficient μ1, the braking force application characteristic is switched according to the determination of the second road surface friction coefficient μ2.

  When the steering handle 70 of the host vehicle 10 is steered at the time point t3, the steering assist control unit 90 responds to the road surface friction coefficient μ (the first road surface friction coefficient μ1 or the second road surface friction coefficient μ2) at the time point t3. Start steering assist control. Thereafter, automatic braking control and steering assist control are performed until the steering of the steering handle 70 of the host vehicle 10 is completed at time t4.

3. As described above, according to this embodiment, the first road surface friction is applied by applying a braking force to the left and right rear wheels 24 (or the left and right front wheels 22) prior to the deceleration assist control. The coefficient μ1 is estimated. As a result, the first road surface friction coefficient μ1 can be estimated while making it difficult for the driver to be aware of the deceleration of the vehicle 10 due to the application of the braking force. During the deceleration support control, the second road surface friction coefficient μ2 is estimated as the vehicle 10 is decelerated. When the second road surface friction coefficient μ2 is different from the first road surface friction coefficient μ1, deceleration support control is performed based on the second road surface friction coefficient μ2. For this reason, even if the road surface state (road surface friction coefficient μ) changes during the deceleration support control, the deceleration support control corresponding to the change can be performed. Furthermore, during the deceleration assist control, the second road surface friction coefficient μ2 is estimated with the braking force applied to the four wheels 22R, 22L, 24R, and 24L. Therefore, the second road surface friction coefficient μ2 can be estimated with higher accuracy.

  In the automatic brake control of this embodiment, the braking force application characteristic Clow for low μ is automatically applied with braking force when the contact allowance time TTC is larger than the braking force application characteristic High for high μ. At the same time, the automatic braking force maximum value Dlmax is reduced. Thus, when the road surface friction coefficient μ is low, the vehicle 10 can be decelerated while stabilizing the vehicle body by applying a small automatic braking force early. In addition, when the road surface friction coefficient μ (first road surface friction coefficient μ1 or second road surface friction coefficient μ2) used as the determination result is high, the automatic braking force is applied later, thereby applying unnecessary braking force. Can be avoided.

  In the automatic brake control of the present embodiment, when the second road surface friction coefficient μ2 is smaller than the first road surface friction coefficient μ1, the high μ deceleration support control is switched to the low μ deceleration support control, and the low μ deceleration is performed. In the assist control, the maximum value Dlmax of the braking force application characteristic Clow for low μ is decreased (FIG. 5). As a result, the optimum deceleration according to the road surface friction coefficient μ is possible.

  In the automatic brake control according to the present embodiment, when the second road surface friction coefficient μ2 is larger than the first road surface friction coefficient μ1, the low-μ deceleration support control is switched to the high μ deceleration support control, and the high μ deceleration is performed. In the assist control, the maximum value Dhmax of the braking force application characteristic High for high μ is decreased (FIG. 4). In the low μ braking force application characteristic Clow, automatic braking force application is started earlier than the high μ braking force application characteristic High. For this reason, when switching from the deceleration support control for low μ to the deceleration support control for high μ, an earlier braking force is already applied. Therefore, the vehicle 10 can be sufficiently decelerated even if the maximum value Dhmax of the braking force imparting characteristic High for High μ is decreased, and the braking force imparting characteristic High for High μ is used as it is. The driver's uncomfortable feeling due to the large braking force acting can be reduced.

B. Modifications It should be noted that the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be adopted based on the contents described in this specification. For example, the following configuration can be adopted.

  In the above embodiment, the contact margin time TTC is used as the contact margin value. However, the present invention is not limited to this. For example, the relative distance L between the host vehicle 10 and the other vehicle 12 (obstacle) may be used as the contact margin value. .

  In the above embodiment, the contact margin time TTC between the host vehicle 10 and the other vehicle 12 (obstacle) is determined based on the output of the radar 80. However, the present invention is not limited to this. For example, the output from the image sensor is used. May be determined.

  In the above embodiment, the vehicle 10 is a four-wheeled vehicle, but is not limited thereto, and may be a two-wheeled vehicle, a truck, a bus, or the like.

  In the above embodiment, the switching determination of the road surface friction coefficient μ is performed in the automatic brake control and the steering assist control. However, the present invention is not limited to this. For example, in the vehicle attitude stabilization control or the anti-skid control in Patent Document 2, Such switching determination may be performed.

10 ... Vehicle (own vehicle) 12 ... Vehicle as an obstacle (other vehicle)
14 ... Vehicle contact avoidance support device 20 ... ECU (first road surface friction coefficient estimation means, second road surface friction coefficient estimation means, contact margin value calculation means, vehicle contact avoidance support control means)
DESCRIPTION OF SYMBOLS 22 ... Front wheel 24 ... Rear wheel 80 ... Radar (relative position detection means) 90 ... Steering assist control unit 92 ... Automatic brake control unit 94 ... VSA control unit 96 ... Reference yaw rate calculation unit 98 ... Slip state determination unit 100 ... Contact avoidance support Control unit High ... braking force imparting characteristic for high μ Clow ... braking force imparting characteristic for low μ D ... Deceleration Dhmax ... maximum value for high μ Dlmax ... maximum value TQh for low μ ... steering assist for high μ Torque TQl ... Steering assist torque TTC for low μ ... Contact margin time μ1 ... First road surface friction coefficient μ2 ... Second road surface friction coefficient

Claims (8)

A vehicle contact avoidance assisting device that assists in avoiding contact with the obstacle according to the positional relationship between the obstacle ahead of the vehicle and the vehicle,
Prior to deceleration of the vehicle by applying braking force to left and right front wheels and left and right rear wheels, a first road surface friction coefficient is estimated by applying braking force to the left and right front wheels or left and right rear wheels. First road surface friction coefficient estimating means;
A relative position detecting means for detecting a relative position between the vehicle and the obstacle;
Contact margin value calculating means for calculating a contact margin value between the vehicle and the obstacle based on a relative position with the obstacle ahead of the vehicle detected by the relative position detecting means;
Vehicle contact avoidance support control means for performing contact avoidance support control with the obstacle based on the first road surface friction coefficient when the contact margin value is a predetermined value or less;
A second road surface friction coefficient is estimated based on the braking force applied to the left and right front wheels and the left and right rear wheels during deceleration of the vehicle by applying braking force to the left and right front wheels and the left and right rear wheels. Two road surface friction coefficient estimating means,
The vehicle contact avoidance support control means performs the contact avoidance support control based on the second road surface friction coefficient when the first road surface friction coefficient and the second road surface friction coefficient are different. Avoidance support device. In the vehicle contact avoidance assistance device according to claim 1,
The second road surface friction coefficient estimating means is based on a deceleration of the vehicle generated by a braking force applied to the left and right front wheels and the left and right rear wheels generated during the assistance control by the vehicle contact avoidance assistance control means. 2. A vehicle contact avoidance assisting device that estimates a road surface friction coefficient. In the vehicle contact avoidance assistance device according to claim 1 or 2,
The vehicle contact avoidance assistance control means is configured such that the second road friction coefficient estimated by the second road friction coefficient estimation means is smaller than the first road friction coefficient estimated by the first road friction coefficient estimation means. A vehicle contact avoidance assisting device that performs assist control for a low road surface friction coefficient. In the vehicle contact avoidance assistance device according to any one of claims 1 to 3,
The vehicle contact avoidance assistance control means is configured such that the second road friction coefficient estimated by the second road friction coefficient estimation means is larger than the first road friction coefficient estimated by the first road friction coefficient estimation means. A vehicle contact avoidance assist device that performs assist control for a high road surface friction coefficient. In the vehicle contact avoidance assistance device according to claim 4, which is dependent on claim 3,
The assist control is an automatic brake control that automatically applies a braking force to the left and right front wheels and the left and right rear wheels,
In the braking force application characteristic for the low road surface friction coefficient, the automatic braking force application is started when the contact margin value is large as compared with the braking force application characteristic for the high road surface friction coefficient. A vehicle contact avoidance assist device characterized in that the maximum value of the automatic braking force is small. In the vehicle contact avoidance assistance device according to claim 5,
When the second road surface friction coefficient is smaller than the first road surface friction coefficient, the support control for the high road surface friction coefficient is switched to the support control for the low road surface friction coefficient,
In the assist control for the low road surface friction coefficient, a maximum value of the braking force application characteristic for the low road surface friction coefficient is set according to the second road surface friction coefficient. In the vehicle contact avoidance assistance device according to claim 5 or 6,
When the second road surface friction coefficient is larger than the first road surface friction coefficient, switching from the low road surface friction coefficient support control to the high road surface friction coefficient support control,
In the high road surface friction coefficient support control, the maximum value of the braking force application characteristic for the high road surface friction coefficient is decreased. In the vehicle contact avoidance assistance device according to any one of claims 1 to 7,
The assist control is a steering assist control that generates an automatic torque for the steering wheel,
In the low road surface friction coefficient assist control, a low torque is continuously applied as compared with the high road surface friction coefficient assist control.

Images