JP2018090161A - Vehicular brake control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control braking force in accordance with the state of a traveling road surface while suppressing a delay in control for determining the state of the aforementioned surface.SOLUTION: In a vehicular brake control apparatus including a camera for obtaining an image of a travel road ahead of a vehicle and a control device for controlling braking force to be applied to wheels of the vehicle independently for left and right wheels, the control device analyzes a camera image, discriminating whether the road surface ahead is a straight road or a curve road, and whether it is a left-right different μ road. Further, in a case where the road surface ahead is the left-right different μ road, the control device stops applying braking force to the left and right wheels, while in the case of the road ahead being not a left-right different μ road, with the road ahead a straight road, the device applies braking force equally to the left and right wheels. Further, in the case of the road ahead being not a left-right different μ road, with the road ahead a curve road, the device applies braking force so that the braking force on a wheel inside of the curve is larger than the braking force to a wheel outside of the curve.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vehicle braking control device.

  As an example of the vehicle braking control, for example, in the control disclosed in Patent Document 1, the desired vehicle turning speed of the driver is estimated using the steering angle of the vehicle and the reference vehicle speed when turning, and the estimated turning speed is calculated. The lateral acceleration of the vehicle estimated using the vehicle speed and the reference vehicle speed is compared with the actual lateral acceleration detected by the lateral acceleration sensor to determine the traveling road surface of the vehicle. Then, the reference turning speed is determined according to the determined road surface condition, the reference turning speed is compared with the actual turning speed detected by the turning speed sensor, and understeer or oversteer is determined. And the driving force is controlled.

JP 2003-252083 A JP 2012-066785 A JP 2000-043690 A JP 2009-149239 A

  The control used to calculate each estimated value by calculating each estimated value as in the control of Patent Document 1 does not hold when the vehicle is not in a state where each estimated value can be estimated. Therefore, a control delay occurs in the state acquisition by various sensors, the calculation of the control amount, and the like, and the driver may feel uncomfortable.

  The present invention aims to solve the above-described problems, and provides an improved vehicle braking control device that can improve the running stability of a vehicle by judging the state of a running road surface while suppressing a control delay. It is.

  In order to achieve the above object, a braking control device for a vehicle according to the present invention includes a camera that acquires an image of a forward travel path of the vehicle, and a braking force applied to the wheels of the vehicle by a left wheel and a right wheel. And a control device that independently controls. The control device is configured to analyze the image acquired by the camera and determine whether the forward traveling path is a straight path or a turning circuit, and whether the left and right are different μ roads. Here, the left and right different μ roads refer to road surfaces in which the μ value of the road surface on which the left wheel travels is different from the μ value of the road surface on which the right wheel travels. Further, when the front traveling road is a different right and left road, the control device cancels the application of braking force to the left wheel and the right wheel, and the front driving road is not a left and right different road. And when it is a straight road, the braking force is equally applied to the left wheel and the right wheel, and the forward running road is not a different left and right μ road and is a turning circuit. The braking force is applied so that the braking force applied to the turning inner wheel is greater than the braking force applied to the turning outer wheel.

  Whether or not the forward travel path is a different μ road and whether it is a straight path or a turning circuit is determined by camera image analysis, so control delay for grasping the condition of the travel path is suppressed. Can do. Further, the braking force can be changed according to the state of the forward travel path determined by the camera image. Therefore, the running stability of the vehicle can be improved.

FIG. 6 is a diagram for describing camera images and image analysis in the first embodiment. 3 is a flowchart for illustrating a control routine executed by the control device in the first embodiment. It is a figure for demonstrating the image analysis in Embodiment 2, and the control according to it. It is a figure for demonstrating the image analysis in Embodiment 2, and the control according to it. It is a figure for demonstrating the image analysis in Embodiment 2, and the control according to it. 10 is a flowchart for illustrating a control routine executed by the control device in the second embodiment. 10 is a flowchart for illustrating another control routine executed by the control device in the second embodiment. It is a figure for demonstrating the relationship between the difference of the ratio which the specific road surface occupies in each of two specific area | regions in an image, and the distribution variable coefficient of a braking force.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof is simplified or omitted.

Embodiment 1 FIG.
The system of this embodiment is used by being mounted on a vehicle. This system includes a view camera that captures at least a travel path ahead of the vehicle (hereinafter also referred to as “front travel path”) and acquires an image of the front travel path.

  The system also includes a control device. The control device controls the entire engine of the vehicle. In particular, the control device processes an image acquired by the view camera, and according to the processing result, the brake braking force (hereinafter simply referred to as “braking force”) to each of the four wheels of the vehicle. For example, VSC (Vehicle Stability Control) -ECU (Electronic Control Unit). The control device is mainly configured by a computer including a CPU, a ROM, and a RAM.

  In addition to the view camera, the control device includes various sensors such as a yaw rate sensor, a lateral acceleration sensor, a steering angle sensor, a wheel speed sensor, an M / C pressure sensor that detects a master cylinder pressure, or a STEP switch, and each of the vehicles. The actuator is connected by a wire harness, CAN, or the like. The ROM stores various control routines including a braking control routine described later. The control device controls the braking force applied to the wheel by operating each actuator according to the control routine based on the signal from each sensor and the acquired image of the view camera.

  With reference to FIG. 1, an image of a forward traveling road acquired by a view camera and image processing will be described. FIG. 1A schematically illustrates an example of an image of a forward travel path acquired by a view camera. The control device divides this image into areas A to J shown in FIG. 1B and performs image processing.

  The view camera is arranged so that the screen of the acquired image matches the center line of the vehicle. The screen is composed of two horizontal lines, an image and a vehicle center line (hereinafter simply referred to as “center line”), a horizontal line with a height of 2/3 and a horizontal line with a height of 1/3. It is delimited by. Furthermore, below the horizontal line with a height of 2/3, there are two points indicating the intersection of the horizontal line with the height of 2/3 and the center line, and the left and right ends of the own lane arranged symmetrically on the bottom of the screen. Are separated by two diagonal lines.

  The areas A, C, D, G, and H are arranged in this order symmetrically with the areas B, F, E, J, and I, respectively, with respect to the center line. Areas A and B are areas on the left side and the right side, respectively, above the horizontal line having a height of 2/3 of the screen. A region C, a region D, a region E, and a region F are arranged in order from the left between the horizontal line having a height of 2/3 and the horizontal line having a height of 1/3. Below the horizontal line having a height of 1/3, a region G, a region H, a region I, and a region J are arranged in order from the left.

  The control device includes a portion indicating a road surface (hereinafter also referred to as “specific road surface”) having characteristics specified by the color, brightness, roughness, and the like of the image for each of the regions A to J divided as described above. Calculate the percentage of Then, by comparing the ratio of the specific road surface between specific areas, it is determined whether the forward traveling road is a straight road or a turning circuit, and whether the road is a different μ road or the same μ road. The braking force is controlled accordingly. Here, the left and right different μ roads are road surfaces in which the μ value of the road surface on which the left wheel travels and the μ value of the road surface on which the right wheel travels are different, and the same μ road has the same μ value. It is the road surface.

  When it is determined by the image processing that the left and right are different μ roads, the control device does not control the braking force. As a result, it is possible to prevent an unintended moment from being generated due to a difference in braking force generated between the left and right different μ roads, and to reduce the uncomfortable feeling with respect to the brake operability.

  Further, when it is determined that the vehicle is traveling straight, control is performed so that equal braking force is applied to the left and right wheels, and control with an emphasis on deceleration is performed. Further, when it is determined that the circuit is a turning circuit, control is performed so that the braking force of the wheel on the inner side of the turning is increased, and the bending moment is emphasized.

  A control routine executed by the control device will be described with reference to the flowchart of FIG. In the routine of FIG. 2, first, in step S2, the road surface of the forward traveling road is acquired by photographing with the preview camera. Next, in step S4, preview camera image processing is performed. Specifically, the acquired image data is divided into areas A to J, and the ratio of the specific road surface is calculated for each area.

  In step S6, it is determined based on the ratio of the specific road surface whether or not the road is different right and left. If the left and right μ roads are different, brake braking is not performed in step S8, and control of the brake braking force is prohibited.

  If it is determined in step S6 that the road is not a left-right different μ road, it is next determined in step S10 whether the road is a straight road based on the ratio of the specific road surface. If it is determined that the vehicle is traveling straight, in step S12, the brake braking is switched to one that emphasizes deceleration, and is controlled so that the braking force is evenly applied to the left and right.

  If it is determined in step S10 that the road is not a straight path, it is determined in step S14 whether or not it is a turning circuit. If it is not determined in step S14 that the circuit is a turning circuit, the brake braking is switched to one that emphasizes deceleration in step S12.

  If it is determined in step S14 that the circuit is a turning circuit, in step S16, the brake braking is switched to one that places importance on the bending moment. Thereafter, the current process is temporarily terminated.

  As described above, according to the first embodiment, it is possible to grasp whether the forward traveling road is a different left-right μ road, whether it is a straight road or a turning circuit, based on the ratio of the specific road surface in each region of the image. . Therefore, the braking force can be changed according to the forward travel path, and the change in the yaw direction relative to the travel path during braking can be suppressed. In particular, on the left and right different μ roads, an unintended left and right deflection moment is generated due to the difference in the left and right road surfaces even when braking with an emphasis on deceleration is performed. In this regard, according to the processing of the present embodiment, since braking is not performed, the deflection moment on the left and right different μ roads can be suppressed. In addition, since the state of the forward travel path is determined by image processing, it is possible to easily control the braking force while suppressing the control delay without executing complicated and expensive control for brake braking.

Embodiment 2. FIG.
The system of the second embodiment has the same configuration as the system of the first embodiment. Specifically, the control device of the second embodiment is a different μ road on the left and right sides by comparing the ratios of the specific road surfaces of areas H and I, areas D and E, and areas C and F among areas A to J. It is determined whether the road is the same μ road, a straight road, a left curve, or a right curve.

  Specifically, determination of the forward travel path and braking control will be described with reference to FIGS. FIG. 3 shows the case of the same μ road and a straight road, FIG. 4 shows the case of the same μ road and a left-handed circuit (hereinafter also referred to as “left curve”), and FIG. 5 shows a left and right different μ road and a straight road. Represents the case. 3 to 5, (a) is a camera image, and (b) is a diagram for explaining control of braking force.

  In the image processing of FIG. 3, the ratio of the specific road surface of the area C and the area G is 0%, the ratio of the specific road surface of the area D, the area E, the area H, and the area I is 100%, and the ratio of the specific road surface of the area F. Is 20%, and the ratio of the specific road surface of the region J is calculated to be 70%. In this case, since the ratio of the specific road surface between the area H and the area I and the ratio of the specific road surface between the area H and the area I are the same, the same μ road and the straight road Determined.

  For example, as shown in FIG. 3B, when the front wheels are facing the turning direction, it is determined that the driver does not intend to turn and the correct operation is not performed. The deceleration is emphasized, and an equal braking force is applied to the left and right wheels to decelerate.

  In the image processing of FIG. 4, the ratio of the specific road surface of each area is 20% for area C, 95% for area D, 90% for area E, 15% for area F, 0% for area G, and 100 for area H. %, Region I is calculated as 100%, and region J is calculated as 70%. In this case, since the ratios of the specific road surfaces of the region H and the region I are the same, they are the same μ road, the ratio of the specific road surface of the region C is larger than the ratio of the specific road surface of the region F, and the specification of the region D Since the ratio of the road surface is larger than the ratio of the specific road surface in the region E, it is determined that the road is a left curve.

  In this case, for example, as shown in FIG. 4B, it can be determined that the driver is steering in accordance with the left front curve, but is not turning according to the steering. Therefore, the braking force is assisted and controlled so as to turn according to the road surface by the braking force different on the left and right. That is, the braking force is controlled with emphasis on the bending moment so that the braking force of the wheel on the inner side of the turning is increased with respect to the left and right wheels.

  In the image processing of FIG. 5, the ratio of the specific road surface of each region is 0% for region C, 100% for region D, 0% for region E, 0% for region F, 0% for region G, and 100% for region H. %, Area I is 0%, and area J is 0%. In this case, since the area H is sufficiently larger than the area I and the area D is sufficiently larger than the area E, the ratio of the specific road surface is determined as a right / left different μ road and a straight road.

  When it is determined that the left and right μ roads are different, the control device performs control so as not to apply the braking force. As a result, it is possible to prevent an unintended moment from being generated due to a difference in braking force generated between the left and right different μ roads, and to reduce the uncomfortable feeling with respect to the brake operability.

  In short, the control device determines whether the left and right different μ roads or the same μ road is based on the difference in the ratio of the specific road surface between the region H and the region I (hereinafter, “difference | HI |”). Since the region H and the region I are the regions closest to the vehicle body and on the center of the road surface, the ratio of the specific road surface is the same with a value close to 100% for the same μ road. Therefore, the control device determines whether the area is the same μ road or the left and right different μ roads by comparing the area H and the area I. The braking amount to be applied is set to 0 when it is determined that the left and right are different μ roads. Therefore, in actual control, it is not determined whether the vehicle is a straight path or a turning circuit.

  On the premise that the roads are the same μ road, the difference in the ratio of the specific road surface between the region D and the region E (hereinafter referred to as “difference | D−E |”) is approximately the same when the road is a straight road. The control device determines that the road is a straight path when the difference | D−E | is equal to or less than the straight line determination threshold value.

  On the assumption that the roads are the same μ road, in the case of a left curve, the ratio of the specific road surface is such that the region D is larger than the region E and the region C is larger than the region F. Using this, the control device has a value obtained by subtracting the specific ratio of the area E from the specific ratio of the area D (hereinafter referred to as “difference (DE)”) larger than the first left curve determination threshold, and the area C. When the value obtained by subtracting the specific ratio of the region F from the specific ratio (hereinafter referred to as “difference (C−F)”) is larger than the second left curve determination threshold value, it is determined to be a left curve.

  On the assumption that the roads are the same μ road, in the case of a right curve, the ratio of the specific road surface is such that the area E is larger than the area D and the area F is larger than the area C. Using this, when the value obtained by subtracting the specific ratio of region D from the specific ratio of region E (hereinafter, “difference (ED)”) is larger than the first right curve determination threshold, and When the value obtained by subtracting the specific ratio of the region C from the ratio (hereinafter, “difference (F−C)”) is larger than the second right curve determination threshold, it is determined that the curve is the right curve.

  FIG. 6 shows a control routine executed by the control device. In the control routine of FIG. 6, first, an image of the preview camera is acquired in step S102. In step S104, image processing of the preview camera is performed. Specifically, the acquired image data is divided into areas A to J, and the ratio of the specific road surface is calculated for each area.

  In step S106, it is determined whether or not the difference | HI | is greater than the left / right different μ road determination threshold ThMu. If the determination result in step S106 is YES and | HI |> ThMu is satisfied, then the left / right different μ road state flag MuDiff is turned ON in step S108. On the other hand, if the determination result in step S106 is NO and | HI |> ThMu is not satisfied, then in step S110, the left / right different μ road state flag MuDiff is turned OFF. That is, the left / right different μ road state flag MuDiff is a flag indicating that the forward traveling road is a left / right different μ road when it is ON and the same μ road when it is OFF.

  If the left / right different μ road state flag MuDiff is set to ON in step S108, then, in step S112, both the RR wheel brake braking amount coefficient Krr and the RL wheel brake braking amount coefficient Krl are set to 0. The RR wheel indicates the right rear wheel, and the RL wheel indicates the left rear wheel.

  If the left / right different μ road state flag MuDiff is turned off in step S110, it is then determined in step S114 whether or not the difference | D−E | is equal to or smaller than the straight line determination threshold ThT0.

  If the determination result of step S114 is YES and | D−E | ≦ ThT0 is satisfied, the forward travel path is straight ahead in step S116, and it is determined that TURN = S. In this case, in step S118, both the RR wheel brake braking amount coefficient Krr and the RL wheel brake braking amount coefficient Krl are set to 0.5, and are set to the same left and right brake braking amount coefficients. That is, the braking force applied to the left and right wheels is set to be equal.

  If the determination result in step S114 is NO, then in step S120, the difference (D−E) is greater than the first left curve determination threshold ThTl1 and the difference (C−F) is equal to the second left curve. It is determined whether or not the determination threshold value is greater than ThTl2.

  If the determination result in step S120 is YES, and D-E> ThTl1 and C-F> ThTl2 are satisfied, it is determined in step S122 that the forward traveling road is a left curve, and TURN = L. . Thereafter, in step S124, the RR wheel brake braking amount coefficient Krr is set to 0, and the RL wheel brake braking amount coefficient Krl is set to 1. As a result, in the left curve, the braking force to the left wheel is set to be larger than the braking force to the right wheel.

  If the determination result of step S120 is NO, then in step S126, the difference (ED) is larger than the first right curve determination threshold ThTr1, and the difference (F-C) is the second right curve determination. It is determined whether or not it is larger than the threshold value ThTr2.

  If the determination result in step 126 is YES, and ED> ThTr1 and FC> ThTr2 are satisfied, it is determined in step S128 that the forward traveling road is a right curve and TURN = R. In this case, the RR wheel brake braking amount coefficient Krr is set to 1, and the RL wheel brake braking amount coefficient Krl is set to 0. As a result, the right curve is set so that the braking force applied to the right wheel is greater than the braking force applied to the left wheel.

  When the determination result of step S126 is NO, both the RR wheel brake braking amount coefficient Krr and the RL wheel brake braking amount coefficient Krl are set to 0.5.

  After setting the RR wheel and RL wheel brake braking amount coefficients Krr and Krl in step S112, S118, S124, S130, or S132, in step S134, the RR wheel brake braking amount BrkRr and the RL wheel brake braking amount BrkRl, The calculated Krr and Krl are multiplied to determine the brake braking amount. Thereafter, the current process is temporarily terminated.

  FIG. 7 is a diagram for explaining another control example of the second embodiment. The routine of FIG. 7 is executed in place of the routine of FIG. The routine shown in FIG. 7 differs from the routine shown in FIG. 6 in that the RR wheel brake braking amount coefficient Krr and the RL wheel brake braking amount coefficient Krl are calculated based on the distribution variable coefficient when the same μ road is used.

  Specifically, the process of determining left and right different μ roads or the same μ road from steps S102 to S110 of FIG. 7 and the process of step S112 when determined to be left and right different μ roads are the routine of FIG. Are the same.

In FIG. 7, it is determined that the roads are the same μ road, and the left and right different μ road state flag MuDiff is turned OFF in step S110. Next, in step S202, the RR wheel brake braking amount coefficient Krr and the RL wheel brake are set. The braking amount coefficient Krl is calculated by the following equations (1) and (2).
RR wheel brake braking amount coefficient Krr = 0.5-distribution variable coefficient Kr (x) (1)
RL wheel brake braking amount coefficient Krl = 0.5 + distribution variable coefficient Kr (x) (2)

  In the above formulas (1) and (2), the distribution variable coefficient Kr (x) is a value set according to a value x obtained by subtracting the specific ratio of the area E from the specific ratio of the area D. FIG. 8 shows the relationship between the distribution variable coefficient Kr (x) and the value x. The distribution variable coefficient is a value that varies between 0 and 0.5 according to the value x. Specifically, when the value x is smaller than the reciprocal of the first right curve determination threshold value ThTrl (that is, -ThTrl), the minimum value is set to -0.5, the value x is equal to or greater than -ThTrl, and the straight line determination threshold value is set. In a range smaller than the reciprocal number (that is, -ThT0), it increases proportionally from -0.5 to 0. In the range where the value x is greater than or equal to -ThT0 and less than or equal to the straight line determination threshold ThT0, it is proportionally increased from 0 to 0.5 in the range larger than the straight line determination threshold ThT0 and smaller than the first left curve determination threshold ThTl1; It is set to 0.5 when it is equal to or greater than the first left curve determination threshold ThTl1.

  Thereafter, in step S134, the RR wheel brake braking amount BrkRr and the RL wheel brake braking amount BrkRl are determined in accordance with the RR wheel brake braking amount coefficient Krr and the RL wheel brake braking amount coefficient Krl set in step S112 or S202. This is the end of the current process.

  In the above embodiment, when referring to the number of each element, quantity, quantity, range, etc., the reference is made unless otherwise specified or the number is clearly specified in principle. The invention is not limited to the numbers. Further, the structure and the like described in this embodiment are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

Claims (1)

A camera that acquires an image of the road ahead of the vehicle;
A control device for independently controlling the braking force applied to the wheels of the vehicle with the left wheel and the right wheel;
The controller is
Analyzing the image acquired by the camera, whether the forward travel path is a straight path or a turning circuit, and the μ value of the road surface on which the left wheel travels and the μ value of the road surface on which the right wheel travels Whether it is a different right and left different μ road,
When the forward traveling road is a different left and right μ road, release of the braking force to the left wheel and the right wheel is canceled,
When the forward travel path is not a left-right different μ road and is a straight path, a braking force is equally applied to the left wheel and the right wheel,
When the forward travel path is not a different left and right μ road and is a turning circuit, the braking force is applied so that the braking force to the turning inner wheel is larger than the braking force to the turning outer wheel. To
The vehicle braking control device is configured as described above.

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