JP2021109543A - Determination device for road surface state - Google Patents

Abstract

To determine correctly, a state of a road surface, by canceling affection which is caused by load movement of a vehicle body in turning in a lateral direction.SOLUTION: There is provided a determination device for determining a state of a road surface on which a vehicle travels. The determination device acquires rotation speed of a tire attached to the vehicle sequentially, acquires lateral acceleration applied to the vehicle sequentially, then, according to the lateral acceleration acquired sequentially, selecting and acquiring sequentially any one out of a group including a first slip ratio which is a slip ratio of a tire calculated on the basis of rotation speed of the left tires, and a second slip ratio which is a slip ratio of a tire calculated on the basis of rotation speed of the right tires, out of the rotation speed of the tire acquired sequentially, then acquires sequentially, drive force of the vehicle, then on the basis of many data sets of the slip ratio and drive force as a regression coefficient indicating a linear relationship between the slip ratio and the drive force, calculates inclination of the slip ratio to the drive force, and on the basis of the inclination, determines the state of the road surface.SELECTED DRAWING: Figure 3

Description

The present invention relates to a determination device, method and program for determining the state of the road surface on which the vehicle travels.

Understanding the slip ratio of tires mounted on a moving vehicle is important for controlling the running of the vehicle. The slip ratio can be defined as, for example, (driving wheel speed-body speed) / body speed, and represents the ease of slipping of a tire. Since the slip ratio depends on the condition of the road surface (slipperiness of the tire), the condition of the road surface during traveling is determined by determining the slip ratio during traveling, and this is used for controlling the traveling of the vehicle. There is. The road surface condition information can be used, for example, to warn the driver and control the braking system. The slip ratio has a linear relationship with the driving force of the vehicle (or the acceleration of the vehicle), and for example, the state of the road surface can be determined according to the regression coefficient (slope) representing this relationship (for example, Patent Document 1). And 2nd grade). The regression coefficient can be calculated from a large number of data sets of a slip ratio that changes from moment to moment during running and a driving force (acceleration) that also changes from moment to moment during running.

Japanese Patent No. 2002-274357 Japanese Patent No. 2002-362345

However, while the vehicle is turning, the slip ratio changes from the time of straight running due to the influence of the load movement in the left-right direction of the vehicle body. As a result, even when the vehicle is traveling on the road surface in the same state during turning, the linear relationship between the slip ratio and the driving force also changes, so that the road surface condition cannot be correctly determined.

An object of the present invention is to provide a determination device, method and program capable of canceling the influence caused by the lateral load movement of the vehicle body during turning and correctly determining the state of the road surface.

The determination device according to the first aspect of the present invention is a determination device that determines the state of the road surface on which the vehicle travels, and includes a rotation speed acquisition unit that sequentially acquires the rotation speed of tires mounted on the vehicle, and the vehicle. Calculated based on the rotational speed of the left tire among the rotational speeds of the tires that are sequentially acquired according to the lateral acceleration acquisition unit that sequentially acquires the lateral acceleration applied to the One of the groups including the first slip ratio, which is the slip ratio of the tire, and the second slip ratio, which is the slip ratio of the tire calculated based on the rotation speed of the right tire, is sequentially selected. The slip ratio calculation unit to be acquired, the driving force acquisition unit to sequentially acquire the driving force of the vehicle, and a large number of the slip ratio and the driving force as regression coefficients representing the linear relationship between the slip ratio and the driving force. It includes a slope calculation unit that calculates the slope of the slip ratio with respect to the driving force based on the data set, and a determination unit that determines the state of the road surface based on the slope.

The determination device according to the second aspect of the present invention is the determination device according to the first aspect, and the slip ratio calculation unit determines the first slip ratio when the vehicle turns to the right according to the lateral acceleration. , The second slip ratio is selected when the vehicle turns to the left.

The determination device according to the third aspect of the present invention is the determination device according to the first aspect or the second aspect, and the slip ratio calculation unit is the first slip according to the lateral acceleration acquired sequentially. The ratio, the second slip ratio, and the third slip ratio, which is the slip ratio of the tires calculated based on the average of the rotation speeds of the left and right tires among the rotational speeds of the tires sequentially acquired. One of them is sequentially selected from the group and acquired.

The determination device according to the fourth aspect of the present invention is the determination device according to the third aspect, and the slip ratio calculation unit determines the first slip ratio when the vehicle turns to the right according to the lateral acceleration. When the vehicle turns left, the second slip ratio is selected, and when the vehicle goes straight, the third slip ratio is selected.

The determination device according to the fifth aspect of the present invention is the determination device according to any one of the first to fourth aspects, and the inclination calculation unit is based on a large number of data sets of the slip ratio and the driving force. The slope is calculated sequentially or by batch processing.

The determination method according to the sixth aspect of the present invention is a determination method for determining the state of the road surface on which the vehicle travels, and includes the following. Further, the determination program according to the seventh aspect is a determination program for determining the state of the road surface on which the vehicle travels, and causes the computer to execute the following: ・ The rotation speeds of the tires mounted on the vehicle are sequentially acquired. That-The lateral acceleration applied to the vehicle is sequentially acquired. Of the rotational speeds of the tires that are sequentially acquired according to the lateral accelerations that are sequentially acquired, the calculation is made based on the rotational speed of the left tire. One of the groups including the first slip ratio, which is the slip ratio of the tire, and the second slip ratio, which is the slip ratio of the tire calculated based on the rotation speed of the right tire, is sequentially selected and acquired. -Obtaining the driving force of the vehicle in sequence-As a regression coefficient representing the linear relationship between the slip ratio and the driving force, the driving force is based on a large number of data sets of the slip ratio and the driving force. Calculate the slope of the slip ratio ・ Determine the condition of the road surface based on the slope.

During the turning of the vehicle, the load is relatively reduced by the centrifugal force on the inside of the turning and the slip of the tire is relatively increased, while the load is relatively increased on the outside of the turning, so that the tire is relatively tired. Slip is reduced. In addition, accompanying this phenomenon, the slope of the slip ratio with respect to the driving force of the vehicle increases as the magnitude of the lateral acceleration increases on the inside of the turn, but the value converges and becomes almost constant on the outside of the turn. .. Utilizing this phenomenon, according to the above viewpoint, the slip ratio (first slip ratio) calculated based on the rotation speed of the left tire and the rotation speed of the right tire according to the lateral acceleration acquired sequentially. Any one of the slip ratios is sequentially selected and acquired from the group including the slip ratio (second slip ratio) calculated based on. That is, it is possible to select a slip ratio that is less affected by the lateral load movement of the vehicle body due to turning according to the lateral acceleration that depends on the turning state, and based on such a slip ratio, slip with respect to the driving force. The slope of the ratio is calculated. Therefore, the state of the road surface can be correctly determined based on such an inclination.

The schematic diagram which shows the appearance that the control unit as a determination device which concerns on 1st Embodiment is mounted on a vehicle. The block diagram which shows the electrical structure of the control unit which concerns on 1st Embodiment. The flowchart which shows the flow of the determination process of the road surface condition which concerns on 1st Embodiment. A graph showing the relationship between the slip ratio and the turning radius of the vehicle. A graph showing the relationship between the slip ratio and the driving force. A graph showing the relationship between various slip ratios and driving force when going straight, turning left, and turning right. The graph which shows the relationship between the 1st slip ratio and the 2nd slip ratio, and a driving force with respect to various vehicle speeds at the time of going straight. The graph which shows the relationship between the 1st slip ratio and the 2nd slip ratio, and a driving force with respect to various vehicle speeds at the time of a left turn. The graph which shows the relationship between the 1st slip ratio and the 2nd slip ratio, and a driving force with respect to various vehicle speeds at the time of a right turn. The graph which shows the evaluation result of the effect of an embodiment. The graph which shows another evaluation result of the effect of an embodiment. The graph which shows the further evaluation result of the effect of an embodiment. The graph which shows the further evaluation result of the effect of an embodiment.

Hereinafter, the determination device, the method, and the program according to some embodiments of the present invention will be described with reference to the drawings.

<1. First Embodiment>
<1-1. Judgment device configuration>
FIG. 1 is a schematic view showing a state in which a control unit 2 as a determination device according to the present embodiment is mounted on a vehicle 1. The vehicle 1 is a four-wheeled vehicle, and includes a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. _{Tires T FL} , T _FR , T _RL , and T _RR are mounted on the wheels FL, FR, RL, and RR, respectively. The vehicle 1 according to the present embodiment is a front engine / front drive vehicle (FF vehicle), the front wheel tires T _FL and T _FR are drive wheel tires, and the rear wheel tires T _RL and T _{R R} are driven wheel tires. .. The control unit 2, the tire T _FL during running, T _FR, based on T _RL, the rotational speed of the information T _RR, the tire _{T FL, T FR, T RL} , slip and ease of T _RR traveling The slip ratio S representing the above is determined, and the state of the road surface on which the vehicle 1 travels is determined based on the slip ratio S. The road surface condition referred to here is the slipperiness _{of the tires T FL} , T _FR , T _RL , and T _{R R.} The road surface condition information can be applied to various uses, for example, it can be used for various controls for controlling the running of a vehicle, for creating a road map for the road surface condition, and the like. Various controls for controlling the running of the vehicle include, for example, warning the driver about hydroplaning and the like, control of the braking system, control of the inter-vehicle distance, and the like.

Wheel speed sensors 6 are attached to the tires T _FL , T _FR , T _RL , and T _RR (more accurately, wheels FL, FR, RL, and RR) of the vehicle 1, respectively. , Detects the rotational speeds (ie, wheel speeds) V1 to V4 of the tires mounted on its own wheels. V1~V4 are respectively the rotational speed of the tire _{T FL, T FR, T RL} , T RR. As the wheel speed sensor 6, any wheel speed sensor 6 can be used as long as it can detect the wheel speeds of the running wheels FL, FR, RL, and RR. For example, a type of sensor that measures the wheel speed from the output signal of the electromagnetic pickup can be used, or a type of sensor that uses rotation to generate electricity and measures the wheel speed from the voltage at this time, like a dynamo. It can also be used. The mounting position of the wheel speed sensor 6 is also not particularly limited, and can be appropriately selected according to the type of sensor as long as the wheel speed can be detected. The wheel speed sensor 6 is connected to the control unit 2 via a communication line 5. Information on the rotational speeds V1 to V4 detected by the wheel speed sensor 6 is transmitted to the control unit 2 in real time.

The vehicle 1 is equipped with an acceleration sensor 7 that detects the acceleration α of the vehicle 1. The structure and mounting position of the acceleration sensor 7 are not particularly limited as long as the acceleration α of the vehicle 1 can be detected. The acceleration sensor 7 is connected to the control unit 2 via a communication line 5. The information on the acceleration α detected by the acceleration sensor 7 is transmitted to the control unit 2 in real time in the same manner as the information on the rotation speeds V1 to V4.

Further, the vehicle 1 is equipped with a lateral acceleration sensor 4 that detects the lateral acceleration γ applied to the vehicle 1. The lateral acceleration γ is a centrifugal acceleration that acts on the vehicle 1 toward the outside of the turn when the vehicle 1 turns. The structure and mounting position of the lateral acceleration sensor 4 are not particularly limited as long as the lateral acceleration γ can be detected. The lateral acceleration sensor 4 is connected to the control unit 2 via a communication line 5. The information on the lateral acceleration γ detected by the lateral acceleration sensor 4 is transmitted to the control unit 2 in real time in the same manner as the information on the rotational speeds V1 to V4 and the acceleration α.

Further, the vehicle 1 is equipped with a yaw rate sensor 8 that detects the yaw rate ω of the vehicle 1. The yaw rate ω is the rotational angular velocity around the vertical axis when the vehicle 1 turns. As the yaw rate sensor 8, for example, a sensor of a type that detects the yaw rate by using the Coriolis force can be used, but the structure and the mounting position are not particularly limited as long as the yaw rate ω can be detected. The yaw rate sensor 8 is connected to the control unit 2 via a communication line 5. The information on the yaw rate ω detected by the yaw rate sensor 8 is transmitted to the control unit 2 in real time in the same manner as the information on the rotational speeds V1 to V4, the acceleration α and the lateral acceleration γ.

FIG. 2 is a block diagram showing an electrical configuration of the control unit 2. The control unit 2 is mounted on the vehicle 1 and includes an I / O interface 11, a CPU 12, a ROM 13, a RAM 14, and a non-volatile and rewritable storage device 15, as shown in FIG. The I / O interface 11 is a communication device for communicating with external devices such as a wheel speed sensor 6, an acceleration sensor 7, a lateral acceleration sensor 4, a yaw rate sensor 8, and a display 3. The ROM 13 stores a program 9 for controlling the operation of each part of the vehicle 1. By reading the program 9 from the ROM 13 and executing the program 9, the CPU 12 virtually includes the rotation speed acquisition unit 21, the driving force acquisition unit 22, the lateral acceleration acquisition unit 23, the turning radius acquisition unit 24, the slip ratio calculation unit 25, and the relationship. It operates as a specific unit 26, a correction unit 27, an inclination calculation unit 28, and a determination unit 29. Details of the operation of each part 21 to 29 will be described later. The storage device 15 is composed of a hard disk, a flash memory, or the like. The storage location of the program 9 may be the storage device 15 instead of the ROM 13. The RAM 14 and the storage device 15 are appropriately used for the calculation of the CPU 12.

The display 3 can output various information including an alarm to the user (mainly the driver), and can be realized in any form such as a liquid crystal display element, a liquid crystal monitor, a plasma display, and an organic EL display. .. The mounting position of the display 3 can be appropriately selected, but it is preferably provided at a position that is easy for the driver to understand, such as on the instrument panel. When the control unit 2 is connected to the car navigation system, the car navigation monitor can also be used as the display 3. When a monitor is used as the display 3, the alarm can be an icon or text information displayed on the monitor.

<1-2. Judgment processing of slip ratio and road surface condition based on this>
Hereinafter, with reference to FIG. 3 _{, a determination process for determining the slip ratio S of the running tires T FL} , T _FR , T _RL , and T _RR and determining the state of the road surface on which the vehicle 1 is traveling will be described. do. This determination process is repeatedly executed while the electric system of the vehicle 1 is powered on.

In step S1, the rotation speed acquisition unit 21 acquires the rotation speeds V1 to V4 of _{the running tires T FL} , T _FR , T _RL , and T _RR. The rotation speed acquisition unit 21 receives an output signal from the wheel speed sensor 6 in a predetermined sampling cycle, and converts this into rotation speeds V1 to V4.

In step S2, the driving force acquisition unit 22 acquires the acceleration α of the vehicle 1. The driving force acquisition unit 22 receives an output signal from the acceleration sensor 7 in a predetermined sampling cycle, and converts this into an acceleration α.

In step S3, the lateral acceleration acquisition unit 23 acquires the lateral acceleration γ applied to the vehicle 1. The lateral acceleration acquisition unit 23 receives the output signal from the lateral acceleration sensor 4 in a predetermined sampling cycle, and converts this into the lateral acceleration γ.

In step S4, the turning radius acquisition unit 24 acquires the yaw rate ω of the vehicle 1. The turning radius acquisition unit 24 receives an output signal from the yaw rate sensor 8 in a predetermined sampling cycle, and converts this into a yaw rate ω. The turning radius acquisition unit 24 acquires the turning radius R of the vehicle 1 by dividing the vehicle body speed by the yaw rate ω. Since the vehicle body speed can be approximated by the speed of the driving wheel, it can be calculated as, for example, R = (V3 + V4) / 2ω. The vehicle body speed can also be calculated by integrating the acceleration α.

In the next step S5, the slip ratio calculation unit 25 calculates the slip ratio S based on the rotation speeds V1 to V4. In the present embodiment, the slip ratio S is calculated as (driving wheel speed − vehicle body speed) / vehicle body speed, and the speed of the driven wheel is used as the vehicle body speed. There are three methods for calculating the slip ratio S. The first method is a method of calculating based only on the rotation speed of the left tire among the left and right tires. The second method is a method of calculating based only on the rotation speed of the right tire among the left and right tires. The third method is a method of averaging the rotational speeds between the left and right wheels and calculating based on the average of the rotational speeds of the left and right tires. In this embodiment, it is defined as follows.
First method (left wheel):
S = (V1-V3) / V3
Second method (right wheel):
S = (V2-V4) / V4
Third method (left-right average):
S = {(V1 + V2)-(V3 + V4)} / (V3 + V4)

Here, the slip ratio S based on any of the above three methods is acquired as the slip ratio S used in the later calculation. The slip ratio by the first method (hereinafter, may be referred to as the first slip ratio), the slip ratio by the second method (hereinafter, may be referred to as the second slip ratio), and the slip ratio by the third method (hereinafter, may be referred to as the second slip ratio). Which slip ratio S is selected from the third slip ratio) is determined according to the lateral acceleration γ calculated in the latest step S3. More specifically, the slip ratio calculation unit 25 sets the first slip ratio S when the vehicle 1 turns right and the first slip ratio S when the vehicle 1 turns left, according to the latest (that is, substantially the current) lateral acceleration γ. The 2 slip ratio S is selected, and the 3rd slip ratio S is selected when going straight. At this time, for example, when −A ≦ γ ≦ A, it can be determined that the vehicle is going straight, when γ <−A, it is when turning right, and when A <γ, it is when turning left. .. A is a threshold value that takes a predetermined positive value. The reason why such a slip ratio S is selected will be described later.

In the next step S6, the slip ratio S acquired in step S5 and the driving force F of the vehicle 1 based on the acceleration α acquired in step S2 are filtered to eliminate the measurement error. The driving force F of the vehicle 1 can be appropriately calculated from the acceleration α acquired in step S2.

The data of the rotational speeds V1 to V4, the acceleration α, the lateral acceleration γ, the yaw rate ω, the turning radius R, and the filtered slip ratio S and the driving force F acquired in the steps S1 to S6 executed continuously are obtained. It is treated as a data set acquired at the same time or approximately at the same time, and stored in the RAM 14 or the storage device 15. As shown in FIG. 3, since steps S1 to S6 are repeatedly executed, the above data sets are sequentially acquired. After step S6, when N1 such data sets (N1 ≧ 2) are accumulated, the process proceeds to step S7. Step S7 is executed only once. After step S7 is executed once, the process proceeds to step S8 after steps S1 to S6.

In step S7, the relationship specifying unit 26 relates the turning radius R and the slip ratio S based on a large number of data sets of the turning radius R calculated in step S4 and the slip ratio S filtered in step S6. Identify the relationship information that represents. This relational information is used for the subsequent correction of the slip ratio S (step S8). As will be described in detail later, in the present embodiment, the state of the road surface is determined based on the linear relationship between the slip ratio S and the driving force F. However, while the vehicle 1 is turning, even if the vehicle 1 is traveling on the road surface in the same state, the linear relationship between the slip ratio S and the driving force F changes as compared with when the vehicle goes straight, so that the road surface condition is correct. It may not be possible to judge. This is because a track difference (path difference) is generated between the left and right tires during turning, and the slip ratio S changes from the time of straight running due to the influence of this track difference. Therefore, here, in order to realize various stable controls based on the slip ratio S, the influence caused by the difference between the left and right orbits during turning is canceled from the slip ratio S.

The difference between the left and right orbits during turning depends on the turning radius R, and a certain relationship is established between the turning radius R and the slip ratio S. According to the experiment conducted by the present inventor, the slip ratio S is generally represented by a quadratic function of the reciprocal of the turning radius R, as shown in FIG. _{In step S7, the relationship specifying unit 26 specifies the coefficients a 1} , b ₁ and c ₁ in the following equation as the relationship information representing the relationship between the turning radius R and the slip ratio S.
S = a ₁ (1 / R) ² + b ₁ (1 / R) + c ₁

The coefficients a ₁ , b ₁ and c ₁ are calculated based on a large number of data sets of the slip ratio S and the turning radius R stored in the RAM 14 or the storage device 15, and are calculated by, for example, a method such as the least squares method. NS.

The apex of the parabola representing the relationship between the reciprocal of the turning radius R and the slip ratio S corresponds to the straight running, and as shown in FIG. 4, roughly overlaps the vertical axis representing the slip ratio S. In other words, b ₁ is approximately 0. _{Therefore, here, only the coefficients a 1} and c ₁ can be specified as the relational information according to the following equation.
S = a ₁ (1 / R) ² + c ₁

When step S7 is completed, the process returns to step S1 and steps S1 to S6 are repeated again. As shown in FIG. 3, step S7 is executed once, and after the relationship information a ₁ , b ₁ and c ₁ between the turning radius R and the slip ratio S are specified, steps S1 to S6 are executed once. Each time, steps S8 to S15 are repeatedly executed following this.

_{In step S8, the correction unit 27 updates the latest based on the relationship information a 1} , b ₁ and c ₁ indicating the relationship between the turning radius R and the slip ratio S and the turning radius R acquired in the latest step S4. The slip ratio S acquired in step S6 of the above is corrected. As described above, the slip ratio S is represented by a quadratic function of the reciprocal of the turning radius R. Therefore, the correction unit 27, according to the following equation, from the slip ratio S, by subtracting the value obtained by multiplying the coefficients a ₁ to a value obtained by squaring the inverse of the turning radius R of the correction time, corrects the slip ratio S.
S = S-a ₁ (1 / R) ²
The slip ratio S may be corrected by further subtracting the value obtained by multiplying the reciprocal of the turning radius R at the time of correction _{by the coefficient b 1 from the slip ratio S according to the following equation.}
S = S-a ₁ (1 / R) ^2- b ₁ (1 / R)

According to the above correction formula, as shown in FIG. 4, it is possible to calculate the slip ratio S converted when (1 / R) = 0, that is, when going straight, and turning left from the slip ratio S. And the influence of the orbital difference due to turning right is canceled.

In the subsequent steps S9 to S15, the road surface condition (tire slipperiness) is determined based on the slip ratio S corrected as described above. In the present embodiment, the road surface condition is determined based on the relationship between the slip ratio S and the driving force F. A linear relationship as shown in FIG. 5 is established between the slip ratio S and the driving force F, and the slope f ₁ of the slip ratio S with respect to the driving force F changes according to the state of the road surface. _{Therefore, here, the regression coefficient (slope f 1} ) representing the linear relationship between the slip ratio S and the driving force F is calculated based on the data sets of the slip ratio S and the driving force F acquired so far. The condition of the road surface is determined according to the above.

By the way, the inclination f ₁ changes not only by the condition of the road surface but also by the load movement in the left-right direction of the vehicle body that occurs during the turning of the vehicle. Therefore, if the influence of such load movement included in the inclination f ₁ cannot be canceled, the accuracy of determining the state of the road surface based on _{the inclination f 1 may decrease.} The reason why one type of slip ratio S is selected from the three types of slip ratio S in step S5 is to cancel the influence of the load transfer during such turning.

FIG. 6 shows a straight line, a left turn with a smaller lateral acceleration γ, a left turn with a larger lateral acceleration γ, and a right turn with a smaller lateral acceleration γ. It is a graph which shows the linear relationship between three kinds of slip ratios S and driving force F at the time of right-hand turn with a larger magnitude of lateral acceleration γ. Further, FIGS. 7A to 7C are graphs plotting the relationship between the slip ratio S and the driving force F based on the measurement data when the actual vehicle is driven. The vertical axis is the slip ratio and the horizontal axis is the driving force. Force F. FIG. 7A shows the relationship between the first slip ratio and the second slip ratio when going straight and the driving force F, and FIG. 7B shows the relationship between the first slip ratio and the second slip ratio and the driving force F when turning left. 7C shows the relationship between the first slip ratio and the second slip ratio at the time of turning right and the driving force F. _{In each graph, the value of the slope f 1} of the slip ratio S with respect to the driving force F is shown in the upper right. In FIGS. 7A to 7C, a graph is drawn for each vehicle body speed of the vehicle 1. Since the magnitude of the lateral acceleration γ is proportional to the square of the vehicle body speed, the larger the vehicle body speed, that is, the lower graph in each figure, the larger the magnitude of the lateral acceleration γ.

During the turning of the vehicle 1, the load is relatively reduced by the centrifugal force on the inside of the turning and the slip of the tire is relatively increased, while the load is relatively increased on the outside of the turning. Tire slip is reduced. Also, associated with this phenomenon, as shown in FIGS. 6 and 7A~ Figure 7C, the inclination f ₁ of the slip ratio S with respect to the driving force F of the vehicle 1, at a pivot inside the magnitude of the lateral acceleration γ It can be seen that the larger the value, the larger the value, but the value converges on the outside of the turn and becomes almost constant. Therefore, when turning left, the second slip ratio S based on the rotation speed of the right tire _{converges the inclination f 1} to the smallest value, and when turning right, the second slip ratio S based on the rotation speed of the left tire. 1 The slip ratio S _{converges the slope f 1} to the smallest value. When going straight, there is no significant difference in the _{inclination f 1} regardless of the slip ratio S.

_{Utilizing the above phenomenon, in step S5, one} of the first, second, and third slip ratios S is sequentially selected as the slip ratio S used for calculating the slope f1 according to the lateral acceleration γ. NS. Thereby, it is possible to select the slip ratio S having a small influence of the load movement in the left-right direction of the vehicle body due to the turning according to the lateral acceleration γ depending on the turning state. Therefore, in the step described later, it is possible to correctly determine the state of the road surface based _{on the slope f 1 calculated based on the slip ratio S.}

Further, the regression coefficient representing the linear relationship between the slip ratio S and the driving force F can be calculated based on a large number of data sets of the slip ratio S and the driving force F. However, in order to correctly calculate the regression coefficient based on a large number of data sets, it is desirable that the variation of the data sets is a certain value or more. However, there is not much variation in the data set during the period when the driving force F does not change so much, for example, when the vehicle is traveling at a constant speed on a downhill. _{Therefore, in the present embodiment, the regression coefficient (slope f 1} ) is determined by different methods according to the degree of variation in the driving force F at the time of determining the state of the road surface.

In step S9, the inclination calculation unit 28 determines whether or not the variation of the driving force F is equal to or more than a certain value at the present time when the road surface condition is determined. In the present embodiment, the width and variance of a large number of driving force F values acquired in the most recent predetermined period are calculated, and when these are each equal to or more than a predetermined threshold value, the variation is considered to be a certain value or more. The determination is made, and the process proceeds to step S10. On the other hand, when at least one of the width and the variance of the values of the large number of driving forces F is smaller than the predetermined threshold value, it is determined that the variation is not equal to or more than a certain value, and the process proceeds to step S11.

In step S10, the inclination calculation unit 28 is represented by the following equation based on a large number of data sets of the slip ratio S and the driving force F in the present and the predetermined period prior to the determination of the road surface condition. _{The regression coefficients f 1} and f ₂ representing the linear relationship between the slip ratio S and the driving force F are calculated. f ₁ is the slope of the slip ratio S with respect to _{the driving force F, and f 2} is an intercept of the slip ratio S with respect to the driving force F.
S = f ₁ F + f ₂

The regression coefficients f ₁ and f ₂ can be calculated by, for example, a method such as the least squares method. At this time, the regression coefficients f ₁ and f ₂ may be calculated sequentially based on a large number of data sets of the slip ratio S and the driving force F, or may be calculated by batch processing. In this embodiment, the sequential least squares method is used as a preferred example. In step S10, the driving force F included in a large number of data sets is sufficiently dispersed. Therefore, based on such a large number of data sets, the regression coefficient f ₁ representing the linear relationship between the slip ratio S and the driving force F and f ₂ can be calculated correctly.

On the other hand, step S11 and subsequent steps S12 to S14 are executed when it is determined that the variation of the driving force F is not equal to or more than a certain value in the most recent predetermined period, in other words, when the driving force F has not changed so much. Will be done. In such a case, even if the regression coefficients f ₁ and f ₂ are calculated from a large number of data sets in the latest period, those regression coefficients f ₁ and f ₂ are linear with the slip ratio S and the driving force F. It may not be a reasonable value for the relationship. However, even in such a case, if the intercept f ₂ has already appeared, it is possible to calculate the _{regression coefficient f 1} representing a valid linear relationship.

More specifically, as shown in FIG. 5, a linear relationship between the slip ratio S and the driving force F, although varies depending on the state of the road surface, it is only the slope f ₁ to vary. That is, _{the slip ratio S when the intercept f 2} , that is, when the driving force F = 0 is substantially constant regardless of the state of the road surface. Therefore, even if a large number of data sets for driving force F with sufficiently variation cannot be obtained, if such an intercept f ₂ has already appeared, at least one data set at the time of determining the road surface condition (F, Based on S), a reasonable slope f ₁ can be calculated. Therefore, in step S11, the tilt calculating section 28 determines whether intercept f ₂ is the foregoing, if the intercept f ₂ is the already, the process proceeds to step S12. On the other hand, if the intercept f ₂ has not already appeared, the determination of the road surface condition at the current time (step S15) is omitted, and the process returns to step S1.

In step S12, the inclination calculation unit 28 determines whether or not the absolute value of the current driving force F at the time of determining the state of the road surface is equal to or higher than a certain value, and if it is determined to be equal to or higher than a certain value, the inclination calculation unit 28 determines. The process proceeds to step S13. In step S13, the inclination calculation unit 28 calculates the inclination f ₁ based on the data set of the current slip ratio S and the driving force F at the time of determining the state of the road surface and the already-existing intercept f _2, and steps. Proceed to S14. The slope f ₁ is calculated according to the following equation. The slope f ₁ calculated here is distinguished from the _{slope f 1} calculated in step S10 or the next step S14 described later, and is expressed as _{f 1'.}
f ₁ '= (S-f ₂ ) / F

By the way, when the absolute value of the current driving force F at the time of determining the road surface condition is not equal to or more than a certain value, the current data set (F, S) and the _{point represented by the intercept f 2} (0, f). since the distance between ₂₎ are close, there is a risk that can not be calculated reasonable slope f ₁ '. Therefore, in the present embodiment, when it is determined in step S12 that the absolute value of the driving force F is not equal to or more than a certain value, the determination of the road surface condition at the current time (step S15) is omitted, and the process returns to step S1. ..

In step S14, the tilt calculating section 28, according to the following equation, the gradient f ₁ ', by combining with a weight and a most recent inclination f _1, calculates an inclination f ₁ used for determining the state of the road surface .. Here, r is a weighting coefficient for combining the current tilt f ₁ 'and inclination f ₁ calculated in the past.
f ₁ = (1-r) f ₁ + rf ₁ '

In the next step S15, the determination unit 29 based on the inclination f ₁ calculated in step S10 or step S14, determines the state of the road surface. The determination unit 29 _{compares the inclination f 1} with a predetermined threshold value, and if it is equal to or higher than the threshold value, hydroplaning or the like is likely to occur, and the determination unit 29 determines that the road surface is in a slippery state. At this time, for example, the determination unit 29 causes the driver to display an alarm on the display 3 indicating that the road surface is in a slippery state. Further, the determination unit 29 _{calculates an index indicating slipperiness according to the inclination f 1} , and passes the index to various control processes executed on the control unit 2. Examples of the control referred to here include brake control when the vehicle is running, control of the inter-vehicle distance, and the like.

When step S15 is completed, the process returns to step S1. According to the above method, it is possible to calculate a slip ratio S that is appropriate for executing various controls, and by extension, a regression coefficient (slope f ₁ ) that is appropriate for executing various controls. The condition of the road surface can be stably determined.

<2. Modification example>
Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the following changes can be made. In addition, the gist of the following modified examples can be combined as appropriate.

<2-1>
The function of determining the slip ratio S and the road surface condition based on the slip ratio S according to the above embodiment can be applied to a rear-wheel drive vehicle and can also be applied to a four-wheel drive vehicle. Further, the same function can be appropriately applied not only to a four-wheeled vehicle but also to a three-wheeled vehicle or a six-wheeled vehicle.

<2-2>
In the above embodiment, in step S5, any one of the three slip ratios S of the first slip ratio, the second slip ratio and the third slip ratio is selected, but the two slip ratios of the first slip ratio and the second slip ratio. Any of the slip ratio S may be selected. More specifically, as described above, when going straight, there is no significant difference in the _{inclination f 1} depending on either the first slip ratio or the second slip ratio. Therefore, as the slip ratio when traveling straight, either the first slip ratio or the second slip ratio may be selected instead of the third slip ratio.

<2-3>
The method for acquiring the lateral acceleration γ of the vehicle 1 is not limited to that described in the above embodiment. For example, the lateral acceleration γ can be obtained from the information of the yaw rate ω and the rotation speeds V1 to V4 from the yaw rate sensor 8.

<2-4>
In the above embodiment, the relational information is specified every time the vehicle travels, but the relational information may be derived in advance and referred to when the slip ratio S is corrected.

<2-5>
The method for calculating the slip ratio S is not limited to that described in the above embodiment. For example, when the slip ratio S = (driving wheel speed − vehicle body speed) / vehicle body speed is defined, the slip ratio S may be calculated by integrating the vehicle body speed with the acceleration α acquired by the acceleration sensor 7. good.

<2-6>
The method of acquiring the driving force F is not limited to that described in the above embodiment. For example, the driving force F can be derived from the output value of the wheel torque sensor attached to the vehicle 1, or can be derived from the engine torque and the engine speed obtained from the control device of the engine of the vehicle 1. It can also be derived from the tire rotation speeds V1 to V4.

<2-7>
The method of acquiring the vehicle body speed is not limited to that described in the above embodiment. For example, instead of the rotation speed of the drive wheels, it may be acquired from a satellite positioning system such as GPS that is communicatively connected to the vehicle 1.

<2-8>
In the above embodiment, the slip ratio S corrected based on the turning radius R is used for determining the state of the road surface, but the present invention is not limited to this, and can be used for various controls based on the slip ratio S.

<3. Evaluation ＞
<3-1. Evaluation 1>
The vehicle was actually driven, measurement data was collected, the vehicle body speed was acquired, and as simulation example 1, the inclination f ₁ was calculated by the same method as in the first embodiment. For reference simulation example 1, from the process of simulation Example 1, by the method is omitted calculated slope f ₁ when the variation of the driving force F is less than a predetermined value, the same measurement data and simulation example 1, the slope f ₁ was calculated. The result at this time is shown in FIG. The horizontal axis of FIG. 8 is time. According to FIG. 8, generally becomes constant vehicle speed in downhill, in a period in which the driving force is substantially reduced to zero, the gradient f ₁ which can not be calculated in the process according to Reference simulation example 1, the method of the simulation example 1 According to it, it can be calculated. Incidentally, the number of valid data tilt f ₁ by simulation example 1, was the 10524 pieces, the number of valid data tilt f ₁ by Reference Simulation Example 1 was 6331 pieces. Therefore, according to Simulation Example 1, it was confirmed that the road surface condition can be stably determined even on a downhill or the like.

<3-2. Evaluation 2>
The vehicle was actually driven to collect measurement data, and as simulation example 2, correction was performed based on the turning radius R in the same manner as in the first embodiment, and a large number of slip ratio S data were acquired. Further, as a reference simulation example 2, a large number of slip ratio S data were acquired from the same measurement data as in the simulation example 2 by a method in which the correction based on the turning radius R was omitted from the method of the simulation example 2. Then, in each case, the values of the driving force F and the slip ratio S were plotted for each predetermined range of the lateral acceleration γ. The result is shown in FIG. In each graph of FIG. 9, the horizontal axis represents the driving force and the vertical axis represents the slip ratio. From FIG. 9, when the correction based on the turning radius R is not performed, there are some places where the linearity between the driving force F and the slip ratio S is broken, such as the places surrounded by circles in the figure. On the other hand, when the correction is performed based on the turning radius R, such a collapse of linearity is suppressed. Therefore, it was confirmed that a more appropriate slip ratio S for use in determining the state of the road surface or the like can be calculated by correcting the slip ratio S based on the turning radius R.

<3-3. Evaluation 3>
A vehicle is actually driven on a road in which the road surface condition is generally stable, measurement data is collected, lateral acceleration γ is acquired, and as a simulation example 3, a large number of inclinations f are performed by the same method as in the first embodiment. ₁ was calculated. Further, as a reference simulation example 3 _{, a large number of slopes f 1} were calculated from the same measurement data as in the simulation example 3 by a method of _{always calculating the slope f 1 based on the third slip ratio.} The results at this time are shown in FIGS. 10A and 10B. FIG. 10A is a graph based on measurement data mainly when traveling in a left turn, and FIG. 10B is a graph based on measurement data mainly when traveling in a right turn. The horizontal axis of each graph of FIGS. 10A and 10B is time. _{Further, the slope f 1} when traveling straight, which is shown in each graph of FIGS. 10A and 10B, is a value calculated from a third slip ratio based on measurement data when traveling on a course including a straight line. According to FIGS. 10A and 10B, when the lateral acceleration γ is greatly applied, the inclination f ₁ fluctuates in both the simulation example 3 and the reference simulation example 3, but in the simulation example 3, the inclination f _{1 is higher than that in the reference simulation example 3.} Fluctuations are suppressed. Therefore, it was confirmed that by selecting the slip ratio according to the lateral acceleration γ, a more appropriate inclination f ₁ for use in determining the state of the road surface or the like can be calculated.

1 Vehicle 2 Control unit (judgment device)
3 Display 4 Lateral acceleration sensor 6 Wheel speed sensor 7 Accelerometer 8 Yaw rate sensor 9 Program 21 Rotation speed acquisition unit 22 Driving force acquisition unit 23 Lateral acceleration acquisition unit 24 Turning radius acquisition unit 25 Slip ratio calculation unit 26 Relationship identification unit 27 Correction unit 28 Tilt calculation unit 29 Judgment unit FL Left front wheel FR Right front wheel RL Left rear wheel RR Right rear wheel V1 to V4 Tire rotation speed

Claims (7)

It is a judgment device that determines the condition of the road surface on which the vehicle travels.
A rotation speed acquisition unit that sequentially acquires the rotation speed of the tires mounted on the vehicle, and a rotation speed acquisition unit.
A lateral acceleration acquisition unit that sequentially acquires lateral acceleration applied to the vehicle, and a lateral acceleration acquisition unit.
Of the rotational speeds of the tires that are sequentially acquired according to the lateral accelerations that are sequentially acquired, the first slip ratio, which is the slip ratio of the tires calculated based on the rotational speed of the left tire, and the right one. A slip ratio calculation unit that sequentially selects and acquires any one from the group including the second slip ratio, which is the slip ratio of the tire calculated based on the rotation speed of the tire, and
A driving force acquisition unit that sequentially acquires the driving force of the vehicle,
As a regression coefficient representing the linear relationship between the slip ratio and the driving force, a slope calculation unit that calculates the slope of the slip ratio with respect to the driving force based on a large number of data sets of the slip ratio and the driving force.
A determination unit for determining the state of the road surface based on the inclination is provided.
Judgment device. The slip ratio calculation unit selects the first slip ratio when the vehicle turns to the right and the second slip ratio when the vehicle turns to the left, according to the lateral acceleration.
The determination device according to claim 1. The slip ratio calculation unit rotates the left and right tires among the first slip ratio, the second slip ratio, and the rotational speeds of the tires sequentially acquired according to the lateral accelerations acquired sequentially. One of the groups including the third slip ratio, which is the slip ratio of the tire calculated based on the average speed, is sequentially selected and acquired.
The determination device according to claim 1 or 2. The slip ratio calculation unit responds to the lateral acceleration with respect to the first slip ratio when the vehicle turns to the right, the second slip ratio when the vehicle turns to the left, and the third slip ratio when the vehicle goes straight. Select the slip ratio,
The determination device according to claim 3. The inclination calculation unit calculates the inclination by sequential or batch processing based on a large number of data sets of the slip ratio and the driving force.
The determination device according to any one of claims 1 to 4. It is a judgment method for judging the condition of the road surface on which the vehicle travels.
Acquiring the rotational speeds of the tires mounted on the vehicle in sequence,
Acquiring the lateral acceleration applied to the vehicle in sequence and
Of the rotational speeds of the tires that are sequentially acquired according to the lateral accelerations that are sequentially acquired, the first slip ratio, which is the slip ratio of the tires calculated based on the rotational speed of the left tire, and the right one. One of the groups including the second slip ratio, which is the slip ratio of the tire calculated based on the rotation speed of the tire, is sequentially selected and acquired.
Acquiring the driving force of the vehicle in sequence and
As a regression coefficient representing the linear relationship between the slip ratio and the driving force, the slope of the slip ratio with respect to the driving force is calculated based on the slip ratio and a large number of data sets of the driving force.
A determination method including determining the state of the road surface based on the inclination. It is a judgment program that determines the condition of the road surface on which the vehicle travels.
Acquiring the rotational speeds of the tires mounted on the vehicle in sequence,
Acquiring the lateral acceleration applied to the vehicle in sequence and
Of the rotational speeds of the tires that are sequentially acquired according to the lateral accelerations that are sequentially acquired, the first slip ratio, which is the slip ratio of the tires calculated based on the rotational speed of the left tire, and the right one. One of the groups including the second slip ratio, which is the slip ratio of the tire calculated based on the rotation speed of the tire, is sequentially selected and acquired.
Acquiring the driving force of the vehicle in sequence and
As a regression coefficient representing the linear relationship between the slip ratio and the driving force, the slope of the slip ratio with respect to the driving force is calculated based on the slip ratio and a large number of data sets of the driving force.
A determination program that causes a computer to determine the state of the road surface based on the inclination.

Images