JP2021109540A - Determination device of slip ratio of tire - Google Patents

Abstract

To achieve various kinds of stable control based on a slip ratio, by canceling affection caused by load movement of a vehicle body in turning in a lateral direction, on the basis of a slip ratio of tires attached to the vehicle.SOLUTION: There is provided a determination device for determining a slip ratio of tires attached to a vehicle in traveling. The determination device comprises: a drive force acquiring part for acquiring drive force of the vehicle; a rotation speed acquiring part for acquiring rotation speed of the tire; a slip ratio calculating part for calculating a slip ratio of tires on the basis of the rotation speed; a lateral acceleration acquiring part for acquiring lateral acceleration applied to the vehicle; and a correcting part for correcting the slip ratio, on the basis of relationship information indicating a relationship among the lateral acceleration, the drive force, and the slip ratio, and the lateral acceleration and drive force in correction time.SELECTED DRAWING: Figure 3

Description

The present invention relates to a determination device, method and program for determining the slip ratio of tires mounted on a traveling vehicle, and 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). For example, by specifying the regression coefficient (slope) representing this relationship, the road surface condition can be determined accordingly. Yes (for example, Patent Documents 1 and 2 etc.).

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. It should be noted that the loss of the linear relationship between the slip ratio and the driving force during turning of the vehicle is not limited to the case of determining the state of the road surface, but is also a problem when some control is performed based on the slip ratio.

The present invention is a determination device capable of canceling the influence caused by the lateral load movement of the vehicle body during turning from the slip ratio of the tire mounted on the vehicle and realizing various stable controls based on the slip ratio. It is an object of the present invention to provide a method and a program, and a determination device, a method and a program capable of canceling an influence caused by a load transfer in the left-right direction of a vehicle body during turning and correctly determining a road surface condition.

The determination device according to the first aspect of the present invention is a determination device that determines the slip ratio of a tire mounted on a running vehicle, and is a determination device that acquires a driving force of the vehicle and a driving force acquisition unit of the tire. A rotation speed acquisition unit that acquires a rotation speed, a slip ratio calculation unit that calculates the slip ratio of the tire based on the rotation speed, a lateral acceleration acquisition unit that acquires the lateral acceleration applied to the vehicle, and the above. It is provided with relational information representing the relationship between the lateral acceleration, the driving force, and the slip ratio, and a correction unit that corrects the slip ratio based on the lateral acceleration and the driving force at the time of correction.

The determination device according to the second aspect of the present invention is the determination device according to the first aspect, and the relational information expresses the slip ratio as a linear function of the driving force, and the slope of the slip ratio with respect to the driving force. Is the information represented by the quadratic function of the lateral acceleration.

The determination device according to the third aspect of the present invention is the determination device according to the second aspect, and the correction unit multiplies the squared value of the lateral acceleration at the time of the correction by a coefficient included in the relational information. The slip ratio is corrected by calculating the sum of the value and a predetermined constant, calculating the product of the sum and the driving force, and subtracting the product from the slip ratio.

The determination device according to the fourth aspect of the present invention is a determination device according to any one of the first to third aspects.

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 is based on a large number of data sets of the slip ratio, the lateral acceleration, and the driving force. , Further includes a relationship specifying unit for specifying the relationship information.

The determination device according to the sixth 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 the tires mounted on the vehicle, and the rotation. A slip ratio calculation unit that sequentially calculates the slip ratio of the tires based on the speed, a lateral acceleration acquisition unit that acquires the lateral acceleration applied to the vehicle, and a driving force acquisition unit that sequentially acquires the driving force of the vehicle. And, 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. And the correction unit that corrects the inclination based on the relational information showing the relationship between the lateral acceleration and the inclination and the lateral acceleration at the time of correction, and the road surface based on the corrected inclination. It is provided with a determination unit for determining the state of.

The determination method according to the seventh aspect of the present invention is a determination method for determining the slip ratio of a tire mounted on a moving vehicle, and includes the following. Further, the determination program according to the eighth aspect of the present invention is a determination program for determining the slip ratio of tires mounted on a moving vehicle, and causes a computer to execute the following.
-Acquiring the driving force of the vehicle-Acquiring the rotation speed of the tire-Calculating the slip ratio of the tire based on the rotation speed-Acquiring the lateral acceleration applied to the vehicle- Correcting the slip ratio based on the relationship information indicating the relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction.

The determination method according to the ninth aspect of the present invention is a 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 tenth aspect of the present invention is a program for determining the state of the road surface on which the vehicle travels, and causes a computer to execute the following.
-Sequentially acquire the rotational speed of the tires mounted on the vehicle-Sequentially calculate the slip ratio of the tires based on the rotational speed-Obtain the lateral acceleration applied to the vehicle-The vehicle Acquiring the driving force sequentially-The slope of the slip ratio with respect to the driving force based on the slip ratio and a large number of data sets of the driving force as a regression coefficient representing the linear relationship between the slip ratio and the driving force. -Correcting the tilt based on the relational information representing the relationship between the lateral acceleration and the tilt and the lateral acceleration at the time of correction-Based on the corrected tilt, the said Judging the condition of the road surface

A certain relationship is established between the lateral acceleration applied to the vehicle, the driving force, and the slip ratio. According to the first aspect, the slip ratio is corrected based on this relationship and the lateral acceleration and driving force at the time of correction. Therefore, from the slip ratio of the tires mounted on the vehicle, the influence caused by the load movement in the left-right direction of the vehicle body during turning can be canceled, and various stable controls based on the slip ratio can be realized.

Further, a certain relationship is established between the lateral acceleration applied to the vehicle and the slope of the slip ratio with respect to the driving force. According to the sixth aspect, the slope of the slip ratio with respect to the driving force is corrected based on this relationship and the lateral acceleration at the time of correction. Therefore, the state of the road surface can be correctly determined based on the inclination in which the influence caused by the load movement in the left-right direction of the vehicle body during turning is canceled.

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 slip ratio which concerns on 1st Embodiment and the state of a road surface based on this. A graph showing the relationship between the slip ratio and the turning radius of the vehicle. A graph showing the relationship between the slope of the slip ratio with respect to the driving force and the lateral acceleration. A graph showing the relationship between the slip ratio and the driving force. The flowchart which shows the flow of the determination process of the slip ratio which concerns on 2nd Embodiment and the state of the road surface based on this. A graph showing the relationship between the slope of the slip ratio and the lateral acceleration with respect to the driving force according to another definition of the slip ratio. A graph showing the relationship between the slope of the slip ratio and the lateral acceleration with respect to the driving force according to another definition of the slip ratio. 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.

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. More specifically, in the present embodiment, the slip ratio S is calculated as follows by averaging the rotation speeds between the left wheel and the right wheel.
S = {(V1 + V2)-(V3 + V4)} / (V3 + V4)

In the next step S6, the slip ratio S calculated 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 and subsequent steps S8 are executed only once. After steps S7 and S8 are executed once, the process proceeds to step S9 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 S9). 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

In the next step S8, the relationship identification unit 26 determines the lateral acceleration based on a large number of data sets of the lateral acceleration γ acquired in step S3 and the slip ratio S and the driving force F filtered in step S6. The relationship information representing the relationship between γ, the driving force F, and the slip ratio S is specified. This relational information is also used for the subsequent correction of the slip ratio S (step S10). As described above, since the linear relationship between the slip ratio S and the driving force F changes while the vehicle 1 is turning, it may not be possible to correctly determine the state of the road surface. Then, during turning, this linear relationship changes from the time of straight running not only due to the difference between the left and right orbits but also due to the influence of the load movement in the left-right direction of the vehicle body. This is because the slip ratio S changes from the time of going straight due to the influence of such load movement. Therefore, here, in order to realize various stable controls based on the slip ratio S, the influence caused by the load movement in the left-right direction during turning is canceled from the slip ratio S.

The load transfer in the left-right direction during turning depends on the lateral acceleration γ, and a certain relationship is established between _{the lateral acceleration γ and the slope f 1 of the slip ratio S with respect to the driving force F.} According to the experiment conducted by the present inventor, the slope f ₁ is generally represented by a quadratic function of the lateral acceleration γ as shown in FIG. _{In step S8, the relationship specifying unit 26 uses the coefficients a 2} , b ₂ , c ₂ and f ₂ in the following equations as the relationship information representing the relationship between the lateral acceleration γ, the driving force F and the slip ratio S. Identify. Note that f ₂ is an intercept of the slip ratio S with respect to the driving force F, and is a substantially constant value as described later.
S = f ₁ F + f ₂ = (a ₂ γ ² + b ₂ γ + c ₂ ) F + f ₂

The coefficients a ₂ , b ₂ , c ₂ and f ₂ are calculated based on a large number of data sets of slip ratio S, driving force F and lateral acceleration γ, and are calculated by, for example, a method such as the least squares method. Further, the range of the lateral acceleration γ is divided into arbitrary ranges, the first-order regression of the slip ratio S and the driving force F is performed _{in each range, the regression coefficients f 1} and f ₂ are calculated, and then the lateral acceleration in each range. It is also possible to calculate the average value of γ and the average value of the slope f ₁ , and to specify the _{coefficients a 2} , b ₂ and c ₂ by the Gauss-Jordan method based on these average values.

When step S8 is completed, the process returns to step S1 and steps S1 to S6 are repeated again. As shown in FIG. 3, is executed steps S7 and S8 once, turning radius R and the relationship information between the slip ratio S a _1, b ₁ and c _1, as well as the lateral acceleration γ driving force F and the slip ratio of S After the relationship information a ₂ , b ₂ and c ₂ are specified, each time steps S1 to S6 are executed once, steps S9 to S17 are repeatedly executed thereafter.

_{In step S9, 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 next step S10, the correction unit 27 receives the relational information a 2} , b ₂ and c ₂ indicating the relationship between the lateral acceleration γ and the slip ratio S, and the lateral acceleration γ acquired in the latest step S3. The slip ratio S acquired in step S9 is further corrected based on the driving force F acquired in the latest step S6. As described above, the slip ratio S is expressed by a linear function of the driving force F to the inclination and f _1, the slope f ₁ is represented by a quadratic function of the lateral acceleration gamma. Therefore, the correction unit 27, according to the following equation, and the value obtained by multiplying the correction time of the lateral acceleration γ coefficients a ₂ to a value obtained by squaring and a value obtained by multiplying the coefficient b ₂ in the lateral acceleration γ during correction, c _The slip ratio S is further corrected by calculating the sum with 2 and calculating the product of the sum and the driving force F at the time of correction, and subtracting the product from the slip ratio S acquired in step S9.
S = S-f ₁ F = S- (a ₂ γ ² + b ₂ γ + c ₂ ) F

Since b _{2 is} also approximately 0, the slip ratio S may be corrected according to the following equation.
S = S- (a ₂ γ ² + c ₂ ) F

According to the above correction formula, the slip ratio S converted when traveling straight can be calculated, and the influence of the load movement in the left-right direction due to the left turn and the right turn is canceled from the slip ratio S.

In the subsequent steps S11 to S17, 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. 6 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.

The regression coefficient can be calculated based on a large number of datasets of slip ratio S and 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 S11, 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 S12. 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 S13.

In step S12, 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.
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 S12, 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 S13 and subsequent steps S14 to S16 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. 6, the 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 S13, 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 S14. 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 S17) is omitted, and the process returns to step S1.

In step S14, 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 more than a certain value, and if it is determined to be equal to or more than a certain value, the inclination calculation unit 28 determines. The process proceeds to step S15. In step S15, 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 S16. The slope f ₁ is calculated according to the following equation. Incidentally, the gradient f ₁ calculated here is to distinguish the gradient f ₁ is calculated by the following step S16 to step S12 or later, 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 S14 that the absolute value of the driving force F is not equal to or higher than a certain value, the determination of the road surface condition at the current time (step S17) is omitted, and the process returns to step S1. ..

In step S16, 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 S17, the determination unit 29 based on the inclination f ₁ calculated in step S12 or step S16, 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 S17 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. Second Embodiment>
Next, the determination device according to the second embodiment will be described. However, since the determination device according to the second embodiment can be configured in the same manner as the first embodiment in terms of hardware configuration, only the determination process according to the second embodiment will be described below.

The determination process according to the second embodiment is executed according to the flowchart shown in FIG. Hereinafter, the description of the parts common to the determination process according to the first embodiment will be omitted. The difference in the determination process between the first embodiment and the second embodiment is as follows. That is, in the first embodiment, the slip ratio S is corrected based on the relationship between the lateral acceleration γ, the driving force F, and the slip ratio S (step S10), and the slope f ₁ is calculated based on the corrected slip ratio S. On the other hand, in the second embodiment _{, the slope f 1} is corrected based on the relationship between the _{slope f 1} and the lateral acceleration γ shown in FIG.

Specifically, step S21 is executed instead of step S8, and step S10 is omitted. According to the experiment conducted by the present inventor, as described above, a certain relationship is established between the _{lateral acceleration γ and the inclination f 1.} More specifically, as _{shown in FIG. 5, the slope f 1} is generally represented by a quadratic function of the lateral acceleration γ. In step S21, the relationship specifying unit 26 returns as relationship information representing the linear relationship between the driving force F and the slip ratio S based on a large number of data sets of the slip ratio S and the driving force F filtered in step S6. Calculate the coefficient (slope f _1). At this time, the relationship specifying unit 26 _{calculates a large number of slopes f 1} , and specifies the lateral acceleration γ that gives the _{slopes f 1} for each slope f 1. As a result, _{a large number of data sets of the slope f 1} and the lateral acceleration γ are acquired. At this time, the regression coefficient f ₁ may be calculated sequentially or by batch processing based on a large number of data sets of the slip ratio S and the driving force F.

_{Subsequently, the relationship specifying unit 26 uses the coefficients a 2} and b of the following equations as the relationship information representing the relationship between the lateral acceleration γ and the slope f ₁ based on these a large number of data sets (γ, f _1). Identify ₂ and c _2.
f ₁ = a ₂ γ ² + b ₂ γ + c ₂

The coefficients a ₂ , b ₂ and c ₂ are calculated by, for example, a method such as the least squares method, based on a large number of data sets of lateral acceleration γ and slope f _1. Further, the range of the lateral acceleration γ is divided into arbitrary ranges, the average value of the lateral acceleration γ and the average value of the slope f ₁ are calculated in each range, and the coefficient is calculated by the Gauss-Jordan method based on these average values. It is also possible to identify a ₂ , b ₂ and c _2.

_{From the above, the coefficients a 2} , b ₂ and c ₂ are specified as the relationship information representing the relationship between the lateral acceleration γ and the slope f _1. This relationship information is used to step S22 to perform the subsequent correction of the slope f _1. Step S22 is executed in order to correct the _{inclination f 1} after calculating the inclination f 1 in steps S12 and S16.

In step S22, the correction unit 27 _{tilts according to the following equation based on the coefficients a 2} , b ₂ and c ₂ representing the relationship between the _{lateral acceleration γ and the inclination f 1,} and the lateral acceleration γ at the time of correction. Correct f _1.
f ₁ = f ₁ −a ₂ γ ² −b ₂ γ

Since b _{2 is} also approximately 0, the slope f ₁ may be corrected according to the following equation.
f ₁ = f ₁ −a ₂ γ ²

After that, the process proceeds to step S17, and the determination unit 29 determines the state of the road surface based on _{the inclination f 1 corrected in step S22, as in the first embodiment.} Also by this method, as in the first embodiment, the influence caused by the load movement in the left-right direction during turning can be substantially canceled from the slip ratio S, and various stable controls based on the slip ratio S are realized. can do.

<3. 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.

<3-1>
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.

<3-2>
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.

<3-3>
In the above embodiment, the relationship information, have been identified in every travel of the vehicle, in advance derive the relationship information may be referring to this at the correction of the slip ratio S or tilt f _1.

<3-4>
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.

Further, the slip ratio S does not average the rotation speed between the left wheel and the right wheel as in the above embodiment, but only the rotation speeds V1 and V3 of the left wheel or the right wheel as shown below. It can also be calculated based only on the rotation speeds V2 and V4. The following formula is based on the premise that the vehicle is a front-wheel drive vehicle, as in the first embodiment.
S = (V1-V3) / V3
S = (V2-V4) / V4

However, when defined as in the above equation, _{the relationship between the inclination f 1} and the lateral acceleration γ changes as shown in FIGS. 8A and 8B. According to the experiments performed by the present inventor, the graphs shown in FIGS. 8A and 8B are approximately approximated to cubic functions. Even in such a case, by specifying such a relationship, the slip ratio S or the slope f ₁ can be corrected as in the first and second embodiments.

<3-5>
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.

<3-6>
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.

<3-7>
In the above embodiment, the slip ratio S corrected based on the lateral acceleration γ and the turning radius R is used for determining the state of the road surface, but is not limited to this, and is used for various controls based on the slip ratio S. Can be done.

<4. Evaluation ＞
<4-1. 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. 9 is time. According to FIG. 9, substantially 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.

<4-2. 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. 10, the horizontal axis represents the driving force and the vertical axis represents the slip ratio. From FIG. 10, 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.

<4-3. Evaluation 3>
The vehicle is actually driven on a road where the road surface condition is generally stable, measurement data is collected, the vehicle body speed and the lateral acceleration γ are acquired, and as a simulation example 3, the inclination is performed in the same manner as in the first embodiment. f ₁ was calculated. Further, as a reference simulation example 3, a large number of data having _{a slope f 1} were acquired from the same measurement data as in the simulation example 3 by a method in which the correction based on the lateral acceleration γ was omitted from the method of the simulation example 3. The result at this time is shown in FIG. The horizontal axis of each graph in FIG. 1 is time. According to FIG. 11, when the lateral acceleration γ is greatly applied, the inclination f ₁ fluctuates greatly in the reference simulation example 3, whereas the fluctuation of _{the slope f 1 is suppressed in the simulation example 3.} Therefore, it was confirmed that by correcting the slip ratio S based on the lateral acceleration γ, a more appropriate slip ratio S 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 (10)

A determination device that determines the slip ratio of tires mounted on a moving vehicle.
A driving force acquisition unit that acquires the driving force of the vehicle,
A rotation speed acquisition unit that acquires the rotation speed of the tire, and a rotation speed acquisition unit.
A slip ratio calculation unit that calculates the slip ratio of the tire based on the rotation speed,
A lateral acceleration acquisition unit that acquires the lateral acceleration applied to the vehicle, and a lateral acceleration acquisition unit.
A determination including a relational information representing the relationship between the lateral acceleration, the driving force, and the slip ratio, and a correction unit for correcting the slip ratio based on the lateral acceleration and the driving force at the time of correction. Device. The relational information is information in which the slip ratio is represented by a linear function of the driving force, and the slope of the slip ratio with respect to the driving force is represented by a quadratic function of the lateral acceleration.
The determination device according to claim 1. The correction unit calculates the sum of the value obtained by multiplying the squared lateral acceleration at the time of the correction by the coefficient included in the relational information and a predetermined constant, and calculates the product of the sum and the driving force. The slip ratio is corrected by calculating and subtracting the product from the slip ratio.
The determination device according to claim 2. The driving force acquisition unit sequentially acquires the driving force, and the driving force acquisition unit sequentially acquires the driving force.
The rotation speed acquisition unit sequentially acquires the rotation speed, and the rotation speed acquisition unit sequentially acquires the rotation speed.
The slip ratio calculation unit sequentially calculates the slip ratio based on the rotational speeds that are sequentially acquired.
The lateral acceleration acquisition unit sequentially acquires the lateral acceleration, and the lateral acceleration acquisition unit sequentially acquires the lateral acceleration.
The correction unit sequentially corrects the slip ratio based on the relational information, the lateral acceleration at the time of the correction, and the driving force.
The determination device is
As a regression coefficient representing the linear relationship between the corrected slip ratio and the driving force, the corrected slip ratio to the driving force is based on the corrected slip ratio and a large number of data sets of the driving force. The tilt calculation unit that calculates the tilt and the tilt calculation unit
A determination unit for determining the state of the road surface based on the inclination is further provided.
The determination device according to any one of claims 1 to 3. A relationship specifying unit that specifies the relationship information is further provided based on a large number of data sets of the slip ratio, the lateral acceleration, and the driving force.
The determination device according to any one of claims 1 to 4. 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 slip ratio calculation unit that sequentially calculates the slip ratio of the tire based on the rotation speed,
A lateral acceleration acquisition unit that acquires the lateral acceleration applied to the vehicle, and a lateral acceleration acquisition unit.
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 correction unit that corrects the inclination based on the relational information indicating the relationship between the lateral acceleration and the inclination and the lateral acceleration at the time of correction.
A determination device including a determination unit that determines the state of the road surface based on the corrected inclination. It is a judgment method for determining the slip ratio of tires mounted on a running vehicle.
Acquiring the driving force of the vehicle and
Acquiring the rotational speed of the tire
To calculate the slip ratio of the tire based on the rotation speed,
Acquiring the lateral acceleration applied to the vehicle and
A determination method including correcting the slip ratio based on the relational information representing the relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction. .. It is a judgment program that determines the slip ratio of tires mounted on a running vehicle.
Acquiring the driving force of the vehicle and
Acquiring the rotational speed of the tire
To calculate the slip ratio of the tire based on the rotation speed,
Acquiring the lateral acceleration applied to the vehicle and
A computer is made to correct the slip ratio based on the relational information showing the relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction. , Judgment program. 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,
The slip ratio of the tire is sequentially calculated based on the rotation speed, and
Acquiring the lateral acceleration applied to the vehicle and
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.
Correcting the inclination based on the relational information showing the relationship between the lateral acceleration and the inclination and the lateral acceleration at the time of correction.
A determination method including determining the state of the road surface based on the corrected 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,
The slip ratio of the tire is sequentially calculated based on the rotation speed, and
Acquiring the lateral acceleration applied to the vehicle and
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.
Correcting the inclination based on the relational information showing the relationship between the lateral acceleration and the inclination and the lateral acceleration at the time of correction.
A determination program that causes a computer to determine the state of the road surface based on the corrected inclination.

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