WO2016006233A1 - Drive control system, automobile, and drive control method - Google Patents

Abstract

A drive control system (10) according to the present invention is provided with: a measuring sensor (11) that takes measurements related to the viscoelastic properties of the tires of an automobile; a viscoelastic property calculating unit (12) that calculates the viscoelastic properties of the tires by using the measurements taken by the measuring sensor (11); a friction coefficient calculating unit (13) that calculates the friction coefficients of the tires by using the viscoelastic properties calculated by the viscoelastic property calculating unit (12); and a drive control unit (14) that controls driving of the automobile on the basis of the friction coefficients of the tires calculated by the friction coefficient calculating unit (13).

Description

Driving control device, automobile and driving control method

The present invention relates to an operation control device, an automobile, and an operation control method, and more particularly to an operation control device, an automobile, and an operation control method for controlling the operation of an automobile based on a friction coefficient of a tire.

In a car, a decrease in the grip force of a tire can be a factor that causes unstable running such as slipping. Therefore, a technique for controlling the traveling of the automobile according to the grip force of the tire has been proposed.

For example, Patent Document 1 discloses a technique for slowly decelerating an automobile during turning when the grip state of the tire is close to the limit of turning performance. Here, the grip state of the tire is estimated to be closer to the limit of turning performance as the slip ratio of the wheel is higher. Patent Document 2 discloses a technique for controlling a transmission gear ratio when a tire grip force is reduced. As a technique related to a tire, Patent Document 3 discloses a technique for measuring friction characteristics in a viscoelastic body such as a tire.

JP 2006-281935 A JP 2014-39449 A JP 2007-47130 A

The grip force of automobile tires is reduced not only due to road surface conditions, but also due to deterioration of the tire itself (particularly, a reduction in the friction coefficient of the tire). Therefore, measuring the deterioration of the tire is important for safely controlling the running of the automobile.

In the technique described in Patent Document 1 described above, although the grip state of the tire is estimated based on the slip ratio of the wheel, the deterioration of the tire is not directly measured. Therefore, even when the tire is deteriorated, it is not determined that the grip state of the tire is close to the limit of the turning performance, and the automobile may not be slowly decelerated during the turning. Further, Patent Document 2 does not specifically describe a method for measuring a decrease in the grip force of a tire.

The present invention has been made to solve such problems, and provides a driving control device, a car, and a driving control method capable of controlling driving of a car by appropriately reflecting deterioration of a tire. The purpose is to do.

The operation control apparatus according to the first aspect of the present invention includes a measurement sensor, a viscoelastic characteristic calculation unit, a friction coefficient calculation unit, and an operation control unit. The measurement sensor measures a measurement amount related to viscoelastic characteristics of the tire of the automobile. A viscoelastic characteristic calculation part calculates the viscoelastic characteristic of a tire using the measured quantity which the measurement sensor measured. The friction coefficient calculating unit calculates the friction coefficient of the tire using the viscoelastic characteristic calculated by the viscoelastic characteristic calculating unit. The driving control unit controls driving of the automobile based on the tire friction coefficient calculated by the friction coefficient calculating unit.

The vehicle driving control method according to the second aspect of the present invention includes the following steps (a) to (d).
(A) a measurement step for measuring a measurement amount relating to viscoelastic characteristics of an automobile tire;
(B) a viscoelastic characteristic calculating step for calculating a viscoelastic characteristic of the tire using the measured amount;
(C) a friction coefficient calculating step for calculating the friction coefficient of the tire using the calculated viscoelastic property, and (d) an operation control step for controlling the driving of the vehicle based on the calculated tire friction coefficient.

As described above, in the present invention, in order to control the driving of the automobile, the viscoelastic characteristics of the tire of the automobile are actually measured, and the friction coefficient of the tire is calculated using the measured viscoelastic characteristics. Therefore, the technology according to the present invention can accurately measure the deterioration of the tire and control the driving of the automobile based on the measurement result.

According to the present invention, it is possible to provide a driving control device, a car, and a driving control method capable of appropriately controlling the driving of the automobile by reflecting the deterioration of the tire.

1 is a block diagram illustrating a configuration example of an automobile equipped with an operation control apparatus according to a first embodiment. FIG. 3 is a block diagram illustrating a configuration example of a measurement sensor and a viscoelastic property calculation unit according to the first embodiment. It is the figure which showed an example which provided the measurement sensor in the tire of the motor vehicle in Embodiment 1. FIG. 6 is a diagram for explaining a method of calculating viscoelastic characteristics in Embodiment 1. FIG. 6 is a diagram for explaining a method of calculating viscoelastic characteristics in Embodiment 1. FIG. FIG. 3 is a block diagram illustrating a configuration example of a friction coefficient calculation unit according to the first embodiment. 3 is a flowchart illustrating an example of processing of the operation control apparatus according to the first embodiment. 10 is a diagram for explaining a method for calculating viscoelastic characteristics in Embodiment 3. FIG. 10 is a diagram for explaining a method for calculating viscoelastic characteristics in Embodiment 3. FIG. In Embodiment 3, it is the table | surface which illustrated about the acoustic impedance and reflectance in two cases of the tire T. FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, each element of the automobile described in the following figure as a functional block for performing various processes can be configured by hardware and a circuit such as a memory or other IC (Integrated Circuit). Can be realized by a program loaded in a memory.

[Embodiment 1]
FIG. 1 is a block diagram illustrating a configuration example of an automobile 1 according to the first embodiment. The automobile 1 includes a driving control device 10, a radar sensor 15, a drive unit 16, a brake unit 17, a steering unit 18, and a display unit 19.

The operation control device 10 is a device that is mounted on the automobile 1 and controls the operation of the automobile 1. In detail, the operation control apparatus 10 includes a measurement sensor 11, a viscoelastic characteristic calculation unit 12, a friction coefficient calculation unit 13, and an operation control unit 14. Hereinafter, each part of the operation control apparatus 10 will be described.

The measurement sensor 11 measures a measurement amount related to the viscoelastic characteristics of the tire of the automobile 1 (not shown in FIG. 1). The tire measured by the measurement sensor 11 may be any one of a plurality of (for example, four) tires included in the automobile 1 or may be a plurality of tires. Further, the portion of the tire measured by the measurement sensor 11 may be any portion of the tire. However, in order to accurately determine the friction deterioration, it is more preferable to measure the tread portion of the tire. The viscoelastic property calculation unit 12 calculates the viscoelastic property of the tire using the measurement amount measured by the measurement sensor 11.

FIG. 2 is a block diagram illustrating a configuration example of the measurement sensor 11 and the viscoelastic property calculation unit 12. The measurement sensor 11 includes a sound wave signal generation unit 20 and a contact unit 21. The sound wave signal generation unit 20 generates an electric signal of incident sound waves and outputs the generated electric signal to the contact unit 21. This incident sound wave is a sound wave signal incident on the tire T, and is used to calculate the viscoelastic characteristics of the tire T. In addition, the sound wave signal generation unit 20 receives the electric signal of the reflected sound wave acquired by the contact unit 21 and outputs the received electric signal to the viscoelastic characteristic calculation unit 12. This reflected sound wave is a sound wave that is generated when the incident sound wave is reflected by the tire T. The contact unit 21 contacts the tire T of the automobile, radiates the incident sound wave generated by the sound wave signal generation unit 20 to the tire T, and acquires the reflected sound wave.

The sound wave signal generation unit 20 includes a drive waveform generator 22, a direction matching unit 23, and a high frequency amplifier 24 in detail. Hereinafter, each part will be described.

The drive waveform generator 22 generates an electrical signal (drive waveform) for generating an incident sound wave in accordance with a sound wave emission instruction from the viscoelastic property calculation unit 12 and also directs the generated electric signal of the incident sound wave in a direction. Output to the matching unit 23. Specific examples of the incident sound wave incident on the tire T include a pulsed sound wave and a sound wave including a predetermined frequency component. Further, the drive waveform generator 22 outputs a trigger signal indicating the output timing of the generated electric signal to the high-frequency amplifier 24 when the electric signal is generated and output.

The direction matching unit 23 is connected to the drive waveform generator 22, the high frequency amplifier 24, and the transducer 25. The direction matching unit 23 outputs the electric signal of the incident sound wave supplied from the drive waveform generator 22 to the transducer 25 and outputs the electric signal of the reflected sound wave supplied from the transducer 25 to the high frequency amplifier 24. Here, the direction matching unit 23 adjusts the transmission direction of the signal so that the electric signal output from the drive waveform generator 22 is not output to the high frequency amplifier 24.

The high frequency amplifier 24 is supplied with an electric signal of a reflected sound wave from the direction matching unit 23. The high frequency amplifier 24 amplifies a high frequency component in the supplied electric signal with a predetermined amplification factor. Then, the high frequency amplifier 24 outputs the amplified electric signal to the time data memory unit 27 of the viscoelastic characteristic calculation unit 12. The high-frequency component in the electric signal amplified by the high-frequency amplifier 24 includes a measurement amount necessary for calculating the viscoelastic characteristics. The high frequency amplifier 24 starts receiving the electric signal supplied from the transducer 25 after receiving the trigger signal from the drive waveform generator 22. By this processing, the high frequency amplifier 24 does not operate during a period in which the measurement of the viscoelastic characteristics of the tire T is not performed. Therefore, unnecessary operations of the high frequency amplifier 24 can be suppressed.

Next, the contact part 21 will be described. Specifically, the contact portion 21 includes a transducer 25 and a delay material 26. Hereinafter, each part will be described.

The transducer 25 is constituted by a piezoelectric element, for example. The transducer 25 is attached so as to contact the delay member 26 and to be connected to the direction aligner 23. When the electric signal of the incident sound wave is supplied from the direction matching unit 23, the transducer 25 converts the supplied electric signal into a sound wave. This electrical signal is an electrical signal output from the drive waveform generator 22. The converted sound wave is emitted to the delay material 26. Further, when receiving the reflected sound wave from the delay material 26, the transducer 25 converts the reflected sound wave into an electrical signal and outputs the electrical signal to the direction matching unit 23.

From the above, the drive waveform generator 22, the direction matching unit 23, and the transducer 25 function as a radiating unit that outputs incident sound waves to the tire T. The direction matching unit 23, the high-frequency amplifier 24, and the transducer 25 have the incident sound waves being tire T. It can be said that it functions as a receiving unit that receives a reflected sound wave that is generated by being reflected by the laser beam.

The delay member 26 is provided so that one surface thereof is in close contact with the transducer 25 and the other surface facing the one surface is in contact with the tire T. Since the delay member 26 is arranged in this way, the incident sound wave incident from the transducer 25 is propagated to the tire T, and the reflected sound wave generated by the reflection of the incident sound wave by the tire T can be propagated to the transducer 25. it can. When the propagation length of the delay member 26 is increased, the arrival time of the sound wave is further delayed. Therefore, by increasing the propagation length of the delay member 26, it is possible to increase the time from when the transducer 25 radiates the incident sound wave to when it receives the reflected sound wave. Therefore, by increasing the propagation length of the delay member 26, the transducer 25 can be prevented from receiving the reflected sound wave while the transducer 25 is emitting the incident sound wave.

FIG. 3 is a view showing an example in which the measurement sensor 11 is provided on the tire T of the automobile. FIG. 3 shows an internal configuration diagram of the tire T. As shown in FIG. 3, the measurement amount related to the viscoelastic characteristics of the tire T can be measured by incorporating the measurement sensor 11 inside the tire T. For example, the contact portion 21 in the measurement sensor 11 is provided on the back surface of the tire T, and is preferably provided between the carcass and the tread rubber. Further, the sound wave signal generation unit 20 may be provided on a rim (wheel) of the tire T.

Referring back to FIG. 2, the viscoelastic property calculation unit 12 will be described. Specifically, the viscoelastic characteristic calculation unit 12 includes a time data memory unit 27, a reference value storage unit 28, and a calculation unit 29. Hereinafter, each part will be described.

The time waveform of the electrical signal of the reflected sound wave supplied from the high frequency amplifier 24 of the measurement sensor 11 is stored in the time data memory unit 27 at a predetermined cycle. The time data memory unit 27 can change the cycle for storing the time waveform based on the control of the calculation unit 29.

The reference value storage unit 28 stores in advance a reference value necessary for calculating the viscoelastic characteristics of the tire T. This reference value is data of an amplitude value and a phase at a frequency to be detected for viscoelastic characteristics. Details of the reference value will be described later. The calculation unit 29 reads out the reference value stored in the reference value storage unit 28.

The calculation unit 29 controls the data measurement process of the measurement sensor 11. Further, the calculation unit 29 calculates the viscoelastic characteristics of the tire T based on the reflected sound wave acquired by the measurement of the measurement sensor 11.

Specifically, when the calculation unit 29 outputs a sound wave radiation instruction to the drive waveform generator 22, the drive waveform generator 22 generates an electrical signal for generating an incident sound wave in accordance with the radiation instruction, It outputs to the direction matching device 23. In this way, the calculation unit 29 starts measurement by the measurement sensor 11.

When the measurement sensor 11 measures the tire T and the time waveform data of the reflected sound wave is stored in the time data memory unit 27, the calculation unit 29 reads the data. The calculation unit 29 performs waveform analysis processing in a frequency domain such as FFT (Fast Fourier Transformation) processing, for example, and acquires an amplitude value and a phase at a frequency to be detected. In addition, the frequency used as a detection object may be one, and plural may be sufficient as it. Next, the calculation unit 29 reads the reference value stored in the reference value storage unit 28, and the reference value and the amplitude value and phase at the frequency that is the detection target of the reflected sound wave stored in the time data memory unit 27. Based on the above, viscoelastic characteristics of the tire T are calculated.

<Calculation method of viscoelastic properties>
Next, the case where the measurement sensor 11 and the viscoelastic property calculation unit 12 calculate the high frequency viscoelastic property of the tire T will be described. Specifically, when the measurement sensor 11 radiates an incident sound wave to the tire T, the incident sound wave is reflected by the inner surface of the tread of the tire T to generate a reflected sound wave. The inner surface of the tread is a surface opposite to the outer surface of the tread that is in contact with the ground. Based on the reflected sound wave, the viscoelastic characteristic calculation unit 12 calculates the viscoelastic characteristic (particularly loss tangent) on the inner surface of the tread from the complex acoustic impedance that is the acoustic characteristic of the tread. This calculation method is referred to as a surface reflection method (see, for example, Patent Document 2).

4A and 4B are diagrams illustrating a method for calculating viscoelastic characteristics using this surface reflection method. FIG. 4A is a diagram illustrating a reflection state of an incident sound wave when obtaining a reference value, and FIG. 4B is a diagram illustrating a reflection state of the incident sound wave when calculating a viscoelastic characteristic of the tire T. In the following description, acoustic impedance representing the propagation characteristics of incident sound waves radiated from the transducer 25 of the measurement sensor 11 is used.

First, the reference value will be described with reference to FIG. 4A. The reference values are the phase and amplitude values at the frequency to be measured when the surface of the retarder 26 opposite to the surface on which the transducer 25 is in contact is not in contact with the tire T. At this time, the incident sound wave is reflected at the boundary surface between the end of the delay member 26 and the air. When the frequency of the incident sound wave and the reflected sound wave is f, the acoustic impedance of the delay material 26 can be expressed as Z _R (f) that is a function of the frequency f. Similarly, the acoustic impedance in the air can also be expressed as Z _A (f) that is a function of the frequency f. Here, the acoustic impedances Z _R (f) and Z _A (f) are complex values.

The reflectance R _AR (f) of the incident sound wave at the interface between the retarder 26 and the air is R _AR (f) = (Z _A (f) −Z _R (f)) / (Z _A (f) + Z _R (F)) ... (1)
It becomes. At this time, since Z _A (f) is sufficiently smaller than Z _R (f) at an arbitrary frequency f, the reflectance R _AR (f) = − 1 from Equation (1). That is, the incident sound wave is totally reflected at the boundary surface between the delay member 26 and the air.

In the following description, the expression of the reflected sound wave incident on the transducer 25 is represented as a ₀ (f) exp (iθ ₀ (f)). i is an imaginary unit, a ₀ (f) is a real amplitude value at a target frequency, and θ ₀ (f) is a real number of 0 or more, and represents a phase at each frequency. The formula of the incident sound wave radiated from the measurement sensor 11 to the tire T is
a ₀ (f) exp (iθ ₀ (f)) × R _AR (f) = − a ₀ (f) exp (iθ ₀ (f)) (2)
It becomes. Therefore, in FIG. 4A, it can be considered that the incident sound wave shown to Formula (2) is radiated | emitted to the tire T. FIG. In the reference value storage unit 28, the amplitude a ₀ (f) and the phase θ ₀ (f) in Expression (2) are stored in advance as reference values. This reference value a ₀ (f) is acquired by measuring in advance.

Next, the case where the viscoelastic characteristics of the tire T are calculated will be described with reference to FIG. 4B. When calculating the viscoelastic characteristics of the tire T, an electric signal is output from the drive waveform generator 22 in a state where the delay member 26 is in close contact with the tire T, so that the same incident sound wave as in FIG. Is emitted. The transducer 25 receives the reflected sound wave reflected at the interface between the delay member 26 and the tire T, and the high frequency amplifier 24 amplifies the high frequency component in the electric signal of the reflected sound wave.

Here, when the acoustic impedance of the bulk of the tire T that is a function of the frequency f is Z _T (f), the reflectance R _RT (f) of the incident sound wave at the boundary surface between the delay member 26 and the tire T is
R _RT (f) = (Z _T (f) −Z _R (f)) / (Z _T (f) + Z _R (f)) (3)
It becomes. From Expression (3), Z _T (f) is expressed as follows.
Z _T (f) = Z _R (f) × (1 + R _RT (f)) / (1−R _RT (f)) (4)

In the following description, the expression of the reflected sound wave incident on the transducer 25 is represented as a (f) exp (iθ (f)). i is an imaginary unit, a (f) is a real amplitude value at a target frequency, and θ (f) is a real number equal to or greater than 0 and represents a phase at each frequency. Using the reference value in equation (2), the equation of the reflected sound wave is a (f) exp (iθ (f)) = − a ₀ (f) exp (iθ ₀ (f)) × R _RT (f).・ (5)
It is expressed. From the equation (5), the reflectance R _RT (f) of the incident sound wave is R _RT (f) = − (a (f) / a ₀ (f)) × exp (i (θ (f) −θ ₀ (f )) ... (6)
It is expressed. Here, Z _T (f) is obtained as follows by substituting Equation (6) into Equation (4).
Z _T (f) = Z _R (f) × (1− (a (f) / a ₀ (f)) × exp (i (θ (f) −θ ₀ (f)))) / (1+ (a ( f) / a ₀ (f)) × exp (i (θ (f) −θ ₀ (f))) (7)

Here, the storage elastic modulus of the tire T as a function of the frequency f is E ′ (f), and the loss elastic modulus of the tire T is E ″ (f). At this time, E ′ (f) and E ″ (f ) And the acoustic impedance Z _T (f) and density ρ _T of the tire T, the following relationship holds.
E ′ (f) + iE ″ (f) = Z _T (f) ² / ρ _T (8)

By substituting equation (7) into equation (8) and separating the real and imaginary components, the loss tangent tan δ (f) is calculated as follows.
tan δ (f) = E ″ (f) / E ′ (f) = {4 × (a (f) / a ₀ (f)) × (1− (a (f) / a ₀ (f)) ² ) × sin (θ (f) −θ ₀ (f))} / {(1− (a (f) / a ₀ (f)) ² ) ² −4 × (a (f) / a ₀ (f)) ² × sin ² (θ (f) −θ ₀ (f))} (9)

The storage elastic modulus E ′ (f) and the loss elastic modulus E ″ (f) are calculated as follows.
E ′ (f) = Re [Z _T (f) ² / ρ _T ] = (Z _R (f) ² / ρ _T ) × {(1− (a (f) / a ₀ (f)) ² ) ² −4 (a (f) / a ₀ (f)) ² × sin ² (θ (f) −θ ₀ (f))} / {1 + 2 (a (f) / a ₀ (f)) cos (θ ( f) −θ ₀ (f)) + (a (f) / a ₀ (f)) ² } ² (10)
E ″ (f) = Im [Z _T (f) ² / ρ _T ] = (Z _R (f) ² / ρ _T ) × {4 (a (f) / a ₀ (f)) × (1- ( a (f) / a ₀ (f)) ² ) sin (θ (f) −θ ₀ (f))} / {1 + 2 (a (f) / a ₀ (f)) cos (θ (f) −θ ₀ (f)) + (a (f) / a ₀ (f)) ² } ² (11)
Here, Re [Z _T (f) ² / ρ _T ] is a real component of Z _T (f) ² / ρ _T , and Im [Z _T (f) ² / ρ _T ] is Z _T (f) ^2. / Ρ is an imaginary component of _T.

As represented by the equations (9) to (11), the storage elastic modulus E ′ (f), the loss elastic modulus E ″ (f), and the loss tangent tan δ (f) are all a ₀ (f), θ ₀ (f) {A (f) / a ₀ (f)} (ratio of incident sound wave amplitude to reflected sound wave amplitude), {θ (f) −θ ₀ (f)} (incident sound wave phase and reflection) Therefore, the data of the electric signal of the reflected sound wave acquired at the time of measurement of the tire T with the amplitude a ₀ (f) and the phase characteristic θ ₀ (f) as reference values. The loss tangent of the tire T depends on the frequency as described above, so that the calculation unit 29 is provided for each of a plurality of frequency components. The loss tangent may be derived at the same time, or when it is necessary to calculate the loss tangent at a high frequency. , As an incident sound wave, ultrasound may be supplied from the transducer 25.

Hereinafter, returning to FIG. 1, the description of the operation control device 10 will be continued. The friction coefficient calculation unit 13 calculates the friction coefficient of the tire T using the viscoelastic characteristic of the tire T calculated by the viscoelastic characteristic calculation unit 12. For example, the friction coefficient μ (f) of the tire T, which is a function of the frequency f, is obtained by using the above loss tangent tan δ (f) and the storage elastic modulus E ′ (f).
μ (f) = α × E ′ (f) ⁿ × tan δ (f) + β (12)
It is expressed. α (> 0) and β are inherent constants that change according to the type of tire (for example, the material of the tire), and n is a predetermined real number (for example, n = −1 / 3). Note that the mathematical formula for obtaining the friction coefficient μ (f) may be other polynomials or higher order formulas using tan δ (f), not the formula (12). By determining the friction coefficient μ (f), tire deterioration can be measured. Note that the constants α and β are values obtained by conducting an experiment or the like in advance. In particular, the constants α and tan δ (f) have a large correlation with the friction coefficient during rain (wet). Needless to say, the magnitude of the friction coefficient at the time of wet is closely related to the accident rate.

FIG. 5 is a block diagram illustrating a configuration example of the friction coefficient calculation unit 13. The friction coefficient calculation unit 13 includes a constant storage unit 31 and a calculation unit 32 in detail. The constant storage unit 31 stores the above α and β. The calculation unit 32 uses the constants α and β stored in the constant storage unit 31, based on the loss tangent tan δ (f) and the storage elastic modulus E ′ (f) calculated by the viscoelastic property calculation unit 12. The friction coefficient μ (f) of the tire T is calculated from 12).

Hereinafter, returning to FIG. When the measurement sensor 11 measures the measurement amount of the tire, the viscoelastic property calculation unit 12 calculates the viscoelastic property of the tire T based on the measured data. The friction coefficient calculation unit 13 calculates the friction coefficient of the tire T based on the viscoelastic characteristics calculated by the viscoelastic characteristic calculation unit 12. The driving control unit 14 controls the driving of the vehicle based on the friction coefficient of the tire T calculated by the friction coefficient calculating unit 13, and performs the automatic driving of the vehicle 1 without user operation (hereinafter, the driving control unit 14 is referred to as the driving control unit 14). A mode in which the automobile 1 is automatically driven without user operation is referred to as an automatic driving mode). In the automatic operation mode, the operation control unit 14 controls the drive unit 16-display unit 19 to perform automatic operation. The operation control unit 14 does not automatically operate the vehicle 1 during normal operation (the user operates the vehicle). In a predetermined case, the operation control unit 14 automatically operates the vehicle 1 without any user operation. (This mode is hereinafter referred to as a driving assist mode.) The predetermined case is, for example, a case where an obstacle is detected in the traveling direction of the automobile 1 or a case where the automobile 1 accelerates. Specific examples of operation control of the operation control unit 14 will be described in [Control Example 1]-[Control Example 4] described later. The viscoelastic characteristic calculation unit 12, the friction coefficient calculation unit 13, and the operation control unit 14 are provided in, for example, an ECU (Electronic Control Unit).

The radar sensor 15 detects an object around the automobile 1 when the automobile 1 travels, and outputs a detection result to the operation control unit 14. In particular, the radar sensor 15 can detect an object (obstacle) in the traveling direction of the automobile 1 (hereinafter also referred to as the front). The radar sensor 15 emits radio waves, and detects a reflected wave generated by the reflected radio waves being reflected by a front object. Thereby, the radar sensor 15 can detect the distance between the object and the automobile 1, the position of the object, and the like. The radar sensor 15 is, for example, a millimeter wave radar.

The driving unit 16 drives the wheels by applying a driving force to the wheels of the automobile 1 according to the control of the operation control unit 14. The drive unit 16 accelerates or decelerates the travel of the automobile 1 by increasing or decreasing the drive force applied to the wheels by the drive unit 16. The drive unit 16 may be, for example, an engine or a motor. Or the drive part 16 may be comprised with both the engine and the motor (namely, the motor vehicle 1 may be a hybrid vehicle).

The brake unit 17 decelerates the rotation of the wheels of the automobile 1 according to the control of the operation control unit 14. Thereby, the brake unit 17 decelerates the speed of the automobile 1. The brake part 17 is comprised by the brake pad provided in the brake actuator and the wheel, for example.

The steering unit 18 steers the wheels of the automobile 1 in accordance with the control of the operation control unit 14. For example, the steering unit 18 turns the wheels of the automobile 1 in the left-right direction so as to change the current traveling direction of the automobile 1 according to the control of the operation control unit 14. The steering unit 18 includes, for example, a steering wheel, a differential gear, a steering shaft, and the like, and distributes the driving force that the driving unit 16 applies to the wheels according to the control of the operation control unit 14.

The display unit 19 displays information related to the driving of the vehicle in accordance with the control of the operation control unit 14. The display unit 19 includes a speedometer or a display, for example.

FIG. 6 is a flowchart showing an example of processing of the operation control device 10. Hereinafter, the overall processing of the operation control apparatus 10 will be described with reference to FIGS. 1, 2, and 6.

First, the calculation unit 29 outputs a sound wave emission instruction to the drive waveform generator 22. As an example, the calculation unit 29 may output a sound wave emission instruction to the drive waveform generator 22 in accordance with a measurement instruction from the operation control unit 14. In response to the instruction, the drive waveform generator 22 generates an electric signal of an incident sound wave and outputs it to the direction matching unit 23. The direction aligner 23 outputs an electric signal of the incident sound wave to the transducer 25. The transducer 25 converts the supplied electric signal into an incident sound wave and radiates it to the tire T (step S1 in FIG. 6).

When receiving the reflected sound wave from the tire T, the transducer 25 converts the reflected sound wave into an electric signal, and outputs the converted electric signal to the direction matching unit 23 (step S2 in FIG. 6). The direction matching unit 23 outputs an electric signal of the reflected sound wave to the high frequency amplifier 24. The high frequency amplifier 24 amplifies the high frequency component included in the supplied electric signal and outputs the amplified electric signal to the time data memory unit 27.

The calculation unit 29 reads the data stored in the time data memory unit 27, performs waveform analysis processing in the frequency domain, and acquires the amplitude value and phase at the frequency to be detected (step S3 in FIG. 6). Next, the calculation unit 29 reads the reference value stored in the reference value storage unit 28. The calculation unit 29 calculates the viscoelastic characteristics of the tire T based on the reference value and the amplitude value and phase of the reflected sound wave stored in the time data memory unit 27 (step S4 in FIG. 6). The details of this calculation method are as described above.

The friction coefficient calculation unit 13 calculates the friction coefficient of the tire T using the viscoelastic property of the tire T calculated by the viscoelastic property calculation unit 12 (step S5). The driving control unit 14 controls driving of the automobile based on the friction coefficient of the tire T calculated by the friction coefficient calculating unit 13 (step S6 in FIG. 6).

Thus, in the present invention, in order to control the driving of the automobile, the friction coefficient of the tire is calculated based on the measured viscoelastic characteristics of the tire of the automobile. A decrease in the coefficient of friction of the tire is directly linked to a decrease in safety, which increases the probability of an accident and increases the damage.By using the present invention, it is possible to control the driving of a car more safely. it can. For example, when an unexpected danger occurs during driving, the driving of the automobile can be controlled so that stopping the automobile using the brake is in time for avoiding the danger. In addition, when it is determined that the friction coefficient of the tire has decreased (the tire characteristics have deteriorated), it is assumed that the user of the automobile replaces the tire (particularly, replaces the tire). Therefore, in the present invention, it is possible to improve the safety of the automobile and to prompt the user to replace the tire by notifying the user of the deterioration of the tire.

Hereinafter, a specific example of the control of the operation control unit 14 will be described with reference to FIG. As a premise for the following description, it is assumed that the operation control unit 14 performs control in the automatic operation mode.

[Control Example 1]
When the radar sensor 15 detects an obstacle in front of the automobile 1, the operation control unit 14 controls the brake unit 17 to decelerate the automobile 1 (in order to avoid a collision between the automobile 1 and the obstacle). (Especially stop). Here, when the measured tire friction coefficient is less than a predetermined threshold value (when the tire is deteriorated), the operation control unit 14 determines that the tire friction coefficient is equal to or greater than the predetermined threshold value (when the tire is The vehicle 1 is decelerated at an earlier timing as compared with the case where it is not deteriorated.

As an example, when the automobile 1 is traveling at 60 km / h, the driving control unit 14 has a distance between the obstacle and the automobile 1 of 20 m or less when the tire friction coefficient is equal to or greater than a predetermined threshold. At the time, the automobile 1 is stopped. However, when the vehicle 1 is traveling at 60 km / h and the friction coefficient of the tire is less than a predetermined threshold value, the operation control unit 14 determines when the distance between the obstacle and the vehicle 1 is 25 m or less. Then, the car 1 is stopped. As described above, the driving control unit 14 determines that the tire friction coefficient is equal to or greater than the predetermined threshold when the friction coefficient of the tire is less than the predetermined threshold even when the automobile 1 is traveling at the same traveling speed. The distance between the vehicle 1 that causes the vehicle 1 to stop and the obstacle is set longer. That is, the operation control unit 14 causes the automobile 1 to decelerate at an earlier timing during traveling. As described above, the operation control unit 14 can reliably avoid the collision between the automobile 1 and the obstacle even when the tire is deteriorated.

When the radar sensor 15 detects an obstacle in front of the vehicle 1, the operation control unit 14 controls the steering unit 18 instead of the deceleration of the vehicle 1 (or simultaneously with the deceleration of the vehicle 1). Steering for changing the traveling direction of the automobile may be executed. That is, the driving control unit 14 changes the course of the automobile 1 to the left or right in order to avoid a collision with an obstacle. At this time, when the tire friction coefficient is less than the predetermined threshold, the traveling direction of the automobile 1 is changed at an earlier timing than when the tire friction coefficient is greater than or equal to the predetermined threshold.

[Control Example 2]
When accelerating the automobile 1, the operation control unit 14 increases the acceleration of the automobile 1 when the tire friction coefficient is less than a predetermined threshold, compared to the case where the tire friction coefficient is greater than or equal to the predetermined threshold. You may set small. As an example, when the automobile 1 starts to move from a stopped state, the drive unit 16 applies driving force to the wheels. At this time, when the friction coefficient of the tire is less than the predetermined threshold, the driving control unit 14 reduces the driving force applied to the wheel as compared with the case where the tire friction coefficient is equal to or greater than the predetermined threshold. The drive unit 16 is controlled. The driving control unit 14 can perform the same control even when the vehicle 1 is accelerated from a state where the vehicle 1 is traveling at a constant speed. From the above, the operation control unit 14 can prevent sudden acceleration of the automobile 1 when the tire is deteriorated, and can reduce the possibility of an accident.

[Control Example 3]
When the tire friction coefficient is less than the predetermined threshold, the operation control unit 14 may set the maximum speed of the automobile 1 lower than when the tire friction coefficient is greater than or equal to the predetermined threshold. . For example, when the friction coefficient of the tire is less than a predetermined threshold, the operation control unit 14 controls the driving unit 16 to limit the driving force applied to the wheels to less than a predetermined value. Thus, the driving control unit 14 limits the maximum speed of the automobile 1 when the tire is deteriorated. Therefore, the driving control unit 14 can reduce the possibility of an accident caused by the automobile 1 when the tire is deteriorated. In addition, when the friction coefficient of a tire is more than a predetermined threshold value, the driving control unit 14 can perform control so that the driving unit 16 applies a driving force of a predetermined value or more to the wheels.

[Control Example 4]
In Control Example 1-3, the operation control unit 14 controlled the operation of the automobile 1 using the tire friction coefficient. However, in the control example 1-3, the operation control unit 14 may control the operation of the automobile 1 using not only the tire friction coefficient but also the tire braking distance data. Thus, since the driving control unit 14 controls the driving of the automobile 1 using tire information other than the friction coefficient of the tire, the driving control unit 14 more reliably reflects the safety of the tire to control the driving of the automobile 1. Can do.

In the automobile 1, when the braking distance in a state where the ABS is operating (that is, a state where the automobile performs sudden braking) is larger than a predetermined value, it can be estimated that the tire characteristics are deteriorated. When the automobile 1 is accelerated, the same estimation is possible even when the TCS that applies brakes and suppresses the idling of the tire is operating. Even when the operation frequency of the ABS or TCS function is larger than a predetermined value, it can be estimated that the characteristics of the tire are deteriorated. For this reason, the driving control unit 14 is at least one of the data of the braking distance of the tire when the ABS or TCS function is operating, and the operation frequency of the ABS or TCS function when the automobile has the ABS or TCS function. The driving of the automobile 1 may be controlled by using one of them together with the measured tire friction coefficient. Note that even in the automobile 1 that does not have the ABS or TCS function, the operation control unit 14 uses both the braking distance data of the tire when the user applies the brake and the measured friction coefficient of the tire, and uses the automobile 1 Can be controlled.

In addition, the effect of tire deterioration also occurs on the steering angle and side slip when turning, the speed control of the vehicle according to the lateral acceleration G generated on the vehicle body, and the degree of tire lock when the user manually brakes. . For this reason, the driving control part 14 is the data of the steering angle at the time of the turn of the motor vehicle 1, the side slip at the time of the motor vehicle 1 turning, the speed control according to the lateral acceleration, or the degree of the tire lock when the user manually applies the brake. The driving of the automobile 1 may be controlled by using at least one of these together with the measured tire friction coefficient. As a result, the deterioration of the tire can be more accurately reflected in the driving control of the automobile.

Furthermore, the braking force acting on the tire and the lateral acceleration G can be calculated from the measured values (acceleration and vehicle weight values) of the acceleration sensor and the vehicle weight sensor mounted on the automobile 1. For this reason, the operation control unit 14 can accurately determine the degree of deterioration from the reference state of the tire by normalizing the braking distance and the side slip at the time of turning using the calculated braking force and lateral acceleration G. . In addition, by statistical processing with the aid of these measured values of the car group, the braking distance when the ABS or TCS function is operating, the frequency of operation of the ABS or TCS function, and the normalization of the skid when turning Is more reflective of the actual situation. Thereby, it is possible to accurately control the operation of the automobile.

As an example, the vehicle 1 is provided with a sensor for measuring a braking distance when the ABS or TCS function is used as an in-vehicle device, and the sensor outputs braking distance data to the operation control unit 14. The operation control unit 14 controls the operation of the automobile 1 based on the acquired tire braking distance data and tire friction coefficient data. When the operation control unit 14 performs the control shown in Control Example 1, if the tire friction coefficient calculated by the friction coefficient calculation unit 13 is the same, the longer the braking distance of the tire, the longer the vehicle 1 decelerates or travels. Make changes happen earlier. The operation control unit 14 can perform the same control even in the case of the control example 2-3.

The operation control unit 14 may display that the tire has deteriorated on the display unit 19 when the friction coefficient of the tire is less than a predetermined threshold. Similarly, the braking distance when the ABS or TCS function is operating, the frequency of operation of the ABS or TCS function, or the data of the skid during the turn is not only used for driving control of the car, but also displayed on the display unit 19. It may be displayed and notified to the user.

[Embodiment 2]
In the second embodiment, an example in which the viscoelastic characteristics of the bulk in the tire T are calculated instead of the viscoelastic characteristics of the inner surface of the tread in the tire T will be described.

The calculation unit 29 estimates the bulk (overall) acoustic characteristics and viscoelastic characteristics of the tire T based on the viscoelastic characteristics of the inner surface of the tread of the tire T calculated by the surface reflection method in the first embodiment. Can do. The friction coefficient calculation unit 13 calculates a bulk friction coefficient μ in the tire T using the estimated bulk viscoelastic characteristics. The driving control unit 14 can control the driving of the automobile 1 based on whether or not the bulk friction coefficient μ calculated by the friction coefficient calculating unit 13 is less than a predetermined threshold value.

Further, the calculation unit 29 may directly calculate the viscoelastic characteristics of the bulk of the tire by using the bottom surface reflection method. Here, the bottom surface reflection method includes a reflected sound wave (hereinafter referred to as a first reflected sound wave) generated when an incident sound wave is incident on the tire and reflected by the inner surface, and an incident sound wave transmitted through the inner surface of the tire. Is a method for measuring viscoelastic characteristics of a bulk of a tire based on a reflected sound wave (hereinafter referred to as a second reflected sound wave) generated by being reflected on an outer surface opposite to the inner surface (for example, Patent Document 1).

In the bottom surface reflection method, since both the first reflected sound wave and the second reflected sound wave are transmitted through the delay member 26, the tire interior (tread rubber) is based on the propagation time of the first reflected sound wave and the second reflected sound wave. ) Sound wave propagation time can be calculated. The computing unit 29 calculates the thickness of the tread rubber based on the propagation time inside the tire and the reference sound speed of the sound wave (especially the sound speed when the tire is new). Here, an actual sound speed inside the tire may be used instead of the reference sound speed of the sound wave. This actual speed of sound can be calculated by installing a reflector in the tire tread rubber, and measuring the time until the sound wave is reflected by radiating sound waves to the reflector (from the transducer 25 to the reflector). And the thickness of the retarder 26 are known). Further, the sound speed may be measured by measuring the time until the sound wave is reflected by radiating the sound wave to the groove portion of the tire.

The calculation unit 29 calculates the bulk storage elastic modulus E ′ (f) of the tire based on the value of the sound velocity and the thickness of the tread rubber calculated as described above. Further, the calculation unit 29 calculates a loss elastic modulus E ″ (f) of the tire bulk by calculating a sound wave attenuation coefficient α (f). The calculation unit 29 calculates the calculated E ′ (f) and E ′. The loss tangent tan δ (f) of the bulk of the tire is calculated by calculating the ratio with “(f)”.

[Embodiment 3]
The third embodiment of the present invention will be described below with reference to the drawings. In the third embodiment, an example in which the viscoelastic characteristics of the outer surface of the tread in the tire T are calculated instead of the viscoelastic characteristics of the inner surface of the tread in the tire T will be described. Furthermore, in Embodiment 3, the measured value of the reflected sound wave reflected from the outer surface of the tire T at the first timing and the tire T at the second timing after a predetermined time has elapsed from the first timing. The measured value of the reflected sound wave reflected from the outer surface of the is compared. Thereby, the viscoelastic characteristic (especially loss tangent) in the outer surface of the tread is calculated. Hereinafter, this calculation method is referred to as a bottom surface reflection comparison method. In general, the viscoelastic characteristics of the same tire T deteriorate when a long time elapses. In the following, assuming such a case, the “first timing” is described as before deterioration, and the “second timing” is described as after deterioration.

FIG. 7A and FIG. 7B are diagrams illustrating a method for calculating viscoelastic properties using this bottom surface reflection comparison method. FIG. 7A is a diagram showing a reflection state of an incident sound wave when obtaining a reference value, and FIG. 7B is a diagram showing a reflection state of the incident sound wave when calculating a viscoelastic characteristic of the tire T after deterioration. It is. In the following description, acoustic impedance representing the propagation characteristics of incident sound waves radiated from the transducer 25 of the measurement sensor 11 is used.

First, the reference value will be described with reference to FIG. 7A. The reference value is the phase and amplitude value of the reflected sound wave at the frequency to be measured when the tire T is not deteriorated. At this time, the incident sound wave is reflected by the boundary surface between the outer surface of the tire T which has not deteriorated and the air. If the frequency of the incident sound wave and the reflected sound wave is f, the acoustic impedance of the outer surface of the tire T that has not deteriorated can be expressed as Z _TO (f) that is a function of the frequency f. Similarly, the acoustic impedance in the air can also be expressed as Z _A (f) that is a function of the frequency f. Here, the acoustic impedances Z _TO (f) and Z _A (f) are complex values.

The reflectance R _TO (f) of the reflected sound wave at the interface between the outer surface of the tire T and the air is R _TO (f) = (Z _A (f) −Z _TO (f)) / (Z _A (f) + Z _TO (f)) (13)
It becomes. At this time, since Z _A (f) is sufficiently smaller than Z _TO (f) at an arbitrary frequency f, it can be generally assumed that R _TO (f) = − 1 from Equation (13). it can.

As an example, when the values of Z _A (f) = 428.6 (Pa · s / m), Z _TO (f) = 1.5 × 10 ⁶ (Pa · s / m), , R _TO (f) is R _TO (f) = − 0.99994, which is a value very close to −1. Z _TO (f) may be a value in the range of 1.5 × 10 ⁶ to 2.4 × 10 ⁶ (Pa · s / m).

In the following description, the expression of the reflected sound wave incident on the transducer 25 is expressed as b _T0 (f) exp (iθ _T0 (f)). i is an imaginary unit, b _T0 (f) is a real amplitude value at a target frequency, and θ _T0 (f) is a real number greater than or equal to 0 and represents a phase at each frequency. The equation of the incident sound wave radiated from the measurement sensor 11 to the outer surface of the tire T through the delay member 26 and the inside of the tire T is:
b _T0 (f) exp (iθ _T0 (f)) × R _TO (f) (14)
It becomes. Therefore, in FIG. 7A, it can be considered that the incident sound wave shown in Formula (13) is radiated to the outer surface of the tire T. In the reference value storage unit 28, the amplitude b _T0 (f) and the phase θ _T0 (f) in Expression (14) are stored in advance as reference values. This reference value b _T0 (f) is acquired by measuring in advance.

Next, with reference to FIG. 7B, a case where the change in viscoelastic characteristics on the outer surface of the tire T is calculated will be described. When calculating the change in viscoelastic characteristics of the tire T, the incident sound wave shown in FIG. 7A is radiated to the outer surface of the deteriorated tire T. The transducer 25 receives the reflected sound wave reflected at the boundary surface between the outer surface of the tire T and the air, and the high frequency amplifier 24 amplifies the high frequency component in the electric signal of the reflected sound wave.

Here, let Z _TOG (f) be the acoustic impedance of the outer surface of the deteriorated tire T. The acoustic impedance Z _TOG (f) is a function of the frequency f. The reflectance R _TOG (f) of the incident sound wave at the interface between the outer surface of the deteriorated tire T and the air is
R _TOG (f) = (Z _A (f) −Z _TOG (f)) / (Z _A (f) + Z _TOG (f)) (15)
It becomes. From equation (15), Z _TOG (f) is expressed as follows.
Z _TOG (f) = Z _A (f) × (1−R _TOG (f)) / (1 + R _TOG (f)) (16)

FIG. 8 is a table illustrating the acoustic impedance and the reflectance in the two cases of the tire T. Case 1 is the acoustic impedance _{Z TO} is ^{1.5 × 10 6 (Pa · s} / m) of the outer surface of the tire T which is not degraded, the acoustic impedance _{Z TO} is 2.4 × the outer surface of the degraded tire T An example of 10 ⁶ (Pa · s / m) is shown. The case 2 is, the acoustic impedance _{Z TO} is 2.4 × ¹⁰ 6 of the outer surface of the tire T which is not deteriorated (Pa · s / m), the acoustic impedance _{Z TO} of the outer surface of the degraded tire T 1. An example of 5 × 10 ⁶ (Pa · s / m) is shown. Note that _{Z A} is a common value of 428.6 (Pa · s / m) . At this time, in case 1, R _TO = −0.9994 and R _TOG = −0.9996. In Case 2, R _TO = −0.9996 and R _TOG = −0.9994. Above, in Cases 1 and _2, although _{R TO} and _{R TOG} is close to a value of -1, not exactly the same value. R _TO and R _TOG are slightly different from the value of -1.

In the following description, the expression of the reflected sound wave incident on the transducer 25 is _expressed as b _T0G (f) exp (iθ _T0G (f)). i is an imaginary unit, b _T0G (f) is a real amplitude value at a target frequency, and θ _T0G (f) is a real number greater than or equal to 0 and represents a phase at each frequency. Using the reference value in the equation (14), the reflectance R _TOG (f) of the incident sound wave is R _TOG (f) = − | R _TOG (f) | × exp (−i (θ), as in the surface reflection method. _G (f)) (17)
It is expressed. In addition,
| R _TOG (f) | = | b _T0G (f) / b _T0 (f) | (18)
θ _G (f) = θ _T0 (f) −θ _T0G (f) (19)
It is. Here, Z _T0G (f) is obtained as follows by substituting Equation (17) into Equation (16).
Z _T0G (f) = Z _A (f) × (1+ | R _TOG (f) | × exp (−iθ _G (f)) / (1− | R _TOG (f) | × exp (−iθ _G (f )) ... (20)

Here, the storage elastic modulus of the tire T as a function of the frequency f is L ′ (f), and the loss elastic modulus of the tire T is L ″ (f). At this time, L ′ (f) and L ″ (f ) And the acoustic impedance Z _TOG (f) and density ρ _T of the deteriorated tire T, the following relationship is established.
L ′ (f) + iL ″ (f) = Z _TOG (f) ² / ρ _T (21)

By substituting equation (20) into equation (21) and separating the real and imaginary components, the loss tangent tan δ (f) is calculated as follows.
tan δ (f) = L ″ (f) / L ′ (f) = − 4 | R _TOG (f) | × (1− | R _TOG (f) | ² ) × sin θ _G (f) / ((1- | R _TOG (f) | ² ) ² -4 × | R _TOG (f) | ² × sin ² θ _G (f)) (22)

The storage elastic modulus L ′ (f) and the loss elastic modulus L ″ (f) are calculated as follows.
L ′ (f) = Re [Z _TOG (f) ² / ρ _T ] = (Z _A (f) ² / ρ _T ) × (1− | R _TOG (f) | ² ) ² −4 | R _TOG ( f) | ² × sin ² θ _G (f) / {1-2 | R _TOG (f) | cos θ _G (f) + | R _TOG (f) | ² } ² (23)
L ″ (f) = Im [Z _TOG (f) ² / ρ _T ] = − (Z _A (f) ² / ρ _T ) × 4 | R _TOG (f) | (1- | R _TOG (f) | ² ) × sin θ _G (f) / {1-2 | R _TOG (f) | × cos θ _G (f) + | R _TOG (f) | ² } ² (24)

As shown in the equations (21) to (24), the storage elastic modulus L ′ (f), the loss elastic modulus L ″ (f), and the loss tangent tan δ (f) are all b _T0 (f), θ _T0 (f). R _TOG (f) = b _T0G (f) / b _T0 (f) (ratio of the amplitude of the reflected sound wave before deterioration and the amplitude of the reflected sound wave after deterioration), θ _G (f) = θ _T0 (F) −θ _T0G (f) (phase difference between the phase of the reflected sound wave before deterioration and the phase of the reflected sound wave after deterioration) Therefore, the amplitude b _T0 (f) before deterioration and the phase characteristic θ _{By using T0} (f) as a reference value and comparing it with the data of the electric signal of the reflected sound wave obtained at the time of measuring the outer surface of the deteriorated tire T, the viscoelastic characteristics (especially loss) of the outer surface of the deteriorated tire T are obtained. In addition, as described above, the loss tangent of the outer surface of the tire T depends on the frequency. For this reason, the calculation unit 29 may derive a loss tangent for each of a plurality of frequency components, and when it is necessary to calculate a loss tangent at a high frequency, an ultrasonic wave is used as the incident sound wave. May be supplied from

It should be noted that the phase value of each frequency used in the calculation changes as the propagation distance of the sound wave changes due to tire wear. Therefore, the calculating part 29 may correct | amend the phase value of each frequency using the above-mentioned calculated value of tread rubber thickness.

In summary, when the measurement sensor 11 and the viscoelastic property calculation unit 12 measure the reflected wave on the outer surface of the tire, the calculation unit 29 regards the tire tread rubber as the delay member 26 in the first embodiment, and the acoustic impedance of the air The surface reflection method is calculated based on. In this way, the calculation unit 29 calculates viscoelastic characteristics such as loss tangent. The friction coefficient calculation unit 13 calculates the friction coefficient μ of the tire outer surface using the calculated viscoelastic characteristic of the tire outer surface. The driving control unit 14 can control the driving of the automobile 1 based on whether or not the friction coefficient μ of the tire outer surface calculated by the friction coefficient calculating unit 13 is less than a predetermined threshold value. Operation control unit 14 When the friction coefficient μ of the tire outer surface is less than a predetermined threshold value, it is determined that the outer surface of the tire T has deteriorated due to heat, ozone, ultraviolet rays, repeated stress, or the like.

In the viscoelastic property measurement of the outer surface of the tire described above, a measurement error may occur due to water film or mud adhering to the outer surface of the tire. Therefore, for example, when measuring viscoelastic properties in the groove of a tire, the measurement is performed with the water film attached to the outer surface of the tire (by measuring in the same environment), and the influence of errors. Can be corrected. As an example, tire deterioration may be measured after the car is washed. For example, a measurement button is provided on an automobile, and when the button is pressed, the automobile 1 enters a deterioration measurement mode according to the tire condition, and the calculation unit 29 executes the above-described processing.

Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention. For example, the measurement sensor 11 is not limited to the structure illustrated in FIG. 2 as long as it can measure a measurement amount related to the viscoelastic characteristics of the tire.

When the automobile 1 is a front wheel drive vehicle, braking force and driving force are concentrated on the front wheel tire (front tire), and therefore the front wheel tire is more easily worn than the rear wheel tire (rear tire). Therefore, it is considered that the operation can be controlled by more accurately reflecting the degree of deterioration of the tire by installing the measurement sensor 11 on the front tire that is easily worn and measuring the viscoelastic characteristics. Conversely, when the automobile 1 is a rear wheel drive vehicle, the rear wheel tire is more easily worn than the front wheel tire. For this reason, it is considered that the operation can be controlled by more accurately reflecting the degree of deterioration of the tire by installing the measurement sensor 11 on the rear wheel tire that is easily worn and measuring the viscoelastic characteristics.

Further, in the front wheel tire, the shoulder portions (both ends of the tread pattern in the tire) are easily worn, and in the rear wheel tire, the center portion of the tread pattern is easily worn. For this reason, it is considered that the operation can be controlled by more accurately reflecting the degree of deterioration of the tire, as described above, by installing the measurement sensors 11 at those places where they are easily worn and measuring the viscoelastic characteristics. It is done.

When the measurement sensor 11 measures a measurement amount for a plurality of tires, the measurement sensor 11 is provided for each tire whose measurement amount is measured. The method of providing the measurement sensor 11 for each tire is, for example, as shown in FIG. Thus, when the measurement amount regarding the viscoelastic property of a plurality of tires is measured, the viscoelastic property calculation unit 12 calculates the viscoelastic property of each tire using the measured measurement amount. The friction coefficient calculation unit 13 calculates the friction coefficient of each tire using the calculated viscoelastic characteristics of each tire. Here, the operation control unit 14 determines whether or not the calculated average value of the friction coefficient of each tire is less than a predetermined threshold value, and executes the control of the above-described control example 1-3 based on the determination result. May be. Further, the operation control unit 14 determines whether or not the friction coefficient is less than a predetermined threshold value for a predetermined number (one or more) of tires, and based on the determination result, the operation control unit 1-3 described above. Control may be performed.

The threshold for the operation control unit 14 to determine tire deterioration is not limited to one, and may be two or more. For example, in the control example 1, the driving control unit 14 may set the timing of deceleration of the automobile 1 or change in the traveling direction using the first threshold value A1 and the second threshold value A2 (A1> A2). Specifically, when the tire friction coefficient is equal to or greater than the first threshold value A1, the operation control unit 14 causes the vehicle 1 to decelerate or change the traveling direction at a predetermined timing (timing t1). . When the tire friction coefficient is less than the first threshold value A1 and greater than or equal to the second threshold value A2, the operation control unit 14 determines the timing of deceleration of the automobile 1 or change in the traveling direction from the timing t1. It is executed at a predetermined timing (timing t2) as soon as possible. Furthermore, when the friction coefficient of the tire is less than the second threshold A2, the operation control unit 14 causes the vehicle 1 to decelerate or change the traveling direction at a timing earlier than the timing t2. In this way, the operation control unit 14 can perform more detailed operation control according to the degree of deterioration of the tire.

The driving control unit 14 not only controls the driving of the automobile 1 when the tire friction coefficient calculated by the friction coefficient calculating unit 13 is less than a predetermined threshold, but also the tire friction coefficient is less than the predetermined threshold. You may output the alerting signal which notifies the circumference | surroundings of this.

For example, the operation control unit 14 irradiates other automobiles with radio wave signals. Another vehicle that has received the signal notifies the user of the vehicle by a screen, voice, or the like that there is the vehicle 1 that has emitted the signal. Alternatively, when another vehicle is performing automatic control, the other vehicle may control driving so as to avoid the vehicle 1. For example, it is possible to perform the above-described deceleration of the automobile or steering to change the traveling direction thereof.

The driving control unit 14 may output a signal to a terminal (smartphone or the like) possessed by a pedestrian or the like. The terminal that has received the signal displays on the display section that the automobile 1 that has transmitted the signal is nearby. The user of the terminal recognizes that the automobile 1 is nearby by looking at this display. As a result, the user can walk so as to avoid the automobile 1, for example. Thus, for example, when the tire of the automobile 1 is deteriorated, a notification signal is notified to surrounding cars and pedestrians. Therefore, there is a high possibility that surrounding cars and pedestrians can prevent accidents.

The radar sensor 15 provided in the automobile 1 is not limited to one, and a plurality of radar sensors that radiate radio waves having different wavelengths may be provided. Further, the automobile 1 may be provided with a stereo camera instead of the radar sensor 15 as a component necessary for automatic driving. This camera photographs the surrounding environment of the automobile 1 and detects an obstacle in front of the automobile 1 based on the photographed data. Furthermore, both the radar sensor 15 and the stereo camera may be provided in the automobile 1.

When the vehicle 1 is an electric vehicle or a hybrid vehicle, and the motors that are the drive units 16 are provided on the left and right wheels, respectively, the motors provided on the left and right wheels according to the control of the operation control unit 14 Can apply different driving forces to each wheel. Thereby, the automobile 1 can change the traveling direction. In this case, the steering unit 18 may not be provided.

In Embodiment 1, the control example of the operation control unit 14 in the automatic operation mode has been described. However, similar control can be executed even in the driving assist mode. In this case, the radar sensor 15 may not be provided in the automobile 1.

This application claims priority based on Japanese Patent Application No. 2014-142267 filed on July 10, 2014, the entire disclosure of which is incorporated herein.

DESCRIPTION OF SYMBOLS 1 Car 10 Operation control apparatus 11 Measurement sensor 12 Viscoelastic property calculation part 13 Friction coefficient calculation part 14 Operation control part 15 Radar sensor 16 Drive part 17 Brake part 18 Steering part 19 Display part 20 Sound wave signal generation part 21 Contact part 22 Drive waveform Generator 23 Direction matching unit 24 High frequency amplifier 25 Transducer 26 Delay material 27 Time data memory unit 28 Reference value storage unit 29 Calculation unit 30 Constant storage unit 31 Calculation unit

Claims (11)

1. A measurement sensor for measuring a measurement amount relating to viscoelastic characteristics of an automobile tire;
   A viscoelastic property calculation unit that calculates the viscoelastic property of the tire using the measurement amount measured by the measurement sensor;
   A friction coefficient calculation unit that calculates a friction coefficient of a tire using the viscoelastic property calculated by the viscoelastic property calculation unit;
   A driving control unit that controls the driving of the automobile based on the friction coefficient of the tire calculated by the friction coefficient calculating unit;
   An automobile driving control device comprising:
2. The driving control unit executes steering for decelerating the automobile or changing the advancing direction of the automobile when an obstacle is detected in the advancing direction of the automobile,
   When the friction coefficient of the tire is less than a predetermined threshold, the vehicle decelerates or changes the traveling direction of the automobile as compared with the case where the friction coefficient of the tire is greater than or equal to a predetermined threshold. To be executed at an earlier timing,
   The operation control apparatus according to claim 1.
3. The driving control unit, when accelerating the automobile, when the friction coefficient of the tire is less than a predetermined threshold, compared with the case where the friction coefficient of the tire is greater than or equal to a predetermined threshold, Set the acceleration of the car small,
   The operation control apparatus according to claim 1 or 2.
4. When the friction coefficient of the tire is less than a predetermined threshold, the operation control unit sets the maximum speed of the automobile lower than that when the friction coefficient of the tire is equal to or greater than a predetermined threshold. To
   The operation control apparatus according to any one of claims 1 to 3.
5. The driving control unit is configured to control the braking distance of the tire, the rudder angle at the time of turning of the automobile, the side slip at the time of turning of the automobile, the speed control according to the lateral acceleration of the automobile, or when the brake is applied in the automobile. Using at least one data of the degree of locking of the tire together with the coefficient of friction of the tire to control the driving of the vehicle;
   The operation control apparatus according to any one of claims 1 to 4.
6. The operation controller is
   Using at least one data of the braking distance of the vehicle when the ABS or TCS function is operating in the vehicle, or the frequency of operation of the ABS or TCS function of the vehicle, together with the friction coefficient of the tire Controlling the driving of the car,
   The operation control apparatus according to any one of claims 1 to 4.
7. The measurement sensor is
   A radiating portion for emitting incident sound waves to the tire;
   A receiving unit that receives a reflected sound wave generated by the incident sound wave radiated from the radiation unit being reflected by the tire; and
   The viscoelastic property calculating unit calculates the viscoelastic property of the tire based on the reflected sound wave received by the receiving unit.
   The operation control apparatus according to any one of claims 1 to 6.
8. The radiating unit radiates an incident sound wave to the tire at a first timing, and radiates the incident sound wave to the tire at a second timing after a predetermined time has elapsed from the first timing.
   The receiving unit receives, in the tire at the first timing, a first reflected sound wave that is generated by reflecting the incident sound wave on a surface opposite to a surface on which the incident sound wave is radiated. In the tire at the timing of 2, the second reflected sound wave generated by reflecting the incident sound wave on the opposite surface is received,
   The viscoelastic characteristic calculation unit includes an amplitude of the first reflected sound wave and an amplitude of the second reflected sound wave received by the receiving unit, a phase of the first reflected sound wave, and a phase of the second reflected sound wave. Based on the above, viscoelastic characteristics in the tire at the second timing is calculated,
   The operation control apparatus according to claim 7.
9. When the friction coefficient of the tire is less than a predetermined threshold, the operation control unit outputs a notification signal that notifies the surroundings that the tire friction coefficient is less than the predetermined threshold.
   The operation control device according to any one of claims 1 to 8.
10. An automobile equipped with the operation control device according to any one of claims 1 to 9.
11. A measurement step for measuring a measurement amount relating to viscoelastic properties of an automobile tire;
    Viscoelastic property calculation step of calculating the viscoelastic property of the tire using the measured amount measured,
    A friction coefficient calculating step of calculating a friction coefficient of the tire using the calculated viscoelastic characteristics;
    An operation control step for controlling the operation of the automobile based on the calculated friction coefficient of the tire;
    An automobile driving control method comprising:

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