JPH08183433A - Slip angle measuring device using doppler effect - Google Patents

Abstract

PURPOSE: To provide a device for measuring a slip angle with accuracy without being influenced by sound velocity in a slip angle measuring device using Doppler effect. CONSTITUTION: A transmitting ultrasonic vibrator 11 and receiving ultrasonic vibrators 12, 13 are arranged with the respective vibrating faces facing a specified point P on the road surface so as to become specified sensor geometry. A tire slip angle αP at the point P is computed in a slip angle computing circuit 26 from the Doppler shift frequency fd1 , fd2 of ultrasonic wave transmitted from the ultrasonic vibrator 11, reflected around the point P as the center and received by the respective ultrasonic vibrators 12, 13, and this value is corrected into the value α at a tire grounding point by a correcting circuit 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring the slip angle of a running vehicle by utilizing the Doppler effect of sound waves, and in particular, excludes the sonic term from the formula for calculating the slip angle. And a device for accurately measuring a slip angle.

[0002]

2. Description of the Related Art In a vehicle equipped with wheels with pneumatic rubber tires, the tire slip angle (the angle between the traveling direction of the wheel and the rolling surface) is an important physical quantity that indicates the vehicle behavior. Although there is an increasing demand for detecting and performing vehicle control using the detected value, there is currently no practical sensor that can detect the slip angle with high accuracy.

A conventionally proposed slip angle measuring device utilizes a Doppler effect of a sound wave, and is described in, for example, Japanese Patent Laid-Open No. 4-220584. In the device described in this publication, as shown in FIG. 20, when the tire centerline direction is the X axis and the tire rotation axis direction is the Y axis, the tire slip angle α is the wheel speed in the X axis direction. Is expressed by the following equation (1) from the component V _{X of the} vehicle and the component V _{Y in the} Y-axis direction, the wheel speed components V _X and V _Y in these directions are detected by the ultrasonic sensors 91 and 92, respectively. The calculation is performed based on the Doppler shift frequencies f _X and f _Y.

Α = tan ⁻¹ (V _Y / V _X ) (1) That is, each of the ultrasonic sensors 91, 92 includes ultrasonic transmitters 91 a, 92 a and receivers 91 b, 92 b. , The ultrasonic sensor 91 for measuring the X component V _X of the wheel speed is
X ′ parallel to the transmitting and receiving surfaces outside the X axis
Y component V of the wheel speed toward the measured road surface 93X in the axial front direction
_The ultrasonic sensor 92 for _Y measurement directs the transmitting surface and the receiving surface toward the measurement road surface 93Y on the outer side in the Y-axis direction, and restricts only the rotation of the wheel in the rolling direction to the wheel or a portion that performs the same movement as the wheel. In other directions, it is installed so as to synchronize with the movement of the wheels.

A signal processing device 94 is mounted on the vehicle body, and transmission signals X _t and Y _t are transmitted to the transmitters 91a and 92a of the ultrasonic sensors 91 and 92 through a transmission circuit 94a in the signal processing device 94. By being output, the transmitters 91a and 92a output the measured road surfaces 93X and 93, respectively.
An ultrasonic wave having a predetermined frequency f _S is transmitted to Y, and the ultrasonic waves reflected from the measurement road surfaces 93X and 93Y are received by the receivers 91b and 91b.
92b receives. This received ultrasonic wave reception signal X
The frequencies f ₁ and f _{2 of the} received ultrasonic waves are detected by the receiving circuit 94b from _r and Y _r , and these frequencies f ₁ and f ₂ are different from the transmission frequency f _S according to the speed in each direction due to the Doppler effect. This is different, and this is the Doppler frequency detection circuit 9
4c, and the Doppler frequencies f _X and f _Y in the ultrasonic sensors 91 and 92 are calculated. Then, in the slip angle calculation circuit 94d, the X component V _X and the Y component V _Y of the wheel speed are calculated based on these Doppler frequencies f _X and f _Y , respectively, and the slip angle α is calculated from the equation (1). are doing.

[0006]

However, when the speed is measured by the sound wave using the Doppler effect, the sound speed is about 6 times the maximum speed of the vehicle, so that the measurement error is high in the high speed region. There is a problem that it becomes large. Further, since the speed of sound changes depending on the temperature, the wheel speeds measured differ depending on the temperature of the measurement road surface and the temperature in the vicinity thereof. However, in the conventional device described above, the wheel speeds measured on separate measurement road surfaces 93X and 93Y are different. The fast X component V _X ,
Since the slip angle is calculated based on the Y component V _Y ,
There is a problem that the measurement error of the slip angle due to the influence of the sound velocity is large.

Assuming that the velocity of the wheel in the traveling direction is V, the angle between the ultrasonic transmission axis and the measured road surface is θ _S , and the speed of sound is C _S , the difference between the transmission frequency f _S and the reception frequency f _R. The Doppler shift frequency f _d calculated as is expressed by the following equation (2). _{f d = (2Vf S cos θ} S) / (c S -Vcos θ S) ...... (2) By this modification of the equation (2), the wheel speed V by using the Doppler shift frequency f _d of the following (3) It is represented by a formula.

V = f _d C _S / (2f _S cos θ _S + f _d cos θ _S ) (3) Thus, when calculating the wheel speed V from the Doppler shift frequency f _d , the sound speed c _S Therefore, as in the case of the above-described conventional apparatus, separate measurement road surfaces 93X, 9
In order to accurately calculate the slip angle α from the X component V _X and the Y component V _Y of the wheel speed measured at 3Y, each measured road surface 9
It is necessary to measure the speed of sound between the 3X and 93Y and the ultrasonic sensors 91 and 92. However, it is generally difficult to accurately measure the sound velocity.

The present invention is intended to solve such unsolved problems of the prior art, and in a slip angle measuring device utilizing the Doppler effect, there is no influence of the speed of sound, It is an object of the present invention to provide an apparatus for measuring a slip angle with high accuracy.

[0010]

In order to achieve the above object, a slip angle measuring device according to claim 1 is installed at a predetermined position of a vehicle, and a transmission axis is directed to a predetermined point on a road surface on which the vehicle runs. Between the sound wave transmitting means for transmitting sound waves at a predetermined angle and the sound waves transmitted from the sound wave transmitting means and reflected at the predetermined point, which are installed at different positions of the vehicle, and sandwich a vertical plane including the predetermined point. Two sound wave receiving means for receiving sound waves propagated at a predetermined angle on both sides, and Doppler shift frequency detection for detecting the amount of frequency change from the time of transmission due to the Doppler effect of the sound waves received by each of the sound wave receiving means. Means, and a slip angle calculating means for calculating a slip angle of the vehicle based on a frequency change amount in each sound wave receiving means detected by the Doppler shift frequency detecting means, It is characterized in that it comprises.

A slip angle measuring device according to a second aspect is the slip angle measuring device according to the first aspect, wherein the slip angle is a tire slip angle, and a turning velocity detecting means for detecting a turning velocity of the vehicle body, With the wheel speed detecting means for detecting the speed of the wheel in the traveling direction at a predetermined point, the slip angle calculating means, the turning speed detection value from the turning speed detecting means, and the wheel from the wheel speed detecting means. The present invention is characterized by further comprising a correction unit that corrects a deviation caused by a difference between the predetermined point and the ground contact point of the tire based on the speed detection value.

A slip angle measuring device according to a third aspect of the present invention is the slip angle measuring device according to the first aspect, wherein the two sound wave receiving means have a sensitivity directivity of a sound wave to be used and a predetermined vehicle speed set in advance. It is characterized in that it is selected according to.

[0013]

In the slip angle measuring device according to claims 1 to 3,
When the sound wave is transmitted from the sound wave transmitting means at a predetermined angle with the transmission axis directed to a predetermined point on the road surface, the two sound wave receiving means receive the sound wave transmitted from the sound wave transmitting means and reflected at the predetermined point. The sound waves propagated at a predetermined angle are received on both sides of the vertical plane including the predetermined point. The sound wave received by each sound wave receiving unit in this way has a frequency different from the frequency at the time of transmission due to the Doppler effect, and the frequency change amount (the above-mentioned “Doppler shift frequency”) f
_d1 and _fd2 are detected by the Doppler shift frequency detecting means.

Here, among the sound waves transmitted by the sound wave transmitting means and reflected from the predetermined point, the two sound wave receiving means propagate at predetermined angles to both sides of the vertical plane including the predetermined point. Since the received sound waves are received, in the slip angle calculation means, for example, the detected Doppler shift frequencies f _d1 and f _d2 , the reception axis of each of the sound wave reception means and the transmission axis of the sound wave transmission means are The slip angle at the predetermined point can be calculated using the projection angle of the angle formed by the road surface, the angle formed by the transmission axis and the road surface, and the angle formed by each reception axis and the road surface. That is, in this device, the slip angle is calculated from a calculation formula that does not include the term of sound velocity.

Particularly, according to the slip angle measuring device of the second aspect, in the correcting means of the slip angle calculating means, for example, the predetermined point on the road surface corresponding to the measurement point of the Doppler shift frequency and the ground contact point of the tire are set. Sound waves are transmitted / reflected by the distance, the turning speed detection value from the turning speed detection means, and the wheel speed detection value from the wheel speed detection means (speed in the traveling direction of the wheel at the predetermined point). The tire slip angle calculated as the value at the predetermined point is corrected and calculated to be the value at the ground contact point of the tire (the center point of the wheel in plan view). With this, in the device, in the case of measuring the tire slip angle, it is possible to prevent the measurement accuracy from deteriorating due to the inability to match the predetermined point with the ground contact point of the tire.

Further, in the slip angle measuring device according to the first aspect, the sound wave transmitting means transmits a sound wave, and the sound wave receiving means receives the transmitted sound wave after the sound wave is reflected on a road surface. Since the sound wave receiving means also moves from the position at the time of sound wave transmission by the sound wave transmitting means as the vehicle travels, when the sound wave to be used has high sensitivity directivity like an ultrasonic wave, Depending on the reception directivities of the two sound wave receiving means, there is a possibility that the sound wave reflected by the sound wave receiving means around the predetermined point may not be received by each of the sound wave receiving means during traveling at high speed.

On the other hand, according to the slip angle measuring device of the third aspect, the sound wave used in the slip angle measuring device of the first aspect is achieved by setting the predetermined vehicle speed to, for example, the assumed maximum vehicle speed of the vehicle. Even if the ultrasonic wave has a high sensitivity directivity, it is possible to reliably receive the sound wave reflected at the predetermined point by each sound wave receiving means when traveling at a high speed.

[0018]

Embodiments of the slip angle measuring device according to each of the inventions will be described below with reference to the drawings. First, the ultrasonic sensor 1 that constitutes the first embodiment of the slip angle measuring apparatus will be described with reference to FIGS.

As shown in FIG. 2, the ultrasonic sensor 1 includes an ultrasonic transducer (sound transmitting means) 11 for transmission, ultrasonic transducers (sound receiving means) 12, 13 for reception, and a predetermined ultrasonic transducer. A plate-shaped mount 14 formed in the shape of FIG. 3 and fixing the vibrating surfaces of the ultrasonic transducers 11 to 13 at predetermined positions, and a housing 15 that protects the mount 14 and the ultrasonic transducers 11 to 13. Consists of.

In the mount 14, as shown in FIGS. 3 to 5, triangular plate-shaped end members 17 and 18 are continuous in the same direction at predetermined angles on both ends in the length direction of a long plate 16 having a predetermined length. ,
Further, the auxiliary plate 19 having the same shape as the long plate 16 has a shape in which end faces in the width direction are overlapped with the long plate 16 and are continuous at a predetermined angle. Also, the end members 17, 18 of the auxiliary plate 19
The surface on the side is a reference surface 19a that serves as a reference when mounted on the vehicle.
_The reference plate 19a forming ₁ is fixed.

At the center position in the length direction of the long plate 16, a mounting hole 1 in which a vibrating body of an ultrasonic transducer 11 for transmission is arranged.
6a is opened, and mounting holes 17a, 18a in which the vibrating bodies of the ultrasonic transducers 12, 13 for reception are arranged are formed at substantially the center positions of the end members 17, 18. Then, the center line O ₁ of the mounting hole 16a of the ultrasonic transducer 11 for transmission is
Corresponding to the transmission axis a _S of the ultrasonic sensor 1, the center lines O ₂ and O _{3 of the} mounting holes 17a and 18a of the ultrasonic transducers 12 and 13 for reception are the two lines of the ultrasonic sensor 1. to accommodate the reception axis a _r1, a _r2, a center line O ₁ of the mounting hole 16a
The angle ω between the center lines O ₂ and O ₃ of the mounting holes 17a and 18a is a value corresponding to the angle between the transmission axis a _S and the reception axes a _r1 and a _{r2 in} the preset sensor geometry. The angle ω that connects the long plate 16 and the end members 17 and 18 is set so that Further, the center-to-center distances L ₆₇ , L between the mounting holes 16a and the mounting holes 17a, 18a in a plan view.
₆₈ are equal to each other.

In a side view of the mount 14, the center lines O ₁ , O ₂ , O _{3 of the} mounting holes 16a, 17a, 18a are shown.
Are coincident with each other, and an angle γ formed by these center lines O ₁ , O ₂ , O ₃ and the end faces 14 a (installed parallel to the road surface) of the end members 17, 18 and the long plate 16 is set in advance. Transmit axis a _S and each receive axis a in the specified sensor geometry
_The angle δ for connecting the auxiliary plate 19 and the long plate 16 is set so that the angle (θ _rS ) formed by _r1 and a _r2 and the road surface is formed. The auxiliary plate 19 and the reference plate 19a are provided with mounting holes 19b and 19c communicating with corresponding positions, respectively, and the ultrasonic sensor 1 as a whole is mounted at a predetermined position on the vehicle in these mounting holes 19b and 19c. To be

The reference plate 19a is made of a plate material having a smaller thickness and a slightly smaller width and length than the auxiliary plate 19, and the end face in the width direction is located near the fold line connecting the auxiliary plate 19 and the long plate 16. Together, they are arranged parallel to the auxiliary plate 19. The step 19 between the auxiliary plate 19 and the reference plate 19a caused by this
The mount 14 is attached to the housing 15 using b.

It should be noted that the inner surface of the long plate 16 and the end members 17 and 18 constituting the mount 14 (the surface which becomes the front surface when attached to the housing 15) and the mounting holes 16a,
17a and 18a and the reference surface 19a ₁ of the reference plate 19a are processed with high surface accuracy, and each ultrasonic transducer 11,
Vibrator mounting holes 16a of 12, 13, 17a, when attached to 18a, and the angle between the transmission axis a _S and the receiving shaft a _r1, a _r2 in preset sensor geometry, transmission shaft a _S and The angle (θ _rS ) formed by each of the receiving axes a _r1 , a _r2 and the road surface is precisely maintained, and when the ultrasonic sensor 1 is mounted on the vehicle, the preset sensor geometry is precisely It is held.

FIG. 6 is a partial sectional view showing a mounting state of the ultrasonic sensor 1 on a vehicle. As can be seen from this figure, the slip angle measuring device of this embodiment measures the slip angle of the tire, and the ultrasonic sensor 1 described above is
Only the rotation of the wheel 110 in the rolling direction is restrained, and in the other directions, it is attached to the vehicle via the attachment member 5 so as to be synchronized with the movement of the wheel 110.

That is, the ultrasonic sensor 1 is directly
The mount 1 is attached to the plate-shaped mounting portion 55 arranged below the wheel rotation axis on the outside of the wheel 110 in the mounting member 5.
The four reference plates 19 are superposed and fixed. The mounting member 5 is a cylindrical wheel-side member 51 mounted on the wheel hub 111, and is arranged outside the wheel-side member 51 via a bearing 52, and mounted on the vehicle body 100 via a rotation restraining member 53. The vehicle body side member 54 and the mounting portion 55 integrally formed with the vehicle body side member 54.

The wheel side member 51 is the wheel hub 11.
1 has a shape in which a small-diameter portion 51a having almost the same diameter as that of a large-diameter portion 51b having a slightly larger diameter is continuous, and a through-hole 51c parallel to the axial direction of the cylinder is aligned with the mounting hole of the wheel hub 111. Is open. A groove 51e into which the inner ring 52a of the bearing 52 is fitted is formed on the outer circumference of the large diameter portion 51b.

The vehicle body side member 54 is composed of a cylinder 54a and a bottom plate 54b which closes one end surface of the cylinder 54a. The outer ring 52b of the bearing 52 is provided on the inner periphery of the cylinder 54a on the open end side.
Is formed with a groove 54c. Also, the bottom plate 54
Has a plate-shaped mounting portion 55, which is thinner than the bottom plate 54, on which the reference plate 19a of the ultrasonic sensor 1 is superposed.
The bottom plate 54 and the outer surface are formed so as to be continuous with each other, and the outer surface of the mounting portion 55 is the reference surface 19 of the reference plate 19a.
It is formed with strict surface accuracy equivalent to that of a ₁ . Further, one end of the rotation restraint member 53 is connected to the side of the outer surface of the bottom plate 54 facing the mounting portion 55.

The rotation restraining member 53 includes a rod-shaped first horizontal member 53a extending horizontally from the vehicle body 100 to the outside.
A rod-shaped second horizontal member 53c connected to the first horizontal member 53a via a connecting member 53b, and a rod-shaped vertical member 53e connected to the second horizontal member 53c in a vertically downward direction via a connecting member 53d. The tip end of the vertical member 53e is formed of a connecting member 53f with the vehicle body side member 54. The connecting member 53b is the second horizontal member 53c.
However, it permits rotation around a point on the side of the connecting member 53b on a horizontal plane of a predetermined height, and the connecting member 53d has the vertical member 53e of the second horizontal member 53c. On the vertical plane formed by the tangent of the rotating circle,
It is allowed to rotate around one point of the end of the connecting member 53d.

In the mounting member 5, the bolt 5a press-fitted into the wheel hub 111 is inserted into the small diameter portion 51a of the through hole 51c of the vehicle body side member 51, and the nut inserted into the bolt 5a from the large diameter portion 51b side. After screwing 51d, the body side member 54 is press-fitted into the bearing 52,
It is attached to the wheel 110. Further, the tip end of the first horizontal member 53a of the rotation restraining member 53 whose vertical member 53e side is connected to the vehicle body side member 54 of the mounting member 5 by the connecting member 53f is fixed to the vehicle body 100 by the mounting metal fitting 53g. As a result, the mounting member 5 is mounted on the vehicle body 100.

As a result, the mounting member 5 is attached to the wheel 11
With the rotation of 0 in the rolling direction, only the wheel side member 51 rotates integrally with the wheel 110, but the vehicle body side member 54 does not rotate in the rolling direction of the wheel 110 due to the rotation restraining member 53. However, with respect to other behaviors in which the wheel 110 changes its direction or posture changes in the front-rear direction of the vehicle body 100, the action of the rotation restraining member 53 causes the vehicle body-side member 54 to move.
Operates together with the wheel-side member 53 to allow this.

In this way, the mounting member 5 is attached to the vehicle body 100.
And the reference plate 19 of the ultrasonic sensor 1 with respect to the outer surface of the mounting portion 55 arranged on the lower side as a result of being mounted on the wheel 110.
Are superposed on each other and fastened by bolts from the mounting portion 55 side, whereby the ultrasonic sensor 1 is located at a predetermined position outside the wheel 110 (a position where a measurement road surface is secured between the ultrasonic sensor 1 and the wheel 110). It is attached.

Next, the signal processing device 2 for operating the ultrasonic sensor 1 to calculate the slip angle will be described with reference to FIG. As shown in FIG. 7, the slip angle measuring device of this embodiment includes a yaw rate sensor (turning speed detecting means) 3 installed at the center of gravity of the vehicle body, and a display device 4 for displaying the measured slip angle. Is equipped with. This signal processing device 2 includes a transmission circuit (sound wave transmission means) 21, a first reception circuit (sound wave reception means) 22, a second reception circuit (sound wave reception means) 23, a first Doppler shift frequency calculation circuit (Doppler shift frequency detection). Means) 24, second Doppler shift frequency calculation circuit (Doppler shift frequency detection means) 2
5. Slip angle calculation circuit (slip angle calculation means) 26,
A wheel speed detection circuit (wheel speed detection means) 27 and a correction circuit (correction means) 28 are included.

The transmission circuit 21 outputs a voltage signal CS _S for oscillating an ultrasonic wave of a predetermined frequency f _S to the ultrasonic transducer 11 for transmission, and the first and second Doppler shift frequency calculation circuits. A signal corresponding to the transmission frequency f _S is output to 24 and 25. Therefore, for example, an oscillation circuit using a crystal oscillator or the like and a power amplification transistor are provided.

The first and second receiving circuits 22 and 23 receive the ultrasonic voltage signals CS _r1 and CS _r2 received by the receiving ultrasonic transducers 12 and 13, and receive the voltage signal C
The frequencies f _r1 and f _r2 of the ultrasonic waves received by the ultrasonic transducers 12 and 13 are calculated from S _r1 and CS _r2 , and these frequencies f _r1 and f
A signal corresponding to _r2 is output to the first and second Doppler shift frequency calculation circuits 24 and 25. Therefore, it is equipped with an amplification function, a filtering function, a detection function, a wave shaping function, and a counter function.

The first and second Doppler shift frequency calculation circuits 24 and 25 are connected to the first and second reception circuit 2 respectively.
And a frequency f _r1, f _r2 inputted as the transmission frequency f _S which is input from the transmitting circuit 21 from 2,23, the deviation (f _r1 -f _S), Doppler corresponding to (f _r2 -f _S) The shift frequencies f _d1 and f _d2 are calculated, and a signal corresponding to these values is sent to the slip angle calculation circuit 26 and the wheel speed detection circuit 27.
It is output to and and is composed of a subtractor.

Then, the slip angle calculating circuit 26 is
From the Doppler shift frequency f _d1 from the first Doppler shift frequency calculation circuit 24, the Doppler shift frequency f _d2 from the second Doppler shift frequency calculation circuit 25, and various angle data according to the set sensor geometry, The slip angle α _P at one point P on the measured road surface is calculated based on the calculation formula described in detail later, and a signal corresponding to this value is output to the wheel speed detection circuit 27 and the correction circuit 28 2. For that purpose, it is provided with a multiplier, a divider, an adder / subtractor, an arithmetic unit, a memory, and the like.

Further, the wheel speed detection circuit 27 determines the wheel speed (speed in the traveling direction of the wheel) V at a point P on the measured road surface.
_P is a transmission frequency f _S from the transmission circuit 21, a Doppler shift frequency f _d1 from the first Doppler shift frequency calculation circuit 24, a sound velocity C _S stored in advance, and a prestored subsequent stage. Using the angle corresponding to the sensor geometry and the slip angle α _{P at} the point P from the slip angle calculating circuit 26, the calculated wheel speed V _P is calculated based on the calculation formula detailed later. The correction circuit 28
Is output to For that, multipliers, dividers,
It is provided with an adder / subtractor, a computing unit, a storage unit and the like.

Further, the correction circuit 28 includes the slip angle α _P from the slip angle calculation circuit 26, the wheel speed V _P from the wheel speed detection circuit 27, and the yaw rate sensor 3
By using the yaw rate detection value φ from, the slip angle α at the tire ground contact point is calculated based on the calculation formula detailed later, thereby correcting the deviation between the measurement point and the tire ground contact point. And outputs a signal corresponding to the calculated slip angle α to the display device 4. For that purpose, it is provided with a multiplier, a divider, an adder / subtractor, an arithmetic unit, a memory, and the like.

Here, the slip angle calculating circuit 26,
Formulas for calculating each physical quantity used in the wheel speed detection circuit 27 and the correction circuit 28 will be described. First, the formula for calculating the slip angle α _P at one point P on the measured road surface used in the slip angle calculation circuit 26 will be described. FIG. 8 is a perspective view showing the sensor geometry of the ultrasonic sensor 1 in this embodiment, FIG. 9 (a) is its plan view, and FIG. 9 (b) is its rear view.

As can be seen from FIG. 8, in this embodiment,
The tire center line corresponding to the rolling direction of the wheel 110 is the X axis.
Is parallel to the X axis and is located outside the wheel 110.
X away by a fixed distance_SEach ultrasonic transducer 11 along the axis
Set the ultrasonic sensor so that the center of the vibration surface of
The service 1 is attached to the vehicle. In addition, each ultrasonic vibration
The center of the vibrating surface of the pendulums 11 to 13 is parallel to the X axis and
X_SX between the axis _PAxis (X_SX_PDistance: L_Y)
And the road at the intersection of the Y axis corresponding to the rotation axis of the wheel 110.
It is directed to the point P corresponding to the projection point on the surface. And this
V in the traveling direction of the wheel at point P_PAnd

Therefore, the ultrasonic wave transmitted from the ultrasonic transducer 11 for transmission is reflected around this point P and is received by the ultrasonic transducers 12 and 13 for reception. Here, the angles formed by the receiving axes a _r1 and a _{r2 of the} ultrasonic transducers 12 and 13 and the transmitting axes a _S of the ultrasonic transducers 11 are θ _d1 and θ, respectively.
_{Let d2} be the projection angles of these angles θ _d1 and θ _{d2 on} the road surface, that is, θ _d1 ′ and θ _d2 ′, respectively. The angle between the transmission axis a _S and the road surface is θ _S, and the angle between the reception axes a _r1 and a _r2 and the road surface is θ _rS1 and θ _rS2 , respectively. Also,
As can be seen from FIG. 9B, the ultrasonic sensor 1 is installed below the Y axis at a height L _Z from the road surface.

Here, since the ultrasonic sensor 1 also moves integrally with the traveling of the vehicle, the frequency of the ultrasonic wave transmitted from the ultrasonic transducer 11 depends on the Doppler effect and the measured road surface centered on the point P. At the time of reflection at, the value becomes a value shifted from the transmission frequency f _S by an amount corresponding to the sensor geometry and the wheel speed vector V _P. Furthermore, the ultrasonic transducers 12, 1
Due to the Doppler effect, the frequencies f _r1 and f _r2 of the ultrasonic waves received by the sensor 3 and the wheel speed vector V
It becomes a value further shifted from the frequency of the reflected ultrasonic wave by an amount corresponding to _P and.

As can be seen from FIG. 9A, the wheel speed vector V _P in the traveling direction of the wheel at the point P and the wheel in the receiving axis direction detected by the ultrasonic transducer 12 for reception are seen in a plan view. The angle formed by the velocity vector V ₁ is θ ₁ ,
If the angle formed by the reception ultrasonic transducer 13 and the wheel speed vector V _{2 in the} direction of the receiving axis is θ ₂ , these angles θ ₁ and θ _{2 form} the X _P axis and the vector V _P. The tire slip angle α _P at the point P corresponding to the angle and each receiving axis a
It is represented by projection angles θ _d1 ′ and θ _d2 ′ on the road surface, which are angles formed by _r1 and a _r2 and the transmission axis a _S.

Therefore, by the ultrasonic transducers 12 and 13,
Frequency f of received ultrasonic wave_r1, F _r2Of the transmission frequency f
_SDeviation (f_r1-F_S), (F_r2-F_S) Is equivalent to
Doppler shift frequency f_d1, F_d2These angles
α_P, Θ_d1’, Θ_d2'And each receiving axis a_r1, A_r2And send axis
a_SAngle between the road surface and_S, Θ_rS1, Θ_rS2And the speed of sound
C _SAnd the vehicle speed vector V_PUsing and, the following equation (4)
And expressed by equation (5).

[0046]

[Equation 1]

[0047]

[Equation 2]

Since the denominators of the equations (4) and (5) are equal to each other, the ratio of the Doppler shift frequencies f _d1 and f _d2 R _f = (f _d2 / f _d1 ) A relational expression between the Doppler shift frequencies f _d1 and f _d2 and the tire slip angle α _P at the point P, which does not include _S , is obtained. The relational expression is shown in the following expression (6).

[0049]

(Equation 3)

By modifying the equation (6), the following equation (7) is obtained,

[0051]

[Equation 4]

Dividing both sides of equation (7) by sin α _P gives
The following equation (8) is obtained,

[0053]

(Equation 5)

When this equation (8) is rearranged in terms of the slip angle α _P , the following equation (11) is obtained through the following equations (9) and (10),

[0055]

(Equation 6)

[0056]

(Equation 7)

[0057]

(Equation 8)

The slip angle α _P is expressed by the following equation (12).

[0059]

[Equation 9]

In particular, in the sensor geometry of this embodiment
Is L_X1= L_X2Because θ_d1’= Θ _d2’And θ_rS1=
θ_rS2Therefore, the above equation (12) is θ_d1’= Θ_d2’= Θ
_d’, Θ_rS1= Θ_rS2= Θ_rSAs in equation (13) below
Organized,

[0061]

[Equation 10]

When R _f in the equation (13) is replaced by (f _d2 / f _d1 ) and the proportional constant K ₁ according to the sensor geometry is defined as follows, the slip angle α _P becomes
It is expressed by the equation 4).

[0063]

[Equation 11]

However, K ₁ = sin θ _d '・ cos θ _rS / (c
_{osθ d '· cosθ rS + cosθ} S) Therefore, in the storage unit of the slip angle calculating circuit 26, the proportional constant K ₁ depending on the sensor geometry is stored, this proportional constant K _1, a first Doppler shift frequency From the Doppler shift frequency f _d1 from the calculation circuit 24 and the Doppler shift frequency f _d2 from the second Doppler shift frequency calculation circuit 25, the tire slip angle α _{P at the} point _P is calculated using the equation (14). So the multiplier,
An adder / subtractor, a divider, a calculator, and a memory are connected.

Next, the wheel speed detecting circuit 27 is used.
Wheel speed V at the point P _PAbout the calculation formula of
explain. In the above equation (4), the sound velocity C_SThe wheels
Speed V_PAnd (sin α_P cos θ_S) Is much larger than the product of
Therefore, the denominator of equation (4) above is almost C_SEqual to
Can be Accordingly, the above equation (4) is
Equation (15) becomes,

[0066]

(Equation 12)

By modifying the equation (15), the wheel speed V _{P at the} point P can be expressed by the following equation (16).

[0068]

(Equation 13)

Therefore, in the memory of the wheel speed detection circuit 27, the angles θ _d1 ′, θ _rS1 ,
θ _S and sound velocity C _S are stored, and these angles θ _d1 ′, θ _rS1 , θ _S and sound velocity C _S , the Doppler shift frequency f _d1 from the first Doppler shift frequency calculation circuit 24, and the transmission circuit A multiplier and an adder / subtractor are used so that the wheel speed V _{P at the} point _P can be calculated from the transmission frequency f _S from 21 and the slip angle α _P from the slip angle calculation circuit 26 using the above equation (16). , A divider, a calculator, and a memory are connected.

Next, the formula for calculating the slip angle α at the tire ground contact point used in the correction circuit 28 will be described with reference to FIG. Tire slip angle α at point P calculated by the slip angle calculation circuit 26
_P is equal to the slip angle at the ground contact point A of the tire (the value actually required as the tire slip angle) when the turning speed of the vehicle body is "0", but in actual vehicle behavior, the turning speed of the vehicle body is In consideration of the above, it is necessary to correct the distance E corresponding to the deviation between the point P and the ground contact point A.

FIG. 10 (a) is a plan view showing the arrangement of the ultrasonic sensor 1 with respect to the vehicle, and FIG. 10 (b) shows the difference between the velocity vectors at points P and A, taking the rear left wheel as an example. FIG. In FIGS. 10A and 10B, CG is the center of gravity of the vehicle body, CLv is the center line in the width direction of the vehicle body (hereinafter referred to as the “vehicle body center line”), and the X axis is the wheel rolling as in FIG. Direction, tire center line, _XP
Similar to FIG. 8, the axis is a line parallel to the X axis and passing through the point P, H is the intersection of the straight line passing through the points P and A (perpendicular to the vehicle body center line CLv) with the vehicle body center line CLv, and C is the center of gravity. The distance between GC and the point H, the distance between the point A and the point H, the distance between the point P and the point A, the distance between the center of gravity GC and the point A, the point G between the center of gravity GC and the point P, Is the distance.

As shown in FIG. 10B, the vehicle body center line C
Considering the case where the Lv and the X axis are parallel, if the vehicle speed vector is V _V and the turning speed (yaw rate) of the vehicle is φ,
The wheel speed vector V _A at the point A, which is the tire ground contact point, is the vehicle speed vector V _V translated from the center of gravity GC to the point A,
It is the sum of the turning speed vector (F · φ) generated in the tangential direction of the turning radius when turning. The tire of the angle between the wheel speed vector V _A and X axis at this point A, the tire slip angle alpha next to the A point is a tire ground contact point, and the true tire slip angle alpha, with the point P It can be seen that there is a shift angle ε with the slip angle α _P.

Here, the vehicle body slip angle (vehicle body center line CL
The angle between v and the vehicle speed vector V _V ) is β, and point A
Decomposing the wheel speed vector V _A at X into a component in the X-axis direction and a component in the Y-axis direction perpendicular to the X-axis, the X component V _AX is the following equation (17), and the Y component V _AY is It is expressed by equation (18). V _AX = V _V · cos β + D · φ ··· (17) V _AY = V _V · sin β-C · φ ··· (18) Further, the wheel speed vector V _P at the point P is the component in the X-axis direction. And the component in the Y-axis direction perpendicular to the X-axis, the X-component V _PX is expressed by the following equation (19) and the Y-component V _PY is _calculated by the following (2)
It is represented by the formula 0).

V _PX = V _V · cos β + (D + E) φ (19) V _PY = V _V · sin β−C · φ (20) From these equations, the X component V of each wheel speed vector _AX , V _PX
Is expressed by the following equation (21), and the relationship between the Y components V _AY and V _PY is expressed by the following equation (22). V _AX = V _PX −E ···················· (21) V _AY = V _PY ································· (22) Therefore, from these expressions, the true tire slip angle α at the point A is the following (23) It is represented by.

Α = tan ⁻¹ (V _AY / V _AX ) = tan ⁻¹ (V _PY / (V _PX −E · φ)) (23) On the other hand, the wheel speed vector V _P at the point P X component V _PX is (V
_P cos α _P ), and the Y component V _PY is (V _P sin α _P ). Therefore, by substituting these into the above equation (23) and transforming, the true tire slip angle α can be calculated as
The following equation (24) is obtained.

[0076]

[Equation 14]

As can be seen from the equation (24), when the yaw rate φ is “0”, α = α _P and the tire slip angle α at the ground contact point A becomes equal to the tire slip angle α _P at the point P. , Φ ≠ 0, the yaw rate φ and the distance E
And the wheel speed V _P have different values. Figure 11
Is the tire slip angle α _P at the point P when the distance E is 0.2 m and the wheel speed V _P is 13.9 m / s.
7 is a graph showing the relationship between the measurement error and the yaw rate when the tire slip angle α in FIG. As can be seen from this figure, since the measurement error of the slip angle increases in proportion to the yaw rate, the yaw rate φ is directly detected by the yaw rate sensor 3 and the distance E is corrected as in this embodiment. Even from the slip angle α _P measured at a point P different from the tire ground contact point A, the slip angle α at the tire ground contact point A can be accurately detected.

Therefore, the memory E of the wheel speed detection circuit 28 stores the distance E between the tire ground contact point A and the point P. With the configuration described above, in the slip angle measuring device of this embodiment, when the tire slip angle measurement is started at the same time as the ignition is turned on, the voltage is transmitted from the transmission circuit 21 to the ultrasonic transducer 11 for transmission. Signal CS _S
And the transmission frequency f _S toward the first and second Doppler shift frequency calculation circuits 24 and 25.
Is output. Along with this, from the ultrasonic transducer 11 for transmission toward the road surface (the road surface centering on the point P) corresponding to the sensor geometry described above (see FIG. 8),
Ultrasonic waves having a predetermined frequency f _S are transmitted. The transmitted ultrasonic waves are reflected on the road surface and are received by the ultrasonic transducers 1
2, 13 are received. Then, the ultrasonic voltage signal CS _r1 received by the ultrasonic transducer 12 is input to the first receiving circuit 22, and the ultrasonic voltage signal CS _r2 received by the ultrasonic transducer 13 is changed by the second receiving circuit 23. Is entered.

Accordingly, the frequencies f _r1 and f _{r2 of the} ultrasonic waves received by the ultrasonic transducers 12 and 13 are calculated in the receiving circuits 22 and 23, and the signal corresponding to the frequency f _r1 is the first Doppler signal. The shift frequency calculation circuit 24 _displays the frequency f _r2
The signal corresponding to is the second Doppler shift frequency calculation circuit 2
5 is output. Here, as described above, the frequencies f _r1 and f _r2 of the ultrasonic waves received by the Doppler effect are different from the transmission frequency f _S, and in the Doppler shift frequency calculation circuits 24 and 25, Deviation ( _fr1
The Doppler shift frequencies f _d1 and f _d2 corresponding to −f _S ), ( _{fr 2} −f _S ) are calculated, and these values are output to each slip computing circuit 26. The Doppler shift frequency f _d1 is also output to the wheel speed detection circuit 27.

Then, in the slip angle calculation circuit 26, the Doppler shift frequency f _d1 from the first Doppler shift frequency calculation circuit 24 and the Doppler shift frequency f from the second Doppler shift frequency calculation circuit 25 are calculated.
_{From d2} and the proportional constant K ₁ stored in advance, the above (1
The tire slip angle α _{P at the} point P is calculated based on the equation 4), and this value is output to the correction circuit 28. On the other hand, in the wheel speed detection circuit 27, the angles θ _d1 ′, θ _rS1 , θ _S and the sound velocity C _S stored in advance, the Doppler shift frequency f _d1 from the first Doppler shift frequency calculation circuit 24, and the transmission circuit 21 are stored. Of the wheel speed V _{P at the} point P from the transmission frequency f _{S of the above} and the slip angle α _P from the slip angle calculation circuit 26, and this value is output to the correction circuit 28. It

Accordingly, in the correction circuit 28, the slip angle α _P from the slip angle calculation circuit 26, the wheel speed V _P from the wheel speed detection circuit 27, and the yaw rate detection value φ from the yaw rate sensor 3 are obtained. From the above (24)
The slip angle α at the tire ground contact point is calculated based on the equation, and this value is output to the display device 4. Then, for example, the measured value of the tire slip angle α at the present time is displayed on the display device 4.

Next, stabilization of the reception gain of the ultrasonic sensor 1 will be described. As shown in FIG. 8 described above, in the ultrasonic sensor 1 of this embodiment, the reception axes a _r1 and a _{r2 of the} ultrasonic waves reflected from the measurement road surface centered on the point P are the ultrasonic transducers for reception. The ultrasonic sensors 1 and 12 are arranged so as to coincide with the centers of the vibration planes of the vehicle, so that the ultrasonic sensor 1 according to the traveling of the vehicle 1
If the movement of is ignored, the reflected ultrasonic wave can be received with the maximum gain. However, in reality, the traveling speed of the vehicle is about 1/10 of the traveling speed with respect to the sound speed in normal traveling, and therefore the movement of the ultrasonic sensor 1 mounted on the vehicle due to traveling of the vehicle cannot be ignored. In particular, since ultrasonic waves have high sensitivity directivity, there is a difference between when ultrasonic waves are transmitted from the ultrasonic transducer 11 and when ultrasonic waves are reflected by the road surface and received by the ultrasonic transducers 12 and 13. It is unavoidable that the reception gain of the ultrasonic transducers 12 and 13 decreases due to the change in the positions of the ultrasonic transducers 12 and 13 for reception.

FIG. 12 (a) is a plan view showing a change in the ultrasonic wave propagation path as the vehicle travels.
2 (b) is a side view thereof. As can be seen from these figures, the ultrasonic transducers 12 and 13 for reception, which were present at the positions P ₁ and P ₂ at a certain point in time, were transmitted to the ultrasonic transducers 12 and 13 at this point as the vehicle traveled. At the time when the ultrasonic waves transmitted from 11 toward the road surface are reflected around the point P and reach the ultrasonic transducers 12 and 13 for reception, the position P ₁ ′,
It has moved to P ₂ '.

Here, the ultrasonic transducers 12 and 13 for reception are used.
Point P ₁ and P ₂ respectively exist at the point P 1.
_Let L _r1 and L _r2 be the propagation paths of the ultrasonic waves reflected around (the center line of the propagated ultrasonic waves), and the ultrasonic transducers 12 and 13 for reception are at positions P ₁ ′ and P ₂ ′, respectively. If the propagation paths of the ultrasonic waves reflected around the point P are L _r1 'and L _r2 ' respectively, the propagation path L
_The deviation angle between _r1 and L _r1 '(Δθ _d1 ' in plan view, Δθ _rS1 'in side view) and the deviation angle between propagation paths L _r2 and L _r2 ' (Δθ _d2 'in plan view, side view Δ
By the amount of θ _rS2 '), the reception axes a _r1 and a _r2 of the ultrasonic waves are deviated from the centers of the vibrating surfaces of the ultrasonic transducers 12 and 13 for reception.

Further, the movement vector P ₁ P in plan view
₁ ', P ₂ P ₂ ' is the tire slip angle α at point P
_It is tilted from the X _S axis by _P, but is hardly tilted from the X _S axis in a side view. This is because the installation height of the ultrasonic sensor 1 and the distance between the road surface and the road surface are short, so that it takes a short time for the ultrasonic waves reflected on the road surface to reach the ultrasonic transducers 12 and 13 for reception, and usually the vehicle This is because the moving speed in the vertical direction is smaller than the traveling speed of the vehicle. Therefore, regarding the movement of the ultrasonic sensor 1 as the vehicle travels, it is sufficient to consider only the movement on the horizontal plane at the installation height.

Therefore, in this embodiment, the maximum values of the deviation angles Δθ _d1 ′, Δθ _rS1 ′, Δθ _d2 ′ corresponding to the assumed maximum vehicle speed are effectively directed as the ultrasonic transducers 12 and 13 for reception. By selecting a half-width, the ultrasonic waves reflected from the road surface can be received with a high gain even when the vehicle travels at the maximum vehicle speed. Further, the reception gain can be stabilized by processing the diaphragm of a predetermined ultrasonic transducer or attaching an acoustic lens.

As shown in FIGS. 13 and 14,
The sensor geometry for ultrasonic transmission / reception is shown in Fig. 8 above.
If it is different from that shown in FIG. 9, the method of calculating the slip angle α _P in the slip angle calculation circuit 26 is different. FIG.
3 and 14, (a) is a plan view of the respective sensor geometries, similar to (a) of FIG. 9 described above, and (b).
FIG. 3 is a side view of each sensor geometry.

In the sensor geometry of FIG.
As can be seen from (a), it corresponds to the rotation axis of the wheel 110.
Parallel to the Y-axis and separated by a predetermined distance on the side opposite to the traveling direction
Was Y _SVibration of each ultrasonic transducer 11-13 along the axis
As shown in Figure 3 above, so that the center of the plane is located
The same ultrasonic sensor 1 is attached to the vehicle. Well
In addition, the center of the vibration surface of each ultrasonic transducer 11 to 13 is the wheel.
The tire center line corresponding to the rolling direction of 110 is the X axis.
When it is turned on, it is parallel to the X-axis and a predetermined distance outside the wheel 110.
X away_PPoint on the road surface at the intersection of the axis and the Y axis
To the point P corresponding to. Also, the ultrasonic sensor 1
As can be seen from FIG. 13B, is below the Y axis,
The height from the road is L_ZIt is installed at

That is, this sensor geometry corresponds to the sensor geometry of FIGS. 8 to 9 rotated clockwise by 90 ° in a plan view around the point P, and the tire slip angle α _P at the point _P is Slip angle calculation circuit 2 in FIG.
6 is calculated using the following equation (25) having a proportional constant different from that of the equation (14).

[0090]

(Equation 15)

However, K ₂ = (cos θ _d '· cos θ _rS + cos
_{θ S) / (sinθ d '} · cosθ rS) On the other hand, in the sensor geometry of Figure 14, as can be seen from FIG. 14 (a), the tire center line corresponding to the rolling direction of the wheel 110 when the X-axis, The X _P axis parallel to the X axis and separated from the wheel 110 by a predetermined distance, and the wheel 11
The center of the vibrating surface of the ultrasonic transducer 11 for transmission is arranged at an intersection with the Y _SS axis which is parallel to the Y axis corresponding to the 0 rotation axis and is separated from the traveling direction by a predetermined distance. Then, Y _Sr parallel to the Y-axis and separated from the traveling direction by a predetermined distance
Along the axis, the points different distances across the X _P axis, the center of the vibration surface of the ultrasonic transducer 12, 13 for reception are arranged. Further, as can be seen from FIG. 14B, the ultrasonic transducers 11 to 13 are installed at positions below the Y-axis and at different heights from the road surface. the center of the plane of vibration of to 13, the point P corresponding to the projection point of the road surface at the intersection of the X _P axis and Y-axis, are directed respectively in different depression angle _{(θ S ≠ θ rS1 ≠ θ} rS2).

In this way, the ultrasonic transducer 11 for transmission and the ultrasonic transducers 12, 13 for reception are connected to the measurement road surface (point P).
In the case of arranging the ultrasonic transducers 11 to face each other with sandwiching them, the ultrasonic transducers 11 to 13 are not collectively arranged according to the sensor geometry as in the ultrasonic sensor 1 shown in FIG. Further, in this sensor geometry, unlike the sensor geometries of FIGS. 8 to 9 and FIG. 13, θ _S ≠ θ _rS1 ≠ θ _rS2 and θ _d ′ ≠ θ _d1 ′ ≠ θ
_Since it is _d2 ', R _{f is changed} to (f _d2
/ F _d1 ), and defining constants G ₁₁ , G ₁₂ , G ₂₁ , and G ₂₂ relating to these angles as follows, the tire slip angle α _{P at the} point P is expressed by the following equation (26). It

[0093]

[Equation 16]

However, G ₁₁ = sin θ _d1 '・ cos θ _rS1 G ₁₂ = cos θ _d1 ' ・ cos θ _rS1 G ₂₁ = sin θ _d2 '・ cos θ _rS2 + cos θ _S G ₂₂ = cos θ _d2 ' ・ cos θ _rS2 + cos θ _S The calculation formula of the tire slip angle at the point P is derived in advance according to the sensor geometry selected by the mounting restrictions on the sound wave transducers 11 to 13 and the setting of the detection resolution of the Doppler shift frequency. It suffices to calculate the proportional constants and the like to be used in step 1 and form the slip angle calculation circuit 26 in accordance with the calculated constants.

Thus, the slip angle of the first embodiment is
According to the measuring device, the slip velocity calculation formula includes the term of sound velocity.
Therefore, compared to conventional equipment, the tire sliding
Angle α_PCan be measured. However, the car
The wheel speed V is detected by the wheel speed detection circuit 27. _PThe formula for calculating
Since the term is included, equipped with a temperature sensor and near point P
Value of sound velocity to be used according to the detected temperature
By setting, a more accurate correction can be made in the correction circuit 28.
It is more preferable because it is made.

FIG. 15 is a block diagram showing a schematic configuration of a second embodiment of the slip angle measuring device according to each of the inventions, and FIG. 16 is a plan view showing a sensor geometry in this device. As can be seen from FIG. 15, the apparatus according to the present embodiment has an ultrasonic transducer (sound wave transmission means, sound wave reception means) 10A for both transmission and reception, and an ultrasonic transducer (sound wave reception means) dedicated to reception. ) 10B, a signal processing device 6 for operating these ultrasonic transducers 10A and 10B to calculate a slip angle, a yaw rate sensor 3 (turning speed detection means) installed at the center of gravity of the vehicle body,
The display device 4 displays the measured slip angle.

The ultrasonic transducers 10A and 10B are shown in the figure.
As can be seen from 16, it corresponds to the rotation axis of the wheel 110.
Parallel to the Y-axis and separated from the traveling direction by a specified distance
Y _SA tie that indicates the rolling direction of the wheel 110 along the axis.
On the outside of the wheel 110, parallel to the X-axis corresponding to the center line
X separated by a predetermined distance_PPlaced equidistantly across the axis
Has been done. Then, the ultrasonic transducers 10A and 10B
Set the center of the vibration plane to the Y-axis and X_PProjection of intersection with axis to road surface
It is toward the point P corresponding to the point. In addition, each ultrasonic transducer
10A and 10B are installed at the same height from the road,
Depression angle θ_SAre also the same. So in this case
Is the transmission / reception axis a of each ultrasonic transducer 10A, 10B._A, A
_BProjection angle θ of the angle formed by each other on the road surface_d12'Is the first real
Example angle θ_d1'And θ_d2'Corresponds to_rS= Θ_SWhen
Become.

Also in this second embodiment, as in the first embodiment, the ultrasonic transducers 12 and 13 for reception are
The deviation angle Δθ _d1 ', Δθ corresponding to the assumed maximum vehicle speed
_{By selecting} the maximum value of _rS1 'and Δθ _d2 ' as the effective directivity half-angle, it is possible to receive the ultrasonic waves reflected from the road surface with a high gain even when the vehicle travels at the maximum vehicle speed. There is.

On the other hand, in the signal processing device 6, as can be seen from FIG. 15, a transmission / reception changeover switch (sound wave transmission means, sound wave reception means) 60, a transmission circuit (sound wave transmission means) 61, a reception circuit (sound wave reception means) 62. , Doppler shift frequency calculation circuit (Doppler shift frequency detection means) 63, storage circuit changeover switch (Doppler shift frequency detection means) 6
4, switching circuit (sound wave transmission means, sound wave reception means, Doppler shift frequency detection means) 65, first storage circuit (Doppler shift frequency detection means) 66a, second storage circuit (Doppler shift frequency detection means) 66b, slip angle calculation A circuit (slip angle calculating means) 67, a wheel speed detecting circuit (wheel speed detecting means) 68, and a correcting circuit (correcting means) 69.

The transmission / reception change-over switch 60 is for switching the reception sensor to either the ultrasonic transducers 10A or 10B and for selecting which sensor for transmitting / receiving the ultrasonic transducer 10A. Therefore, the ultrasonic transducer 10B and the receiving circuit 62 are connected and disconnected according to the switching signal CS _K1 from the switching circuit 65, and the ultrasonic transducer 10A is _switched on according to the switching signal CS _K2 from the switching circuit 65. It is connected to the transmission circuit 61 or the reception circuit 62.

The transmission circuit 61 outputs a voltage signal CS _S for oscillating an ultrasonic wave of a predetermined frequency f _S to the ultrasonic transducer 10A connected to the transmission circuit 61 via the transmission / reception changeover switch 60. At the same time, it outputs a signal corresponding to the transmission frequency f _S to the Doppler shift frequency calculation circuit 63, and has the same configuration as the transmission circuit 21 of the first embodiment.

The receiving circuit 62 receives the ultrasonic voltage signal CS _r received by the ultrasonic transducer 10A (or 10B) connected to the receiving circuit 62 via the transmission / reception changeover switch 60, and receives the ultrasonic voltage signal CS _r. The frequency f _r of the ultrasonic wave received by the ultrasonic transducer is calculated from the voltage signal CS _r ,
A signal corresponding to this frequency f _r is output to the Doppler shift frequency calculation circuit 63, and has the same configuration as the first and second receiving circuits 22 and 23 of the first embodiment.

The Doppler shift frequency calculation circuit 63
Calculates the Doppler shift frequency f _d corresponding to the deviation (f _r −f _S ) from the frequency f _r input from the receiving circuit 62 and the transmission frequency f _S input from the transmitting circuit 61. , A signal corresponding to this value is connected to the first memory circuit 6 via the memory circuit changeover switch 64.
6a or the second storage circuit 66b,
The configuration is similar to that of the first and second Doppler shift frequency calculation circuits 24 and 25 of the first embodiment.

The memory circuit change-over switch 64 sets one of the first memory circuit 66a and the second memory circuit 66b as the Doppler shift frequency calculating circuit 63 according to the changeover signal CS _K1 from the changeover circuit 65. To connect. The switching circuit 65 outputs the switching signal CS _K1 to the transmission / reception switching switch 60 and the storage circuit switching switch 64, and outputs the switching signal CS _K2 to the transmission / reception switching switch 60. And the like, so that the switching signal C is provided at each predetermined time.
It outputs S _K1 and C S _K2 . Then, in response to the switching signal CS _K1 , in the first connection state (that is, in the state in which the memory circuit switching switch 64 connects the Doppler shift frequency calculation circuit 63 and the first memory circuit 66a, the transmission / reception switching switch 60, The ultrasonic transducer 1 is first _sent by the switching signal CS _K2.
0A and the transmission circuit 61 are connected, the ultrasonic transducer 1
0A and the receiving circuit 62 are connected) and the second state shown in FIG. 15 (the ultrasonic transducer 10A and the transmitting circuit 61 are connected, the ultrasonic transducer 10B and the receiving circuit 62 are connected, and the Doppler Shift frequency calculation circuit 63 and second storage circuit 6
6b is connected) and the switch 6b can be switched at predetermined time intervals.

When the first memory circuit 66a is connected to the Doppler shift frequency calculation circuit 63 by the memory circuit changeover switch 64, the first Doppler shift frequency f _d output from the Doppler shift frequency calculation circuit 63 is set to the first Doppler shift frequency. The shift frequency f _d1 is updated and stored, and this value is output to the slip angle calculation circuit 67 and the wheel speed detection circuit 68 at a predetermined timing.

When the second memory circuit 66b is connected to the Doppler shift frequency calculation circuit 63 by the memory circuit changeover switch 64, the second Doppler shift frequency f _d output from the Doppler shift frequency calculation circuit 63 is set to the second Doppler shift frequency. The shift frequency f _d2 is updated and stored, and this value is output to the slip angle calculation circuit 67 at the same timing as the output of the first Doppler shift frequency f _d1 from the first storage circuit 66a.

The slip angle calculation circuit 67, the wheel speed detection circuit 68, and the correction circuit 69 are basically the same as the slip angle calculation circuit 26, the wheel speed detection circuit 27, and the correction circuit 68 of the first embodiment. Is similar, but has a configuration according to a calculation formula based on the sensor geometry. Here, in the first state by the switching signal CS _K1 , the ultrasonic transducer 10A first transmits ultrasonic waves as a transmission sensor, and then immediately receives reflected ultrasonic waves as a reception sensor by the switching signal CS _K2. The Doppler shift frequency f _d1 at that time is represented by the following equation (27).

[0108]

[Equation 17]

In the second state by the switching signal CS _K1 , the ultrasonic wave oscillator 10B receives the ultrasonic wave transmitted from the ultrasonic wave oscillator 10A and reflected on the road surface. At this time, the Doppler shift frequency f _d2 Is expressed by the following equation (28).

[0110]

(Equation 18)

Since the denominators of these expressions are equal,
Ratio of both Doppler shift frequencies f _d1 and f _d2 R _f '= (f _d1
/ F _d2 ), the relational expression between the Doppler shift frequencies f _d1 and f _d2 and the tire slip angle α _P at the point P, which does not include the sound velocity C _S , is obtained. The relational expression is
It is shown in the equation 9).

[0112]

[Formula 19]

By modifying this equation (29), the tire slip angle α _P is expressed by the following equation (30), and the proportional constant K ₃
= 1 / (tan (θ _{d12 '} / 2)) and finally (3
It is expressed by the equation 1).

[0114]

(Equation 20)

[0115]

[Equation 21]

Therefore, the slip angle calculation circuit 67
The proportional constant K is stored in the memory according to the sensor geometry.
₃ is stored, and the operation is performed based on the equation (31). With the configuration described above, in the slip angle measuring device of this embodiment, for example, when the tire slip angle measurement is started at the same time as the ignition is turned on, the transmission / reception changeover switch 60 by the changeover signals CS _K1 , CS _K2 from the changeover circuit 65. Operation of the ultrasonic transducer 1
The transmission of ultrasonic waves by 0A and the reception of reflected ultrasonic waves and the transmission of ultrasonic waves by the ultrasonic transducer 10A and the reception of reflected ultrasonic waves by the ultrasonic transducer 10B are alternately performed at predetermined timings. In addition, the first Doppler shift frequency f _d1 from the first storage circuit 66a to the slip angle calculation circuit 26 and the wheel speed detection circuit 27, the second Doppler shift frequency f _d2 from the second storage circuit 66b to the slip angle calculation circuit 26,
It is output at the same time every predetermined time.

Then, in the slip angle calculating circuit 26, the point P based on the above equation (30) is calculated from the two Doppler shift frequencies f _d1 and f _d2 inputted at the same time and the proportional constant K ₃ stored in advance. tire slip angle alpha _P is calculated, this value is outputted to the correction circuit 28 in,
In the wheel speed detection circuit 27 and the correction circuit 28, the same processing as in the first embodiment is performed, the calculated slip angle α at the tire ground contact point is output to the display device 4, and the tire slip angle α is displayed on the display device 4. The measured value of is displayed.

According to the slip angle measuring apparatus of the second embodiment, since the ultrasonic transducer 10A is used for both transmission and reception, the number of ultrasonic transducers is reduced by one compared with the first embodiment, and the receiving circuit and the Doppler are used. Since only one shift frequency calculation circuit 63 is required, not only cost reduction can be achieved, but also
There is also an advantage that problems such as electrical interference between channels and inconsistency of circuit characteristics can be avoided.

The slip angle measuring devices of the first and second embodiments measure the tire slip angle, and for transmitting ultrasonic waves to the road surface near each wheel to be measured, for example, As shown in FIG. 7, the ultrasonic sensor 1 is mounted between the wheel 110 and the vehicle body 100 via the mounting member 5, but a similar ultrasonic sensor 1 is mounted near the center of gravity CG of the vehicle body 100. And the center of gravity CG
The slip angle at the vehicle body weight center point can be measured by setting the center point P directly under the center of the measurement road surface. FIG. 17
(A) is the vehicle body 100 of the said ultrasonic sensor 1 in that case.
FIG. 17 is a plan view showing an example of a mounting position with respect to FIG.
(B) is the side view. In this case, the center of gravity CG
Since it is possible to make the center of the measurement road surface just below, it is necessary to provide the correction circuits 28 and 69 and the wheel speed detection circuits 27 and 68 in the signal processing devices 2 and 6 as in the first and second embodiments. Absent.

Further, the wheel speed detection circuit 2 of the first embodiment.
7, in the slip angle measured by the slip angle measuring device of the present invention, as can be seen from the formula (16) corresponding to the formula for calculating the wheel speed V _P (speed in the traveling direction of the wheel at the point P), Since it is possible to measure the speed in the traveling direction of the wheel or vehicle body weight center point at a predetermined point, the slip angle measuring device of the present invention measures the speed in the traveling direction of the wheel or vehicle body weight center point at such a predetermined point. It can also be used as a device for In this case, it is difficult to align the X-axis direction and the Y-axis direction when installing the ultrasonic sensor with the conventional speedometer utilizing the Doppler effect, while the slip angle measurement of the present invention is performed. Since the device eliminates such difficulty of axis alignment, the mounting workability is significantly improved.

The slip angle measuring device of the present invention is
By using a piezoelectric ultrasonic transducer, it is possible to provide a practical device that can detect the slip angle with high accuracy because it has excellent environmental resistance, is small and lightweight, and saves power.
Therefore, as shown in FIG.
The ultrasonic sensors 1FL to 1RR having ultrasonic transducers for transmission and reception are arranged inside the 110RR, and the reception signals CS from the ultrasonic sensors 1FL to 1RR are arranged.
_{Input rFL ~} CS _rRR to the control unit 20,
By outputting various control signals corresponding to the tire slip angles α _{FL to} α _RR of each wheel to the engine / powertrain unit 7, the steering actuator 8, and the like, various fine-tuned vehicle control can be performed. Further, in such an actual vehicle, as shown in FIG. 19 corresponding to the detailed view of the portion A of FIG. 18, unlike the case of FIG. 7 showing the mounting state of the first embodiment, inside the wheel 110RR is different. It is preferable to install the ultrasonic sensor 1RR via a dedicated bracket 10RR or the like.

In each of the above-described embodiments, the signal processing devices 2 and 6 have a circuit configuration by hardware, but the tire slip angle α at the point A is calculated from the calculation of the Doppler shift frequency other than the transmission / reception of ultrasonic waves. The part up to the calculation can be configured by a microcomputer. Also,
In each of the embodiments described above, only the case where the ultrasonic wave is used as the sound wave has been described, but it goes without saying that the sound wave that can be used in the slip angle measuring device of each invention of the present invention is not limited to the ultrasonic wave.

[0123]

As described above, according to the slip angle measuring device according to the first to third aspects, the two sound wave receiving means are arranged as described above with respect to the predetermined point where the transmission axis of the sound wave transmitting means is directed. By installing with a specific sensor geometry, the term of sonic velocity is excluded from the formula for calculating the slip angle using the Doppler shift frequency, so the slip angle can be accurately measured without being affected by the sonic velocity. is there.

Particularly, according to the slip angle measuring device of the second aspect, since the measurement error occurring in the device of the first aspect when measuring the tire slip angle is small, the tire slip angle can be accurately measured. it can. Particularly, according to the slip angle measuring device of the third aspect, it is possible to reliably and accurately measure the slip angle during high-speed traveling.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram of a slip angle measuring device of the present invention.

FIG. 2 is a perspective view showing an ultrasonic sensor that constitutes the slip angle measuring device of the first embodiment.

3 is a perspective view showing a mount constituting the ultrasonic sensor of FIG. 2. FIG.

4 is a cross-sectional view showing a portion of the mount of FIG. 3 from which an auxiliary plate is removed.

5 is a vertical sectional view showing a portion of the mount of FIG. 3 from which both end members are removed.

6 is a partial cross-sectional view showing how the ultrasonic sensor of FIG. 2 is attached to a vehicle.

FIG. 7 is a block diagram showing a schematic configuration of a slip angle measuring device of a first embodiment.

FIG. 8 is a perspective view showing a sensor geometry for transmitting and receiving ultrasonic waves in the first embodiment.

FIG. 9A is a plan view and FIG. 9B is a rear view showing sensor geometries of ultrasonic wave transmission and reception in the first embodiment.

10A is a plan view showing an arrangement of ultrasonic sensors with respect to a vehicle, and FIG. 10B is a schematic diagram showing a difference between velocity vectors at a point P and a point A on the rear left wheel side as an example. Is.

FIG. 11 is a graph showing an example of a relationship between a yaw rate and a measurement error caused when a tire slip angle measurement point is different from a tire ground contact point.

FIG. 12 (a) is a plan view showing a change in an ultrasonic wave propagation path as a vehicle travels, and FIG. 12 (b) is a side view thereof.

FIG. 13 is a plan view (a) and a side view (b) showing an example in which the sensor geometry for transmitting and receiving ultrasonic waves is different from that shown in FIGS. 8 and 9 for the device of the first embodiment.

FIG. 14 is a plan view (a) and a side view (b) showing an example different from that of FIG. 13 in which the sensor geometry for transmitting and receiving ultrasonic waves is different from that shown in FIGS. 8 and 9 for the device of the first embodiment. It is a figure.

FIG. 15 is a block diagram showing a schematic configuration of a slip angle measuring device of a second embodiment.

16 is a plan view showing a sensor geometry of transmission and reception of ultrasonic waves in the apparatus of FIG.

FIG. 17 is a plan view (a) showing an example of the mounting position of the ultrasonic sensor when measuring the slip angle of the body weight center of the vehicle;
It is a side view.

FIG. 18 is a schematic plan view showing an example of a vehicle control system in which the slip angle measuring device is assumed to be used in an actual vehicle.

19 is a cross-sectional view corresponding to a detailed view of a portion A in FIG.

FIG. 20 is a schematic configuration diagram showing a conventional example of a slip angle measuring device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ultrasonic sensor 3 yaw rate sensor (turning speed detection means) 11 ultrasonic transducer for transmission (sound wave transmission means) 12, 13 ultrasonic transducer for reception (sound wave reception means) 21 transmission circuit (sound wave transmission means) 22 First reception circuit (sound wave reception means) 23 Second reception circuit (sound wave reception means) 24 First Doppler shift frequency calculation circuit (Doppler shift frequency detection means) 25 Second Doppler shift frequency calculation circuit (Doppler shift frequency detection means) 26 , 67 Slip angle calculation circuit (slip angle calculation means) 27, 68 Wheel speed detection circuit (wheel speed detection means) 28, 69 Correction circuit (correction means) 10A Ultrasonic transducer (sound wave reception means, sound wave transmission means) 10B Ultra Sound wave transducer (sound wave receiving means) 60 Transmission / reception changeover switch (sound wave receiving means, sound wave transmitting means) 61 Transmission circuit (sound wave transmitting means) 62 reception circuit (sound wave reception means) 63 Doppler shift frequency calculation circuit (Doppler shift frequency detection means) 64 storage circuit changeover switch (Doppler shift frequency detection means) 65 changeover circuit (sound wave transmission means, sound wave reception means, Doppler shift frequency detection means) ) 66a 1st memory circuit (Doppler shift frequency detection means) 66b 2nd memory circuit (Doppler shift frequency detection means) 100 Vehicle body 110 Wheels

Front Page Continuation (72) Inventor Shuji Torii 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (3)

[Claims] 1. A sound wave transmitting unit that is installed at a predetermined position of a vehicle and sends a sound wave at a predetermined angle with a transmission axis directed to a predetermined point on a road surface on which the vehicle travels. Of the sound waves transmitted by the sound wave transmitting means and reflected at the predetermined points, two sound wave receiving means for receiving sound waves propagated at predetermined angles on both sides of the vertical plane including the predetermined point, and Doppler shift frequency detecting means for detecting the amount of frequency change from the time of transmission due to the Doppler effect of the sound wave received by the sound wave receiving means, and the amount of frequency change in each sound wave receiving means detected by the Doppler shift frequency detecting means. A slip angle measuring device utilizing the Doppler effect, comprising: a slip angle calculating means for calculating a slip angle of the vehicle based on the slip angle measuring device. 2. The slip angle is a tire slip angle, and is provided with a turning speed detecting means for detecting a turning speed of a vehicle body, and a wheel speed detecting means for detecting a speed of a wheel in a traveling direction at the predetermined point. The slip angle calculating means, based on the turning speed detection value from the turning speed detection means and the wheel speed detection value from the wheel speed detection means, the predetermined point and the ground contact point of the tire are different from each other. The slip angle measuring apparatus using the Doppler effect according to claim 1, further comprising a correction unit that corrects a deviation caused by the shift. 3. The Doppler effect according to claim 1, wherein the two sound wave receiving means are selected according to sensitivity directivity of sound waves to be used and a predetermined vehicle speed set in advance. Slip angle measuring device.