JPH04212086A - Apparatus for detecting ground speed of car body - Google Patents

Abstract

PURPOSE:To enhance the reliability of the title apparatus by outputting ground speed using the detection result of car speed based on a wheel utilizing system at the time of abnormality in the detection of car speed based on a Doppler system. CONSTITUTION:It is judged whether an ultrasonic sensor 48 detecting the ground speed of a car body in the before-and-behind direction thereof using ultrasonic Doppler effect is normal and, when the ultrasonic sensor 48 is normal, the Doppler speed Vd based on the output signal of the ultrasonic sensor 48 is outputted as a ground car speed Vt. When the ultrasonic sensor 48 is abnormal, estimated speed Ve is calculated on the basis of the output signals of wheel speed sensors 40-46 and outputted as the ground car speed Vt.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting the speed of a vehicle relative to the ground, which is the speed at which a vehicle travels relative to a road surface, and particularly to a technique for improving the reliability of the device.

0002

[Prior art] A device for detecting vehicle speed relative to the ground was developed in Japanese Patent Application Laid-open No. 6
As disclosed in Publication No. 1-14586, the system includes a transmitter that transmits radiation waves toward the road surface that the wheels come into contact with, and a receiver that receives reflected waves that are reflected by the radiation waves on the road surface. Usually, the vehicle is equipped with a Doppler type vehicle speed detection device that detects the vehicle speed based on the transmission frequency and the reception frequency of the reflected wave, and is configured to determine the vehicle speed as the vehicle speed relative to the ground. The ground vehicle speed detected in this manner is used, for example, in the following devices. These include anti-lock control devices that control the braking force of the wheels to prevent excessive wheel slip when the vehicle is braking, and traction control devices that control the driving force of the wheels to prevent excessive wheel slip when the vehicle accelerates. It is a device.

0003

SUMMARY OF THE INVENTION The above-mentioned Doppler type vehicle speed detection device does not always operate normally. However, the conventional ground vehicle speed detection device determines the detected vehicle speed as the ground vehicle speed regardless of whether the operating state of the Doppler type vehicle speed detection device is normal or abnormal. Therefore, a device that operates using the vehicle speed relative to the ground has a problem in that its operating state greatly changes depending on the accuracy of the vehicle speed relative to the ground, that is, the operating state of the Doppler type vehicle speed detection device.

An example of a case where the Doppler type vehicle body speed detection device cannot operate normally will be explained. For example, the transmitting section and the receiving section are arranged in the direction in which the Doppler-type vehicle speed detection device should detect the vehicle speed, that is, parallel to the longitudinal direction of the vehicle, aligned in the left-right direction of the vehicle, and facing diagonally to the road surface. Placed. Of the reflected waves that are emitted from the transmitter and reflected on the road surface, only those that travel toward the receiver are incident on the receiver. However, the radiated waves do not always reflect back toward the receiver with a sufficiently large intensity; for example, if the road surface is smoother than usual due to water on the road surface, the radiated waves may Because the light cannot be reflected, almost none of the light reaches the receiving section, and as a result, the reception strength at the receiving section is insufficient, and the Doppler-type vehicle speed detection device cannot accurately detect the vehicle speed.

[0005] Against the background of the above circumstances, the present invention is provided in a vehicle equipped with a wheel-based vehicle speed detection device for detecting vehicle speed from the rotational state of the wheels, and also provides a ground vehicle body including the Doppler type vehicle speed detection device. The speed detection device determines whether the operating state of the Doppler type vehicle speed detection device is good or bad, and if it is not good, the vehicle speed detected by the wheel-based vehicle speed detection device is used to determine the vehicle speed relative to the ground. This was done with the goal of solving a problem.

[0006]

[Means for Solving the Problems] The gist of the present invention is as shown in FIG.
A ground vehicle speed detection device that is installed in a vehicle equipped with
The Doppler type vehicle speed detection device 2 is in a normal state where it can normally detect the vehicle speed using the output signal from the receiver or a parameter that changes in relation to it, or is in an abnormal state where it cannot normally detect the vehicle speed. (b) When the detection state determining means 3 makes a normal determination, the detected vehicle speed by the Doppler type vehicle speed detection device 2 is determined as the ground vehicle speed of the vehicle, but when an abnormality is determined, the vehicle speed The vehicle speed determining means 4 determines the vehicle speed relative to the ground using the vehicle speed detected by the vehicle speed detecting device 1.

[0007] The wheel-based vehicle speed detection device 1 may, for example, be of a type that detects the rotation of a rotor that is close to the wheel and rotates integrally therewith, and detects the vehicle speed based on the detection result. The system detects the rotation of a rotor that is close to and rotates integrally with a rotating shaft (e.g., propeller shaft, output shaft of a transmission, etc.) that connects the wheels and wheels, and detects the vehicle speed based on the detection results. can do.

[0008]

[Operation] In the ground vehicle speed detection device configured as above, it is determined whether the Doppler type vehicle speed detection device 2 can operate normally, and if so, the Doppler type vehicle speed detection device 2 The detected vehicle speed is determined as the ground vehicle speed, but otherwise, the ground vehicle speed is determined using the vehicle speed detected by the wheel-based vehicle speed detection device 1.

[0009]

As described above, according to the present invention, when the Doppler type vehicle speed detection device cannot operate normally, the vehicle speed detected by the wheel-based vehicle speed detection device is used to determine the vehicle speed relative to the ground. Therefore, the reliability of the ground vehicle speed detection device is improved, and the reliability of the device that operates using the ground vehicle speed is also improved.

0010

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 2 shows an anti-lock brake system including a ground vehicle speed detection device, which is an embodiment of the present invention. In this system, the brake pressure of the brakes 14 and 16, which suppress the rotation of the left and right front wheels 10 and 12, respectively, is applied to the actuators 18 and 20, and the brake pressure of the brakes 26 and 28, which suppress the rotation of the left and right rear wheels 22 and 24, respectively, is applied to the actuators. 30 and 32, respectively. Further, the wheel speeds of the respective wheels 10, 12, 22, 24 are detected by wheel speed sensors 40, 42, 44, 46, respectively. Each wheel speed sensor 40, 42, 44, 4
Reference numeral 6 detects the rotation of a rotor (not shown) that is close to each wheel 10, 12, 22, 24 and rotates integrally therewith, and outputs a signal corresponding to the rotation.

[0011] This system calculates the vehicle body speed in the longitudinal direction of the vehicle (this corresponds to the vehicle body speed in the present invention).
The ultrasonic sensor 48 includes an ultrasonic sensor 48 for detecting the speed of the vehicle, and an ultrasonic sensor 50 for detecting the vehicle speed in the left-right direction of the vehicle. Each of the ultrasonic sensors 48 and 50 includes a transmitting section 52 that transmits an ultrasonic wave as a radiation wave, and a receiving section 54 that receives an ultrasonic wave as a reflected wave. Both are attached to the bottom of the vehicle body near the center of gravity of the vehicle. Regarding the ultrasonic sensor 48, as shown in FIGS. 3 and 4,
The transmitting section 52 and the receiving section 54 are installed facing forward and diagonally facing the road surface at a constant angle φ, whereas the ultrasonic sensor 50 is installed with the transmitting section 52 and receiving section 54 facing right and facing the road surface at a constant angle φ. They are installed diagonally opposite each other at an angle φ. Therefore, when ultrasonic waves are transmitted toward the road surface from each transmitting section 52, among the reflected waves of the transmitted waves reflected from the road surface, those that travel in a direction almost opposite to the transmission direction of the transmitted waves are transmitted to each receiving section. 54.

The wheel speed sensors 40, 42,
44, 46, actuator 18, 20, 30, 32,
The transmitting section 52 and receiving section 54 of the ultrasonic sensor 48 and the transmitting section 52 and receiving section 54 of the ultrasonic sensor 50 are connected to the controller 60. This controller 6
As shown in FIG. 5, 0 is mainly a computer in which a CPU 62, a ROM 64, and a RAM 66 are connected to each other by a bus 68, and the wheel speed sensor 40 is connected to the bus 68 via a control circuit (not shown). etc. are connected.

The ROM 64 contains a Vd calculation and abnormality determination routine shown in the flowchart of FIG. 6, a Ve, Vt, θs calculation routine shown in the flowchart of FIG. 7, and a wheel speed calculation routine and an anti-lock control routine (not shown). is remembered.

The Vd calculation and abnormality determination routine uses the ultrasonic sensor 48 to calculate the vehicle body speed in the longitudinal direction of the vehicle (hereinafter simply referred to as Doppler speed Vd) based on the Doppler effect, and also calculates the speed based on the change in the Doppler speed Vd. This is to determine whether or not vehicle speed detection using the Doppler method is abnormal.

The Ve, Vt, θs calculation routine is (a
) Calculating the longitudinal vehicle body speed (hereinafter simply referred to as estimated speed Ve) estimated from the wheel speeds detected by the wheel speed sensors 40, 42, 44, and 46, and (b) V
d The true ground vehicle speed in the longitudinal direction (hereinafter, true speed Vt) based on the execution results of the calculation and abnormality determination routine.
That's what it means. However, this is only a calculated true speed and does not necessarily match the actual vehicle speed over the ground. It calculates the vehicle body speed in the left and right direction, and calculates the vehicle slip angle θs based on this and the above-mentioned Doppler speed Vd.

The wheel speed calculation routine calculates the wheel speed of each wheel 10, 12, 22, 24 based on the output signal from each wheel speed sensor 40, 42, 44, 46.

The anti-lock control routine calculates the slip rate of each wheel 10, 12, 22, 24 based on the true speed Vt and the wheel speed of each wheel 10, 12, 22, 24, and calculates the slip rate of each wheel 10, 12, 22, 24. Based on each wheel 10, 12,
22, 24, and if so, the true speed Vt and each wheel 10, 12, 22,
24 wheel speeds, each wheel 10 when braking the vehicle.
, 12, 22, 24 are controlled so that the slip ratios of the actuators 18, 20, 30, 32 are maintained within appropriate ranges. Furthermore, the anti-lock control routine controls each actuator 1 based on the vehicle slip angle θs.
8, 20, 30, and 32 are also controlled.

In the anti-lock brake system configured as described above, when the power of the vehicle is turned on, ultrasonic waves having a constant transmission frequency ft are transmitted from the transmitting section 52 of each ultrasonic sensor 48, 50. Along with being
The CPU 62 performs the Vd calculation, abnormality determination routine and Ve
, Vt, θs calculation routine, wheel speed calculation routine, and anti-lock control routine, respectively.

When executing the Vd calculation and abnormality determination routine, first, in step S1 in FIG. Then, the receiving section 5
The reception frequency fr of the ultrasonic wave received by No. 4 is measured, and then, in S2, the Doppler velocity Vd is calculated using the Doppler effect of the ultrasound based on the reception frequency fr and the transmission frequency ft. The calculated Doppler velocity Vd is stored in the RAM 66.

Subsequently, in S3, the difference between the maximum value and the minimum value among the plurality of Doppler velocities Vd calculated during a certain period of time (for example, 100 ms) is determined as the maximum velocity difference Δ.
Then, in S4, the maximum speed difference ΔVmax is calculated as the threshold value α (for example, 2km
/h). For example, because there is water on the road surface, the transmitted wave from the transmitting section 52 is hardly reflected properly on the road surface (reflection that causes a reflected wave toward the receiving section 54), so the receiving section 54 receives the reflected wave. When the intensity is insufficient, the receiving frequency fr fluctuates greatly, which in turn causes the Doppler velocity Vd to fluctuate greatly. In this step, based on such a phenomenon, it is determined that the operating state of the ultrasonic sensor 48 is abnormal if the maximum speed difference ΔVmax exceeds the threshold value α, and otherwise it is determined that the operating state is normal. That is, in this embodiment, the maximum speed difference ΔVmax
This is one aspect of the "parameter that changes in relation to the output signal from the receiving section" in the present invention. Note that the determination regarding the operating state of the ultrasonic sensor 48 in this embodiment is as follows, assuming that there is no abnormality in the ultrasonic sensor 48 itself.
This functions as a determination as to whether or not the road surface is suitable for detection by the ultrasonic sensor 48, that is, as a road surface suitability determination.

If the determination result in S4 is NO because the maximum speed difference ΔVmax is not larger than the threshold value α, S5
In S6, the value of the counter provided in the RAM 66 is set to 0, and subsequently, in S6, the abnormality flag provided in the RAM 66 is reset to 0. The abnormality flag indicates that the operating state of the ultrasonic sensor 48 is normal when it is reset to 0, and indicates that the ultrasonic sensor 48 is abnormal when it is set to 1. . This completes one execution of this routine.

On the other hand, if the determination result in S4 is YES because the maximum speed difference ΔVmax is larger than the threshold α, the value of the counter is increased by 1 in S7, and then the value of the counter is increased in S8. It is determined whether the current value is greater than the threshold value β. For example, the threshold value β is selected to be the number of times this routine is repeated during one second. In this example, the maximum speed difference Δ
Even if Vmax exceeds the threshold α, a final determination that the operating state of the ultrasonic sensor 48 is abnormal is not made immediately;
The final judgment that the operating state of the ultrasonic sensor 48 is abnormal is made only when the maximum speed difference ΔVmax exceeds the threshold α for a certain period of time (time corresponding to the magnitude of the threshold β). It is supposed to be done. Therefore, if it is assumed that the value of the counter is not larger than the threshold value β this time, the determination result in S8 becomes NO, and one execution of this routine ends. This time, the operating state of the ultrasonic sensor 48 is not determined to be abnormal, so the abnormality flag remains reset. On the other hand, if it is assumed that the value of the counter is larger than the threshold value β this time, the determination result in S8 becomes YES, and the abnormality flag is set to 1 in S9. This time, since the value of the counter exceeds the threshold value β, it is determined that the operating state of the ultrasonic sensor 48 is abnormal, and the abnormality flag is set. Thereafter, in S10, the current value of the counter is set to the threshold value β. This completes one execution of this routine.

When the Ve, Vt, θs calculation routine is executed, first, in S101 of FIG. 7, it is determined whether the abnormality flag is set to 1 or not. Assuming that is not the case this time, the result of the determination will be NO, and S1
At 02, the Doppler velocity Vd is read from the RAM 66 and stored in the RAM 66 as the true velocity Vt. Thereafter, in S103, the vehicle speed in the left and right direction is calculated using the ultrasonic sensor 50 according to S1 and S2, and the vehicle slip angle θs is calculated based on this and the true speed Vt. The calculated vehicle slip angle θs is stored in the RAM 66. This completes one execution of this routine.

On the other hand, if the abnormality flag is set to 1, the determination result in S101 becomes YES, and in S104, the four wheels 10, 12, 22, 2
After the four wheel speeds are read out from the RAM 66, the estimated speed Ve is calculated based on these wheel speeds. Specifically, when the vehicle is not braking, the left and right front wheels 1, which are idle wheels,
It is estimated that the average value of the two wheel speeds 0 and 12 represents the estimated speed Ve, while when braking the vehicle, the average value of the two wheel speeds 1
It is estimated that the wheel speed of the fastest wheel with the maximum wheel speed among 0, 12, 22, and 24 represents the estimated speed Ve, and after the deceleration of the fastest wheel exceeds a preset upper limit, Estimated speed Ve with the speed fixed at its upper limit
is calculated. The calculated estimated speed Ve is R
Stored in AM66. Thereafter, in S105, the estimated speed Ve is read out from the RAM 66 and stored in the RAM 66 as the true speed Vt. Subsequently, in S106, the vehicle slip angle θs is set to zero. This time, the operating state of the ultrasonic sensor 48 is abnormal and the vehicle slip angle θs cannot be detected accurately, so even if the vehicle slip angle θs is not actually 0,
It is considered that

At each execution of the anti-lock control routine, the true speed Vt and vehicle slip angle θs are read out from the RAM 66, and anti-lock control is performed based on these true speed Vt and vehicle slip angle θs.

Therefore, in this embodiment, when the operating state of the ultrasonic sensor 48 is abnormal (more precisely, when the output signal of the ultrasonic sensor 48 is abnormal), the estimated speed Ve remains the true speed. Since the anti-lock control is carried out by being diverted as Vt, even if the ultrasonic sensor 48 operates abnormally, the control accuracy of the anti-lock control does not deteriorate significantly.

As is clear from the above description, in this embodiment, the part of the computer that executes S104 in FIG. The part of the computer that executes S1 and S2 in FIG. The portion of the computer that constitutes the detection state determining means 3 and executes S101, S102, and S105 in FIG. 7 constitutes the ground vehicle speed determining means 4.

In the above embodiment, when it is determined that the operating state of the ultrasonic sensor 48 is abnormal,
The vehicle slip angle θs was set to 0, but this was done based on the prediction that if the operating state of the ultrasonic sensor 48 was abnormal, the operating state of the ultrasonic sensor 50 would also be abnormal. That's how it was done. However, it goes without saying that the operating state of the ultrasonic sensor 50 may also be determined; in this case, for example, (a) it is determined that the operating states of the ultrasonic sensors 48 and 50 are both normal; For example, Doppler velocity Vd and ultrasonic sensor 50
The vehicle slip angle θs is calculated based on the left-right vehicle body speed calculated using If it is judged that If it is determined that the vehicle slip angle θs is 0, the vehicle slip angle θs may be set to 0.

Furthermore, in the embodiment described above, it is determined that the operating state of the ultrasonic sensor 48 is abnormal only when the maximum velocity difference ΔVmax exceeds the threshold value α for a certain period of time. However, other forms of abnormality determination may be adopted. For example, a format in which it is determined whether the current value of the Doppler velocity Vd has changed by more than a certain value from the previous value, and if so, it is determined that the operating state is abnormal, or a format in which a plurality of consecutive Doppler velocities Vd are determined. It is possible to adopt a format in which the value of σ or 3σ (σ: standard deviation) is calculated and it is determined whether the result exceeds the threshold value γ, and if so, the operating state is determined to be abnormal. be.

Furthermore, in the embodiment, as soon as it is determined that the operating state of the ultrasonic sensor 48 is abnormal,
The estimated velocity Ve was used to be used as is as the true velocity Vt, but in this case, the current true velocity Vt, that is, the estimated velocity Ve, becomes slightly suddenly different from the previous true velocity Vt, that is, the Doppler velocity Vd. Changing circumstances may arise. If it is necessary to avoid such a situation, for example, it is determined whether the current estimated speed Ve has changed by a certain amount or more from the previous true speed Vt, and if not, the estimated speed Ve is used as is as the true velocity Vt, but if so, a specific value (for example, the average value of the estimated velocity Ve and the latest normal Doppler velocity Vd) may be used. In this way, a sudden change in the true speed Vt is prevented and anti-lock control is performed in accordance with reality.

Furthermore, in the embodiment described above, while the operating state of the ultrasonic sensor 48 is determined to be abnormal,
The estimated velocity Ve was used to be used as is as the true velocity Vt, but the true velocity Vt immediately before the abnormality determination, that is, the latest normal Doppler velocity Vd
and the subsequent estimated speed Ve to determine the true speed Vt
may be determined. For example, for the period from the first estimated speed Ve to the current estimated speed Ve during the abnormality determination period, the cumulative result of the amount of change in the estimated speed Ve per a certain short time (time differential value of the estimated speed Ve) is compared to the normal latest The true velocity Vt may be determined by adding it to the Doppler velocity Vd of .

FIG. 8 shows another embodiment of the present invention. In addition,
Elements common to those in the previous embodiment will be designated by the same reference numerals and a description thereof will be omitted.

In this embodiment, as shown in FIG.
An ultrasonic sensor 48 including a transmitting section 52 and a receiving section 54 is attached to the front end of the bottom surface of the vehicle body at a position intersecting a front-rear center line passing through the center of gravity. The transmitting section 52 and the receiving section 54 are both arranged so as to face forward and face the road surface diagonally at a constant angle φ. Further, as shown in FIG. 9, a warning light 80 is connected to the bus 68 of the controller 60 and is turned on to warn the driver that the operating state of the ultrasonic sensor 48 is abnormal. As shown in the figure, the ROM 64 of the controller 60 stores the same wheel speed calculation routine as in the previous embodiment, an estimated speed calculation routine, a Doppler speed calculation routine, a sensor abnormality determination routine, and an anti-lock control routine. Initially, various programs are stored. The estimated speed calculation routine is a program that calculates the estimated speed Ve in the same manner as in the previous embodiment. The Doppler velocity calculation routine is a program that calculates the Doppler velocity Vd from the output signal from the receiving section 54 of the ultrasonic sensor 48. As shown in the flowchart of FIG. 10, the sensor abnormality determination routine determines whether the operating state of the ultrasonic sensor 48 is abnormal, and uses the wheel speed sensors 40 to 46 according to the determination result. Estimated speed Ve calculated by
This program calculates the true velocity Vt from the Doppler velocity Vd calculated using the ultrasonic sensor 48. The anti-lock control routine operates each actuator 18, 2 so as to generate as large a braking force as possible on each wheel 10, 12, 22, 24 while referring to the true speed Vt.
This is a program that controls 0, 30, and 32. The details of the sensor abnormality determination routine will be explained later.

On the other hand, the RAM 66 of the controller 60, as shown in FIG.
Estimated velocity memory 84 for storing Doppler velocity Vd
Doppler velocity memory 86 that stores true velocity Vt
A true speed memory 88 for storing the time t, a time memory 90 for storing the time t, an abnormality flag, and a characteristic change flag to be described later are provided.

The sensor abnormality determination in the sensor abnormality determination routine will be described. For this sensor abnormality determination, the output signal of the ultrasonic sensor 48 alone is used to determine whether the ultrasonic sensor 4
8 is abnormal or not, and relative abnormality determination is determined based on the relative relationship between the Doppler velocity Vd based on the output signal of the ultrasonic sensor 48 and other parameters. There is. Absolute abnormality determination is based on the output signal from the receiving section 54 of the ultrasonic sensor 48 (this is one aspect of the "output signal from the receiving section" in the present invention).
It is determined whether the level of has fallen below the threshold value δ, and if so, it is determined that the operating state of the ultrasonic sensor 48 is abnormal. On the other hand, the relative abnormality determination is based on whether the Doppler vehicle speed Vd (this is an aspect of the "parameter that changes in relation to the output signal from the receiver" in the present invention) satisfies Conditions 1 to 4, respectively. If the condition is satisfied, it is determined that the operating state of the ultrasonic sensor 48 is abnormal. Each condition 1 to 4 will be explained in detail below.

When the vehicle is not braking, the estimated speed calculation routine calculates the estimated speed Ve using the left and right front wheels 10 and 12, which are idle wheels, as described above. At this time, left and right front wheels 10
, 12 is approximately 0, so if the ultrasonic sensor 48 is normal, the estimated speed Ve and the Doppler speed Vd should almost match. Therefore, if the Doppler velocity Vd deviates from the estimated velocity Ve by more than the threshold value ε (for example, 2 km/h), the ultrasonic sensor 4
8 is determined to be abnormal. In short, Doppler velocity V
Condition 1 is satisfied if d deviates from the estimated speed Ve by more than the threshold value ε. However, even if the Doppler velocity Vd deviates from the estimated velocity Ve by more than the threshold value ε, it is not immediately determined that the ultrasonic sensor 48 is abnormal, but if this continues for more than the maximum time tmax (for example, 10 seconds) It is determined for the first time that the ultrasonic sensor 48 is abnormal. If the ultrasonic sensor 48 itself is abnormal, the situation in which the Doppler velocity Vd deviates from the estimated velocity Ve by more than the threshold value ε continues for a long time, whereas the ultrasonic sensor 48 itself is normal, but The output signal of the ultrasonic sensor 48 may become temporarily abnormal due to a temporary deterioration of the reflection condition on the ultrasonic sensor 4. In this case, if the road surface changes, the reflection condition improves and the ultrasonic sensor 4
This is because the output signal of No. 8 may recover to a normal state.

On the other hand, when the vehicle is braked, the estimated speed calculation routine applies all the wheels 10, 12, 22 as described above.
, 24 is used to calculate the estimated speed Ve. At this time, the slip rate of the fastest wheel is greater than 0. Therefore, when the vehicle is braked, regardless of whether anti-lock control is being performed or not, if the ultrasonic sensor 48 is normal, the Doppler speed Vd should be larger than the estimated speed Ve. Therefore, in this embodiment, as shown in FIG. 11, for example, the Doppler velocity Vd is smaller than the estimated velocity Ve, and the difference is a threshold value
), it is determined that the ultrasonic sensor 48 is abnormal. In short, the Doppler velocity Vd is the estimated velocity Ve
Condition 2 is satisfied if the difference is smaller than the threshold value ζ and the difference is larger than the threshold value ζ.

When braking the vehicle, both the Doppler velocity Vd and the estimated velocity Ve may become 0, but this can occur either when the vehicle comes to a complete stop with the ultrasonic sensor 48 operating normally, or when the ultrasonic sensor 48 is malfunctioning. It is conceivable that all the wheels 10, 12, 22, and 24 shift to a completely locked state at the same time that the Doppler velocity Vd decreases. In the latter case, since each wheel speed and the Doppler speed Vd decrease together, it is not possible to shift to anti-lock control, and all wheels 10, 12, 22, 24 will shift to a completely locked state. be. Therefore, in this embodiment, as shown in FIG. 12, when both the Doppler speed Vd and the estimated speed Ve are 0, only the brake pressure of the left and right rear wheels 22, 24 is applied for a certain period of time T0 (for example, 10 ms). If the estimated speed Ve becomes larger than the Doppler speed Vd, it is determined that the ultrasonic sensor 48 is abnormal. Note that the broken line shown in the figure does not indicate the actual ground vehicle speed, but the original ground vehicle speed (the ground vehicle speed when the ultrasonic sensor 48 is normal). In short, if both the Doppler speed Vd and the estimated speed Ve are 0, and if the brake pressure of the left and right rear wheels 22, 24 is then reduced for a certain period of time T0, then the estimated speed Ve will be greater than the Doppler speed Vd, which satisfies condition 3. It is about fulfilling it.

Assuming that an abnormality occurs in the ultrasonic sensor 48 during anti-lock control and the Doppler velocity Vd becomes greater than the actual ground vehicle speed, each wheel 10, 12, 2
The calculated slip ratio SLc of 2.2 and 24 becomes larger than the actual slip ratio SLa. Also, during anti-lock control, the calculated slip ratio SLc is controlled so as to approach the target slip ratio SLd (for example, 15%),
In the end, the actual slip rate SLa is the target slip rate S
It is controlled to approach a value smaller than Ld. When the actual ground vehicle speed is estimated from the estimated speed Ve, that is, the wheel speed of the fastest wheel among all wheels 10, 12, 22, 24, the actual slip rate SLa of the fastest wheel is 0 and the target slip rate SLd. The actual ground speed is between the wheel speed of the fastest wheel and (
1-SLd). That is, if the Doppler velocity Vd is larger than the product of the estimated velocity Ve and the reciprocal of (1-SLd), it can be estimated that the ultrasonic sensor 48 may be abnormal. However, even if the ultrasonic sensor 48 is normal, the calculated slip rate SLc of the fastest wheel temporarily becomes larger than the target slip rate SLd, and as a result, the Doppler speed Vd becomes the estimated speed Ve and (1-SLd ) may be larger than the product of the reciprocal of For these reasons, in this embodiment, as shown in FIG. 13, for example, the Doppler velocity Vd is equal to the estimated velocity Ve and (1-SLd)
The brake pressure of the fastest wheel used to estimate the estimated speed Ve remains greater than the product of the reciprocal of
If the pressure continues to be reduced for more than 1 second), it is determined that the ultrasonic sensor 48 is abnormal. If the Doppler speed Ve is larger than the actual ground vehicle speed, each wheel 10, 12, 2
The calculated slip ratio SLc of wheels 2 and 24 is larger than the actual slip ratio SLa, and even if the brake pressure continues to be reduced, the calculated slip ratio S of each wheel 10, 12, 22, 24
This is because Lc does not decrease to the target slip ratio SLd. Note that the broken line shown in the same figure indicates the original vehicle speed relative to the ground, not the actual vehicle speed relative to the ground. in short,
Doppler velocity Vd is estimated velocity Ve and (1-SLd
Condition 4 is satisfied if the brake pressure of the fastest wheel continues to decrease for a certain period of time T1 or more while remaining greater than the product of the reciprocal of ).

Next, the manner in which the sensor abnormality determination routine is executed will be explained in detail with reference to FIG. First, S
At 201, it is determined whether the brake pedal has been depressed. Assuming that the vehicle is currently not braking, the result of the determination is NO, and in S202 it is determined whether the abnormality flag is set to 1 or not. Since the abnormality flag is reset to 0 when the controller 60 is powered on, the abnormality flag is currently reset to 0. Therefore, the result of the determination is NO, and the absolute abnormality determination is performed in S203. Assuming that it is determined that the ultrasonic sensor 48 is not abnormal in this absolute abnormality determination, the determination result becomes NO, and in S204, it is determined whether or not the above-mentioned condition 1 is satisfied, that is, the Doppler velocity Vd
It is determined whether or not the estimated speed Ve deviates from the estimated speed Ve by a threshold value ε or more. Assuming that condition 1 is not currently satisfied, the determination result is NO, and in S205, 0 is stored in the time memory 90 as time t, and in S6, the Doppler velocity Vd is read from the Doppler velocity memory 86, and this is It is stored in the true speed memory 88 as the true speed Vt. This time, it is determined that the ultrasonic sensor 48 is not abnormal, so the Doppler velocity Vd is determined to be the true velocity Vt. This completes one execution of this routine.

On the other hand, assuming that condition 1 is satisfied, the determination result in S204 becomes YES, and in S207, the time t of the time memory 90 is increased by a constant minute time Δt, and then, in S208, the time It is determined whether the current value of t exceeds the scheduled maximum time tmax. If it is determined that condition 1 is satisfied during a certain execution of S204, but it is determined that condition 1 is not satisfied during subsequent execution of S204, time t is returned to 0 in S205. Therefore, S201 to 204, 207
, 208 and 206 are repeated many times, and as a result, in S208, the current value of time t becomes the maximum time tma
It is determined that x has exceeded the maximum time t of condition 1.
This means that the condition continues to be satisfied at least max, and only then is it determined that the ultrasonic sensor 48 is abnormal. Subsequently, in S209, the abnormality flag is set to 1, and in S210, the warning light 80 is turned on to display to the driver that the ultrasonic sensor 48 is abnormal. Subsequently, in S211, the estimated speed Ve is read from the estimated speed memory 84 and stored in the true speed memory 88 as the true speed Vt. Since it is determined that the ultrasonic sensor 48 is abnormal this time, the estimated velocity Ve is set as the true velocity Vt instead of the Doppler velocity Vd. This completes one execution of this routine.

If it is assumed that the ultrasonic sensor 48 is determined to be abnormal in the absolute abnormality determination in S203, the steps after S209 are immediately executed. Further, after the abnormality flag is set to 1 in S209, if it is determined in S202 whether or not the abnormality flag is set to 1, the determination result is YE.
S, and the steps after S210 are executed immediately.

[0043] Above, the non-braking state has been explained, but next, the braking state will be explained. In this case, if it is determined in S201 whether or not the brake pedal has been depressed, the result of the determination becomes YES, and in S211a it is determined whether or not the abnormality flag is set to 1. Assuming that it is set to 1, the result of the determination is YE.
S, and in S212, when it is reset to 0, it indicates that the control characteristic of the anti-lock control is the normal characteristic, while when it is set to 1, it indicates that the control characteristic is on the pressure reduction side from the normal characteristic. The characteristic change flag shown is set to 1. Characteristic change flag is controller 60
It is reset to 0 when the power is turned on.

When this step is executed, the estimated velocity Ve is the true velocity Vt instead of the Doppler velocity Vd.
It is said that The estimated speed Ve is the actual ground vehicle speed, that is, the Doppler speed V when the ultrasonic sensor 48 is normal.
d (hereinafter simply referred to as normal Doppler velocity Vd), the estimated velocity Ve is higher than the true velocity Vt.
, the calculated slip ratio SLc of each wheel 10, 12, 22, 24 becomes smaller than when the normal Doppler velocity Vd is taken as the true velocity Vt, and as a result, anti-locking is performed while referring to the estimated velocity Ve. When performing the control, the brake pressure of each wheel 10, 12, 22, 24 is controlled to the pressure increasing side compared to when anti-lock control is performed while referring to the normal Doppler speed Vd. Therefore, when the estimated speed Ve is set to the true speed Vt, anti-lock control is performed with a characteristic on the pressure reduction side rather than a normal characteristic. After that, in S213, S2
An abnormality display is performed in the same manner as in S214.
In S215, the estimated speed Ve in the estimated speed memory 84 is stored as the true speed Vt in the true speed memory 88, and then in S215 it is determined whether the current depression of the brake pedal continues. If so, S2
Return to 13. That is, once it is determined that the ultrasonic sensor 48 is abnormal while the brake pedal is depressed a certain time, the ultrasonic sensor 48 is unconditionally determined to be abnormal until the brake pedal is depressed that time. It has become.

If the current depression of the brake pedal is released and the determination result in S215 becomes NO, the abnormality flag and characteristic change flag are each reset to 0 in S216, and then the current value of time t is reset to 0 in S217. will be reinstated. This completes one execution of this routine.

On the other hand, if S211a is executed with the abnormality flag reset to 0, the result of the determination is NO, and in S218 it is determined whether the current value of time t is greater than 0 or not. That is, it is determined whether or not the continuation time does not exceed the maximum time tmax even though it is determined that condition 1 is satisfied. If it is assumed that it is greater than 0, the result of the determination will be YES, and the steps after S212 will be executed. That is, if it is determined that condition 1 is satisfied but the duration does not exceed the maximum time tmax, as described above, the ultrasonic sensor 48 itself is abnormal and the ultrasonic sensor 48 itself is normal. This is thought to be caused by a temporary deterioration in the reflection state of ultrasonic waves on the road surface, and since it is not possible to determine which of these is the true cause, the abnormality flag is set to 1 in S209.
Even if the ultrasonic sensor 48 is not set, it is determined that the ultrasonic sensor 48 is abnormal.

If both the determination result of S211a and the determination result of S218 are NO, the condition 2 is satisfied in S219.
It is determined whether the Doppler velocity Vd is smaller than the estimated velocity Ve and the difference is larger than the threshold value ζ. If it is assumed that condition 2 is satisfied, the result of the determination is YES, and the steps after S212 are executed, but if it is assumed that it is not satisfied, the result of the determination is NO, and in S220, it is determined whether the condition 3 is satisfied or not. , that is, the Doppler velocity Vd is also the estimated velocity Ve
is 0, and if the brake pressure of the left and right rear wheels 22, 24 is then reduced for a certain period of time T0, the estimated speed Ve
It is determined whether or not the velocity has become larger than the Doppler velocity Vd. Assuming that condition 3 is satisfied, the judgment result is YES.
Therefore, in S221, only the brake pressure of the left and right rear wheels 22, 24 is reduced for a certain period of time T2. This time, the estimated speed Ve is set to the true speed Vt, so that the wheel speeds of the left and right rear wheels 22, 24 are restored to the actual ground vehicle speed as much as possible. After that, the steps after S212 are executed. On the other hand, if it is assumed that condition 3 is not satisfied, the determination result in S220 is NO, and S2
At step 22, it is determined whether anti-lock control is currently being performed. If we assume that this is not the case, the result of the judgment is N
O, and an absolute abnormality determination is made in S223.
If it is determined that the ultrasonic sensor 48 is not abnormal, the determination result becomes NO and the process moves to S206. On the other hand, if it is determined that the ultrasonic sensor 48 is abnormal in S223, the determination result becomes NO. The answer is YES, and the steps after S212 are executed.

Assuming that anti-lock control is currently being performed, the determination result in S222 is YES, and an absolute abnormality determination is made in S224, and if it is determined that the ultrasonic sensor 48 is abnormal, Judgment result is YES
S, and after the brake pressures of the left and right rear wheels 22, 24 are reduced for a certain period of time T2 in S221, the steps after S212 are executed. All wheels 10, 12, 22,
24, anti-lock control is performed, and the actual slip rate SLa of each wheel 10, 12, 22, 24
is not 0 and is close to the target slip ratio SLd, so the actual slip ratio SLa of the left and right rear wheels 22, 24 is brought close to 0 to make the true speed Vt match the actual ground vehicle speed as much as possible.

On the other hand, if it is determined in S224 that the ultrasonic sensor 48 is not abnormal, the result of the determination becomes NO, and in S225 it is determined whether the above-mentioned condition 4 is satisfied, that is, the Doppler velocity Vd is Estimated speed Ve
It is determined whether the brake pressure of the fastest wheel used for estimating the estimated speed Ve has continued to decrease for a certain period of time T1 or more while remaining smaller than the product of the reciprocal of (1-SLd) and (1-SLd). If it is assumed that condition 4 is satisfied, the result of the determination is YES and the steps after S212 are executed, but if it is assumed that condition 4 is not satisfied, the result of the determination is NO and the process moves to S206.

In the several embodiments detailed above, the left and right front wheels 10, 12 are idle wheels, the left and right rear wheels 22,
24 is a ground vehicle speed detection device suitable for a rear wheel drive vehicle, but the present invention can also be applied to a ground vehicle speed detection device for a front wheel drive vehicle or a four wheel drive vehicle. can be applied. Note that when the present invention is applied to a ground vehicle speed detection device for a four-wheel drive vehicle, since the actual slip ratio SLa of each wheel 10, 12, 22, 24 is slightly larger than 0 even when the vehicle is not braking, The determination of whether Condition 1 is satisfied, that is, the determination of whether the Doppler speed Vd deviates from the estimated speed Ve by more than the threshold value ε, is made when the vehicle is not braking and the engine throttle valve is in the most closed position. It is desirable to do this at times.

Several embodiments of the present invention have been described above in detail with reference to the drawings, but the present invention can be carried out in various modifications and improvements based on the knowledge of those skilled in the art. can do.

[Brief explanation of the drawing]

FIG. 1 is a block diagram conceptually showing the configuration of the present invention.

FIG. 2 is a system diagram of an anti-lock brake system including a ground vehicle speed detection device according to an embodiment of the present invention.

3 is a side view showing an enlarged view of the ultrasonic sensor 48 in FIG. 2. FIG.

4 is an enlarged front view showing the ultrasonic sensor 48 in FIG. 2. FIG.

FIG. 5 is a block diagram showing an electrical system of the anti-lock brake system.

FIG. 6 is a flowchart showing selected programs that are closely related to the present invention from among the programs stored in the ROM of the computer in FIG. 5;

FIG. 7 is a flowchart showing selected programs that are closely related to the present invention from among the programs stored in the ROM of the computer in FIG. 5;

FIG. 8 is a system diagram of an anti-lock brake system including a ground vehicle speed detection device according to another embodiment.

FIG. 9 is a block diagram showing an electrical system of the anti-lock brake system.

10 is a flowchart showing selected programs that are closely related to the present invention from among the programs stored in the ROM of the computer in FIG. 9; FIG.

FIG. 11 is a graph for explaining the flowchart of FIG. 10;

FIG. 12 is a graph for explaining the flowchart of FIG. 10;

FIG. 13 is a graph for explaining the flowchart of FIG. 10;

[Explanation of symbols]

40 Wheel speed sensor 42 Wheel speed sensor 44 Wheel speed sensor 46 Wheel speed sensor 48 Ultrasonic sensor 50 Ultrasonic sensor 60 Controller

Claims (1)

[Claims] 1. A transmitter and its radiation, which are installed in a vehicle equipped with a wheel-based vehicle speed detection device that detects the vehicle speed from the rotational state of the wheels, and which transmits radiation waves toward a road surface with which the wheels are in contact. A Doppler-type vehicle body speed detection device that includes a receiving section that receives reflected waves that are waves reflected on a road surface, and that detects the vehicle speed based on a transmission frequency of the radiated wave and a reception frequency of the reflected wave; and the receiving section. Determine whether the Doppler type vehicle speed detection device is in a normal state in which it can normally detect the vehicle speed, or in an abnormal state in which it cannot normally detect the vehicle speed, using an output signal from or a parameter that changes in relation to it. and a detection state determining means that determines the vehicle body speed detected by the Doppler type vehicle body speed detection device to be the ground vehicle speed of the vehicle when the detection state determining means determines normality, but when determining an abnormality, the wheel-based vehicle body speed detection device A ground vehicle speed detection device comprising: ground vehicle speed determining means for determining the ground vehicle speed using the vehicle speed detected by the method.