JP2837981B2 - Automotive sensors - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle-mounted sensor for measuring a vehicle speed and / or a road surface friction coefficient (.mu.) Using ultrasonic waves or radio waves.

[0002]

2. Description of the Related Art A conventional on-vehicle μ / speed sensor emits an ultrasonic or radio wave beam having a constant dip angle toward the front of an automobile to measure vehicle speed and μ. For example, an ultrasonic beam is emitted from the transmitter / receiver, and the speed calculator determines the vehicle speed of the own vehicle from the Doppler shift of the reflected wave. Further, the μ of the road surface is estimated by the μ detector based on the change in the intensity of the reflected wave from the road surface toward the transducer.

[0003]

However, a sufficient reflection signal cannot be obtained from a road surface having a small μ, and it may be impossible to measure the vehicle speed, and the measurement of μ may be inaccurate. Was. That is, an equation for calculating the vehicle speed V from the Doppler shift Δf [Hz] observed by the transducer V = (Δf / f) · C · (1 / (2 · cos θ)) (1) where f: transmission Wave frequency [Hz] C: Propagation speed (transmission speed or light speed) of transmission wave θ: Measurement accuracy of vehicle speed V is Doppler shift Δ
It is determined by the observed value of f and the dip angle θ of the beam. For example, if the dip angle θ of the beam is reduced, the measurement accuracy of the vehicle speed V can be increased. However, at this time, if μ on the road surface becomes small, the reflected energy from the road surface to the transducer becomes extremely low, and the vehicle speed V cannot be measured. In order to be able to measure the vehicle speed even on a road surface with a low μ, it is sufficient to increase the dip angle θ of the beam.
Measurement accuracy decreases.

[0004] Further, when the μ of the road surface is to be measured by a transmission beam having a constant dip angle θ, the μ of the road surface has been estimated from the change in the intensity of the reflected wave from the road surface toward the transducer. There was a problem that the measurement accuracy of μ was insufficient.

Furthermore, when trying to measure the vehicle speed and μ using one transmission beam, it has been difficult to select the dip angle θ to the best value regardless of the magnitude of μ on the road surface.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can provide a sufficiently strong reflection irrespective of μ of the road surface, and can improve the vehicle speed and μ.
It is an object of the present invention to obtain an in-vehicle μ / speed sensor having high measurement accuracy.

[0007]

In order to achieve the above object, a first aspect of the present invention is different from the first aspect in that a transducer is divided into a long area in front of the vehicle and a narrow area in the left and right direction. A plurality of vehicles are mounted on the vehicle body so as to transmit a beam to a road surface at a dip angle, transmit an ultrasonic wave or a radio wave beam toward a lower front of the vehicle according to a transmission signal, receive a reflected wave from the road surface, and receive a reception signal. A transmitter / receiver for outputting, a transmitter for providing a transmission signal to the transmitter / receiver, an amplitude detector provided in plurality corresponding to the transmitter / receiver for detecting the amplitude of a reception signal related to the transmitter / receiver, and each amplitude Based on the amplitude detected by the detector, the smallest dip angle of the transducer of the amplitude of the received signal is equal to or more than the predetermined value, or the most of the transducers of the amplitude of the received signal is equal to or less than the predetermined value. Select a transducer with a large dip, Suggest a duplexer dip μ determiner determines the value of the friction coefficient of the road surface from the μ sensor-vehicle, characterized in that it comprises a.

According to a second aspect of the present invention, a plurality of Doppler detectors are provided corresponding to the transmitter / receiver for detecting a Doppler shift from a received signal related to the transmitter / receiver, and are detected by the respective Doppler detectors. Of the Doppler shifts, based on the Doppler shifts detected from the received signals related to the transducer selected by the μ determiner or the next lower dip transducer,
And a speed calculator for calculating the speed of the vehicle.

According to a third aspect of the present invention, in the in-vehicle μ sensor or the in-vehicle μ / speed sensor according to the first or second aspect, the plurality of transducers are symmetrically arranged one by one before and after the vehicle. It is characterized by the following.

According to a fourth aspect of the present invention, an ultrasonic wave or a radio wave beam that is long and narrow in the left and right direction is transmitted toward the front lower road surface of the vehicle in response to the transmission signal, and the reflected wave from the road surface is received. A transmitter / receiver that outputs a reception signal and a transmitter that supplies a transmission signal to the transmitter / receiver, and a time-division measurement timing is continuously set so as to divide a beam irradiation area on a road surface into a plurality of portions along a vehicle front. Timing generators, a plurality of amplitude detectors corresponding to the number of time-division measurement timings to detect the amplitude of the received signal at different time-division measurement timings, and detection by each amplitude detector Based on the amplitude to be received, the latest time-division measurement timing among the time-division measurement timings in which the amplitude of the received signal is equal to or larger than a predetermined value, or the time when the amplitude of the received signal is equal to or smaller than a predetermined value. A μ-determining device that selects the earliest time-division measurement timing among the measurement timings and determines a value of a friction coefficient of a road surface from a dip angle corresponding to the time-division measurement timing; suggest.

According to a fifth aspect of the present invention, an ultrasonic or radio wave beam that is long and narrow in the left-right direction is transmitted toward the front lower road surface of the vehicle in response to a transmission signal, and a reflected wave from the road surface is received. A transmitter / receiver that outputs a received signal, a transmitter that supplies a transmission signal to the transmitter / receiver, and time-division measurement timing are continuously generated so that the beam irradiation area on the road surface is divided into multiple parts along the front of the vehicle. A timing generator to perform the operation, time-divisionally operated at the time-division measurement timing, an amplitude detector that detects the amplitude of the received signal, and time-division where the amplitude of the received signal is equal to or larger than a predetermined value based on the amplitude detected by the amplitude detector. Select the latest time-division measurement timing among the measurement timings, or the earliest time-division measurement timing among the time-division measurement timings in which the amplitude of the received signal is equal to or less than a predetermined value. Suggest μ sensor-vehicle, characterized in that it comprises a μ determiner determines the value of the friction coefficient of the road surface from the dip corresponding to the ring.

According to a sixth aspect of the present invention, there is provided an on-vehicle μ sensor according to the fourth or fifth aspect, wherein the number of time-division measurement timings generated from the received signal at different time-division measurement timings is detected. A plurality of Doppler detectors provided corresponding to the time division measurement timing selected by the μ determiner among the Doppler shifts detected by each Doppler detector, or a portion related to this time division measurement timing Next, a speed calculator that calculates the speed of the vehicle based on the Doppler shift detected from the received signal at the time-division measurement timing relating to the portion where the dip is small,
We propose a μ / speed sensor for in-vehicle use.

A seventh aspect of the present invention is the vehicle-mounted μ sensor or the vehicle-mounted μ / speed sensor according to the fourth to sixth aspects,
It is characterized in that the transducers are arranged symmetrically one by one in front and behind the vehicle.

[0014]

According to the present invention, among a plurality of transducers provided at different dip angles, the n-th transducer whose amplitude of the received signal is equal to or larger than a predetermined value and among which the dip angle θ is the smallest is selected. The road surface μ is detected based on the selected θn. Alternatively, the n'th transducer having the amplitude of the received signal equal to or less than the predetermined value and the largest inclination angle θ is selected, and μ of the road surface is detected based on the θn '. That is, the amplitude of the received signal is detected by each of the plurality of amplitude detectors, and the n-th or n-th transducer is selected by the μ determiner based on the amplitude detected by each amplitude detector, and the inclination angle θn Alternatively, the value of μ on the road surface is determined from θn ′. As described above, the angle immediately before or immediately after the decrease in the amplitude of the received signal as a result of total reflection is θn or θn
′, And μ is determined based on this.
As compared with a case where μ is determined by a single transducer having a constant inclination angle θ, μ can be measured more stably and with high accuracy.

According to a second aspect of the present invention, the speed V of the vehicle is detected based on the reception signal of the selected n-th transducer. That is, the Doppler shifts Δf are respectively detected from the plurality of received signals by the plurality of Doppler detectors, and further, the Doppler shifts Δf related to the n-th transducer are detected.
, The speed V of the vehicle is calculated by the speed calculator. Here, the Doppler shift Δf to be subjected to the speed calculation relates to the n-th transducer, and the transducer is selected by the μ determiner as described above, or The dip angle is the second smallest after the n-th transducer selected by the μ decision unit. Therefore, while a sufficient amplitude is detected for detecting the speed V of the vehicle, the received signal of the transducer having the smallest inclination angle θ is used for detecting the speed V, and the detection accuracy of the speed V of the vehicle is improved. Secured.

According to a third aspect of the present invention, a so-called pair beam configuration is realized. With the pair beam configuration, the Doppler shift in the vertical direction of the road surface, which is unnecessary for vehicle speed detection, can be canceled by the output of the transducer group at the front of the vehicle and the output of the transducer group at the rear of the vehicle. Also, a primary correction for the trim heel is realized.

Further, in the present invention, the directivity of the transducer is long in front of the vehicle and narrow in the left-right direction. A time-division measurement timing is continuously generated by the timing generator so as to divide the beam irradiation area on the road surface into a plurality of portions along the front of the vehicle, and a reception signal obtained from such a transducer is subjected to time-division processing. . That is, the amplitudes of the received signals are respectively detected by the plurality of amplitude detectors, and the n-th or n-th time-division measurement timing is selected by the μ determiner based on the amplitudes detected by the respective amplitude detectors. The value of μ on the road surface is determined from θn or θn ′. In this manner, the slowest n-th time-division measurement timing among the time-division measurement timings at which the amplitude of the reception signal is equal to or more than the predetermined value is obtained, or the time-division measurement timing at which the amplitude of the reception signal becomes equal to or less than the predetermined value is obtained. The earliest n 'time-division measurement timing is determined, and the μ of the road surface is detected based on the inclination angle θn or θn' of the part corresponding to this timing. Thus, unlike the first aspect, a single transducer is sufficient.

According to a fifth aspect of the present invention, the amplitude detector operates in a time division manner at the time division measurement timing, and the amplitude of the received signal is detected. Thus, the same μ detection is realized by a single amplitude detector instead of the plurality of amplitude detectors according to claim 4.

According to a sixth aspect of the present invention, a plurality of Doppler detectors detect a Doppler shift Δf from a plurality of received signals, respectively, and calculate a speed based on the Doppler shift Δf related to the n-th time division measurement timing. The speed V of the vehicle is calculated by the device.

According to the seventh aspect of the present invention, the same operation as the second aspect can be obtained.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a vehicle-mounted μ / speed sensor according to a first embodiment of the present invention. As shown in this figure, the present embodiment has different inclination angles θ1, θ
N (N: plural) transducers 10-1, 10-2,... Attached to the vehicle at 2,.
10-N, a transmitter 20 for supplying the same transmission signal to the transmitter / receiver 10, and a μ
, And a vehicle speed detector 31 that detects the vehicle speed of the vehicle from the waves received by the transducers 10. The inclination angles θ1, θ2,... ΘN are θ1 <θ2
<... <θN The transmission signal may be a continuous wave or a pulse wave.

In this embodiment, when a transmission signal is supplied from the transmitter 20 to each of the transducers 10, as shown in FIG. 2, N transducers 10-1, 10-2,. −
The beam transmitted from N enters the road surface R at different dips. This transmitted wave is reflected by the road surface R, and a part of the reflected wave corresponds to the corresponding one of the transducers 10-1, 10-2,.
0-N. The reception signal obtained in this manner is transmitted from each transducer 10 to the μ detector 30 and the vehicle speed detector 3.
It is led to 1.

As shown in FIG. 3, when the transducers (transducers TR) 10-1, 10-2,..., 10-N are arranged in numerical order and the amplitudes of the received signals are compared, the amplitude of a given number is extremely high. Suddenly changes from a small value to a large value. The μ detector 30 obtains the amplitude of the received signal by the built-in amplitude detector, and determines the amplitude of the received signal.
The number n (4 in the figure) of (the smallest numbered transducer capable of obtaining a large amplitude, the transducer 10-4 in FIG. 3) is obtained. The μ detector 30 knows the dip angle θn from this number n,
Μ is detected based on the inclination angle θn, and the detection result is output to the brake control system. The brake control system executes a predetermined braking operation or the like according to the detection result.

The sudden change in the amplitude occurs because the transmission beam is totally reflected on the road surface R when the inclination angle θ is small. For example, when the road surface R is rough (when μ is large), the transmission waves related to any of the transducers 10 are reflected by the road surface R regardless of the inclination angle θ. In this case, the reflection energy is sufficiently large for any inclination angle θ. However, when the μ of the road surface R is small, the transmission beam having a small inclination angle θ is totally reflected, and the energy of the reflected wave reflected by the transducer for transmission becomes extremely small. Therefore, as described above,
A transducer 10- in which a sufficiently large received signal amplitude is obtained
If n is obtained and μ is detected by using the number n of the transducer 10, reflection of sufficient intensity can be obtained regardless of μ on the road surface, and μ measurement can be performed with sufficient accuracy.

On the other hand, the detection of the vehicle speed in this embodiment
This is executed by the vehicle speed detector 31. In order for the vehicle speed detector 31 to detect the vehicle speed V based on the equation (1), the received signal to be processed by the vehicle speed detector 31 must have a sufficient amplitude. In this embodiment, as described above,
The transducer 10 having a sufficient amplitude obtained by the detector 30
Since the number n of −n has been obtained, the vehicle speed detector 31 inputs this number n from the μ detector 30. Vehicle speed detector 31
Therefore, the vehicle speed V is detected based on the received signal having the smallest dip angle among the received signals having the sufficient amplitude. The vehicle speed detector 31 outputs a detection result to the brake control system. The brake control system executes a predetermined braking operation or the like according to the detection result.

The detection of the vehicle speed V is performed based on equation (1). That is, the vehicle speed detector 31 calculates the Doppler shift Δf and detects the vehicle speed V. At this time, the measurement accuracy of the vehicle speed V improves as the inclination angle θ decreases. If the reception signal having the smallest inclination is selected from the reception signals having a sufficient amplitude as in this embodiment, the measurement accuracy of the vehicle speed V can be ensured.

FIG. 4 shows a more detailed configuration of this embodiment. This figure shows the amplifiers 40-1, 40-2,... 40-N for amplifying the received signal, and also shows the internal configurations of the μ detector 30 and the vehicle speed detector 31.

The μ detector 30 includes amplitude detectors 30-1, 30-2,..., 30-N so as to correspond to the respective transducers 10. Amplitude detectors 30-1, 30-2, ..., 30-
N detects the amplitude of the received signal from the corresponding transducer 10. The μ detector 30 further includes a μ determiner 30-0. μ determiner 30-0 is an amplitude detector 30-1, 30
−2... 30-N are taken in, and μ is obtained.

The vehicle speed detectors 31 are Doppler detectors 31-1, 31-2,... 31 corresponding to the respective transducers 10.
-N. Doppler detector 31-1, 31-
2,... 31-N detect the Doppler shift contained in the received signal. The vehicle speed detector 31 further includes a speed calculator 31
−0. The vehicle speed detector 31 is a Doppler detector 3
The detection results of 1-1, 31-2,.
Find the vehicle speed V. At this time, as described above, the vehicle speed detector 31 takes in the number n of which the amplitude changes suddenly from the μ detector 30, and obtains the vehicle speed V by the equation (1) using the dip angle θn related to the number.

FIG. 5 shows the configuration of a second embodiment of the present invention. This embodiment differs from the first embodiment shown in FIGS. 1 and 4 in that the number of transducers 10 is one. On the other hand, the amplitude detector and the Doppler detector are N as in the first embodiment.
Are provided. In this embodiment, a single transducer 1
The timing generator 50 and the switch 6 are used to switch the received signal of 0 to be supplied to the amplitude detector and the Doppler detector while switching.
0 is provided.

FIGS. 6 and 7 show the operation principle and operation timing of this embodiment. When a transmission timing is given from the timing generator 50 to the transmitter 20 and, for example, a pulse-like transmission signal is given from the transmitter 20 to the transmitter / receiver 10 at this timing, a beam is emitted from the transmitter / receiver 10 toward the road surface R. Sent. The transducer 10 used in this embodiment has a directivity that is long in the front and narrow in the horizontal direction, as indicated by B in FIG. That is, the transmitted beam has a shape like B on the road surface R.

Accordingly, the reflected wave is received by the transmitter / receiver 10 at different times depending on the portion of the road surface R reflected. As shown in FIG. 7, after a time τmin has elapsed from the generation of the transmission pulse, the reflected wave from the part SN shown at the rearmost in FIG. 6 (that is, closest to the transducer 10) is received by the transducer 10. Then, the reflected wave from the portion SN-1 is received by the transducer 10, and finally, the reflected wave from the foremost portion (that is, the portion farthest from the transducer 10) is received by the transducer 10. (Time τmax). The reflected waves from these parts S1, S2,... SN are input to the amplifier 40 as reception signals from the transmitter / receiver 10, and after being amplified, are input to the switch 60. The switch 60 switches at the time-division measurement timings # 1, # 2,... #N provided by the timing generator 50, and switches and supplies the received signal amplified by the amplifier 40 to each amplitude detector and Doppler detector. For example, at timing # 1, the received signal related to the portion S1 of FIG. 6 is the amplitude detector 30-1 and the Doppler detector 31-1, and at timing # 2, the received signal related to the next portion S2 is the amplitude detector 30-2 and Doppler detector 3
The supply destination is changed to 1-2,.... The time division measurement timings # 1, # 2,..., #N are set so as to divide the time from the lapse of time τmin to the lapse of τmax after the generation of the transmission pulse into N pieces.

Thus, the amplitude detectors 30-1 and 30-3
0-2,... 30-N and Doppler detectors 31-1, 31
−2,... 31-N have different portions S1, S2,.
Is supplied. Time division measurement timing #
.., #N are a μ detector 30 and a vehicle speed detector 31
The amplitude detector and the Doppler detector operate in synchronization with the switching of the switch 60, and the corresponding parts S1, S
2,... Detection of the amplitude of the signal received from the SN and detection of the Doppler component are performed. Each of the portions S1, S2,... SN has a different inclination angle θ1, θ2,.
Each of the amplitude detectors and the Doppler detectors processes a received signal having a different inclination angle θ1, θ2,... θN as in the first embodiment.

As shown in FIG. 7, the pulse width PW of the received signal obtained in this embodiment is PW ≦ τmax−
τmin. This is because total reflection occurs at a portion where the inclination angle θ is small (a portion closer to the front), and a reflected wave with sufficient energy cannot be obtained. Considering the case where μ of the road surface R gradually decreases, the reception pulse width PW decreases, and the N amplitude detectors 30-1, 30-2,.
Only the signal corresponding to the rear portion of 0-N is supplied with the received signal having a sufficient amplitude. In the present embodiment, the μ determiner 30-0 determines the smallest inclination angle θn among the inclination angles θ at which a received signal having a sufficient amplitude is obtained.
Is determined by determining the latest time-division measurement timing among the amplitudes detected by the amplitude detector that are equal to or greater than a predetermined value. The speed calculator 31-0 calculates the speed V of the vehicle from the Doppler component Δf detected from the received signal related to the inclination θn.

In other words, in this embodiment, in the first embodiment, the N transducers 10-1, 10-2,.
The same operation and effect as those obtained by using N can be obtained. Furthermore, only one transducer 10 is required, and the apparatus can be easily attached to the vehicle body, is inexpensive, and has high reliability.

In the present embodiment, one amplitude detector is used instead of the N amplitude detectors 30-1, 30-2,..., 30-N, and the time division operation is performed at the time division measurement timing. It does not matter. In this case, the configuration of the μ detector 30 becomes simpler.

Further, it is more preferable to adopt a so-called pair beam configuration. That is, one or two transducers are arranged at the front and rear of the vehicle so as to be geometrically symmetric. For example, in the case of the embodiment shown in FIG.
., 10-N are arranged at the front and rear of the vehicle one by one. In the embodiment of FIG. 5, the transducers 10 are arranged at the front and rear of the vehicle one by one. . If the output of each transducer is combined with the output of the corresponding transducer after this, the vertical Doppler shift of the road surface R unnecessary for speed detection or the like can be canceled.

That is, as shown in FIG.
If the reflected wave from the vehicle contains a vertical velocity component due to the unevenness of the road surface R, and the horizontal velocity is V and the vertical velocity is U, the Doppler frequency of the reflected wave received by the transceiver at the front of the vehicle fd1 is expressed as fd1 = (2f / C) · (Vcos θ−Usin θ) (2) Here, θ is a dip angle. Conversely, the Doppler frequency fd2 of the reflected wave received by the transducer having the same inclination provided at the rear of the vehicle is fd2 = (2f / C) · (−Vcos θ−Usin θ). Then, the difference between the equations (2) and (3) is fd = fd1−fd2 = (4fV / C) cosθ. In this way, by obtaining the difference between the outputs of the transducers before and after the vehicle, a numerical value that does not include U can be obtained. By detecting the vehicle speed based on this numerical value, a more accurate vehicle speed without the influence of the vertical speed U can be detected.

Also, with such a pair beam structure,
Eliminates the effect of trim heels. Now, suppose that θ has increased by a small angle δ in the equation fd1 = (2f / C) Vcos θ ignoring the vertical velocity U in the equation (2). That is, it is assumed that the vehicle body is inclined by δ. In this case, the Doppler frequency can be expressed as fd1 ′ = (2f / C) Vcos (θ + δ). Therefore, the error E1 of the Doppler frequency when the vehicle body is tilted by δ is Becomes On the other hand, for the transducer 10 behind the vehicle, the Doppler frequency fd2 'when the vehicle body is tilted by δ is fd2' = (2f / C) Vcos (θ-δ). For a pair beam, fd '= fd1'-fd2'
The problem is that fd
'Is the error E12. E12 is expressed as follows: E12 = ((cos δ−tan θ sin δ−1) + (cos δ + tan θ sin δ−1)) / 2 = cos δ−1 Therefore, by using a paired beam, the error is reduced and the influence of the trim heel is reduced.

Further, in the above description, the number of the receiver in which the amplitude of the received signal is equal to or larger than the predetermined value, or the dip angle of the portion corresponding to the latest timing among the time-division timings in which the amplitude is equal to or larger than the predetermined value. Thus, μ and vehicle speed were detected. This may use not the number of the receiver or the time-division timing at which the amplitude is equal to or more than the predetermined value, but the number or timing immediately before that. For example, in the example of FIG. 3, the number of the immediately preceding receiver whose amplitude exceeds a predetermined value, such as using the receiver 10-3, may be used. The dip angle of the part related to the timing immediately before the timing may be used. Even in this case,
The above-described functions, effects, and the like are suitably realized.

[0042]

As described above, according to the first aspect of the present invention,
According to the present invention, among a plurality of transducers provided at different dip angles, the amplitude of the received signal is equal to or more than a predetermined value, and among them, the nth transducer having the smallest dip angle θ, or the amplitude of the received signal Is less than or equal to a predetermined value and further selects the n'th transducer having the largest inclination angle θ,
, The μ of the road surface is detected, so that μ can be measured stably and with high accuracy.

According to the second aspect of the present invention, since the speed V of the vehicle is detected based on the reception signal of the n-th transducer selected in the same manner, it is sufficient to detect the speed V of the vehicle. And the detection accuracy of the speed V of the vehicle is improved and ensured.

According to the third aspect of the present invention, a so-called pair beam configuration is realized, the Doppler shift in the vertical direction of the road surface is canceled, and the primary correction of the trim heel is realized, so that a more preferable detection result can be obtained. .

According to the fourth aspect of the present invention, the μ detection is performed in a time-division manner so as to divide the beam irradiation area on the road surface into a plurality of portions along the front of the vehicle, and the beam is long in front of the vehicle and narrow in the lateral direction. Because a single transducer is used, a single transducer is sufficient, and the apparatus is smaller and suitable for mounting on a car. Further, the resolution of the μ measurement can be realized without complicating and enlarging the configuration of the transducer, and the apparatus has excellent measurement accuracy, reliability, and stability.

According to the fifth aspect of the present invention, since the amplitude detector is operated in a time-division manner at the time-division measurement timing, a small apparatus configuration using a single amplitude detector is provided.
Can be realized in the same manner as in the above.

According to the sixth aspect of the present invention, the speed V of the vehicle is detected by time division measurement.
Alternatively, an effect similar to that of 5 is obtained for vehicle speed measurement.

According to the seventh aspect of the present invention, the same effect as the third aspect can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a vehicle-mounted μ / speed sensor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a beam transmission direction in this embodiment.

FIG. 3 is a diagram showing the principle of selecting a transducer in this embodiment.

FIG. 4 is a diagram showing a detailed configuration of this embodiment.

FIG. 5 is a diagram showing a configuration of a vehicle-mounted μ / speed sensor according to one embodiment of the present invention.

FIG. 6 is a diagram showing a division of a beam receiving portion in this embodiment.

FIG. 7 is a diagram showing time-division measurement timing in this embodiment.

FIG. 8 is a diagram for explaining an effect when this embodiment is a pair beam.

[Explanation of symbols]

 10-1, 10-2,... 10-N transmitter / receiver 20 transmitter 30 μ detector 30-0 μ determiner 30-1, 30-2,... 30-N amplitude detector 31 vehicle speed detector 31-0 .. 31-N Doppler detector 50 Timing generator 60 Switch θ-1, θ-2,... Θ-N Angle of dip # 1, # 2,. timing

Continuation of the front page (56) References JP-A-3-115987 (JP, A) JP-A-2-236451 (JP, A) JP-A-51-65678 (JP, A) JP-A-53-17376 (JP) (A) JP-A-1-148985 (JP, A) JP-A-63-124677 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01S 13/50-13/64 G01S 15/50-15/62

Claims (7)

(57) [Claims] 1. A plurality of vehicles are mounted on a vehicle body so as to transmit a beam to a road surface at different dip angles so as to divide and cover an area long and narrow in the left-right direction in front of the vehicle. A transmitter / receiver that transmits an ultrasonic wave or a radio wave beam toward a receiver, receives a reflected wave from a road surface, and outputs a reception signal, a transmitter that supplies a transmission signal to the transmitter / receiver, and a plurality of transmitters / receivers corresponding to the transmitter / receiver. An amplitude detector for detecting the amplitude of the received signal related to the transducer, and the most dip angle of the transducers whose amplitude of the received signal is equal to or more than a predetermined value based on the amplitude detected by each amplitude detector. The transducer having the largest dip angle is selected from the transducers having a small or the amplitude of the received signal is equal to or less than a predetermined value, and the value of the friction coefficient of the road surface is determined from the dip angle of the transducer.
A μ sensor for mounting on a vehicle, comprising: a judgment unit. 2. A vehicle-mounted μ sensor according to claim 1, a plurality of Doppler detectors provided corresponding to the transducers for detecting a Doppler shift from a received signal related to the transducer, and each Doppler detection. The vehicle speed is calculated based on the Doppler shift detected from the transmitter / receiver selected by the μ determiner or the received signal related to the next smaller transducer in the Doppler shift detected by the detector. A μ / speed sensor for a vehicle, comprising: 3. The on-vehicle μ sensor or on-vehicle μ / speed sensor according to claim 1 or 2, wherein the plurality of transducers are symmetrically arranged one set before and after the vehicle. . 4. A transmission / reception that transmits an ultrasonic wave or a radio wave beam that is long and narrow in the left-right direction toward a front lower road surface of the vehicle in response to a transmission signal, receives a reflected wave from the road surface, and outputs a reception signal. A wave generator, a transmitter for providing a transmission signal to a transmitter / receiver, and a timing generator for continuously generating time-division measurement timing so as to divide a beam irradiation area on a road surface into a plurality of parts along a vehicle front, A plurality of amplitude detectors are provided corresponding to the number of time-division measurement timings to detect the amplitude of the reception signal at different time-division measurement timings, and the received signal is detected based on the amplitude detected by each amplitude detector. Of the time-division measurement timings whose amplitudes are equal to or greater than a predetermined value, or the latest time-division measurement timings where the amplitude of the received signal is equal to or less than a predetermined value. Select division measurement timing early times, vehicle μ sensor, characterized in that and a μ determiner determines the value of the friction coefficient of the road surface from the corresponding dip in the time-division measurement timing. 5. A transmission / reception that transmits an ultrasonic wave or a radio wave beam that is long and narrow in the left-right direction toward a front lower road surface of the vehicle according to a transmission signal, receives a reflected wave from the road surface, and outputs a reception signal. A wave generator, a transmitter for providing a transmission signal to a transmitter / receiver, and a timing generator for continuously generating time-division measurement timing so as to divide a beam irradiation area on a road surface into a plurality of parts along a vehicle front, An amplitude detector that operates in a time-division manner at the time-division measurement timing to detect the amplitude of the received signal; and, based on the amplitude detected by the amplitude detector, the latest of the time-division measurement timings in which the amplitude of the received signal is equal to or greater than a predetermined value. The earliest time-division measurement timing is selected from the time-division measurement timings or the time-division measurement timings in which the amplitude of the received signal is equal to or less than a predetermined value. Determining the value of the friction coefficient of the road surface from the corner μ
A μ sensor for mounting on a vehicle, comprising: a judgment unit. 6. A vehicle-mounted μ sensor according to claim 4 or 5, wherein a plurality of μ sensors are provided corresponding to the number of time-division measurement timings to detect Doppler shifts from received signals at different time-division measurement timings. Doppler detector, of the Doppler shift detected by each Doppler detector, time-division measurement timing selected by the μ determiner,
Or a speed calculator that calculates the speed of the vehicle based on the Doppler shift detected from the received signal at the time-division measurement timing related to the portion having the next smaller dip angle than the portion related to the time-division measurement timing. Features μ / speed sensors for vehicles. 7. The mu sensor or mu · speed sensor for automotive vehicle according to claim 4 to 6, wherein vehicle sensor, characterized in that the transducer symmetrically disposed one by one before and after the vehicle.