JP3037505B2 - Doppler velocity measuring device for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Doppler velocity measuring apparatus for a vehicle for measuring a ground speed by applying the Doppler effect of aerial ultrasonic waves.

[0002]

2. Description of the Related Art A transmitter / receiver is provided at a predetermined position in front of a vehicle, an ultrasonic wave is emitted from the transmitter / receiver toward a road surface at a predetermined angle, a reflected wave is received, and a ground speed is measured by Doppler effect. Speed measuring devices are well known in the art.
However, in this device, the posture of the vehicle, so-called trim, changes depending on the state of the vehicle occupant and the load, and the change in the angle of incidence of the ultrasonic wave on the road surface is large with this change, and the measurement error is large. Therefore, at present, a device called a Jain's system or a pair beam system, which includes transducers before and after a vehicle, calculates an average value of the speeds obtained by the transducers, and reduces a measurement error has been developed.

FIG. 2 is a block diagram showing an example of a pair beam type Doppler velocity measuring device for a vehicle, in which a predetermined burst wave is generated from a transmission burst wave generation circuit 1, amplified by a transmission amplification circuit 2, and then transmitted and received. The ultrasonic waves 5A and 5B are transmitted to the switching circuits 3A and 3B, respectively, and are emitted from the front transducer 4A and the rear transducer 4B into the air at a predetermined timing downward and forward and rearward of the vehicle. The emitted ultrasonic waves 5A and 5B are reflected on the road surface 6, respectively, and the reflected waves are received by the respective transducers 4A and 4B, and the respective received signals are transmitted to the respective reception circuits 7A and 7A via the transmission / reception switching circuits 3A and 3B.
7B are amplified and input to the speed calculation circuit 8, respectively. Then, the speed is calculated by the speed calculation circuit 8 for each of the received signals whose frequency has been shifted by the Doppler effect,
The average of these is output as speed data.

Next, calculation performed by the speed calculation circuit 8 and a speed error will be described. The frequency of the transmission burst wave is f ₀ , the reception frequency is f _A , the set angle of incidence on the road is θ _A ,
When the sound velocity is C, the forward ground speed _{V A, V A = (f} A -f 0) · C / (2 · f 0 · cosθ A) ··· (1) , and the one transducer forward In the apparatus described above, for example, in the apparatus in which the incident angle θ _A is set to 45 °, when the incident angle changes by 5 ° due to the trim change, this change causes a 9% speed error.

[0005] FIG. 2 also shows a transmitter / receiver provided behind the vehicle.
In the apparatus is shown, the incident angle to the road surface theta _B, rear ground speed V _B when the reception frequency of the reflected wave was f _B incident after a transducer. 4B, V _B = (f ₀ -f _B ) · C / (2 · f ₀ · cos θ _B ) (2), and the average ground speed (V) is obtained from V = (V _A + V _B ) / 2 (3). Output as data. In this pair beam method, θ _A
= Θ _B = 45 °, when the angle of incidence changes by 5 ° due to trim change, this change causes about 0.4%
Speed error occurs, and the error can be reduced as compared with the above-described single transducer device.

[0006]

As described above, the above-mentioned conventional Doppler velocity measuring apparatus for a vehicle includes a pair beam type apparatus for reducing a measurement error due to a trim change. Cannot be ignored. That is, in this type of apparatus, there are many error factors other than the error due to the trim change, for example, the error due to the difference between the calculated value of the sound velocity C and the actually measured value. There is a problem that the error due to the change must be minimized.

The present invention has been made to solve such a problem, and an object of the present invention is to provide a Doppler velocity measuring apparatus for a vehicle which can further reduce an error due to a change in trim.

[0008]

According to the Doppler velocity measuring device for a vehicle according to the present invention, the ultrasonic wave in a burst form is emitted from a transmitter / receiver for a vehicle front and a vehicle rear and reflected on a road surface to transmit each of the above-mentioned transmission / reception waves. The angle of incidence of each of the transducers on the road surface is calculated based on the time until the beam enters the device, and the angle of incidence on the setting is corrected to calculate velocity data. That is, when the trim change of the vehicle is detected by a trim angle detection circuit, and the speed is obtained by calculation from the frequency deviation caused by the Doppler effect, the angle of incidence on the road surface is corrected and calculated.

[0009]

In the present invention, the time from transmission to reception is measured by using the ultrasonic waves to be used as burst ultrasonic waves, whereby the distance between each transducer and the road surface can be obtained. If transmission / reception is performed by the transducers directed obliquely downward at the front and rear of the vehicle, the trim angle can be detected based on the ratio between the front and rear distances. Therefore, if the incident angle is corrected at the time of speed calculation using the trim angle, accurate speed measurement can be performed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention.
In the figure, 1 is a transmission burst wave generation circuit, 2 is a transmission amplification circuit, and 3A and 3B are transmission / reception switching circuits (symbol A indicates a vehicle front, symbol B indicates a vehicle rear, the same applies hereinafter), 4
A and 4B are transmitters and receivers, 5A and 5B are emitted burst ultrasonic waves, 6 is a road surface, 7A and 7B are reception circuits, 8 is a speed calculation circuit, 9 is a trim angle detection circuit, and trim is a trim. Except for the angle detection circuit 9, the configuration is the same as the conventional configuration shown in FIG.

Next, the operation will be described. A predetermined burst wave is generated from the transmission burst wave generation circuit 1, amplified by the transmission amplification circuit 2, sent to the transmission switching circuits 3 A and 3 B, and transmitted from the front and rear transducers 4 A and 4 B to a predetermined frequency. At the timing, the ultrasonic waves 5A and 5B are emitted forward and rearward and downward of the vehicle. Launched ultrasonic waves 5A, 5B
Are respectively reflected by the road surface 6 and the respective transducers 4
The reflected waves are received at A and 4B, and the respective received signals enter the respective receiving circuits 7A and 7B via the respective transmission / reception switching circuits 3A and 3B and are amplified. The amplified received signals are sent to the speed calculation circuit 8 and , And the trim angle detection circuit 9 detects the trim angle, and corrects the above-mentioned set incident angles θ _A and θ _B.

As shown in FIG. 1, the transmission timing of the burst wave is input to the trim angle detection circuit 9 from the transmission burst wave generation circuit 1, and the respective reception timings are input from the respective reception circuits 7A and 7B. , The distance between each of the transducers 4A, 4B and the reflection point on the road surface 6 is determined, and the trim angle is determined from the ratio of the distance in front of and behind the vehicle. Then, the obtained trim angle is input as information to the speed calculation circuit 8, and the incident angles θ _A and θ _B on the setting are set.
Is corrected, and the calculations according to the above-described arithmetic expressions (1) to (3) are performed to obtain speed data.

[0013]

As described above, the Doppler velocity measuring apparatus for a vehicle according to the present invention can obtain velocity data by correcting an incident angle due to a change in trim, and can trim a vehicle according to a change in a vehicle occupant or a load. There is an effect that even if the speed changes, stable speed data can be obtained without being affected by the change.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 transmission burst wave generation circuit 2 transmission amplification circuit 3A, 3B transmission / reception switching circuit 4A, 4B transmission / reception device 5A, 5B each burst-shaped ultrasonic wave 6 road surface 7A, 7B reception circuit 8 speed calculation circuit 9 trim angle detection circuit

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-3-57985 (JP, A) JP-A-2-280077 (JP, A) JP-A-3-269388 (JP, A) JP-A-61- 201176 (JP, A) JP-A-4-2522985 (JP, A) JP-A-4-357486 (JP, A) JP-A-5-40173 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S ⁷ /00-7/64 G01S 13/00-15/96

Claims (1)

(57) [Claims] 1. _A burst-like ultrasonic wave (f ₀ ) is emitted toward a road surface in front of the vehicle in the forward direction of the vehicle (a set incident angle on the road surface is θ _A ), and a reflected wave (f _A ) from the road surface is emitted. Means to obtain the forward ground speed (V _A ) by calculating the following equation (1): V _A = (f _A −f ₀ ) · C / (2 · f ₀ · cos θ _A ) , C is the speed of sound), means for determining the time (T _A ) from the emission of the ultrasonic wave (f ₀ ) to the reception of the reflected wave (f _A ), The angle of incidence on the road surface is θ _B ) The above ultrasonic wave (f ₀ ) is emitted, the reflected wave (f _B ) from the road surface is received, and the rear ground speed (V _B )
V _B = (f ₀ −f _B ) · C / (2 · f ₀ · cos θ _B ) means for calculating by the equation (2), the ultrasonic wave (f ₀ ) is emitted and the reflection is performed. Means for obtaining the time (T _B ) until the wave (f _B ) is received, the so-called trim of the vehicle changes depending on the state of the occupant and the load of the vehicle, and the actual incident angle changes to the above-mentioned set incident angle (θ) _A ) When there is a difference between ( _A ) and (θ _B ), means for calculating the difference by the time difference between (T _A ) and (T _B ) and correcting the calculation by the above equations (1) and (2) V = (V _A + V _B ) / 2... A vehicle Doppler velocity measuring device comprising means for outputting a vehicle velocity (V) according to equation (3).