JPH0365680A - Ultrasonic vector speedometer - Google Patents

Abstract

PURPOSE:To enable measurement stably with a high accuracy using a small transmitter/receiver by using a plurality of ultrasonic transmitter/receivers to calculate a speed and a direction of movement from a plurality of Doppler frequencies obtained therefrom. CONSTITUTION:For example, two pairs of ultrasonic wave receivers 1 and 2 and 1' and 2' are mounted under a vehicle floor and so arranged that an angle of mounting is 30 deg. to a road surface both in the pairs and 60 deg. on the right and 60 deg. on the left with respect to a Y axis in the center line in a longitudinal way of the vehicle. An ultrasonic beam is radiated to the road surface from transmitters 1 and 1' and the reflected beam is received with receivers 2 and 2' to determine Doppler frequencies fdr and fdl to be outputted therefrom. An arithmetic device (microcomputer) 9 computes fdr-fdl to obtain a speed component vx in an X axis and computes (fdr-fdl)/(fdr+fdl) to obtain an angle thetas in a direction of movement (angle to the Y axis). Thus, from the results, a speed v (=vx/sintheta2) in the direction of movement and a speed Vy (vy/tanthetas) in the Y axis can be determined.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus for measuring the moving direction and speed of a moving object (eg, a vehicle) using a plurality of ultrasonic Doppler detectors.

[Conventional technology]

As a conventional vector speedometer, the Japanese Patent Publication No. 55-4434
There is one shown in Publication No. 7.

The above device uses a so-called spatial filter, which optically detects irregular "unevenness" that naturally exists on the surface of a moving object or a surface facing it, and uses the specific The speed is detected from the detection period of "unevenness" in the interval.

Regarding spatial filters, please refer to "Electronics,
January 1980 issue, pp73-76" and "Illumination Institute Journal,
It is described in 1981, Volume 68, No. 2 PP55-60J, etc.

[Problem to be solved by the invention]

Conventional vector speedometers such as those described above optically detect road surface irregularities, so they require an optical system (
There were various problems in practical use, such as a reduction in detection ability due to dirt adhering to protective glass plates, etc., damage to the optical system due to stones, etc., and the general use of large-capacity floodlights to increase road brightness. .

In particular, in the case of a vehicle, the location where the vector speedometer is installed is mainly under the floor of the vehicle body, so the above points pose a big problem in practice.

The present invention aims to solve the problems of the prior art as described above, and aims to provide a vector speedometer that is small, robust, and not easily affected by secular changes such as dirt. .

[Means to solve the problem]

In order to achieve the above object, one aspect of the present invention is as follows.

The invention is constructed as described in the claims.

That is, in the present invention, a plurality of ultrasonic transducers are used as means for obtaining movement information of a moving object, and the moving speed and direction of movement are calculated from the plurality of Doppler frequencies obtained by them. .

Note that a moving object and a moving surface in the claims refer to the relative movement of an object and a surface that are opposite each other, that is, the movement of at least one of the object and the surface so that the two move relative to each other. means to move;
Both do not necessarily move in absolute coordinates6
For example, if the moving object is a vehicle, the moving surface is a fixed road surface, and if the moving object is a fixed detector,
A combination in which the moving surface is a moving surface such as a belt conveyor is also possible.

[Embodiments of the invention]

FIG. 1 is a block diagram of an embodiment of the present invention, showing a vector speedometer mounted on a vehicle.

First, let me explain the configuration: 1. l' is a transmitter that emits an ultrasonic beam to the road surface, 2.2' is a receiver that receives the reflected beam, and 3 is an oscillator that outputs a signal at a predetermined frequency.
4 amplifies the output signal of the oscillator 3 and transmits it to the transmitter 1. 5゜5' is a preamplifier that amplifies the signals received by the receivers 2 and 2', respectively. 6 and 6' are the frequency of the transmitting signal (output of the oscillator 3) and the receiving signal (preamplifier). 5
An analog multiplier that outputs the sum and difference components with the frequency of the output of the analog multiplier 6゜6', and 7 and 7' are only the difference components of the sum and difference frequencies output from the analog multiplier 6゜6'. 8.8' is a comparator that converts the frequency output from the low-pass filter 7.7' into a pulse train. 9 is a comparator that measures the frequency of the pulse train, Velocity component in the direction Vx
This is a computing unit that computes the angle θS (angle indicating the direction of movement) between g vF, V and vl and V. This computing unit 9
is composed of, for example, a microcomputer.

Next, FIG. 2 is a diagram showing a state in which the detection means consisting of the plurality of transmitters and receivers is attached to a moving object, ie, a vehicle, in which 10 and 10' are tires, 11 is a vehicle body, and 12
indicates the road surface.

As shown in the diagram, ultrasonic transmitters 1, 1' and receiver 2
, 2' are housed in a single casing and attached near the front bumper or rear bumper under the floor of the vehicle.

Next, FIG. 3 is a diagram showing the arrangement angles of a transmitter and a receiver.

As shown in the figure, in this embodiment, the mounting angle of each transmitter and receiver is the same for each set with respect to the road surface.
0", and the right transmitter 1 and receiver 2 are at +60° with respect to the longitudinal reference line (for example, the center line) of the vehicle.
, the transmitter 1' and the receiver 2' on the left side were arranged at an angle of 160°.

Note that this example shows the case where the transmitter and receiver are arranged facing the front of the vehicle, the center line in the longitudinal direction of the vehicle is the Y axis, the line perpendicular to it is the Y axis, and the right side is the Y axis. +, and the left side is -, but the transmitter and receiver may be disposed toward the rear of the vehicle.

[Operation and Use] In FIGS. 1 and 3, the Doppler frequency fdr output from the right receiver 2 and the Doppler frequency fl output from the left receiver s2' are expressed by the following approximate equations, respectively. It will be done.

In the above equation, C is the speed of sound, ■ is the speed of the vehicle in the moving direction, θS is the angle between the Y axis and the moving direction, 0g is the angle between the transducer and the road surface, and fr is the transmission frequency.

In addition, Fig. 4 shows the fdr for the angle θS in the moving direction when the transducer is arranged at θr = +60 @ θ = -60° with the Y axis as a reference, as shown in Fig. 3.
, fcHl is a diagram showing the characteristics standardized by the amount of change. As shown, this characteristic changes according to the cosine function of O8. Note that the vertical axis in FIG. 4 is a value normalized by the Doppler frequency at θ=O°. That is, θ=00
When the Doppler frequency at the time is fo and the Doppler frequency at an arbitrary θ is θ, the vertical axis is the value f/f.

When the difference between the two Doppler frequencies fdr and fdQ, that is, fdr-fd12, is determined, a velocity component vx in the X-axis direction perpendicular to the reference axis Y direction is obtained.

degree O8 is obtained.

That is, vx=fdr-fdQ-(1) It is.

Further, from the above two results, the velocity V in the moving direction and the velocity VF in the Y-axis direction can be determined by the following formula.

As mentioned above, in the arithmetic unit 9 of FIG.
By performing calculations as shown in equations (4) to (4), velocity components in each direction and angles in the moving direction can be detected.

Next, when arranging the detection means consisting of a transmitter and a receiver, what is important is the angle Or, θ with respect to the reference line.
α and the angle to the road surface is 0g.

First, if the angle Or and θ Tomoe with respect to the reference line are set to 60" or more, as shown in Figure 4, if the angle θS between the reference line and the moving direction is around O (for example, within ±15°) can be used within a range that can be approximated to a straight line of a cosine function, so a large amount of variation can be obtained, and since the variation is approximated by a straight line, highly accurate measurement is possible without the need for correction.

Further, the angle 0g with respect to the moving plane varies according to a cosine function as described above, but it is necessary to make 0g small in order to suppress measurement errors due to vehicle attitude, such as rolling and pitching. This is also clear from the fact that the slope of the cosine function near 0 is small. However, if 0g is made too small, the distance from the transducer to the moving surface increases, resulting in a decrease in the reception level of the reflected beam, making it difficult to obtain a stable Doppler frequency. According to the results of vehicle experiments carried out by the inventors in consideration of the conflicting conditions mentioned above, the best value was found around 30". Furthermore, 0g
When is made smaller, the absolute amount of the Doppler frequency increases accordingly, which can contribute to improving measurement resolution.

In addition, as is well known, the ultrasonic transmitter and receiver used in the present invention are sensors using piezoelectric elements, which are small and lightweight, and have high environmental resistance as they are resistant to dirt and impact.
In addition, unlike optical spatial filters, it does not require lighting equipment or the like, so it is suitable for installation under the floor of a vehicle.

Therefore, the automatic brake control system ABS and the four-wheel steering system 4WS.

Various vehicle control devices such as traction control,
Alternatively, it is effective as a measuring device for analyzing vehicle behavior, etc. Of course, it can be applied to various vector velocity measurements other than vehicles.

〔Effect of the invention〕

As explained above, in the present invention, a plurality of ultrasonic transducers are used as means for obtaining movement information of a moving object,
Since the moving speed and moving direction are calculated from the plurality of Doppler frequencies obtained by these, environmental resistance is high.

Vector velocity can be measured stably and with high precision using a small, low-cost transducer. This effect can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a diagram showing a state in which a detection means consisting of a plurality of transmitters and receivers is attached to a moving object, ie, a vehicle, and FIG. FIG. 4 is a diagram showing the arrangement angles of the wave transmitter and the wave receiver, and FIG. 4 is a diagram showing the characteristics in which the amount of change in fdr and fdQ is standardized with respect to the angle θS in the moving direction. <Explanation of symbols> 1, Engineering'... Transmitter 2, 2'... Receiver 3
...Oscillator 4...Drive circuit 5.5'
...Preamplifier 6.6'...Analog multiplier 7.7'...Low pass filter 8.8'...Comparator

Claims (1)

[Claims] A plurality of sets of transmitting means for emitting ultrasonic signals from a moving object toward a moving surface and receiving means for receiving the reflected waves are provided, and each set is set at the same angle with respect to the moving surface, and the moving object are arranged on the moving object so as to make different predetermined angles with respect to the reference line in the front-rear direction, and
The frequency change caused in each received signal due to the Doppler effect due to the relative movement between the moving object and the moving surface, that is, the Doppler frequency, is determined, and the relative velocity and movement direction of the moving object and the moving surface are determined from each set of Doppler frequencies. An ultrasonic vector velocity meter characterized by comprising a calculating means for calculating.