JPH03115988A - Speed detecting device - Google Patents

Abstract

PURPOSE:To facilitate signal processing without misdetecting the Doppler shift quantity of an ultrasonic wave signal even against disturbance such as a wind by using an ON/OFF ultrasonic wave signal which has one pulse part consisting of a group of waves and calculating a vehicle speed according to the Doppler shift quantity of the pulse part. CONSTITUTION:A continuous wave signal which is inputted from an oscillator 1 to a modulation part 2 alternates between a period t1 wherein the continuous signal wave is outputted and a period t2 wherein the signal is not outputted to generate the ON/OFF continuous wave signal. An ultrasonic wave signal device 3 outputs the ON/OFF ultrasonic wave signal whose sound pressure level is large in the period t1 and nearly 0 in the period t2. The ON/OFF ultrasonic wave signal is reflected irregularly by the road surface 4 and affected by Doppler effect when received by a receiving sensor 5, so that an ON/OFF period is T-DELTAt. A counter part 8 measures the pulse period T-DELTAt and a vehicle speed calculation part 9 finds the vehicle speed according to the relation between the Doppler shift quantity DELTAt and vehicle speed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a speed detection device that detects ground speed using the Doppler effect of ultrasonic waves.

(Prior Art) For a moving object such as an automobile that moves on a road surface, there is a demand for detecting the moving speed of the moving object with respect to the road surface, that is, the ground speed with high accuracy.

One method for detecting the ground speed of a moving object is to provide the moving object with an ultrasonic transmitter and a receiving sensor, transmit ultrasonic waves from the transmitter toward the road surface, and detect the ultrasonic waves from the road surface. A method is known in which a receiving sensor receives diffusely reflected waves, detects the Doppler shift frequency in the diffusely reflected waves, and thereby detects the ground speed of a moving body.

A conventional device for detecting ground speed using such a Doppler effect is disclosed, for example, in Japanese Patent Application Laid-Open No. 62-12 (1988) (No. 378).

(Problems to be Solved by the Invention) However, since the above-mentioned ultrasonic waves propagate using air as a medium, signal strength fluctuations are likely to occur due to disturbances such as wind, and the period of each wave of the ultrasonic signal fluctuates. There is a possibility that this detection may occur depending on the above-mentioned conventional technology that detects the amount of Doppler shift based on the amount of Doppler shift.

Furthermore, since the frequency of ultrasonic waves is as high as 20 KHz or more, and it is necessary to detect fluctuations in the period, advanced signal processing technology is required.

The present invention was made to solve such problems, and there is no risk of erroneously detecting the amount of Doppler shift of an ultrasound signal even when subjected to disturbances such as wind, and it is superior to conventional technology when detecting the amount of Doppler shift. It is an object of the present invention to provide a speed detection device whose signal processing is easier.

(Means for Solving the Problem) The speed detection device of the present invention directs a so-called pulsed ultrasonic signal, in which a plurality of ultrasonic waves are made into one pulse, from a moving object moving on a road surface toward the road surface. It is characterized by transmitting pulsed ultrasonic waves (G), detecting the reflected signal from the road surface, measuring the Doppler shift amount of the pulse in the detected reflected signal, and detecting the vehicle speed based on this Doppler shift amount. That is.

That is, the speed detection device of the present invention is a speed detection device that is installed on a moving body moving on a road surface and detects the ground speed of the moving body, in which a continuous wave electric signal with a relatively short period is relatively long. a signal generating means for generating an on-off continuous wave signal of a predetermined period, which is turned on and off in a period; and an ultrasonic transmitting means for applying the on-off continuous wave signal and transmitting an on-off ultrasonic signal according to the on-off continuous wave signal. , an ultrasonic receiving means for receiving a reflected signal from a road surface of the transmitted on-off ultrasonic signal, a detecting means for detecting an on-off period of the received reflected signal, and an on-off period detected by the detecting means. The present invention is characterized by comprising speed calculation means for calculating the ground speed of the moving object based on the difference between the on-off period and the on-off period of the on-off continuous wave signal.

(Function) According to the above configuration, instead of detecting the amount of Doppler shift for each wave of ultrasound reflected from the road surface, it is possible to detect the amount of Doppler shift of a pulse consisting of a group of multiple ultrasound waves. Therefore, even if the ultrasonic signal undergoes intensity fluctuations due to disturbances such as wind, the possibility that one entire pulse consisting of a plurality of waves will undergo intensity fluctuations is extremely low, and therefore the risk of such detection is extremely small. Furthermore, since the period of the pulse is larger than the period of the six ultrasonic waves, the signal processing for detecting the amount of Doppler shift does not require as advanced a technique as the prior art.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing a speed detection device according to an embodiment of the present invention. In this device, first, an oscillator 1 outputs a continuous wave electrical signal with a frequency of 200 KHz, and a modulator 2 modulates the electrical signal into an on-off continuous wave signal (hereinafter referred to as a pulsed signal) in which one period is a plurality of periods of the electrical signal. Then, an on-off ultrasonic signal is transmitted from the ultrasonic transmitter 3 toward the road surface 4 in accordance with this pulse ratio multiple. Next, a diffused reflection signal of this on-off ultrasonic signal from the road surface 4 is received by the ultrasonic reception sensor 5 and converted into an intermittent electric signal (hereinafter referred to as a reflected pulsed signal) according to this diffused reflection signal, This reflected pulsed signal is amplified by an amplifier 6, and further waveform-shaped by a waveform shaping section 7 into a rectangular pulse signal. Thereafter, this pulse signal is input to the counter section 8 to measure its pulse period, and from this measurement value, the Doppler shift amount of the pulse period is detected in the vehicle speed calculation section 9, and the vehicle speed is further calculated based on this Doppler shift amount. . Note that the ultrasonic transmitter 3 and the ultrasonic receiving sensor 5 are, for example, MA20.
This is an ultrasonic transducer made of 0 AI (manufactured by Zaiyo Seisakusho), which is installed in parallel to the balance tire storage area of the vehicle body, for example, so that the angle of incidence θ on the road surface 4 can be varied in the range of 0 to 90''. configured.

Further, the distance between the transmitter 3 and the receiving sensor 5 from the road surface 4 is set to, for example, 24°.

Next, the operation of the apparatus of the above embodiment will be explained with reference to FIG. A continuous wave signal of 2°0 KHz input from the oscillator 1 to the modulator 2 is subjected to so-called pulse modulation in the modulator 2. That is, this pulse modulation consists of a period tl (on signal period) in which the continuous wave signal is output and a period 1 m (off signal wj) in t2 in which the continuous wave signal is not output.
On-off continuous wave signal (
pulsed signal). The above period tl,
For example, t2 is set to 0.5 m5ec in both cases. In response to this pulsed signal, the ultrasonic transmitter 3 has a high sound pressure level for a period of tl, and this portion is referred to as a pulse portion. The on-off ultrasonic signal outputs an on-off ultrasonic signal in which the sound pressure level is approximately 0 during the subsequent period <t2 (this portion is referred to as a non-pulse portion; the same applies hereinafter). The on-off period T of this on-off ultrasonic signal is the period t1 and the period t2.
It is a combination of The on-off ultrasonic signal transmitted towards the road surface 4 in this way is diffusely reflected on the road surface 4 and then received by the receiving sensor 5.
This on-off ultrasonic signal when received is affected by the Doppler effect, and the period 11S1 of the pulse portion is t1',
The period of the non-pulse portion becomes t2', and the on/off period becomes T-Δt. That is, the amount of Doppler shift is Δt. The on-off ultrasonic signal received by the ultrasonic receiving sensor 5 is converted into a reflected pulsed signal having a vibration intensity corresponding to the sound pressure level, and the waveform shaping unit 7 converts the on-off ultrasonic signal into a reflected pulsed signal having the same pulse width as the on-signal period. Converted to a rectangular pulse signal. The counter section 8 measures the pulse period T-Δt of the rectangular pulse signal. In this example, T-+1■
Since it is S, the pulse period is 1 S - Δt. In this case, the frequency of the pulse signal is about IKHz, and signal processing of high-frequency signals is not required, so the configuration of the signal processing circuit becomes simple 1i. Further, the vehicle speed calculating section 9 calculates the vehicle speed based on the equation (f is the pulse frequency of the ultrasonic wave received by the receiving sensor 5) that gives the relationship between the Doppler shift amount Δt and the vehicle speed.

Note that the speed detection device of the present invention is not limited to the configuration described above, and various other configuration changes are possible. Furthermore, the period T of the pulsed signal formed by pulse modulation and the ratio of the on-signal period t1 to the off-signal period t2 are not limited to those of the above embodiment, but appropriate values may be selected depending on the situation. be able to. In general, the detection accuracy improves as the period T is shorter, but considering the attenuation characteristics of the ultrasonic receiving sensor 5, the on-signal period t] and the off-signal period t2 each require about 0.5 IOs. It is desirable that the period T is 0.1 s or more.

(Effects of the Invention) As explained above, according to the speed detection device of the present invention, an on-off ultrasonic signal in which a wave group consisting of a plurality of waves is used as one pulse part is used, and based on the Doppler shift amount of this pulse part, Since the vehicle speed is calculated based on the amount of Doppler shift of a single wave of ultrasonic waves, compared to conventional technology that calculates the vehicle speed based on the amount of Doppler shift of a single wave of ultrasonic waves, it is much less affected by external disturbances such as wind.
< It is possible to perform speed detection with high r- and j-axis characteristics.

In addition, the period of the pulse part of the on-off ultrasonic signal is ultrasonic 6
Signal processing becomes easier when the Doppler shift amount is large compared to the period of the wave.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining the operation of a speed detection device according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of the embodiment device shown in FIG. 1.

Claims (1)

[Claims] A speed detection device that is installed on a moving body moving on a road surface and detects the ground speed of the moving body, in which a continuous wave electrical signal with a relatively short cycle is turned on and off in a relatively long cycle. a signal generating means for generating an on-off continuous wave signal with a predetermined period, an ultrasonic transmitting means for receiving the on-off continuous wave signal and transmitting an on-off ultrasonic signal corresponding to the on-off continuous wave signal; an ultrasonic receiving means for receiving a reflected signal of an on-off ultrasonic signal from a road surface; a detecting means for detecting an on-off period of the received reflected signal; and an on-off period detected by the detecting means and the on-off continuous wave. A speed detection device comprising speed calculation means for calculating the ground speed of the moving body based on the difference between the on-off period of the signal.