JPH03237381A - Ultrasonic doppler type ground speed indicator - Google Patents

Abstract

PURPOSE:To widen the detection range of a vehicle speed and to make a measurement accurate by dividing the speed area to be detected into two and regarding the reception frequency of one as a 1st resonance point and the reception frequency of the other as a 2nd resonance point. CONSTITUTION:An ultrasonic receiver 6 divides the speed range of a vehicle to be detected into two area. for example, 140 km/h is set as the border speed and a transmission frequency is controlled between 130 kHz (0km/h) and 110.9kHz (140km/h) according to the vehicle speed so that the reception fre quency is fixed at 130kHz (main resonance point F) in a speed are of 0 - 140km/h. Then a transmission frequency control circuit 14 performs control so that the reception frequency is selected and fixed at 140kHz (subordinate resonance point F') in a speed range of 140 - 250 km/h. Consequently, the narrow transmission band of 20kHz can be utilized effectively and the vehicle speed can accurately be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an ultrasonic Doppler ground speed meter that utilizes the Doppler effect of ultrasonic waves.

(Prior Art) As a conventional ultrasonic Doppler ground speed meter, there is one shown in FIG. 7, for example.

This figure shows a measurement circuit in a conventional ultrasonic Doppler ground speed meter disclosed in Japanese Patent Application Laid-Open No. 60-76678. In the figure, 21 is an oscillator, and 23 is an ultrasonic signal from the oscillator 21. 22 is a wave transmitter driven by the drive circuit 23; 26 is a road surface 25;
This is a receiver that receives reflected ultrasonic waves 24 that are diffusely reflected and returned from the ultrasonic waves.

The received ultrasonic signal received by the receiver 26 is transmitted to the preamplifier 27. Analog multiplier 28° low pass filter 29. After passing through a zero cross comparator 30 and a pulse counter 31, a vehicle speed calculation circuit 32 calculates the vehicle speed.

(Problem to be Solved by the Invention) However, in such a conventional vehicle-mounted ultrasonic Doppler ground speed meter, the frequency band of the receiving sensitivity of the receiver 26 that receives the ultrasonic signal 24 is limited. As shown in FIG. 8, the configuration is such that the bandwidth can only be expanded to about 20 KHz, and the more the bandwidth is expanded, the lower the reception sensitivity is.

That is, for example, if the detection speed range of the target vehicle is 0 to 250 Km/h, the corresponding frequency width for detection and reception is 120 KHz, the ultrasonic beam rQ
In the case of 45°, the frequency is approximately 34.7 KHz from the following equation (2).

V; ground speed f. ;Transmission frequency θ;Irradiation ff1C;Sonic speed Therefore, in the conventional ultrasonic Doppler type ground speed meter, the detection reception frequency width exceeds the reception sensitivity bandwidth of the receiver 6, so it is difficult to detect a wide range of targets. There was a problem in that it was impossible to obtain a high-level signal over a wide speed range, and as a result, the accuracy of ground speed detection deteriorated.

In addition, even in the ultrasonic Doppler type ground speed meter disclosed in Japanese Patent Application Laid-open No. 1-107320, that is, the above-mentioned ground speed meter that employs a method of keeping the frequency of the received Doppler signal constant, the transmitter generates a high transmitted sound pressure. Bandwidth is 20KHz
Therefore, the same problem as the above-mentioned conventional example occurs.

The present invention has been made in view of the above-mentioned problems, and has the following objects: 1. To provide an ultrasonic Doppler ground speed meter that can expand the detection range of vehicle speed and improve the level of the detection signal. shall be.

(Means for Solving the Problems) In order to solve the problems mentioned in item 2, the present invention is configured as shown in FIG. Ultrasonic signals are transmitted diagonally to detect ground speed.

The receiving means receives the ultrasonic signal reflected from the road surface and has at least a first resonance point and a second resonance point for the input ultrasonic signal.

The vehicle speed calculating means C calculates the vehicle speed according to the ground speed detection signal detected by the receiving means (-).

The vehicle speed determination child actor d determines the vehicle speed from the vehicle speed value calculated by the calculation means C, and also determines the vehicle speed from the vehicle speed value calculated by the calculation means C.
．． The second j (designates one of the resonant frequencies at which there are H swinging points.

The transmission frequency changing means e inputs and controls the frequency designated by the vehicle speed 't'lJ cutting means d as the transmission frequency to the transmitter a.

(Function) The ultrasonic Doppler ground speed meter according to the present invention uses an ultrasonic receiving means having a first J (swing point) and a second J (swing point), and detects two speed regions. By setting the reception frequency of one of them as the first resonance point and the reception frequency of the other as the second resonance point, the detection range of vehicle speed can be expanded and the level of the detection signal can be changed. By measuring vehicle speed more accurately;
can be made possible.

(Description of Embodiments) Hereinafter, one embodiment of the ultrasonic Doppler ground speed meter according to the present invention will be described based on the drawings.

FIG. 2 is a block diagram showing the basic circuit configuration of an ultrasonic Doppler ground speed meter to which the present invention is applied.

In FIG. 1, an oscillator 1 generates a signal at a transmission frequency determined by a transmission frequency control circuit (described later), a drive circuit 3 amplifies the signal, and the output is used to transmit a signal to a transmitter 2.
The transmitter 2 generates an ultrasonic signal 4 having the wavelength of the above signal, and radiates the ultrasonic signal 4 toward the road surface 5.

In the figure, the receiver 6 is mounted on a vehicle with a first J (oscillation point (hereinafter abbreviated as the main resonance point) F and a second resonance point (hereinafter abbreviated as the sub-resonance point) F'). This is a sealed structure ultrasonic receiver for on-board use, and its resonance frequency characteristics have reception sensitivity characteristics as shown in FIG.
Receives the reflected wave signal that is diffusely reflected.

The received signal received by this receiver 6 is amplified by a preamplifier 7 and sent to a multiplier 8, and the multiplier 8 multiplies the oscillation frequency of the oscillator 1 by the frequency of the received signal, which is expressed as -. Find the difference.

After the signal obtained by the multiplier 8 is passed through a low-pass filter 9 to remove defective noise, the Doppler signal component is shaped into a waveform by a zero-cross comparator 10, and its frequency is read by a pulse counter 11.

The frequency of the Doppler signal read by the pulse scouter 11 is converted into a vehicle speed value by a vehicle speed calculation circuit 12 which is a vehicle speed calculation means.

13 in the figure selects one of the receiving frequencies of the above-mentioned two-pole signal set in advance from the vehicle speed value calculated by the vehicle speed calculating circuit 12, and also selects the receiving frequency in the vehicle speed calculating circuit of the vehicle speed calculating circuit 12. This is a receiving frequency selection circuit that is a vehicle speed determining means that specifies parameters.

Further, 14 inputs to the oscillator 1 a transmission frequency control signal generated by the oscillator 1 from the vehicle speed value calculated by the vehicle speed calculation circuit 12 and the frequency value selected by the reception frequency selection circuit 13. - A transmission frequency control circuit that is a controlling transmission frequency changing means.

The sealed structure type ultrasonic receiver 6 has a main resonance point F and a sub JI as shown in FIG. 3 as resonance frequency characteristics.
In many cases, the swing point F' is set to h', and conventional (for example,
The fixed reception frequency type ground speed: 1 of Tokkyo'P 1-1073205) has a configuration in which the ultrasonic receiver uses only one of the two J1 center points described in 2. In the present invention, the configuration is such that the two resonance points described above are actively utilized.

Next, the present invention will be explained in detail.

In this example, the receiving frequency fixed to the ultrasonic receiver 6 is 130 KHz, the irradiation angle is 45', and the sound speed is 1248 km.
/h (temperature: 25° C.).

First, the ultrasonic receiver 6 divides the speed range of the vehicle to be detected into two regions.

Here, as an example, 140 km/h is the boundary speed, and based on the following formula (■), the two speed regions (a),
In (b), each transmission frequency is controlled.

V: Ground speed f,, (V); Transmission frequency θ
; irradiation angle C; at sound speed of 250 km/h) That is, (a) In the speed range from 0 to 140 km/h, the reception frequency is fixed at 130 KHz (main resonance point F) shown in Fig. 3; The transmission frequency changes from 130 KHz (at km/h) to 110.9 K depending on the vehicle speed.
Hz (1401 oa/h).

Next, (b) between the speed range of 140 to 250 km/h, after the reception frequency selection circuit 13 selects the reception frequency, the reception frequency is set to 140KHz as shown in FIG.
It is controlled by the transmission frequency control circuit 14 so that it is fixed (subverted) at (F-).

In other words, in this embodiment, the narrow transmission frequency band of 20 KHz shown in FIG. This means that it can be used effectively.

Furthermore, in this embodiment, the speed range of the vehicle to be detected can be expanded, but apart from this, the transmitted sound pressure characteristic has a narrower frequency band than the one shown in FIG. By using a higher transmitter 2, the Doppler signal level can be improved compared to conventional detection methods, although the detection speed range is slightly narrower than in this embodiment.

Furthermore, since a fixed reception frequency method is used as the Doppler signal detection method, the following effects are achieved.

That is, according to the reception frequency fixing method, the Doppler shift frequency Fd shown in FIG. 5 is obtained from the number of zero crosses of the signal output from the zero cross comparator 9 shown in FIG. includes various frequency components shown in the shaded area in FIG.

Therefore, as shown in FIG. 4, the narrower the bandwidth Fw of the Doppler signal detected, the more the extra frequency components other than the Doppler shift frequency Fd included in the signal shown in FIG. The difference between the pulse scout number (corresponding to the Doppler shift frequency) detected by the counter pulse 11 shown by and the true Doppler shift frequency Fd becomes smaller.

In other words, the smaller the value of the signal bandwidth Fw, the more accurate the detected vehicle speed becomes.

Furthermore, in the Doppler signal detection method that fixes the receiving frequency, it is possible to use an ultrasonic receiver 6 with a large resonance Q value as shown in FIG. It will have a bus filter function.

In contrast, in the conventional method of fixing the transmission frequency,
Since a broadband receiver 22 as shown in FIG. 8 is used, the filter function described above cannot be expected.

Therefore, as shown in FIG. 6, there is a large difference in the signal bandwidth fw in both of the above methods.

In this way, by adopting the reception frequency fixed method, the reception bandwidth fw can be narrowed, so that the accuracy of speed measurement of the vehicle can be improved.

(Effects of the Invention) As described above, the ultrasonic Doppler ground speed meter according to the present invention has #i! a sound wave receiving means, and a vehicle speed 1'11 that specifies one of the frequencies of the resonance points according to the detected vehicle speed.
Since the configuration includes a transmission frequency changing means for inputting and controlling the transmission frequency specified by the vehicle speed determining means to the transmitting means, it is possible to expand the detection range of the vehicle speed. In addition, it is possible to improve the detected signal level, which has the effect of accurately measuring the vehicle speed.

[Brief explanation of drawings]

Fig. 1 is a diagram corresponding to the claims of this invention, Fig. 2 is a block diagram showing the basic circuit configuration of an embodiment of an ultrasonic Doppler ground speed meter according to this invention, and Fig. 3 is an ultrasonic wave used in this invention. FIG. 4 is a frequency characteristic diagram of the transmitter, FIG. 4 is a frequency characteristic diagram of the receiver used in this invention, FIG. 5 is a characteristic diagram showing the bandwidth of the Doppler signal in the frequency space detected by this invention, and FIG. Fig. 6 is a characteristic diagram of a detected Doppler signal, Fig. 7 is an explanatory diagram showing a comparison of signal bandwidth fw between the present invention and a conventional example, and Fig. 8 is a basic circuit configuration of a conventional ultrasonic Doppler ground speed meter. The block diagram shown in FIG. 9 is a reception sensitivity characteristic diagram of an ultrasonic receiver used in a conventional example. 1... Oscillator 2... Transmitter 4... Ultrasonic wave 5... Road surface 6... Ultrasonic receiver (receiving means) ) 12... Vehicle speed calculation circuit (vehicle speed calculation means) 13... Reception frequency selection circuit (vehicle speed judgment means) 14... Transmission frequency control circuit (
Transmission frequency changing means) F... Main resonance point (first resonance point) F-... Sub-resonance point (second resonance point)

Claims (1)

[Claims] 1. Transmitting means for transmitting an ultrasonic signal for detecting ground speed in a diagonal direction at a predetermined angle with respect to the road surface in front of the vehicle; a receiving means having at least a first resonance point and a second resonance point with respect to the input ultrasonic signal; and calculating a vehicle speed according to a ground speed detection signal detected by the receiving means. a vehicle speed calculating means for determining the vehicle speed from the vehicle speed value calculated by the calculating means, and for specifying one of the resonance frequencies at which the first and second resonance points of the receiving means exist. An ultrasonic Doppler type ground speed comprising: vehicle speed determining means; and transmitting frequency changing means for inputting and controlling the frequency specified by the vehicle speed determining means as a transmitting frequency to the transmitting means. Total.