JPH09257922A - Radio-wave ground speed meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ground speed meter which is not affected by vibration of a moving vehicle or fluctuation of attitude after being mounted and can detect a moving speed of a vehicle with stability and high accuracy. SOLUTION: A device for detecting a moving speed of a moving body with an electromagnetic wave is provided with two transmission antennas 5a and 5b fixed to the moving body with an angular difference. These transmission antennas 5a and 5b alternately emit an electromagnetic wave in the time-division manner, a reflected wave reflected by the surface of a railway or a road 7 is received by these transmission antennas 5a and 5b, and a speed of the moving body is detected by a signal processor 4 based on a frequency of the reflected wave and the angular difference between these transmission antennas 5a and 5b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and system for measuring the moving speed of a moving body such as a train or an automobile.

[0002]

2. Description of the Related Art Conventionally, as a sensor for always accurately measuring the moving speed of a moving vehicle, a radio wave ground speed sensor constructed as shown in the block diagram of FIG. 2 is attached to the floor or side of the moving vehicle. A radio wave type ground speed sensor for measuring the ground speed is known.

That is, in FIG. 2, a casing 1 of a radio wave ground speed sensor is mounted under the floor of the vehicle. An oscillator 2, a circulator 3, and a signal processor 4, which generate electromagnetic waves, are installed inside the housing 1, and a transmitting / receiving antenna 5 is installed in the housing 1. The oscillator 2 is connected to the transmitting / receiving antenna 5 via the circulator 3. The circulator 3 is also connected to the signal processor 4.

The electromagnetic wave sent from the oscillator 2 is transmitted to the transmission / reception antenna 5 through the circulator 3, and is radiated obliquely from the transmission / reception antenna 5 toward the road surface or the line 7 as indicated by an arrow. The electromagnetic waves applied to the road surface 7 and the like are scattered, and a part of them is received by the transmitting / receiving antenna 5. At this time, if the vehicle is moving at a certain speed,
The signal of the scattered electromagnetic wave that has been frequency-shifted by the Doppler effect is guided to the signal processor 4 by the circulator 3.

In the signal processor 4, as shown in the spectrum of FIG. 3, a signal frequency-shifted from the electromagnetic wave of frequency F to the electromagnetic wave of frequency f by the Doppler effect corresponding to the traveling speed of the vehicle is signal-processed by the signal processor 4. Will be detected. Here, the frequency shifted by the Doppler effect is determined by the ground speed of the vehicle and the irradiation angle of electromagnetic waves.
In the signal processor 4, the irradiation frequency of the electromagnetic wave with respect to the reception frequency and the preset moving direction is θ, the wavelength of the transmitted electromagnetic wave is λ (m), and the frequency of the received electromagnetic wave is f (Hz). When the moving speed of is V (m / s), it is expressed by the following equation.

[0006]

[Equation 1]

From the above equation (1), the received frequency f
Is known, the moving speed V of the moving vehicle can be obtained.

[0008]

By the way, in the above-mentioned conventional radio wave type ground speed sensor, vibration occurs when the vehicle is moving, and the irradiation angle of the electromagnetic wave with respect to the moving direction is changed. Therefore, the frequency of the electromagnetic wave that shifts due to the Doppler effect changes depending on the irradiation angle of the electromagnetic wave with respect to the moving direction of the vehicle, resulting in a large measurement error. In addition, the error becomes large even when the vehicle, which is a moving body, has an angle different from that when the radio wave ground speed sensor is attached to the ground due to the mounting of a heavy load or the tire air pressure imbalance.

The present invention has been made in view of the above circumstances, and solves the above-mentioned drawbacks of the prior art, and is stable and highly accurate without being affected by the vibration of the moving vehicle or the change in the posture after mounting. An object is to provide a radio wave type ground speed sensor capable of detecting the moving speed of a vehicle.

[0010]

SUMMARY OF THE INVENTION The present invention is a device for detecting the moving speed of a moving body by means of an electromagnetic wave, which has two transmitting and receiving antennas fixed to the moving body with an angular difference, and the two transmitting and receiving antennas Emitting electromagnetic waves alternately in a divided manner, the reflected wave reflected on the surface of the track or road is received by the transmitting and receiving antenna, and the speed of the moving body is detected by the signal processor from the frequency difference of the reflected wave and the angle difference between the transmitting and receiving antenna. It is a radio wave type ground speed sensor.

Therefore, this radio wave type ground speed sensor is
Two transmitting and receiving antennas that are fixed to the moving vehicle with an angle difference and alternately radiate electromagnetic waves in a time division manner to receive the reflected waves reflected on the surface of the road or track, the frequency of the reflected waves and the angle of the transmitting and receiving antennas. It is composed of a signal processor that calculates the speed of the moving body from the difference, and it is possible to detect the moving speed of the vehicle stably and with high accuracy without being affected by the vibration of the moving vehicle and the change in the posture after the mounting. Since the two transmitting / receiving antennas are fixed to each other with a constant angular difference, the angular difference between the two transmitting / receiving antennas does not change due to the vibration of the moving vehicle or the change in posture after the transmitting / receiving antennas are attached. Therefore, it is possible to greatly improve the stability and high accuracy of speed detection.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of a radio wave type ground speed sensor of the present invention.
That is, the radio wave ground speed sensor is attached together with the housing 1 under the floor of the vehicle. An oscillator 2, which generates electromagnetic waves, circulators 3a and 3b, a signal processor 4, and a switch circuit 6 are installed in the housing 1. Further, two transmitting / receiving antennas 5a and 5b are attached to the housing 1 with an angle difference. The oscillator 2 and the transmitting / receiving antenna 5a are connected via the switch circuit 6 and the circulator 3a, and the oscillator 2 and the transmitting / receiving antenna 5b are connected via the switch circuit 6 and the circulator 3b. Those circulators 3a,
3b are also connected to the signal processor 4, respectively.

The electromagnetic wave emitted from the oscillator 2 is transmitted to the switch circuit 6 and transmitted to the transmitting / receiving antennas 5a and 5b through the circulators 3a and 3b. The switch circuit 6 functions to alternately transmit signals to the transmitting / receiving antennas 5a and 5b in a time division manner, and the switching circuit 6 time-divisionally directs the transmitting / receiving antennas 5a and 5b toward the road surface or the line 7 as shown by arrows. Irradiate diagonally. The electromagnetic waves radiated on the road surface or the line 7 are scattered, and some of them are received by the transmitting / receiving antennas 5a and 5b. At this time, if the vehicle is moving at a certain speed, the scattered waves that have undergone the frequency shift of the electromagnetic waves due to the Doppler effect will be received by the respective transmitting / receiving antennas 5a and 5b.

The received signals thus obtained are guided to the signal processor 4 by the circulators 3a and 3b, respectively. Electromagnetic waves are transmitted from the transmission / reception antennas 5a and 5b in a time division manner, so that the received electromagnetic waves are also time division. Therefore, the signal processor 4 can recognize which transmission / reception antenna of the two transmission / reception antennas 5a and 5b is the reception signal. The signal processor 4 includes a transmission / reception antenna 5a and a transmission / reception antenna 5b which are input in advance with the frequency of the reception signal.
The moving speed of the vehicle is detected from the difference in angle.

Here, the wavelength of the electromagnetic wave transmitted is λ
(M), the frequency of the electromagnetic wave to be transmitted is F (Hz), the irradiation angle of the electromagnetic wave from the transmitting / receiving antenna 5a with respect to the speed direction is θa (°), and the transmitting / receiving antenna 5b with respect to the speed direction
The irradiation angle of the electromagnetic wave from the antenna is θb (°), the frequency of the electromagnetic wave received by the transmitting and receiving antenna 5a is fa (Hz), and the frequency of the electromagnetic wave received by the transmitting and receiving antenna 5b is fb (H
z), the moving speed V (m / s) of the vehicle can be expressed by the following equations (2) and (3).

[0016]

[Equation 2]

Here, the angle difference between the transmitting / receiving antenna 5a and the transmitting / receiving antenna 5b is Δθ, that is, (θb-θa) = Δ
When θ is set and θa and θb are deleted from the equations (2) and (3), the following equation is obtained.

[0018]

(Equation 3)

From the above equation (4), the moving speed of the moving vehicle can be obtained from the angle difference Δθ between the transmitting / receiving antenna 5a and the transmitting / receiving antenna 5b. At this time, a large value of less than 90 ° is suitable for the angle difference between the two transmitting and receiving antennas. The reason for this is that the speed V in the above formula (4) is 90 ° in angle difference.
This is because the closer the value becomes, the smaller the change in the value with respect to the change in the angle, the smaller the error in the angle difference due to mounting, and the smaller the error in the speed detection.

[0020]

As described above, according to the radio wave type ground speed sensor of the present invention, since the two transmitting and receiving antennas are fixed with an angle difference, the angle of the moving vehicle with respect to the ground due to mounting of a heavy object or the like. The angle difference between the two transmitting and receiving antennas does not change even if the value fluctuates or vibrates due to movement. Therefore, the moving speed of the vehicle can always be detected stably and with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a radio wave type ground speed sensor of the present invention,

FIG. 2 is a block diagram showing a configuration of a conventional radio wave type ground speed sensor,

FIG. 3 is a spectrum for explaining a state of Doppler shift of a signal measured by a conventional radio wave type ground speed sensor.

[Explanation of symbols]

 1 case 2 oscillator 3, 3a, 3b circulator 4 signal processor 5, 5a, 5b transmitting / receiving antenna 6 switch circuit 7 road surface or line

Claims (1)

[Claims] 1. An apparatus for detecting a moving speed of a moving body by means of an electromagnetic wave, comprising two transmitting and receiving antennas fixed to the moving body with an angular difference, and the electromagnetic waves are alternately emitted from the transmitting and receiving antennas in a time division manner. However, a radio wave type characterized in that the reflected wave reflected on the surface of a railroad or a road is received by the transmitting / receiving antenna, and the speed of the moving body is detected by a signal processor from the angular difference between the frequency of the reflected wave and the transmitting / receiving antenna. Ground speed sensor.