JPS5926912B2 - Dotsplus speed meter for vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speedometer for a vehicle or a moving object, and particularly to speedmaking using the microwave Doppler effect.

Traditionally, automobile speedometers have used a method of converting the number of rotations of the wheels into electrical signals and counting them to measure speed, but if the wheels slip, the correct speed will not be indicated.

Therefore, in order to accurately measure speed, it is being considered to attach a speedometer that uses the microwave Doppler effect.

However, when a Tonpura speed sensor is attached to a vehicle, it naturally measures the speed relative to the road surface, so the radiation waves are emitted diagonally at a certain angle.

By doing this, the speed of the vehicle can be measured, but Doppler waves due to the vertical movement of the vehicle will inevitably be mixed in, resulting in an error.

In order to put the Doppler speedometer into practical use, it is necessary to eliminate this drawback.

SUMMARY OF THE INVENTION An object of the present invention is to provide a Doppler speedometer that can detect the correct running speed even if the vehicle moves up and down.

According to the present invention, by providing mutually symmetrical transducers in the traveling direction and the opposite direction, and processing both Doppler signals using an electric circuit, the Doppler waves caused by vertical motion are canceled out and the correct traveling speed is measured. be able to.

This will be explained in detail below using the drawings.

Generally, the Doppler signal sD is expressed by equation (1) as shown below.

2■ 5D=ACO8(±-ω.

t) ・・・・・・・・・・・・ (1) Tatashi,
A: amplitude ■: relative speed of the moving object C: speed of light ω.

: When attempting to measure vehicle speed using a transmitted angular frequency Doppler signal, the antenna attached to the vehicle must be attached at a certain angle θ with respect to the ground.

This is clear from the fact that Doppler signals cannot be obtained in principle if the device is mounted vertically or horizontally to the ground.

Therefore, if the velocity component in the antenna axis direction that is proportional to the running speed ■1 is V'l, and the velocity component in the antenna axis direction that is proportional to the vertical motion speed v2 is Two frequencies are detected, and the second term becomes an error component.

However, A' and B' are amplitude coefficients.The present invention aims to reduce the word difference by removing the Doppler signal according to equation (6) above.

The figure shows an embodiment of the present invention, in which 1 is an oscillator, 2 is a distributor, 3 and 4 are directional couplers, 5 and 6 are circulators, 7 and 8 are mixers, 9 and 10 are phase shifters,
11 and 12 are antennas, 13 is the vehicle body, 14 is the road surface,
15 is mixer output terminal, ■1 is vehicle running speed, ■1'
is the component in the antenna axis direction of ■1, ■2 is the velocity in the vertical direction,
■2' is the antenna axis direction component of ■2, and θ is the mounting angle of the antenna.

The output signal from the oscillator 1 is divided into left and right equal parts by a distributor 2.

The right signal after being split passes through the directional coupler 3,
The signal passes through the circulator 5, is delayed by one phase by the phase shifter 9, and is radiated toward the road surface 14 by the antenna 11.

The output divided by the directional coupler 3 is applied to the mixer 7 as a local oscillator signal.

On the other hand, since the signal divided on the left side is also a symmetrical circuit as shown in the figure, it follows the same path on the right side, and most of the signal is not radiated to the road surface by the antenna 12, and is transmitted by the directional coupler 4. The shunted output is added to the mixer 8 as a local oscillator signal.

However, the difference with respect to the right side is that the output signal radiated from the antenna 12 is delayed by π/4 by the phase shifter 10 and that the radiation direction is exactly opposite.

Now, when the vehicle body 13 on which the above circuit is installed travels as shown in the figure at a speed of V1 and a vertical movement (■2) (the actual moving direction of the vehicle body 13 is the opposite direction to the arrow in ■1), the mounting angles of the antennas 11 and 12 will be Since .theta. is the same angle, the velocity components received by the antennas 11 and 12 are detected as vectors having the relationship shown in the drawing, i.e., 1' is detected as a vector in opposite directions, and 2' is detected as a vector in the same direction.

In this way, one of the reflected waves from the road surface is received by the antenna 11 and advanced by π/4 in phase by the phase shifter 9 and applied to the mixer 7, and the other is received by the antenna 12 and advanced by π/4 in phase by the phase shifter 10. Mixer 8 with delayed phase
added to.

Therefore, if we define the velocity component approaching the antenna as positive and the velocity component moving away from the antenna as negative, the phases of the local oscillation signals are the same for both, so the Doppler signal S obtained by mixers 7 and 8 is
D7 and Sn2 are expressed by the following formulas (3) and (4), respectively.
It is expressed by the formula.

When the signals SD7 and Sn2 are combined and taken out at the terminal 15, the second terms cancel each other out, and only the first term component is added and output.

That is, the component (2) due to vertical movement is removed, and a Doppler signal with only the traveling speed component (1) is obtained.

In addition, in the example, explanation was given using a ±π/4 phase shifter, but similar results can be obtained by inserting lines of 1/8 wavelength and 3/8 wavelength, respectively, instead of the phase shifter. is clear from the phase relationship.

As explained above, according to the present invention, it is possible to obtain a Doppler speedometer for a vehicle that is not adversely affected by vertical movement of the vehicle body and has extremely small errors.

[Brief explanation of drawings]

The figure shows an embodiment of the present invention, in which 1 is an oscillator, 2 is a distributor, 3 and 4 are directional couplers, 5 and 6 are circulators, 7 and 8 are mixers, 9 and 8 are phase shifters, 11
and 12 is an antenna, 13 is a vehicle body, 14 is a road surface, and 15
is the mixer output terminal, ■1 is the vehicle running speed, and vI' is ■
1 is the antenna axis direction component, V2 is the vertical velocity, ■2
' is the antenna axis direction component of ■2, and θ is the antenna installation angle.

Claims (1)

[Claims] 1. A first antenna provided with an angle of depression in the direction of travel of the vehicle, a second antenna provided symmetrically in the opposite direction of travel, and a distributor that equally distributes the output of the oscillation source. A first directional coupler that shunts a local signal from one output, a first mixer connected to it, a first circulator, and a wave received by the output of the first directional coupler and the first antenna. a first phase shifter that advances the phase of a circulator, a second phase shifter that delays the phase of the output of the second directional coupler and the wave received by the second antenna by π/4, and means for combining the outputs of the first and second mixers. A vehicle Dotsupura speedometer characterized by: