JPH0411188Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a ground penetrating radar for detecting underground objects or geology, and particularly to a towing vehicle equipped with an antenna section thereof.

[Conventional technology]

The above-mentioned ground-penetrating radar uses a towing vehicle equipped with the antenna section to run on the ground surface and collect measurement results.
It is displayed on a CRT or recording paper using a B-scope display, with the vertical axis representing the intensity of reflected radio waves in the direction of underground depth, and the horizontal axis representing travel distance (corresponding to the exploration point). This display method requires accurate measurement of the amount of rotation of the wheels, which is used as a guide for travel distance. Usually, a so-called shaft encoder is attached to the axle, and an electrical signal proportional to the amount of rotation is extracted using a cable or the like.

[Problem that the invention attempts to solve]

The towing vehicle has a trolley-like housing 10 as shown in FIG.
Fixed wheels 11A on both sides, casters 11B on the front
It can move on the ground by changing the angle freely by changing the direction of the handle. The arrangement of the antenna head is as shown in FIG.
3, and the antenna 12 is arranged on an insulating plate in contact with the surface of the opening 13A. The antenna 12 emits radio waves in the direction of the arrow and receives the reflected waves. The transmitter/receiver 15 is arranged on the outside of the back surface of the shield housing 13 facing the opening 13A.
Receiver output and the like are taken out from the center via a cable via a connector 16.

By the way, the travel distance of a towing vehicle can be determined by attaching a shaft encoder to the axle and measuring the rotation amount of the wheels. The shaft encoder can be mounted on either the fixed wheels 11A or the casters 11B. In order to accurately determine the travel distance, it is best to measure it at the position of the caster 11B located at the center of the front of the towing vehicle. But caster 1
1B has a structure in which the wheels can be rotated at any angle, so incorporating the shaft encoder becomes mechanically complicated. Furthermore, when pushing the handle forward with both hands, it is necessary to operate carefully so as not to accidentally change the direction of the caster 11B. On the other hand, since the fixed wheels 11A are fixedly supported and move only in one direction, the shaft encoder can be easily attached to the fixed wheels 11A. However, if the tow vehicle is not moving in a straight line, there is a distance between the attached wheels and the center of the tow vehicle, which makes the measurement of the distance traveled inaccurate.

The above is a mechanical problem, but due to the structure of the towing vehicle, the connector 16 taken out to the outside is located in the center and is far away from the fixed wheels 11A and caster 11B, and the input/output wire connecting the shaft encoder and the connector 16 is prone to electrical noise. I have a problem picking up the .

Figure 4 shows a state in which a conventional shaft encoder is attached to a fixed wheel 11A.A shaft encoder, for example, includes a rotary ring with a comb-shaped peripheral edge attached to the shaft of the fixed wheel 11A, and a light emitting part and a light receiving part are combined. The normal type. The supply of power to the shaft encoder and the transmission of photoelectrically converted electrical signals are all carried out through the input/output line 33'.
Due to the structure of the towing vehicle, the input/output wire 33' is connected to the shield housing 1 from the connector 16 at the upper center of the housing 10.
3 to the shaft encoder of the fixed wheel 11A. The housing 10 is made of plastic to reduce weight, and the lower surface is open to radio waves, so the input/output line 33' is exposed to radio waves reflected from underground as shown in the figure. In this way, the input/output line 33' connected to the shaft encoder picks up noise, and the length of the conductor wire is about the same as the wavelength included in the radar pulse used, so the magnitude of the noise is different from the radio waves received by the antenna. This becomes a non-negligible level and causes a measurement error.

Although there are electrical and mechanical problems as mentioned above, the purpose of this invention is to install the shaft encoder on a fixed wheel because it is easy to install and there is less error in distance measurement due to driving errors. An object of the present invention is to provide a towing vehicle equipped with an underground exploration radar that is not subject to damage.

[Means for solving problems]

A perfect way to eliminate the effects of electrical noise is to use optical transmission instead of electrical signal transmission for the input/output lines, but conventional commercially available shaft encoders cannot be used and special design is required, making measurement difficult. The system is complex. The present invention uses a conventional shaft encoder, but attempts to significantly reduce electrical noise by modifying the input/output lines.

As a means for this purpose, the input/output line from the shaft encoder provided on the wheel to the connector on the top surface of the towing vehicle uses a conducting wire with a plurality of resistors inserted at intervals. The interval is at least 1/4λ of the wavelength λ included in the radar pulse.

[Effect]

The frequency component of the transmission pulse of the ground penetrating radar is
The commonly used pulse width ranges from 50MHz to 600MHz, and the wavelength ranges from 6m to 0.5m. When the input/output line is routed from the wheel to the connector, the dimensions are of the same order as the short wavelength component, so it resonates with the radio waves reflected from underground. In this invention, the input/output line is not a single conductor wire, but is divided into sections by multiple resistors, and the conductor section is made much smaller than the above wavelength to reduce the induced voltage. At the same time, noise power is consumed in each section using a resistor. Therefore, even if the input/output line reaches the noise wavelength, the noise will not be transmitted from the connector to the external signal processing system.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Fig. 2 shows a state in which a conventional optical encoder is attached to a fixed wheel (hereinafter simply referred to as a wheel) 11A. 31 and a light receiving section 32 are combined.

Light emitting section 31 and light receiving section 32 of shaft encoder
The power supply to and the transmission of photoelectrically converted electric signals are all performed by the input/output line 33 shown in the "Means for Solving the Problems" of the present invention. FIG. 1 shows a schematic diagram of this input/output line 33. In this embodiment, the conductors of the light emitting unit 31 and the light receiving unit 32 enter the housing 10 (P in FIG.
The wires are divided into approximately 10cm intervals from l ₁ to l _o from point ) to connector 16, and the resistance in each section is assumed to be approximately the same, and the total resistance of each line, e.g.
R ₁₁ + R ₁₂ +...R1n is set to 100Ω. Each line has a bead-shaped tie yoke inserted from the final section l _o to the connector 16 (indicated by l _n in the figure, approximately 10 cm) to further block radio waves.

The lengths of l ₁ , l ₂ ... do not need to be strictly equally spaced. The wavelength included in the radar pulse is 6m~
Even if 0.5 m is used, it does not need to be exact, as long as it is at least 1/4λ or less of the maximum wavelength, since the energy component is small in high frequency components. Note that it is necessary to choose a resistor that is as small as possible.

[Effect of idea]

In detail, as explained above, according to the present invention, a conventional optical shaft encoder is attached to the fixed wheel of a towing vehicle, and even if the input/output line from the shaft encoder to the connector becomes long,
The influence of noise caused by reflected radio waves can be removed. It has the advantage of simply changing the input/output lines. However, even if you try to significantly change the exploration depth range by changing the pulse width of the ground-penetrating radar, there may be cases where it is impossible to follow the radar. If the number of sections is small and there is little margin, it may not be possible to completely prevent noise if the radar pulse is emitted with a larger amplitude than the specified pulse amplitude or if the reflected radio wave energy is abnormally large. Shorten the section length and increase the number of sections as much as possible.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the present invention, with the input and output lines taken out, Fig. 2 is a sectional view showing the shaft encoder installation part, Fig. 3 is an external perspective view of the towing vehicle, and Fig. 4 is an explanatory diagram showing the input/output line part. The figure is a sectional view of the towing vehicle. 10... Housing, 11A... (fixed) wheels, 11
B...caster, 12...antenna, 13...shield casing, 13A...opening of shield casing,
15...transmitter/receiver, 16...connector, 30...
Rotating ring, 31... Light emitting section, 32... Light receiving section,
33, 33'...Input/output line.

Claims (1)

[Scope of claim for utility model registration] In a towing vehicle equipped with a shield casing containing a built-in antenna head that radiates radio waves from an opening into the ground, from the shaft encoder installed on the wheel to the connector on the top of the towing vehicle. An underground device characterized in that the input/output line is formed by inserting a plurality of resistors into a conducting wire at intervals, and the intervals are at least 1/4λ or less of the wavelength λ included in the radar pulse. Towing vehicle equipped with exploration radar.