JPH0532556B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for detecting the position of an excavator underground in order to make the excavator excavate underground along an excavation target line. Regarding a detection device.

[Conventional technology]

When burying pipes, etc. underground without excavation using the small-diameter excavation method, etc., the excavator placed at the tip of the pipe must excavate underground along a predetermined excavation target line. . For this reason, it is necessary to detect the position of the excavator underground and correct it if the excavator deviates from the excavation target line. In this way, detecting the position of the excavator is an essential means when excavating underground to construct a tunnel or burying a sewer pipe or the like. Hereinafter, conventional position detection means will be explained with reference to the drawings.

FIG. 5 is a schematic diagram of the configuration of a conventional position detection device. In the figure, A indicates the ground surface, A' indicates underground, and T indicates the excavation target line. 1 is an AC power supply, and 2a and 2b are conductive wires. The conducting wires 2a and 2b are loop-shaped conducting wires arranged at equal intervals W (W=W ₁ =W ₂ ) from the excavation target line T, and are connected to each other on the side opposite to the power source 1. 3 is underground A' and the above excavation target line T
This is an excavator that excavates in the direction of arrow 4. 5a and 5b are magnetic field detectors arranged on both sides of the excavator 3. Note that X, Y, and Z indicate assumed coordinate axes.

Now, when a current is supplied to the conducting wires 2a and 2b by the power source 1, the magnetic field formed underground by this current will be Depth) varies as a function of y and distance x in the X-axis direction. Therefore, if the magnetic field is detected by the magnetic field detectors 5a and 5b, the position of the excavator 3 in the underground A' can be detected. When the magnetic field detectors 5a and 5b are constituted by loop coils, the output thereof is proportional to the temporal rate of change of the magnetic flux passing through the loop surface of the coil. Here, φ: Magnetic flux passing through the loop surface of the coil N: Number of turns of the coil G: Loop area of the coil B: Magnetic flux density passing through the loop surface of the coil ω: Frequency of the magnetic flux, then the output e of the loop coil is as follows. It is expressed by the formula.

e=dφ/dt=ω・N・G・B・cosωt……(1) Also, when current is supplied to the conductors 2a and 2b, the magnetic field H _x in the X-axis direction and the magnetic field H _y in the Y-axis direction are , the positions x and y of the excavator 3 are determined as shown in the figure, and are expressed by the following equation.

H _x = I/2π{y/(x-W ₁ ) ² +y ² -y/(x+W ₂ ) ²
+y ² } ...(2) H _y = I/2π{X-W ₁ /(x-W ₁ ) ² +y ² -X+W ₂ /(x
+W ₂ ) ² +y ² } ...(3) Furthermore, the relationship between the magnetic field H and the magnetic flux density B is as follows, where μ is the magnetic permeability of the material, B=μ·H ...(4). In this embodiment, the medium is soil, and the magnetic permeability of soil can be kept constant, with almost no difference from air.

From the above, the positions x and y of the excavator 3 can be calculated based on the outputs e of the magnetic field detectors 5a and 5b. Such means determine what kind of line (straight line or curve) the excavation target line T is.
Since the position of the excavator 3 in the underground A' can be continuously detected even when the excavator 3 is in the ground, the excavator 3 can be automatically controlled.

[Problem that the invention seeks to solve]

By the way, the excavator 3 is often made of iron-based members. Therefore, when a magnetic flux passes through this, an eddy current is generated, and due to its influence, the magnetic permeability μ in equation (4) above changes locally, and the output voltage e also changes accordingly. This makes it impossible to accurately detect the positions x and y. Conventionally, in order to solve such problems, a method has been adopted in which experiments are conducted for each position detection device of each excavator to determine the necessary correction coefficients. However, this work required a high degree of skill and required a lot of effort and time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a position detection device for an excavator that can solve the problems of the prior art described above and can accurately and easily detect the position without conducting any experiments.

[Means for solving problems]

In order to achieve the above object, the present invention provides a magnetic field detector in an excavation machine, lays a loop-shaped conductor along an excavation target line, and furthermore, a loop-shaped conductor is laid at a predetermined distance from the conductor. A magnetic field detector detects the magnetic field due to the current flowing through the conductive wire and the magnetic field due to the current flowing through the other conductive wire. Based on these detected values and the predetermined distance, a calculation device detects the excavator. It is characterized in that the position of is calculated.

[Effect]

A current is passed through one conductor wire, the magnetic field generated by this current is detected by a magnetic field detector, a current is also passed through other conductors, the magnetic field is detected in the same way, and these detected values and the magnetic field between each conductor wire are A predetermined calculation is performed based on the distance to detect the position of the excavator.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

FIG. 1 is a schematic diagram of the configuration of a position detection device according to the present invention. In the figure, parts that are the same as those shown in FIG. 5 are given the same reference numerals, and explanations thereof will be omitted. 20a, 20b
Similar to the conductors 2a and 2b shown in FIG. 5, the conductors 21a and 21b are loop-shaped conductors laid at equal intervals W with respect to the excavation target line T, and the conductors 21a and 21b are laid a predetermined distance S apart from the conductors 20a and 20b. 6 is a loop-shaped conducting wire connected to the power source 1 and each conducting wire 20a, 20b, 21
This is a changeover switch interposed between a and 21b. Although not shown, an arithmetic device that inputs the detection values of the magnetic field detectors 5a and 5b is installed at an appropriate location on the ground surface A or the like. In addition, magnetic field detectors 5a and 5b
A loop coil is used.

Next, the operation of this embodiment will be explained with reference to FIGS. 2a and 2b and FIG. 3. FIG. 2a is a sectional view taken along line a-a shown in FIG. 1, and the same parts as shown in FIG. 1 are given the same reference numerals. When the changeover switch 6 is switched to the conductors 20a and 20b,
A current is supplied to the conducting wires 20a and 20b, and a magnetic field as shown by the solid arrow 7 is formed in the underground A' by this current. The magnetic field detectors 5a and 5b detect only the magnetic field component in the X-axis direction in such a magnetic field.

Here, if the excavator 3 is made of non-magnetic or non-conductive material, the magnetic field (magnetic flux density)
The axial component _H
The magnetic field component H _x changes as it shifts in the axial direction. In this case, the deviation in the X-axis direction is the depth y or the distance
When it is smaller than 2W, a proportional relationship is established between the magnitude of the deviation and the magnetic field component H _x . Figure 2b
is a characteristic diagram showing this, in which the horizontal axis represents the deviation size x, and the vertical axis represents the magnetic flux density _Bx . The characteristics when current is supplied to the conductors 20a and 20b are shown by a straight line _B20 , the output of the magnetic field detector 5a is a value proportional to the magnetic flux density _B20a , and the output of the magnetic field detector 5b is a value proportional to the magnetic flux density _B20b . It will be a proportional value.

In the above state, when the changeover switch 6 is switched to supply current from the power supply 1 to the conductors 21a and 21b, the magnetic field pattern indicated by the arrow 7 in FIG. is also moved by a distance S, as shown by the dashed line _B21 in FIG. 2b. In this case, the outputs of the magnetic field detectors 5a and 5b have values proportional to the magnetic flux densities B _21a and B _21b , respectively.

By the way, as mentioned above, since the excavator 3 is often made of iron-based materials, the position where the X-axis direction component H _x of the magnetic field becomes zero due to the influence of eddy currents etc. is shown in Figure 2 a. The position will be shifted from the original position. This is shown in FIG. FIG. 3 is a sectional view similar to FIG. 2a, and each part is given the same reference numeral as in FIG. 2a. As shown in the figure, the magnetic field indicated by the arrow 7 is biased toward the excavator 3 in the vicinity of the excavator 3, and the position where the output of the magnetic field detector 5b becomes zero is the excavation target line T.
The position is shifted to the left from directly below. This shift is indicated by distance u. Conversely, the position where the output of the magnetic field detector 5a becomes zero is shifted to the right by a distance u.

Considering the above, the output of the magnetic field detector 5a when current is supplied to the conductors 20a and 20b
e _5a

Claims (1)

[Claims] 1. An excavator that excavates underground, a loop-shaped conductive wire placed along the excavation target line of this excavator, and a magnetic field detector that is placed on the excavator and detects a magnetic field due to the current supplied to the conductor. a position detection device for an excavator, comprising: at least one other loop-shaped conducting wire arranged at a predetermined distance from the conducting wire; and the conducting wire and the other conducting wire detected by the magnetic field detector. 1. A position detection device for an excavator, comprising: a calculation device that calculates the position of the excavator based on each detected value of a magnetic field caused by a current flowing through a conducting wire and the predetermined distance.