JP2000155003A - Distance gauge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure an absolute distance without any influence by an environmental change even in measurement of a long distance by freely rolling/sliding a short circuit conductor from the outside by means of a magnet for generating a short circuit in an optional position between parallel conductors. SOLUTION: In measurement of a height of a liquid level 5 in a container 36, for example, parallel conductors 34-1, 34-2 and a rotational short circuit conductor 17 are put inside a protection cover, and a permanent magnet 4 is fixed inside a float 31 constructed to move upward/downward according to the vertical movement of the liquid lever 5. When a liquid level moves upward/downward, the permanent magnet 4 moves upward/downward according to the vertical movement of the float 31, and consequently, the parallel conductors 34-1, 34-2 moved upward/downward are short- circuited with each other by the short circuit conductor 1. A high frequency pulse is impressed to the ends of the parallel conductors 34-1, 34-2 from an amplifier 1, and a time required for transmission of this pulse impressed and reflected by the short circuit part is measured. By multiplying the transmission time by a voltage propagation speed inside the conductor, a distance to impedance mismatching, that is, a height of the liquid lever 5 of the position of the float 31 can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the measurement of the position of a transport trolley in an automatic warehouse, the position measurement of a container carrier, the position measurement of an overhead traveling crane, the position detection of a cylinder rod, and a long-distance position such as a liquid level measuring device in a tank. Regarding measurement.

[0002]

2. Description of the Related Art Conventional long-distance position measurement includes measurement using reflection of a laser beam, a method of winding a wire around a reel having a built-in rotation detector, and converting the number of windings and the winding angle of the wire into a position. There has been a method in which a tachometer is fixed to a pinion, and the pinion is engaged with a rack to measure the number of rotations and the angle of the pinion and convert it into a distance.

[0003]

In a conventional distance measuring device, for example, in a radar measuring method, the measuring accuracy is affected by weather such as sunlight or rain, and in a measuring method using a wire and a roller, a winding per rotation is used. A change in the take-up radius or turbulent winding changes the amount of wire wound per revolution.In measurement using a rack and a pinion, the number of pinion rotations changes due to backlash etc., and an error occurs. Because of the repetition (incremental) of the same signal every time,
In order to return the measuring device after the power is turned off, it is necessary to adjust the origin, which is a problem in the field of factory automation.

[0004] The present invention provides a measuring instrument based on physical characteristics that can be obtained absolutely (not incrementally) even if the measurement distance is a long distance measurement, and that the measurement accuracy does not significantly decrease due to environmental changes such as rain or temperature. It is intended to provide.

[0005]

To achieve the above object, the distance measuring apparatus of the present invention focuses on the fact that the propagation speed of a voltage propagating through a conductor is stable with respect to changes in the external environment. Measure distance by measuring time.

[0006] The propagation speed of a voltage propagating through a conductor varies depending on the material of the conductor, but it is usually very high. In a conductor such as a copper wire, which transmits a voltage of 1 m in about 5 ns (nanoseconds), 0.05 ns for 1 cm resolution
A high-speed counter having the above resolution is required.

The present invention provides a distance measuring principle for performing distance measurement with high reproducibility, mechanical means for accurately determining a measured distance, and electric means for reliably measuring such a high-speed phenomenon.

[0008]

The parallel conductor (34) is regarded as having an equivalent distribution of equivalent inductance L, equivalent resistance R and equivalent capacitance C as shown in the equivalent circuit of FIG. 1, and when an applied pulse is applied to one end of the parallel conductor, the voltage becomes parallel. The light propagates through the conductor, reaches the opposite terminal, is reflected, and returns to the application section again.

The change in voltage due to the reflection differs depending on the connection state of the opposite terminal. If an impedance mismatch occurs due to a short circuit in FIG. 2 or a disconnection in FIG. appear.

A terminal to which an applied pulse is applied, when the reflected wave returned at the initial stage is a primary reflected wave (2) and the reflected wave whose voltage is reversed at the application section and re-reflected is a secondary reflected wave (23). The time required for the primary reflected wave to return is determined by the propagation speed of the voltage in the conductor, and is less affected by changes in the external environment.

In order to mechanically cause impedance mismatch from the outside, a mechanical part (short-circuiting conductor) which is short-circuited between the parallel conductors is disposed, and a permanent magnet (4) is provided outside the mechanical part. Is arranged, and by moving the permanent magnet, the short-circuit portion is moved.

To measure a very short time from the application of the pulse to the return of the primary reflected wave (2) with high resolution, a high-performance ultra-high-speed counter is required. Provide a high-speed analog circuit for high time measurement.

Further, since the rise time of the voltage itself upon application of the pulse affects the measurement of the measurement distance, a mechanical process for removing this error in advance is also provided.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The longest measurement distance (Lt) is 100 m and the propagation speed Ve of a voltage propagating through a conductor is 5 ns (nanosecond) / 1 m.
The configuration of the distance measuring instrument of the present invention is shown on the assumption that a parallel conductor that has not been specially processed is provided under the condition (1).

As shown in FIG. 4, T1 = Tt when measuring the entire length of the sensor is obtained by adding Ve to the reciprocating distance of Lt (2 × 100 m).
(5 ns / m), which is 1 μs (μ second). When the impedance of the parallel conductor is not particularly large and the secondary reflected wave of the reflected wave ends in a shorter time than Tt, Tp = Tt, and T = Tt + Tp = 2. × Tt.

Therefore, T is 2 × Tt, which is 2 μs (microsecond), and the applied frequency F of the applied pulse is 500 KH (kilohertz) obtained by dividing one second by T.

If there is no impedance mismatch in the middle, the primary reflected wave is generated after 1 μs, and the length of the conductor is 1 μm.
s divided by the voltage propagation velocity Ve (5 ns / m) to obtain 200
m, but since the transit time is round-trip, this is divided by 2 and 1
00 m is obtained as the distance between the parallel conductors.

If there is an impedance mismatching part at the position L1 on the way, a primary reflected wave is generated after T1, and half the value obtained by dividing the distance T1 to the impedance mismatching part by Ve is the measurement distance.

Next, in order to measure the time obtained in this way with high resolution, it is necessary to take out a minute change in time. Here, a method of replacing time with voltage is used, so this conversion method will be described.

The method for measuring the position of the mismatch generator shown in FIG. 5 will be described with reference to the electric block diagram of FIG.

The pulse having the frequency of F hertz formed by the pulse generator (27) is formed into a well-formed rectangular waveform by the waveform shaper (25), and then sent to the distributor (32) to be transmitted to the parallel conductor (3).
Used for pulse (3) applied to 4).

The reflected wave returned from the parallel conductor (34) is sent to a pulse amplifier (27) via a distributor (32), and this signal and a signal obtained from a reference voltage generator are compared by a comparator (8). The output of the reference voltage is stopped at the instant when the voltages match, and the time T1 during which the reference voltage was output is T1.
Divided by the reference period T to calculate the average voltage (33)
The average voltage (33) is proportional to the time from when the applied pulse is applied to the time when the voltage propagation reaches the impedance mismatch generator (30), where it is reflected and returned. This makes it possible to measure the distance from the pulse applying unit to the impedance mismatch generator placed in the middle of the parallel conductor (34).

Similarly, as shown in FIG. 6, the total length of the sensor cable (13) is LM, the distance corresponding to the loss time until the voltage rises is the approach distance, this approach distance is L0, and the sensor cable (13) terminal is The distance to the impedance mismatch generator (30) is L1, the reference voltage is a threshold (9) E0, and the sawtooth wave generator generates a sawtooth wave (24) voltage at the same time as applying an applied pulse. ), When the primary reflected wave (2) E1 exceeds the threshold value (9) E0, this is used as a trigger to stop and save the boosting of the sawtooth wave, and measure this voltage to measure the impedance from the pulse application terminal of the sensor cable. Measure the distance to the generator.

Here, as a method of generating the impedance mismatch, a method of short-circuiting between the parallel conductors (34) using a resistance change as shown in FIG. 3 is used.

FIGS. 8 and 9 show examples of mechanical means for freely generating a short circuit between parallel conductors from the outside.

In FIG. 8A, two parallel conductors are run inside the cover B, and a sphere of a magnetic metal such as iron or Ni is put therein.
An example is shown in which a cover A containing a permanent magnet (4) that freely slides outside is provided, and when the cover A slides on the cover B, the internal magnetic metal also rolls and the short-circuit portion moves.

Similarly, FIG. 8B shows a cover A containing a short-circuited cylindrical magnetic metal that freely moves in the cover B and a permanent magnet (4) that slides freely outside the cover B. When the cover A slides on the cover B, the internal magnetic metal rolls and the short-circuit portion on the parallel conductor moves.

In FIG. 8C, two parallel conductors formed so as to have a space inside are arranged, and a magnetic metal is built therein.
An example in which the outer circumference of a parallel conductor is covered with an insulator, and a slider with a built-in permanent magnet is arranged outside the slider, and when the slider slides, the short-circuiting magnetic metal in the parallel conductor is attracted, causing a short circuit between the parallel conductors. Show.

In FIG. 9, in order to measure the liquid surface height in the container, a protective cover (6) is inserted vertically into the container, and a parallel conducting wire (34) and a short-circuiting magnetic metal capable of rolling are inserted therein.
A float (31) is formed so as to slide on the protective cover, and a permanent magnet (4) is fixed inside the float, so that the float moves up and down above and below the liquid surface.

Here, when the liquid level goes up and down, the permanent magnet goes up and down in accordance with the up and down of the float, and the magnetic metal in the conductor protection cover goes up and down to short-circuit between the parallel conductors.

Here, the parallel conductor (34) from the amplifier (1)
A high-frequency rectangular pulse is applied to the terminal, and the voltage propagation in the conductor is reflected at the short-circuit portion, and the time from when the applied pulse (2) returns to the application end immediately after the application of the applied pulse is measured. By multiplying the propagation time by the voltage propagation speed in the conductor, the distance from the application position of the parallel conductor end to the impedance mismatch generator (2) can be measured, so that the float position can be measured, and as a result, the liquid level can be measured. Can be measured.

In FIG. 10, a cylindrical hole is formed in the rod and piston to measure the position of the cylinder rod.
A protective cover (6) fixed to the cylinder head is inserted in parallel with the cylindrical hole, and a parallel conducting wire (34) is set in the protective cover.
And a magnetic metal for short-circuiting that can be rolled in. A gap is provided between the protective cover and the cylindrical hole in the rod, and a permanent magnet (4) is fixed to the piston end on the cylinder head cover side, and the rod expands and contracts. So that the permanent magnet moves.

Here, when the cylinder rod expands and contracts, the permanent magnet moves, and the magnetic metal in the conductor protection cover moves to short-circuit the parallel conductors.

Here, the parallel conductor (34) from the amplifier (1)
A high-frequency rectangular pulse is applied to the terminal, and the voltage propagation in the conductor is reflected at the short-circuit portion, and the time from when the applied pulse (2) returns to the application end immediately after the application of the applied pulse is measured. By multiplying the transmission time by the voltage propagation speed in the conductor, the distance from the application position of the parallel conductor end to the short circuit can be measured, so that the cylinder rod position is known.

[0035]

A radar is a long-distance measuring device using electromagnetic waves, but the present invention measures a distance using reflection in a closed space such as a parallel conductor, not in an open space like a radar. Therefore, it is possible to freely bend the parallel conductor (34). Moreover, since the propagation speed of the voltage in the parallel conductor is used as a reference for measurement, there is little disturbance due to disturbance, and the propagation speed of the voltage is known. Absolute position measurement (absolute) is possible because it is a conductor.

There is a distance measuring device utilizing the reflection of ultrasonic waves, but the measurement is based on the speed of sound in the air.
In addition to being easily affected by temperature, it is not suitable for measurement of a high-speed moving object due to a low propagation speed.

Further, since time can be converted into voltage without using a high-speed counter, ultra-high-speed processing of short distances, that is, distance measurement becomes possible, and even if a flexible conductor is used, even a shape having a bend or curvature can be obtained. Because distance measurement is possible, distance measurement for new factory automation applications that was not available before has become possible.

[Brief description of the drawings]

Fig. 1 Equivalent circuit of parallel conductors assumed to be in equal distribution

FIG. 2 Mismatch state: equivalent circuit at short circuit

FIG. 3 is a schematic diagram of a state in which a mismatch has occurred;

FIG. 4 shows the shape of the reflected wave and the position of the mismatch generator.

FIG. 5: Mismatch generator position and average voltage

FIG. 6 is a detection distance output method using a sawtooth wave.

FIG. 7 is a block diagram of a distance detector.

FIG. 8 Short-circuit method

FIG. 9: Measurement of liquid surface height by liquid level gauge

FIG. 10 is a cylinder rod position detector

[Explanation of symbols]

 Reference Signs List 1 amplifier 2 primary reflected wave 3 applied pulse 4 permanent magnet 5 liquid surface 6 cover or protective cover 7 reference voltage generator 8 comparator 9 threshold 10 approaching distance 11 cylinder tube 12 slider 13 sensor cable 14 measuring distance 15 disconnection 16 short circuit 17 Short-circuit conductor 18 Low-pass filter 19 Equivalent inductance 20 Equivalent resistance 21 Equivalent capacitance 22 Trigger 23 Secondary reflected wave 24 Sawtooth wave 25 Waveform shaper 26 Pulse amplifier 27 Pulse generator 28 Piston 29 Mismatch 30 Mismatch generator 31 Float 32 Distributor 33 Average voltage 34 Parallel conductor 34-1 Parallel conductor A 34-2 Parallel conductor B 37 Port 38 Container 39 Rod or cylinder rod

Claims (3)

[Claims] A parallel conductor (3) whose propagation speed of a voltage in a conductor is known and whose impedance is considered to be in a uniform distribution state.
In 4), at any desired position of the parallel conductor (34),
It has an impedance mismatch generator (30) for short-circuiting the short-circuit conductor (17) to the parallel conductor (34) to cause impedance mismatch, and applies a high-frequency rectangular pulse to the terminal of the parallel conductor (34) to apply a voltage in the conductor. The propagation is reflected by the impedance mismatch generator (30), and the primary reflected wave (2) is required for reciprocation from immediately after the application of the applied pulse (3) to returning to the application end (one end of the parallel conductor). By measuring the time and multiplying the transmission time by the voltage propagation speed in the parallel conductor, the distance from the application position of the end of the parallel conductor (34) to the position where the impedance mismatch generator (30) is installed is measured. In this distance measuring device, the short-circuiting conductor is made of a magnetic metal, and the short-circuiting conductor (17) is freely rolled or slid from the outside with a permanent magnet (4) or an electromagnet to be parallel-conductive. Any by generating a short circuit at the position of,
A distance measuring device configured to perform position measurement. 2. The distance measuring device according to claim 1, wherein the sensor cable portion (13) covered by the protective cover and the freely movable magnetic metal are vertically installed in the liquid container (36) and protected on the outer periphery of the protective cover. A float (31) having a lower specific gravity than the liquid is installed so as to slide on the cover, and a permanent magnet (4) is inserted into this float. When the liquid surface moves up and down, the float (31) also moves up and down, and this movement The liquid metal configured to measure the liquid surface height by moving the magnetic metal for short circuit (17) in the protective cover up and down in accordance with the time, and short-circuiting the parallel conductors at an arbitrary position corresponding to the liquid surface height. Surface height measuring instrument. 3. A cylindrical hole is formed in the center of the cylinder rod (37) and the piston (28) of the cylinder, and a protective cover fixed to the cylinder head cover side is inserted into the hole in parallel with the cylinder rod (37). In this protective cover, two parallel conductors (34) and a freely movable short-circuiting magnetic metal (17) are placed, and the parallel conductors are connected to an amplifier to protect the permanent magnet (4) on the end face of the piston on the cylinder head side. When the cylinder rod (37) expands and contracts based on the distance measuring principle according to claim 1, the piston and the permanent magnet fixed to the cylinder move and the piston and the permanent magnet move to prevent the cover from coming into contact with the cover. The short-circuiting magnetic metal (17) is attracted to the permanent magnet, and moves in accordance with the movement of the permanent magnet (4) to cause a short-circuit of the parallel conductors, thereby causing an impedance between the parallel conductors. -A cylinder rod position detector that generates a dance mismatch and can measure the cylinder rod position.