JPH0530202B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a position detector using the magnetostrictive effect of a ferromagnetic material, and in particular to a position detector suitable for detecting the relative position of a movable object with respect to a fixed object. Regarding the detector.

[Background of the invention]

Position detectors using the magnetostrictive effect of ferromagnetic materials are described, for example, in the journal IEEE Transactions on Nuclear Science, no.
NS-25 Volume 1, February 1978, Pages 93 to 97
DCBettencourt and C.H.
A magnetosonic type rod position monitoring system for new clear power by CMMeijer
Plants (A Magneto-Sonic Type Rod
Position Monitoring System For Nuclear
It is described in a paper entitled "Power Plants".
The position detector measures the propagation time t of magnetostrictive ultrasonic waves generated by a permanent magnet attached to a movable object, and uses the ultrasonic propagation velocity v to calculate A position x is calculated.

Since this conventional position detector measures the position based on the ultrasonic propagation time, the propagation velocity v
If it changes for some reason, it will directly appear as a position detection error. For example, Fe: 52%,
A 42% Ni ferromagnetic waveguide has a temperature coefficient of propagation velocity of approximately -0.015%°C, and the ambient temperature is 300°C.
If the value changes, the error will be approximately 4.5%.

[Purpose of the invention]

An object of the present invention is to provide a position detector for detecting the relative position of a movable object with respect to a fixed object with high resolution and high precision, which is almost unaffected by temperature changes.

[Summary of the invention]

The above object is to provide a waveguide made of a ferromagnetic material, a conducting wire wired inside the waveguide in the tube axis direction, and a pulse current generating means for applying a pulse current to the conducting wire.
a plurality of stationary magnetic field generating means periodically arranged at predetermined intervals in the axial direction of the waveguide; and a movable object that is outside the waveguide and moves in the axial direction of the waveguide. a movable side magnetic field generation means installed in the fixed side magnetic field generation means and a movable side magnetic field generation means, an ultrasonic pulse detection means for detecting ultrasonic pulses generated at the positions of the fixed side magnetic field generation means and the movable side magnetic field generation means and propagated in the waveguide; an ultrasonic pulse discrimination means for discriminating between a fixed ultrasonic pulse produced by the fixed magnetic field generation means and a movable ultrasonic pulse produced by the movable magnetic field generation means from the ultrasonic pulses detected by the pulse detection means; Ultrasonic pulse counting means for counting fixed-side ultrasonic pulses until detection, and ultrasonic pulses for measuring the detection time interval of fixed-side ultrasonic pulses and the detection time interval between fixed-side ultrasonic pulses and movable-side ultrasonic pulses. By providing an interval measuring means and a means for calculating the position of the movable object with respect to the tube axis direction of the waveguide using the output of the ultrasonic pulse counting means and the output of the ultrasonic pulse interval measuring means, achieved.

With the above configuration, the following is affected by temperature:
Only the measured value is between the fixed magnetic field generating means closest to the movable magnetic field generating means and the movable magnetic field generating means, and if there are multiple fixed magnetic field generating means up to this fixed magnetic field generating means, the distance is a pulse. It becomes a count value of several numbers, and the influence of temperature disappears. For this reason,
Highly accurate measurement becomes possible.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The present invention will be described in more detail using Examples, but these are merely illustrative, and it goes without saying that various changes and improvements may be made without going beyond the scope of the present invention.

FIG. 1 is a block diagram showing the configuration of a position detector according to an embodiment of the present invention, including a perspective view of an object to be measured. The permanent magnet 4 shown in FIG. 1 will hereinafter be referred to as a fixed magnet, and will be represented by symbols M1, M2, . . . from the detection coil 6 side. Further, permanent magnets 10a and 10b attached to the movable object 9 are referred to as movable magnets Ma and Mb.

Now, when an excitation pulse current is applied to the core wire 2 from the excitation pulse current generation circuit 1 shown in Fig. 1, the fixed magnet M
Magnetostrictive ultrasonic waves are generated in the ferromagnetic waveguide 3 at the positions where the magnets 1, M2, . . . and the movable magnets Ma, Mb are present. This ultrasonic wave propagates through the waveguide 3, reaches the guide 5, and induces a voltage in the coil 6. After the voltage is amplified by an amplifier 7, the voltage is waveform-shaped through a waveform shaping circuit 11.

FIG. 2b is a pulse waveform diagram showing the output signal of the waveform shaping circuit 11 after application of the excitation pulse current, and this output signal will hereinafter be referred to as an ultrasonic pulse. Further, the ultrasonic pulses corresponding to the fixed magnets M1, M2, . . . and the movable magnets Ma, Mb are respectively represented as S1, S2, . . . and Sa, Sb. FIG. 2a shows the waveform of the excitation pulse.

When detecting an ultrasonic pulse as shown in Figure 2b, the propagation time t1 between the ultrasonic pulses Si and S _i+1 due to the fixed magnet, the propagation time t2 between Si and Sa, and the ultrasonic pulse Sa are detected. By counting the number i of ultrasonic pulses until the position x of the movable magnet Ma can be calculated using the following equation.

x=(i+t2/t1)・d...(1) Here, d is the installation interval of the fixed magnets.

In short, digital measurement by the number of ultrasonic pulses by a fixed magnet (i and d in equation (1)), and 2
Precise measurement by interpolation using ultrasonic propagation time (t2/t1·d in equation (1)) is also used between the fixed magnets.

FIG. 3 shows an example of the position detector signal processing circuit of this embodiment, which is composed of an ultrasonic pulse discrimination section, an ultrasonic pulse counting section, and an ultrasonic pulse interval measuring section. The excitation pulse current is input to terminal 100, and the ultrasonic pulse is input to terminal 200. The circuit 13 in FIG. 3 is an ultrasonic pulse discriminator. As shown in FIG. 1, since the fixed magnets are installed at regular intervals, the time intervals of the ultrasonic pulses generated by the fixed magnets are approximately equal. However, the pulse time interval caused by the ultrasonic pulses generated by the movable magnet varies greatly. Therefore, in the ultrasonic pulse discriminator 13, the ultrasonic pulses generated by the fixed magnet and the ultrasonic pulses generated by the movable magnet are separated based on the pulse time interval.
Furthermore, in this embodiment, since the position of the movable magnet Ma matters, the ultrasonic pulse discriminator 13 extracts only the ultrasonic pulse Sa caused by the movable magnet Ma. When the movable magnet Ma and the fixed magnet completely overlap, the ultrasonic pulse caused by the movable magnet Ma and the ultrasonic pulse caused by the fixed magnet cannot be separated, and only the ultrasonic pulse Sb caused by the movable magnet Mb can be separated. In the ultrasonic pulse discriminator 13, a signal separated from the detected ultrasonic pulse pattern is
or Sb.

Next, the ultrasonic pulse counting section will be explained. The excitation pulse current resets the ultrasonic pulse discriminator 13, counter 17, and counter 19 via the delay circuit 12. The first output signal (signal a in the figure) of the ultrasonic pulse discriminator 13 remains at a high level (hereinafter referred to as "H" in this specification) from after the excitation pulse current is applied until the ultrasonic pulse by the movable magnet Ma is detected. ), and by inputting this signal and the ultrasonic pulse input to the terminal 200 to the AND gate 18, the counter 1
9, i in equation (1) (the number of ultrasonic pulses generated by the fixed magnet until the ultrasonic pulse Sa generated by the movable magnet Ma is detected) is counted.

Next, the ultrasonic pulse interval measuring section will be explained. The second output signal (signal b in the figure) of the ultrasonic pulse discriminator 13 is a signal that becomes "H" for a slightly shorter time than the ultrasonic propagation time between the fixed magnets after the ultrasonic pulse is detected. This signal and the clock oscillator 14
The clock pulse is input to the AND gate 15 and becomes the input to the ultrasonic pulse interval measuring counter 17.

The third output signal (signal c in the figure) of the ultrasonic pulse discriminator 13 is an ultrasonic pulse generated by a fixed magnet, and this signal resets the counter 17 via the OR gate 16.

The fourth output signal (signal d in the figure) of the ultrasonic pulse discriminator 13 is Sa, which is the first pulse of the ultrasonic pulses Sa and Sb generated by the movable magnet separated from the detected ultrasonic pulse. The value of the counter 17 is taken into the latch 21 by using the signal as a load signal of the latch 21. This is shown in Figure 2b.
This value corresponds to t2. When the movable magnet Ma completely overlaps the fixed magnet, the signal d is from the movable magnet.
This becomes an ultrasonic pulse Sb due to Mb. In this case, the content of the latch 21 is a value corresponding to the propagation time between the fixed magnet and the movable magnet Mb (this is
It is equal to the propagation time between Ma and Mb. ), and if the position is calculated using this value, the value of the movable magnet Mb will be found. Therefore, the fifth output signal (signal e in the figure) of the ultrasonic pulse discriminator 13 clears the contents of the latch 21.

The signal e is a signal indicating that the movable magnet Ma overlaps with the fixed magnet. This is a case where an ultrasonic pulse is detected by a fixed magnet and no ultrasonic pulse is detected after a time τ corresponding to the interval between movable magnets. Clear signal.

The sixth output signal (signal f in the figure) of the ultrasonic pulse discriminator 13 is the first ultrasonic pulse generated by the fixed magnet after the load signal d of the latch 21, and this signal is the load signal of the latch 22. be. This causes the content of latch 22 to be a value corresponding to the propagation time between the fixed magnets. This is t1 in Figure 2b
This value corresponds to .

Further, the value of the counter 19 is loaded into the latch 20 by the excitation pulse, and the latch 20 is loaded with the movable magnet Ma.
The number of ultrasonic pulses generated by the fixed magnet until detecting the ultrasonic pulse Sa is captured.

As described above, the values of i, t2, and t1 in equation (1) are stored in the latches 20, 21, and 22, respectively, and the arithmetic circuit 23 uses the contents of each latch to move the movable magnet Ma The position x of is calculated.

In FIG. 4, the ultrasonic pulse discriminator 13 of FIG.
This is a specific circuit example. The ultrasonic pulse discriminator is
It consists of a fixed-side ultrasonic pulse discrimination section, a movable-side ultrasonic pulse discrimination section, an overlap detection section between a movable magnet and a fixed magnet, and a fixed-side ultrasonic pulse detection section after detecting the movable-side ultrasonic pulse.

Ultrasonic pulses are input to terminal 200. Monostable multivibrator 24 by ultrasonic pulse
is set. The setting time is slightly shorter than the propagation time of the fixed magnet installation interval. The output of the monostable multivibrator 24 is the output signal b of the ultrasonic pulse discriminator 13 in FIG.

Further, by inputting the output of the monostable multivibrator 24 and the ultrasonic pulse to the AND gate 25, the output of the AND gate 25 becomes an ultrasonic pulse generated by the movable magnet. Therefore, and gate 25
By inputting the output of the inverter 26 and the output and the ultrasonic pulse to the AND gate 27, the output of the AND gate 27 becomes an ultrasonic pulse generated by the fixed magnet. This is the output signal c of the ultrasonic pulse discriminator 13.

The ultrasonic pulse produced by the movable magnet, which is the output of AND gate 25, is input to the set terminal of flip-flop 28, and its output and the output of AND gate 25 are input to AND gate 29. As a result, the output of the AND gate 29 becomes the AND gate 2
This is the first pulse among the 5 output pulses,
Usually, it is an ultrasonic pulse Sa generated by a movable magnet Ma. Only when the movable magnet Ma and the fixed magnet overlap, the ultrasonic pulse Sb is produced by the movable magnet Mb.
This signal becomes the output signal d of the ultrasonic pulse discriminator 13.

Furthermore, the flip-flop 30, which has been set by the excitation pulse, is reset by the signal d. The Q output of the flip-flop 30 is the output signal a of the ultrasonic pulse discriminator 13.

Next, the overlap detection section of the movable magnet and the fixed magnet will be explained.

The signal c is passed through the delay circuit 31 to the AND gate 3.
2 is input. The delay time is the moving magnet Ma,
This is the ultrasonic propagation time τ between Mb. The other input of AND gate 32 is signal d. Flip-flop 33 set by the output of AND gate 32
The Q output becomes "H" in the following case.
One is when the movable magnet Ma and the fixed magnet overlap, and the flip-flop 33 is set by the ultrasonic pulse Sb. The other case is when the interval between the fixed magnet and the movable magnet Ma is equal to the installation interval of the movable magnets, and in this case, the signal for setting the flip-flop 33 is the ultrasonic pulse Sa. Also,
A signal obtained by delaying the output pulse of the AND gate 32 by the propagation time τ between the movable magnets via the delay circuit 34 and an output signal of the AND gate 25 (this is an ultrasonic pulse generated by the movable magnet) are output to the AND gate 32.
5 is input.

It is in the latter of the above two cases that a pulse appears at the output of the AND gate 35. Therefore, by ANDing the output of the flip-flop 36 set by the output of the AND gate 35 and the Q output of the flip-flop 33, the AND gate 37 is set only when the movable magnet Ma and the fixed magnet overlap.
The output becomes "H". This is the output signal e of the ultrasonic pulse discriminator 13.

Next, the fixed side ultrasonic pulse detection section after detecting the movable side ultrasonic pulse will be explained.

The Q output of the flip-flop 38 set by the signal d and the signal c, which is an ultrasonic pulse generated by a fixed magnet, are input to the AND gate 39, and the output signal is input to the flip-flop 40 and the AND gate 41.
becomes the signal f. As a result, the first ultrasonic pulse after the ultrasonic pulse detected by the movable magnet is extracted.

FIG. 5 shows the circuit operation when both movable magnets Ma and Mb are located between the fixed magnets. A is pulse current, B is ultrasonic pulse,
Signals a and D in Fig. 4 remain in the "H" state until the movable ultrasonic pulse is detected. Signals b and E in Fig. 4 remain in the "H" state for a time corresponding to the installation interval of the fixed magnets. Signals c and F in FIG. 4 indicate fixed side ultrasonic pulses, G is a clock signal for ultrasonic pulse interval measurement, and H indicates movable side ultrasonic pulses. Signals d and I in FIG. 4 indicate overlap detection signals between the fixed magnet and the movable magnet, and signal e in FIG. 4 indicates the fixed-side ultrasonic pulse after detection of the movable-side ultrasonic pulse.
It is.

In this case, the pulse interval t2 is between the fixed magnet and the moving magnet.
The arithmetic circuit 23 calculates the position x using the contents of the latches 20 to 22 according to equation (1).

Figure 6 shows the circuit operation when the movable magnet Ma and the fixed magnet are overlapped, and A to J are A in Figure 5.
It corresponds to J. In this case, a value corresponding to t2 in the figure is once loaded into the latch 21, but its contents are cleared by the signal e and become 0.
Arithmetic circuit 23 can then calculate position x using the contents of latches 20-22.

Furthermore, if a movable magnet sandwiches a fixed magnet,
Even if the movable magnet Mb overlaps the fixed magnet, the fifth
The position can be detected by the rotational movement shown in the figure.

Note that the oscillation period of the excitation pulse current circuit is set to a time slightly longer than the time required for the ultrasonic waves generated by the fixed magnet farthest from the reference point to reach the guide 5.

In the above explanation, an example is shown in which a permanent magnet is used as the magnetic field generating means, but as shown in FIG. 7, the position can be detected in the same way even if the fixed magnet is replaced with a coil 42 and excited at the same time as the core wire 2. .

〔Effect of the invention〕

As explained above, according to the present invention, the number of pulses until the pulse interval changes is digitally counted, and at the same time, the ratio of the propagation time between adjacent fixed magnets to the propagation time between the fixed magnet and the movable magnet is calculated. By using this interpolation method in combination, highly accurate position detection that is almost unaffected by temperature changes around the waveguide becomes possible.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a position detector according to an embodiment of the present invention, including a perspective view of the object to be measured, and Fig. 2 is the output of the waveform shaping circuit after applying the excitation pulse and excitation pulse current. 3 is a block diagram of a signal processing circuit of a position detector according to an embodiment of the present invention, and FIG. 4 is a block diagram showing the configuration of the ultrasonic pulse discriminator shown in FIG. 3. , Fig. 5 is a signal waveform diagram of each part of the signal processing circuit when the fixed magnets do not overlap, Fig. 6 is a signal waveform diagram of each part of the signal processing circuit when the fixed magnet and movable magnet are overlapped, and Fig. 7 FIG. 3 is a diagram showing another embodiment of the present invention. 1... Excitation pulse current generation circuit, 2... Core wire,
3...Ferromagnetic waveguide, 4...Fixed magnet, 6...
Detection coil, 9...Movable object, 10...Movable magnet, 13...Ultrasonic pulse discriminator, 17, 19...
... Counter, 20 to 22 ... Latch, 23 ... Arithmetic circuit, 42 ... Coil, 100 ... Excitation pulse input terminal, 200 ... Ultrasonic pulse input terminal.

Claims (1)

[Scope of Claims] 1. A waveguide made of a ferromagnetic material, a conducting wire wired inside the waveguide in the tube axis direction, a pulse current generating means for applying a pulse current to the conducting wire, and a pulse current generating means for applying a pulse current to the conducting wire, a plurality of fixed-side magnetic field generating means arranged periodically at predetermined intervals in the axial direction of the waveguide; and arranged on a movable object that is outside the waveguide and moves in the axial direction of the waveguide. a movable side magnetic field generating means, an ultrasonic pulse detecting means for detecting an ultrasonic pulse generated at the positions of the fixed side magnetic field generating means and the movable side magnetic field generating means and propagating in the waveguide, and the ultrasonic pulse detecting means. an ultrasonic pulse discriminator for discriminating between a fixed ultrasonic pulse produced by the fixed magnetic field generating means and a movable ultrasonic pulse produced by the movable magnetic field generating means from the ultrasonic pulses detected by the means; an ultrasonic pulse counting means for counting the fixed side ultrasonic pulses up to 1000 ms, and an ultrasonic pulse interval measurement means for measuring the detection time interval of the fixed side ultrasonic pulses and the detection time interval of the fixed side ultrasonic pulses and the movable side ultrasonic pulses. and means for calculating the position of the movable object with respect to the tube axis direction of the waveguide using the output of the ultrasonic pulse counting means and the output of the ultrasonic pulse interval measuring means. Detector. 2. The position detector according to claim 1, wherein both the fixed side magnetic field generation means and the movable side magnetic field generation means are permanent magnets. 3. The position detector according to claim 1, wherein the fixed side magnetic field generating means is a coil. 4 The installation interval of the fixed side magnetic field generation means is d, the detection time interval of the fixed side ultrasonic pulses by the mutually adjacent fixed side magnetic field generation means is t1, and the movable side ultrasonic pulse and the movable side magnetic field generation by the movable side magnetic field generation means. The detection time interval of fixed side ultrasonic pulses by the fixed side magnetic field generating means located on the side of the ultrasonic pulse detection means with respect to the position of the means is t2, and the fixed side ultrasonic pulses detected until the movable side ultrasonic pulses are detected. Claim 1, wherein the number of is i, and the position x of the movable object on which the movable side magnetic field wave generating means is installed is calculated by the formula x=(i+t2/t1)・d.
Position detector as described in section. 5. Two movable magnetic field generating means are used as the movable magnetic field generating means and are spaced apart by a distance shorter than the predetermined interval of the fixed magnetic field generating means, and one of the movable magnetic field generating means and the fixed magnetic field generating means are at the same position. 2. The position detector according to claim 1, wherein the position of the movable object is calculated using the ultrasonic pulses generated by the other movable side magnetic field generating means when the movable object overlaps with the movable magnetic field generating means.