JPS6123917A - Position detector - Google Patents

Abstract

PURPOSE:To detect the position of a moving body from the number of magnetostrictive ultrasonic waves and their propagation time by providing plural fixed magnetic field generating means in the moving direction of the moving body and providing >=2 magnetic field generating means to the moving body, and generating a magnetostrictive ultrasonic wave in a waveguide with each magnetic field. CONSTITUTION:An exciting pulse current is inputted to a terminal 100 and an ultrasonic wave pulse is inputted to a terminal 200. Time intervals of ultrasonic pulses are nearly equalized through a fixed magnet 4, but time intervals of ultrasonic pulses are varied greatly through a movable magnet 10. The position of the movable magnet 10a is an object of detection, so only ultrasonic pulses Sa by the movable magnet 10a are extracted from ultrasonic pulses by movable magnets which are separated by a period detecting circuit 13. When the movable magnet 10a and fixed magnet 4 overlap each other, the separated ultrasonic waves by the movable magnets are ultrasonic wave pulses Sb by a movable magnet 10b, but the period detecting circuit 13 decides on the relative position relation among the respective magnets from the ultrasonic wave pulse relation between the separated ultrasonic wave pulses by the movable magnet and ultrasonic wave pulses by the fixed magnet.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a position detector that uses the magnetostrictive effect of a ferromagnetic material, and is particularly suitable for detecting the relative position of a movable object with respect to a fixed object. Concerning vessels.

[Background of the Invention] A position detector using the magnetostrictive effect of a ferromagnetic material is described, for example, in the magazine IE Transactions on
Nuclear Science (IEEE'l'ransa)
tions on Nuclear 5science
) Volume N5-25, No. 1, February 1978, No. 93
D. C. Bettencourt and C. H. Meijer are published on pages 97 to 97.
) Author: A Magnetosonic Type Rod φ Position Monitoring System for Nuclear Bower Planon (A Magneto-5oi
lic TypeRod position Mon
Itoring System porNuclear
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 determine the position of the movable object is calculated.

Since this conventional position detector measures the position based on the ultrasonic propagation time, if the propagation velocity V changes for some reason, this will directly appear as a position detection error. For example, pe: 52%.

For Ni: 42-chi ferromagnetic waveguide, -0,015%/
It has a temperature coefficient of propagation velocity of about C and an ambient temperature of 300°C.
A change of 0 results in an error of approximately 4.5%.

[Purpose of the invention]

The purpose of the present invention is to provide a system that is almost unaffected by temperature changes;
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.

[Summary of the invention]

The present invention provides a plurality of fixed magnetic field generating means in the moving direction of the movable object, and at least two magnetic field generating means on the movable object, and generates magnetostrictive ultrasound in the waveguide by each of these magnetic fields. The object is to detect the position of a movable object from both the number of ultrasonic signals and the propagation time.

The present invention will be described in more detail below using examples with reference to the drawings, but these are merely illustrative and various modifications and improvements may be made without going beyond the scope of the present invention. Of course.

[Embodiments of the invention]

FIG. 1 is a block diagram showing the configuration of a position detector according to the present invention, including a perspective view of a temporary measurement object.

The permanent magnet 4 in FIG. 1 will be referred to as a fixed magnet hereinafter, and the detection coils 611tll to Mt, M2 . It is represented by the symbol...

Also, a permanent magnet 10 attached to the movable object 9. .

10b is represented 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 magnets Ml, M2
, . . . and magnetostrictive ultrasonic waves are generated in the ferromagnetic waveguide 3 at the positions where the movable magnets M-, 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 passed through a waveform shaping circuit 11 to shape the waveform.

Figure 2(b) shows the waveform shaping circuit 1 after applying the excitation pulse current.
1 is a pulse waveform diagram showing an output signal of No. 1, and this output signal will hereinafter be referred to as an ultrasonic pulse. In addition, fixed magnet M 1+ M
2 +... and the ultrasonic pulses corresponding to the movable magnets Ma and Mb are Slr 8z +... and S, respectively.
, Sb. FIG. 2(a) shows the waveform of the excitation pulse.

When detecting an ultrasonic pulse as shown in Fig. 2(b), the propagation time j between the ultrasonic pulses SI and SL and 1 due to the fixed magnet
1, and S+=8-, and by counting the number i of ultrasonic pulses until the ultrasonic pulse S is detected.

The position X can be calculated using the following equation.

Here, d is the installation interval of the fixed magnets.

In short, digital measurement based on the number of ultrasonic pulses by the fixed magnet (1-d in equation (1)) and interpolation between the two fixed magnets using the ultrasonic propagation time are performed.

FIG. 3 shows a specific circuit example of a position detector according to the present invention. The excitation pulse current is input to the terminal 100, and the ultrasonic pulse is input to the terminal 200. The circuit 13 in FIG. 3 is a period detection circuit. 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 period detection circuit 13, the ultrasonic pulse generated by the fixed magnet and the ultrasonic pulse generated by the movable magnet are separated based on the pulse time interval. Furthermore, in this example,
Since the position of the movable magnet M is a problem, the period detection circuit 1
Only the ultrasonic pulse S caused by the movable magnet M is extracted from the ultrasonic pulse caused by the movable magnet separated in step 3. When the movable magnet M1 and the fixed magnet completely overlap,
The ultrasonic pulse generated by the separated movable magnet is generated by the movable magnet Mb.
The period detection circuit 13 determines the relative positional relationship of each magnet from the relationship between the ultrasonic pulses generated by the separated movable magnets and the ultrasonic pulses generated by the fixed magnets.

The excitation pulse current resets the period detection circuit 13, counter 17, and counter 19 via the delay circuit 12. The first output signal of the period detection circuits 1 and 3 (signal in the figure)
a)) is a signal that remains at a high level (hereinafter abbreviated as 'H' in this specification) from after the excitation pulse current is applied until the ultrasonic pulse is detected by the movable magnet M, and this signal and the terminal By inputting the ultrasonic pulses inputted to 200 to the AND gate 18, the counter 19 calculates the ultrasonic pulses generated by the fixed magnet until it detects the ultrasonic pulse S1 generated by i (the movable magnet M) in equation (1). number) is counted.

Further, the second output signal (signal Φ in the figure) of the period detection circuit 13 is a signal that becomes II H1F for a slightly shorter time than the ultrasonic propagation time between the fixed magnets after detecting the ultrasonic pulse. . This signal and the clock pulse of the clock oscillator 14 are input to an AND gate 15.

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

The fourth output signal of the period detection circuit 13 (signal (d) in the figure)
) is the first pulse S, Sb of the ultrasonic pulses S, , Sb by the movable magnet separated from the detected ultrasonic pulses.
This signal is used as a load signal for the latch 21, and the value of the counter 17 is taken into the latch 21. Movable magnet M
, completely overlaps the fixed magnet, the signal (d) becomes an ultrasonic pulse Sb generated by the movable magnet Mb. In this case, the self-response of the latch 21 is a value corresponding to the propagation time between the fixed magnet and the movable magnet Mb (this is the value corresponding to the propagation time between the movable magnet M-Mb
equal to the propagation time between ), 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 period detection circuit 13 clears the internal signal of the latch 21.

Signal (e) is a signal indicating that the movable magnet M 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 of the period detection circuit 13 (signal (f) in the figure)
) is the first fixed magnet ultrasonic pulse after the latch 21 load signal (d), and this signal is the latch 22
This is the load signal. Thereby, the content of the latch 22 becomes a value corresponding to the propagation time between the fixed magnets.

Further, the value of the counter 19 is loaded into a latch 20 with an excitation pulse, and the latch 20 is loaded with a movable magnet M.

The number of ultrasonic pulses generated by the fixed magnet until the ultrasonic pulse S is detected by the fixed magnet is captured.

As described above, the values of F 2 and il in equation (1) are stored in the launches 20, 21, and 22, respectively, and the arithmetic circuit 23 uses the contents of each latch to calculate the movable magnet M The position X of , is calculated.

FIG. 4 shows a specific circuit example of the period detection circuit 13 shown in FIG. Ultrasonic pulses are input to terminal 200. The monostable multivibrator 24 is set by the ultrasonic pulse. 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 period detection circuit 13 in FIG.

Furthermore, 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, by inputting the output of the AND gate 25 to the inverter 26 and inputting the output and the ultrasonic pulse to the AND gate 27, the output of the AND gate 27 becomes an ultrasonic pulse generated by a fixed magnet. This is the output signal (C) of the period detection circuit 13.

The eight sound wave pulses produced by the movable magnet, which are the outputs of the AND gate 25, are input to the set terminal of the flip-flop, and the Q output and the output of the AND gate 25 are input to the AND gate 29. As a result, the output of the AND gate 29 is
This is the first pulse among the output pulses of the AND gate 25, and is usually an ultrasonic pulse S generated by a movable magnet M.

The ultrasonic pulse Sb is produced by the movable magnet Mb only when the movable magnet M and the fixed magnet overlap. This signal becomes the output signal (d) of the period detection circuit 13.

The flip-flop 30 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 period detection circuit 13.

Signal (C) is input to AND gate 32 via delay circuit 31. The delay time is determined by the movable magnet M.

This is the ultrasonic propagation time τ between Mb. The other input of AND gate 32 is signal (d). The Q output of the flip-flop 33 set by the output of the AND gate 32 is to
Hn occurs in the following cases.

One is when the movable magnet M1 and the fixed magnet overlap, and it is the ultrasonic pulse Sb that sets the flip-flop. The other case is when the interval between the fixed magnet and the movable magnet M is equal to the installation interval of the movable magnets, and in this case, the signal that sets the flip-flop 33 is the ultrasonic pulse S. In addition, the output pulse of the AND gate 32 is transferred to the delay circuit 3.
4, a signal delayed by the propagation time τ between the movable magnets and the output signal of the AND gate 25 (this is an ultrasonic pulse produced by the movable magnet) are manually input to the AND gate 35. It is in the latter of the above two cases that a pulse appears at the output of the AND gate 35. Therefore, and gate 35
The Q output of the flip-flop 36 is set by the output of
By ANDing the Q output of the flip-flop 33, the output of the AND gate 37 becomes "'H" only when the movable magnet M and the fixed magnet overlap. This is the output signal (e) of the period detection circuit 13.

The Q output of the flip-flop 38 set by the signal (d) and the signal (C), which is an ultrasonic pulse generated by the fixed magnet, are input to the AND gate 39, and the output signal is converted into a signal via the flip-flop 40 and the AND gate 41. (f)
becomes. 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 the movable magnets M- and Mb are both located between the fixed magnets. Fifth
Figures (4) to (J) represent the excitation pulse, ultrasonic pulse, signal (a), and signal (b) in the circuit shown in Figure 3, respectively.
, signal (C), input of counter 19, AND gate 15
represents the timing of the output of signal (d), signal (e) and signal (f). In this case, the pulse interval t2 is the propagation time between the fixed magnet and the movable magnet M1, and the latches 20 to 2
Using the contents of 2, the calculation circuit 23 performs calculation according to equation (1) to find the position X.

FIG. 6 shows the circuit operation when the movable magnet M and the fixed magnet overlap, and (4) to (correspond to (4) to (Jet) in FIG. 5. In this case, the latch 21 The value corresponding to t2' in the figure is once taken in, but its contents are cleared by the signal (e) and becomes 0. Then, the arithmetic circuit 13 calculates the position X using the contents of the latches 20 to 22. be able to.

Furthermore, when the movable magnet is sandwiched between the fixed magnet numbers, even when the movable magnet M overlaps the fixed magnet, the position can be detected by the rotational movement shown in FIG.

Note that the oscillation period of the excitation pulse current circuit is set to a time slightly longer than the time fr 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 was shown in which a permanent magnet is used as the magnetic field generating means, but as shown in FIG.
Even if the core wire 2 and the core wire 2 are excited simultaneously, the position can be detected in exactly the same way.

〔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 the ratio of the propagation time between the fixed magnets that are in contact with each other at the same time 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 the position detector according to the present invention, including a perspective view of the object to be measured, and FIG. 2 is a pulse waveform showing the output signal of the waveform shaping circuit after applying the excitation pulse and excitation pulse current. 3 is a block diagram of the electric circuit of the position detector according to the present invention, FIG. 4 is a block diagram showing the configuration of the period detection circuit in FIG. 3, and FIGS. 5 and 6 are respectively on the reference point side. 3 represents the timing of signals at various points in the circuit shown in FIG. 3 when the second type of magnetic field generating means does not overlap with any of the first type of magnetic field generating means and when it overlaps with one of them. 7 are views corresponding to FIG. 1 of a position detector according to 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.
...Period detection circuit, 17.19...Counter, 20~
22--Latch, 23--Arithmetic circuit, 42--Coil, 1oo river excitation pulse input terminal, 2oo--Ultrasonic pulse input terminal.

Claims (1)

[Claims] 1. A waveguide made of a ferromagnetic material and having a conducting wire therein for applying a current, and a plurality of first type magnetic fields provided at regular intervals in the axial direction of the waveguide. generating means; at least two second type magnetic field generating means mounted on a movable object moving in the axial direction of the waveguide; means for converting into an electric signal, means for applying a current pulse to the conductive wire, means for counting ultrasonic signals generated at the position of the first type of magnetic field generating means, and the first type of magnetic field generating means adjacent to each other. Taking the ratio of the ultrasonic propagation time between the type of magnetic field generation means and the propagation time of the ultrasonic signal by the second type of magnetic field generation means located in the middle,
and means for calculating a relative position of the second type of magnetic field generating means with respect to the first type of magnetic field generating means. 2. Claim 1, wherein the first and second types of magnetic field generating means are both permanent magnets.
Position detector as described in section. 3. The position detector according to claim 1, wherein the first type of magnetic field generating means is a coil. 4. Set the installation interval of the first type of magnetic field generating means to d, using the position where the means for converting the ultrasonic signal to an electric signal exists as a reference point, and set the ultrasonic wave between the adjacent first type of magnetic field generating means as d. The propagation time is t_1, and the first type of magnetic field generating means located on the reference point side and closest to the second type of magnetic field generating means with respect to the second type of magnetic field generating means located on the reference point side and the reference The ultrasonic propagation time between the second type of magnetic field generating means located on the point side is _2, and the second type of magnetic field generating means located on the reference point side from the reference point is
The first type of magnetic field generating means exists in the range up to the point where it exists.
When the number of types of magnetic field generating means is i, the means for calculating the relative position of the second type of magnetic field generating means with respect to the first type of magnetic field generating means is expressed by the formula x=[i+(t_2/t_1 )]・d The position detector according to claim 1, characterized in that the distance x is calculated according to d. 5. When the second type of magnetic field generating means on the reference point side and one of the first type of magnetic field generating means exist at the same position, the second type of magnetic field for the first type of magnetic field generating means The means for calculating the relative position of the generating means is a first type of magnetic field that exists in an area from the reference point side to the point of existence of the second type of magnetic field generating means among the second type of magnetic field generating means. 2. The position detector according to claim 1, wherein the distance from the reference point to the second magnetic field generating means located on the reference point side is calculated from the number of generating means.