JPH0374765B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention applies a signal to a magnetostrictive wire, detects the signal transmitted through the magnetostrictive wire by a receiving means, and measures the propagation times t ₁ and t ₂ at this time. The present invention relates to a device that detects the position of a target object. More specifically, the present invention relates to a device suitable for outputting a digital signal as a signal representing a position.

[Background of the invention]

Regarding position detection devices using magnetostrictive effects,
There are various publicly known documents, one example is Tokugan Sho.
No. 53-22282 "Automatic Balancing Instrument" etc. The devices described in these documents are of a type that outputs analog signals, and cannot be directly applied to output digital signals. Furthermore, there are many problems that must be resolved before applying conventional technology to digital equipment, such as digitizing it using common sense methods and making it extremely expensive.

[Object of the present invention]

The present invention has been made in view of these points, and its purpose is to provide a position detection device that outputs a digital position-related output signal, has a high-speed response, and does not require adjustment. be.

[Summary of the invention]

The present invention provides: an excitation means that applies ultrasonic waves from an end of a magnetostrictive wire; a reception means that is located at a certain point on the magnetostrictive wire and outputs a signal every time the ultrasonic wave passes through the position; and the excitation means Period t1 from when the ultrasonic wave is emitted until the receiving means first outputs a signal, current I ₀
a first integrator A that integrates the current I0; a second integrator B that integrates the current _I0 during a period t2 from when the receiving means outputs the first signal until it outputs the second signal; first return means 7, 9, which applies a current I1 of opposite polarity to ₀ to the first integrator and converts the time X from the application of this current I1 until the voltage of the first integrator becomes 0 into a digital value; SW2, the time that is the sum of the time X until the voltage of the first integrator becomes 0 when the current I1 is applied to the second integrator, and the time Y until the voltage of the second integrator becomes 0 ( A value corresponding to (2t1+t2) is calculated from the second exchange means 8, 10, SW2 which converts X+Y) into a digital value, and the digital signals introduced from the first and second conversion means, and this value is set. and an autospan circuit that adds a compensation current Ic to the current _I0 so that the current Ic becomes the same as the current I0.

[Effect]

The first integrator controls the period from when the excitation means emits ultrasonic waves until the reception means first outputs a signal;
Since the current I ₀ is integrated, the integrated voltage is proportional to the time t1 shown in FIG.

The second integrator generates a current during the period from when the receiving means outputs the first signal until it outputs the second signal.
Since I ₀ is integrated, the integrated voltage is proportional to time t2 shown in FIG.

Since the first conversion means converts the discharge time X of the integrated voltage stored in the first integrator into a digital value, the digital value means the time t1 shown in FIG. .

The second conversion means calculates the time (X+Y) which is the sum of the discharge time X of the first integrator and the discharge time Y of the second integrator.
Since the digital value is converted into a digital value, the digital value means the time (t1+t2) shown in FIG.

The autospan circuit introduces a signal representing time (t1+t2) and a signal representing time t1, and calculates a value corresponding to full span (2t1+t2). Then, in order to keep this value constant, the current is
Since the compensating current Ic is added to I ₀ , the discharge times X and Y are not affected by characteristic fluctuations of the magnetostrictive wire.

That is, the output of the first converting means indicates the position of the receiving means.

[Explanation based on examples]

The present invention will be explained in detail below using the drawings.

FIG. 1 is a diagram showing an example of the configuration of a position detection means using a magnetostrictive effect used in a device according to the present invention. However, the configuration shown in FIG. 1 is not new, and the position detection means in the present invention is not limited to this configuration. In the figure, reference numeral 1 denotes a magnetostrictive wire made of a linear magnetostrictive material such as Ni-SPANC or nickel. 2 is an excitation means for generating an ultrasonic signal in the magnetostrictive wire 1;
For example, a coil is used. In the configuration example shown in FIG. 1, the excitation means 2 is fixed to the end of the magnetostrictive wire 1. 3 is an oscillator, for example, a crystal oscillator or the like is used. 4 is an ultrasonic signal receiving means, for example, a coil or a piezoelectric element is used;
Here, an example using a coil will be explained. This receiving means 4 is electromagnetically coupled to the magnetostrictive wire 1, and furthermore,
The structure is such that the position can be moved along the magnetostrictive line 1. The device according to the present invention attempts to output the position of this receiving means 4 as a digital signal. 5, 5' are comparators, 6,
6' is a reference voltage.

Since the operation of the apparatus shown in FIG. 1 configured as described above can be easily understood from the above-mentioned known documents, only a brief description of the operation will be given here. The ultrasonic wave oscillated from the excitation means 2 propagates through the magnetostrictive wire 1 and reaches the reception means ₄ after time t1 from the excitation. Further, the ultrasound propagates through the magnetostrictive wire 1, is reflected at its end, and passes through the receiving means 4 again at a time t ₂ from the time when it previously passed through the receiving means 4. Therefore, the receiving means 4 detects the signal at times t ₁ and (t ₁ +t ₂ ) after the ultrasonic wave is oscillated. It is obvious that the position of the receiving means 4 on the magnetostrictive line 1 can be known by measuring these times t ₁ and t ₂ .

A second circuit digitally measures the times t ₁ and t ₂ using the detection means described above.
It is a diagram.

FIG. 2 is a block diagram showing an example of the configuration of an apparatus according to the present invention. In the figure, A and B are integrators, and the output current of power supplies 14 and 15, which will be described later, is
It integrates I ₀ and I ₁ . Comparators 7 and 8 introduce the outputs of integrators A and B and compare them with predetermined values. Counters 9 and 10 input the output signals of comparators 7 and 8 and count the pulse widths thereof. Reference numeral 11 denotes an auto-span circuit, which inputs the output signals of counters 9 and 10 and the full-scale set value, and controls a compensation power supply 16, which will be described later, to keep the full-span value constant. 12 is an output register which receives the output of the counter 9 and outputs a digital signal corresponding to the position of the receiving means 4 described above. Reference numeral 13 denotes a setting device, which sets a full span value to the auto span circuit 11. 14, 15, and 16 are power supplies. Usually, constant current sources are used for the power supplies 14, 15, and 16. However, the current value Ic of the power source 16 is variable by the auto span circuit 11.
SW ₁ and SW ₂ are changeover switches that apply the output currents of the power supplies 14, 15, and 16 mentioned above to the integrators A and B. Power supplies 14 and 16 are connected to the changeover switch _SW1 , and power supply 15 is connected to the changeover switch SW1.
They are applied to integrators A and B via SW ₂ , respectively. Here, power supplies 14 and 15 are applied to integrators A and B with opposite polarities. Although the changeover switches SW ₁ and SW ₂ are illustrated as one switch each having three positions, one switch may be provided for each contact point. The changeover switches SW ₁ and SW ₂ are switched by signals from elements (not shown in FIG. 2) corresponding to the comparators 5 and 5' in FIG. 1.

The operation of the apparatus shown in FIG. 2 constructed as described above is as follows. Note that FIG. 3 is a diagram showing the operation and timing of each part of the apparatus shown in FIG. 2, and the operation of FIG. 2 will be explained with reference to this FIG.

First, a drive pulse is applied to the excitation means 2 from the oscillator 3 shown in FIG. This is shown in Figure 3a. In synchronization with this drive pulse (Figure a), the changeover switch _SW1 is connected to the contact p. Therefore, integrator A operates as shown in FIG. 3e.
As a result, the output voltage of integrator A increases, and comparator 7 monitors this output voltage.
Normally, comparators 7 and 8 compare the voltages of the introduced integrators A and B with a zero level voltage. The operation timing of this comparator 7 is shown at i in FIG.

As described above, the emitted ultrasonic wave is transmitted at time t ₁
Later, it reaches the receiving means 4. Then, this ultrasonic wave is detected, and the _P1 pulse shown in FIG. 3B is outputted from the receiving means 4. This _P1 pulse is compared with a reference voltage 6, and a waveform-shaped signal as shown in Fig. 3c is outputted from the comparator 5.

In synchronization with the rising edge of the output pulse of the comparator 5 (c in FIG. 3), the contact point of the changeover switch _SW1 becomes q. As a result, the integrator A
, the integration of the current I ₀ ends in the period shown in e of FIG.

Then, integrator B calculates current I ₀ of power supply 14
Start integrating [see Figure 3 f]. Note that when integrator B starts integration, its output voltage is monitored by comparator 8 [see k in FIG. 3].
Thereafter, the ultrasonic wave that has passed through the receiving means 4 is reflected at the end and passes through the receiving means 4 again after time _t2 . Therefore, the receiving means receives this reflected pulse _P2 , and the comparator 5' shapes the waveform of this [see d in FIG. 3].Synchronizing with this pulse, the contact point of the changeover switch _SW1 is set to The voltage flowing into integrator B is cut off. Therefore, integrator B has a current I ₀
The voltage integrated over time t ₂ is held.

Next, at the first falling edge of the clock pulse CLK (see FIG. 3g) that occurs after the rising edge of the signal from the comparator 5 (FIG. 3c), the following operations begin.

The changeover switch SW ₂ becomes the contact point u (see g and h in Figure 3).

Counters 9 and 10 start operating (see l and m in FIG. 3).

According to the above operation, the integrator A begins to integrate the current _I1 of the power supply 15 via the contact u of the changeover switch _SW2 . Note that since the currents I ₀ and I ₁ from the power supplies 14 and 15 move in opposite directions, the integrator A operates in the direction of discharging the voltage integrated by the current I ₀ . Note that there is a slight hold period when the current in integrator A switches from I ₀ to I ₁ as shown in Figure 3, but this is just a design thing, so it should be completely synchronized. It is clear that the hold period may be longer or the hold period may be longer.

In this way, the integrator A operates at time t ₁ (Fig. 3 P ₁
Integrate the current I ₀ by (until the pulse is applied),
This time, the integrated voltage is discharged with a current _I1 . Finally, the output voltage reaches zero level.

The comparator 7 captures the moment when the level reaches this zero level and uses it as a trigger for the following operation.

<> Stop the operation of the counter 9 (see Figure 3 i and l). In other words, the counter 9 was measuring the period during which the integrator A was discharging.

<> Set changeover switch SW ₂ as contact point v.

That is, the integrator B starts discharging due to the current _I1 of the power source 15 (see FIG. 3j). Incidentally, before this time, the integrator B has already integrated the current I ₀ for a time t ₂ and is holding it. The reason for this is that the magnitudes of the current values I ₀ and I ₁ are determined in advance to achieve such timing. Furthermore, the operation of the changeover switch _SW2 causes the integration operation of the integrator A to stop (see FIG. 3h).

Please note that the changeover switch cannot be pressed even during the above operation.
SW ₂ has become a contact point v, and integrator B continues to discharge with current I ₁ . Then, when the output voltage of the integrator B reaches zero level, the comparator 8 captures this and uses it as a trigger for the following operation.

<> Stop the operation of the counter 10 [Fig. 3 m
reference〕. In other words, the counter 10 measures the sum of the periods during which the integrators A and B integrate (discharge) the current _I1 . In other words, the output signal of the counter 10 is generated during the period (t ₁ +
_t2 ).

<> Set changeover switch SW ₂ as contact W.

That is, the integrating operation of integrator B is stopped.

On the other hand, as described above, the digital signal corresponding to the period t ₁ (which can be seen in place of distance) shown in FIG. 1 is taken out as the output signal of the counter 9. This output signal is taken out via the output register 12.

The above-mentioned apparatus may cause a measurement error when a variable factor such as a temperature coefficient comes into contact with the characteristics of the magnetostrictive wire. Therefore, full span [time (2t ₁ +
If the value of t ₂ ] is controlled to be constant, such errors can be eliminated. In the apparatus of the present invention, an autospan circuit 11 is provided for the above purpose. This auto span circuit 11 is connected to the setting device 1.
3, a signal corresponding to a full span serving as a reference is introduced, and this value is compared with a value based on the output signals of counters 9 and 10, and the current value of the compensation power supply 16 is adjusted so that this difference becomes zero. It controls IC.

As explained above, a digital signal corresponding to the position of the receiving means 4 can be obtained from the output register 12 of the apparatus shown in FIG.

In addition, in order to obtain high resolution, power supplies 14 and 15 are connected.
The currents I ₀ and I ₁ are set to have a relationship of I ₁ <<I ₀ .
That is, by doing so, the counting period of the counters 9 and 10 can be made sufficiently long.

FIG. 4 is a diagram showing a more specific configuration example of the apparatus shown in FIG. 2 and the apparatus shown in FIG. 1. In the same figure,
Elements (blocks) corresponding to FIGS. 1 and 2 are given the same element numbers. Since its operation has been explained in detail in the section of the apparatus shown in FIG. 2, the main parts added to the configuration shown in FIG. 2 will be explained here.

The autospan circuit 11 is composed of an adder 111 and a comparator 112. Then, the output signal of the adder 111 and the reference full span value
Tc is compared by a comparator 112. As a result, 3 of a, b, and c are set so that this difference becomes zero.
Two contact signals are output.

Further, the compensation power supply 16 has three switches as shown in FIG. These three switches are selected by signals a, b, and c from the autospan circuit 11, and a corresponding current value Ic is applied to the integrator A in a superimposed manner with the current _I0 .

Further, since the control signals for the changeover switches SW ₁ and SW ₂ are shown in FIG. 4, their explanation will be omitted.

Furthermore, as can be seen from Figures 2 and 4, the current
I ₀ and I ₁ can be in either direction as long as they are opposite to each other.

[Effects of the present invention]

As described above, according to the present invention, the following effects can be obtained.

Highly accurate digital position detection is possible.

Since the drive signal from the oscillator 3 is one shot, the response is faster than that of the conventional analog feedback type.

Since I ₁ ≪ I ₀ , the counting time can be long, and even if the counter clock CLK is slow, high resolution can be achieved.

In principle, the accuracy is determined by the ratio of charging and discharging currents, and the offset of the comparator and integrator can be ignored, and the accuracy of the integrating capacitor is not required.

The charge/discharge current ratio is controlled by an autospan circuit, so it can be made unadjusted.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an example of the configuration of a position detection means using the magnetostrictive effect used in the device according to the present invention, FIG. 2 is a block diagram showing an example of the configuration of the device according to the present invention, and FIG. Figure 2 shows the operation of each part of the device.
FIG. 4, a diagram showing timing, is a diagram showing a more specific example of the configuration of the device in FIG. 2 and the device in FIG. 1. A, B... Integrator, SW ₁ , SW ₂ ... Changeover switch, 1... Magnetostrictive wire, 2... Excitation means, 3... Oscillator, 4... Receiving means, 5, 5', 7, 8... ... Comparator, 6 ... Reference voltage, 9, 10 ... Counter, 11 ... Auto span circuit, 12 ... Output register, 13 ... Setting device, 14, 15, 16
……power supply.

Claims (1)

[Scope of Claims] 1. Excitation means that applies ultrasonic waves from the end of the magnetostrictive wire; Receiving means that is located at a certain point on the magnetostrictive wire and outputs a signal every time the ultrasonic wave passes through that position; Period t1 from when the excitation means emits ultrasonic waves until the reception means first outputs a signal, current I ₀
a first integrator A that integrates the current I0; a second integrator B that integrates the current _I0 during a period t2 from when the receiving means outputs the first signal until it outputs the second signal; first converting means 7, 9, which applies a current I1 having a polarity opposite to ₀ to the first integrator and converts the time X from the application of the current I1 until the voltage of the first integrator becomes 0 into a digital value; SW2, the time that is the sum of the time X until the voltage of the first integrator becomes 0 when the current I1 is applied to the second integrator, and the time Y until the voltage of the second integrator becomes 0 ( A value corresponding to (2t1+t2) is calculated from the second exchange means 8, 10, SW2 which converts X+Y) into a digital value, and the digital signals introduced from the first and second conversion means, and this value is set. A position detection device comprising: an autospan circuit that adds a compensation current Ic to the current _I0 so that the current Ic becomes the same as the current I0.