JPS63117607A - Method and apparatus for measuring space between conductive repulsion track and magnetic sensing device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for accurately determining the spacing of a magnetic sensing element from a conductive repulsion track. In this case, an alternating voltage is applied to the detection winding, and the current in this winding, which is dependent on the distance from the repulsion track to the detection winding, is used to measure this distance. Especially in the case of magnetic bearings and magnetic levitation devices, the excitation current of the magnets is controlled so that the magnets maintain a predetermined spacing while levitating, as used in magnetic transport technology to control the position of moving magnets and guide magnets. In order to maintain the controlling signal, it must be constantly measured. Measuring distance without contact has been studied many times.

In the known method from DE 280 S 877, a magnetic coupling is used which is dependent on the spacing of the two windings. However, it has the disadvantage of being highly sensitive to the excitation frequency of the winding. This is because this winding is operating at a constant frequency in a resonant circuit. Since the signals used are weak, this arrangement is sensitive to external interfering electromagnetic fields.

The method described in German Published Application No. 8287848 uses ferromagnetic materials to introduce magnetic flux into the interior of the sensing element. Therefore, the characteristics of the sensing element are affected by external magnetic fields, and limitations arise when measuring distances relative to the repulsion tracks of ferromagnetic materials.

The device for measuring the gap length described in DE 29 16 289 is disadvantageous for geometrical measurements, since it covers a large area of the grooved repulsion track.

All methods and devices known so far have in common that the detection signal for the interval is not reliably monitored. This means that if an error occurs in the sensing element, the detection signal will be a value that is the result of a longer distance between the sensing element and the repulsion track, but in reality that distance is shorter.

Each time a sensing element is inserted or used, certain limitations or conditions arise that impair accuracy.

When distance measurement is applied to a magnetic levitation device, the following errors occur. In other words, when the distance is short, a signal corresponding to a long distance is given, and the electromagnet is not strongly excited in order to narrow the distance, so a stronger magnetic stress is generated, causing the electromagnet and the magnetic repulsion track to come into contact. Let me do it! It is with Tsukasa. This presents a significant safety risk.

The object of the invention is to develop a measuring method and a device of the type mentioned at the outset, with which the detection function can also be reliably monitored for interval measurements.

This problem is solved as follows: the same voltage as the detection winding is applied to the second winding, that is, the reference winding, which is weakly magnetically coupled to the rail, and in order to measure the distance, the measurement During operation, a difference current is formed from the current in the sense winding and the current in the reference winding, and an additional impedance is periodically connected to the sense winding current circuit and the reference winding current circuit during each test operation. The reference winding is weakly magnetically coupled to the rails, and a current is generated in the reference winding circuit that is independent of the spacing between the tracks. Since the same voltage is applied to the reference winding as the sense winding and the current is independent of the interval, the difference current formed by the current in the sense winding and the current in the reference winding is the measured value for that interval. used as. By connecting an additional impedance to the sense winding circuit, the sense winding current is reduced and
Interval dependence is greatly reduced. Connecting an additional impedance to the reference winding current circuit reduces the corresponding reference winding current.

In this way, when the operating state is test, the difference between the sensed winding current and the reference winding current becomes less dependent on the spacing. If the entire circuit functions without error, the differential current when testing the operating state is characterized by a constant value, which changes only slightly when the interval is changed. Therefore, if the error that occurs becomes significant due to the corresponding deviation of the interval, this error can be detected. Furthermore, since in this arrangement a differential current is created by the sensing winding and the reference winding, it is advantageous to largely eliminate the influence of temperature on the winding resistance.

The method according to the invention is advantageously constructed in the following individual respects.

Good adjustment of the detection signal even when the material of the repulsion track changes is due to the fact that the effective and reactive components of the differential current are separated by a switch controlled by a periodic applied voltage, rectified, and finally By being smoothed.

The grooves in the repulsion track cause variations in the effective and reactive components of the differential current in the same way. This variation in the signal combined from both components is minimized as follows. The effect (waveform) of the groove is the same magnitude and opposite phase for both components, so the composite signal formed from both components is (
This is because both components of the differential current are determined so as to minimize the influence of the groove (for a given output signal). The determination of both components is determined by a geometric relationship, but is determined by whether they are strengthened or weakened by a temporally constant constant.

To check the connection, check whether the output signal adheres to a predetermined tolerance in the phase of the circuit in which the impedance is inserted. If this value is outside the allowed range,
The sensing element is faulty and generates a signal that interrupts the excitation of the electromagnet.

The additional impedance is determined so that it has the same value when the output signal is at a predetermined shortest interval during both measurement and inspection operations. This spacing is determined in such a way that it is not less than the safe spacing of the repulsive rails.

If, in the operating state of the measurement, the output signal falls below or equal to this minimum interval, a signal is generated which likewise interrupts the excitation of the electromagnet.

Two detection circuits are operated in sequence in order to increase safety regarding fault detection.

That is, the signal synchronously connecting the additional impedance and connecting the impedance of the first sensing element is tested for safety using the output signal of the second sensing element. The signal connecting the impedance of the second sensing element is tested for safety using the output signal of the first sensing element. If both signals are safe, a safe signal for the entire measuring circuit results.

is advantageous. In this case, the windings of the first sensing element and the windings of the second sensing element are operated independently, the former winding being operated at a different frequency than the latter winding.

Uncoupling can also be caused by the geometry of the windings themselves and/or by the arrangement of the windings.

An effective device for carrying out the method of the invention is constructed as follows: a winding is placed in a body which is open to a conductive repulsion track.

A second winding serving as a reference winding is placed below the detection winding of this body. An alternating current power supply is used as the source of the two winding currents. An additional impedance is connected to the detection winding and the reference winding, respectively, and a switch connected in parallel to this impedance is arranged. The difference current measurement position is provided in the common current circuit portion of both windings. The conductive body, which is open towards the repulsion track, shields the detection winding from the surrounding alternating magnetic field. The opening towards the repulsive track allows magnetic coupling to this track.

By installing the reference winding in the main body below the detection winding, the reference winding is placed in a shielded space.
It is further decoupled from the rail by a sensing winding. A synchronous switch which connects the additional impedance periodically and simultaneously can receive and receive measurement and test signals alternately at the difference current measurement point, so that continuous monitoring is ensured. The device can be advantageously constructed in individual respects as follows.

Since the reference winding has a smaller diameter than the detection winding, the magnetic coupling between the two windings will be the same at the main body, and in that case, the currents induced in the main body by both windings will be the same. Therefore, the reactions of resistance and actance on both windings are also equal. Therefore, both windings have the same electrical characteristics.

The detection winding is annular and wound in the same direction, and the reference winding is coiled and wound in alternate directions. Therefore, the electromagnetic coupling between the detection winding and the reference winding can be easily separated.

In the embodiment shown schematically in FIG. 1, the sensing winding 1 is directed towards the ferromagnetic repulsion track 7, and the sensing element 4 is arranged between the magnetic poles 5 of the electromagnet 6 in such a way that the distance to this track is determined. ing. The reference winding 2 arranged outside the sensing element 4 is directed toward the metal shielding plate 3 and is therefore not affected by the repulsion track 7. Furthermore, the metal shielding plate 3 is provided with a signal that shields the magnetic field of the sensing element 4 from the direction of the magnetic pole of the electromagnet 6, which is not shown, and is independent of the arrangement of the components of the sensing element 4 in the electromagnet 6. The purpose is to maintain the .

The detection winding 1 and the reference winding 2 are mainly manufactured using printed circuit board manufacturing technology.

FIG. 2 shows an electrical compensation circuit for the two detection and reference windings according to FIG. This circuit has a resistance R(s
) 12, which resistance depends on the spacing S and the temperature ■ in the case of the detection winding 1, and mainly on the temperature Φ in the case of the reference winding. This compensation circuit beam actance X(s
) 13, whose reactance depends on the spacing S for winding 1 and is independent of the spacing S for winding 2. Combined impedance Z9u resistance R(s) 1
It is formed by a parallel circuit of 2 and L-actance X(s) 13. Resistance R(s) 12 by power supply with voltage u8
The effective mill 1W1o is then the reactance X(s)
A reactive current 1B11 occurs at 13.6 This electrical quantity relationship is given by Equations 14 and 15.

This detection circuit is shown in FIG. The detection winding 2 with impedance Zs 9 is connected to 1 by a compensation impedance zvS 18, a switch 20, a power supply 8 and a difference current measurement location 16.
It forms two current closed circuits.

The reference winding 2, which likewise has an impedance ZR17, forms a further current closed circuit with a compensating impedance ZUR19, a switch 20°, a power supply 21 and a differential current measuring location 16. Both current circuits are interconnected by a difference current measurement location 16, and based on the specified phase positions of the power supplies US8 and U321, the difference current i,
-i 22 is detected.

FIG. 4 shows a circuit for examining equipotential signals for the effective and reactive components of the differential current f3-iR.

This circuit has a difference current signal i3-iR22 and a power supply US
8 has been introduced.

This difference current signal is-fB is introduced into a switch 24 that rectifies the effective component of this difference current and a switch 25 that rectifies the reactive component. The corresponding circuit signals are sent to comparator 2.
3 is introduced from the power source 8. A rectangular wave synchronized with the power supply 8 controls the switch 24, and a rectangular wave whose phase is 90° ahead of the above controls the switch 25. The output signal of the switch 24 is smoothed by a wave leaker 26 to provide a signal Uw28 corresponding to the effective component of the difference current.

The output signal of the switch 25 is smoothed by a wave leaker 27 to provide a signal UB29 corresponding to the reactive component of the difference current.

FIG. 5 shows the circuit of the sensing element 30 corresponding to FIG. 3, the circuit 31 according to FIG. It holds 34 sections. The significance of the adder circuit lies in the fact that the groove in the repulsion track 7 according to FIG. 1 exerts various influences on the signals Uw28 and UB29, and in this case the spacing-related influences are also exerted to the same extent on both signals. When the influence of the grooves is the least, it appears when appropriate evaluation processing is performed on the grooves of the repulsion rail using coefficients Kw32 and KH23.

The opening/closing unit 35 is controlled by a signal T338, and the capacitor 3
9 to form a holding portion.

A continuous interval signal 36 is therefore formed at the output of the device based on this circuit.

The principle for reliably checking the detection function is to excite the sensing element by the switching signal T137 generated by the clock generator 40 and to compare the waveform of the pulse produced when this element responds to the excitation with the waveform of the pulse produced by the excitation itself. be. The switch 20 according to FIG. 3 is then periodically controlled by the signal T137. As a result, the difference current 1B-iR2
2 is periodically switched between a measured value depending on the spacing to the repulsion track and a constant value adjusted by the additional impedances Z 18 and ZvR19 and corresponding to a predetermined shortest spacing. This periodic conversion is the addition point 3
4 is formed in the output signal -41. This signal U341
is introduced into comparator 42. In the comparator 42, the signal U
341 is compared with the voltage 51 of the resistor divider 54. Furthermore, the signal waveform 54 is generated by the switches 46, 47, 48,
are introduced into comparators 43.44.45.

The comparator converts the signal waveform 55 into the voltage U45 of the resistor divider 54.
0, U351, and U252.

FIG. 6 shows the temporal flow of the signal. Clock T657
During the operating state, signal 55 takes on the value of U153 with switch 47 being closed.

This causes the resistor divider 54 to be checked and the voltage U158 to be U2.
It is checked whether the value is below the threshold value formed at step 52.

While clock T756 is active, signal 55 is active at U349.
takes the value of This checks resistor divider 54 to check whether voltage U349 is above the threshold formed by U450. During the operation of clock T3, signal 55 assumes the value of U341. This checks whether the detection output signal is within the operating range determined by the thresholds .)U35:1 and 045+()-.

Clock T657 and T756 when the operating state is "inspection"
During this period, the same signal flow occurs as when the operating state is "measurement". During the period of clock T338, the detection signal Us
41 examines whether it is within the range indicated by threshold values U252 and U351. As a result, the detection circuit 30
and examine the electrical characteristics of the rectifier circuit 31.

Clock waveforms T117 and T388 shown in FIG.

A lock waveform 58 is generated, a clock waveform 60 is generated by a coupling circuit 61, and a comparison circuit 62 compares both clock waveforms 58 and 60. Comparator circuit 62 produces a logic output 63 which changes output state when the minimum interval falls below or when there is a fault in the sensing element.

Figure 7 shows a circuit with improved failure detection reliability. This circuit comprises two mutually independent electrical circuits according to FIG. 5, in this case one circuit having sensing elements 80.1. Detection and inspection circuit 64.1° Clock distribution circuit 40.1. Signal coupling circuit 61.1° Clock coupling circuit 59.1. and a comparison circuit 62.1. The other circuit corresponds to the above and has 80.2, 64.2, 40.2, 61.2.
, 59.2 and 62.2. These are further connected by a connecting circuit 65. The output signal 66 of the connecting circuit 65 changes its logic state if both circuits fail or if the final interval is exceeded.

This circuit generates both spacing-dependent signals 36.1 and 86.2.

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view of a spacing sensing element constructed from a sensing winding and a reference winding. FIG. 2 is an electrical compensation circuit diagram of a sensing winding having a spacing-dependent resistance and a spacing-dependent total inductance. Figure 3 shows the detection winding,
FIG. 2 is a principle electrical circuit diagram regarding the arrangement of a reference winding, power supply to a switchable additional inductance, and a difference current measurement location. FIG. 4 is a diagram schematically showing a circuit for separating and investigating the spacing-dependent reaction into effective and reactive components of the detection winding impedance. Figure 5 is a layout diagram schematically showing the detection function and the circuit for accurately testing whether the interval has fallen below a predetermined minimum interval by periodically switching the operating state between "measurement" and "inspection" alternately. It is. FIG. 6 shows time waveforms of clocks and signals for reliable functional monitoring and minimum interval monitoring. FIG. 7 is a schematic diagram of a dual circuit that improves the reliability of the detection circuit for irregularity and minimum interval monitoring. Code in the figure:

Claims (12)

[Claims] (1) In a measurement method in which an AC voltage is applied to the detection winding and the winding current, which depends on the distance between the repulsion rail and this detection winding, is used to measure the distance, a second Applying the same voltage as the detection winding to the reference winding, and using the difference current formed by the current of the detection winding and the current of the reference winding in the measurement state for the interval measurement, and inspecting. conductive repulsion rail, characterized in that additional impedances are periodically connected to the current circuit of the detection winding and the current circuit of the reference winding when the current circuit is in the state, and the difference current is used for testing the device. A method for measuring the distance between the magnetic sensor and the magnetic sensing element. (2) The effective component and the reactive component of the difference current are separated, rectified, and finally smoothed by a switch controlled by a periodically applied voltage. A distance measuring method according to claim 1. (3) The effective component and the reactive component of the difference current are determined so that the influence exerted on both components by the groove is the same in magnitude and in opposite phase, and is added to the output signal. The distance measurement method described in Range 2. (4) In the inspection state, it is checked whether the output signal is maintained within a predetermined tolerance range, and when the output signal exceeds the tolerance range, a signal is generated to interrupt the excitation of the electromagnet. Spacing measurement method described in Section. (5) The size of the additional impedance is determined so that the output signals in the measurement state and the inspection state become equal when they reach a predetermined shortest interval. interval measurement method. (6) In the measurement state, when the output signal corresponds to an interval equal to or smaller than the shortest interval, an opening/closing signal is generated which interrupts the excitation of the electromagnet. Interval measurement method. (7) For two sensing elements, the additional impedance is
are connected synchronously, the signal for connecting the impedance of the first sensing element uses the output signal of the second sensing element to confirm that there is no failure, and the signal for connecting the impedance of the second sensing element is Claims 1 to 6, characterized in that the output signal of the first sensing element is used to ascertain the absence of faults, and the safety signal of the entire measuring circuit is formed from the two fault-free signals.
The spacing measurement method according to any one of paragraphs. (8) Both of the sensing elements are spatially placed together, and the winding of the first sensing element is operated at a different frequency from the winding of the second sensing element to remove the electromagnetic coupling between the two windings. The distance measuring method according to claim 7, characterized in that: (9) The electromagnetic coupling between the windings of the first sensing element and the windings of the second sensing element is broken by the geometric shape and/or mutual arrangement of the two windings. A distance measuring method according to claim 7. (10) Apply an alternating voltage to the detection winding, use the winding current that depends on the distance between the repulsion rail and this detection winding to measure the distance above, and In a device using one detection winding built into the opening surface, a second reference winding (2) installed below the detection winding (1) in the main body (3); AC voltage power supply (8, 2
1), an additional impedance for the detection winding circuit and the reference winding circuit, respectively, a synchronous switch (20) placed in parallel with the impedance, and a common circuit for the detection winding (1) and the reference winding (2). A distance measuring device between a conductive repulsion track and a magnetic sensing element, comprising: a differential current measuring location (16) in a portion; (11) The distance measuring device according to claim 10, wherein the reference winding (2) has a winding frame cross-sectional area smaller than that of the detection winding (1). (12) The detection winding (1) is annular and wound in the same direction, and the reference winding (2) is wound in alternating directions. or the first
The distance measuring device according to item 1.