JP2002031134A - Sensorless magnetic levitation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a magnetic levitation device used in a magnetic bearing, etc., simple and inexpensive and to provide the magnetic levitation device by having a versatility in a control circuit part and separately designing a control circuit and a magnetic circuit. SOLUTION: An object to be levitated is disposed between a pair of electromagnets and an electric power is fed to a bridge circuit constituted of respective coils 9, 10 of these electromagnets and two 2-terminal circuit networks 11, 12 by an inverter circuit X. A potential difference (or a short circuit current) between bd is detected by a signal detector 13, is passed through a synchronization amplifier 16 synchronous to a switching action of the inverter circuit X and is returned to a control input 2 of the inverter circuit X through a controller 15. Thus, the object to be levitated is retained between the electromagnets.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sensorless magnetic levitation device.

[0002]

2. Description of the Related Art In a rotating machine rotating at a high speed, a magnetic bearing device (magnetic levitation device) is sometimes used in order to avoid friction of a bearing. The magnetic levitation device referred to here is a device that holds a levitation target, which is a magnetic material, using an attractive force or a repulsive force of an electromagnet so as not to contact another object. Alternatively, this is achieved by controlling the voltage. At this time, it is necessary to obtain information on the distance between the electromagnet and the floating object. However, using a sensor device for acquiring this information increases the size of the device and increases the cost. For this reason, several so-called sensorless magnetic levitation systems that do not use this sensor have been proposed, and the apparatus has been simplified.

[0003] For example, Japanese Patent Laid-Open Publication No. Hei 6-2294
19 ”, the current hysteresis control PWM (P
There has been proposed a control that utilizes the fact that when the inductance of the load of an inverter circuit changes, the switching frequency changes. When the two inverter circuits are used as power sources for the pair of electromagnets, the inductance value of the windings of the two electromagnets changes depending on the position of the floating object placed between the pair of electromagnets. Changes. The PLL so that the switching frequencies of the two inverter circuits match or have a certain ratio.
If the output current or voltage of the inverter circuit is controlled by (Phase-Locked Loop) control, a floating object can be held between the pair of electromagnets.

[0004] In addition, a sensorless magnetism using a differential transformer method as in the paper "Study on a differential transformer type self-sensing magnetic bearing" published in Transactions of the Japan Society of Mechanical Engineers (C), Vol. 63, No. 609 (1997-5). Ascent has also been proposed. This method is also a method utilizing the change in the inductance value of the pair of electromagnet windings described above. That is, in addition to the current necessary to levitate the object to be levitated, the alternating current (or AC voltage) is superimposed on the windings of both electromagnets, and the reverse of the two windings to the AC current (or AC voltage) is performed. By detecting a difference in electromotive force (or a difference in current), the position of a floating object is to be detected. This method uses a band-pass filter that passes only signals of the same frequency component as the superimposed AC current (or AC voltage), and superimposes the back electromotive force (or current flowing through the winding) on both ends of the winding of the electromagnet. A signal of a back electromotive force (or a current flowing through the winding) with respect to the generated AC current (or AC voltage) is extracted. At this time, when a PWM inverter circuit is used as a power source for the electromagnet, if the frequency of the harmonic current (or harmonic voltage) generated by the inverter circuit is constant, this current (or voltage) is converted to the above-described AC current (or AC voltage). For example, in Japanese Patent Application Laid-Open Publication No. 2000-060169, a current component that fluctuates according to an AC voltage of a winding is extracted by a band-pass filter. The difference between the back electromotive force signals (or current signals) of the two windings obtained in this way is obtained and multiplied by the superposed alternating current (or voltage) signal using a multiplier to obtain the position information of the floating object. Get. If the current or voltage of the electromagnet winding is controlled in accordance with this, the floating object can be held between the pair of electromagnets.

[0005]

In the above-described system based on PLL control, a plurality of inverter circuits for performing power control are required. Therefore, it cannot be said that sufficient simplification of the apparatus and reduction in cost have been achieved. . Furthermore, the characteristics of the current hysteresis control PWM inverter circuit, particularly the switching frequency, vary greatly depending on changes in the inductance value and resistance value of the load.
It is also affected by the electrical characteristics of the electromagnet and the material and shape of the floating object. Therefore, when designing the device, it is necessary to consider all of the control circuit, the electromagnet, and the object to be levitated, and to divert the control circuit and electromagnet of other magnetic levitation devices, exchange the object to be levitated, etc. Is often difficult.

On the other hand, in the above-described differential transformer system, since a band-pass filter is used for detecting a back electromotive force as position information, it is necessary to accurately adjust the center frequency. When the frequency changes, it becomes a big problem. Further, when the frequency of the AC current to be superimposed fluctuates, or when the switching frequency is not constant, P
When a WM inverter circuit is used, it is difficult to apply this method. Furthermore, since the multiplier is used, there is a disadvantage that it is difficult to reduce the cost of the control circuit. This method basically controls the differential transformer to be in an equilibrium state, so that it is necessary to add another mechanism to arbitrarily change the stable point of the floating object between the electromagnets. The change of the stable point is useful, for example, in a rotating mechanism using a magnetic bearing, to correct poor machining accuracy in mounting the bearing. However, even if a mechanism can be added to the control circuit to change the stable point, the stable point is not the equilibrium point of the differential transformer. There is a disadvantage that it is easily affected by

Accordingly, an object of the present invention is to propose a novel sensorless magnetic levitation device which does not have the above-mentioned disadvantages.

[0008]

According to a first aspect of the present invention, a magnetic material is held in a non-contact manner between a pair of electromagnets by utilizing the attraction or repulsion of the pair of electromagnets. In the device, a bridge circuit in which a series circuit in which respective windings of the pair of electromagnets are connected in series and a series circuit in which a two-terminal network is connected in series are connected in parallel, and an inverter circuit that supplies power to the bridge circuit. A detector for detecting a current or a voltage connected between the connection points of the two series circuits; a position detecting means for detecting a position of the magnetic body based on a detection output from the detector; Control means for controlling the inverter to a required position by controlling an inverter circuit based on the detection result of the means.

As a means for solving the second problem, a magnetic material is arranged between a pair of electromagnets, and the current of the windings of the electromagnets or the voltage applied to the windings is controlled so that the magnetic materials are connected to the pair of electromagnets. In a device that can be arranged without touching the electromagnet, a series circuit in which the windings of the pair of electromagnets are connected in series and a series circuit in which two two-terminal circuit networks are connected in series are connected in parallel. A bridge circuit is formed, and an output terminal of an inverter circuit as a power supply of the bridge circuit is connected to both ends of the parallel circuit, and an input of a detector for detecting a current or a voltage is provided between the middle points of the two series circuits. And the output of this detector is connected to the input of a synchronous rectifier that performs synchronous rectification in synchronization with the switching operation of the inverter circuit. Constructed by inputting the voltage or current control input terminal of the serial inverter circuit.

[0010] As a third means for solving the problem, in the above configuration, the output of the synchronous rectifier and the voltage or current control input terminal of the inverter circuit are modified to be connected via a low-pass filter. .

As a fourth means for solving the problem, instead of the synchronous rectifier, a sample-and-hold circuit that performs sampling in synchronization with the switching operation of the inverter circuit is used, and the input of the sample-and-hold circuit is used as the output of the detector. The output of the sample and hold circuit is used as the input of the controller.

The fifth means for solving the problem is the above first method.
In the means for solving problems 4 to 5, a current source circuit is connected in parallel to each winding of a pair of electromagnets.

As a sixth means for solving the problems, the above-mentioned first method is used.
The fourth aspect of the present invention is a configuration in which a second winding is applied to each of a pair of electromagnets, and a power supply circuit is individually or commonly connected to the second winding.

[0014] As a seventh means for solving the problem, the above-mentioned first method is used.
In the means for solving the problems of (1) to (6), a permanent magnet is used as the iron core of the electromagnet, or a part of the magnetic path is a permanent magnet.

According to an eighth aspect of the present invention, in the above aspect, the detector is a primary winding connected between a connection point of two series circuits and an output of the detector. The transformer has a secondary winding and a secondary winding.

According to a ninth problem solving means, in the above problem solving device, one or both of the two-terminal network has a variable impedance.

[0017]

First Embodiment A first embodiment of the present invention will be described with reference to FIGS.

In FIG. 1, windings 9 and 1 of a pair of electromagnets are shown.
0 and two two-terminal circuits 11 and 12 constitute a bridge circuit, and the inverter circuit X is used as a power supply for the bridge circuit. As an example of the two two-terminal circuits 11 and 12, resistors having the same resistance are used here, but a network composed of a combination of resistors, inductances, capacitors, and the like can also be used. The inverter circuit X includes, for example, a bipolar transistor having a reverse conducting diode, a MOS-FET, an IG
Switching elements 4a and 4b such as BT and DC power supplies 5a and
5b (both have the same voltage). The conduction or non-conduction command signal to the switching element has an opposite relationship between the inverter circuit control input terminal 2 and the output of the triangular wave oscillator 8 by the negating circuit 7. Has been given. A detector 13 for detecting a potential difference between bd or a current flowing through bd is provided in the bridge circuit, and an output of the detector 13 is a signal corresponding to a detected voltage or a current, for example, a voltage proportional to them. It is something that can be done. For this purpose, an insulating amplifier, a differential amplifier or the like can be used. This output is guided to a synchronous rectifier 16 in which the sign of the amplification degree switches in synchronization with the switching of the inverter circuit X. It is known that a synchronous rectifier can be constituted by, for example, an operational amplifier B1, an analog switch B2, and resistors Ra, Rb, and Rc (the same resistance value) as shown in FIG. In this case, the input is B
3. The synchronization input is B4 and the output is B5. For the synchronization of the synchronous rectifier, the voltage between the terminals of the inverter circuit output terminals 1a and 1b may be referred to, but in this embodiment, the output of the comparator 6 is referred to. The output B5 of the synchronous rectifier 16 is guided to the controller 15, and the output is fed back to the inverter circuit control input terminal 2 described above. It is assumed that the controller 15 is well known such as proportional, proportional integral, proportional derivative, proportional integral derivative, and the like. The relationship between the electromagnet and the object to be levitated is as shown in FIG. That is, the electromagnet M including the windings 9 and 10
A magnetized levitation object 14 smaller than the interval is arranged between a and Mb, and the magnetic poles of both electromagnets and the levitation object are placed so as to face each other. It is assumed that the movement of the flying object has a degree of freedom only in the direction of the arrow in the figure.

The operation of the first embodiment will be briefly described below. Here, in FIG.
Are assumed to be the same. When the object to be levitated 14 is placed so that the gap between the electromagnet Ma and the object to be levitated 14 is equal to the space between the electromagnet Mb and the object to be levitated 14, the inductance value between the terminals of the windings 9 and 10 is the same. Becomes The position of the flying object 14 is defined as a center point. Normally, the magnetic permeability of the iron core of the electromagnet and the object to be levitated is several hundred to several thousand times larger than the magnetic permeability of the air gap. Therefore, when the object to be levitated approaches the electromagnet Ma side, the winding 9
The inductance at both ends becomes larger than that at both ends of the winding 10, and conversely, as it approaches the electromagnet Mb side, the inductance at both ends of the winding 10 becomes larger. Therefore, when the flying object 14 is at the center point, the bridge circuit of FIG. 1 including the windings 9 and 10 is in a balanced state, and v2 = 0 or i2 = 0. Here, v2 and i2
Means a bd open circuit voltage and a bd short circuit current, respectively. Also, when the flying object 14 is closer to the electromagnet Ma side than this position, when the bridge input voltage v1 is v1> 0, v2 <0 and i2 <0, v1 <0.
, V2> 0 and i2> 0. Conversely, when approaching the electromagnet Mb side, when v1> 0, v2> 0 and i2>
When 0 and v1 <0, v2 <0 and i2 <0. Figure 1
Since the binary output of the comparator 6 represents the polarity of the output voltage of the inverter circuit X, that is, the sign of v1,
When the output of the detector 13 that detects a signal proportional to v2 or i2 is input to the synchronous rectifier 16 that performs synchronous rectification in synchronization with the binary output, the output signal f is output from the floating object to the electromagnet Ma side. In case of deviation f> 0 When the object to be levitated is shifted toward the electromagnet Mb f <0 When the object to be levitated is at the center point, f = 0 can be set. Further, the absolute value of f increases as the distance from the center point increases. Therefore, it is clear that the position of the flying object can be known from this signal. In addition, since the detection signal f is not affected by the switching of the inverter circuit in principle, even when the switching frequency changes, information on the position of the flying object is given. On the other hand, when a current flows from a to c in the winding of FIG. 3, the floating object is attracted to the electromagnet Ma and repelled by the electromagnet Mb, and receives a force in the direction of the electromagnet Ma. Conversely, when a current flows from c to a, the levitating object receives a force in the direction of the electromagnet Mb. Thus, the signal f is
If the feedback is made to the inverter circuit control input terminal 2 for controlling the output voltage of the inverter circuit via the controller 15, the current of the windings 9 and 10 is operated, and control can be performed so that the object to be levitated is held at the center point. That is clear.

Also, as shown in FIG. 4, an inverter circuit having a current control system using a controller C3 such as a current detector C1, an error amplifier C2, and a proportional-integral-differential controller is replaced with the inverter circuit X shown in FIG. If used, two-terminal network 1
If the impedances of the windings 1 and 12 are set sufficiently larger than the impedances of the windings 9 and 10 (for example, 10 times or more of the winding reactance at the switching frequency),
The current of the two-terminal network can be neglected, the current of the winding can be directly controlled by a command from the controller 15, and control can be performed so as to maintain the levitating object at the center point as in the above-described case. Is clear. Further, as shown in FIG. 5, the conduction and non-conduction of the switching elements 4c and 4d are respectively set to 4a and 4b.
The same effect can be expected when the inverter circuit that outputs the midpoint of 4a and 4b and the midpoint of 4c and 4d is replaced with X in FIG. In addition, as in FIG. 6, similarly to FIG. 4, the same effect can be expected even with an inverter circuit having a current control system using a controller C3 such as a current detector C1, an error amplifier C2, and a proportional-integral-differential controller. it is obvious.

[0021]

Embodiment 2 Next, a second embodiment of the present invention will be described with reference to FIG. The control circuit of the present embodiment includes:
The output terminal B5 of the synchronous rectifier of FIG. 1 and the input of the controller 15 are connected via a low-pass filter L1, and other configurations are the same as those of the first embodiment.

It is generally known that switching between conduction and non-conduction of a semiconductor switching element used in an inverter circuit or the like requires some time. Due to this time delay,
The output of the synchronous rectifier 16 of FIG. 1 shown in the first embodiment is
Although the position information of the object to be levitated is given, the sign changes when the conduction or non-conduction of 4a and 4b is switched. When a switching element having a noticeable time delay is used, the sign change may be input to the controller 15 as noise, and in some cases, the controllability is deteriorated or the control becomes impossible. Since this sign change occurs every time the state of the switching element of the inverter circuit X changes, the pass band of the low-pass filter is changed to the switching frequency of the inverter circuit X (that is, the oscillation frequency of the triangular wave generation circuit 8).
In the following, removal of this noise can be expected, and even if such a switching element is used, control can be performed so that the flying object is held at the center point.

Although not shown in the drawing, when a delay circuit is inserted between the synchronous signal output terminal 3 for switching and the synchronous signal input terminal B4 of the synchronous rectifier, the switching between the synchronous rectifier 16 and the switching elements 4a and 4b is performed. However, although synchronized, a time lag occurs. For this reason, the output signal of the synchronous rectification indicates that the conduction of the switching elements 4a and 4b and
A sign change occurs at the time of non-conductivity switching. When this signal is passed through a low-pass filter, time differentiation by a conventionally known synchronous rectifier is performed, and a signal including an element of time differentiation of the position of the flying object is obtained. With this configuration, the effect of performing the differential control can be expected without using a differentiator for the controller 15.

[0024]

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG.

In the first embodiment, a synchronous rectifier is used, and a deviation from the center point of the object to be levitated is detected based on an output signal of the synchronous rectifier to control the object to be levitated. As shown in FIG. 7, a sample-and-hold circuit 16a that performs sampling in synchronization with the switching operation of the inverter circuit X is used. This input is used as a detection signal from the detector 13, and the output is used as an input to the controller 15. Except for this change, the configuration is the same as that of the first embodiment. The sampling timing is obtained from the switching synchronizing signal output terminal 3 of the inverter circuit. For example, if the binary output is “1” and “0”, sampling is performed at “1”. When the value is "0", an operation of holding the sampled data is performed.

As described in the first embodiment, when the object to be levitated 14 in FIG. 3 is at the center point, the bridge circuit in FIG. 7 including the windings 9 and 10 is in a balanced state, and v2 = 0 or i2 = 0. (V2 and i2 are bd
Open-circuit voltage and short-circuit current between bd)
4 is closer to the electromagnet Ma side than this position, when the bridge input voltage v1 is v1> 0, v2 <0 and i2
When <0 and v1 <0, v2> 0 and i2> 0. Conversely, when approaching the electromagnet Mb side, when v1> 0, v2>
0 and i2> 0 and v2 <0 when v1 <0
Becomes That is, if the output from the detector 13 is sampled only when either v1> 0 or v1 <0, deviation information including the direction from the center point of the flying object can be obtained. Therefore, detailed explanation is omitted,
Obviously, with this configuration, control can be performed so that the flying object is held at the center point. When the present control circuit is constructed using a digital controller, the sample and hold circuit provided in the digital controller is regarded as the sample and hold circuit 16a, and the sampling is synchronized with the switching of the inverter circuit, and v1>
It may be performed when either 0 or v1 <0.

[0027]

Embodiment 4 Next, a fourth embodiment of the present invention will be described with reference to FIGS. 1, 3, and 8. FIG.

In the fourth embodiment, the windings 9 and 10 of FIG. 1 use the circuit of FIG. That is, in the first embodiment, the electromagnet and the object to be levitated in FIG. 3 are used, but in this embodiment, there is no difference except for the configuration shown in FIG. A1 and A2 are current source circuits, both supplying a DC current Ic. The flying object 14a is a magnetic material that is not magnetized, and its mechanical degree of freedom is limited to the direction of the arrow. Here, assuming that the impedance of the two-terminal network is sufficiently larger than the impedance of the windings 9 and 10 (for example, at least 10 times the reactance of the winding at the switching frequency of the inverter circuit), the current of the two-terminal network can be ignored. Think. If the inverter circuit X of FIG. 1 supplies a current I to the bridge circuit, the windings 9 and 10
Respectively, Im1 = Ic + I Im2 = Ic-I. Further, when the absolute value of I is equal to or less than Ic, I
m1 and Im2 are non-negative and both currents are differential with respect to changes in I. Therefore, by manipulating the current I, the electromagnet M
Since the difference between the suction forces a and Mb can be adjusted, the force applied to the flying object can be controlled in both directions. This controllability is equivalent to FIG. 3 described in the first embodiment. Therefore, although detailed description is omitted, it is apparent that control can be performed so that the magnetic body on which the floating object is not magnetized is held at the center point between the electromagnets.

[0029]

Fifth Embodiment Next, a fifth embodiment of the present invention will be described with reference to FIGS. 1, 3, and 9. FIG.

In the fifth embodiment, the circuits shown in FIG. 9 are used as the windings 9 and 10 in FIG. That is, in the first embodiment, the electromagnet and the object to be levitated in FIG. 3 are used, but in this embodiment, there is no difference except for the configuration shown in FIG. A3 and A4 are bias magnetic flux windings having the same number of turns and sharing the same magnetic path as the windings 9 and 10, respectively, and being wound so as to be harmonic and differential, respectively.
Is the power supply circuit. The flying object 14a is a magnetic material that is not magnetized, and its mechanical degree of freedom is limited to the direction of the arrow. When a constant current is supplied from the power supply A5, the magnetomotive force generated in the winding 9 and the winding A3 is added by the iron core, and the magnetomotive force generated in the winding 10 and the winding A4 is subtracted. On the other hand, the magnetomotive force applied to each iron core changes differentially. Therefore, if the current of the winding A4 is set so that the magnitude of the magnetomotive force generated by the winding A4 is always larger than that of the winding 10, the change in the attraction force of each electromagnet becomes Similarly to the case of the fourth embodiment, if the current I is manipulated, the difference between the attraction forces of the electromagnets Ma and Mb can be adjusted, so that the force applied to the floating object can be controlled in both directions. Therefore, a detailed description is omitted, but a magnetic body in which the object to be levitated is not magnetized,
As in the fourth embodiment, it is apparent that control can be performed so as to maintain the center point between the electromagnets. In the present embodiment, two bias magnetic flux windings are connected in series to supply current from a common power supply. However, in the case where current is supplied from a common power supply in parallel, or when individual power supplies are used. Needless to say, the same effect can be obtained.

[0031]

Embodiment 6 Next, a sixth embodiment of the present invention will be described with reference to FIGS. In the sixth embodiment, the windings 9 and 10 of FIG.
Is inserted. That is, in the first embodiment, the electromagnet and the object to be levitated in FIG. 3 are used, but in this embodiment, there is no difference except for the configuration shown in FIG. Permanent magnets A6 and A7 are attached to each electromagnet, and the magnetic force of the permanent magnet and the magnetic force generated by the pair of electromagnets are added and subtracted, respectively. The flying object 14a is a magnetic material that is not magnetized, and its mechanical degree of freedom is limited to the direction of the arrow. In this case, the permanent magnet functions in the same manner as the bias magnetic flux winding of the fifth embodiment. Here, if a permanent magnet is selected so that the magnetic force of the permanent magnet is always larger than the magnetic force generated by the electromagnet, or if the operating range of the current of the electromagnet is limited, detailed description is omitted, Is equivalent to that of the fifth embodiment, and it is apparent that control can be performed so that the magnetic body on which the object to be levitated is not magnetized is held at the center point between the electromagnets. Needless to say, the same result can be obtained even when the magnetic path itself of the electromagnet is a permanent magnet.

[0032]

Seventh Embodiment Next, a seventh embodiment of the present invention will be described with reference to FIGS.

FIG. 11 shows a seventh embodiment of the present invention, in which an insulating transformer 13a is used as the detector 13 in FIG. The primary winding of the insulating transformer 13a is connected between bd of the bridge circuit, and one end of the secondary winding is used as a reference and the other end is used as a detection signal output terminal. The detector 13 aims at measuring whether or not the bridge circuit is in an equilibrium state. To obtain the information, if only the AC component of the voltage or current between the bd and the bd of the bridge circuit is detected. Good. Therefore, it is possible to use an insulating transformer as a detector. In the circuit of the present embodiment, the inverter circuit always performs a switching operation while the device is operating, so that the AC voltage component is always input to the bridge circuit. Therefore, the state of the bridge circuit can always be known via the insulating transformer 13a. Therefore, although detailed description is omitted, it is clear that the position of the flying object can be controlled by the configuration of the present embodiment as in the other embodiments.

[0034]

[Eighth Embodiment] Next, an eighth embodiment of the present invention will be described with reference to FIGS.

FIG. 12 shows an eighth embodiment of the present invention, in which the two-terminal circuit networks 11, 12 in FIG. 1 are replaced by variable resistors R1, R2. In the first embodiment, two two-terminal networks are resistors having the same resistance value.
In the present embodiment, a configuration is shown in which by changing these resistance values, the equilibrium point of the bridge circuit can be changed and the floating position of the floating object can be changed. In FIG. 3, the inductance between both ends of the windings 9 and 10 when the flying object 14 is brought into contact with the electromagnet Ma is represented by La, respectively.
1, Lb1, and when the inductance between both ends of the windings 9 and 10 when the object to be levitated 14 is brought into contact with the electromagnet Mb is La2 and Lb2, respectively, a range of La1 @ Lb1> R1. If the resistance value is selected, the object to be levitated can be arranged at an arbitrary position between the pair of electromagnets. In this embodiment, the two-terminal networks 11 and 12 are variable resistors.
It goes without saying that variable inductance and variable capacitance can also be used. Similar effects can be obtained by using an element whose impedance can be controlled by an external signal, such as a transistor, as these elements.

[0036]

According to the magnetic levitation device of the present invention, the problem of the sensorless magnetic levitation device based on the PLL control exemplified as the prior art, that is, since a plurality of inverter circuits are used, the simplification can be sufficiently performed. And the disadvantage of using the current hysteresis control PWM inverter circuit, that is, the problem that it is necessary to design in consideration of all of the control circuit, the electromagnet, and the floating object. As a result, not only can the price be reduced, but also the versatility can be imparted to the control circuit, so that the control circuit and the magnetic circuit can be separately designed and provided separately. In addition, since a band-pass filter is not used to detect the position of the object to be levitated, it is difficult to set the center frequency of the band-pass filter and problems related to fluctuations in the center frequency, which are present in sensorless magnetic levitation using the differential transformer method. Is eliminated. In the embodiment of the present invention, it is possible to select whether to use a synchronous rectifier or a sample and hold circuit.However, if the former is selected, the control circuit can be inexpensively used without using the multiplier used in the differential transformer method. Can be configured. In addition, by using a low-pass filter at the output of the synchronous rectifier, noise in the output of the synchronous rectifier due to the time delay of the switching element can be removed, and the time differential operation of the position of the floating object can be performed together with the delay circuit. This makes it possible to include differential control without using a differentiator. When the present control circuit is constructed using a digital controller, the latter method in which the sample and hold circuit provided in the digital controller can be used as it is becomes useful.

Further, by adding a current source circuit to the winding of the electromagnet, it is possible to control a non-magnetized magnetic body. The same effect applies a second winding to the electromagnet,
It is also possible to connect a power supply circuit individually or commonly to one winding. Similar results can be obtained by using a permanent magnet as the core of the electromagnet or by using a permanent magnet as a part of the magnetic path. In this case, there is an advantage that an additional power supply is unnecessary.

On the other hand, when a transformer having a primary winding as an input and a secondary winding as an output is used as a detector for detecting the state of a bridge circuit inside the device, an insulation amplifier, a differential amplifier, etc. This has the advantage that the control circuit can be constructed at a lower cost as compared with the case where the above circuit is used. Further, by setting one or both of the two-terminal network in the bridge circuit to have a variable impedance, the position of the flying object can be controlled. This means that it can also be used as a kind of actuator for driving a floating object. In addition, when installing the electromagnet, if the mechanical accuracy of the installation is poor, there is an advantage that the accuracy of the installation can be corrected by changing the floating position.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a basic control circuit in first to eighth embodiments of a sensorless magnetic levitation device according to the present invention.

FIG. 2 is a circuit diagram showing a circuit example of a synchronous rectifier.

FIG. 3 is a connection diagram showing an electromagnet part and a levitation object used in the first embodiment of the sensorless magnetic levitation apparatus according to the present invention.

FIG. 4 is a circuit diagram of an inverter circuit having a current control system that can be used in place of the inverter circuit X used in FIG.

FIG. 5 is a circuit diagram of an inverter circuit that can be used in place of the inverter circuit X used in FIG.

6 is a circuit diagram of an inverter circuit having a current control system that can be used in place of the inverter circuit X used in FIG.

FIG. 7 is a circuit diagram of a control circuit portion of a sensorless magnetic levitation device according to a third embodiment of the present invention.

FIG. 8 is a connection diagram showing an electromagnet portion and a levitation object used in a fourth embodiment of the sensorless magnetic levitation device according to the present invention.

FIG. 9 is a connection diagram showing an electromagnet portion and a levitating object used in a sensorless magnetic levitation apparatus according to a fifth embodiment of the present invention.

FIG. 10 shows a sixth embodiment of the sensorless magnetic levitation apparatus according to the present invention.
FIG. 6 is a connection diagram showing an electromagnet part and a floating object used in the embodiment.

FIG. 11 is a seventh view of the sensorless magnetic levitation device according to the present invention;
FIG. 9 is a circuit diagram of the control circuit portion of the embodiment according to the present invention, in which an insulating transformer is used for detecting the state of the bridge circuit.

FIG. 12 is an eighth view of the sensorless magnetic levitation device according to the present invention;
FIG. 9 is a circuit diagram of a control circuit portion of the embodiment of FIG. 7 when a variable resistor is applied as a two-terminal network of a bridge circuit.

[Explanation of symbols]

1a, 1b Inverter circuit output terminal 2 Inverter circuit control input terminal 3 Switching synchronization signal output terminal 4a, 4b, 4c, 4d Switching element 5, 5a, 5b DC power supply 6 Comparator 7 Negation circuit 8 Triangular wave generation circuit 9, 10 Electromagnet Winding 11, 12 Two-terminal network 13 Voltage (current) detector 13a Insulation transformer 14 Magnetized floating object 14a Non-magnetized floating object 15 Controller 16 Synchronous rectifier 16a Sample hold circuit B1 Operational amplifier B2 Analog switch B3 Signal input terminal of synchronous rectifier B4 Synchronous signal input terminal of synchronous rectifier B5 Rectified signal output terminal Ra, Rb, Rc Resistance (resistance values are all the same) Ma, Mb Electromagnet C1 Current detector C2 Error amplifier C3 Controller for current control L1 Low-pass filter A1 A2 current source circuit A3, A4 bias flux winding A5 bias flux winding of the power supply circuit A6, A7 permanent magnets R1, R2 two-terminal resistor and the resistance value of the network

Claims (9)

[Claims] 1. An apparatus for holding a magnetic body in a non-contact manner between a pair of electromagnets by utilizing attraction or repulsion of the pair of electromagnets, wherein respective windings of the pair of electromagnets are connected in series. A bridge circuit in which a series circuit and a series circuit in which a two-terminal network is connected in series are connected in parallel, an inverter circuit that feeds the bridge circuit, and a current or a current connected between the connection points of the two series circuits. A detector for detecting a voltage, a position detecting means for detecting a position of the magnetic body based on a detection output from the detector, and controlling the inverter circuit based on a detection result by the position detecting means to obtain the magnetic body. And a control means for controlling the position of the sensorless magnetic levitation. 2. A magnetic body is disposed between a pair of electromagnets, and a current of a winding of the electromagnet or a voltage applied to the winding is controlled to distribute the magnetic body without touching the pair of electromagnets. In this device, a bridge circuit is formed by connecting in series a series circuit in which respective windings of the pair of electromagnets are connected in series and a series circuit in which two two-terminal networks are connected in series. An output terminal of an inverter circuit as a power supply of this bridge circuit is connected to both ends of the circuit, an input of a detector for detecting a current or a voltage is connected between the middle points of the two series circuits, and an output of the detector is provided. Is connected to the input of a synchronous rectifier that performs synchronous rectification in synchronization with the switching operation of the inverter circuit, and the output of a controller having the output of the synchronous rectifier as an input is the voltage of the inverter circuit or A sensorless magnetic levitation device characterized by inputting to a current control input terminal. 3. The sensorless magnetic levitation device according to claim 2, wherein the output of the synchronous rectifier and the voltage or current control input terminal of the inverter circuit are connected via a low-pass filter. apparatus. 4. The sensorless magnetic levitation device according to claim 2, wherein a sample-and-hold circuit that performs sampling in synchronization with a switching operation of the inverter circuit is used instead of the synchronous rectifier, and an input of the sample-and-hold circuit is used as a detector. A sensorless magnetic levitation device, wherein the output is used as an output, and the output of the sample and hold circuit is used as an input of a controller. 5. The sensorless magnetic levitation device according to claim 1, wherein a current source circuit is connected in parallel to each winding of the pair of electromagnets. 6. The sensorless magnetic levitation device according to claim 1, wherein a second winding is applied to each of the pair of electromagnets, and a power supply circuit is individually or commonly applied to the second winding. A sensorless magnetic levitation device, which is connected. 7. The sensorless magnetic levitation apparatus according to claim 1, wherein a permanent magnet is used as an iron core of the electromagnet, or a part of the magnetic path is a permanent magnet. 8. The sensorless magnetic levitation device according to claim 1, wherein the detector includes a primary winding connected between a connection point of two series circuits and an output of the detector. A sensorless magnetic levitation device, characterized in that the transformer is provided with a primary winding and a secondary winding. 9. The sensorless magnetic levitation device according to claim 1, wherein one or both of the two-terminal network has a variable impedance.