JPH05122893A - Linear dynamic magnetic bearing device - Google Patents

Abstract

PURPOSE:To move full shift range stably by controlling electric current of an axial electromagnet group bearing a movable body moving in an axial direction along a static body in a state of non-contact by output of radial position detectors, and providing axial driving force in accordance with an axial moving amount. CONSTITUTION:A movable body 4 moving along a static body 1 is levitated by a plurality of electromagnetic forces 10a and 10b of which a magnetic bearing device 10 is constituted and is borne in a state of non-contact. While, an electromagnet generation mechanism 20 constituted of an outside cylindrical section 7, a cylindrical hollow section 6, a circular permanent magnet 21 and a voice coil 22 is provided at the left end of the movable body 4, and thrust is applied to the movable body 4 in a state of non-contact. Excitation current of the electromagnets 10a and 10b is controlled by displacement detected by a plurality of radial position detector groups 15a-15d (15a is only illustrated). An axial moving amount is detected by an inclined plane of an auxiliary plate 24 attached to the movable body 4 and a moving amount detector 26, and the electric current of the voice coil 22 is controlled. According to the constitution, smooth movement is stably made through full shift range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear dynamic magnetic support device suitable for supporting elements such as a scanning mirror of an optical interferometer and a precision linear table which require highly accurate positioning.

[0002]

2. Description of the Related Art As is well known, a supporting device for supporting a scanning mirror or a precision linear table of an optical interferometer is required to have a function of accurately positioning them. In order to cope with such a demand, usually, a structure is adopted in which a movable body which is guided by a guide mechanism and smoothly moves linearly is provided, and the movable body is moved by a precision ball screw feeding mechanism.

However, the supporting device adopting such a mechanical positioning system has a problem that the constituent parts must be processed with extremely high accuracy. Further, even if the parts are machined with high accuracy, it is not possible to completely avoid the influence of backlash of the ball screw, etc., so that the positioning accuracy is limited. Further, in a special environment such as a harsh temperature environment or a high vacuum, it is difficult to use for a long time due to problems such as lubrication of the guide mechanism and the ball screw.

Therefore, in order to solve such a problem, a method is conceivable in which the movable body is levitated by a magnetic force, that is, a magnetic bearing in a completely non-contact manner.

However, even the so-called linear dynamic magnetic support device using the magnetic bearing has the following problems. That is, in this linear dynamic magnetic support device, the position of the center of gravity of the movable body with respect to the magnetic bearing also moves as the movable body moves in the axial direction. Therefore, there is a problem that the magnetic support control system becomes unstable. Furthermore, when a stationary body that supports a movable body is excited by external vibration, the movable body causes a coupled motion due to interference between its center-of-gravity motion and rotational motion around the center of gravity, which causes a problem that positioning accuracy cannot be maintained. is there.

[0006]

As described above, even if the linear dynamic magnetic support device is constructed by simply using the magnetic bearings, the magnetic support control system becomes unstable when the movable body is largely moved in the axial direction. In addition, vibrations applied from the outside cause a coupled motion in the movable body, making it difficult to perform highly accurate positioning.

Therefore, an object of the present invention is to provide a linear dynamic magnetic support device capable of realizing stable support characteristics over the entire axial movement distance of a movable body and stability against disturbance.

[0008]

In order to achieve the above object, in a linear dynamic magnetic support device according to the present invention, a stationary body,
A movable body that is arranged in the vicinity of the stationary body so as to be movable in the axial direction, and a plurality of electromagnet groups that are provided at a position surrounding the movable body of the stationary body and at two or more positions in the axial direction,
Radial position detecting means for detecting the radial position of the movable body, and magnetic support for supporting the movable body in a non-contact manner by adjusting the magnetic force of the plurality of electromagnet groups based on the information of the position detecting means. Control system, axial movement amount detecting means for detecting the axial movement amount of the movable body, driving means for applying an axial movement force to the movable body, and information obtained by the axial movement amount detecting means And a control parameter adjusting means for adjusting the control parameter of the magnetic support control system intermittently or continuously. Specifically, the control parameter adjusting means uses the level of the steady excitation current flowing in the electromagnet group as a control parameter, the equilibrium condition of the force applied by the electromagnet group, the center of gravity of the movable body, and the rotational movement around the center of gravity. Select a level that satisfies the mutual decoupling conditions. In addition to this, the model of the magnetic support system is updated according to the information obtained by the axial movement amount detecting means, and the compensation for stabilizing the magnetic support system is performed from the result of the updating means of the control model. Updating the parameters is also effective.

[0009]

Since the control parameters of the magnetic support control system are updated based on the axial moving distance of the movable body, a stable supporting system can be realized over the axial moving range of the movable body. Furthermore, if the control parameters are adjusted so as to satisfy the decoupling condition, the control system can be designed independently of the center-of-gravity motion and the rotational motion. Against this, the countermeasure becomes relatively easy. That is, since there is theoretically no influence on the rotational motion due to the center-of-gravity disturbance, when performing precise positioning of the rotational motion of the movable body, the natural frequency of the rotational motion system is sufficiently high and By reducing the frequency of vibration, the transmitted vibration can be reduced and the positioning accuracy can be sufficiently ensured. On the other hand, in the case of performing precise positioning of the center-of-gravity movement, it can be dealt with by suppressing the resonance of the support system and promptly preventing the vibration.
If the decoupling support is adjusted with a steady excitation current and the support characteristics are adjusted with compensation parameters, the control system design of the center of gravity motion and the rotary motion can be calculated individually, and the calculation is not complicated, so it is easy to And it can be carried out accurately.

[0010]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows a linear dynamic magnetic supporting device according to an embodiment of the present invention, which is a linear dynamic magnetic supporting device for supporting a scanning mirror of an optical interferometer for measuring a gas distribution state. ..

In the figure, 1 indicates a stationary body.
The stationary body 1 is composed of a base 2 and a cylindrical body 3 made of a non-magnetic material and fixed to the base 2. The movable body 4 formed in a substantially columnar shape is provided in the cylindrical body 3.
Is arranged so as to be movable in the axial direction.

The movable body 4 is made of a magnetic material, and the right half of the figure is hollow. In addition, the movable body 4
In the left half of the figure, the central rod portion 5 and the cylindrical hollow portion 6 are shown.
And the outer cylindrical portion 7 are concentrically arranged. A mirror support 8 is attached to the right end of the movable body 4 in the figure, and a scanning mirror 9 is fixed to the mirror support 8.

Main elements 10a and 10b of the magnetic support device 10 for supporting the movable body 4 in a non-contact manner with the movable body 4 and the cylindrical body 3 are provided at two axial positions, that is, arrows in the figure. A,
They are provided at the positions indicated by B, respectively.

The magnetic support device 10 is of a suction support type to which a magnetic bearing is applied, and of the main elements 10a and 10b thereof,
When the main element 10a provided at the position indicated by the arrow A is shown as a representative, it is configured as shown in FIG. That is, the main element 10a is circumferentially attached to the inner peripheral surface of the tubular body 3 by 90
Yokes 11a, 11b, 11c, 11d fixed with the magnetic pole surfaces facing the axis of the movable body 4 with a space between them,
Coil 12 attached to these yokes to form an electromagnet
a, 12b, 12c, 12d and the convex magnetic poles 13a, 13 formed on the outer peripheral surface of the movable body 4 at intervals of 90 degrees in the circumferential direction and extending over substantially the entire length of the movable body 4.
b, 13c, 13d and a non-magnetic body fixed between the convex magnetic poles so as to extend over substantially the entire length of the movable body 4, for example, a thin plate of stainless steel, and used for radial displacement detection. Flat surfaces 14a, 14b, 14c, 1
4d and each of the yokes are fixed to the cylindrical body 3 so as to detect the distance between each flat surface and each of them, for example, a volume change detection type detector such as an eddy current type detector. And position detectors 15a, 15b, 15c and 15d.

Each yoke 11a, 11b, 11c, 11d
1 includes two magnetic pole surfaces 16a and 16b as shown in FIG. 1 as a representative of the yoke 11c.
The a and 16b are fixed to the inner surface of the cylindrical body 3 so as to be arranged in the axial direction. Each yoke 11a, 11b, 11c, 11
coils 12a, 12b, 12c, 12d mounted on d
Are each composed of a bias coil 17 and a control coil 18. The control coils 18 mounted on the yokes facing each other across the movable body 4 are connected in series so as to generate magnetic fluxes in the same direction.

Each yoke 11a, 11b, 11c, 1
The axial center line of the movable body 4 is set so that the two magnetic pole surfaces 16a and 16b of 1d and the magnetic pole surfaces of the four convex magnetic poles 13a, 13b, 13c and 13d provided on the movable body 4 do not come into contact with each other by rotation. It is formed in a cylindrical curved surface centered at the center.
The main element 10b has the same structure as the main element 10a.

On the left side of the movable body 4 in FIG. 1, an electromagnetic force generating mechanism 20 is provided to the movable body 4 and the cylindrical body 3 to selectively apply a moving force in the axial direction to the movable body 4 in a non-contact manner. It is provided. This electromagnetic force generation mechanism 20 is fixed to the inner peripheral surface of the outer tubular portion 7 on the open end side and is annularly magnetized in the radial direction, as in a known voice coil motor. And a cylindrical coil 22 that is formed into a cylindrical shape and is fitted into and attached to the cylindrical hollow portion 6 in a non-contact manner. The base end of the tubular coil 22 is fixed to the tubular body 3. Touchdown bearings 23a, 23b, and 23c are provided between the main elements 10a and 10b and on the left side of the stationary body 1 in FIG. 1, and the yokes 11a to 23a are provided when the movable body 4 is not magnetically levitated. 11d and the convex magnetic poles 13a to 13d do not collide with each other.

On the other hand, the auxiliary plate 2 is arranged on the outer peripheral surface of the mirror support 8 so as to extend along the axis of the movable body 4.
One end side of 4 is fixed. The lower surface of the auxiliary plate 24 in FIG. 1 is an inclined surface 25 that is inclined with respect to the axis of the movable body 4.
Is formed in. The stationary body 1 is fixed with an axial movement amount detector 26 that detects the axial movement amount of the movable body 4 in a non-contact manner from the distance between the stationary body 1 and the inclined surface 25. The axial movement amount detector 26, the tubular coil 22, the bias coil, the control coil, and the position detector that form the main elements 10a and 10b of the magnetic support device 10 described above are the control device 31 shown in FIG. It is connected to the.

The controller 31 includes a magnetic support controller 32,
It is composed of an axial movement amount control unit 33. It should be noted that FIG. 3 shows a magnetic support control section 32 for urging and controlling the coils 12a to 12d of the main element 10a.
The control unit for controlling the energization of each coil of 0b is omitted.

The magnetic support control section 32 introduces the outputs of the four movement amount detectors 15a to 15d into the processing circuit 35 and converts them into radial displacement amounts. Then, these displacement amounts are introduced into the control circuit 36 to determine operation amounts from the difference from the reference position, these operation amounts are converted into currents by the current amplifier 37, and these currents are supplied to the control coils 18 of the coils 12a to 12d. I am trying to give. The input end of the current amplifier 37 is connected to the power supply 38. On the other hand, an axial movement amount signal output from a processing circuit 39 of an axial position control unit 33, which will be described later, is introduced into the parameter adjuster 42 to balance the force balance condition, the center of gravity of the movable body, and the rotational movement around the center of gravity. The operation amount is determined so as to satisfy the decoupling condition.

That is, referring to FIG. 4, with respect to the movable body 4 supported in an equilibrium state, the axis of the movable body 4 having the center of gravity G of the movable body 4 at the initial position as the origin o coincides with the z-axis. In the coordinate system o-xyz fixed in space as described above, when the center of gravity motion of the movable body 4 and the rotational motions in the xz plane and the yz plane are approximated as the fluctuation from the equilibrium state is Can be described as First of all,

[0023]

[Equation 1]

Here, ∘ represents the differential d / dt with respect to time t, M is the mass of the movable body 4, M ₀ is the component of the electromagnet attraction force of M,

[0025]

[Equation 2]

And F _{1 to} F ₈ are the yokes 11 a to 11
The attraction force of each electromagnet acting on the movable body 4 via d, and g is the gravitational acceleration. The rotational movement is

[0027]

[Equation 3]

[0028] In addition, I is the inertial moment in the radial direction of the movable body 4, L ₁ is the distance from the center of gravity G of the movable body 4 to the action of F _{1 to} F _{4 in} the positive direction of the z axis, and L ₂ is the center of gravity of the movable body 4. The distance from G to the action of F _{5 to} F _{8 in} the negative direction of the z axis is shown.

Here, the parameter adjuster 42 assumes that the characteristics of each electromagnet are all the same, and the following equilibrium condition F ₃ = F ₁ + L ₂ / (L ₁ + L ₂ ) · M ₀ · g ... (5) F ₄ = F ₂ + L ₂ / (L ₁ + L ₂ ) · M ₀ · g (6) F ₇ = F ₅ + L ₁ / (L ₁ + L ₂ ) · M ₀ · g (7) F _{8 = F 6 + L 1 /} (L 1 + L 2) · M 0 · g ... (8), non-interference conditions _{(F 1 -F 3) · L} 1 - (F 5 -F 7) · L 2 = _{0 ... (9) (F 2} -F 4) · L 1 - (F 6 -F 8) · L 2 = 0 ... (10) which adjusts the control parameter to satisfy a. Specifically, the level of the steady excitation current flowing in each bias coil 17 is used as a parameter, and the level of the steady excitation current is determined in correspondence with the movement amount of the movable body 4. And
The output of the parameter adjuster 42 is converted into a current by the current amplifier 44, and this current is given to each bias coil 17 of the coils 12a to 12d.

The axial movement amount control unit 33 introduces the output of the axial movement amount detector 26 and the outputs of the position detectors 15a to 15d into the processing circuit 39, and the processing circuit 39 causes the movable body 4 to move in the radial direction. The true axial movement amount signal is obtained by removing the error appearing in the output of the axial movement amount detector 26 depending on the amount. Then, the deviation between the obtained axial movement amount signal and the target position signal H is obtained by the control circuit 40, this deviation is converted into a current by the current amplifier 41, and this current is converted into the tubular coil 22.
I am trying to flush it. By this control, the movable body 4 is moved to the target position and stopped at this target position.

With such a configuration, the magnetic support device 1
When 0 is operated, each bias coil 17 is energized and each control coil 18 is energized at a level according to the amount of displacement of the movable body 4 in the radial direction and with a current having a polarity according to the displacement direction. .. That is, the magnetic gap length between the magnetic pole surfaces of the yokes 11a to 11d and the magnetic pole surfaces of the convex magnetic poles 13a to 13d is obtained based on the outputs of the position detectors 15a to 15d. Then, for the portion where the magnetic gap length is widened, the control coil 18 is energized so as to increase the magnetic flux passing through the magnetic gap. The control coil 18 is urged to reduce the magnetic flux passing through the magnetic gap in the portion where the magnetic gap length is narrowed. Therefore, the movable body 4 is supported by the magnetic support device 10 in a completely non-contact manner with respect to the stationary body 1.

Further, when the target position signal H is given, the electromagnetic force generating mechanism 20 operates to give a moving force in the axial direction to the movable body 4 in a non-contact manner on the same principle as that of a known voice coil motor. , The movable body 4 is stopped at the target position. In this case, the auxiliary plate 24 is used to detect the axial position required for position control.
The non-contact detection is performed by the axial movement amount detector 26 whose detection target is the inclined surface 25 provided on the. Therefore,
Axial driving and positioning are also performed without contact.

By the way, in this device, the movable member 4
The bias coil 17 is supplied with a steady exciting current satisfying the condition of equilibrium of forces including the force of the magnetic support device 10 and the condition of decoupling the center of gravity motion and the rotary motion of the movable body in accordance with the amount of axial movement of. Therefore, since there is theoretically no influence on the rotational movement due to the disturbance in the direction of the center of gravity from the base 2, when the movable body 4 is precisely positioned in the rotational movement direction, the natural vibration of the rotational movement system is generated. High number,
By reducing the natural frequency of the center-of-gravity motion system, the transmitted vibration can be reduced and the positioning accuracy can be sufficiently ensured. On the other hand, in the case of performing precise positioning of the center-of-gravity movement, it is possible to cope with it by suppressing the resonance of the support system and stopping the vibration quickly.

FIG. 5 shows an example in which the steady currents I _{1 to} I ₈ are applied to the bias coil 17 so as to satisfy the above-described force balance condition and decoupling condition. In this figure, the steady exciting currents I _{5 to} I ₈ become zero at the position of the moving amount L _{G because} the position of the center of gravity G of the movable body 4 is on the arrow A line (FIG. 1,
This is because it coincides with the positions of the yokes 11a to 11b provided in FIG. Therefore, at the position of this movement amount L _G , the rotational movement of the movable body 4 is uncontrolled. For this reason, when importance is attached to the control of the rotational movement, the maximum movement amount may not exceed L _G , or the update of the steady excitation current may be postponed at least at the position of L _G. Although I ₁ and I ₂ are set to constant values in FIG. 5, the present invention is not limited to this.

The present invention is not limited to the above embodiment. That is, in the linear dynamic magnetic support device that satisfies the above-described conditions, the parameter adjuster may be added with a control model of the magnetic support system and a function of updating the compensation parameter. In a system satisfying the force equilibrium condition and the decoupling condition, the control system can be designed independently for the center-of-gravity motion and the rotational motion, so that the parameter adjuster 42 has a control model updating function and a stabilizing support function. By adding a compensation parameter updating function for this, it becomes possible to keep the characteristics of the magnetic support system constant regardless of the amount of movement of the movable body 4.

Here, the general formula of the control model will be described as an example. The equation of motion in the x direction can be described as follows.

[0037]

[Equation 4]

Here, f is an external force, k _D (L ₁ ) is a negative equilibrium rigidity in the moving amount L ₁ , and k _U (L ₁ ) · U _X is a control force for stabilization, which is a function of the moving amount L ₁ . In particular, U _X is a feedback manipulated variable that realizes stabilization of the system based on the observed values such as the displacement x, the velocity of the first derivative of x, and the acceleration of the second derivative.

Each parameter of k _D (L ₁ ) and k _U (L ₁ ) shown in this general formula is updated according to the moving amount of the movable body 4. Also, these k _D (L ₁ ) and k _U (L
_The compensation parameter that determines the feedback manipulated variable U _X is updated from ₁ ) and the desired support characteristic condition. The control constant of the control circuit 36 is adjusted according to this update.

With such a structure, the same magnetic support characteristic can be always obtained with respect to the total amount of movement of the movable body 4 in the axial direction.

Further, although the bias coil is provided in the above embodiment, the control may be performed only by the control coil. Further, in the above-described embodiment, two sets of electromagnet groups necessary for magnetic support are provided in the axial direction, but three or more sets may be provided. Furthermore, although the control parameter is continuously adjusted in the above-mentioned embodiment, it may be adjusted intermittently.

[0042]

As described above in detail, according to the present invention, the control parameter of the magnetic support control system is adjusted in accordance with the amount of movement of the movable body in the axial direction. Support for decoupling with the rotational motion around the center of gravity becomes possible. Further, the control system for the center of gravity motion and the control system for the rotary motion can be designed independently, so that the design can be simplified. Furthermore, it is possible to easily implement measures that can minimize the influence of the disturbance from the base on the accuracy of positioning on the rotational movement due to the disturbance in the direction of the center of gravity and the influence on the center of gravity movement due to the disturbance in the direction of rotation. It can be secured stably.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a linear dynamic magnetic support device according to an embodiment of the present invention, taken along the line SS in FIG. 2 and viewed in the direction of the arrow.

FIG. 2 is a cross-sectional view of the same device taken along line RR in FIG. 1 and viewed in the direction of the arrow.

FIG. 3 is a block configuration diagram of a control device in the device.

FIG. 4 is a view for explaining a force equilibrium condition and a decoupling condition.

FIG. 5 is a diagram showing an example of a relationship between a moving amount of a movable body and a steady excitation current.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Stationary body, 4 ... Movable body, 10 ... Magnetic support device, 11a-11d ... Yoke, 12a
~ 12d ... coil, 13a ~ 13d ... convex magnetic pole,
14a to 14d ... Flat surface, 15a to 15d ... Radial position detector, 17 ... Bias coil, 1
8 ... Control coil, 20 ... Electromagnetic force generation mechanism, 21 ... Permanent magnet, 22 ... Cylindrical coil, 24 ... Auxiliary plate, 2
5 ... Inclined surface, 26 ... Axial movement amount detector, 31 ... Control device, 32 ... Magnetic support control part, 33 ... Axial movement amount control part.

Claims (4)

[Claims] 1. A stationary body, a movable body disposed in the vicinity of the stationary body so as to be movable in the axial direction, a position surrounding the movable body of the stationary body, and at two or more positions in the axial direction. The plurality of electromagnet groups provided, the radial position detecting means for detecting the radial position of the movable body, and the magnetic force of the plurality of electromagnet groups based on the information of the position detecting means to move the movable body. A magnetic support control system for supporting the body in a non-contact manner, an axial movement amount detecting means for detecting an axial movement amount of the movable body, and a driving means for giving an axial moving force to the movable body,
A linear dynamic magnetic field comprising: a control parameter adjusting means for adjusting the control parameter of the magnetic support control system intermittently or continuously according to the information obtained by the axial movement amount detecting means. Support device. 2. The linear dynamic magnetic support apparatus according to claim 1, wherein the control parameter adjusted by the control parameter adjusting means is a level of a steady excitation current flowing through the electromagnet group. 3. The level of the steady-state exciting current adjusted by the control parameter adjusting means is a condition of equilibrium of the force applied by the electromagnet group and the center of gravity movement of the movable body and the rotational movement around the center of gravity. The linear dynamic magnetic support device according to claim 2, wherein the linear dynamic magnetic support device is adjusted so as to satisfy an interference condition. 4. The control parameter adjusting means updates the model of the magnetic support system in accordance with the information obtained by the axial movement amount detecting means, and a magnetic field based on the result of the control model updating means. The linear dynamic magnetic support device according to claim 1 or 3, further comprising a compensation parameter updating means for updating a compensation parameter for stabilizing the support system.