Rotary driving device and control method for the same, and rotary apparatus

Abstract

To provide a rotary driving device that can levitate a rotor while avoiding an increase in size of the entire device.SOLUTION: A rotary driving device has: a rotor that has first magnetic parts and is rotatable in a rotation direction centered on a rotation axis intersecting the direction of gravity; a stator that has second magnetic parts; a support part that supports the rotor located at a first position; and a control unit. The first magnetic parts are arranged circumferentially along the rotation direction on an outer peripheral side face of the rotor. The second magnetic parts are arranged in an arc shape along the rotation direction above the rotor. When the rotor is located at the first position, and a levitation force on the rotor is less than a predetermined value, the control unit rotates the rotor to a second position where the levitation force is equal to or more than the predetermined value and levitates the rotor from the second position.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to a rotary drive device, a control method thereof, and a rotating device. [Background technology]

[0002] A known example of a rotating device that uses magnetic force to rotate a rotor in a non-contact manner is a gantry for computed tomography (CT).Furthermore, such a configuration is known to be applied to a magnetically levitated motor.

[0003] In a typical X-ray CT system, an X-ray tube is attached to the rotor side of a magnetic section that includes a stator and a rotor, and scanning is performed by rotating the rotor. To increase the rotation speed of the rotor, a magnetic levitation motor is used, which uses a magnetic bearing for the rotor's magnetic support, with the aim of eliminating the sliding parts of the motor. If a rotation actuator and a magnetic levitation actuator are separately arranged to rotate the motor and magnetically levitate it, the entire system tends to become larger. To avoid such an increase in system size and achieve a more compact system, a configuration is needed in which the motor rotation and magnetic levitation are controlled by the same actuator.

[0004] One known configuration of a magnetic levitation motor that generates both rotational torque and levitation force using the same actuator is the configuration described in Patent Document 1. The configuration described in Patent Document 1 uses an induction motor, and obtains both rotational torque and levitation force by applying magnetic force from a coil on the stator side to a rotor made of a magnetic material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-184345 Summary of the Invention [Problem to be solved by the invention]

[0006] CT scanners require high positional accuracy when scanning while rotating. For this reason, CT scanners use synchronous motors instead of induction motors. Synchronous motors use permanent magnets in either the stator or rotor. Furthermore, to achieve high torque, the coils in synchronous motors have cores such as iron cores. As a result, there is always an attractive force between the stator and rotor.

[0007] When levitating a rotor from a magnetic bearing, the attractive force generated between the stator and rotor as described above pulls the rotor in a direction different from the direction of gravity, causing the rotor to vibrate. As a result, it is difficult for the rotor to levitate stably when transitioning from a seated state supported by the magnetic bearing to a levitated state. Because CT devices are particularly large, there is a concern that the rotor may come into contact with the magnetic bearing when it vibrates, resulting in wear on the rotor or the magnetic bearing.

[0008] An object of the present invention is to provide a rotary drive device capable of levitating a rotor while avoiding an increase in the size of the entire device, a control method therefor, and a rotating device. [Means for solving the problem]

[0009] According to one aspect of the present invention, there is provided a rotary drive device comprising: a rotor having a first magnetic force portion and rotatable in a rotational direction around a rotation axis that intersects the direction of gravity; a stator having a second magnetic force portion; a support portion that supports the rotor located at a first position; and a control portion, wherein the first magnetic force portion is arranged circumferentially along the rotational direction on the outer peripheral side of the rotor; and the second magnetic force portion is arranged in an arc shape above the rotor that also follows the rotational direction; and when the rotor is located at the first position and the levitation force on the rotor is less than a predetermined value, the control portion rotates the rotor to a second position where the levitation force is equal to or greater than a predetermined value, and levitates the rotor from the second position.

[0010] According to another aspect of the present invention, there is provided a rotary drive device comprising: a rotor having a first magnetic force portion and rotatable in a rotational direction around a rotation axis that intersects with the direction of gravity; a stator having a second magnetic force portion; a support portion that supports the rotor located at a first position; and a control portion, wherein the first magnetic force portion is arranged circumferentially along the rotational direction on the outer peripheral side surface of the rotor; and the second magnetic force portion is arranged in an arc shape that also follows the rotational direction above the rotor; and when the rotor is located at the first position and a cogging torque on the rotor is equal to or greater than a predetermined value, the control portion rotates the rotor to a second position where the cogging torque is less than the predetermined value, and levitates the rotor from the second position. [Effects of the Invention]

[0011] According to the present invention, the rotor can be levitated stably while avoiding an increase in the size of the entire device. [Brief explanation of the drawings]

[0012] [Figure 1A] 1 is a schematic diagram showing a rotation drive device according to a first embodiment of the present invention. [Figure 1B] 1 is a schematic diagram showing a rotation drive device according to a first embodiment of the present invention. [Figure 1C] 1 is a schematic diagram showing a rotation drive device according to a first embodiment of the present invention. [Figure 1D] 1 is a schematic diagram showing a rotation drive device according to a first embodiment of the present invention. [Figure 2A] 1 is a schematic diagram showing the arrangement of permanent magnets in a rotary drive device according to a first embodiment of the present invention. [Figure 2B] 1 is a schematic diagram showing the arrangement of coils in a rotary drive device according to a first embodiment of the present invention. [Figure 2C] 3 is a schematic diagram showing a thrust constant in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 2D] 3 is a schematic diagram showing a thrust constant in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 3A] 1 is a schematic diagram showing an arrangement of sensors in a rotation drive device according to a first embodiment of the present invention. [Figure 3B] 3 is a schematic diagram illustrating a method for calculating the displacement of the rotor from a sensor in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 4] 1 is a schematic diagram showing a current control system in a rotary drive device according to a first embodiment of the present invention. [Figure 5] 1 is a block diagram showing a control loop for calculating the magnitude of torque to be applied to a rotor in a rotary drive device according to a first embodiment of the present invention. FIG. [Figure 6] 3 is a schematic diagram showing torque controlled by a coil in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 7A] 3 is a schematic diagram showing an attractive force acting between a permanent magnet and a core of a coil in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 7B] 3 is a schematic diagram showing an attractive force acting between a permanent magnet and a core of a coil in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 8A] 3 is a schematic diagram showing forces acting according to the position of the rotor in the Y direction in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 8B] 3 is a schematic diagram showing forces acting according to the position of the rotor in the Y direction in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 8C] 3 is a schematic diagram showing forces acting according to the position of the rotor in the Y direction in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 9A] 1 is a schematic view showing a state in which a rotor abuts against a seating bearing in a rotary drive device according to a first embodiment of the present invention. FIG. [Figure 9B] 1 is a schematic view showing a state in which a rotor abuts against a seating bearing in a rotary drive device according to a first embodiment of the present invention. FIG. [Figure 10] 3 is a schematic diagram showing an arrangement of permanent magnets that prioritizes torque in the Y direction in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 11A]3 is a schematic diagram showing a state of the rotor that provides an electrical angle that facilitates stable levitation in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 11B] 3 is a schematic diagram showing a state of the rotor that provides an electrical angle that facilitates stable levitation in the rotary drive device according to the first embodiment of the present invention. FIG. [Figure 12A] 4 is an example of data showing the transition of the position of the rotor in the X direction during stable levitation in the rotary drive device according to the first embodiment of the present invention. [Figure 12B] 4 is an example of data showing the transition of the position of the rotor in the X direction during stable levitation in the rotary drive device according to the first embodiment of the present invention. [Figure 13A] 4 is an example of data showing a transition of a current command value during stable levitation in the rotary drive device according to the first embodiment of the present invention. [Figure 13B] 4 is an example of data showing a transition of a current command value during stable levitation in the rotary drive device according to the first embodiment of the present invention. [Figure 14] 10 is a flowchart showing a procedure for floating a rotor by a floating procedure executing unit in a rotary drive device before the present invention is applied. [Figure 15] 10 is a flowchart showing a procedure for floating the rotor by a floating procedure executing unit when a procedure for rotating the rotor is added before the execution of the floating procedure in the rotary drive device according to the first embodiment of the present invention. [Figure 16A] 10 is a schematic diagram showing a state of the rotor in which the cogging torque becomes a large electrical angle in the rotary drive device according to the second embodiment of the present invention. FIG. [Figure 16B] 10 is a schematic diagram showing a state of the rotor in which the cogging torque becomes a large electrical angle in the rotary drive device according to the second embodiment of the present invention. FIG. [Figure 17] 10 is a flowchart showing a procedure for floating a rotor by a floating procedure executing unit in a rotary drive device according to a second embodiment of the present invention. [Figure 18] FIG. 10 is a schematic view showing a rotating device according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] [First embodiment] A rotary drive device according to a first embodiment of the present invention will be described with reference to Figures 1A to 15. The rotary drive device according to this embodiment has a rotor with a rotation axis that intersects with the direction of gravity, and a stator that is arranged above the rotor in the direction of gravity, and rotates the rotor around its axis in a non-contact manner while magnetically levitating the rotor in the direction of gravity.

[0014] Here, the coordinate axes and directions used in the following description are defined. First, the rotation axis around which the rotor 110 (described later) rotates is defined as the Z axis. An XY plane is defined perpendicular to the Z axis, and two axes perpendicular to each other on the XY plane are defined as the X direction, the Y direction, and the Z direction. The direction along the X axis is defined as the X direction, the Y direction, and the Z direction. The direction of rotation around the X axis is defined as the Wx direction, the Wy direction, and the Wz direction. The origin of the XYZ coordinate system including the X, Y, and Z axes is defined as Os. The origin Os is the position connecting the center lines of the coils arranged on the stator 200 (described later). The positive direction of rotation in the Wx, Wy, and Wz directions is defined as the clockwise direction from the origin Os toward the positive direction of the X, Y, and Z axes. The R axis is defined as the radial direction in which the radius increases on the plane along the XY plane, with the Z axis as the central axis. In the following description, the Z direction is defined as the horizontal direction and the Y direction as the direction of gravity. The X, Y, and Z directions are not necessarily limited to being perpendicular to each other, but can also be defined as directions that intersect with each other. The Z direction does not necessarily have to be horizontal, but may be a direction inclined relative to the horizontal direction. In this case, the X and Z directions can be defined in the same way relative to the Z direction.

[0015] First, the configuration of a rotational drive device according to this embodiment will be described with reference to Figures 1A to 1D. Figure 1A is a perspective view showing a rotational drive device 10 according to this embodiment. Figure 1B is a side view of the rotational drive device 10 according to this embodiment as seen in the Z direction. Figure 1C is a top view of the rotational drive device 10 according to this embodiment as seen in the Y direction. Figure 1D is a cross-sectional view of a cross section taken along line AA' shown in Figure 1B as seen in the X direction.

[0016] 1A to 1C, the rotary drive device 10 according to this embodiment includes a rotor 110 and a stator 200. The rotor 110 includes a plurality of first permanent magnets 101a and a plurality of second permanent magnets 101b as a permanent magnet group. The stator 200 includes a plurality of first coils 201a and a plurality of second coils 201b as a coil group. The rotary drive device 10 also includes a current control system 300 (described below) as a control unit that controls the driving of the rotor 110.

[0017] In the following description, unless otherwise necessary, each permanent magnet in the plurality of first permanent magnets 101a will be simply referred to as the "first permanent magnet 101a," and each permanent magnet in the plurality of second permanent magnets 101b will be simply referred to as the "second permanent magnet 101b." When it is necessary to identify each permanent magnet individually, each permanent magnet will be individually identified by the notation "first permanent magnet 101a-1," "first permanent magnet 101a-2," "second permanent magnet 101b-1," "second permanent magnet 101b-2," etc., with a subnumber following "-." In addition, the "first permanent magnet 101a" and the "second permanent magnet 101b" may be collectively referred to simply as the "permanent magnet 101" without distinction.

[0018] Similarly, unless otherwise necessary, each coil in the plurality of first coils 201a will be simply referred to as the "first coil 201a," and each coil in the plurality of second coils 201b will be simply referred to as the "second coil 201b." When it is necessary to identify each coil individually, each coil will be individually identified by a symbol with a subnumber following a "-," such as "first coil 201a-1," "first coil 201a-2," "second coil 201b-1," or "second coil 201b-2." Coil components are also similarly represented by a symbol with a subnumber, and individually identified as necessary. Furthermore, for a group of the plurality of first coils 201a or the plurality of second coils 201b, the symbol "j" is used as a coil index, as described below. Here, j is a positive integer. Furthermore, the "first coil 201a" and the "second coil 201b" may be collectively referred to simply as the "coil 201" without distinction.

[0019] As shown in FIG. 1A, rotor 110 has a hollow cylindrical shape with the Z axis as its central axis. Rotor 110 is configured to be rotatable in the Wz direction, which is the rotation direction around the Z axis as the rotation axis. The shape of rotor 110 is not limited to a hollow cylindrical shape. The shape of rotor 110 may be any shape that allows rotation around a rotation axis that is aligned in a direction intersecting the direction of gravity, and may be another shape, such as a cylindrical shape, depending on the configuration of the device that utilizes the rotation of rotor 110.

[0020] The plurality of first permanent magnets 101a, which are part of the permanent magnet group, are attached and installed on the outer circumferential side surface of the rotor 110 so as to be evenly aligned in a single row along the Wz direction, which is the direction of rotation. The plurality of second permanent magnets 101b, which are also part of the permanent magnet group, are attached and installed on the outer circumferential side surface of the rotor 110 so as to be evenly aligned in a single row along the Wz direction. For example, the plurality of first permanent magnets 101a are installed on the outer circumferential side surface of one end of the rotor 110 in the Z direction, and the plurality of second permanent magnets 101b are installed on the outer circumferential side surface of the rotor 110 so as to be circumferentially aligned on the outer circumferential side surface of the rotor 110 at the other end in the Z direction. In this manner, the plurality of first permanent magnets 101a and the plurality of second permanent magnets 101b are arranged in the rotor 110. The first permanent magnets 101a and the second permanent magnets 101b function as first magnetic force portions that exert magnetic forces between the first coil 201a and the second coil 201b of the stator 200, respectively.

[0021] The stator 200 is provided with a plurality of first coils 201a and a plurality of second coils 201b located above the rotor 110 in the Y direction on the outside of the rotor 110 so as to face the first permanent magnets 101a and the second permanent magnets 101b. The first coils 201a are attached to positions that allow them to face the first permanent magnets 101a of the rotor 110 so as to be evenly aligned in a row in an arc along the Wz direction. The second coils 201b are attached to positions that allow them to face the second permanent magnets 101b of the rotor 110 so as to be evenly aligned in a row in an arc along the Wz direction. In this manner, the first coils 201a and the second coils 201b are arranged in the stator 200. The first coil 201a and the second coil 201b function as a second magnetic force portion in which a magnetic force acts between the first permanent magnet 101a and the second permanent magnet 101b of the rotor 110, respectively.

[0022] The set of the first coil 201a and the first permanent magnet 101a and the set of the second coil 201b and the second permanent magnet 101b are arranged symmetrically on the stator 200 and the rotor 110 with the XY plane as the plane of symmetry. In this way, the rotor 110 is arranged below the plurality of first coils 201a and the plurality of second coils 201b in the direction of gravity, and is levitated in the Y direction by levitation control while rotating around the Z axis by rotation control.

[0023] In this embodiment, the stator 200 is referenced to a reference Oc, which is a straight line extending diagonally upward from the origin Os along the XY plane, and the first coils 201a-1 to 201a-12 are arranged in order in the Θ direction, which is the circumferential direction along the Wz direction. Similarly, the stator 200 is referenced to a reference Oc, and the second coils 201b-1 to 201b-12 are arranged in order in the Θ direction. Furthermore, the rotor 110 is referenced to a reference Or, which is a straight line extending from the origin Os toward a predetermined position on the outer circumferential side surface of the rotor 110, and the rotor 110 is referenced to a reference Or, and the rotor 110 is referenced to a reference Or, and the rotor 110 is referenced to a reference Or, and the rotor 110 is referenced to a reference Or. Similarly, the rotor 110 is referenced to a reference Or, and the rotor 110 is referenced to a reference Or.

[0024] The numbers of the first coils 201a, the second coils 201b, the first permanent magnets 101a, and the second permanent magnets 101b are not limited to those shown in this embodiment. The numbers of the first coils 201a, the second coils 201b, the first permanent magnets 101a, and the second permanent magnets 101b can be changed as appropriate depending on the thrust required in the q-axis direction, the d-axis direction, and the Z-axis direction, which will be described later. Although the number of the first coils 201a and the number of the second coils 201b are the same, this does not necessarily have to be the case. Although the number of the first permanent magnets 101a and the number of the second permanent magnets 101b are the same, this does not necessarily have to be the case.

[0025] In addition, in this embodiment, a case will be described in which there are two rows of pairs of mutually opposing permanent magnets and coils: a row of pairs of the first permanent magnet 101a and the first coil 201a, and a row of pairs of the second permanent magnet 101b and the second coil 201b. However, the rows of pairs of permanent magnets and coils are not limited to this case. The rows of pairs of permanent magnets and coils may be one row, two rows, or even three or more rows in which a row of pairs similar to the first permanent magnet 101a and the first coil 201a is further installed. Note that when there is one row of pairs of permanent magnets and coils, it is desirable to arrange the coils symmetrically with respect to the YZ plane from the viewpoint of stable control of the rotor 110.

[0026] Fig. 1B is a side view of Fig. 1A seen from the Z direction. The first coil 201a and the first permanent magnet 101a will be described below with reference to Fig. 1B. Note that the second coil 201b has the same configuration as the first coil 201a, and the second permanent magnet 101b has the same configuration as the first permanent magnet 101a.

[0027] As shown in FIG. 1B , multiple first permanent magnets 101a are attached to the outer peripheral side surface of the rotor 110 in a line along the circumferential direction of the rotor 110. The rotor 110 has a yoke 102 attached to its outer peripheral side surface. The multiple first permanent magnets 101a are attached to the outer peripheral side surface of the rotor 110 via the yoke 102. As a result, the yoke 102 is disposed behind the first permanent magnets 101a. The yoke 102 is made of a magnetic metal such as iron or SUS400 stainless steel to increase the magnetic force of the first permanent magnets 101a. The yoke 102 itself has sufficient strength and may also serve as a base member for the rotor 110. The yoke 102 may be installed separately from the base member for the rotor 110 or may be integrated with the base member. Note that the yoke 102 does not necessarily have to be installed on the rotor 110, and may not be installed at all. Even in this case, it is possible to control the levitation and rotation of the rotor 110.

[0028] Here, the rotation angle, which is the angle of the rotor 110 in the Wz direction, is defined as θ. The rotation angle θ is the angle from the reference Oc in the Wz direction on the stator 200 side to the reference Or in the Wz direction on the rotor 110 side. The reference Oc in the Wz direction on the stator 200 side is defined as a straight line connecting the first coil 201a-1 arranged in an arc shape and the origin Os. The reference Or in the Wz direction on the rotor 110 side is defined as a straight line connecting the origin Os and the midpoint between the first permanent magnet 101a-1 and the first permanent magnet 101a-24.

[0029] 1C is a top view of FIG. 1A as viewed from the Y direction. Note that, for ease of explanation, FIG. 1C shows the arrangement of first coil 201a and second coil 201b, omitting side yokes 204a and 204b, which will be described later. As shown in FIG. 1C, the plurality of first coils 201a and the plurality of second coils 201b are attached and arranged in plane symmetry with the YZ plane as the plane of symmetry on stator 200. Furthermore, the plurality of first coils 201a and the plurality of second coils 201b are attached and arranged in plane symmetry with the XY plane as the plane of symmetry on stator 200.

[0030] Stator 200 also has X sensor 213, Y sensor 214, Z sensors 210a, 210b, 210c, and Wz sensor 211 as sensors for detecting the displacement or attitude of rotor 110. The displacement of rotor 110 in the X direction can be detected based on the detection value of X sensor 213. The displacement of rotor 110 in the Y direction can be detected based on the detection value of Y sensor 214. The displacement of rotor 110 in the Z direction, Wx direction, and Wy direction can be detected based on the detection values ​​of Z sensors 210a, 210b, 210c. The displacement of rotor 110 in the Wz direction can be detected based on the detection value of Wz sensor 211. Detection of angular displacement is performed by position controller 301, which will be described later.

[0031] X sensor 213 detects the distance in the X direction between rotor 110 and X sensor 213. Y sensor 214 detects the distance in the Y direction between rotor 110 and Y sensor 214. Z sensor 210a detects the distance in the Z direction between rotor 110 and Z sensor 210a. Z sensor 210b detects the distance in the Z direction between rotor 110 and Z sensor 210b. Z sensor 210c detects the distance in the Z direction between rotor 110 and Z sensor 210c. X sensor 213, Y sensor 214, and Z sensors 210a, 210b, and 210c are not particularly limited, and may be sensors that can detect distance, such as eddy current sensors or displacement sensors. Furthermore, these sensors may be optical sensors, magnetic sensors, or the like, with a separate detection scale.

[0032] X sensor 213 is installed to the side of rotor 110 in the X direction and faces the outer circumferential side surface of rotor 110. Y sensor 214 is installed to be above rotor 110 in the Y direction and faces the outer circumferential side surface of rotor 110. Z sensors 210a, 210b, and 210c are installed to be laterally of rotor 110 in the Z direction and face the circumferential end surface of rotor 110 in the Z direction.

[0033] X sensor 213 and Y sensor 214 are installed to detect the outer circumferential side surface, which is the curved surface of rotor 110, and therefore perform detection at positions shifted in the X or Y direction from the apex of the outer circumferential side surface of rotor 110. This is due to the following reasons for X sensor 213 and Y sensor 214.

[0034] The X sensor 213 is as follows. When controlling the levitation of rotor 110, if X sensor 213 is installed to detect the apex of the outer peripheral side surface in the X direction, there will be positions where X sensor 213 indicates the same detection value on the positive and negative sides of the Y direction when movement control of rotor 110 is performed in the Y direction. To avoid such identical detection values, X sensor 213 is installed at a position offset by an offset amount p1 on the negative Y side from the position facing the apex of the X direction of the outer peripheral side surface of rotor 110, as shown in FIG. 1B.

[0035] Furthermore, X sensor 213 is arranged so that the range of levitation control in the Y direction of rotor 110 is equal to or less than offset amount p1. By arranging X sensor 213 in this way, X sensor 213 does not exceed the X-direction apex of the outer peripheral side surface of rotor 110 in the Y direction in terms of configuration or control, and therefore X sensor 213 does not indicate the same detection value on the positive side and negative side in the Y direction.

[0036] In this way, the position of X sensor 213 is offset in the Y direction from the position facing the vertex in the X direction of the outer circumferential side surface of rotor 110, so that X sensor 213 can accurately detect the position of rotor 110. Note that although X sensor 213 is arranged offset on the negative side of the Y direction in FIG. 1B, X sensor 213 may also be arranged offset on the positive side of the Y direction.

[0037] Furthermore, Y sensor 214 is as follows. Similarly, when controlling rotor 110 by levitating it, if Y sensor 214 is installed so as to detect the Y-direction apex of the outer peripheral side surface, there will be positions where Y sensor 214 indicates the same detection value on the positive and negative sides of the X direction when movement control of rotor 110 is performed in the X direction. To avoid such identical detection values, Y sensor 214 is installed at a position that is offset by offset amount p2 on the positive side of the X direction from the position facing the Y-direction apex of the outer peripheral side surface of rotor 110, as shown in FIG. 1B .

[0038] Furthermore, Y sensor 214 is arranged so that the range of movement control in the X direction of rotor 110 is equal to or less than offset amount p2. By arranging Y sensor 214 in this way, in terms of configuration or control, Y sensor 214 does not exceed the Y-direction apex of the outer peripheral side surface of rotor 110 in the X direction, and therefore Y sensor 214 does not indicate the same detection value on the positive side and negative side in the X direction.

[0039] In this way, the position of Y sensor 214 is offset in the X direction from the position facing the vertex in the Y direction of the outer circumferential side surface of rotor 110, so that Y sensor 214 can accurately detect the position of rotor 110. Note that although Y sensor 214 is arranged offset on the positive side of the X direction in FIG. 1B, Y sensor 214 may also be arranged offset on the negative side of the X direction.

[0040] However, if the position of rotor 110 is measured simultaneously by X sensor 213 and Y sensor 214, it is possible to detect deviation of rotor 110. Therefore, X sensor 213 and Y sensor 214 do not necessarily need to be arranged offset as described above.

[0041] Wz sensor 211 is located on the opposite side of rotor 110 in the Z direction from Z sensors 210a, 210b, and 210c, and is installed so as to face the circumferential end surface of rotor 110 in the Z direction. Scale 212 is attached to the circumferential end surface of rotor 110 that Wz sensor 211 faces. Wz sensor 211 detects the rotation angle of rotor 110 in the Wz direction by reading a pattern on scale 212. Wz sensor 211 may be any sensor that can detect angles, such as an optical or magnetic type, and may be an absolute type or an incremental type used together with origin detection means.

[0042] Fig. 1D is a cross-sectional view taken along line AA' in Fig. 1B. The structure and mounting positions of first coil 201a and second coil 201b will now be described with reference to Fig. 1D. First coil 201a and second coil 201b are each formed by winding a conducting wire around a magnetic material such as a silicon steel plate used in general motors.

[0043] Specifically, as shown in FIG. 1D , the first coil 201a-5 is configured by winding a winding 203a-5 around a core 202a-5 made of a magnetic material such as a silicon steel plate, and attaching a U-shaped side yoke 204a-5 to the core 202a-5. The side yoke 204a-5, like the core 202a-5, is also made of a magnetic material such as a silicon steel plate. The core 202a-5 is disposed so that its central axis faces the Z axis along the XY plane. The winding 203a-5 is wound around the core 202a-5 around its central axis. The side yoke 204-5 is configured with three plate-shaped portions that cover the outer side of the core 202a-5 in the R axis direction and both sides in the Z direction. All of the other first coils 201a have the same configuration as the first coil 201a-5.

[0044] In this embodiment, the configuration in which the side yoke 204a is attached is described as an example, but the present invention is not limited to this. The side yoke 204a only needs to be attached when torque in the Z direction is required, and even if the side yoke 204a is not attached, the levitation control and rotation control of the rotor 110 are possible.

[0045] As described above, the first coil 201a is configured to include the core 202a and the side yoke 204a, thereby reducing the magnetic resistance and increasing the magnetic flux density generated by the first permanent magnet 101a and the magnetic flux density generated by passing a current through the winding 203a. Since each magnetic flux density can be increased, the torque generated in each direction can also be increased.

[0046] The second coil 201b has the same configuration as the first coil 201a. The components of the second coil 201b, that is, the core 202b, the winding 203b, and the side yoke 204b, correspond to the components of the first coil 201a, that is, the core 202a, the winding 203a, and the side yoke 204a, respectively.

[0047] The plurality of first permanent magnets 101a and the plurality of second permanent magnets 101b are preferably arranged in plane symmetry with respect to the XY plane in the rotor 110, i.e., with respect to a plane perpendicular to the Z axis, which is the axis of rotation. Furthermore, it is preferable that the weight of the rotor 110 is uniform in the Z direction. By uniformly arranging the weight of the rotor 110, tilt and eccentricity of the rotor 110 caused by weight variations can be reduced, and as a result, control of the rotor 110 can be easily performed. Furthermore, it is preferable that the plurality of first coils 201a and the plurality of second coils 201b are arranged in plane symmetry with respect to the XY plane in the stator 200, i.e., with respect to a plane perpendicular to the Z axis, which is the axis of rotation. By symmetrically arranging the set of the first permanent magnet 101a and the first coil 201a and the set of the second permanent magnet 101b and the second coil 201b in this way, the positions where attractive forces are generated in each set are plane symmetric with respect to the XY plane. By making the positions where the attractive force is generated symmetrical in this way, tilting and eccentricity of rotor 110 caused by variations in position can be reduced, and rotor 110 can be easily controlled.

[0048] Furthermore, it is desirable that the plurality of first coils 201a and the plurality of second coils 201b are arranged in plane symmetry with respect to the YZ plane, that is, with respect to a plane that includes the Z axis, which is the rotation axis, and is along the Y direction, which is the direction of gravity, in stator 200. Due to the symmetry of such an arrangement, the positions where attractive forces are generated are plane symmetric with respect to the YZ plane, which makes it even easier to control rotor 110.

[0049] Although the above description has been given of the case where the first permanent magnet 101a and the second permanent magnet 101b, and the first coil 201a and the second coil 201b are symmetrically arranged, they do not necessarily have to be arranged symmetrically. The tilt and eccentricity of the rotor 110 can be corrected by adjusting the gap between the coil and the permanent magnet or the amount of current flowing through the coil.

[0050] Here, the arrangement and thrust of the first permanent magnet 101a and the first coil 201a will be described using Figures 2A to 2D. The arrangement and thrust of the second permanent magnet 101b and the second coil 201b are similar to those of the first permanent magnet 101a and the first coil 201a.

[0051] 2A is a perspective view of the arrangement of the multiple first permanent magnets 101a as viewed from the Y direction. In this embodiment, 24 first permanent magnets 101a are arranged as shown in FIG. 1B. As shown in FIG. 2A, the 24 first permanent magnets 101a are arranged in order from the reference Or in the Wz direction, with the first permanent magnets 101a-1 to 101a-24 lined up at equal intervals around the outer circumferential side surface of the rotor 110.

[0052] The first permanent magnet 101a is magnetized in the direction of its surface facing the first coil 201a. For example, the surfaces of the first permanent magnets 101a-1, 101a-3, 101a-19, and 101a-21 facing the first coil 201a are magnetized to the north pole, and the surfaces of the first permanent magnets 101a-18, 101a-22, and 101a-24 are magnetized to the south pole. Furthermore, for example, the first permanent magnets 101a-2, 101a-17, 101a-20, and 101-23 are divided into two in the Z direction, and each is magnetized to the north pole and the south pole.

[0053] In this way, the multiple first permanent magnets 101a are arranged on the side facing the first coil 201a so that magnetization units, each consisting of an N pole, a two-part magnetization, an N pole, an S pole, a two-part magnetization, and an S pole arranged in that order in the Wz direction, are periodically arranged in the Wz direction.

[0054] The multiple first permanent magnets 101a may include a first permanent magnet row in which different magnetic poles are alternately arranged in the Wz direction, which is the rotation direction, and a second permanent magnet row in which different magnetic poles are alternately arranged in the Z direction, which intersects with the Wz direction. The Z direction is along the Z axis, which is the rotation axis. In the example shown in FIG. 2A, the first permanent magnets 101a-1, 101a-3, 101a-18, 101a-19, 101a-21, 101a-22, and 101a-24 constitute the first permanent magnet row. In the example shown in FIG. 2A, the first permanent magnets 101a-2, 101a-17, 101a-20, and 101a-23 constitute the second permanent magnet row. The second permanent magnet row is not limited to the two-divided permanent magnet shown in FIG. 2A, but may be composed of multiple permanent magnets. In this case, the multiple permanent magnets constituting the second permanent magnet are arranged so that different magnetic poles are alternately arranged in the Z direction, which is the direction intersecting with Wz. In addition, in the second permanent magnet row, different magnetic poles may be alternately arranged not only in the Z direction but also in the direction intersecting with Wz.

[0055] 2B is a perspective view of the arrangement of the first coils 201a as seen from the Y direction. In this embodiment, 12 first coils 201a are arranged as shown in FIG. 1B. As shown in FIG. 2B, the 12 first coils 201a are arranged in an arc shape, with first coils 201a-1 to 201a-12 arranged in order at equal intervals in the Wz direction from the reference Oc.

[0056] 2C and 2D are schematic diagrams showing the magnitudes of torque in the q-axis direction, d-axis direction, and Z-axis direction generated per unit current in the first coil 201a when the rotation angle θ of the rotor 110 is θ1, i.e., the thrust constants Eq, Ed, and Ez. The q-axis and d-axis shown here correspond to the q-axis and d-axis in motor control theory, respectively. FIG. 1B shows the directions of the q-axis and d-axis for the first coil 201a-10 as a representative example. The q-axis direction corresponds to the circumferential direction, Wz, and the d-axis direction corresponds to the radial direction centered on the Z-axis. FIG. 2C shows the thrust constant Eq in the q-axis direction and the thrust constant Ed in the d-axis direction. FIG. 2D shows the thrust constant Ez in the Z-axis direction.

[0057] As shown in FIGS. 2C and 2D, the magnitudes of the thrust constants Eq, Ed, and Ez vary depending on the rotation angle θ1 of the rotor 110 and the index j of the first coil 201a. Here, the index j is a positive integer, e.g., an integer satisfying 1≦j≦12. The first coil 201a can be identified by using the index j to write "first coil 201a-j." The thrust constants Eq, Ed, and Ez can be expressed as Eq(j, θ), Ed(j, θ), and Ez(j, θ), respectively, with two arguments in parentheses: the index j of the first coil 201a as the first argument and the rotation angle θ of the rotor 110 as the second argument. FIGS. 2C and 2D show the thrust constants when θ=θ1.

[0058] 2A and 2B where θ=θ1, the first coil 201a-10 is positioned approximately midway between the first permanent magnet 101a-24, whose opposing surface has an S pole, and the first permanent magnet 101a-1, whose opposing surface has an N pole. In this case, for example, a unit current is applied to the first coil 201a-10 so that the N pole appears on the side facing the first permanent magnet 101a-24 and the first permanent magnet 101a-1. Note that the application of current to the first coil 201a is performed by a current control system 300, which will be described later. When the unit current is applied to the first coil 201a-10 in this manner, an attractive force acts between the first coil 201a-10 and the first permanent magnet 101a-24, and a repulsive force acts between the first coil 201a-10 and the first permanent magnet 101a-1. That is, a thrust force Eq(10, θ1) is applied to the first coil 201a-10 in the q-axis direction. On the other hand, a thrust force Ed(10, θ1) is applied to the first coil 201a-10 in the d-axis direction, and is relatively small.

[0059] 2A and 2B, the first coil 201a-9 faces the first permanent magnet 101a-24, whose opposing surface has an S pole. In this case, for example, a unit current is applied to the first coil 201a-9 so that the S pole appears on the side facing the first permanent magnet 101a-24. When a unit current is applied to the first coil 201a-9 in this manner, a repulsive force acts between the first coil 201a-9 and the first permanent magnet 101a-24. That is, a thrust force Ed(9, θ1) is applied to the first coil 201a-9 in the d-axis direction. On the other hand, a thrust force Eq(9, θ1) applied to the first coil 201a-9 in the q-axis direction is relatively small.

[0060] 2A and 2B, a unit current is applied to the first coil 201a-3 so that an N pole appears on the side facing the first permanent magnet 101a-20. Then, because the first permanent magnet 101a-20 facing the first coil 201a-3 is divided and magnetized into an N pole and an S pole in the Z direction, a thrust Ez(3, θ1) acts on the first coil 201a-3 in the Z direction.

[0061] The force acting on the first coil 201a can be treated as equivalent to a reaction force acting on the rotor 110. Therefore, for example, when a thrust force is generated in the first coil 201a in the positive direction of the q axis, a thrust force is generated in the rotor 110 in the negative direction of the q axis. In this way, the force acting on the rotor 110 can be controlled by the first coil 201a and the first permanent magnet 101a. Furthermore, by individually controlling the currents applied to the coils using the respective thrust constants for the control directions according to the rotation angle θ1, the forces in the q axis direction, d axis direction, and Z direction can each be controlled.

[0062] 1A from the opposite side in the Z direction to that of FIG. 1B. As shown in FIG. 3A, Z sensors 210a, 210b, and 210c are positioned laterally in the Z direction with respect to rotor 110 and are installed so as to face the circumferential end face of rotor 110 in the Z direction. Z sensors 210a, 210b, and 210c are arranged, for example, at equal angular intervals in the Wz direction. Z sensors 210a, 210b, and 210c are each arranged so as to detect the distance to rotor 110 in the Z direction.

[0063] 3B is a diagram illustrating a method for calculating the displacement of rotor 110 in the Z, Wx, and Wy directions from the detection values ​​of Z sensors 210a, 210b, and 210c. When calculating each displacement, a plane ABC including points A, B, and C is created based on the detection values ​​of Z sensors 210a, 210b, and 210c. The X and Y coordinates of point A are the X and Y coordinates of Z sensor 210a, respectively, and the Z coordinate of point A is a coordinate based on the detection value of Z sensor 210a. The X and Y coordinates of point B are the X and Y coordinates of Z sensor 210b, respectively, and the Z coordinate of point B is a coordinate based on the detection value of Z sensor 210b. The X and Y coordinates of point C are the X and Y coordinates of Z sensor 210c, respectively, and the Z coordinate of point C is a coordinate based on the detection value of Z sensor 210c. The Z-direction displacement, Wx-direction displacement, and Wy-direction displacement of plane ABC can be calculated from the gradient of the normal vector of plane ABC and the distance from origin Os to plane ABC. The Z-direction displacement, Wx-direction displacement, and Wy-direction displacement of plane ABC can be treated as the Z-direction displacement, Wx-direction displacement, and Wy-direction displacement of rotor 110, respectively, i.e., the Z-direction position, Wx-direction rotation angle, and Wy-direction rotation angle of rotor 110. In this way, the displacement of rotor 110 can be calculated using plane ABC. Note that the calculation of each displacement is performed by position controller 301, which will be described below.

[0064] 4 is a connection diagram that schematically shows a current control system 300 that controls the current applied to the first coil 201a and the second coil 201b. The current control system 300 will be described with reference to FIG. 4. The current control system 300 is a control unit that controls the drive of the rotor 110 by controlling the current applied to the plurality of first coils 201a and the plurality of second coils 201b. Note that the configuration of the current control system 300 regarding the first coil 201a will be described as an example, but the configuration regarding the second coil 201b is similar.

[0065] As shown in FIG. 4, the current control system 300 includes a floating procedure execution unit 302, a position controller 301, a plurality of current sensors 312a, and a plurality of current controllers 313a.

[0066] Each of the current controllers 313a is individually connected to a first coil 201a. Each of the current controllers 313a is individually connected to a current sensor 312a. The current controllers 313a can detect the current value of the first coil 201a using the current sensor 312a. Each of the current controllers 313a is connected to the position controller 301. The levitation procedure executer 302 generates and transmits a target position according to a levitation procedure to the position controller 301. The levitation procedure will be described later.

[0067] Furthermore, Z sensors 210a, 210b, and 210c, Wz sensor 211, X sensor 213, and Y sensor 214 are connected to position controller 301. Position controller 301 can detect displacements X, Y, Z, Wx, Wy, and Wz of rotor 110 based on the detection values ​​output by Z sensors 210a, 210b, and 210c, Wz sensor 211, X sensor 213, and Y sensor 214. Displacement X is the displacement in the X direction, displacement Y is the displacement in the Y direction, displacement Z is the displacement in the Z direction, displacement Wx is the displacement in the Wx direction, displacement Wy is the displacement in the Wy direction, and displacement Wz is the displacement in the Wz direction. Position controller 301 detects displacement X based on the detection value of X sensor 213, displacement Y based on the detection value of Y sensor 214, and displacement Wz based on the detection value of Wz sensor 211. Furthermore, position controller 301 detects displacements Z, Wx, and Wy as described above based on the detection values ​​of Z sensors 210a, 210b, and 210c.

[0068] Position controller 301 has a control program, a clock, etc. built in, and calculates the current value to be applied to each first coil 201a in accordance with each displacement of rotor 110. Position controller 301 transmits the calculated current command value that commands the current value to be applied to each first coil 201a to each current controller 313a.

[0069] The current controller 313a applies a predetermined current to the corresponding first coil 201a individually in accordance with the current command value from the position controller 301 while detecting the current amount with the current sensor 312a.

[0070] FIG. 5 is a diagram schematically showing a control loop for calculating the magnitude of the torque to be applied to the rotor 110. A method of controlling the attitude of the rotor 110 by the position controller 301 will be described with reference to FIG. 5. In FIG. 5, ref is the target value of the displacement of the rotor 110, and Trqref is the target value of the torque to be applied to the rotor 110. Also, pos is the displacement (X, Y, Z, Wx, Wy, Wz) of the rotor 110 acquired from the detection values ​​of the sensor group (Z sensors 210a, 210b, 210c, Wz sensor 211, X sensor 213, Y sensor 214). The position controller 301 includes an attitude controller 501, a current calculator 502, and a torque controller 605.

[0071] The torque controller 605 calculates the manipulated variable d for moving the rotor 110 toward the target value from the difference between the torque Tq applied to the rotor 110 and the target value Trqref of the torque applied to the rotor 110. If each component in the Y direction, Wx direction, and Wz direction of the target value Trqref for Z, Wz, and Wy is 0 [N], the torque controller 605 functions as so-called zero power control. The torque controller 605 executes so-called zero power control, and can set the position and attitude at which the gravity and attractive force acting on the rotor 110 are balanced as the target value.

[0072] The attitude controller 501 calculates the torque Tq to be applied to the rotor 110 from the difference err between the target value ref and the manipulated variable d and the displacement pos. The attitude controller 501 may be, for example, a controller using PID control, or a controller using an appropriate filter depending on the characteristics of the rotor 110. Such a controller can stabilize the attitude of the rotor 110.

[0073] The current calculator 502 determines the current I to be applied to the first coil 201a and the second coil 201b from the torque Tq and the displacement pos. The current controllers 313a and 313b apply the determined current I to the first coil 201a and the second coil 201b, respectively.

[0074] When current I is applied to first coil 201a and second coil 201b, electromagnetic force F is generated between first coil 201a and second coil 201b and rotor 110, and acts on rotor 110. This causes levitation control and rotation control of rotor 110 to be performed. Posture controller 501 again detects displacement pos from the detection values ​​of Z sensors 210a, 210b, 210c, Wz sensor 211, X sensor 213, and Y sensor 214, and repeats the above process. In this way, levitation control and rotation control of rotor 110 are performed, and drive of rotor 110 is controlled.

[0075] Torque vector Tq, which indicates the torque applied to rotor 110 as described above, is expressed by the following equation (1). Tx, Ty, and Tz are the magnitudes of torque in the X direction, Y direction, and Z direction, respectively. Furthermore, Twx, Twy, and Twz are the magnitudes of force moments around the X axis, Y axis, and Z axis, respectively. Torque here includes force and force moment, and torque in a direction along an axis such as the X direction, Y direction, or Z direction refers to force. Tq=(Tx,Ty,Tz,Twx,Twy,Twz)...Formula (1)

[0076] The rotary drive device 10 according to this embodiment controls the currents flowing through the first coil 201a and the second coil 201b using the current control system 300 to control the components Tx, Ty, Tz, Twx, Twy, and Twz of the torque vector Tq. This allows the rotary drive device 10 to rotate the rotor 110 in the Wz direction while controlling the attitude (X, Y, Z, Wx, Wy) of the rotor 110. In the attitude of the rotor 110, X, Y, and Z represent positions in the X, Y, and Z directions, respectively, and Wx and Wy represent angles of rotation around the X-axis and Y-axis, respectively.

[0077] 6 is a diagram illustrating torque generated in each of the q-axis direction, d-axis direction, and Z-axis direction at an arbitrary position of the rotor 110. Here, it will be explained with reference to FIG. 6 that torque vector Tq can be applied to the rotor 110 at an arbitrary rotation angle in the Wz direction of the rotor 110 by moving the magnetic fields generated in the first coil 201a and the second coil 201b in accordance with the rotation of the rotor 110.

[0078] In this embodiment, the first coil 201a and the second coil 201b are arranged on the stator 200, so that torque can be generated in each of the q-axis direction, the d-axis direction, and the Z-axis direction. As shown in FIG. 2A , the multiple first permanent magnets 101a and the multiple second permanent magnets 101b each constitute a permanent magnet array including permanent magnets divided in the Z-axis direction and permanent magnets not divided in the Z-axis direction. In the permanent magnet array, the permanent magnets not divided in the Z-axis direction mainly contribute to torque in the q-axis direction and the d-axis direction, and the permanent magnets divided in the Z-axis direction mainly contribute to torque in the Z-axis direction.

[0079] Here, the symbols used in the explanation will be organized, and are shown appropriately in Figure 6. j: an index for distinguishing the first coil 201a or the second coil 201b (j = 1 to 12) Ij: current value applied to the j-th first coil 201a-j or the j-th second coil 201b-j Φj: angle of the jth first coil 201a-j or the jth second coil 201b-j in the Wz direction r: radius to the first permanent magnet 101a or the second permanent magnet 101b *: Multiplication sign Σ: Sum when index j is changed from 1 to 12

[0080] The symbols relating to the forces acting on the first coil 201a are as follows: Eqj, Edj, and Ezj shown in FIG. 6 correspond to Eqa(j, θ), Eda(j, θ), and Eza(j, θ) shown below, respectively. Eqa(j, θ): Force per unit current in the q-axis direction acting between the j-th first coil 201a-j and the rotor 110 at a rotation angle θ Eda(j, θ): Force per unit current in the d-axis direction acting between the j-th first coil 201a-j and the rotor 110 at a rotation angle θ Eza(j, θ): Force per unit current in the Z direction acting between the j-th first coil 201a-j and the rotor 110 at a rotation angle θ

[0081] The symbols relating to the forces acting on the second coil 201b are as follows: Eqj, Edj, and Ezj shown in FIG. 6 correspond to Eqb(j, θ), Edb(j, θ), and Ezb(j, θ) shown below, respectively. Eqb(j, θ): Force per unit current in the q-axis direction acting between the j-th second coil 201b-j and the rotor 110 at a rotation angle θ Edb(j, θ): Force per unit current in the d-axis direction acting between the j-th second coil 201b-j and the rotor 110 at a rotation angle θ Ezb(j, θ): Force per unit current in the Z-axis direction acting between the j-th second coil 201b-j and the rotor 110 at a rotation angle θ

[0082] The torque vector Tq generated in the rotor 110 is expressed by the above formula (1). Furthermore, the components of the torque vector generated in the first coil 201a are represented by Txa, Tya, Tza, and Twza, and the components of the torque vector generated in the second coil 201b are represented by Txb, Tyb, Tzb, and Twzb. These components are in the following directions: Txa: X-direction component of the torque vector generated in the first coil 201a Tya: Y-direction component of the torque vector generated in the first coil 201a Tza: Z-direction component of the torque vector generated in the first coil 201a Twza: Wz-direction component of the torque vector generated in the first coil 201a Txb: X-direction component of the torque vector generated in the second coil 201b Tyb: Y-direction component of the torque vector generated in the second coil 201b Tzb: Z-direction component of the torque vector generated in the second coil 201b Twzb: Wz-direction component of the torque vector generated in the second coil 201b

[0083] The components Txa, Tya, Tza, and Twza are respectively represented by the following formulas (2-1) to (2-4). Txa=Σ{(-Eqa(j,θ)*sinΦj+Eda(j,θ)*cosΦj)*Ij} …Equation (2-1) Tya=Σ{(Eqa(j,θ)*cosΦj+Eda(j,θ)*sinΦj)*Ij} …Equation (2-2) Tza=Σ{Eza(j,θ)*Ij} …Equation (2-3) Twza=Σ{Eqa(j,θ)*r*Ij} …Equation (2-4)

[0084] The components Txb, Tyb, Tzb, and Twzb are respectively represented by the following formulas (2-5) to (2-8). Txb=Σ{(-Eqb(j,θ)*sinΦj+Edb(j,θ)*cosΦj)*Ij} …Equation (2-5) Tyb=Σ{(Eqb(j,θ)*cosΦj+Edb(j,θ)*sinΦj)*Ij} …Equation (2-6) Tzb=Σ{Ezb(j,θ)*Ij} …Equation (2-7) Twzb=Σ{Eqb(j,θ)*r*Ij} …Equation (2-8)

[0085] 1C, the first coil 201a and the second coil 201b are arranged symmetrically with respect to the XY plane, with each coil spaced a distance t from the XY plane in the Z direction. Then, the components Tx, Ty, Tz, Twx, Twy, and Twz of the torque vector Tq are expressed by the following equations (3-1) to (3-6), respectively. Tx = Txa + Txb ... Equation (3-1) Ty = Tya + Tyb ... Equation (3-2) Tz = Tza + Tzb ...Equation (3-3) Twx = (Tya - Tyb) * t ... Equation (3-4) Twy = (Txa - Txb) * t ... Equation (3-5) Twz=Twza+Twzb ...Equation (3-6)

[0086] To apply a desired torque vector Tq, a current Ij that satisfies the above formulas (2-1) to (2-8) and formulas (3-1) to (3-6) may be applied to each of the first coil 201a and the second coil 201b. The current control system 300 can control the application of the current Ij. Note that each coil generates a small amount of torque in the d-axis direction. The torque in the d-axis direction generated in each coil can be canceled out by arranging the first coil 201a and the second coil 201b symmetrically with respect to the XY plane and the YZ plane, since the directions of the torques are opposite to each other.

[0087] In addition to the above control, by controlling the current applied to the coils more precisely using the current control system 300, it is possible to further apply a force Twy to the rotor 110. Specifically, the multiple first coils 201a are arranged on the upstream and downstream sides with respect to the YZ plane, and the current of the first coils 201a facing the first permanent magnets 101a divided in the Z direction may be controlled so that opposite torques are generated on the upstream and downstream sides.

[0088] For example, in FIGS. 1C, 2A, and 2B, first coils 201a-1 to 201a-6 are arranged on the upstream side, and first coils 201a-7 to 201a-12 are arranged on the downstream side. First permanent magnets 101a-20 and 101a-23, each divided in the Z direction, are positioned to face first coils 201a-3 and 201a-8, respectively. The same applies to the relationship between second coil 201b and second permanent magnet 101b. In this case, to generate torque in the Z direction, a current is passed through first coil 201a, which faces first permanent magnet 101a, divided in the Z direction. If currents are passed in the same direction through both first coil 201a-3 on the upstream side and first coil 201a-8 on the downstream side, torque in the Z direction can be generated as shown in equation (3-3) above. On the other hand, for example, if a positive current flows through the upstream first coil 201a-3 and a negative current flows through the downstream first coil 201a-8, the torque generated in the Z direction on the upstream and downstream sides will be in opposite directions, resulting in a torque in the Wy direction. Note that the first coil 201a-12 also faces the first permanent magnet 101a-2, which is divided in the Z direction, so torque may be obtained by adding it in the same way.

[0089] 2A and 2B show an arrangement in which the first permanent magnets 101a-2, 101a-20, and 101a-23, which are divided in the Z direction and form the second permanent magnet row, face the first coils 201a-1 to 201a-12. When the rotor 110 rotates in the Wz direction, the first permanent magnets 101a also rotate in the Wz direction. The torque Tz in the Z direction is controlled by the current flowing through the first coils 201a that face the first permanent magnets 101a divided in the Z direction. Therefore, it is desirable to arrange the first permanent magnets 101a so that at least one of the first permanent magnets 101a divided in the Z direction faces the first coils 201a arranged in an arc when the rotor 110 rotates in the Wz direction. Due to the relative positional relationship between the first coils 201a and the first permanent magnets 101a, the torque Tz in the Z direction can be obtained without fail. That is, if first permanent magnet 101a divided in the Z direction faces one or more of first coils 201a-1 to 201a-12, torque Tz in the Z direction can be obtained regardless of the rotation angle θ of rotor 110. By configuring in this way that torque Tz in the Z direction can be obtained while rotor 110 is rotating, stable rotation control of rotor 110 can be performed. The relative positional relationship between second coil 201b and second permanent magnet 101b can also be made similar to the relative positional relationship between first coil 201a and first permanent magnet 101a described above.

[0090] Here, the upstream and downstream distances from the YZ plane to the point where the first permanent magnet 101a is divided in the Z direction are defined as h1 and h2, respectively. Note that the distances h1 and h2 change with the rotation of the rotor 110 when it is rotating.

[0091] The Z-direction torque Tza (j=1 to 6) generated in the upstream first coils 201a-1 to 201a-6 and the Z-direction torque Tzb generated in the upstream second coils 201b-1 to 201b-6 are calculated by the following equations (4-1) and (4-2), respectively. Note that Σ in equations (4-1) and (4-2) is the sum when the index j is changed from 1 to 6. Tza(j=1~6)=Σ{Eza(j,θ)*Ij}...Formula (4-1) Tzb(j=1~6)=Σ{Ezb(j,θ)*Ij} …Equation (4-2)

[0092] Furthermore, the Z-direction torque Tza (j=7 to 12) generated in the downstream first coils 201a-7 to 201a-12 can be calculated using the following equation (4-3): Furthermore, the Z-direction torque Tzb (j=7 to 12) generated in the downstream second coils 201b-7 to 201b-12 can be calculated using the following equation (4-4): where Σ in equations (4-3) and (4-4) is the sum when the index j is changed from 7 to 12. Tza(j=7~12)=Σ{Eza(j,θ)*Ij}…Formula (4-3) Tzb(j=7~12)=Σ{Ezb(j,θ)*Ij} …Equation (4-4)

[0093] Then, from equation (3-5) and equations (4-1) to (4-4), the torque Twy in the Wy direction expressed by the following equation (4-5) can be obtained. Twy=(Txa-Txb)*t+{(Tza(j=1~6)+Tzb(j=1~6))*h1-(Tza(j=7~12)+Tzb(j=7~12))*h2}...Formula (4-5)

[0094] In this way, the rotary drive device 10 according to this embodiment can apply a torque vector Tq having six-axis components to the rotor 110 using the current control system 300 as described above, thereby controlling the rotational speed and attitude of the rotor 110.

[0095] 7A and 7B are schematic diagrams showing the attractive force acting between the first permanent magnet 101a of the rotor 110 and the core 202a of the first coil 201a. The attractive force acting between the core 202a of the first coil 201a and the first permanent magnet 101a will be described with reference to FIGS. 7A and 7B. The second coil 201b and the second permanent magnet 101b have a similar configuration, and a similar attractive force acts between them.

[0096] The core 202a disposed within the first coil 201a is made of a magnetic material. Therefore, as shown in FIG. 7A, an attractive force fmar, which is a magnetic force, is generated between the core 202a and the first permanent magnet 101a. The attractive force fmar is decomposed into an attractive force fmax in the X direction and an attractive force fmay in the Y direction. The magnitude and direction of the attractive force fmar vary depending on the relative positions of the core 202a and the first permanent magnet 101a, as indicated by the arrows in FIG. 7B.

[0097] According to the configuration of this embodiment, in the Y direction, which is the direction of gravity, the resultant force obtained by adding up the Y direction attractive forces fmay acting on the first coils 201a-1 to 201a-12 becomes the attractive force Fmay generated in the gravity direction of the rotor 110.

[0098] On the other hand, in the X direction, first coils 201a-1 to 201a-6 and first coils 201a-7 to 201a-12 are arranged symmetrically with respect to the YZ plane, and therefore, attractive forces are also generated symmetrically with respect to the YZ plane. Specifically, in the X direction, attractive forces act in the positive direction in first coils 201a-1 to 201a-6, and in the negative direction in first coils 201a-7 to 201a-12. If rotor 110 is positioned at the center in the X direction, the attractive forces in the positive direction and the attractive forces in the negative direction in the X direction cancel each other out. That is, in this case, the resultant force obtained by adding together the attractive forces fmax in the X direction acting on first coils 201a-1 to 201a-6 and the resultant force obtained by adding together the attractive forces fmax in the X direction acting on first coils 201a-7 to 201a-12 are approximately equal in magnitude and cancel each other out.

[0099] In this embodiment, as described above, the first coil 201a has a core 202a, and therefore an attractive force Fmay in the Y direction acts on the rotor 110. Furthermore, the second coil 201b has a core 202b, and therefore an attractive force Fmby in the Y direction acts on the rotor 110, similar to the attractive force Fmay. The attractive forces Fmay and Fmby in the Y direction are used to levitate the rotor 110 in the Y direction. Note that the first coil 201a and the second coil 201b are not necessarily limited to cored coils having cores, and may be air-core coils. In the case of air-core coils, a torque Ty in the Y direction is used as a force to levitate the rotor 110 in the Y direction.

[0100] 8A, 8B, and 8C are schematic diagrams illustrating the state when rotor 110 is moved in the Y direction with the center position of rotor 110 in the X direction aligned with origin Os. The levitation of rotor 110 will be described with reference to FIGS. 8A to 8C.

[0101] The rotor 110 is disposed at a position where its center O overlaps with the origin Os. When the rotor 110 is moved in the Y direction, an equilibrium point e p is reached, which is a position where the magnitude of the gravity Fg of the rotor 110 and the magnitude of the attractive force Fmay+Fmby are equal. In this embodiment, the origin Os and the equilibrium point e p are configured to overlap. FIG. 8A shows a state in which the rotor 110 is disposed so that the center O of the rotor 110 overlaps with the equilibrium point e p.

[0102] For example, if the position of rotor 110 shifts in the positive Y direction from the state shown in Fig. 8A as shown in Fig. 8B, the attractive force Fmay+Fmby becomes larger than gravity Fg. On the other hand, if the position of rotor 110 shifts in the negative Y direction from the state shown in Fig. 8A as shown in Fig. 8C, gravity Fg becomes larger than attractive force Fmay+Fmby. Rotor 110 moves in the direction of the larger force, that is, in the direction of attractive force Fmay+Fmby in the case shown in Fig. 8B, and in the direction of gravity Fg in the case shown in Fig. 8C.

[0103] Therefore, the rotational driving device 10 controls the torque in the Y direction applied to the rotor 110 by causing the current control system 300 to flow through the first coil 201a and the second coil 201b at the position where the center O of the rotor 110 and the equilibrium point ep overlap. Furthermore, the rotational driving device 10 can maintain the levitation of the rotor 110 by similarly controlling the torque applied to the rotor 110 in the X direction.

[0104] To maintain the levitation of the rotor 110, it is desirable to control the torque applied to the rotor 110 at a position where the center O of the rotor 110 overlaps the equilibrium point e p. By controlling the rotor 110 at the equilibrium point e p in this manner, the levitation state of the rotor 110 can be maintained with a smaller current flowing through the first coil 201 a and the second coil 201 b. Furthermore, as described above, by passing current through the first coil 201 a and the second coil 201 b so as to generate torque in the Wz direction, the rotor 110 can be rotated in the Wz direction while remaining levitated so that the center O of the rotor 110 overlaps the equilibrium point e p. In this way, the rotary drive device 10 can rotate the rotor 110 in the Wz direction while levitating it in the Y direction by controlling the current flowing through the first coil 201 a and the second coil 201 b using the current control system 300 to control the coils relative to the rotor 110.

[0105] To position the rotor 110 so that its center O coincides with the equilibrium point ep, current is passed through the first coil 201a and the second coil 201b to control the torque Ty in the Y direction. In this case, a seating bearing 220 is required to prevent the rotor 110 from falling when the rotor 110 is not being controlled.

[0106] The seat bearing 220 will be described with reference to Figures 9A and 9B, along with the state in which the rotor 110 abuts against the seat bearing 220. Figure 9A is a cross-sectional view showing a cross section of the rotor 110 cut along the YZ plane including the central axis that includes the center O of the rotor 110, and shows the state in which the rotor 110 abuts against the seat bearing 220. Figure 9B is a side view of the state shown in Figure 9A, seen from the Z direction.

[0107] 9A and 9B, the rotary drive device 10 according to this embodiment further includes a seating bearing 220. The seating bearing 220 is provided so as to function as a support for supporting the rotor 110 when the rotor 100 is not being controlled. Specifically, the seating bearing 220 is provided at one end and the other end of the rotor 100 in the Z direction. When the rotor 100 is not being controlled, the seating bearing 220 supports the upper wall portions of the one end and the other end of the cylindrical rotor 100 in the Z direction from the hollow interior side of the rotor 100, thereby preventing the rotor 110 from falling.

[0108] In the cases shown in FIGS. 9A and 9B , the rotor 110 is located lower than the equilibrium point e p and contacts the seating bearing 220 due to gravity. The seating bearing 220 supports the contacting rotor 110 from below, preventing the rotor 110 from falling. In this case, the rotor 110 contacts the seating bearing 220 but is not fixed. Therefore, the rotor 110 can move while sliding in the X direction. In this case, if a force other than that in the direction of gravity is simultaneously applied to the rotor 110 when torque Ty is applied to the rotor 110, the rotor 110 also moves in the X direction. As a result, the rotor 110 contacts the seating bearing 220 again due to movement in the X direction, causing vibration in the rotor 110, which may result in a failure of the rotor 110 to transition from the contact state to the floating state.

[0109] The difference between a state in which the rotor 110 can stably transition to the levitated state and a state in which the rotor 110 is unstable in transition to the levitated state will be described with reference to Figures 10 to 14. Note that, although the following description will be given using the first permanent magnet 101a and the first coil 201a as an example, the same applies to the second permanent magnet 102b and the second coil 201b.

[0110] FIG. 10 shows an example of the arrangement of the first permanent magnets 101a, in which the first permanent magnets 101a for control in the Z direction are arranged every sixth magnet in the magnet row.

[0111] In this case, the first permanent magnets 101a-2 and 101a-8 are used for control in the Z direction. If a current is passed through the first coil 201a that faces these first permanent magnets 101a-2 and 101a-8, the rotor 110 will move in the Z direction. Therefore, when transitioning the rotor 110 from the contact state to the levitated state, it is necessary to apply torque Ty to the rotor 110 using a permanent magnet 101a other than the first permanent magnets 101a-2 and 101a-8.

[0112] 11A and 11B are side views of the rotary drive device 10 viewed in the Z direction, showing two example patterns of the electrical angle of the rotor 110. As will be described below, the electrical angle of the rotor 110 shown in FIG. 11A is an angle at which the arrangement of the first permanent magnets 101a has a predetermined symmetry with respect to the Y axis. The electrical angle of the rotor 110 shown in FIG. 11B is an angle at which the arrangement of the first permanent magnets 101a has a predetermined asymmetry with respect to the Y axis. The electrical angle of the rotor 110 corresponds to the position of the rotor 110 in the Wz direction, which is the direction of rotation.

[0113] In the example shown in FIG. 11A, the first permanent magnets 101a-2 and 101a-8 for control in the Z direction are arranged symmetrically with respect to the Y axis in a plan view in the Z direction. The first permanent magnet 101a-5 is also arranged on the Y axis. Therefore, the magnetic poles of the first permanent magnet 101a-5 are parallel to the direction of gravity. The first permanent magnets 101a-1, 101a-3 to 101a-7, and 101a-9 other than the first permanent magnets 101a-2 and 101a-8 are also arranged symmetrically with respect to the Y axis in a plan view in the Z direction. The first coils 201a-1 to 201-12 facing the first permanent magnets 101a-1 to 101a-9 are also arranged symmetrically with respect to the Y axis in a plan view in the Z direction. Thus, the first permanent magnets 101a-1 to 101a-9 and the first coils 201a-1 to 201-12 are arranged symmetrically with respect to the Y axis in a plan view seen in the Z direction.

[0114] In the electrical angle state shown in FIG. 11A, the first coils 201a-1, 201a-3 to 201a-10, and 201a-12 are coils capable of generating torque Ty without generating torque Tz. These first coils 201a-1, 201a-3 to 201a-10, and 201a-12 capable of generating torque Ty are arranged symmetrically with respect to the Y axis in a plan view viewed in the Z direction. Therefore, the torque Tx generated by the first coils 201a-1, 201a-3 to 201a-10, and 201a-12 can be easily canceled out among the multiple coils. As a result, in the case shown in FIG. 11A, torque Ty can be efficiently obtained without disturbance.

[0115] On the other hand, in the case shown in FIG. 11B, the first permanent magnets 101a-2 and 101a-8 for Z-direction control are arranged asymmetrically with respect to the Y-axis in a planar view in the Z-direction. In this case, unlike the case shown in FIG. 11A, the first coils 201a-2 to 201a-9, 201a-11, and 201a-12 are coils that can generate torque Ty without generating torque Tz. These first coils 201a-2 to 201a-9, 201a-11, and 201a-12 are arranged asymmetrically with respect to the Y-axis in a planar view in the Z-direction. Therefore, if the same current is applied to all of the first coils 201a, torque Tx in the X-direction is generated. Therefore, it is necessary to balance the torque Tx by weakening the current applied to some of the multiple first coils 201a. As a result, in the state shown in FIG. 11B, the state of the device is more likely to become unstable when the rotor 110 transitions from a state in which it is in contact with the seating bearing 220 to a floating state, due to disturbances caused by the generation of torque Tx and a decrease in torque Ty caused by weakening the current, compared to the state shown in FIG. 11A.

[0116] The levitation stability of the rotor 110 when levitated from the electrical angle state shown in Fig. 11A will be compared with the levitation stability of the rotor 110 when levitated from the electrical angle state shown in Fig. 11B and will be described using Figs. 12A to 14. Figs. 12A and 12B are graphs showing example data for position control of the rotor 110 shown in Figs. 11A and 11B, respectively. Figs. 13A and 13B are graphs showing data for current control in Figs. 12A and 12B, respectively. Fig. 14 is a flowchart showing the levitation procedure performed by the levitation procedure executer 302 shown in Fig. 4.

[0117] 12A and 12B, the vertical axis represents the position of the rotor 110 in the X direction, and the horizontal axis represents the time axis, with 0 seconds representing the time when position control of the rotor 110 in the Y direction begins. FIGS. 12A and 12B also show a position command value 801x and an X position 802x. The position command value 801x is an X direction position command value generated by the position controller 301 shown in FIG. 4. The X position 802x represents the X position of the rotor 110 detected by the X sensor 213 shown in FIG. 4. The X position 802x is used as feedback (denoted as FB in the figures) to the position controller 301. Hereinafter, the position detected by the sensor will be referred to as the FB position. By performing control according to the procedure shown in FIG. 14, the position command value 801x and the FB position 802x transition over time as shown in FIGS. 12A and 12B. In accordance with the transition of the position command value 801x shown in FIGS. 12A and 12B, the current command value 803 by the position controller 301 transitions as shown in FIGS. 13A and 13B, respectively.

[0118] The levitation procedure for levitating rotor 110 will be described with reference to Fig. 14 as well as Figs. 12A and 12B. Fig. 14 is a flowchart showing the levitation procedure for rotor 110. The levitation procedure shown in Fig. 14 is executed by levitation procedure executor 302.

[0119] As shown in FIG. 14, the floating procedure execution unit 302 acquires the current position of the rotor 110 from the Z sensor 210, the Wz sensor 211, the X sensor 213, and the Y sensor 214 via the position controller 301 (step S701).

[0120] Next, the floating procedure executer 302 sets the acquired current position as a target position and enables position control of the rotor 110 in all axial directions (step S702). All axial directions include the X direction, Y direction, Z direction, Wx direction, Wy direction, and Wz direction. Here, when the rotor 110 is in contact with the seating bearing 220, the rotor 110 is supported by the seating bearing 220 in addition to being positionally controlled, and therefore the position of the rotor 110 is stable.

[0121] Next, in order to transition the rotor 110 from the seated state to the levitated state, the target position in the Y direction in the position control is changed to the equilibrium point (step S703). In FIGS. 12A and 12B, this point in time is time 0 seconds. When the rotor 110 begins to levitate following the change in the target position in the Y direction, the support provided by the seating bearing 220 is lost, causing an unintended fluctuation in the position of the rotor 110 in the X direction. Because this position fluctuation in the X direction can be corrected by position control, the levitation procedure executer 302 waits until a certain time has elapsed (step S704). In the example of FIGS. 12A and 12B, the period from time 0 seconds to 1 second is the period of step S704.

[0122] In the section of step S704, there is a difference in the behavior of rotor 110 between the case shown in FIG. 12A and the case shown in FIG. 12B.

[0123] 12A, the arrangement of first permanent magnets 101 shown in Fig. 11A is symmetrical with respect to the Y axis in a plan view seen in the Z direction, so that torque Tx in the X direction caused by application of torque Ty in the Y direction is unlikely to occur, making it easy to control the rotor 110 in the X direction. Therefore, although FB position 802x temporarily deviates from position command value 801x, after one second has elapsed, it can be returned to the vicinity of position command value 801x by position control.

[0124] 12B, the arrangement of the first permanent magnets 101 shown in FIG. 11B is asymmetric with respect to the Y axis in a plan view in the Z direction, so that torque Tx in the X direction is generated while torque Ty in the Y direction is being applied. As a result, FB position 802x cannot return to the vicinity of position command value 801x, and steady-state deviation 804x, which is the steady-state difference between FB position 802x and position command value 801x, is generated.

[0125] Next, as shown in FIG. 14, the floating procedure executing unit 302 changes the target position in the X direction in the position control to the origin Os, which is the center of rotation of the rotor 110 (step S705). The target position in the X direction before step S705 was the position read by the sensor before the start of position control, so that position depended on the usage state of the rotor 110 immediately before and was not reproducible. In contrast, after step S705, the target position is changed to the center of rotation, so the target position remains the same even when the operation is repeated. Therefore, in the cases shown in FIGS. 12A and 12B, the X direction position command values ​​801x at time 0 second do not match, but after time 2 seconds, they match.

[0126] 12A, the FB position 802x can follow the change in the position command value 801x. On the other hand, in the case shown in FIG. 12B, a deviation continues to occur between the position command value 801x and the FB position 802x even after the change in the position command value 801x, resulting in a steady-state deviation 804x.

[0127] After changing the target position in the X direction to the center of rotation, the floating procedure executer 302 repeatedly determines whether a predetermined time has elapsed (step S706) and whether the deviation between the position command value 801x and the FB position 802x is within a predetermined set value (step S707).

[0128] If it is determined that a certain period of time has not elapsed (step S706, NO) and that the deviation is within the set value (step S707, YES), the floating procedure executer 302 determines that the rotor 110 has moved to the center of rotation and has successfully transitioned from the seated state to the floating state.

[0129] On the other hand, if it is determined that the deviation is not within the set value (step S707, NO) and that a certain time has elapsed (step S706, YES), the floating procedure executer 302 determines that floating has failed and abnormally terminates the control of the rotor 110 (S708). In the case shown in FIG. 12B, a steady-state deviation 804x has occurred. Therefore, in the case shown in FIG. 12B, it is highly likely that the floating procedure executer 302 needs to be configured so that, depending on the magnitude of the steady-state deviation 804x, it determines that the rotor 110 cannot rotate due to eccentricity and determines that an abnormal termination has occurred.

[0130] The effect of the steady-state deviation 804 x also appears in the current command value 803 calculated by the current calculator 502 .

[0131] Fig. 13A shows the transition of current command value 803 on the same time axis as Fig. 12A. In this case, when transitioning from the seated state to the levitated state, current command value 803 rises once as rotor 110 moves in the X direction in Fig. 12A, but after the position of rotor 110 in the X direction reaches the target position, current command value 803 remains at approximately 0. This indicates that after transitioning to the levitated state, rotor 110 can be stably levitated at the center of rotation even with almost no current flowing through coil 201.

[0132] On the other hand, FIG. 13B shows the transition of the current command value 803 on the same time axis as FIG. 12B. In this case, the current command value 803 does not return to 0, and it is necessary to continue to flow current to the coil 201 so that the rotor 110 remains near the center of rotation. Even though current continues to flow to the coil 201, steady-state deviation 804x remains in FIG. 12B. The current steadily flowing through the coil 201 to generate torque Tx uses part of the current capacity of the coil 201. As a result, the proportion of the current generating torque Ty to the total current decreases. Here, the proportion of the current that can contribute to torque Ty relative to the current capacity of the coil 201 is defined as the levitation force. The levitation force on the rotor 110 is used to evaluate the stability of levitation of the rotor 110. The levitation force can also be defined as a force in the Y direction acting on the rotor 110 corresponding to the proportion of the current that can contribute to torque Ty relative to the current capacity of the coil 201. The levitation force is based on the electrical angle of the rotor 110 , and specifically, varies depending on the electrical angle of the rotor 110 .

[0133] In position controller 301, it is possible to reduce steady-state deviation 804x by increasing the gain during control and thereby increasing the value of the current flowing through coil 201. However, this would result in issues such as increased power consumption and the risk of oscillation due to the increased gain. For this reason, it is not possible to simply increase the gain of position controller 301. A method is required to levitate rotor 110 from seating bearing 220 at a position where steady-state deviation 804x does not occur.

[0134] Therefore, in this embodiment, a procedure for rotating the rotor 110 in the Wz direction while it remains in contact with the seating bearing 220 is added to the levitation procedure shown in Fig. 14, thereby preventing the steady-state deviation 804x from occurring. Fig. 15 shows a flowchart with the procedure for rotating the rotor 110 in the Wz direction added. The levitation procedure shown in Fig. 15 is executed by the levitation procedure executer 302.

[0135] In the levitation procedure shown in Fig. 15, in addition to the procedures from step S701 to step S707 shown in Fig. 14, a procedure (step S710) of rotating the rotor 110 before levitation is added between the procedures from step S702 to step S703. The procedure from step S710 includes the procedures from step S801 to step S806. Details of the procedure from step S801 to step S806 will be explained in order.

[0136] The electrical angle of the rotor 110 is determined from the current position of the rotor 110 acquired in step S701. Therefore, the levitation procedure executer 302 determines the electrical angle of the rotor 110 from the current position of the rotor 110 acquired in step S701, and refers to data on the levitation force corresponding to that electrical angle (step S801). Here, the levitation force data is obtained by measuring the levitation force of the rotor 110 at each electrical angle in advance during the adjustment of the rotary drive device 10, and storing this data in a table. The levitation procedure executer 302 can refer to data on the levitation force of the rotor 110 stored in a storage device (not shown). Note that the levitation force data is not limited to data acquired by measurement, but may be data calculated based on design values ​​of a magnetic circuit determined from the positional relationship between the stator 200 and the rotor 110.

[0137] Next, the lift procedure execution unit 302 determines whether the lift force data obtained by the reference is equal to or greater than a predetermined constant value (step S802).

[0138] If it is determined that the levitation force data is equal to or greater than a certain value (YES in step S802), the levitation procedure executer 302 terminates the procedure of step S710 midway. As illustrated in FIG. 11A, if the arrangement of the permanent magnets 101 is symmetrical with respect to the Y axis in a plan view in the Z direction, the steady-state deviation in the X direction when the rotor 110 is levitated is small enough to be negligible. Therefore, in such a case, most of the current capacity of the coil 201 can be allocated to the torque Ty, and the levitation force is equal to or greater than a certain value. Therefore, the levitation force is sufficiently ensured, and the rotor 110 can be stably levitated with the current electrical angle maintained. Therefore, in a case such as the example illustrated in FIG. 11A where it is determined that the levitation force data is equal to or greater than a certain value, the levitation procedure executer 302 terminates the procedure of step S710 midway.

[0139] On the other hand, if it is determined that the levitation force data is less than the certain value (step S802, NO), the levitation procedure executer 302 searches the levitation force data for an electrical angle that is equal to or greater than the certain value and that is closest to the current electrical angle (step S803). The electrical angle searched here is for rotating the rotor 110 before levitation.

[0140] The candidate electrical angles found in step S803, i.e., candidate target positions in the Wz direction, include electrical angles at which the arrangement of the permanent magnets 101 is symmetrical with respect to the Y axis in a plan view in the Z direction. There are two possible electrical angle candidates: an electrical angle at which the first permanent magnets 101a-2 and 101a-8 for Z direction control are symmetrical with respect to the Y axis in a plan view in the Z direction, as illustrated in FIG. 11A , and an electrical angle at which the first permanent magnet 101a-8 for Z direction control overlaps the Y axis. However, in the latter case, the two first coils 201a-6 and 201a-7 that can most efficiently transmit torque Ty to the rotor 110 face the first permanent magnet 101a-8 for Z direction control, resulting in a lower levitation force compared to the former case. Therefore, the electrical angle illustrated in FIG. 11A is found and selected as an electrical angle at which the levitation force is high.

[0141] Next, the levitation procedure executer 302 changes the target position in the Wz direction of the position controller 301 to the value of the electrical angle found in step S803 (step S804). In response to the change in the target position in the Wz direction, the position controller 301 starts rotating the rotor 110 in the Wz direction. That is, in the case of an arrangement of the permanent magnets 101 that is asymmetric with respect to the Y axis in a plan view seen in the Z direction as illustrated in FIG. 11B, the position controller 301 starts rotating the rotor 110 in the Wz direction while the rotor 110 remains in contact with the seating bearing 220. At this time, in order to reduce friction between the rotor 110 and the seating bearing 220, the position controller 301 may apply a torque Ty in the Y direction to the rotor 110 to the extent that the rotor 110 does not levitate.

[0142] After changing the target position in the Wz direction, the floating procedure executer 302 repeatedly determines whether a predetermined time has elapsed (step S805) and whether the deviation between the position command value in the Wz direction and the FB position is within a predetermined set value (step S806).

[0143] If it is determined that the certain time has not elapsed (step S805, NO) and that the deviation in the Wz direction is within the set value (step S806, YES), the levitation procedure executer 302 confirms that the movement to the target electrical angle has been completed and ends the procedure of step S710. This completes the rotation of the rotor 110 to the electrical angle at which the levitation force is equal to or greater than a certain value.

[0144] On the other hand, if it is determined that the deviation in the Wz direction is not within the set value (step S806, NO) and that a certain time has elapsed (step S805, YES), the floating procedure executer 302 ends the procedure of step S710. In this case, the deviation in the Wz direction does not fall within the set value within the certain time, resulting in a timeout determination. However, the timeout determination is likely due to friction between the rotor 110 and the seating bearing 220, and even if the deviation in the Wz direction is not within the set value, there is still a possibility that the rotor 110 can be successfully floated. For this reason, even if a timeout determination is made, the floating procedure executer 302 does not determine that an abnormality has occurred and ends the procedure of step S710.

[0145] After the procedure of step S710 is completed, the floating procedure execution unit 302 executes the procedure of steps S703 to S707 in the same manner as in the case shown in FIG.

[0146] As described above, in this embodiment, in the procedure of step S710 in Fig. 15, the levitation force at the electrical angle of the rotor 110 to be controlled is confirmed before levitation begins. If it is determined that the levitation force is insufficient as a result, the rotor 110 is rotated in advance while remaining in the seated state to change the electrical angle. This prevents the X-direction torque Tx from being applied to the rotor 110 at the start of levitation, which would otherwise cause steady-state deviation or oscillation, and also makes it possible to efficiently transmit the Y-direction torque Ty to the rotor 110. In this way, according to this embodiment, the rotor 110 can be stably transitioned from a seated state to a levitated state while avoiding an increase in the size of the entire rotary drive device 10.

[0147] 15, the rotor 110 is rotated before levitation. However, the rotor 110 may be rotated and stopped in advance at the end of levitation in preparation for the next levitation. Specifically, when transitioning the rotor 110 from a levitated state to a seated state in which the rotor 110 abuts against the seating bearing 220, the levitation procedure executer 302 may rotate the rotor 110 to an electrical angle that will result in a levitation force equal to or greater than a certain value when the rotor 110 is supported by the seating bearing 220. After rotation, the levitation procedure executer 302 can stop the rotor 110 by supporting it on the seating bearing 220, thereby ending control of the rotor 110. In this case, since it is not necessary to rotate the rotor 110 at the start of levitation, the waiting time when using the rotary drive device 10 can be shortened.

[0148] [Second embodiment] A rotation drive device according to a second embodiment of the present invention will be described with reference to Figures 16A to 17. Note that components similar to those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0149] The basic configuration of the rotary drive device 10 according to this embodiment and the basic method of controlling the rotor 110 are the same as those according to the first embodiment. The arrangement of the first permanent magnets 101 is the same as that shown in Fig. 10 in the first embodiment. In this embodiment, a case will be described in which the coils 201 serving as the magnetic force portion are not arranged at equal intervals.

[0150] When arranging magnetic parts such as coils on a stator, it is ideal to arrange the magnetic parts at equal intervals in order to reduce cogging torque. However, in reality, there are cases where it is not possible to arrange the magnetic parts at equal intervals due to restrictions on the arrangement of equipment within the device.

[0151] FIG. 16A shows an example in which the coils 201 cannot be arranged at equal intervals in the configuration shown in FIG. 11A. Comparing FIG. 11A and FIG. 16A, the structures of the rotor 110 are the same. On the other hand, in the structure of the stator 200 in FIG. 16A, the first coil 201a-4 is not arranged due to interference with equipment within the device, resulting in a gap 205. Thus, in the multiple first coils 201a shown in FIG. 16A, gaps 205 are formed between adjacent first coils 201a. In this respect, the arrangement of the first coils 201a shown in FIG. 16A is asymmetric with respect to the Y axis in a plan view seen from the Z direction, unlike the arrangement shown in FIG. 11A.

[0152] The magnetic resistance is low in the portion where the coil 201 is disposed due to the presence of the core of the coil 201. On the other hand, the magnetic resistance is high in the gap portion 205. As a result, an attractive force is generated between the first permanent magnet 101a-3 and the core in the first coil 201a-3, and a torque in the -Wz direction is generated in the rotor 110 even when no current is applied to the first coil 201a. However, when the rotor 110 is in contact with the seat bearing 220, friction is generated between the rotor 110 and the seat bearing 220, so the rotor 110 remains stationary even when a torque in the -Wz direction is generated.

[0153] 14 from the state shown in FIG. 16A, after executing step S703, which changes the target position in the Y direction to the equilibrium point, the rotor 110 lifts off the seating bearing 220. This eliminates friction between the rotor 110 and the seating bearing 220. Then, at the moment of lifting, torque in the -Wz direction suddenly acts on the rotor 110, causing the rotor 110 to vibrate significantly. A method is needed to stably lift the rotor 110 off the seating bearing 220 while preventing the rotor 110 from vibrating at the moment of lifting.

[0154] Therefore, in this embodiment, a procedure for rotating the rotor in the Wz direction while it is in contact with the seating bearing 220 is added to the levitation procedure shown in FIG. 14 to prevent the generation of cogging torque on the rotor 110. The cogging torque on the rotor 110 includes torque in the X direction and the Wz direction. The cogging torque is based on the electrical angle of the rotor 110, and more specifically, varies depending on the electrical angle of the rotor 110. A flowchart in which the procedure for rotating the rotor 110 in the Wz direction is added is shown in FIG. 17. The levitation procedure shown in FIG. 17 is executed by the levitation procedure executer 302.

[0155] In the levitation procedure shown in Fig. 17, in addition to the procedures from step S701 to step S707 shown in Fig. 14, a procedure (step S711) of rotating rotor 110 before levitation is added between the procedures from step S702 to step S703. The procedure of step S711 includes the procedures from step S901 to step S905. Details of the procedure of step S711 will be explained in the order of the procedures from step S901 to step S905.

[0156] The electrical angle of the rotor 110 is determined from the current position of the rotor 110 acquired in step S701. Therefore, the levitation procedure executer 302 determines the electrical angle of the rotor 110 from the current position of the rotor 110 acquired in step S701, and refers to the cogging torque data corresponding to that electrical angle (step S901). Here, the cogging torque data for the rotor 110 is obtained by measuring the cogging torque for the rotor 110 at each electrical angle in advance during the adjustment of the rotary drive device 10, and creating a table from the measured data. Note that the cogging torque data is not limited to data acquired by measurement, and may be data calculated based on design values ​​of a magnetic circuit determined from the positional relationship between the stator 200 and the rotor 110.

[0157] Next, the levitation procedure execution unit 302 determines whether the cogging torque data obtained by reference is less than a predetermined constant value (step S902).

[0158] If the levitation procedure executer 302 determines that the cogging torque data is less than the predetermined value (YES in step S902), it terminates the procedure of step S711 midway. In the example illustrated in FIG. 16B, the multiple first permanent magnets 101a are arranged so that one first permanent magnet 101a does not face both the first coils 201a-3 and 201a-5 adjacent to the gap 205 and the gap 205. In this way, when there are no permanent magnets 101 partially facing the gap 205 and the coil 201, it is possible to suppress the cogging torque to the same level as when there is no gap 205 in the coil 201. In this case, the value of the cogging torque is less than the predetermined value. Therefore, it is possible to stably levitate the rotor 110 with the current electrical angle maintained. Therefore, in the example illustrated in FIG. 16B where the cogging torque data is determined to be less than the predetermined value, the levitation procedure executer 302 terminates the procedure of step S711 midway.

[0159] On the other hand, if it is determined that the cogging torque data is equal to or greater than the certain value (step S902, NO), the levitation procedure executer 302 searches the cogging torque data for an electrical angle that makes the cogging torque less than the certain value and is closest to the current electrical angle (step S903). The electrical angle found here is the angle for rotating the rotor 110 before levitation. As illustrated in FIG. 16A, when the first permanent magnet 101a-3 partially faces the first coil 201a-3 near the gap 205 of the first coil 201a, the cogging torque has a large value. In such a case, it is determined that the cogging torque data is equal to or greater than the certain value.

[0160] The electrical angle candidates found in step S903, i.e., the target position candidates in the Wz direction, include an electrical angle in which the first permanent magnet 101a is arranged so as not to partially face the first coil 201a, as illustrated in Fig. 16B. Even if such an arrangement does not exist in the design of the device, the cogging torque is reduced at an electrical angle in which the torque in the Wz direction generated between each permanent magnet 101 and coil 201 is canceled out in opposite directions (positive and negative). Therefore, an electrical angle in which the torque in the Wz direction generated between the multiple permanent magnets 101 and the multiple coils 202 is canceled out in this way is also included as a candidate for the target position.

[0161] Next, the levitation procedure executer 302 changes the target position in the Wz direction of the position controller 301 to the value of the electrical angle found in the procedure of step S903 (step S904). In response to the change in the target position in the Wz direction, the position controller 301 starts rotating the rotor 110 in the Wz direction. That is, the position controller 301 starts rotating the rotor 110 in the Wz direction while the rotor 110 remains in contact with the seating bearing 220. At this time, in order to reduce friction between the rotor 110 and the seating bearing 220, the position controller 301 may apply a torque Ty in the Y direction to the rotor 110 to the extent that the rotor 110 does not levitate.

[0162] After changing the target position in the Wz direction, the floating procedure executer 302 repeatedly determines whether a predetermined fixed time has elapsed (step S905). If it determines that the fixed time has elapsed (step S905, YES), the floating procedure executer 302 confirms that movement to the electrical angle set as the target position has been completed, and ends the procedure of step S711. This completes the rotation of the rotor 110 to an electrical angle at which the cogging torque becomes less than a fixed value.

[0163] After the procedure of step S711 is completed, the floating procedure execution unit 302 executes the procedure of steps S703 to S707 in the same manner as in the case shown in FIG.

[0164] As described above, in this embodiment, in the procedure of step S711 in FIG. 17, the cogging torque at the electrical angle of the rotor 110 to be controlled is checked before levitation begins. As a result, if it is determined that the cogging torque is large and will affect the realization of stable levitation, the rotor 110 is rotated in advance while remaining in the seated state to change the electrical angle. This makes it possible to suppress the application of torque in the X direction and Wz directions due to cogging to the rotor 110 at the start of levitation, and to prevent oscillation of the rotor 110. In this way, according to this embodiment, the rotor 110 can be stably transitioned from a seated state to a levitated state while avoiding an increase in the size of the entire rotary drive device 10.

[0165] The procedure for levitating the rotor 110 shown in FIG. 17 can be performed not only when the coil 201 has a gap 205, but also when the coil 201 does not have a gap 205, as exemplified in FIG. 11A of the first embodiment.

[0166] 16A and 16B , the arrangement of the coils 201 in the stator 200 may be asymmetric with respect to the Y-axis in a plan view in the Z direction, or the coils 201 may be slightly misaligned during assembly of the device even if they are line-symmetric in design. In these cases, to keep the rotor 110 levitated from the origin Os, which is the center of rotation, it is necessary to continuously apply torque Tx or torque Ty to the rotor 110. In these cases, it is desirable to keep the rotor 110 levitated at a magnetic equilibrium point rather than at the center of the coordinate system. Therefore, after transitioning from the seated state to the levitated state, switching the control of the rotor 110 from position control to zero power control is also effective in stabilizing the levitation of the rotor 110.

[0167] 17, the rotor 110 is rotated before levitation. However, the rotor 110 may be rotated and stopped in advance at the end of levitation in preparation for the next levitation. Specifically, when transitioning the rotor 110 from a levitated state to a seated state in which the rotor 110 abuts against the seating bearing 220, the levitation procedure executer 302 may rotate the rotor 110 to an electrical angle at which the cogging torque becomes less than a certain value when the rotor 110 is supported by the seating bearing 220. After the rotation, the levitation procedure executer 302 stops the rotor 110 by supporting it on the seating bearing 220, and can terminate control of the rotor 110. In this case, since it is not necessary to rotate the rotor 110 at the start of levitation, the waiting time when using the rotary drive device 10 can be shortened.

[0168] [Third embodiment] A rotating device according to a third embodiment of the present invention will be described with reference to Fig. 18. Note that the same components as those in the first and second embodiments are given the same reference numerals, and descriptions thereof will be omitted or simplified.

[0169] The rotary drive device 10 according to the above embodiment can be used in a rotary device that utilizes the rotation of the rotor 110. In this embodiment, an X-ray computed tomography (CT) device will be described as an example of a rotary device that uses the rotary drive device 10 according to the above embodiment.

[0170] Fig. 18 is a side view showing an X-ray CT apparatus 600 that uses the rotation drive device 10 according to the first embodiment. Fig. 18 corresponds to the side view of the rotation drive device 10 according to the first embodiment shown in Fig. 1B.

[0171] 18 , the X-ray CT apparatus 600 includes the rotary drive device 10 according to the first embodiment, a plate-shaped unit 602, an X-ray irradiation unit 604, an X-ray detection unit 606, a signal amplification unit 608, a cooling unit 610, power supply units 612 and 614, and a power supply control unit 616. The rotary drive device 10 is mounted on a stand (not shown). The plate-shaped unit 602, the X-ray irradiation unit 604, the X-ray detection unit 606, the signal amplification unit 608, the cooling unit 610, the power supply units 612 and 614, and the power supply control unit 616 are each components mounted on the rotor 110 of the rotary drive device 10.

[0172] The plate-shaped portion 602 is an annular plate-shaped member installed inside the cylindrical rotor 110 along the XY plane. An imaging opening 618 is provided in the center of the plate-shaped portion 602, into which a subject, such as a human or other living organism, to be subjected to X-ray CT, is inserted. The imaging opening 618 is a circular opening centered on the Z axis, which is the rotation axis of the rotor 110. As the rotor 110 rotates in the Wz direction around the Z axis, the plate-shaped portion 602 also rotates in the Wz direction around the Z axis.

[0173] The manner in which the subject is inserted into the imaging opening 618 is not particularly limited, but for example, a bed (not shown) on which the subject lies slides along the Z direction into the imaging opening 618, thereby inserting the subject into the imaging opening 618. The subject is inserted into the imaging opening 618 and placed inside the rotator 110. Note that the subject is not necessarily limited to a living organism such as a human being, and may be an article such as an industrial product.

[0174] The X-ray irradiation unit 604, the X-ray detection unit 606, the signal amplification unit 608, the cooling unit 610, the power supply units 612 and 614, and the power supply control unit 616 are each attached to one surface in the Z direction of the plate-shaped unit 602. The X-ray irradiation unit 604, the X-ray detection unit 606, the signal amplification unit 608, the cooling unit 610, the power supply units 612 and 614, and the power supply control unit 616 rotate in the Wz direction around the Z axis as the rotation axis when the plate-shaped unit 602 rotates in accordance with the rotation of the rotor 110 by the rotary drive device 10. Note that each of these units may be attached to one or the other surface or both surfaces in the Z direction of the plate-shaped unit 602. Furthermore, each of these units may be disposed between multiple coil arrays.

[0175] The X-ray irradiation unit 604 and the X-ray detection unit 606 are installed on the same plane in the Z direction of the plate-shaped unit 602. The X-ray irradiation unit 604 and the X-ray detection unit 606 are arranged in the diameter direction of the annular plate-shaped unit 602 so as to face each other across the Z axis, which is the axis of rotation of the annular plate-shaped unit 602.

[0176] The X-ray irradiator 604 is an irradiator that irradiates a subject placed inside the rotor 110 with X-rays, which are radiation, toward the subject while the rotor 110 makes one rotation around the subject. The X-ray irradiator 604 is, for example, an X-ray tube. The power supply units 612 and 614 are power supply devices that supply voltages for X-ray irradiation, such as tube voltage for the X-ray tube, to the X-ray irradiator 604. The power supply control unit 616 is a control device that controls the supply of tube voltages by the power supply units 612 and 614. The cooling unit 610 is a cooling device that cools the X-ray irradiator 604, which generates heat when irradiating X-rays.

[0177] The X-ray detection unit 606 is a detector that detects X-rays that are irradiated from the X-ray irradiation unit 604 toward the subject and that have passed through the subject. The X-ray detection unit 606 outputs a detection signal corresponding to the detected X-rays. The signal amplification unit 608 amplifies the detection signal output from the X-ray detection unit 606. The signal amplification unit 608 outputs the amplified detection signal to a system control unit (not shown). The system control unit generates an X-ray CT image by image processing or the like based on the detection signal from the signal amplification unit 608.

[0178] In this way, in the X-ray CT apparatus 600, the rotation drive device 10 can be used as a device that rotates the rotor 110 to rotate the X-ray irradiation unit 604, the X-ray detection unit 606, and the like.

[0179] In this embodiment, the X-ray CT device 600 using X-rays has been described, but it is also possible to configure a CT device using radiation such as gamma rays instead of X-rays. In this case, an irradiation unit according to the type of radiation can be used instead of the X-ray irradiation unit 604, and a detection unit according to the type of radiation can be used instead of the X-ray detection unit 606.

[0180] Moreover, the rotation drive device 10 according to the second embodiment can also be used in an X-ray CT apparatus.

[0181] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above embodiment, the first and second permanent magnets 101a, 101b are used as the first magnetic force portion of the rotor 110, and the first and second coils 201a, 201b are used as the second magnetic force portion of the stator 200. However, the present invention is not limited to this. It is also possible to use a coil as the first magnetic force portion of the rotor 110, and a permanent magnet or a coil as the second magnetic force portion of the stator 200. In this case, the current control system 300 can control the drive of the rotor 110 in the same manner as in the above embodiment by controlling the current applied to the coil of the rotor 110 or the stator 200.

[0182] Furthermore, in the above embodiment, the X-ray CT scanner 600 has been described as an example of a rotating device that uses the rotary drive device 10, but the present invention is not limited to this. As a rotating device that uses the rotary drive device 10, not only the X-ray CT scanner 600 but also any other device can be configured. Furthermore, depending on the type of rotating device, components that are installed on the rotor 110 and rotate together with the rotor 110 can be designed.

[0183] The present invention can also be realized by supplying a program that realizes one or more functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program. It can also be realized by a circuit (e.g., ASIC) that realizes one or more functions.

[0184] The disclosure of this embodiment includes the following configurations and methods. (Configuration 1) a rotor having a first magnetic portion and rotatable in a rotation direction about a rotation axis intersecting the direction of gravity; a stator having a second magnetic portion; a support portion that supports the rotor located at a first position; a control unit; the first magnetic force portion is arranged circumferentially along the rotation direction on the outer peripheral side surface of the rotor, the second magnetic force portion is disposed above the rotor in an arc shape along the rotation direction, When the rotor is located at the first position and a levitation force on the rotor is less than a predetermined value, the control unit rotates the rotor to a second position where the levitation force is equal to or greater than a predetermined value, and levitates the rotor from the second position. A rotary drive device characterized by: (Configuration 2) When the rotor is located at the first position, the control unit levitates the rotor from the first position when the levitation force is equal to or greater than the predetermined value. 2. The rotary drive device according to configuration 1, (Configuration 3) the second magnetic force unit includes a plurality of coils, The plurality of coils are arranged symmetrically with respect to the axis along the direction of gravity in a plan view seen in a direction along the rotation axis. 3. The rotary drive device according to configuration 1 or 2. (Configuration 4) the first magnetic force portion includes a plurality of permanent magnets, At the second position, the plurality of permanent magnets are arranged symmetrically with respect to the axis along the direction of gravity in a plan view seen in a direction along the rotation axis. 4. The rotary drive device according to any one of configurations 1 to 3. (Configuration 5) In the second position, the orientation of a magnetic pole of one of the plurality of permanent magnets is parallel to the direction of gravity. 5. The rotary drive device according to configuration 4. (Configuration 6) the plurality of permanent magnets include a first magnet group in which magnetic poles are alternately arranged in the rotation direction, and a second magnet group in which magnetic poles are alternately arranged in a direction intersecting the rotation direction, At the second position, the second magnet group is arranged symmetrically with respect to an axis along the direction of gravity. 6. The rotary drive device according to configuration 4 or 5, (Configuration 7) The levitation force varies depending on the electrical angle of the rotor. 7. The rotary drive device according to any one of configurations 1 to 6. (Configuration 8) The control unit rotates the rotor to a position where a levitation force on the rotor becomes equal to or greater than a predetermined value when the rotor is supported by the support unit, and then stops the rotor by supporting it with the support unit. 8. The rotation drive device according to any one of configurations 1 to 7. (Configuration 9) a rotor having a first magnetic portion and rotatable in a rotation direction about a rotation axis intersecting the direction of gravity; a stator having a second magnetic portion; a support portion that supports the rotor located at a first position; a control unit; the first magnetic force portion is arranged circumferentially along the rotation direction on the outer peripheral side surface of the rotor, the second magnetic force portion is disposed above the rotor in an arc shape along the rotation direction, When the rotor is located at the first position and a cogging torque on the rotor is equal to or greater than a predetermined value, the control unit rotates the rotor to a second position where the cogging torque becomes less than the predetermined value, and levitates the rotor from the second position. A rotary drive device characterized by: (Configuration 10) When the rotor is located at the first position and the cogging torque is less than the predetermined value, the control unit levitates the rotor from the first position. 10. The rotary drive device according to configuration 9, (Configuration 11) the second magnetic force unit includes a plurality of coils, The plurality of coils are arranged asymmetrically with respect to the axis along the direction of gravity in a plan view seen in a direction along the rotation axis. 11. The rotary drive device according to configuration 9 or 10. (Configuration 12) In the plurality of coils, a gap is formed between adjacent coils, the first magnetic force portion includes a plurality of permanent magnets, At the second position, the plurality of permanent magnets are arranged so that one permanent magnet does not face both the coil adjacent to the gap and the gap. 12. The rotary drive device according to claim 11, (Configuration 13) the first magnetic force portion includes a plurality of permanent magnets, At the second position, the torques in the rotation direction generated between the plurality of permanent magnets and the plurality of coils are canceled out. 12. The rotary drive device according to claim 11, (Configuration 14) The cogging torque varies depending on the electrical angle of the rotor. 14. The rotation drive device according to any one of configurations 9 to 13. (Configuration 15) The control unit rotates the rotor to a position where a cogging torque on the rotor becomes less than a predetermined value when the rotor is supported by the support unit, and then stops the rotor by supporting it on the support unit. 15. The rotation drive device according to any one of configurations 9 to 14. (Method 1) A method for controlling a rotary drive device comprising: a rotor having a first magnetic force portion and rotatable in a rotation direction about a rotation axis that intersects with a direction of gravity; a stator having a second magnetic force portion; and a support portion that supports the rotor located at a first position, wherein the first magnetic force portion is disposed circumferentially along the rotation direction on an outer peripheral side surface of the rotor, and the second magnetic force portion is disposed above the rotor in an arc shape that also follows the rotation direction, When the rotor is located at the first position and the levitation force on the rotor is less than a predetermined value, the rotor is rotated to a second position where the levitation force is equal to or greater than the predetermined value, and the rotor is levitated from the second position. A method for controlling a rotary drive device. (Method 2) A method for controlling a rotary drive device comprising: a rotor having a first magnetic force portion and rotatable in a rotation direction about a rotation axis that intersects with a direction of gravity; a stator having a second magnetic force portion; and a support portion that supports the rotor located at a first position, wherein the first magnetic force portion is disposed circumferentially along the rotation direction on an outer peripheral side surface of the rotor, and the second magnetic force portion is disposed above the rotor in an arc shape that also follows the rotation direction, When the rotor is located at the first position and a cogging torque applied to the rotor is equal to or greater than a predetermined value, the rotor is rotated to a second position where the cogging torque becomes less than the predetermined value, and the rotor is levitated from the second position. A method for controlling a rotary drive device. (Configuration 16) The rotation drive device according to any one of configurations 1 to 15, Components installed on the rotor; A rotating device comprising: (Configuration 17) The components include: an irradiation unit that irradiates radiation toward a subject disposed inside the rotor; a detection unit that is disposed opposite the irradiation unit across the rotation axis and detects the radiation that has passed through the subject; 17. The rotating device according to claim 16, comprising: [Explanation of symbols]

[0185] 110 Rotor 101a first permanent magnet 101b Second permanent magnet 102 York 200 Stator 201a First coil 201b Second coil 202a, 202b Core 203a, 203b Windings 204a, 204b Side yoke 210a, 210b, 210c Z sensors 211 Wz sensor 212 scale 213 X Sensor 214 Y sensor 220 Seating bearing 300 Current Control System 301 Position Controller 302 Levitation Procedure Executor 312a, 312b Current sensors 313a, 313b Current controller 501 Attitude Controller 502 Current Calculator 605 Torque Controller

Claims

1. a rotor having a first magnetic portion and rotatable in a rotation direction about a rotation axis intersecting the direction of gravity; a stator having a second magnetic force portion; a support portion that supports the rotor located at a first position; a control unit; the first magnetic force portion is arranged circumferentially along the rotation direction on the outer peripheral side surface of the rotor, the second magnetic force portion is disposed above the rotor in an arc shape along the rotation direction, When the rotor is located at the first position and a levitation force on the rotor is less than a predetermined value, the control unit rotates the rotor to a second position where the levitation force is equal to or greater than a predetermined value, and levitates the rotor from the second position. A rotary drive device characterized by:

2. When the rotor is located at the first position, the control unit levitates the rotor from the first position when the levitation force is equal to or greater than the predetermined value.

2. The rotary drive device according to claim 1.

3. the second magnetic force portion includes a plurality of coils, The plurality of coils are arranged symmetrically with respect to the axis along the direction of gravity in a plan view seen in a direction along the rotation axis.

3. The rotary drive device according to claim 1 or 2.

4. the first magnetic force portion includes a plurality of permanent magnets, At the second position, the plurality of permanent magnets are arranged symmetrically with respect to the axis along the direction of gravity in a plan view seen in a direction along the rotation axis.

3. The rotary drive device according to claim 1 or 2.

5. In the second position, the orientation of the magnetic pole of one of the plurality of permanent magnets is parallel to the direction of gravity.

5. The rotary drive device according to claim 4.

6. the plurality of permanent magnets include a first magnet group in which magnetic poles are alternately arranged in the rotation direction, and a second magnet group in which magnetic poles are alternately arranged in a direction intersecting the rotation direction, At the second position, the second magnet group is arranged symmetrically with respect to an axis along the direction of gravity.

5. The rotary drive device according to claim 4.

7. The levitation force varies depending on the electrical angle of the rotor.

3. The rotary drive device according to claim 1 or 2.

8. The control unit rotates the rotor to a position where a levitation force on the rotor becomes equal to or greater than a predetermined value when the rotor is supported by the support unit, and then stops the rotor by supporting it with the support unit.

3. The rotary drive device according to claim 1 or 2.

9. a rotor having a first magnetic portion and rotatable in a rotation direction about a rotation axis intersecting the direction of gravity; a stator having a second magnetic force portion; a support portion that supports the rotor located at a first position; a control unit; the first magnetic force portion is arranged circumferentially along the rotation direction on the outer peripheral side surface of the rotor, the second magnetic force portion is disposed above the rotor in an arc shape along the rotation direction, When the rotor is located at the first position and a cogging torque on the rotor is equal to or greater than a predetermined value, the control unit rotates the rotor to a second position where the cogging torque becomes less than the predetermined value, and levitates the rotor from the second position. A rotary drive device characterized by:

10. When the rotor is located at the first position and the cogging torque is less than the predetermined value, the control unit levitates the rotor from the first position. The rotary drive device according to claim 9 .

11. the second magnetic force portion includes a plurality of coils, The plurality of coils are arranged asymmetrically with respect to the axis along the direction of gravity in a plan view seen in a direction along the rotation axis.

11. The rotary drive device according to claim 9 or 10.

12. In the plurality of coils, a gap is formed between adjacent coils, the first magnetic force portion includes a plurality of permanent magnets, At the second position, the plurality of permanent magnets are arranged so that one permanent magnet does not face both the coil adjacent to the gap and the gap. The rotary drive device according to claim 11 .

13. the first magnetic force portion includes a plurality of permanent magnets, At the second position, the torques in the rotation direction generated between the plurality of permanent magnets and the plurality of coils are canceled out. The rotary drive device according to claim 11 .

14. The cogging torque varies depending on the electrical angle of the rotor.

11. The rotary drive device according to claim 9 or 10.

15. The control unit rotates the rotor to a position where a cogging torque on the rotor becomes less than a predetermined value when the rotor is supported by the support unit, and then stops the rotor by supporting it on the support unit.

11. The rotary drive device according to claim 9 or 10.

16. A method for controlling a rotary drive device comprising: a rotor having a first magnetic force portion and rotatable in a rotation direction about a rotation axis that intersects with a direction of gravity; a stator having a second magnetic force portion; and a support portion that supports the rotor located at a first position, wherein the first magnetic force portion is disposed circumferentially along the rotation direction on an outer peripheral side surface of the rotor, and the second magnetic force portion is disposed in an arc shape above the rotor that is also along the rotation direction, When the rotor is located at the first position and the levitation force on the rotor is less than a predetermined value, the rotor is rotated to a second position where the levitation force is equal to or greater than the predetermined value, and the rotor is levitated from the second position. A method for controlling a rotary drive device.

17. A method for controlling a rotary drive device comprising: a rotor having a first magnetic force portion and rotatable in a rotation direction about a rotation axis that intersects with a direction of gravity; a stator having a second magnetic force portion; and a support portion that supports the rotor located at a first position, wherein the first magnetic force portion is disposed circumferentially along the rotation direction on an outer peripheral side surface of the rotor, and the second magnetic force portion is disposed in an arc shape above the rotor that is also along the rotation direction, When the rotor is located at the first position and a cogging torque applied to the rotor is equal to or greater than a predetermined value, the rotor is rotated to a second position where the cogging torque becomes less than the predetermined value, and the rotor is levitated from the second position. A method for controlling a rotary drive device.

18. A rotary drive device according to any one of claims 1, 2, 9 and 10; Components installed on the rotor; A rotating device comprising:

19. The components include: an irradiation unit that irradiates radiation toward a subject disposed inside the rotor; a detection unit that is disposed opposite the irradiation unit across the rotation axis and detects the radiation that has passed through the subject; 20. The rotating device according to claim 18, further comprising:

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