Control system for controlling magnetic levitation system

Abstract

A control system for controlling a magnetic levitation system, comprising controllers (101, 102), each controller being configured to control one or more magnetic actuators (108-111) that cause an object (113) to be magnetically suspended. One of the controllers is configured to operate as a master controller, and one or more of the other controllers are configured to operate as one or more slave controllers. The master controller is communicatively connected to the one or more slave controllers via one or more digital data transmission links (104), and the master controller is configured to control the operation of the one or more slave controllers. The control system is capable of implementing centralized control using separate controllers, and thereby does not require a controller with a large number of controller current sources.

Description

Technical Field

[0001] The present disclosure relates to a control system for controlling a magnetic levitation system, which may be, for example but not necessarily, an active magnetic bearing "AMB" system. In addition, the present disclosure relates to a magnetic levitation system. Background Art

[0002] Magnetic levitation systems, such as for example active magnetic bearing "AMB" systems, are often used to levitate objects that are, for example, rotating or oscillating. A typical application is the levitation of the rotor of an electric motor, for example a high-speed motor. In many cases, levitation is achieved by balancing the attractive force of oppositely acting magnets and other forces acting on the object to be levitated, wherein at least one of the magnets is a controllable electromagnet. In principle, it is also possible to balance the attractive force of a controllable electromagnet with other forces, such as gravity, that act in opposition to the attractive force of the electromagnet. There are several different types of magnetic levitation systems. Some systems use permanent magnetic material to generate the bias flux, while other systems use a DC bias current to generate the bias flux. The bias is used to linearize the operation of the system and to improve the control dynamics of the system.

[0003] Due to the inherent instability of magnetic levitation, it is necessary to actively control the magnetic forces acting in the degrees of freedom of a suspended object (e.g. the rotor of an electric motor). This instability is caused by the fact that when the air gap between a magnet and an object made of, for example, ferromagnetic material becomes smaller, the magnetic attraction between the magnet and the object increases. In a typical active magnetic bearing system, there are five degrees of freedom to be controlled, so ten controller current sources are required. All of them should be operated in a centralized manner to provide good controllability of the AMB system and take into account the correlation between the different degrees of freedom.

[0004] There are AMB systems with longer shafts where additional bearings are required to provide reliable suspension. Four controller current sources are required for each radial bearing, thus quickly increasing the total number of controller current sources. Therefore, in AMB systems of the type mentioned above, the control system requires a large number of controller current sources to provide magnetic suspension. The challenges associated with a large number of controller current sources have been addressed by modifying the power electronics to provide more controller current sources, but this requires additional development and reduces cost effectiveness. Alternatively, decentralized schemes have been adopted when different bearings operate independently, in which case the controllability and stability of the magnetic suspension may be reduced. Summary of the invention

[0005] In order to provide a basic understanding of some aspects of various invention embodiments, a simplified summary of the invention is provided below. This summary of the invention is not an extensive overview of the present invention. It is neither intended to identify key or important elements of the present invention nor to indicate the scope of the present invention. The following summary of the invention merely presents some concepts of the present invention in a simplified form as a preface to a more detailed description of exemplary embodiments of the present invention.

[0006] In this document, when used as a prefix, the word "geometry" means a geometric concept that is not necessarily part of any physical object. The geometric concept can be, for example, a geometric point, a straight or curved geometric line, a geometric plane, a non-planar geometric surface, a geometric space, or any other zero-dimensional, one-dimensional, two-dimensional, or three-dimensional geometric entity.

[0007] According to the present invention, there is provided a new control system for controlling a magnetic levitation system, which may be, for example but not necessarily, an active magnetic bearing "AMB" system for levitating a rotating element, such as a motor rotor.

[0008] The control system according to the present invention includes a controller, each of which is configured to control one or more magnetic actuators of a magnetic levitation system to cause an object to levitate magnetically. One of these controllers is configured to operate as a master controller, and one or more of these controllers are configured to operate as one or more slave controllers. The master controller is communicatively connected to the one or more slave controllers via one or more digital data transmission links, wherein the digital data transmitted via the one or more digital data transmission links indicates a reference value of the current of the coil of the magnetic actuator, and the master controller is configured to control the operation of the one or more slave controllers.

[0009] The control system according to the present invention can implement centralized control using a single controller, and thus does not require a controller having a large number of controller current sources.

[0010] According to the present invention, a new magnetic levitation system is also provided, comprising:

[0011] - a magnetic actuator configured to levitate an object magnetically,

[0012] - a position sensor system for generating a position signal indicative of a position of the object relative to a reference position of the object, and

[0013] - A control system according to the invention for controlling the current of a coil of a magnetic actuator based on a position signal.

[0014] Exemplary and non-limiting embodiments are described in the attached dependent claims.

[0015] Various exemplary and non-limiting embodiments, both as to constructions and methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplary and non-limiting embodiments when read in connection with the accompanying drawings.

[0016] The verbs "to comprise" and "to include" are used herein as open limitations that neither exclude nor require the existence of unrecited features.

[0017] Unless explicitly stated otherwise, the features recited in the dependent claims may be freely combined with each other.

[0018] Furthermore, it is to be understood that the use of "a" or "an" throughout this document, i.e. in the singular, does not exclude a plurality. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Exemplary and non-limiting embodiments and their advantages will be explained in more detail below by way of example with reference to the accompanying drawings, in which:

[0020] Figure 1a and Figure 1b shows a magnetic levitation system including a control system according to an exemplary and non-limiting embodiment,

[0021] Figure 2 A portion of a magnetic levitation system including a control system according to an exemplary and non-limiting embodiment is shown, and

[0022] Figure 3a , Figure 3b , Figure 3c and Figure 3d An exemplary winding arrangement of a magnetic actuator that can be controlled by a control system according to an exemplary and non-limiting embodiment is shown. DETAILED DESCRIPTION

[0023] The specific examples provided in the following description should not be construed as limiting the scope and / or applicability of the appended claims.The lists of examples and groups of examples provided in the specification are not exhaustive unless expressly stated otherwise.

[0024] Figure 1a A magnetic levitation system is shown, which includes a control system 100 according to an exemplary and non-limiting embodiment. The magnetic levitation system includes magnetic actuators 108, 109, 110, 111 and 112 configured to magnetically levitate an object 113. In this exemplary case, the magnetic levitation system is an active magnetic bearing "AMB" system, and the object 113 is a rotating element, which can be, for example, a rotor of an electric motor. The magnetic actuators 108, 109, 111 and 112 are radial magnetic bearings, and the magnetic actuator 110 is an axial magnetic bearing.

[0025] The magnetic levitation system comprises a position sensor system 114 for generating a position signal indicating the position of the object 113 relative to a reference position of the object. The position sensor system 114 may comprise, for example, an inductive sensor, wherein the inductance of each inductive sensor depends on the distance from the inductive sensor under consideration to the surface of the object 113. It is also possible that the position sensor system comprises means for forming a position signal based on the difference between the inductances of the coils of the magnetic actuators 108-112. When the voltage directed to the coil under consideration varies in a stepwise manner, the inductance of each coil may be estimated based on, for example, the rate of change di / dt of the current. In this exemplary case, no separate position sensor is required.

[0026] The control system 100 is configured to control the current of the coils of the magnetic actuators 108-112 based on the position signal mentioned above. The control system 100 includes a controller 101 and a controller 102, each of which is configured to control a corresponding magnetic actuator in the magnetic actuators for magnetically levitating the object 113. One of the controllers 101 and 102 is configured to operate as a master controller, and the other of the controllers 101 and 102 is configured to operate as a slave controller. The master controller is communicatively connected to the slave controller via a digital data transmission link 104, and the master controller is configured to control the operation of the slave controller. Therefore, centralized control can be implemented using separate controllers 101 and 102, and thus a controller with a large number of controller current sources is not required. In an exemplary embodiment, the digital data transmitted between the controller 101 and the controller 102 indicates a reference value of the current of the coil of the magnetic actuator, and the controller 101 and the controller 102 are configured to use the digital data to coordinate the operations of the controller 101 and the controller 102, so that, for example, a situation in which two or more of the magnetic actuators act against each other can be avoided. In another exemplary embodiment, all calculations related to magnetic levitation are performed by the master controller, and one or more slave controllers are used only as controllable current sources, which are controlled by the reference value received from the master controller via the digital data transmission link.

[0027] In a controller system according to an exemplary and non-limiting embodiment, each of the controllers includes a control board configured to perform calculations related to magnetic levitation. In addition, each of the controllers includes a replaceable power board, each of the power boards being configured to supply current according to a control signal received from the control board. Figure 1bIn the embodiment, the control board is indicated by reference numeral 105 and the replaceable power board is indicated by reference numeral 106. The above arrangement can adapt each controller to different requirements by changing the number and rated current of the replaceable power boards.

[0028] Figure 1b The control board 105 shown may include one or more processor circuits, each of which may be a programmable processor circuit equipped with appropriate software, a dedicated hardware processor, such as, for example, an application specific integrated circuit "ASIC", or a configurable hardware processor, such as a field programmable gate array "FPGA". In addition, the control board 105 may include one or more storage devices, such as, for example, a random access memory "RAM" device. Each of the replaceable power boards 106 may include, for example, transistors configured to form, for example, a full H-bridge or a half H-bridge and a driver circuit for driving the transistors.

[0029] Figure 2 A portion of a magnetic levitation system including a control system 200 according to an exemplary and non-limiting embodiment is shown. The control system includes controllers 201, 202, and 203 for controlling a magnetic actuator (e.g., an active magnetic bearing) of the magnetic levitation system. In this exemplary case, controller 202 and controller 203 are connected to the same coil 207 of the magnetic actuator. This arrangement provides redundancy, thereby improving reliability. One of the controllers 201, 202, and 203 acts as a master controller, which is configured to select which of the controllers 202 and 203 is used to supply current to the coil 207. In an exemplary embodiment, the master controller is configured to compare one or more quantities with an allowable range of the one or more quantities, and select one of the controllers 202 and 203 based at least in part on the comparison, wherein the one or more quantities are related to the operation of each of the controllers 202 and 203. The one or more quantities related to the operation of each controller may include, for example, a measured current, a reference value of the current, a direct current "DC" voltage of the controller, a position estimate of the suspended object, and / or a temperature measured in the controller. In an exemplary embodiment, three or more controllers are connected to the same coil, and the controllers are configured to generate reference values ​​for the coil current, and a main controller is configured to select one of the controllers based on a majority of the reference values ​​so that the reference value generated by the selected controller belongs to the majority of the reference values.

[0030] Figure 3a , Figure 3b , Figure 3c and Figure 3dAn exemplary winding arrangement of a magnetic actuator that can be controlled with a control system according to an exemplary and non-limiting embodiment is shown. Figure 3a An exemplary winding arrangement is shown in which each electromagnetic pole pair is powered by one controller current source. Figure 3b An exemplary winding arrangement is shown, in which each electromagnetic pole pair is provided with two windings, which are supplied by different controller current sources. The controller current sources advantageously belong to different controllers, for example to improve redundancy. Figure 3b Two exemplary windings 331 and 332 are shown, which are arranged to magnetize the same electromagnetic pole pair. The winding 331 depicted with a solid line may be powered by a first controller, and the winding 332 depicted with a dashed line may be powered by a second controller. Figure 3c An exemplary arrangement is shown in which more than one set of electromagnets are used to move the electromagnets in a desired degree of freedom (i.e., in Figure 3c Control is implemented in directions perpendicular to each other in the graphic plane). Figure 3c Two exemplary windings 333 and 334 are shown, which are arranged to magnetize different electromagnets belonging to the groups mentioned above. The winding 333 depicted with a solid line can be powered by a first controller current source, and the winding 334 depicted with a dotted line can be powered by a second controller current source. The first controller current source and the second controller current source advantageously belong to different controllers, for example to improve redundancy. The possibility of supplying current to parallel windings of a given electromagnetic pole pair or to windings of different electromagnets from different controller current sources advantageously belonging to different controllers to control the same degree of freedom allows to increase the bandwidth of the control, because when the number of controller current sources increases, the inductance of the windings that limit the bandwidth decreases. This allows to operate systems of various sizes by increasing the number of controllers without changing the power electronics. Figure 3d An exemplary winding arrangement is shown, where each electromagnetic pole has a separate winding that can be powered by a separate controller current source. Figure 3d Two exemplary windings 335 and 336 are shown, arranged to magnetize the poles of an electromagnet and powered by different controller current sources.

[0031] The specific examples provided in the description given above should not be construed as limiting the scope and / or applicability of the appended claims.The lists of examples and groups of examples provided in the description given above are not exhaustive unless expressly stated otherwise.

Claims

1. A control system for controlling a magnetic levitation system, the control system comprising: a controller (101, 102, 201-203), each controller (101, 102, 201-203) being configured to control one or more magnetic actuators of the magnetic levitation system for magnetically levitating an object, wherein one of the controllers is configured to operate as a master controller (101, 201), and the other one or more controllers of the controllers are configured to operate as one or more slave controllers (102, 202, 203), and the master controller is communicatively connected to the one or more slave controllers via one or more digital data transmission links (104), wherein digital data transmitted via the one or more digital data transmission links indicates a reference value of the current of the coil of the magnetic actuator, and the master controller is configured to control the operation of the one or more slave controllers; Characterized in that two or more of the controllers are connectable to the same coil (207) of the magnetic actuator, and the main controller is configured to select one of the two or more controllers to supply current to the same coil.

2. The control system according to claim 1, wherein: Each of the controllers includes a control board (105) and a replaceable power board (106), wherein the control board (105) is configured to perform calculations related to magnetic levitation, and each replaceable power board (106) is configured to supply current according to a control signal received from the control board.

3. The control system according to claim 1, wherein: The master controller is configured to compare one or more quantities with an allowable range for each of the one or more quantities, wherein the one or more quantities are related to the operation of each of the controllers connected to the same coil, and the master controller selects one of the controllers based at least in part on the comparison related to the controllers.

4. The control system according to claim 1, wherein: The controllers connected to the same coil are configured to generate reference values ​​for the current of the coil, and the main controller is configured to select one of the controllers based on a majority of the reference values, so that the reference value generated by the selected controller belongs to the majority of the reference values.

5. A magnetic levitation system, comprising: - a magnetic actuator (108-112) configured to magnetically levitate the object (113), - a position sensor system (114) for generating a position signal indicative of a position of the object relative to a reference position of the object, and - a control system (100, 200) for controlling the current of the coil of the magnetic actuator based on the position signal, Characterized in that the control system is the control system according to claim 1.

6. The magnetic levitation system according to claim 5, wherein: The magnetic actuator (108, 109, 111, 112) comprises a radial magnetic bearing.

7. The magnetic levitation system according to claim 5, wherein: The magnetic actuator (110) includes an axial magnetic bearing.

8. The magnetic levitation system according to claim 6, wherein: The magnetic actuator (110) includes an axial magnetic bearing.

9. The magnetic levitation system according to any one of claims 5 to 8, wherein: Two or more of the controllers (201, 202) in the control system (200) are connected to the same coil (207) of the magnetic actuator, and the main controller is configured to select one of the two or more controllers to supply current to the same coil.

10. The magnetic levitation system according to any one of claims 5 to 8, wherein: The magnetic actuator has two or more windings (331, 332), the windings (331, 332) are configured to magnetize the same electromagnetic pole pair, and a first controller in the controller of the control system is configured to supply current to the first winding in the windings, and a second controller in the controller of the control system is configured to supply current to the second winding in the windings.

11. The magnetic levitation system according to any one of claims 5 to 8, wherein: The magnetic actuator has a first set of electromagnets for implementing control in a predetermined degree of freedom and a second set of electromagnets for implementing control in the same predetermined degree of freedom, and a first controller in the controller of the control system is configured to supply current to the windings (333) of the first set of electromagnets, and a second controller in the controller of the control system is configured to supply current to the windings (334) of the second set of electromagnets.

12. The magnetic levitation system according to any one of claims 5 to 8, wherein: The magnetic actuator has windings (335, 336), each winding being wound around only a single pole of the magnetic actuator, the windings being powered by a separate controller current source of the control system.

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