Control devices, refrigeration equipment

Abstract

This invention provides a technology that can suppress vibrations of the rotating shaft supported by a magnetic bearing. [Solution] A controller 700 according to one embodiment of the present disclosure includes a coil 412 that generates an electromagnetic force that attracts or repels a rotating shaft 250, and controls the output voltage from the power conversion circuit 460 to the coil 412 by operating a power conversion circuit 460 that outputs power to the coil 412 for a radial magnetic bearing 400 that supports the rotating shaft 250 in a non-contact manner. Specifically, the controller 700 includes an integral element in the transfer function from the current detection value of the coil 412 to the voltage command value Vc1, the amplitude of the open-loop transfer function including the current detection value of the coil 412 has attenuation characteristics in the frequency band above the critical speed of the rotating body RT including the rotating shaft 250, and the phase of the open-loop transfer function including the position detection value of the rotating shaft 250 is in the range of -90 degrees or more and 90 degrees or less at the critical speed of the rotating body RT.

Description

[Technical Field]

[0001] This disclosure relates to control devices for radial magnetic bearings and bearingless motors, etc. [Background technology]

[0002] Conventionally, for magnetic bearings and bearingless motors, a technique is known in which a target current value for an electromagnet is set based on the deviation between the target position and the actual position, and the voltage applied to the electromagnet is controlled based on the deviation between the set target current value and the actual current value (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Patent No. 6695541 [Overview of the project] [Problems that the invention aims to solve]

[0004] Incidentally, a rotating body that rotates as a whole, including the rotating shaft of a supported object such as a magnetic bearing (for example, a rotating shaft and an impeller fixed integrally to the rotating shaft), is subjected to a centrifugal force with the same frequency as the rotation frequency. Therefore, for example, if the rotational speed of the rotating shaft is increased to pass through the rotational frequency corresponding to the natural frequency of the rotating body, the vibration of the rotating body due to centrifugal force increases rapidly. In this case, the position control and current control based on the target position and current target values ​​mentioned above have relatively low response speeds, and may not be able to adequately suppress the natural vibration of the rotating body including the rotating shaft. As a result, it may not be possible to increase the rotational speed of the rotating shaft to a rotational frequency range higher than the rotational frequency corresponding to the natural frequency.

[0005] This disclosure aims to provide a technology capable of suppressing vibrations of the rotating shaft of a supported object such as a magnetic bearing. [Means for solving the problem]

[0006] In the first aspect of this disclosure, A control device for a magnetic bearing or bearingless motor that includes a coil that generates an electromagnetic force to attract or repel a rotating shaft and supports the rotating shaft in a non-contact manner, wherein the control device controls the output voltage from the power conversion circuit to the coil by operating a power conversion circuit that outputs power to the coil, The transfer function from the current value of the coil to the output voltage includes an integral element. The amplitude of the open-loop transfer function, including the current value of the coil, has attenuation characteristics in the frequency band above the critical speed of the rotating body, including the rotating shaft. The phase of the open-loop transfer function, including the position of the rotation axis, is in the range of -90 degrees or more and 90 degrees or less at the critical speed. A control device is provided.

[0007] According to this embodiment, the control device can suppress vibrations of the rotating shaft of the object supported by magnetic bearings or bearingless motors.

[0008] Furthermore, a second aspect of this disclosure, based on the first aspect described above, The phase of the open-loop transfer function, including the position of the rotation axis, may be in the range of -90 degrees or more and 90 degrees or less, within the range between two resonant frequencies separated above and below the critical speed as the rotation axis rotates.

[0009] According to this embodiment, the control device can appropriately suppress vibrations of the rotating shaft of the object supported by magnetic bearings or bearingless motors in accordance with the rotation of the rotating shaft.

[0010] Furthermore, a third aspect of this disclosure, based on the first or second aspect described above, Based on the position information of the rotating shaft and the target position of the rotating shaft, the target value of the coil current is obtained. Based on the current value of the coil and the target value, a first voltage command value for the coil is obtained. Based on the position information of the rotating shaft and the information regarding the electromagnetic force of the coil, a second voltage command value is obtained. The output voltage may be controlled based on the first voltage command value and the second voltage command value.

[0011] According to this embodiment, the control device can control the position of the rotating shaft based on a first voltage command value, and can also suppress vibrations of the rotating body, including the rotating shaft, at a response speed higher than that of the first voltage command value based on a second voltage command value.

[0012] Furthermore, in the fourth aspect of this disclosure, based on the third aspect described above, Based on the information regarding the electromagnetic force of the coil and the position information of the rotating shaft, a state observer may be used to acquire the natural vibration state of the rotating shaft, and the second voltage command value may be output based on the acquired state.

[0013] According to this embodiment, the control device can appropriately suppress vibrations of the rotating shaft due to centrifugal force at a frequency corresponding to the natural frequency of the rotating body, based on a second voltage command value.

[0014] Furthermore, in the fifth aspect of this disclosure, based on the third or fourth aspect described above, Based on the first voltage command value and the second voltage command value, a third voltage command value for controlling the output voltage is output. Based on the third voltage command value and the current value of the coil, a disturbance observer is used to obtain the deviation of the output voltage corresponding to the steady-state deviation between the current value of the coil and the target value. The first voltage command value may be obtained based on the deviation between the current value of the coil and the target value, and the obtained deviation of the output voltage.

[0015] According to this embodiment, the control device can reduce the gain of the integral element (i.e., integral controller) in the control element for acquiring the first voltage command value. As a result, the control device can weaken the responsiveness of the first voltage command value to the second voltage command value's vibration suppression control of the rotating shaft. Consequently, the control device can prevent a situation in which the first voltage command value's position control of the rotating shaft weakens the effect of the second voltage command value's vibration suppression control of the rotating shaft.

[0016] Furthermore, the sixth aspect of this disclosure is based on any one of the third to fifth aspects described above, The information relating to the electromagnetic force of the coil may also be the current value of the coil.

[0017] According to this embodiment, the control device can acquire a second voltage command value based on the current value of the coil.

[0018] Furthermore, in the seventh aspect of this disclosure, A control device for a magnetic bearing or bearingless motor that includes a coil that generates an electromagnetic force to attract or repel a rotating shaft and supports the rotating shaft in a non-contact manner, wherein the control device controls the output voltage from the power conversion circuit to the coil by operating a power conversion circuit that outputs power to the coil, The amplitude of the open-loop transfer function, including the current value of the coil, has attenuation characteristics in the frequency band above the critical speed of the rotating body, including the rotating shaft. The phase of the open-loop transfer function, including the position of the rotation axis, is in the range of -90 degrees or more and 90 degrees or less at the critical speed. Based on the position information of the rotating shaft and the target position of the rotating shaft, the target value of the coil current is obtained. Based on the current value of the coil and the target value, a first voltage command value for the coil is obtained. Based on the position information of the rotating shaft and the information regarding the electromagnetic force of the coil, a second voltage command value is obtained. Based on the first voltage command value and the second voltage command value, a third voltage command value for controlling the output voltage is output. Based on the third voltage command value and the current value of the coil, a disturbance observer is used to obtain the deviation of the output voltage corresponding to the steady-state deviation between the current value of the coil and the target value. Based on the deviation between the current value of the coil and the target value, and the obtained deviation of the output voltage, the first voltage command value is obtained. A control device is provided.

[0019] According to this embodiment, the control device can appropriately suppress vibrations of the rotating shaft of an object supported by magnetic bearings or a bearingless motor in accordance with the rotation of the rotating shaft. Specifically, the control device can control the position of the rotating shaft based on a first voltage command value, and suppress vibrations of the rotating body, including the rotating shaft, at a higher response speed than the first voltage command value based on a second voltage command value. Furthermore, the control device can omit an integral element (i.e., an integral controller) from the control elements for acquiring the first voltage command value. As a result, the control device can weaken the responsiveness of the first voltage command value to the second voltage command value's vibration suppression control of the rotating shaft. Consequently, the control device can prevent situations in which the vibration suppression control of the rotating shaft based on the second voltage command value is weakened by the rotation shaft position control based on the first voltage command value.

[0020] Furthermore, in the eighth aspect of this disclosure, A compressor comprising the aforementioned rotating shaft, the aforementioned magnetic bearing or the aforementioned bearingless motor, and a rotating part that rotates integrally with the rotating shaft and compresses the refrigerant, A control device comprising any one of the first to seventh embodiments described above, A refrigeration system will be provided.

[0021] According to this embodiment, the refrigeration system can suppress vibrations of the rotating shaft of the object supported by magnetic bearings or bearingless motors.

[0022] Furthermore, the ninth aspect of this disclosure is based on the eighth aspect described above, The compressor is a turbo compressor, The rotating shaft may rotate at a rotational speed of 1.67 times or more the primary critical speed.

[0023] According to this embodiment, the refrigeration device as a turbo chiller can suppress vibration of the rotating shaft when it rotates at a rotational speed of 1.67 times or more the primary critical speed. [Effects of the Invention]

[0024] According to the above-described embodiment, vibrations of the rotating shaft of a supported object such as a magnetic bearing can be suppressed. [Brief explanation of the drawing]

[0025] [Figure 1] This is a diagram showing the configuration of an example of a refrigeration system. [Figure 2] This diagram shows an example of the configuration of a compressor. [Figure 3] This figure shows an example of a radial magnetic bearing. [Figure 4] This figure shows another example of a radial magnetic bearing. [Figure 5] This figure shows a first example of a control method for a rotating shaft and magnetic bearing system. [Figure 6] This block diagram shows an example of state feedback control for a rotating shaft and magnetic bearing system. [Figure 7] This figure shows an example of the frequency characteristics of a real machine and a model of a rotating body, including the axis of rotation. [Figure 8] This diagram illustrates an example of the relationship between the rotational speed of a rotating shaft and the magnitude of vibration. [Figure 9] This figure shows a second example of a control method for a rotating shaft and magnetic bearing system. [Figure 10] This figure shows a third example of a control method for a rotating shaft and magnetic bearing system. [Figure 11] This figure shows a fourth example of a control method for a rotating shaft and magnetic bearing system. [Figure 12]This figure shows the fifth example of a control method for a rotating shaft and magnetic bearing system. [Figure 13] This figure shows the sixth example of a control method for a rotating shaft and magnetic bearing system. [Figure 14] This is a Bode plot illustrating an example of the frequency characteristics of a rotating body including its axis of rotation. [Figure 15] This Bode plot shows an example of the open-loop transfer characteristics (transfer function) of a current controller from the detected current value to the voltage command value. [Figure 16] This is a Bode plot illustrating an example of the open-loop transfer characteristics (transfer function) from the position detection value to the voltage command value. [Figure 17] This is a Bode plot illustrating another example of the frequency characteristics of a rotating body that includes an axis of rotation. [Figure 18] This Bode plot illustrates another example of the open-loop transfer characteristics (transfer function) from the position detection value to the voltage command value. [Figure 19] This is a Bode plot illustrating yet another example of the frequency characteristics of a rotating body that includes its axis of rotation. [Figure 20] This Bode plot illustrates yet another example of the open-loop transfer characteristics (transfer function) from the position detection value to the voltage command value. [Figure 21] This figure shows another example of a control method for a rotating shaft and magnetic bearing system. [Figure 22] This figure shows an example of a bearingless motor. [Modes for carrying out the invention]

[0026] The embodiments will be described below with reference to the drawings.

[0027] [Refrigeration System Configuration] Referring to Figure 1, the configuration of the refrigeration system 1 according to this embodiment will be described.

[0028] Figure 1 shows an example of the configuration of a refrigeration system 1.

[0029] The refrigeration device 1 circulates a refrigerant through the refrigerant circuit RC and uses a compression refrigeration cycle to cool or heat the target liquid or gas.

[0030] Refrigeration device 1 is, for example, a chiller that cools a target liquid (cooled liquid) by heat exchange between a refrigerant and the target liquid using a compression refrigeration cycle. The cooled liquid is, for example, water or brine. Alternatively, refrigeration device 1 may be a water heater that generates hot water by heat exchange between a refrigerant and water using a compression refrigeration cycle. Alternatively, refrigeration device 1 may be an air conditioner that cools or heats a target space by heat exchange between a refrigerant and air. The following explanation will focus mainly on the case where refrigeration device 1 is a chiller.

[0031] As shown in Figure 1, the refrigeration system 1 includes refrigerant paths L1 to L4, a compressor 10, a heat exchanger 20, an expansion mechanism 30, and a heat exchanger 40 as components of the refrigerant circuit RC.

[0032] Refrigerant pathways L1 to L4 are the paths through which the refrigerant flows. Refrigerant pathways L1 to L4 are, for example, metal pipes made of steel or similar material.

[0033] Refrigerant path L1 connects the heat exchanger 40 to the suction port of the compressor 10. Refrigerant path L2 connects the discharge port of the compressor 10 to the heat exchanger 20. Refrigerant path L3 connects the heat exchanger 20 to the expansion mechanism 30. Refrigerant path L4 connects the expansion mechanism 30 to the heat exchanger 40.

[0034] The compressor 10 compresses the low-pressure refrigerant flowing in from the refrigerant path L1 and discharges the high-pressure refrigerant into the refrigerant path L2.

[0035] The heat exchanger 20 performs heat exchange between a refrigerant flowing through its interior and an external heat transfer medium (for example, cooling water).

[0036] The heat exchanger 20 is a so-called condenser, which cools the high-temperature and high-pressure refrigerant, compressed by the compressor 10 and flowing in from the refrigerant path L2, by heat exchange with an external heat transfer medium, thereby condensing it and releasing the high-pressure liquid refrigerant into the refrigerant path L3.

[0037] The expansion mechanism 30 expands the high-pressure liquid refrigerant, causing the low-pressure gas-liquid mixture of refrigerant to flow out. The expansion mechanism 30 is, for example, an expansion valve or an orifice.

[0038] The expansion mechanism 30 expands the high-pressure liquid refrigerant that flows in from the refrigerant path L3 and has passed through the heat exchanger 20, causing the low-pressure gas-liquid mixture of refrigerant to flow out into the refrigerant path L4.

[0039] The heat exchanger 40 performs heat exchange between the refrigerant flowing through its interior and the external liquid to be cooled.

[0040] The heat exchanger 40 is a so-called evaporator, and by absorbing heat from the liquid to be cooled, it heats the low-pressure gas-liquid mixture of refrigerant that flows in from the refrigerant path L4 and has been expanded by the expansion mechanism 30, thereby evaporating it and causing the low-pressure gaseous refrigerant to flow out into the refrigerant path L1. In this way, the refrigeration device 1 can cool the liquid to be cooled.

[0041] [Compressor configuration] The configuration of the compressor 10 according to this embodiment will be described with reference to Figures 2 to 4.

[0042] Figure 2 shows an example configuration of the compressor 10. Figure 3 shows an example of the radial magnetic bearing 400. Figure 4 shows another example of the radial magnetic bearing 400.

[0043] In Figure 2, a cross-sectional view is shown in a plane including the axis AX of the rotating shaft 250, so that the contents inside the casing 100 are exposed. In Figures 3 and 4, some of the electromagnets 410 among the multiple (specifically, three or more) electromagnets 410 included in the radial magnetic bearing 400 are depicted as representative.

[0044] Hereafter, the direction along the axis AX of the rotating shaft 250, i.e., the parallel direction, will be referred to as the "axial direction," and explanations may be given using the terms for the axial direction, as well as the "radial direction" and "circumferential direction" with respect to the axis AX.

[0045] As shown in Figure 2, in this example, the compressor 10 is a centrifugal compressor.

[0046] The number of stages in the compressor 10 is, for example, one stage (single stage), as shown in Figure 2. Alternatively, the number of stages in the compressor 10 may be two or more stages, and a multi-stage compressor 10 has multiple stages of compression units, including impellers 200, arranged in series.

[0047] The compressor 10 includes a casing 100, an impeller 200, a rotating shaft 250, an electric motor 300, a radial magnetic bearing 400, a power supply 450, a power conversion circuit 460, a thrust magnetic bearing 500, a touchdown bearing 600, and a controller 700.

[0048] The casing 100 is an enclosure for housing and mounting the components of the compressor 10.

[0049] The impeller 200 is housed in an impeller chamber 110 formed inside the casing 100.

[0050] The impeller 200 is mounted on the rotating shaft 250 and rotates about the axis AX of the rotating shaft 250. The impeller 200 is formed such that its meridional outer diameter increases from one end in the axial direction (the right end in this example) to the other end (the left end in this example). At the circumferential center of one end in the axial direction of the impeller 200, the refrigerant flowing in axially from the suction pipe 120 is discharged radially outward at the other end in the axial direction of the impeller 200. A diffuser 111 is provided on the radially outward side of the other radial end of the impeller 200, where the dynamic pressure (i.e., kinetic energy) of the refrigerant flowing out from the impeller 200 is converted into static pressure (i.e., pressure energy), and the compressed refrigerant flows out from the diffuser 111 to the discharge pipe 130.

[0051] The electric motor 300 is housed in an electric motor room 140 formed inside the casing 100.

[0052] The electric motor 300 rotates the impeller 200 using power supplied from an external source. The electric motor 300 is, for example, a permanent magnet synchronous motor. The electric motor 300 is of the inner rotor type and includes a rotor 310 attached to the rotating shaft 250 and a stator 320 positioned radially outside the rotor 310 and fixed to the inner circumferential surface of the motor chamber 140 in the casing 100.

[0053] The radial magnetic bearings 400 support the radial load on the rotating shaft 250 non-contact by electromagnetic force. Two radial magnetic bearings 400 are provided, each fixed to the inner surface of the casing 100. The two radial magnetic bearings 400 are positioned adjacent to each other at both ends of the electric motor 300 in the axial direction.

[0054] As shown in Figures 3 and 4, the radial magnetic bearing 400 includes a plurality of electromagnets 410 positioned facing the rotating shaft 250 from the radially outer side of the rotating shaft 250 and arranged to surround the rotating shaft 250 around its axis. For example, the plurality of electromagnets 410 can adjust the position of the rotating shaft 250 with two degrees of freedom as viewed from a direction along the rotating shaft 250 by including two or more combinations of pairs of electromagnets 410 located radially opposite each other with respect to the rotating shaft 250. The electromagnets 410 include a stator core 411 and coils 412 wound around the stator core.

[0055] For example, as shown in Figure 3, the radial magnetic bearing 400 is of the heteropolar type. In the heteropolar type, the magnetic poles of the multiple electromagnets 410 arranged in the circumferential direction are configured such that the magnetic poles facing the rotating shaft 250 switch in the circumferential direction, and the electromagnets 410 generate an electromagnetic force that attracts the rotating shaft 250.

[0056] Furthermore, as shown in Figure 4, the radial magnetic bearing 400 may also be of the homopolar type. In the homopolar type, the stator core 411 is magnetized in the axial direction by the current flowing through the coil 412, and the magnetic poles facing the rotation axis 250 are the same in the circumferential direction for the multiple electromagnets 410 arranged in the circumferential direction. In the homopolar type, a bias magnetic flux that attracts the rotation axis 250 acts on the stator core 411 side of each of the multiple electromagnets 410 by a permanent magnet (not shown), and one of the pair of radially opposing electromagnets 410 acts an attractive electromagnetic force on the rotation axis 250, while the other acts a repulsive electromagnetic force on the rotation axis 250. As a result, one electromagnet 410 can strengthen the bias magnetic flux, and the other electromagnet can weaken the bias magnetic flux, and as a result, the radial magnetic bearing 400 can adjust the magnetic force acting on the rotation axis 250 and adjust the position of the rotation axis 250.

[0057] The power supply 450 supplies drive power to the radial magnetic bearing 400 through the power conversion circuit 460.

[0058] The power conversion circuit 460 uses power supplied from the power supply 450 to apply a desired drive voltage to the coil 412 of the electromagnet 410 in the radial magnetic bearing 400. For example, the power conversion circuit 460 includes a switching device (also referred to as a "switching element" or "semiconductor switch," etc.). As a result, the power conversion circuit 460 can output a desired drive voltage to the radial magnetic bearing 400 through the switching operation of the switching device under the control of the controller 700. The power conversion circuit 460 is, for example, a linear amplifier or a PWM (Pulse Width Modulation) amplifier.

[0059] The thrust magnetic bearing 500 supports the thrust load of the rotating shaft 250 non-contact by electromagnetic force. The thrust magnetic bearing 500 includes a pair of electromagnets 510, each fixed to the inner surface of the casing 100. The pair of electromagnets 510 are positioned adjacent to each of the axial ends of a disc-shaped thrust disk (also called a "collar") 260, which is provided on the rotating shaft 250 and is centered on the axis AX. The thrust disk 260 is made of a magnetic material, and the thrust magnetic bearing 500 maintains the position of the rotating shaft 250, which is integrated with the thrust disk 260, non-contact by the magnetic attraction force of the pair of electromagnets 510 to the thrust disk 260.

[0060] The touchdown bearing 600 is provided to suppress contact between the rotating shaft 250 and the radial magnetic bearing 400, and between the thrust disk 260 and the electromagnet 510 of the thrust magnetic bearing 500. The touchdown bearing 600 is, for example, mainly composed of angular contact ball bearings.

[0061] The controller 700 controls the drive of the radial magnetic bearing 400 by operating the power conversion circuit 460.

[0062] The functions of the controller 700 are realized by any hardware, or any combination of hardware and software. For example, the controller 700 is centered around a computer that includes a CPU (Central Processing Unit), a memory device, an auxiliary storage device, and an interface device for input / output with external devices. The memory device is, for example, SRAM (Static Random Access Memory). The auxiliary storage device is, for example, EEPROM (Electronic Erasable Programmable Read-Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), or flash memory. The interface device includes, for example, an external interface for connecting to an external storage medium and a communication interface for communicating with other devices. The controller 700 can realize various functions by loading programs installed in the auxiliary storage device into the memory device and executing them on the CPU. The controller 700 can also retrieve and install programs from a storage medium via the external interface, or retrieve and install programs from other devices via the communication interface.

[0063] The compressor 10 is equipped with, for example, a position sensor 800 and a current sensor 900 (see Figure 5, etc.), as described later, and the controller 700 controls the drive of the radial magnetic bearing 400 based on the outputs of the position sensor 800 and the current sensor 900.

[0064] [First example of a control method for rotating shafts and magnetic bearing systems] Referring to Figures 5 to 8, a first example of a control method for the rotating shaft / magnetic bearing system SYS will be described. The rotating shaft / magnetic bearing system SYS, which includes the rotating shaft 250 and the radial magnetic bearing 400, is the object controlled by the controller 700.

[0065] Figure 5 shows a first example of a control method for the rotating shaft / magnetic bearing system SYS. Figure 6 is a block diagram showing an example of state feedback control for the radial magnetic bearing 400. Figure 7 shows an example of the frequency characteristics of the actual machine and model of the rotating body RT including the rotating shaft 250. Figure 8 shows an example of the relationship between the rotational speed of the rotating shaft 250 and the magnitude of vibration. Specifically, Figure 8 includes Figure 8A, which shows the relationship between the rotational speed of the rotating shaft 250 and the rotational frequency, and Figure 8B, which shows the relationship between the rotational speed of the rotating shaft 250 and the magnitude of vibration.

[0066] As shown in Figure 5, the controller 700 includes a position controller 710, a current controller 720, a feedback compensator 730, and a voltage command output unit 740. These control elements may be implemented, for example, by hardware processing of an arithmetic circuit, by software processing in which a program installed in an auxiliary storage device is loaded into a memory device and executed by a CPU, or by a combination of both processes.

[0067] The position controller 710 is a control element for controlling the position of the rotation axis 250. The position controller 710 sets and outputs a target value (current target value) for the current of the coil 412 so that the actual position of the rotation axis 250 approaches (preferably matches) the target position. For example, the position controller 710 is a PI (Proportional Integral) controller that sets the current target value of the coil 412 based on the deviation between the detected position value (position detection value) of the rotation axis 250 output from the position sensor 800 and the target position of the rotation axis 250.

[0068] The position sensor 800 is a non-contact and highly responsive position sensor such as an eddy current sensor, induction sensor, capacitance sensor, optical sensor, or Hall sensor.

[0069] The current controller 720 is a control element for controlling the current of the coil 412. The current controller 720 outputs a voltage command value (voltage command value) Vc1 to apply to the coil 412 so that the actual current value of the coil 412 approaches (preferably matches) the current target value set by the position controller 710. For example, the current controller 720 is a PI controller that outputs a voltage command value Vc1 based on the current target value of the coil 412 and the detected value of the current of the coil 412 output by the current sensor 900.

[0070] The feedback compensator 730 is a control element that performs control (vibration suppression control) to suppress the natural vibration of the rotating shaft 250 based on feedback from the system (rotating shaft / magnetic bearing system SYS) which includes the rotating shaft 250 and the radial magnetic bearing 400 as the controlled objects. The feedback compensator 730 outputs a command value (voltage command value Vc2) for the voltage of the coil 412 using feedback control.

[0071] In this example, the feedback compensator 730 performs state feedback control for the rotating shaft / magnetic bearing system SYS.

[0072] For example, as shown in Figure 6, the basic idea of ​​state feedback control is that the observed state x of the rotating shaft / magnetic bearing system SYS is fed back to the feedback compensator 730 (path F61). The state x is, for example, the state x1 to x of the rotating shaft / magnetic bearing system SYS. n This is a column vector where n is an integer greater than or equal to 2. State x k (k=1,···,n) includes at least one natural vibration state. The voltage command output section 732 of the feedback compensator 730 outputs a voltage command value Vc2 (=K·x) multiplied by the gain K based on the feedback state x to the rotating shaft / magnetic bearing system SYS as input u (path F62). Gain K is, for example, gain k1~k n This is a vector.

[0073] The rotating shaft-magnetic bearing system SYS is modeled by the following equations of state, (1) and (2), which include the natural vibrations of the rotating body RT, which rotates as a whole including the rotating shaft 250, using, for example, input u, output y, state x, and matrices A, B, and C.

[0074]

number

[0075] As a result, the feedback compensator 730 determines the natural vibration state x of the rotating body RT. k is zero By appropriately setting the gain K so that the natural vibrations included in the state equation of the rotating shaft 250 can be suppressed, and a voltage command value Vc2 can be output.

[0076] The rotating body RT includes an impeller 200 and a thrust disc 260, which rotate together with the rotating shaft 250.

[0077] For example, as shown in Figure 7, the rotating shaft-magnetic bearing system SYS is modeled using a transfer function representation based on the frequency characteristics of the actual compressor 10, which includes a rotating shaft 250 and radial magnetic bearings 400. In this example, the rotating shaft-magnetic bearing system SYS, including the first-order natural vibration among the first to third-order natural vibrations represented in the actual machine, is modeled using a transfer function representation. This allows the transfer function of the model to suppress the first-order natural vibration to be obtained. Furthermore, if it is necessary to suppress not only the first-order natural vibration but also the second-order, third-order, and higher-order natural vibrations, the transfer function of the model including the second-order, third-order, and fourth-order and higher-order natural vibrations in addition to the first-order natural vibration is obtained. Then, by converting the model from a transfer function representation to a state-space representation, the state equation of the model of the rotating shaft-magnetic bearing system SYS is obtained.

[0078] For example, the rotating shaft-magnetic bearing system SYS is modeled as a transfer function P(s) by equation (3) below, including at least one natural vibration of the rotating body RT.

[0079] [Number]

[0080] Then, from Equation (3), the rotation axis-magnetic bearing system SYS is modeled as the state equation of the state-space representation of Equations (1) and (2) represented by the state x, matrices A, B, and C in the following Equations (4) to (7).

[0081] [Number]

[0082] For Equations (1) and (2), by multiplying the state x by a gain K as the input u and inputting it, the following autonomous system of Equation (8) is obtained.

[0083] [Number]

[0084] The eigenvalues of the row example (A - BK) are the poles of the state feedback control system, and by appropriately setting the gain K, the poles of the state feedback control system can be freely arranged. Therefore, for example, using a known pole placement method, the gain K can be preset so that the poles representing the state of natural vibration are appropriately arranged.

[0085] Usually, it is difficult to observe all the states x included in the state x k . Therefore, in this example, the feedback compensator 730 includes a state observer 731 that estimates the state x, and the state observer 731 outputs an estimated state x e as the estimation result of the state x. The estimated state x e is a column vector by the estimated state x 1e to x ne , and each corresponds to the state x1 to x n .

[0086] For example, the state observer 731 can be represented by the following equation (9) using a matrix L that is set as appropriate.

[0087]

number

[0088] As shown in Figure 6, the electromagnetic force Fd of coil 412 and the position Pd of the rotating shaft 250, which are outputs y of the rotating shaft / magnetic bearing system SYS, are fed back to the state observer 731 (path F63). Based on the electromagnetic force Fd of coil 412 and the position Pd of the rotating shaft 250, the state observer 731 estimates the state x e Obtain the estimated state x e This is fed back to the voltage command output unit 732 (path F64). Then, the voltage command output unit 732 determines the estimated state x e Based on this, the voltage command value Vc2 (=K·x) is obtained by multiplying by the gain K. e The output is sent to the rotating shaft / magnetic bearing system SYS (path F65). This allows the feedback compensator 730 to perform state feedback control of the rotating shaft / magnetic bearing system SYS using the state observer 731.

[0089] Specifically, the state observer 731 estimates the state x based on information regarding the position of the rotation axis 250 (position information) and information regarding the electromagnetic force of the coil 412. e Obtain it.

[0090] For example, as shown in Figure 5, the information regarding the position of the rotation axis 250 that is input to the state observer 731 is the position detection value of the rotation axis 250 acquired by the position sensor 800.

[0091] Furthermore, as shown in Figure 5, for example, the information regarding the electromagnetic force of the coil 412 used in the state observer 731 is, for example, the current detection value of the coil 412 obtained by the current sensor 900. Alternatively, the information regarding the electromagnetic force of the coil 412 used in the state observer 731 may be the voltage command value Vc3, described later, output from the voltage command output unit 740 to the power conversion circuit 460. Alternatively, the information regarding the electromagnetic force of the coil 412 used in the state observer 731 may be obtained by calculation from the position information of the rotation axis 250 and the mass information of the rotating body RT including the rotation axis 250.

[0092] For example, if the rotating shaft / magnetic bearing system SYS is modeled by the state equations (1) and (2) based on the above equations (4) to (7), the voltage command output unit 732 includes multipliers 732A1, 732A2, 732A3, and 732A4, and an adder 732B, as shown in Figure 5.

[0093] The multiplier 732A1 outputs the estimated state x from the state observer 731. 1e The result is multiplied by the gain k1 and output. The multiplier 732A2 takes the estimated state x output from the state observer 731 as the result. 2e The result is multiplied by the gain k2 and output. The multiplier 732A3 takes the estimated state x output from the state observer 731. 3e The result is multiplied by the gain k2 and output. The multiplier 732A4 takes the estimated state x output from the state observer 731 as input. 4e The result is multiplied by the gain k4 and output.

[0094] The adder 732B adds the output values ​​from the multipliers 732A1, 732A2, 732A3, and 732A4 and outputs the voltage command value Vc2. In other words, the adder 732B calculates and outputs the voltage command value Vc2 using the following equation (10).

[0095]

number

[0096] The voltage command output unit 740 obtains a voltage command value Vc3 based on the voltage command value Vc1 output from the current controller 720 and the voltage command value Vc2 output from the feedback compensator 730, and outputs it to the power conversion circuit 760. As a result, the power conversion circuit 760 operates the switching device appropriately to apply a voltage corresponding to the voltage command value Vc3 to the coil 412. Therefore, the controller 700 can operate the power conversion circuit 760 so that the rotating shaft 250 approaches the target position and suppresses the natural vibration of the rotating shaft 250.

[0097] For example, as shown in Figure 5, the voltage command output unit 740 calculates the voltage command value Vc3 (=Vc1+Vc2) by adding the voltage command value Vc1 and the voltage command value Vc2. Alternatively, the voltage command output unit 740 may calculate the voltage command value Vc3 by multiplying at least one of the voltage command values ​​Vc1 and Vc2 by a predetermined value to amplify or attenuate at least one of Vc1 and Vc2, and then adding them together.

[0098] Furthermore, as shown in Figure 4, in the heteropolar radial magnetic bearing 400, a pair of electromagnets 410 located radially opposite each other around the rotation axis 250 generate attractive forces in opposite directions. Therefore, for one of the electromagnets 410 located vertically downwards, the voltage command output unit 740 obtains a voltage command value Vc3 based on a voltage command value Vc4 (=-Vc2) obtained by inverting the sign of the voltage command value Vc2 output from the feedback compensator 730. For example, the voltage command output unit 740 calculates a voltage command value Vc3 (=Vc1+Vc4) by adding a voltage command value Vc1 and a voltage command value Vc4.

[0099] Thus, in this example, the controller 700 controls the output voltage applied from the power conversion circuit 760 to the coil 412 based on the voltage command value Vc2 obtained using the feedback compensator 730, in addition to the voltage command value Vc1 obtained using the position controller 710 and the current controller 720. As a result, the controller 700 can exhibit high responsiveness to vibrations of the rotating shaft 250 through the action of the voltage command value Vc2, which is obtained from the position information of the rotating shaft 250 and the electromagnetic force information of the coil 412 without having to set a current target value.

[0100] For example, consider the case where the rotational speed of the rotating shaft 250 is increased from a levitating stationary state to a speed range where the rotational frequency is higher than the natural frequency of the rotating body RT, as shown in Figure 8A.

[0101] In this case, a centrifugal force with the same frequency as the rotation frequency acts on the rotating shaft 250. As shown in Figure 8B, the vibration of the rotating shaft 250 increases rapidly in the rotation speed range of the rotating shaft 250 corresponding to the rotation frequency near the natural frequency of the rotating body RT (i.e., the rotation speed range near the critical speed of the rotating body RT). Therefore, control based solely on the voltage command value Vc1 obtained using the position controller 710 and current controller 720 has relatively low responsiveness and may not be able to cope with the rapid increase in vibration of the rotating shaft 250, potentially failing to suppress the natural vibration of the rotating shaft 250. As a result, the rotating shaft 250 may not be able to exceed the rotation speed corresponding to the natural frequency, and the rotation speed may not be able to be increased to the desired level.

[0102] In contrast, in this example, the controller 700 exhibits relatively high responsiveness to vibrations of the rotating shaft 250 through control based on the voltage command value Vc2, and can suppress the natural vibration of the rotating shaft 250. Therefore, the controller 700 can increase the rotational speed of the rotating shaft 250 to a rotational speed range corresponding to a rotational frequency that exceeds the natural frequency of the rotating body RT.

[0103] In this example, the controller 700 controls the output voltage applied from the power conversion circuit 760 to the coil 412 based on the voltage command value Vc1 obtained using the position controller 710 and the current controller 720, in addition to the voltage command value Vc2 obtained using the feedback compensator 730. This prevents the current value of the coil 412 and the electromagnetic force of the electromagnet 410 based on that current value from deviating from the desired value, thereby preventing the radial magnetic bearing 400 from stably supporting the rotating shaft 250.

[0104] For example, in mass-produced products such as radial magnetic bearings 400 and power conversion circuits 460, manufacturing tolerances and characteristic changes due to heat during operation may exist in the electromagnets 410 and power conversion circuits 460. Therefore, in control based on the voltage command value Vc2 obtained using the feedback compensator 730, the current value of the coil 412 and the electromagnetic force of the electromagnet 410 may deviate significantly from the desired values ​​due to manufacturing tolerances and characteristic changes due to heat during operation, which may prevent the radial magnetic bearing 400 from stably supporting the rotating shaft 250.

[0105] In contrast, in this example, the controller 700 can adjust the current value of the coil 412 and the electromagnetic force of the electromagnet 410 to approach desired values ​​by controlling based on the voltage command value Vc1 obtained using the position controller 710 and the current controller 720. As a result, the controller 700 can stably support the rotating body RT on the radial magnetic bearing 400.

[0106] In other words, in this example, the controller 700 controls the output voltage applied to the coil 412 based on both the voltage command value Vc1 and the voltage command value Vc2, thereby enabling the radial magnetic bearing 400 to stably support the rotating body RT while allowing the rotating body RT to pass through the critical speed corresponding to its natural frequency and increase its rotational speed.

[0107] Furthermore, in this example, the controller 700 is modeled by a state equation that includes the natural vibration of the rotating body RT, and the estimated state x of the rotating shaft / magnetic bearing system SYS as the controlled object is represented by this equation.e Using the state observer 731, which acquires the state, state feedback control is performed on the natural vibration state of the rotating body RT, and the voltage command value Vc2 is obtained.

[0108] This allows the controller 700 to appropriately suppress the natural vibration of the rotating body RT.

[0109] [Second example of a control method for rotating shafts and magnetic bearing systems] Referring to Figure 9, a second example of a control method for the rotating shaft / magnetic bearing system SYS will be described.

[0110] In the following examples, the same reference numerals are used for components that are the same as or corresponding to those in the first example described above. The explanation will focus on the differences from the first example, and explanations of components that are the same as or corresponding to those in the first example may be omitted. The same approach will be applied to the third to sixth examples of the control method for the rotating shaft / magnetic bearing system SYS described later, as well as to the examples of control methods already explained.

[0111] Figure 9 shows a second example of a control method for the rotating shaft / magnetic bearing system SYS.

[0112] As shown in Figure 9, in this example, the configuration of the current controller 720 differs from that of the first example described above, but it may be the same as the first example in other respects.

[0113] As shown in Figure 9, the current controller 720 includes a controller 721, a disturbance observer 722, and a voltage command output unit 723.

[0114] The controller 721 outputs a compensation amount to bring the current of coil 412 closer to the current target value, based on the deviation between the current target value output from the position controller 710 and the current detection value of coil 412 acquired by the current sensor 900. Specifically, the controller 721 is, for example, a PI controller, and outputs proportional and integral compensation amounts based on proportional and integral compensation amounts obtained by multiplying the deviation between the current target value and the current detection value of coil 412 by predetermined proportional gains and integral gains, respectively. In this case, for example, the integral gain is set to a relatively small value. Alternatively, the controller 721 may be, for example, a P (Proportional) controller, and output a proportional compensation amount obtained by multiplying the deviation between the current target value and the current detection value of coil 412 by a predetermined proportional gain.

[0115] The disturbance observer 722 estimates the deviation of the output voltage applied to coil 412 as a disturbance (voltage disturbance), which corresponds to the steady-state deviation of the actual current relative to the target current value of coil 412, based on the voltage command value Vc3 of coil 412 and the current detection value of coil 412 obtained by the current sensor 900. For example, the disturbance observer 722 obtains and outputs an estimated value of the voltage disturbance using an inverse model of the transfer function model of coil 412, which takes the voltage applied to coil 412 as input and the current of coil 412 as output.

[0116] The voltage command output unit 723 acquires and outputs a voltage command value Vc1 based on the compensation amount for the current of the coil 412 output from the controller 721 and the estimated value of the voltage disturbance corresponding to the steady-state deviation of the current of the coil 412 output from the disturbance observer 722. For example, the voltage command value Vc1 is obtained by adding the compensation amount and the estimated value of the voltage disturbance. This makes it possible to suppress the steady-state deviation of the current of the coil 412, which may occur with only the proportional compensation amount of the controller 721, by weakening the effect of the I (Integral) controller (integral controller) with a relatively small integral gain, or without using an I controller at all.

[0117] Thus, in this example, the current controller 720 can suppress the steady-state deviation of the current in coil 412 and the deviation between the detected current value and the target current value of coil 412 by using the disturbance observer 722, while weakening the effect of the I controller (i.e., the integral compensation amount), or without using the I controller (integral compensation amount).

[0118] For example, if the action of the I controller (specifically, the proportional gain) is relatively large, the current controller 720 and the feedback compensator 730 may interfere with each other, and the presence of the integral compensation may reduce the effect of the voltage command value Vc2 output from the feedback compensator 730 on suppressing the natural vibration of the rotating body RT.

[0119] In contrast, in this example, the controller 700 weakens the effect of the integral compensation amount within the current controller 720, or acquires the voltage command value Vc1 without using the integral compensation amount, thereby weakening the responsiveness of the voltage command value Vc1 to the voltage command value Vc2. As a result, the controller 700 can prevent situations in which the suppression effect of the natural vibration of the rotating body RT is reduced by using the feedback compensator 730.

[0120] [Third example of a control method for rotating shafts and magnetic bearing systems] Referring to Figure 10, a third example of a control method for the rotating shaft / magnetic bearing system SYS will be described.

[0121] Figure 10 shows a third example of a control method for the rotating shaft / magnetic bearing system SYS.

[0122] As shown in Figure 10, this example differs from the first and second examples described above in that the feedback compensator 730 includes a disturbance observer 733, but may be the same as the first example described above in other respects.

[0123] The disturbance observer 733 estimates the deviation (error) of the position of the rotating shaft 250, which corresponds to the steady-state deviation of the electromagnetic force of the coil 412, as a disturbance (position disturbance), based on the position information of the rotating shaft 250 and the information regarding the electromagnetic force of the coil 412. The steady-state deviation of the electromagnetic force of the coil 412 is a steady-state deviation caused by the model error of the rotating shaft / magnetic bearing system SYS. For example, the disturbance observer 733 obtains and outputs an estimated value of the position disturbance using a transfer function model or a state-space model that represents the relationship between the position of the rotating shaft 250 and the electromagnetic force of the coil 412.

[0124] The voltage command output unit 732 outputs the estimated state x from the state observer 731 based on the estimated position disturbance obtained by the disturbance observer 733. e This corrects the estimated state x obtained by the state observer 731 due to the model error of the rotating shaft / magnetic bearing system SYS. e This is because a significant error may occur in the actual state x. Then, the voltage command output unit 732 outputs the corrected estimated state x e Based on this, the voltage command value Vc2 is calculated and output.

[0125] Thus, in this example, the controller 700 uses the disturbance observer 733 to acquire the voltage command value Vc2, taking into account the steady-state deviation of the electromagnetic force of the coil 412 caused by the model error of the rotating shaft / magnetic bearing system SYS. As a result, the controller 700 can suppress the influence of the model error on the control stability of the vibration suppression control of the rotating body RT, and improve control stability.

[0126] [Fourth example of a control method for rotating shafts and magnetic bearing systems] Referring to Figure 11, a fourth example of a control method for the rotating shaft / magnetic bearing system SYS will be described.

[0127] Figure 11 shows a fourth example of a control method for the rotating shaft / magnetic bearing system SYS.

[0128] As shown in Figure 11, this example differs from the first to third examples described above in that the controller 700 includes an unbalanced compensator 750 and multipliers 751,752, and may otherwise be the same as any one of the first to third examples described above.

[0129] The unbalance compensator 750 acquires a compensation amount for the unbalance of the electromagnetic force of the electromagnet 410 acting on the rotating shaft 250. The unbalance of the electromagnetic force of the electromagnet 410 acting on the rotating shaft 250 is a phenomenon in which the electromagnetic force acting on the rotating shaft 250 increases as the distance to the rotating shaft 250 decreases.

[0130] For example, as shown in Figure 11, the unbalance compensator 750 obtains and outputs the unbalance compensation amount CA (=(δ-s) / δ) by dividing the value obtained by subtracting the displacement s of the rotation axis 250 from the target position by the distance δ between the target position of the rotation axis 250 and the electromagnet 410.

[0131] The multiplier 751 corrects and outputs the current target value by multiplying the current target value of the coil 412 output from the position controller 710 by an unbalance compensation amount CA.

[0132] The current controller 720 acquires and outputs a voltage command value Vc1 based on the current target value of the coil 412, which has been corrected by the multiplier 751, and the current detection value of the coil 412, which is obtained by the current sensor 900.

[0133] The multiplier 752 corrects the voltage command value Vc2 output from the feedback compensator 730 by multiplying it by an unbalance compensation amount CA, and outputs the voltage command value Vc2'.

[0134] The voltage command output unit 740 obtains a voltage command value Vc3 based on the voltage command value Vc1 output from the current controller 720 and the voltage command value Vc2' output from the multiplier 752, and outputs it to the power conversion circuit 460.

[0135] For example, as shown in Figure 11, the voltage command output unit 740 calculates the voltage command value Vc3 (=Vc1+Vc2') by adding the voltage command value Vc1 and the voltage command value Vc2'. Alternatively, the voltage command output unit 740 may calculate the voltage command value Vc3 by multiplying at least one of the voltage command values ​​Vc1 and Vc2' by a predetermined value to amplify or attenuate at least one of Vc1 and Vc2', and then adding them together.

[0136] Thus, in this example, the controller 700 can control the output voltage applied from the power conversion circuit 460 to the coil 412, taking into account the unbalance compensation amount CA for the voltage command values ​​Vc1 and Vc2. As a result, the controller 700 can suppress the effects of unbalance in the electromagnetic force acting from the electromagnet 410 on the rotating shaft 250, and stabilize the support of the rotating shaft by the magnetic bearing.

[0137] [Fifth example of a control method for rotating shafts and magnetic bearing systems] Referring to Figure 12, a fifth example of a control method for the rotating shaft / magnetic bearing system SYS will be described.

[0138] Figure 12 shows a fifth example of a control method for a rotating shaft and magnetic bearing system.

[0139] As shown in Figure 12, this example differs from the first to fourth examples described above in that the feedback compensator 730 uses PD (Proportional Derivative) control instead of state feedback control, but may be the same as the first example described above in other respects.

[0140] The feedback compensator 730 includes a PD controller 734, a force estimator 735, and a multiplier 736.

[0141] The PD controller 734 outputs a PD compensation amount, which is the sum of a proportional compensation amount and a differential compensation amount for the position information of the rotating shaft 250, based on the input position information of the rotating shaft 250. For example, the PD controller 734 outputs a PD compensation amount, which is the sum of a proportional compensation amount obtained by multiplying the position detection value of the rotating shaft 250, acquired by the position sensor 800, by a proportional gain, and a differential compensation amount obtained by multiplying the differential value of the position detection value of the rotating shaft 250 by a differential gain.

[0142] The force estimator 735 calculates an estimated value of the electromagnetic force of coil 412 based on information regarding the electromagnetic force of coil 412.

[0143] The multiplier 736 multiplies the deviation obtained by subtracting the estimated electromagnetic force of the coil 412 output from the force estimator 735 from the PD compensation amount output from the PD controller 734 by a predetermined gain and outputs it as a voltage command value Vc2.

[0144] Thus, in this example, the controller 700 acquires a voltage command value Vc2 based on the output of the PD controller 734, which is based on information regarding the position of the rotating shaft 250, and the output of the force estimator 735, which is based on information regarding the electromagnetic force of the coil 412. As a result, the controller 700 can exhibit high responsiveness to vibrations of the rotating shaft 250 through the action of the voltage command value Vc2, which is acquired from the position information of the rotating shaft 250 and the electromagnetic force information of the coil 412 without having to set a current target value. Therefore, the controller 700 can increase the rotational speed of the rotating shaft 250 to a speed range corresponding to a rotational frequency that exceeds the natural frequency of the rotating body RT.

[0145] [Sixth example of a control method for rotating shafts and magnetic bearing systems] Referring to Figure 13, a sixth example of a control method for the rotating shaft / magnetic bearing system SYS will be described.

[0146] Figure 13 shows a sixth example of a control method for the rotating shaft / magnetic bearing system SYS.

[0147] As shown in Figure 13, this example differs from the first to fifth examples described above in that the feedback compensator 730 uses a phase filter, but may be the same as the first example described above in other respects.

[0148] The feedback compensator 730 includes a phase filter 737, a multiplier 738, a force estimator 735, and a multiplier 739.

[0149] The phase filter 737 performs phase lead compensation on the input position information signal of the rotation axis 250. For example, as shown in Figure 13, the phase filter 737 performs phase lead compensation on the time-series signal of the position detection value acquired by the position sensor 800 and outputs it.

[0150] The multiplier 738 multiplies the output signal of the phase filter 737 by a predetermined gain and outputs it.

[0151] The multiplier 739 multiplies the deviation obtained by subtracting the output of the force estimator 735 from the output of the multiplier 738 by a predetermined gain and outputs it as a voltage command value Vc2.

[0152] Thus, in this example, the controller 700 applies a phase filter 737 to the position information of the rotating shaft 250 to obtain a voltage command value Vc2. As a result, the controller 700 can exhibit relatively high responsiveness to vibrations of the rotating shaft 250 through control based on the voltage command value Vc2, and can also increase the phase margin of control stability near the natural frequency of the rotating body RT. Therefore, the controller 700 can suppress the natural vibration of the rotating shaft 250.

[0153] [An example of transmission characteristics of a control system related to a rotating shaft and magnetic bearing system] Referring to Figures 14 to 16, an example of the transfer characteristics (transfer function) of the control system corresponding to the control method of the rotating shaft / magnetic bearing system SYS according to this embodiment will be described.

[0154] Figure 14 is a Bode plot showing an example of the frequency characteristics of a rotating body RT including the rotating shaft 250. Figure 15 is a Bode plot showing an example of the transfer characteristics (transfer function) of an open loop controlled by a current controller 720 from the current detection value to the voltage command value Vc1 (hereinafter referred to as "current-controlled open loop" for convenience). Figure 16 is a Bode plot showing an example of the transfer characteristics (transfer function) of an open loop controlled by a current controller 720 from the position detection value to the voltage command value Vc3 (hereinafter referred to as "position-controlled open loop" for convenience).

[0155] Specifically, Figure 14 shows a concrete example of the frequency characteristics of the rotating body RT in a stationary state, and includes Figure 14A, which shows a concrete example of the amplitude (gain) frequency characteristics, and Figure 14B, which shows a concrete example of the phase frequency characteristics, for the rotating body RT in a stationary state. Furthermore, Figure 15, based on the frequency characteristics of the rotating body RT in Figure 14, includes Figure 15A, which shows a concrete example of the amplitude (gain) frequency characteristics for a current-controlled open loop, and Figure 15B, which shows a concrete example of the phase frequency characteristics for a current-controlled open loop. Furthermore, Figure 16, based on the frequency characteristics of the rotating body RT in Figure 14, includes Figure 16A, which shows a concrete example of the amplitude (gain) frequency characteristics for a position-controlled open loop, and Figure 16B, which shows a concrete example of the phase frequency characteristics for a position-controlled open loop.

[0156] Furthermore, Figures 16A and 16B show the frequency characteristics of the position-controlled open-loop according to the comparative example, in addition to the frequency characteristics of the position-controlled open-loop according to the embodiment (for example, the first example of the control method described above). In the position-controlled open-loop according to the comparative example, unlike the embodiment described above, the feedback compensator 730 is omitted, and the power conversion circuit 460 is driven only by the voltage command value Vc1 output from the current controller 720.

[0157] As shown in Figure 14A, the rotating body RT has a frequency f cs1 (Hereinafter, "1st resonance frequency f cs1 The first-order resonance (first-order natural vibration) F14-1 peaks at '', and the frequency f cs2 (Hereinafter, "secondary resonance frequency f cs2This represents the frequency characteristics including the second-order resonance (second-order natural vibration) with a peak at ''. Below, the rotational speed of the rotating body RT corresponding to the first and second resonances of the stationary rotating body RT is comprehensively referred to as "critical speed V". cs It is sometimes referred to as "primary critical speed V". In addition, the rotational speeds of the rotating body corresponding to the primary and secondary resonances are individually called "primary critical speed V". cs1 " and "Secondary dangerous speed V cs2 It is sometimes referred to as "[...]."

[0158] As shown in Figure 15A, the amplitude characteristics (gain characteristics) of the current-controlled open-loop are as follows: Primary critical velocity V cs1 The corresponding primary resonant frequency f cs1 A cutoff frequency f lower than cutoff It has. In other words, the amplitude (gain) of the current-controlled open loop is critical speed V cs (That is, the primary critical speed V cs1 and secondary dangerous speed V cs2 ) corresponds to the resonant frequency (i.e., the first resonant frequency f cs1 and secondary resonant frequency f cs2 ) has damping characteristics. As a result, the controller 700 controls the critical speed V of the rotating body RT by current control open loop. cs It is possible to dampen vibrations in this area.

[0159] As shown in Figure 16B, in the comparative example, the phase of the position control open loop is the secondary critical velocity V cs2 The corresponding secondary resonant frequency f cs2 Within the following frequency range, the phase is centered around -180 degrees. The phase of the position-controlled open loop is the primary resonant frequency f. cs1 and secondary resonant frequency f cs2 In each of these locations, the range is -135 degrees to -180 degrees. Therefore, the critical speed V of the rotating body RT is cs In the vicinity, the stability of the open-loop position control is very low, and as a result, it may not be possible to suppress the primary and secondary resonances of the rotating body RT. Therefore, for example, when the rotating shaft 250 reaches the primary critical speed V cs1It is not possible to exceed the rotational speed range in the vicinity. For example, the controller corresponding to the comparative example sets the rotational speed of the rotating shaft 250 to the primary critical speed V. cs1 It may not be possible to raise the level beyond the desired level.

[0160] In contrast, as shown in Figure 16B, in the above embodiment, the phase of the position-controlled open loop is further away from -180 degrees towards 0 degrees compared to the comparative example. The phase of the position-controlled open loop is the primary resonant frequency f cs1 and secondary resonant frequency f cs2 In each of these, the range is -90 degrees to 90 degrees. Therefore, the critical speed V of the rotating body RT is cs In the vicinity, the stability of the open-loop position control is very high, and as a result, the controller 700 can suppress the primary and secondary resonances of the rotating body RT. Therefore, the controller 700 can, for example, control the rotational speed of the rotating shaft 250 to the primary critical speed V of the rotating body RT. cs1 It can be increased to a desired rotational speed range beyond that.

[0161] [Other examples of transmission characteristics of control systems related to rotating shafts and magnetic bearing systems] Referring to Figures 17 and 18, other examples of the transfer characteristics (transfer function) of the control system corresponding to the control method of the rotating shaft / magnetic bearing system SYS according to this embodiment will be described.

[0162] In the following examples, we will focus on explaining the differences from the example of control system transmission characteristics described above (Figures 14-16), and may omit explanations of parts that are the same as or correspond to the example of control system transmission characteristics described above.

[0163] Figure 17 is a Bode plot showing another example of the frequency characteristics of a rotating body RT including the rotation axis 250. Figure 18 is a Bode plot showing another example of the transfer characteristics (transfer function) of an open loop (position-controlled open loop) from a position detection value to a voltage command value Vc3.

[0164] Specifically, Figure 17 shows the critical speed V. cs (Specifically, the primary critical speed V cs1This shows a specific example of the frequency characteristics of a rotating body RT in a rotating state at the primary critical speed V. cs1 Figure 17A shows a specific example of the frequency characteristics of the amplitude (gain) for a rotating body RT in a rotating state, and Figure 17B shows a specific example of the frequency characteristics of the phase. Furthermore, Figure 18 includes Figure 18A, which shows a specific example of the frequency characteristics of the amplitude (gain) for a position-controlled open loop, and Figure 18B, which shows a specific example of the frequency characteristics of the phase for a position-controlled open loop, based on the frequency characteristics of the rotating body RT in Figure 17.

[0165] Furthermore, Figures 18A and 18B show the frequency characteristics of the position control open loop according to the embodiment (for example, the first example of the control method described above), as well as the frequency characteristics of the position control open loop according to the comparative example. The comparative example is the same as in Figures 16A and 16B described above.

[0166] As shown in Figure 17A, the rotating body RT has a frequency response that includes a primary resonance F17-1 and a secondary resonance F17-2, similar to the example described above (Figure 14). However, when the rotating body RT is in a rotating state, it comes to have two resonant frequencies separated above and below the resonant frequency in the stationary state. Specifically, the primary resonance F17-1 of the rotating body RT is the lower of the two primary resonant frequencies f cs1A ( <f cs1 The first-order resonance F17-1A peaks at ) and the other first-order resonance frequency f is higher cs1B (>f cs1 The primary resonance F17-1B, which peaks at ), is separated into two parts. Similarly, the secondary resonance F17-2 of the rotating body RT is separated into two parts with a lower secondary resonance frequency f cs2A ( <f cs2 The second resonance F17-2A peaks at ) and the other high second resonance frequency f cs2B (>f cs2 It is separated into a secondary resonance F17-2B with a peak at ) and another.

[0167] As shown in Figure 18B, in the comparative example, the phase of the position-controlled open loop is the separated primary resonant frequency f cs1A ,f cs1BFor more than half of the frequency range between these two points, the range is around -180 degrees. Therefore, the upper and lower primary resonant frequencies f are separated according to the rotation state of the rotating body RT. cs1A ,f cs1B Within the frequency range between these two points, the stability of the position-controlled open-loop can become very low. Also, in the comparative example, the phase of the position-controlled open-loop is separated by the secondary resonance frequency f. cs2A ,f cs2B For more than half of the frequency range between these two points, the range is relatively close to -180 degrees (-180 degrees to -90 degrees). Therefore, the upper and lower secondary resonant frequencies f are separated according to the rotation state of the rotating body RT. cs2A ,f cs2B Within the frequency range between these two points, the stability of the position-controlled open-loop system may become extremely low. As a result, the position-controlled open-loop system in the comparative example may not be able to suppress the primary and secondary resonances of the rotating body RT. Therefore, the primary resonance frequency f of the rotating shaft 250 separated into upper and lower parts is important. cs1A ,f cs1B The controller corresponding to the comparative example cannot pass through the rotational speed range before and after the critical speed, and the controller corresponding to the comparative example controls the rotational speed of the rotating body RT at the upper and lower separated primary resonant frequencies f cs1A ,f cs1B The primary critical speed V corresponds to cs1 It may not be possible to raise the rotational speed to the desired level, exceeding the rotational speed range centered around [a specific point].

[0168] In contrast, in the above-described embodiment, the phase of the position-controlled open loop is separated from -180 degrees towards 0 degrees compared to the comparative example. The phase of the position-controlled open loop is separated into upper and lower primary resonant frequencies f cs1A ,f cs1B Within the entire range between -90 degrees and 90 degrees (the textured area in Figure 18B), the phase is within the range of -90 degrees to 90 degrees. Similarly, the phase of the position-controlled open loop is the upper and lower separated secondary resonant frequency f cs2A ,f cs2B Within the entire range, it is in the range of -90 degrees to 90 degrees. Therefore, the primary resonant frequency f separated into upper and lower parts of the rotating body RT cs1A ,f cs1B The range between and the secondary resonant frequency fcs2A ,f cs2B Within this range, the stability of the open-loop position control is very high, and as a result, the controller 700 can suppress the primary and secondary resonances of the rotating body RT. Therefore, the controller 700 can, for example, control the rotational speed of the rotating shaft 250 to control the primary resonance frequency f separated into upper and lower parts. cs1A ,f cs1B The primary critical velocity V of the rotating body RT corresponds to the range between these two points. cs1 It can be increased to a desired level that exceeds the rotational speed range centered around [a specific point].

[0169] [Further examples of transmission characteristics of control systems related to rotating shafts and magnetic bearing systems] Referring to Figures 19 and 20, further examples of the transfer characteristics (transfer function) of the control system corresponding to the rotating shaft / magnetic bearing system SYS control method according to this embodiment will be described.

[0170] In the following examples, we will focus on explaining the differences between the control system's transmission characteristics described above (Figures 14-16) and other examples (Figures 17 and 18), and may omit explanations of parts that are the same as or correspond to the control system's transmission characteristics described above.

[0171] Figure 19 is a Bode plot showing yet another example of the frequency characteristics of a rotating body RT including the rotation axis 250. Figure 20 is a Bode plot showing yet another example of the transfer characteristics (transfer function) of an open loop (position-controlled open loop) from a position detection value to a voltage command value Vc3.

[0172] Specifically, Figure 19 shows the critical speed V. cs (Specifically, the primary critical speed V cs1 This shows a specific example of the frequency characteristics of a rotating body RT rotating at 1.67 times the primary critical speed V. cs1For the rotating body RT in a rotating state at 1.67 times the speed, it includes FIG. 19A showing a specific example of the frequency characteristics of the amplitude (gain) and FIG. 19B showing a specific example of the frequency characteristics of the phase. Also, FIG. 20 includes FIG. 20A showing a specific example of the frequency characteristics of the amplitude (gain) for the position control open loop and FIG. 20B showing a specific example of the frequency characteristics of the phase for the position control open loop, based on the frequency characteristics of the rotating body RT in FIG. 19.

[0173] In addition, in FIGS. 19A and 19B, in addition to the frequency characteristics of the rotating body RT in a rotating state at 1.67 times the first critical speed V cs1 the frequency characteristics of the rotating body RT in a rotating state at the first critical speed V cs1 are depicted (i.e., the frequency characteristics in FIGS. 17A and 17B). Also, in FIGS. 20A and 20B, in addition to the frequency characteristics of the position control open loop according to the embodiment (for example, the first example of the control method described above), the frequency characteristics of the position control open loop according to the comparative example are depicted. The comparative example is the same as in the case of FIGS. 16A and 16B described above.

[0174] As shown in FIG. 19A, the first resonance F19-1 of the rotating body RT is separated into a first resonance F19-1A with a peak at the lower first resonance frequency f cs1A (<f cs1 ) and a first resonance F19-1B with a peak at the higher other first resonance frequency f cs1B (>f[[ID=]19] cs1 ), similar to the case of the other examples (FIG. 17) described above. Similarly, the second resonance F19-2 of the rotating body RT is separated into a second resonance F19-2A with a peak at the lower second resonance frequency f cs2A (<f cs2 ) and a second resonance F19-2B with a peak at the higher other second resonance frequency f cs2B (>f cs2 ).

[0175] The interval between the resonance frequencies separated vertically tends to expand as the rotational speed of the rotating body RT increases. Therefore, as shown in FIG. 19A, the first resonance frequencies f cs1A , f cs1BThe interval between them is when the rotational speed of the rotating body RT reaches the primary critical speed V. cs1 The primary critical speed V is higher than in the case of cs1 The value is larger when it is 1.67 times (see arrow in Figure 19A). Similarly, the second resonant frequency f cs2A ,f cs2B The interval between them is when the rotational speed of the rotating body RT reaches the primary critical speed V. cs1 The primary critical speed V is higher than in the case of cs1 The value is larger when it is 1.67 times the original value.

[0176] As shown in Figure 20B, in the comparative example, the phase of the position-controlled open loop is the separated primary resonant frequency f cs1A ,f cs1B For more than half of the frequency range between these two points, the range is around -180 degrees. Therefore, the upper and lower primary resonant frequencies f are separated according to the rotation state of the rotating body RT. cs1A ,f cs1B Within the range between these two points, the stability of the position-controlled open-loop can become very low. Also, in the comparative example, the phase of the position-controlled open-loop is the separated secondary resonance frequency f. cs2A ,f cs2B For more than half of the frequency range between these two points, the range is relatively close to -180 degrees (-180 degrees to -90 degrees). Therefore, the upper and lower secondary resonant frequencies f are separated according to the rotation state of the rotating body RT. cs2A ,f cs2B Within this range, the stability of the position-controlled open-loop system may become very low. As a result, the position-controlled open-loop system in the comparative example may not be able to suppress the primary and secondary resonances of the rotating body RT. Therefore, the primary resonance frequency f of the rotating shaft 250 separated vertically is... cs1A ,f cs1B The primary critical speed V corresponds to cs1 It is not possible to exceed the rotational speed range before and after the specified value. For example, the controller corresponding to the comparative example sets the rotational speed of the rotating shaft 250 to the primary critical speed V. cs1 It may not be possible to raise it to the desired level of 1.67 times or more.

[0177] In contrast, in the above-described embodiment, the phase of the position-controlled open-loop is separated from -180 degrees in the direction of decreasing degrees compared to the comparative example. The phase of the position-controlled open-loop is separated into upper and lower primary resonant frequencies f cs1A ,f cs1B Within the entire range between -90 degrees and 90 degrees (the textured area in Figure 20B), the phase is within the range of -90 degrees to 90 degrees. Similarly, the phase of the position-controlled open loop is the upper and lower separated secondary resonant frequency f cs2A ,f cs2B Within the entire range between -90 degrees and 90 degrees, the position control open loop is in a very stable state within the range between the primary critical speed and the secondary critical speed separated above and below the rotating body RT. As a result, the controller 700 can suppress the primary and secondary resonances of the rotating body RT. Therefore, the controller 700 controls the rotation speed of the rotating shaft 250 to the primary critical speed V of the rotating body RT. cs1 A desired level that far exceeds this, i.e., the primary critical speed V cs1 It can be raised to a desired level of 1.67 times or more.

[0178] Furthermore, in a refrigeration system 1 (i.e., a turbo chiller) that uses a turbo compressor (i.e., a centrifugal compressor) as the compressor 10, the disturbance force due to stall is greater than the centrifugal force, and it is desirable to suppress vibrations caused by the disturbance force due to stall. For this reason, the controller 700 is designed to suppress vibrations caused by the disturbance force due to stall when operating at high rotational speeds where the possibility of stall in the turbo compressor is high (for example, the primary critical speed V cs1 During operation at extremely high rotational speeds (more than 1.67 times the normal speed), resonance of the rotating body RT associated with stalling can be suppressed.

[0179] [Other examples of control methods for rotating shafts and magnetic bearing systems] Referring to Figure 21, another example of a control method for the rotating shaft / magnetic bearing system SYS will be described.

[0180] Figure 21 shows another example of a control method for the rotating shaft / magnetic bearing system SYS.

[0181] Examples 1 to 6 of the above-described control methods for the rotating shaft and magnetic bearing system SYS may be modified or altered as appropriate. Hereinafter, examples of modifications or alterations made to Examples 1 to 6 of the above-described control methods for the rotating shaft and magnetic bearing system SYS may be referred to as "modified versions" for convenience.

[0182] For example, in the first to fourth examples of the control method for the rotating shaft / magnetic bearing system SYS described above, the controller 700 may change the specifications of the state observer 731 and the voltage command output unit 732 in the feedback compensator 730 in accordance with the change in the rotational speed of the rotating shaft 250. This is because the characteristics of the rotating body RT including the rotating shaft 250 change according to the rotational speed, and as a result, the state equation and transfer function of the rotating shaft / magnetic bearing system SYS change (see, for example, Figure 19 above). For example, multiple state observers 731 are prepared in advance in accordance with the change in the state equation of the rotating shaft / magnetic bearing system SYS in accordance with the change in the rotational speed of the rotating shaft 250, and the controller 700 switches the state observer 731 to be used in accordance with the change in the rotational speed of the rotating shaft 250. Alternatively, multiple gains K may be prepared in advance in accordance with the change in the state equation of the rotating shaft / magnetic bearing system SYS in accordance with the change in the rotational speed of the rotating shaft 250, and the controller 700 may switch the gain K to be used in the voltage command output unit 732 in accordance with the change in the rotational speed of the rotating shaft 250. Furthermore, the controller 700 may switch both the state observer 731 and the gain K in accordance with the change in the rotational speed of the rotating shaft 250.

[0183] Furthermore, in the fifth example of the control method for the rotating shaft / magnetic bearing system SYS described above, the controller 700 may change the specifications of the PD controller 734 and the multiplier 736 in the feedback compensator 730 in accordance with the change in the rotational speed of the rotating shaft 250. This is because the characteristics of the rotating body RT including the rotating shaft 250 change according to the rotational speed, and as a result, the state equation and transfer function of the rotating shaft / magnetic bearing system SYS change (see, for example, Figure 19 above). For example, multiple proportional gains and differential gains in the PD controller 734 are prepared in advance in accordance with the change in the transfer function of the rotating shaft / magnetic bearing system SYS in accordance with the change in the rotational speed of the rotating shaft 250, and the controller 700 switches at least one of the proportional gains and differential gains in the PD controller 734 in accordance with the change in the rotational speed of the rotating shaft 250. Furthermore, multiple gains for the multiplier 736 are pre-configured to match the change in the transfer function of the rotating shaft-magnetic bearing system SYS in response to the change in the rotational speed of the rotating shaft 250, and the controller 700 may switch the gain of the multiplier 736 in response to the change in the rotational speed of the rotating shaft 250. Alternatively, the controller 700 may switch at least one of the proportional gain and differential gain of the PD controller 734, as well as both the gain of the multiplier 736, in response to the change in the rotational speed of the rotating shaft 250.

[0184] Furthermore, in the sixth example of the control method for the rotating shaft / magnetic bearing system SYS described above, the controller 700 may change the specifications of the phase filter 737, multiplier 738, and multiplier 739 in accordance with the change in the rotational speed of the rotating shaft 250. This is because the characteristics of the rotating body RT, including the rotating shaft 250, change according to the rotational speed, and as a result, the state equation and transfer function of the rotating shaft / magnetic bearing system SYS change (see, for example, Figure 19 described above). For example, multiple phase filters 737 may be prepared in advance to match the change in the transfer function of the rotating shaft / magnetic bearing system SYS in accordance with the change in the rotational speed of the rotating shaft 250, and the controller 700 may switch the phase filter 737 being used in accordance with the change in the rotational speed of the rotating shaft 250. Alternatively, multiple gains for the multiplier 738 may be prepared in advance to match the change in the transfer function of the rotating shaft / magnetic bearing system SYS in accordance with the change in the rotational speed of the rotating shaft 250, and the controller 700 may switch the gain of the multiplier 738 in accordance with the change in the rotational speed of the rotating shaft 250. Furthermore, multiple gains for the multiplier 739 are pre-configured to match the change in the transfer function of the rotating shaft-magnetic bearing system SYS in response to the change in the rotational speed of the rotating shaft 250, and the controller 700 may switch the gain of the multiplier 739 in response to the change in the rotational speed of the rotating shaft 250. Alternatively, the controller 700 may switch two or three of the gains of the phase filter 737, the multiplier 738, and the multiplier 739 in response to the change in the rotational speed of the rotating shaft 250.

[0185] For example, as shown in Figure 21, an encoder 950 is provided to detect the rotational speed of the rotating shaft 250, and the detected value of the rotational speed of the rotating shaft 250 by the encoder (rotational speed detection value) is input to the feedback compensator 730 of the controller 700. This allows the feedback compensator 730 to recognize changes in the rotational speed of the rotating shaft 250. Alternatively, the controller 700 may recognize changes in the rotational speed of the rotating shaft 250 by acquiring information representing the rotational speed of the motor 300 from a power converter (e.g., an inverter device) that drives the motor 300. This is because the rotational speed of the motor 300 is equivalent to the rotational speed of the rotating shaft 250. In this case, the information acquired from the power converter that drives the motor 300 may be the detected value of a sensor (e.g., an encoder) that detects the rotational speed of the motor 300 and is used for drive control of the motor 300, or it may be the estimated value of the rotational speed of the motor 300 derived in the process of sensorless control.

[0186] Furthermore, in the third example of the control method described above and in this modified version, the feedback compensator 730 may be replaced with a Model Error Compensator (MEC) instead of the disturbance observer 733.

[0187] Furthermore, in the fourth example of the control method described above and in this modified version, instead of the multipliers 751 and 752, an alternative multiplier may be provided that multiplies the voltage command value Vc3 output from the voltage command output unit 740 by an unbalance compensation amount CA and outputs the voltage command value Vc3' to the power conversion circuit 760. In this case, the current controller 720 receives the current target value of the coil 412 output from the position controller 710, the voltage command value Vc2 output from the feedback compensator 730 is input to the voltage command output unit 740, and the voltage command value Vc3 output from the voltage command output unit 740 is input to the alternative multiplier.

[0188] Furthermore, in the third to sixth examples of the control method described above, and in their variations, the current controller 720 may be replaced with the current controller 720 of the second example of the control method described above.

[0189] Furthermore, in the fourth example of the control method described above and in this modified example, the feedback compensator 730 may be replaced with the feedback compensator 730 including the disturbance observer 733 or the model error suppression compensator, as in the third example of the control method described above and in this modified example.

[0190] Furthermore, in the fifth and sixth examples of the control method described above, and their variations, the unbalance compensator 750 and multipliers 751, 752 of the fourth example described above, or the unbalance compensator 750 and an alternative multiplier of the variation of the fourth example described above may be provided.

[0191] [Other embodiments] Other embodiments will be described.

[0192] The embodiments described above may be modified or altered as appropriate. Hereinafter, embodiments that have been modified or altered from the main embodiment described above will be referred to as "other embodiments" for convenience.

[0193] For example, in the main embodiment described above, a bearingless motor 420 may be used instead of the electric motor 300 and the radial magnetic bearing 400.

[0194] Figure 14 shows an example of a bearingless motor 420.

[0195] The bearingless motor 420 includes multiple electromagnets 410, and unlike the radial magnetic bearing 400, the electromagnets 410 apply power to the rotating shaft 250 that includes both a radial and circumferential component. As a result, the bearingless motor 420 supports the rotating shaft 250 with the radial component of the electromagnetic force applied by the electromagnets 410, while simultaneously applying rotational torque to the rotating shaft 250 with the circumferential component of the electromagnetic force, thereby rotating the rotating shaft 250.

[0196] Even when a bearingless motor 420 is used, the natural vibration of the rotating shaft 250 can be suppressed by the same control method as in the case of the radial magnetic bearing 400 in the main embodiment described above. For example, the controller 700 outputs a voltage command value Vc3 based on a voltage command value Vc1 and a voltage command value Vc5 obtained by multiplying the voltage command value Vc2 or voltage command value Vc2' by a correction value that changes according to the rotation angle of the rotating shaft 250. As a result, the controller 700 can appropriately suppress the natural vibration of the rotating body RT including the rotating shaft 250, similar to the case of the radial magnetic bearing 400.

[0197] Furthermore, the control methods for the radial magnetic bearing 400 and the bearingless motor 420 described above may also be adopted as control methods for the rotating shaft / magnetic bearing system SYS mounted on a compressor other than the refrigeration system 1.

[0198] Furthermore, the control methods for the radial magnetic bearing 400 and the bearingless motor 420 according to the main embodiment described above may be used as control methods for radial magnetic bearings and bearingless motors mounted on other types of compressors different from centrifugal compressors.

[0199] Furthermore, the control methods for the radial magnetic bearing 400 and the bearingless motor 420 according to the above-described embodiment may be used as control methods for radial magnetic bearings and bearingless motors that support the rotating shaft of other rotating devices different from the compressor.

[0200] [Effect] The operation of the control device and refrigeration system according to this embodiment will be described.

[0201] In a first aspect of this embodiment, a control device is provided for a magnetic bearing or bearingless motor that includes a coil that generates an electromagnetic force to attract or repel a rotating shaft and supports the rotating shaft in a non-contact manner, by operating a power conversion circuit that outputs power to the coil, thereby controlling the output voltage from the power conversion circuit to the coil. The control device is, for example, the controller 700 described above. The rotating shaft is, for example, the rotating shaft 250 described above. The coil is, for example, the coil 412 described above. The magnetic bearing is, for example, the radial magnetic bearing 400 described above. The bearingless motor is, for example, the bearingless motor 420 described above. The power conversion circuit is, for example, the power conversion circuit 460 described above. Specifically, the transfer function from the current value of the coil to the output voltage includes an integral element. The transfer function from the current value of the coil to the output voltage is, for example, the open-loop (current-controlled open-loop) transfer function from the current detection value to the voltage command value Vc1 described above. The integral element is, for example, an integral controller included in the current controller 720 described above. Furthermore, the amplitude of the open-loop transfer function, including the current value of the coil, has a damping characteristic in the frequency band above the critical speed of the rotating shaft. The critical speed of the rotational speed is, for example, the primary critical speed described above. The open-loop transfer function, including the current value of the coil at the critical speed of the rotating shaft, is, for example, the transfer function of the current-controlled open-loop described above. The phase of the open-loop transfer function, including the position of the rotating shaft, is in the range of -90 degrees or more and 90 degrees or less at the critical speed. The open-loop transfer function, including the position of the rotating shaft, is, for example, the transfer function of the position-controlled open-loop described above.

[0202] This allows the control device to suppress vibrations of the rotating shaft of the object being supported by magnetic bearings or bearingless motors.

[0203] Furthermore, in a second aspect of this disclosure, based on the first aspect described above, the phase of the open-loop transfer function including the position of the rotation axis may be in the range of -90 degrees or more and 90 degrees or less within the range between two resonant frequencies separated above and below the critical speed as the rotation axis rotates.

[0204] As a result, the control device can appropriately suppress vibrations of the rotating shaft of the object supported by magnetic bearings or bearingless motors in accordance with the rotation of the rotating shaft.

[0205] Furthermore, in a third aspect of this disclosure, based on the first or second aspect described above, the control device may acquire a target value for the current of the coil based on the position information of the rotating shaft and the target position of the rotating shaft, and acquire a first voltage command value for the coil based on the current value of the coil and the target value. The position information of the rotating shaft is, for example, the position detection value of the rotating shaft 250 acquired by the position sensor 800 described above. The first voltage command value is, for example, the voltage command value Vc1 described above. Furthermore, the control device may acquire a second voltage command value based on the position information of the rotating shaft and information regarding the electromagnetic force of the coil. The information regarding the electromagnetic force of the coil is, for example, the current detection value of the coil 412 acquired by the current sensor 900 described above. Furthermore, the information regarding the electromagnetic force of the coil may be the voltage command value Vc3 described above. Furthermore, the information regarding the electromagnetic force of the coil may be an estimated value of the electromagnetic force of the coil 412 calculated based on the position information of the rotation axis 250 and the mass of the rotating body RT including the rotation axis 250, as described above. The second voltage command value is, for example, the voltage command value Vc2 described above. The control device may then control the output voltage based on the first voltage command value and the second voltage command value.

[0206] As a result, the control device can control the position of the rotating shaft based on the first voltage command value, and suppress the natural vibration of the rotating shaft at a higher response speed than the first voltage command value based on the second voltage command value. Therefore, the control device can suppress vibrations of the rotating shaft due to centrifugal force in the rotation frequency range corresponding to the natural frequency of the rotating body including the rotating shaft. Thus, the control device can increase the rotational speed of the rotating shaft to a rotation frequency range higher than the rotation frequency corresponding to the natural frequency.

[0207] Furthermore, in a fourth aspect of this embodiment, based on the third aspect described above, the control device may acquire the natural vibration state of the rotating shaft using a state observer based on information regarding the electromagnetic force of the coil and the position information of the rotating shaft, and output the second voltage command value based on the acquired state. The state observer is, for example, the state observer 731 described above. The natural vibration state of the rotating shaft is, for example, the estimated state x described above. 1e ~x 4e It is at least one of the following.

[0208] As a result, the control device can appropriately suppress vibrations of the rotating shaft caused by centrifugal force at frequencies corresponding to the natural frequency of the rotating body, based on the second voltage command value.

[0209] Furthermore, in a fifth aspect of this embodiment, based on the fourth aspect described above, the control device may acquire the state using the state observer based on the information regarding the electromagnetic force of the coil and the position information of the rotating shaft, taking into account the steady-state deviation of the electromagnetic force of the coil caused by the model error of the controlled object including the magnetic bearing and the rotating shaft. The controlled object including the magnetic bearing and the rotating shaft is, for example, the rotating shaft-magnetic bearing system SYS described above.

[0210] This allows the control device to suppress the decrease in control stability of the vibration suppression control of the rotating shaft that occurs due to model errors in the controlled object.

[0211] Also, in the sixth aspect of the present embodiment, on the premise of any one of the above-described third to fifth aspects, the control device may output a third voltage command value for controlling the output voltage based on the first voltage command value and the second voltage command value. The third voltage command value is, for example, the above-described voltage command value Vc3. Further, the control device may obtain a deviation of the output voltage corresponding to a steady-state deviation between the current value of the coil and the target value by using a disturbance observer based on the third voltage command value and the current value of the coil. The disturbance observer is, for example, the above-described disturbance observer 722. The deviation of the output voltage is, for example, the above-described voltage disturbance. Then, the control device may obtain the first voltage command value based on the deviation between the current value of the coil and the target value and the obtained deviation of the output voltage.

[0212] Thereby, the control device can reduce the gain of the integral element (i.e., the integral controller) in the control element for obtaining the first voltage command value. Therefore, the control device can weaken the responsiveness of the former control with respect to the latter control between the position control of the rotating shaft by the first voltage command value and the vibration suppression control of the rotating shaft by the second voltage command value. As a result, the control device can suppress a situation in which the action of the vibration suppression control of the rotating shaft by the second voltage command value is weakened by the position control of the rotating shaft by the first voltage command value.

[0213] Also, in the seventh aspect of the present embodiment, on the premise of any one of the above-described third to sixth aspects, the control device may obtain a compensation amount for the imbalance of the electromagnetic force of the coil acting on the rotating shaft based on the position information of the coil. The compensation amount for the imbalance of the electromagnetic force of the coil is, for example, the above-described imbalance compensation amount CA. Then, the control device may control the output voltage in consideration of the compensation amount for the imbalance with respect to the second voltage command value.

[0214] As a result, the control device can suppress the influence of the imbalance in the electromagnetic force of the coil acting on the rotating shaft (a phenomenon in which the electromagnetic force of the coil acting on the rotating shaft increases as the distance to the rotating shaft decreases) on the vibration suppression control of the rotating shaft.

[0215] Furthermore, in the eighth aspect of this embodiment, based on any one of the third to seventh aspects described above, the control device may acquire the second voltage command value corresponding to the rotational speed of the rotating shaft based on the position information of the rotating shaft and the information regarding the electromagnetic force of the coil.

[0216] As a result, the control device can appropriately suppress vibrations of the rotating shaft in accordance with the changes in the characteristics of the rotating body, including the rotating shaft, that accompany changes in rotational speed. Therefore, the control device can appropriately suppress the natural vibrations of the rotating body, including the rotating shaft, during the operating section, for example, from the time the rotating shaft is stationary and levitating until it passes the rotational speed corresponding to the first natural frequency.

[0217] Furthermore, in the ninth aspect of this embodiment, assuming any one of the third to eighth aspects described above, the information relating to the electromagnetic force of the coil may be the current value of the coil. The current value of the coil is, for example, the current detection value of the coil 412 obtained by the current sensor 900 described above.

[0218] This allows the control device to obtain a second voltage command value based on the coil current value.

[0219] Furthermore, in the tenth aspect of this embodiment, a third voltage command value for controlling the output voltage may be output based on the first voltage command value and the second voltage command value, assuming any one of the third to ninth aspects described above. The control device may also output the third voltage command value as the information relating to the electromagnetic force of the coil.

[0220] This allows the control device to acquire a second voltage command value based on a third voltage command value corresponding to the output voltage from the power conversion circuit to the coil.

[0221] Furthermore, in the eleventh aspect of this embodiment, based on any one of the third to eighth aspects described above, information regarding the electromagnetic force of the coil may be obtained based on the position information of the rotating shaft and information regarding the mass of the rotating shaft.

[0222] As a result, the control device can obtain, for example, an estimated value of the electromagnetic force acting on the rotating shaft based on the position information of the rotating shaft and information about the mass of the rotating body including the rotating shaft, and obtain a second voltage command value based on that estimated value.

[0223] Furthermore, in the twelfth aspect of this embodiment, the magnetic bearing may be of the heteropolar type, based on any one of the third to eleventh aspects described above. The control device may then control the output voltage of the coil located vertically lower of the two coils located radially opposite to each other, based on the first voltage command value and a fourth voltage command value obtained by inverting the positive and negative values ​​of the second voltage command value. The fourth voltage command value is, for example, the voltage command value Vc4 described above.

[0224] This allows the control device to control the heteropolar magnetic bearing based on a second voltage command value, thereby suppressing vibrations of the rotating shaft.

[0225] Furthermore, in the 13th aspect of this embodiment, the magnetic bearing may be of the homopolar type, based on any one of the third to 11 aspects described above.

[0226] This allows the control device to control the homopolar magnetic bearing based on a second voltage command value, thereby suppressing vibrations of the rotating shaft.

[0227] Furthermore, in the 14th aspect of this embodiment, based on any one of the third to 11 aspects described above, the control device may control the output voltage of the bearingless motor based on the first voltage command value and a fifth voltage command value obtained from the second voltage command value according to the rotation angle of the rotating shaft. The fifth voltage command value is, for example, the voltage command value Vc5 described above.

[0228] This allows the control device to control the bearingless motor and suppress vibrations of the rotating shaft.

[0229] Furthermore, in a 15th aspect of this embodiment, a control device is provided for a magnetic bearing or bearingless motor that includes a coil that generates an electromagnetic force to attract or repel a rotating shaft and supports the rotating shaft in a non-contact manner, by operating a power conversion circuit that outputs power to the coil, thereby controlling the output voltage from the power conversion circuit to the coil. The control device is, for example, the controller 700 described above. The rotating shaft is, for example, the rotating shaft 250 described above. The coil is, for example, the coil 412 described above. The magnetic bearing is, for example, the radial magnetic bearing 400 described above. The bearingless motor is, for example, the bearingless motor 420 described above. The power conversion circuit is, for example, the power conversion circuit 460 described above. Specifically, the amplitude of the open-loop transfer function including the current value of the coil has attenuation characteristics in the frequency band above the critical speed of the rotating shaft. The critical speed of the rotation is, for example, the primary critical speed described above. The open-loop transfer function including the current value of the coil at the critical speed of the rotating shaft is, for example, the current-controlled open-loop transfer function described above. Furthermore, the phase of the open-loop transfer function including the position of the rotation axis is in the range of -90 degrees or more and 90 degrees or less at the critical speed. The open-loop transfer function including the position of the rotation axis is, for example, the position-controlled open-loop transfer function described above. More specifically, the control device acquires a target value for the current of the coil based on the position information of the rotation axis and the target position of the rotation axis, and acquires a first voltage command value for the coil based on the current value of the coil and the target value. The position information of the rotation axis is, for example, the position detection value of the rotation axis 250 acquired by the position sensor 800 described above. The first voltage command value is, for example, the voltage command value Vc1 described above. Furthermore, the control device acquires a second voltage command value based on the position information of the rotation axis and information regarding the electromagnetic force of the coil. The information regarding the electromagnetic force of the coil is, for example, the current detection value of the coil 412 acquired by the current sensor 900 described above. Furthermore, the information regarding the electromagnetic force of the coil may be the voltage command value Vc3 described above. Furthermore, the information relating to the electromagnetic force of the coil may be an estimated value of the electromagnetic force of the coil 412, calculated based on the position information of the rotation axis 250 and the mass of the rotating body RT including the rotation axis 250, as described above.The second voltage command value is, for example, the voltage command value Vc2 described above. The control device also outputs a third voltage command value for controlling the output voltage based on the first voltage command value and the second voltage command value. The third voltage command value is, for example, the voltage command value Vc3 described above. The control device also uses a disturbance observer to obtain the deviation of the output voltage corresponding to the steady-state deviation between the coil current value and the target value, based on the third voltage command value and the coil current value. The disturbance observer is, for example, the disturbance observer 722 described above. The deviation of the output voltage is, for example, the voltage disturbance described above. The control device then obtains the first voltage command value based on the deviation between the coil current value and the target value and the obtained deviation of the output voltage.

[0230] As a result, the control device can suppress vibrations of the rotating shaft of an object supported by magnetic bearings or bearingless motors. Specifically, the control device can control the position of the rotating shaft based on a first voltage command value, and suppress the natural vibration of the rotating shaft at a higher response speed than the first voltage command value based on a second voltage command value. Therefore, the control device can suppress vibrations of the rotating shaft due to centrifugal force in the rotation frequency range corresponding to the natural frequency of the rotating body including the rotating shaft. Thus, the control device can increase the rotational speed of the rotating shaft to a rotation frequency range higher than the rotation frequency corresponding to the natural frequency. Furthermore, the control device can omit the integral element (i.e., integral controller) in the control element for acquiring the first voltage command value. Therefore, the control device can weaken the responsiveness of the first voltage command value to the second voltage command value's vibration suppression control of the rotating shaft. As a result, the control device can prevent situations in which the vibration suppression control of the rotating shaft by the second voltage command value is weakened by the rotation shaft position control by the first voltage command value.

[0231] Furthermore, the control device can implement the second, fourth, fifth, seventh to fourteenth embodiments described above, based on the fifteenth embodiment.

[0232] As a result, the control device exhibits the same operations and effects as those of the second, fourth, fifth, seventh to fourteenth aspects described above.

[0233] Further, in the sixteenth aspect of the present embodiment, a refrigeration device may be provided that includes a compressor including the magnetic bearing or the bearingless motor and a rotating part that rotates integrally with the rotating shaft and compresses a refrigerant, and a control device according to any one of the first to fifteenth aspects described above. The refrigeration device is, for example, the refrigeration device 1 described above. The rotating part is, for example, the impeller 200 described above. The compressor is, for example, the compressor 10 described above.

[0234] As a result, the control device can suppress the vibration of the rotating shaft supported by the magnetic bearing of the compressor mounted on the refrigeration device.

[0235] Further, in the seventeenth aspect of the present embodiment, on the premise of the sixteenth aspect described above, the compressor may be a turbo compressor. And the rotating shaft may rotate at a rotational speed of 1.67 times or more of the first critical speed.

[0236] As a result, the refrigeration device as a turbo refrigerator can suppress the vibration of the rotating shaft when rotating at a rotational speed of 1.67 times or more of the first critical speed.

[0237] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims.

Explanation of Reference Numerals

[0238] 1 Refrigeration device 10 Compressor 20 Heat exchanger 30 Expansion mechanism 40 Heat exchanger [[ID=三十七]] 100 Casing 110 Impeller chamber 111 Diffuser 120 Suction pipe 130 Discharge pipe 140 Electric motor room 200 Impeller 250 Rotation axis 260 Thrust Discs 300 electric motor 310 Rotor 320 Stator 400 Radial Magnetic Bearing 410 Electromagnet 411 Stator Core 412 coil 420 Bearingless Motor 450 power supply 460 Power Conversion Circuit 500 Thrust Magnetic Bearing 510 Electromagnet 600 Touchdown Bearing 700 Controllers 710 Position controller 720 Current Controller 721 Controller 722 Disturbance Observer 723 Voltage Command Output Section 730 Feedback Compensator 731 Status Observer 732 Voltage Command Output Section 732A1 Multiplier 732A2 Multiplier 732A3 Multiplier 732A4 Multiplier 732B Adder 733 Disturbance Observer 734 PD controller 735 Force Estimator 736 Multiplier 737 Phase Filter 738 Multiplier 739 Multiplier 740 Voltage Command Output Section 750 Unbalance Compensator 751 Multiplier 752 multiplier 760 Power Conversion Circuit 800 Position Sensor 900 Current Sensor AX axis center CA unbalance compensation amount K Gain k1~k n gain L1 Refrigerant Path L2 Refrigerant Path L3 Refrigerant Route L4 Refrigerant Route RC refrigerant circuit RT Rotating Body SYS Rotating Shaft / Magnetic Bearing System Vc1 Voltage command value Vc2 Voltage Command Value Vc3 Voltage command value Vc4 Voltage command value Vc5 Voltage command value x state x1~x n situation x 1e ~x ne Estimated state x e Estimated state

Claims

1. A control device for a magnetic bearing (400) or bearingless motor (420) that supports a rotating shaft (250) in a non-contact manner, which includes a coil (412) that generates an electromagnetic force that attracts or repels the rotating shaft (250), by operating a power conversion circuit (460) that outputs power to the coil (412), wherein the power conversion circuit (460) controls the output voltage from the power conversion circuit (460) to the coil (412), The transfer function from the current value of the coil (412) to the output voltage includes an integral element. The amplitude of the open-loop transfer function, including the current value of the coil (412), has attenuation characteristics in the frequency band above the critical speed of the rotating body (RT) including the rotating shaft (250). The phase of the open-loop transfer function, including the position of the rotation axis (250), is in the range of -90 degrees or more and 90 degrees or less at the critical speed. Control device.

2. The phase of the open-loop transfer function, including the position of the rotation axis (250), is in the range of -90 degrees or more and 90 degrees or less within the range between two resonant frequencies separated above and below the critical speed as the rotation axis (250) rotates. The control device according to claim 1.

3. Based on the position information of the rotating shaft (250) and the target position of the rotating shaft (250), the target value of the current of the coil (412) is obtained. Based on the current value of the coil and the target value, a first voltage command value (Vc1) of the coil (412) is obtained. Based on the position information of the rotating shaft (250) and the information regarding the electromagnetic force of the coil (412), a second voltage command value (Vc2) is obtained. Based on the first voltage command value (Vc1) and the second voltage command value (Vc2), the output voltage is controlled. The control device according to claim 1 or 2.

4. Based on information regarding the electromagnetic force of the coil (412) and the position information of the rotating shaft (250), the state observer (731) is used to acquire the natural vibration state of the rotating shaft (250), and based on the acquired state, the second voltage command value (Vc2) is output. The control device according to claim 3.

5. Based on the first voltage command value (Vc1) and the second voltage command value (Vc2), a third voltage command value (Vc3) for controlling the output voltage is output. Based on the third voltage command value (Vc3) and the current value of the coil (412), the disturbance observer (722) is used to obtain the deviation of the output voltage corresponding to the steady-state deviation between the current value of the coil (412) and the target value. Based on the deviation between the current value of the coil (412) and the target value, and the obtained deviation of the output voltage, the first voltage command value (Vc1) is obtained. The control device according to claim 3.

6. The information relating to the electromagnetic force of the coil (412) is the current value of the coil (412). The control device according to claim 3.

7. A control device for a magnetic bearing (400) or bearingless motor (420) that supports a rotating shaft (250) in a non-contact manner, which includes a coil (412) that generates an electromagnetic force that attracts or repels the rotating shaft (250), by operating a power conversion circuit (460) that outputs power to the coil (412), wherein the power conversion circuit (460) controls the output voltage from the power conversion circuit (460) to the coil (412), The amplitude of the open-loop transfer function, including the current value of the coil (412), has attenuation characteristics in the frequency band above the critical speed of the rotating body (RT) including the rotating shaft (250). The phase of the open-loop transfer function, including the position of the rotation axis (250), is in the range of -90 degrees or more and 90 degrees or less at the critical speed. Based on the position information of the rotating shaft (250) and the target position of the rotating shaft (250), the target value of the current of the coil (412) is obtained. Based on the current value of the coil and the target value, a first voltage command value (Vc1) of the coil (412) is obtained. Based on the position information of the rotating shaft (250) and the information regarding the electromagnetic force of the coil (412), a second voltage command value (Vc2) is obtained. Based on the first voltage command value (Vc1) and the second voltage command value (Vc2), a third voltage command value (Vc3) for controlling the output voltage is output. Based on the third voltage command value (Vc3) and the current value of the coil (412), the disturbance observer (722) is used to obtain the deviation of the output voltage corresponding to the steady-state deviation between the current value of the coil (412) and the target value. Based on the deviation between the current value of the coil (412) and the target value, and the obtained deviation of the output voltage, the first voltage command value (Vc1) is obtained. Control device.

8. A compressor (10) includes the rotating shaft (250), the magnetic bearing (400) or the bearingless motor (420), and a rotating part (200) that rotates integrally with the rotating shaft (250) and compresses the refrigerant. A control device (700) according to claim 1, 2, or 7, comprising Refrigeration equipment.

9. The compressor (10) is a turbo compressor, The rotating shaft (250) rotates at a rotational speed of 1.67 times or more the primary critical speed. The refrigeration apparatus according to claim 8.

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