Control device for a bearingless motor, motor system and control method for a bearingless motor

Abstract

A control device (30) for a bearingless motor is provided, the bearingless motor including a rotor and a stator including an electric motor winding that generates torque, the rotor and the stator being arranged with a predetermined gap, the control device being configured to control the bearingless motor, the control device including an observation unit (32) and a speed estimation unit (33).The observation unit (32) calculates an estimated current and / or an estimated rotor magnetic flux based on a voltage command value of the electric motor winding or a voltage detection value, which is a detection value of a voltage applied to the electric motor winding, wherein the estimated current is an estimated value of a current flowing through the bearingless motor, wherein the estimated rotor magnetic flux is an estimated value of a rotor magnetic flux generated in the electric motor winding by the rotor. The speed estimation unit (33) calculates and outputs an estimated axial speed, which is an estimated value of an axial speed of the rotor, in response to an input of a current error and / or the estimated rotor magnetic flux, wherein the current error is a difference between the estimated current and a current detection value, which is a value of a current of the electric motor winding.

Description

Field of InterestThe present disclosure relates to: a control device for a bearingless motor (or a bearingless motor) including a rotor supported in a non-contact manner with respect to the stator by being magnetically floated and rotating; a motor system; and a control method for a bearingless motor.Prior ArtBearingless motors have the function of an electric motor that generates torque and the function of a magnetic bearing that generates a support force for floating the rotor in a contactless manner with respect to the stator, both functions being on the same magnetic circuit. In order to float the rotor, it is necessary to actively control all five degrees of freedom except for the rotation axis or to form a passively stable structure without partially actively controlling the five degrees of freedom.In a bearingless motor of the two-axis control type, a sensor detects a position only in the radial direction, specifically, in two directions of the X-axis and the Y-axis orthogonal to each other, and a support force is set such that the detected position coincides with the target position, thereby actively controlling the two-axis direction. The rotor is generally arranged by being separated from the stator by a radial gap portion. The Z axis, which is the axial direction of the bearingless motor of the two-axis control type and the axis is perpendicular to both the X axis and the Y axis, and the inclination direction (θ x, θ y) are not controlled actively in general and have a passively stable structure. Hereinafter, a direction in which control is performed is referred to as a control direction. On the other hand, a direction that is passively stable without being controlled is referred to as a passive stability direction. In order to achieve passive stability, the attractive force between the permanent magnet of the rotor and the iron core of the stator is used. In one example, when the rotor is displaced in the axial direction, a magnetic flux flows between the permanent magnet of the rotor and the iron core of the stator separated by the radial gap portion to generate a mutual attractive force serving to restore the axial displacement of the rotor. As a result, a restoring force is generated in an orientation opposite to the displacement direction in the axial direction without control. The attractive force acting between the permanent magnet and the iron core is proportional to the distance and thus can be regarded as a spring force. Hereinafter, the ratio of a restoring force [N] to an axial displacement [m] is referred to as a restoring force coefficient k z[ N / m].In the axial direction of the two-axis control type bearingless motor, the stability is secured using only the restoring force generated in the radial gap portion, and thus the stability is poor compared to the control direction. In addition, the restoring force has no function of damping vibrations. A damping force proportional to the rotational speed and having the effect of damping vibrations is not generated in the passive stability direction in principle. For this reason, the vibration in the passive stability direction may maintain stability or diverge and become unstable.Patent Literature 1 proposes a method of performing control of the axial position of the rotor by applying a field current to the winding of teeth, which is the stator facing the rotor, by being separated by a radial gap portion. In the technique described in Patent Literature 1, the rotor and the stator have surface portions that do not face each other in the axial direction, a displacement sensor detects the axial position of the rotor, and a control device generates a field current command for performing control of the axial position of the rotor based on position information detected by the displacement sensor. In the technique described in Patent Literature 1, an axial force is generated in the rotor by a magnetic flux generated by applying a field current to the winding disposed between teeth of the stator protruding toward the rotor and a magnetic flux generated by the permanent magnet.List of InstructionsPatent LiteraturePatent Literature 1: Japanese Patent Application Laid-Open No. 2015-171165Summary of the InventionProblem to be Solved by the InventionControl of the axial position of the rotor requires an axial displacement sensor or a sensor that measures the speed or acceleration from which the displacement can be calculated. Integrating the acceleration results in a speed, and integrating the speed results in a shift. Differentiation of the displacement results in a rotational speed, and differentiation of the rotational speed results in an acceleration. If at least one of the displacement, rotational speed and acceleration can be detected, the remaining physical quantities can also be calculated. In the technique described in Patent Literature 1, a sensor that detects a position using the shaft of the rotor as a sensor target is disposed on the axis end side. In this case, the structure extends in the axial direction by the amount corresponding to the sensor, thereby increasing the volume. In addition, among the two directions in which the shaft extends, on the side where the sensor is provided, the shaft physically interferes with the sensor and is thus difficult to connect to a load such as a fan, which is problematic. Further, in the technique described in Patent Literature 1, the use of the sensor as described above is problematic in terms of cost increase due to the use of the sensor, failure of the sensor, disconnection of a signal line connected to the sensor, or increase of variations or errors in sensor characteristics due to a change in temperature, or the like.The present disclosure has been developed in view of the above, and an object thereof is to provide a control device for a bearingless motor capable of estimating the displacement, rotation speed, or acceleration of the rotor in the axial direction with a simplified structure as compared with the related art.Ways to Solve the ProblemIn order to solve the above-described problems and achieve the object, the present disclosure provides a control device for a bearingless motor, the bearingless motor including a rotor and a stator including an electric motor winding that generates torque, the rotor and the stator being arranged with a predetermined gap, the control device being configured to control the bearingless motor, the control device including an observation unit and a rotation speed estimation unit. The observation unit calculates at least one of an estimated current or an estimated rotor magnetic flux based on a voltage command value of the electric motor winding or a voltage detection value that is a detection value of a voltage applied to the electric motor winding, the estimated current being an estimated value of a current flowing through the bearingless motor, the estimated rotor magnetic flux being an estimated value of a rotor magnetic flux generated in the electric motor winding by the rotor. The rotation speed estimation unit calculates and outputs an estimated axial rotation speed, which is an estimated value of an axial rotation speed of the rotor, in response to an input of at least one of a current error or the estimated rotor magnetic flux, the current error being a difference between the estimated current and a current detection value, which is a value of a current of the electric motor winding.Effects of the InventionThe bearingless motor control device according to the present disclosure can achieve the effect of estimating the displacement, rotational speed, or acceleration of the rotor in the axial direction with a simplified structure compared to the related art.Brief Description of the DrawingsFIG. 1 is a cross-sectional view schematically illustrating an exemplary configuration of a bearingless motor according to the first embodiment. FIG. 2 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the first embodiment. FIG. 3 is a block diagram illustrating an exemplary configuration of the rotational speed estimation unit that outputs the estimated axial rotational speed in response to input of a current error. FIG. 4 is a block diagram illustrating an exemplary configuration of the rotational speed estimation unit that outputs the estimated axial rotational speed in response to input of a current error. FIG. 5 is a block diagram illustrating an exemplary configuration of the rotational speed estimation unit that outputs the estimated axial rotational speed in response to input of a current error. FIG. 6 is a block diagram illustrating an exemplary configuration of the rotational speed estimation unit that outputs the estimated axial rotational speed in response to input of a current error. FIG. 7 is a block diagram illustrating an exemplary configuration of the rotational speed estimation unit that outputs the estimated axial rotational speed in response to input of a current error. FIG. 8 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the second embodiment. FIG. 9 is a block diagram illustrating an exemplary configuration of the d-axis current command value generation unit in the bearingless motor control device according to the third embodiment. FIG. 10 is a block diagram illustrating an exemplary configuration of the d-axis current command value generation unit in the bearingless motor control device according to the third embodiment. FIG. 11 is a block diagram illustrating an exemplary configuration of the rotation speed estimation unit of the bearingless motor control device according to the fourth embodiment. FIG. 12 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the fourth embodiment. FIG. 13 is a block diagram illustrating an exemplary configuration of the rotation speed estimation unit used in the bearingless motor control device according to the fourth embodiment. FIG. 14 is a block diagram illustrating an exemplary configuration of the rotation speed estimation unit used in the bearingless motor control device according to the fourth embodiment. FIG. 15 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the fifth embodiment. FIG. 16 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the sixth embodiment. FIG. 17 is a block diagram illustrating an exemplary configuration of hardware for implementing the storage-less motor control device according to the first to sixth embodiments.DESCRIPTION OF EMBODIMENTSHereinafter, a bearingless motor (or a bearingless motor) control device, a motor system, and a bearingless motor control method according to embodiments of the present disclosure will be described in detail with reference to the drawings.In the following embodiments, a character indicating a vector is written as "character (vector)", and a character indicating a matrix is written as "character (matrix)". In addition, a character written with a symbol thereon in a mathematical formula is written as "character (symbol thereon)" in the sentence. In one example, a character having "^" is written thereon as "Character^".First Embodiment.FIG. 1 is a cross-sectional view schematically illustrating an exemplary configuration of a bearingless motor according to the first embodiment. Here, the axial direction of a rotor 20 is defined as the z-axis, and two axes perpendicular to each other in a plane perpendicular to the z-axis are defined as the x-axis and the y-axis. FIG. 1 illustrates a zx cross section of a bearingless motor 1. the bearingless motor 1 includes a stator 10 and the rotor 20.The stator 10 includes a stator iron core 11, an electric motor winding 12, and a support winding 13. The central axis CA is the center of rotation of the rotor 20 in the bearingless motor 1, and is a virtual straight line passing through the center of the rotor 20 in one example. The central axis CA is an example of a rotation axis. Hereinafter, the extending direction of the central axis CA is also referred to as the axial direction. FIG. 1 illustrates a case where the central axis CA is oriented in the vertical direction. The electric motor winding 12 is a winding for rotation provided in a slot of the stator iron core 11 and rotates the rotor 20, that is, generates torque. The support winding 13 is a magnetic levitation winding provided in a slot of the stator iron core 11.The rotor 20 includes a shaft 21 and a permanent magnet 22. The shaft 21 has a rotation axis which is the z axis. The diameter of the shaft 21 in the direction perpendicular to the z-axis is smaller than the inner diameter of the stator iron core 11. the permanent magnet 22 is disposed on the outer periphery of the shaft 21. The permanent magnet 22 may be fixed to the shaft 21 with magnetic force or may be fixed with a fixing member such as an adhesive. Although FIG. 1 illustrates the bearingless motor 1 of the surface permanent magnet (SPM) type in which the permanent magnet 22 is integrated on the surface of the shaft 21, the bearingless motor 1 may be of the internal permanent magnet (IPM) type in which the permanent magnet 22 is integrated in the iron core of the shaft 21. The stator 10 and the rotor 20 are arranged with a predetermined gap. In this example, the rotor 20 is provided inside the cylindrical stator 10 with a predetermined gap from the inner periphery of the stator 10.When a current flows through the electric motor winding 12 of the stator 10, a magnetic flux of p poles is generated and torque occurs. When a current flows through the support winding 13 of the stator 10, a magnetic flux of p±2 or two poles is generated and a support force occurs in the radial direction. In the case of a general bearingless motor including a surface permanent magnet type bearingless motor or the like, the support force is generated by the magnetic field of p±2 poles through the support winding 13, and in the case of a subsequent pole type bearingless motor or a homopolar type bearingless motor, the support force is generated by the magnetic field of two poles through the support winding 13.At least a part of the magnetic circuit of the magnetic flux of p poles for generating torque and the magnetic circuit of the magnetic flux of p±2 or two poles for generating support force is divided. At least a part of the magnetic circuits is shared, and the magnetic flux of p±2 or two poles is superimposed on the magnetic flux of p poles, whereby irregularity in the magnetic flux density occurs. Therefore, the magnitude and orientation of the support force in the radial direction can be controlled by adjusting the magnitude and phase of the support current.In view that the gravitational acceleration is g and the mass of the rotor 20 is m, an own weight mg always acts downward on the rotor 20. When the rotor 20 is present on the lower side in the axial direction, i.e., on the negative direction side of the z-axis, a restoring force F z acts upward in the axial direction from the stator 10. Then, the rotor 20 floats at a position where the own weight mg and the restoring force F z are balanced. For this reason, as illustrated in FIG. 1, in the arrangement in which the z-axis is oriented in the vertical direction, the rotor 20 has a balanced position at the position shifted downward from the magnetic center in the axial direction, that is, the position of z=0. On the other hand, when the rotor 20 is displaced toward the upper side in the axial direction, i.e., toward the positive direction side of the z-axis, the restoring force F z is directed downward, which corresponds to the own weight.Although not illustrated, a fan or the like may be mounted on the rotor 20. At this time, the reaction associated with the circulation of air or the like by the fan acts in the axial direction of the rotor 20, which also changes the axially balanced position of the rotor 20, which reaction occurs even when the axial direction of the rotor 20 is the horizontal direction. Thus, even when the center axis CA of the rotor 20 is located along the horizontal direction, the balanced position may deviate from the magnetic center in the axial direction.Although FIG. 1 illustrates the inner rotor type bearingless motor 1 in which the rotor 20 is located inside the stator 10, a similar phenomenon also occurs in the outer rotor type in which the rotor 20 is located outside the stator 10, and the technology of the embodiments described below may be applied to the outer rotor type bearingless motor 1.FIG. 2 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the first embodiment. Here, with respect to the bearingless motor 1, as a plant 40 to be controlled, an observation unit 32 to which a voltage is input and a rotation speed estimation unit 33 that outputs an estimated axial rotation speed in response to the input of a current fault are illustrated. A thin line in the drawing represents a scalar and a thick line represents a vector which also applies to the following block diagrams.The bearingless motor 1 illustrated in FIG. 1 is controlled by a control device 30 illustrated in FIG. 2. The control device 30 includes a current controller 31, the observation unit 32, and the rotation speed estimation unit 33.The current controller 31 outputs a voltage command value v s* ( vector), i.e., a command value of the voltage to be applied to the electric motor winding 12, so that a current detection value detected by a current detection unit (not illustrated) that detects a current i s( vector) flowing through the electric motor winding 12 of the bearingless motor 1, i.e., the plant 40, matches the current command values i d* and i q* for the electric motor winding 12 of the stator 10. In the example of FIG. 2, the voltage command value v d in the d-axis direction and the voltage command value v q in the q-axis direction are output such that the deviation between the d-axis current command value i d*, which is the current command value in the d-axis direction, and a d-axis current i d, which is the output of the plant 40 and the value of the current in the d-axis direction, and the deviation between the q-axis current command value i q*, which is the current command value in the q-axis direction, and a q-axis current i q, which is the output of the plant 40 and the value of the current in the q-axis direction, each become zero. Here, subscript s represents stator 10. subscript d represents the d-axis and subscript q represents the q-axis. The raised * represents a command value. The voltage v s( vector) input to the observation unit 32 in FIG. 2 may be a voltage detection value or a voltage command value. The voltage detection value represents the value of the voltage applied to the electric motor winding 12 of the stator 10 and detected by a sensor such as a voltage sensor, but a voltage command value may be used without a sensor. In FIG. 2, both the voltage detection value and the voltage command value are simply referred to as v s( vector) without the raised *. The same applies to the other embodiments and drawings for describing the other embodiments.Based on the voltage command value v s* ( vector), the observation unit 32 calculates an estimated current i s ^ (vector) which is an estimated value of the current flowing through the bearingless motor 1 and / or an estimated rotor magnetic flux Φ r ^ (vector) which is an estimated value of a rotor magnetic flux Φ r( vector) generated in the electric motor winding 12 by the rotor 10. In the first embodiment, the observation unit 32 is a calculation model that calculates an estimated value of a state variable of the bearingless motor 1, i.e., the plant 40, in response to an input of the voltage command value v s* ( vector) output from the current controller 31, and estimates the current flowing through the electric motor winding 12 of the bearingless motor 1. That is, the observation unit 32 is a calculation model that reproduces the operation of the bearingless motor 1. Thus, the output of the observation unit 32 and the values of current, magnetic flux, and the like that are held as state variables can be calculated and estimated without a detection unit. Moreover, it is also possible to compare an estimated value with a detected value to obtain the difference or the like by calculation. However, the observation unit 32 performs estimation and calculation on the assumption that the rotor 20 of the bearingless motor 1 does not move in the axial direction. The current flowing through the electric motor winding 12 estimated by the observation unit 32 is referred to as the estimated current i s ^ (vector), and a hat "^" is attached thereto. The observation unit 32 outputs a current error Δi s( vector) that is a difference between the estimated current i s ^ (vector) and the current detection value i s( vector) detected by the current detection unit.the rotational speed estimating unit 33 estimates the axial rotational speed of the rotor 20 in response to the input of the current error Δ i s (vector) and / or the estimated rotor magnetic flux Φ r ^ (vector) obtained from a value calculated by the observing unit 32. The axial rotation speed estimated by the rotation speed estimating unit 33 is referred to as an estimated axial rotation speed d|z^| / dt.The position z of the rotor 20 in the axial direction is calculated from the equation of motion of the rotor 20 in the axial direction. This is shown in FIG. 2 as a model 41 for axial movement. The equation of motion of the rotor 20 in the axial direction is expressed by the below formulas (1) and (2). Formula 1:The ratio of the restoring force to the displacement is stiffness. The rigidity is a constant value k z0, in a case where the current is not controlled, but it is possible to increase or decrease the rigidity by applying the d-axis current i d. In other words, it is possible to increase or decrease the attractive force generated between the stator iron core 11 and the permanent magnet 22 of the rotor 20. Here, k zi is a ratio at which the rigidity changes due to the d-axis current i d and the rigidity at the time of energization k z0+ k zi i is d.The plant 40 to be controlled is the bearingless motor 1. the input is the voltage v s( vector) = [v d v q]T and the output is the current i s( vector) = [i d i q]T. T here represents reaction.Moreover, a variable that is between the input and the output of the plant 40 and represents a state is referred to as a state variable. The state variables include an armature reaction magnetic flux Φ s( vector)=[Φ ds Φqs] T and the rotor magnetic flux Φ r( vector)=[Φ dr Φ qr]T. Here, subscript r stands for rotor 20.As expressed by Formula (3) below, the armature reaction magnetic flux Φ s( vector) and the current i s( vector) observed in the electric motor winding 12 of the stator 10 are in a proportional relationship. Therefore, the current i s( vector) observed in the electric motor winding 12 can be used as a state variable instead of the armature reaction magnetic flux Φ s( vector), in which case only some elements of the matrix constituting the state equation to be described later are multiplied by a constant of 1 / L based on the following formula (3), and the core of the equation does not change at all. Formula 2:The current i s( vector) observed in the electric motor winding 12 of the stator 10 and has three phases, U phase, V phase, and W phase, and can be converted into a current on the rotation dq axis by uvw-dq conversion. The equation for converting the detection values for U-phase, V-phase and W-phase currents i u, i v and i w into the d-axis current i d and the q-axis current i q is expressed by Formula (4) below. Here, Φ is the angle of the rotation dq axis with respect to the stationary coordinate, that is, the rotation angle. Formula 3: Formula 3:In a case where the true rotation angle Φ is unknown, the conversion may be performed using an estimated rotation angle Φ^ which is an estimated value of the rotation angle. In a case where the U-phase, V-phase, and W-phase currents i u, i v and i w are converted into the d-axis current i d and the q-axis current i q with the estimated rotation angle Φ^, the formula (5) below is used. Here, the value on the left side is the current value on the estimated d-axis and the estimated q-axis. Formula 4: Formula 4: Formula 4:In FIG. 2, the current i is s( vector) output from the plant 40 which is converted into a current on the dq axis, i.e., i s( vector)=[i d i q]T is illustrated. Thus, in FIG. 2, illustration of blocks for converting a three-phase current to a dq axis is omitted.As described above, the current i is s( vector)=[i d i q]T, which is the output of the plant 40, and the deviation between the d-axis current command value i d* and the q-axis current command value i q* is calculated and input to the current controller 31. The deviation between the d-axis current i d and the d-axis current command value i d* is performed by a current value deviation calculation unit 34 d, and the deviation between the q-axis current i q and the q-axis current command value i q* is performed by a current value deviation calculation unit 34 q. Then, the current controller 31 outputs the voltage command value v s* ( vector)=[v d* v q*]T such that the deviation becomes zero.The inverter applies a voltage according to the voltage command value v s* ( vector) to the equipment 40. Actually, a voltage is applied to each of the windings of the U phase, the V phase, and the W phase, but in FIG. 2, the illustration of the uvw-dq conversion block is omitted and a dq coordinate value is shown as it is. In FIG. 2, the illustration of the inverter is also omitted.The observation unit 32 is configured to calculate the estimated armature reaction magnetic flux Φ s ^ (vector) and the estimated rotor magnetic flux Φ r ^ (vector) which are estimated values of state variables of the plant 40 in response to an input of the voltage v s( vector) applied to the stator 10, and estimate, output, and reproduce the current i s( vector) flowing through the electric motor winding 12 of the stator 10. The observation unit 32 calculates the current error Δi s( vector) according to the following formula (6). Formula 5: Formula 5:As described above, the rotation speed estimation unit 33 receives an input of the current error Δi s( vector) and estimates the estimated axial rotation speed d|z^| / dt of the rotor 20.The voltage input to the observation unit 32 may be the voltage command value v s* ( vector) or the voltage detection value v s( vector). In a case where the voltage command value v s* ( vector) is input, a voltage sensor is unnecessary and the structure can be simplified. In a case where the voltage detection value v s( vector) is input, the influence of the error between the voltage command value v s* ( vector) and the voltage detection value v s( vector) due to the dead time or the like can be eliminated.In this way, the estimated axial rotational speed d|z^| / dt of the rotor 20 can be estimated without providing a displacement sensor, a rotational speed sensor, or an acceleration sensor that detects the axial position of the rotor 20. As described above, it is also possible to estimate the remaining physical quantities by calculation, namely, displacement by integration and acceleration by differentiation, based on the estimated rotational speed. In addition, the configuration of inputting the voltage command value v s* ( vector) to the observation unit 32 may make a voltage sensor unnecessary. In this case, the only necessary sensor is a current sensor. Thus, it is not necessary to newly provide hardware such as a sensor required for estimating the axial displacement, rotational speed, or acceleration.Here, the processing in the rotation speed estimation unit 33 will be described. The observation unit 32 performs estimation on the assumption that the rotor 20 of the bearingless motor 1 does not move in the axial direction, and the rotation speed estimation unit 33 obtains the estimated axial rotation speed d|z^| / dt from the relational expression between the current error Δi s( vector) and the axial rotation speed d|z| / dt, where the current error Δi s( vector) is the difference between the estimated current i s ^ (vector) obtained from the observation unit 32 and the current i s( vector) of the equipment 40 including the influence of the axial rotation speed d|z| / dt. Details of the calculation of the estimated axial rotational speed d|z^| / dt will be described below. The state equation and the output equation of the plant 40 are expressed by the formulas (7) and (8), respectively, below. Formula 6: Formula 7:Here, in Fig. 2, the matrices in the formulas (7) and (8) are defined as A' (matrix), B (matrix) and C (matrix) as in the formulas (9), (10) and (11) below. Formula 8: Formula 9: Formula 10:The variables used in the formulas (7) to (11) are as follows. Φ s( vector)=[Φ ds Φqs] T armature reaction magnetic flux Φ r( vector)=[Φ dr Φ qr]T rotor magnetic flux R stator resistance L inductance v s( vector)=[v d v q]T voltage input to plant 40 i s( vector)=[idiq]Tcurrent output from plant 40 ω1angle frequency of the current supply ω r Rotational angular velocity (electrical angle) of the rotor 20Here, the inductance L is expressed by L on the assumption that the d-axis inductance L d and the q-axis inductance L q are the same. The two can be distinguished by the fact that L in the first row and the first column of A' (matrix) in formula (9) is marked with L d and L in the second row and the second column with L q. In addition, it is considered that the rotor magnetic flux Φ r( vector) changes when the rotor 20 is displaced in the axial direction, and k represents the reciprocal of the ratio of the change in the rotor magnetic flux Φ r( vector) to the axial displacement.The state equation and the output equation of the observation unit 32 are set as in Formulas (12) and (13) below, respectively. Formula (12) is expressed using an estimated rotational angular velocity ω r ^ if the rotational angular velocity ω r of the rotor 20 cannot be detected. Formula 11: Formula 12:Here, in Fig. 2, the matrices in the formulas (12) and (13) are defined as A^ (matrix) and H (matrix) as in the formulas (14) and (15) below. Formula 13: Formula 14:When the rotational angular velocity ω r can be detected, the detected rotational angular velocity ω r can be used. A (matrix) using the rotational angular velocity ω r of the rotor 20 in the first row and the fourth column, the second row and the third column, the third row and the fourth column, and the fourth row and the third column of A^ (matrix) in Formula (14) is hereinafter expressed as Formula (16). Formula 15:In the formulas (12) and (13), the following variables are used. Note that H (matrix) indicated by formula (15) represents the feedback gain. Φ s ^(vector)= [Φ ds ^ Φqs^] T estimated armature reaction magnetic flux Φ r ^(vector)= [Φ dr ^ Φ qr ^] T estimated rotor magnetic flux i s ^(vector)= [i d ^ i q ^]Testimated currentIn formulas (14) and (16), the first row and third column, the second row and fourth column, the third row and third column, and the fourth row and fourth column are set to zero in A^ (matrix). This is because the observation unit 32 performs estimation on the assumption that the rotor 20 of the bearingless motor 1 does not move in the axial direction, unlike the equipment 40.Here, when the above formulas are transformed and organized, the below formula (17) indicating the current error Δi s( vector) can be obtained. Formula 16:Here, s represents the time derivative d / dt, and the raised "-1" represents the inverse matrix. In formula (17), instead of using A^ (matrix) and A' (matrix), A (matrix), the rotational angular velocity error Δω r and the estimated axial rotational speed d|z| / dt are used. Moreover, the matrices and variables used in formula (17) are as follows. I 4( matrix) 4x4 unit matrix I (matrix) 2x2 unit matrix Formula 17: Δω r= ω r ^-ω r Rotational angular velocity error Formula 18:When the d-axis among dq axes to be controlled substantially coincides with the orientation of the N pole of the permanent magnet 22 of the rotor 20, the values of the rotor magnetic flux Φ qr in the q-axis direction and the estimated rotor magnetic flux Φ qr ^ in the q-axis direction may be approximately zero. In this case, formula (17) can be simplified to formula (18) below. Formula 19:As a result, the axial rotation speed d|z| / dt can be estimated depending on Δi d / Φ dr or Δi q / Φ dr and the result of the estimation can be output as the estimated axial rotation speed d|z^| / dt. Thus, the rotation speed estimation unit 33 can calculate and output the estimated axial rotation speed d|z^| / dt using the formula (18).The current error Δi s( vector) depends on the estimated rotor magnetic flux Φ dr ^ in the d-axis direction and the rotor magnetic flux Φ dr in the d-axis direction, and these values are theoretically necessary. Here, the estimated rotor magnetic flux Φ dr ^ in the d-axis direction may be used instead of the rotor magnetic flux Φ dr in the d-axis direction. Alternatively, a rotor magnetic flux constant that is a representative constant of the rotor magnetic flux Φ r( vector) may be obtained in advance and used instead of the rotor magnetic flux Φ dr in the d-axis direction, and the estimated rotor magnetic flux Φ dr ^ in the d-axis direction that fluctuates during operation may not be used.Accordingly, since the current error Δi s( vector) on the left side of the formula (17) or (18) includes information on the axial rotational speed d|z| / dt on the right side, a relational expression between these two values can thus be clarified. Therefore, it is easy to design a gain coefficient for estimating the axial rotational speed d|z| / dt from the current error Δi s( Vector).With respect to the estimated axial rotation speed estimation d|z^| / dt, the estimated axial rotation speed d|z^| / dt is estimated by the rotation speed estimation unit 33 using the current error Δi s( Vector) without treating the estimated axial rotation speed d|z^| / dt as a state variable. Therefore, the size of the array of the equipment 40 and the observation unit 32 does not increase. Thus, the number of state variables may be maintained at four and A (matrix) may be maintained at 4×4. Thus, the amount of calculation in the observation unit 32 is not increased. Accordingly, estimating the estimated axial rotation speed d|z^| / dt at the rotation speed estimating unit 33 causes the calculation load to be able to be reduced and the adjustment to be facilitated.A control method for controlling the bearingless motor 1 including the rotor 20 and the stator 10 including the electric motor winding 12 that generates torque includes an observing step and a speed estimating step. In the observation step, the observation unit 32 calculates at least one of the estimated current i s ^ (vector), i.e., an estimated value of the current flowing through the bearingless motor 1, or the estimated rotor magnetic flux Φ r ^ (vector), which is an estimated value of the rotor magnetic flux generated in the electric motor winding 12 by the rotor 10, based on the voltage command values v d* and v q*, which are output, so that the current detection values i d and i q, which are the values of the current of the electric motor winding 12, The voltage detection values v d and V q, which are the detection values of the voltage applied to the electric motor winding 12, are the same as the current command values i d* and i q* respectively. In the rotation speed estimation step, the rotation speed estimation unit 33 estimates and outputs the estimated axial rotation speed d|z^| / dt, which is an estimated value of the axial rotation speed of the rotor 20, in response to an input of at least one of the current error Δi s( vector), the difference between the estimated current i s ^ (vector), and the current detection value i s( vector), or the estimated rotor magnetic flux Φ r ^ (vector).In a case where the voltage detection values v d and v q are not used, the control method for the bearingless motor 1 includes a current detection step and a voltage command value output step. In the current detection step, the current detection unit of the bearingless motor 1 detects the current of the motor winding 12. In the voltage command value output step, the current controller 31 outputs the voltage command values v d* and v q* such that the current detection values i d and i q, which are the values of the current detected by the motor winding 12, coincide with the current command values i d* and i q* respectively. The output voltage command values v d* and v q* are used in the observation step. Note that even in a case where the voltage detection values are used, the current detection step and the voltage command value output step may also be included.Next, an exemplary configuration of the rotation speed estimation unit 33 will be described. The estimated current i s ^ (vector) and the current detection value i s( vector) input to the rotation speed estimation unit 33 are those converted into d-q axes which are biaxial rotation coordinates. The rotation speed estimating unit 33 outputs the estimated axial rotation speed d|z^| / dt based on at least one of a value obtained by multiplying the d-axis current error Δi d by a predetermined first coefficient or a value obtained by multiplying the q-axis current error Δi d by a predetermined second coefficient.FIGS. 3 to 7 are block diagrams illustrating exemplary configurations of the rotational speed estimation unit that outputs the estimated axial rotational speed in response to input of a current error. FIG. 3 illustrates the rotation speed estimation unit 33 in the case of using only the d-axis current error Δi d among the current error Δi s( vector)=[Δi d Δi q]T. The rotation speed estimation unit 33 in this case includes a calculation unit 331 aand a proportional (P) controller 332 a. That is, the calculation unit 331 adividates the d-axis current error Δi d by the estimated rotor magnetic flux Φ dr ^ in the d-axis direction, and the P controller 332 amultiplies the calculation result from the calculation unit 331 awith a P gain K P1 which is the first coefficient for outputting the estimated axial rotational speed d|z^| / dt.FIG. 4 illustrates the rotation speed estimation unit 33 in the case of using only the q-axis current error Δi q among the current error Δi s( vector)=[Δi d Δi q]T. The rotation speed estimation unit 33 in this case includes a calculation unit 331 band a P controller 332 b. That is, the calculation unit 331 bdividles the q-axis current error Δi g by the estimated rotor magnetic flux Φ dr ^ in the d-axis direction, and the P controller 332 bmultiplies the calculation result from the calculation unit 331 bwith a P gain K P2 which is the second coefficient for outputting the estimated axial rotation speed d|z^| / dt.FIG. 5 illustrates the rotation speed estimation unit 33 in the case of using both components of the current error Δi s( vector)=[Δi d Δi q]T. The rotation speed estimation unit 33 in this case includes a calculation unit 331 cand a P controller 332 c. That is, the calculation unit 331 cdivists the current error Δi s( vector) by the estimated rotor magnetic flux Φ dr ^ in the d-axis direction, and the P controller 332 ccalculates the inner product of the calculation result from the calculation unit 331 cand the P gain matrix [K P1 K P2] and outputs the estimated axial rotation speed d|z^| / dt. Note that the inner product of the calculation result and the P gain matrix is calculated as in Formula (19) below.Inner product of the calculation result and P gain matrix=K P1* ( Δi d / Φ dr ^)+K P2* ( Δi q / Φ dr ^)... (19)Note that FIGS. 3 and 4 correspond to the case where one of the P gain matrix [K P1 K P2] is set to zero. Thus, the rotation speed estimation unit 33 illustrated in FIGS. 3 and 4 corresponds to a specific case in the rotation speed estimation unit 33 in FIG. 5, and the rotation speed estimation unit 33 illustrated in FIG. 5 includes the rotation speed estimation unit 33 in FIGS. 3 and 4.The speed estimating unit 33 illustrated in FIG. 6 further includes a high pass filter that excludes only DC and low frequency components as compared to the speed estimating unit 33 in FIG. 5. FIG. 6 illustrates a case where the high pass filter is a direct current (DC) cut-off high pass filter (HPF) 333. Important for the frequency components of the current error Δi s( vector) is the component of the axial vibration frequency of the rotor 20, and the DC component is unnecessary. If a DC component is present in the current error Δi s( vector), the DC component also remains at the estimated axial rotational speed d|z^| / dt. Therefore, the DC blocking HPF 333 removes the DC component. In one example, the DC blocking HPF 333 having a cut-off frequency of 1 Hz is used to exclude the DC component.FIG. 7 illustrates the rotation speed estimation unit 33 in the case of using the current error Δi s( vector) as an input but without performing division by the estimated rotor magnetic flux Φ dr ^ in the d-axis direction. The rotation speed estimation unit 33 includes a P controller 332 din this case. The P controller 332 dcalculates the inner product of the input current error Δi s( vector) and the P gain matrix [K P1 K P2] and outputs the estimated axial rotational speed d|z^| / dt. In this case, the calculation corresponding to the division by the estimated rotor magnetic flux Φ dr ^ in the d-axis direction is applied in advance to the P gain matrix [K P1 K P2] as a constant. As a result, the division calculation during operation is avoided, so that the calculation load is reduced, and a possibility that the output becomes unstable due to the division by a value close to zero can be avoided.As described above, in order to calculate the estimated axial rotation speed d|z^| / dt, P controllers 332 ato 332 dmay be used, which are calculations for multiplying the current error Δi s( vector) by a coefficient. Normally, in order to estimate the rotational speed from displacement information, derivative (D) control is required for difference calculation. However, the difference calculation amplifies a high frequency, and thus there is a problem that noise including a frequency higher than the frequency component of a necessary signal is amplified. However, in the first embodiment, the P controllers 332 ato 332 dare used instead of the D controllers, and thus it is possible to prevent amplification of noise including a frequency higher than the frequency component of a necessary signal.The rotational speed estimating unit 33 illustrated in FIGS. 3 to 7 sets the coordinate center of the axial position of the rotor 20, that is, z=0, as the center position magnetically facing the stator 10, and outputs the estimated axial rotational speed d|z^| / dt corresponding to a value obtained by time-differentiating the absolute value of the axial position. This configuration makes it possible to estimate the rotational speed after determining whether the rotor 20 is away from or nears the axial center. When a displacement sensor that detects the position of the rotor 20 is used, a signal corresponding to z=0 needs to be obtained in advance, and post-processing for changing the sign using this value as a boundary needs to be performed. However, the rotation speed estimation unit 33 used in the control device 30 for the bearingless motor 1 according to the first embodiment may directly obtain the estimated axial rotation speed d|z^| / dt without post-processing. Therefore, setting for obtaining a signal corresponding to z=0 is unnecessary in advance.As described above, the control device 30 for the bearingless motor 1 according to the first embodiment controls the bearingless motor 1 including the rotor 20 and the stator 10 including the electric motor winding 12 that generates torque. The control device 30 for the bearingless motor 1 includes the observation unit 32 and the rotation speed estimation unit 33. the observation unit 32 calculates at least one of the estimated current i s ^ (vector) or the estimated rotor magnetic flux Φ r ^ (vector) of the bearingless motor 1 based on the voltage command value v s* ( vector) output so that the current detection value i s( vector) which is the value of the current of the motor winding 12 coincides with the current command values i d* and i q* or based on the voltage detection value which is the detection value of the voltage applied to the motor winding 12. The rotation speed estimation unit 33 calculates the estimated axial rotation speed d|z^| / dt of the rotor 20 in response to an input of at least one of the current error Δi s( vector) which is the difference between the estimated current i s* ( vector) and the current detection value i s( vector) or the estimated rotor magnetic flux Φ r ^ (vector). The position of the rotor 20 in the axial direction can be obtained using the estimated axial rotational speed d|z^| / dt, and a sensor for detecting the axial displacement, rotational speed, or acceleration of the rotor 20 is unnecessary. Thus, as compared with a conventional bearingless motor including a sensor that detects the axial displacement, rotational speed, or acceleration of the rotor 20, there is an effect that the axial displacement, rotational speed, or acceleration of the rotor 20 can be estimated with a simplified structure.Second Embodiment.In the first embodiment, both the armature reaction magnetic flux φ s( vector) or the current i s( vector) and the rotor magnetic flux φ r( vector) are used as state variables. However, the state variables may be reduced. In the second embodiment, the control device 30 for the bearingless motor 1 capable of calculating the estimated axial rotation speed d|z^| / dt with reduced state variables will be described.FIG. 8 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the second embodiment. Here, since the state variable is only the current, with respect to the bearingless motor 1 as the equipment 40 to be controlled, the observation unit 32A to which the voltage v s is input and the rotation speed estimation unit 33 that outputs the estimated axial rotation speed d|z^| / dt in response to the input of the current error Δi s( Vector) are illustrated.The control device 30A for the bearingless motor 1 according to the second embodiment includes the current controller 31, the observation unit 32A, and the rotation speed estimation unit 33. The second embodiment is different from the first embodiment in that the observation unit 32A calculates the estimated current i s ^ (vector))=[i d ^ i q ^] T using the state variable that is the current i s( vector). Note that components identical to those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.A method of calculating the estimated axial rotation speed d|z^| / dt using the current error Δi s( vector) as an input will be described. Since the state variable is only the current i s( vector)=[i d i q]T the state equation and the output equation of the plant 40 are expressed by the formulas (20) and (21) below, respectively. Formula 20: Formula 21:Here, Δθ is a rotation angle error which is a deviation of the estimated rotation angle θ^ from the rotation angle θ and is represented by θ^-θ, and Φ m is a rotor magnetic flux constant.When the rotation angle error Δθ is close to zero assuming that approximations for cosΔ≈1and sinΘ≈Δ are valid, the state equation of Formula (20) can also be expressed as Formula (22) below. Formula 22:On the other hand, the state equation and the output equation of the observation unit 32A are set as in the below formulas (23) and (24). Formula 23: Formula 24:Here, in Fig. 8, the matrices in the formulas (22) and (23) are defined as H 2( matrix), A 2( matrix), E' (matrix) and E^ (matrix) as in the formulas (25) to (28) below. Note that H 2( matrix) is a matrix indicating the feedback gain. Formula 25: Formula 26: Formula 27: Formula 28:Here, when the above formulas are transformed and organized, the below formula (29) indicating the current error Δi s( vector) can be obtained. Formula 29:Here, when Δθ, |z| / k, and (1 / k)*d|z| / dt values are close to zero, since Δθ*|z| / k, and Δθ*(1 / k)*d|z| / dt are very small, the fact that these values are negligible compared with the other terms is used.The current error Δi s( vector) on the left side of the formula (29) includes a component related to d|z| / dt of the first term on the right side and a component related to the rotation angle error Δθ of the second term. Therefore, the estimated axial rotation speed d|z^| / dt and the estimated rotation angle θ^ can be estimated based on the current error Δi s( vector).In the second embodiment, the state variable representing the state of the plant 40 is set only to the current i s (vector) observed in the electric motor winding 12 of the stator 10, that is, the d-axis current i d and the q-axis current i q, and a relational expression is formed between the current error Δi s( vector) and the axial rotational speed d|z| / dt and the rotational angle θ. Then, the estimated axial rotation speed d|z^| / dt and the estimated rotation angle θ^ are calculated from this relational expression. In this way, by setting two state variables, an effect is obtained that the calculation amount can be reduced as compared with the case of setting four state variables.Third Embodiment.In the third embodiment, the control devices 30 and 30A for the bearingless motor 1 further include a d-axis current command value generation unit that generates the d-axis current command value i d*. The d-axis current command value generation unit generates the d-axis current command value i d* using the estimated axial rotation speed d|z^| / dt output from the rotation speed estimation unit 33, and outputs the d-axis current command value i d* to the current controller 31.FIG. 9 is a block diagram illustrating an exemplary configuration of the d-axis current command value generation unit in the bearingless motor control device according to the third embodiment. The d-axis current command value generation unit 35 receives an input of the estimated axial rotation speed d|z^| / dt from the rotation speed estimation unit 33, and outputs the d-axis current command value i d*. The d-axis current command value generation unit 35 includes an axial position controller 351, a zero value output unit 352, and a switch 353. The axial position controller 351 outputs the d-axis current command value i d* from the estimated axial rotational speed d|z^| / dt. The zero value output unit 352 outputs zero as the d-axis current command value i d*. The switch 353 selects one of the output of the axial position controller 351 or the output from the zero value output unit 352, and outputs the selected output as the d-axis current command value i d*. The zero value output unit 352 is used when the d-axis current command value i d* can be set to zero. In FIG. 9, the axial position controller 351 is configured to output the d-axis current command value i d* in response to an input of the estimated axial rotation speed d|z^| / dt to enable adjustment of the d-axis current.The d-axis current command value generation unit 35 may be configured to issue a command for a positive d-axis current when the estimated axial rotation speed d|z^| / dt is a positive value and issue a command for a negative d-axis current when the estimated axial rotation speed d|z^| / dt is a negative value. A representative controller that outputs such a command is a P controller. FIG. 10 is a block diagram illustrating an exemplary configuration of the d-axis current command value generation unit in the bearingless motor control device according to the third embodiment. FIG. 10 illustrates a case where a P controller 351 ais used as the axial position controller 351. The P gain of the P controller 351 ais denoted by K P5. By setting K P5 to a positive value, the signs of the input and the output can be adjusted.The axial position controller 351 is not limited to the P controller 351 athat makes the output simply proportional to the input. An sgn function (sign function) which is a function that outputs 1 when the value of the input is positive and -1 when the value of the input is negative may be used, or the sgn function may be used in combination with the P controller 351 a. Further, a limiting unit may be applied to the value of the input. Further, a third power value of the input may be used.Applying the P controller 351 ato the axial position controller 351 assumes that a condition that the d-axis current i d is K P5- times the estimated axial rotation speed d|z^| / dt and the estimated axial rotation speed d|z^| / dt is equal to the axial rotation speed d|z| / dt is satisfied. At this time, the equation of motion in the axial direction is as in formula (30) below. Formula 30:Here, where z≥0, the formula (31) below applies and k zi K p5 z>0 is valid. Here, z<0 applies the formula (32) below and k zi K p5(- z)>0 is valid. Formula 31: Formula 32:As described above, a force proportional to the axial rotational speed d|z| / dt and may be generated at an orientation opposite to the direction of the rotational speed. This corresponds to a damping force that weakens vibrations. Thus, by generating the d-axis current command value i d* from the estimated axial rotation speed d|z^| / dt output from the rotation speed estimation unit 33, it is possible to generate a damping force that weakens vibrations when the rotor 20 vibrates in the axial direction.In the third embodiment, the control amount for the bearingless motor 1 includes the d-axis current command value generation unit 35 that outputs the d-axis current command value i d* in response to an input of the estimated axial rotation speed d|z^| / dt, or the d-axis current command value generation unit 35 that issues a command of the positive d-axis current command value i d* when the estimated axial rotation speed d|z^| / dt is a positive value and issues a command of the negative d-axis current command value i d* when the estimated axial rotation speed d|z^| / dt is a negative value. Consequently, the d-axis current i d of the electric motor winding 12 can be increased or decreased according to the axial vibration of the rotor 20. As a result, an axial attractive force can be generated between the stator 10 and the rotor 20, so that axial vibrations of the rotor 20 are mitigated. In addition, this control for which a device such as a magnetic thrust bearing is not newly added achieves an effect that the structure is compact and the stability in the axial direction to be the original passive stability direction of the two-axis control type bearingless motor 1 can be improved without increasing the cost.Fourth Embodiment.FIG. 11 is a block diagram illustrating an exemplary configuration of the rotation speed estimation unit of the bearingless motor control device according to the fourth embodiment. In the fourth embodiment, the rotation speed estimation unit 33 receives an input of the current error Δi s( vector), and outputs the estimated axial rotation speed d|z^| / dt and the estimated rotational angular velocity ω r ^. In formula (17) representing the current error Δi s( vector) described in the first embodiment, the first term on the right side represents the rotational angular velocity error Δω r and the second term on the right side represents the axial rotational speed d|z| / dt. Thus, the current error Δi s( vector) includes information of both the rotational angular velocity error Δω r and the axial rotational speed d|z| / dt. Therefore, not only the axial rotation speed d|z| / dt but also the rotational angular velocity ω r can be estimated from the current error Δi s( Vector).FIG. 12 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the fourth embodiment. Note that components identical to those described in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The control device 30B for the bearingless motor 1 in FIG. 12 illustrates a case where the estimated rotational angular velocity ω r ^ estimated by the rotation speed estimation unit 33 is used by the observation unit 32. That is, the observation unit 32 does not use the signal of the rotational angular velocity sensor, and uses the value of the estimated rotational angular velocity ω r ^ output from the rotation speed estimation unit 33 instead of the rotational angular velocity ω r.Next, an exemplary configuration of the rotation speed estimation unit 33 used in the fourth embodiment will be described. FIG. 13 is a block diagram illustrating an exemplary configuration of the rotation speed estimation unit used in the bearingless motor control device according to the fourth embodiment. The rotation speed estimation unit 33 includes a calculation unit 331 c, a P controller 332 c, and a PI controller 334. That is, the calculation unit 331 cdividues the current error Δi s( vector) by the estimated rotor magnetic flux Φ dr ^ in the d-axis direction. The calculation unit 331 coutputs the result of division to the P controller 332 cand the PI controller 334. The processing in the P controller 332 cis similar to that described in FIG. 5 of the first embodiment, and thus the description thereof is omitted.The PI controller 334 calculates the inner product of the calculation result from the calculation unit 331 cand the PI gain matrix [K P3+ K I3 / s K P4+ K I4 / s], and outputs an estimated rotational angular velocity ω r ^. The PI controller 334 also performs integration calculation. A term, such as K I3 / s, of the PI gain matrix corresponds to the integration calculation. That is, 1 / s in this term represents the integration calculation, and K I3 and K I4 represent gains of the integration. The PI controller 334 amplifies the DC component and reports it back. When the DC component of the current error Δi s( vector) is not zero, the estimated rotational angular velocity ω r ^ changes, and the estimated rotational angular velocity ω r ^ approximates the rotational angular velocity ω r. At the same time, the DC component of the current error Δi s( vector) approaches zero to establish a steady state. Therefore, it is possible to make the estimated rotational angular velocity ω r ^ equal to the rotational angular velocity ω r.In order to merge the rotational angular velocity error Δω r from DC components to low frequency components of Δω r, which are included in the current error Δi s( vector), are important. In order to converge the axial rotational speed d|z| / dt, from center frequency components to high frequency components near the natural angular frequency in the axial direction corresponding to the variation of the axial rotational speed d|z| / dt and included in the current error Δi s( vector) are important. Therefore, information on the rotational angular velocity ω r can be extracted by amplifying the DC component of the current error Δi s( Vector), and information on the axial rotation speed d|z| / dt can be extracted by non-amplifying the DC component. Thus, the rotational angular velocity ω r and the axial rotational speed d|z| / dt can be separately fed back.FIG. 14 is a block diagram illustrating an exemplary configuration of the rotation speed estimation unit used in the bearingless motor control device according to the fourth embodiment. Note that components identical to those in FIG. 13 are denoted by the same reference numerals, and the description thereof is omitted. The speed estimating unit 33 illustrated in FIG. 14 further includes the DC blocking HPF 333, which is a high pass filter that excludes only DC and low frequency components and is disposed in the subsequent stage of the P controller 332 cin FIG. 13. By adding the DC blocking HPF 333 to the estimated axial rotation speed detection block d|z^| / dt in this manner, the DC component can be excluded from the estimated axial rotation speed d|z^| / dt, and the rotational angular velocity ω r and the axial rotation speed d|z| / dt can be accurately separated and estimated.In the fourth embodiment, the rotation speed estimation unit 33 outputs the estimated axial rotation speed d|z^| / dt and the estimated rotation angular speed ω r ^ from the current error Δi s( vector). Thus, not only the estimated axial rotational speed d|z^| / dt of the rotor 20, but also the angle of the rotor 20 can be simultaneously estimated from the current error Δi s( Vector). By estimating the angle of the rotor 20 from the current, it is possible to perform the rotation control and the levitation control of the bearingless motor 1 without using the signal of the angle sensor. As a result, it is possible to solve the problem that the noise of the angle sensor generated during the operation of the bearingless motor 1 including the angle sensor affects the control. In addition, it is possible to avoid a change in characteristics of the angle sensor due to a phase delay of an angle sensor signal low-pass filter (LPF) used for noise countermeasures and excluding a high frequency component, a temperature change, and the like, and it is possible to avoid a problem occurring in a detection signal from the angle sensor, such as disconnection of a signal line. Further, from the same input of the current error Δi s( vector), the estimated rotational angular velocity ω r ^ can be estimated by amplifying the DC component, and the estimated axial rotational speed d|z^| / dt can be estimated by not amplifying the DC component. Thus, the estimated rotational angular velocity ω r ^ and the estimated axial rotational speed d|z^| / dt can be simultaneously separated and fed back.Fifth Embodiment.In the first embodiment, both the armature reaction magnetic flux φ s( vector) or the current i s( vector) and the rotor magnetic flux φ r( vector) are used as state variables. However, it is also possible to use only the rotor magnetic flux Φ r( vector) as the state variable. In the fifth embodiment, the control device 30 for the bearingless motor 1 capable of calculating the estimated axial rotation speed d|z^| / dt with the reduced state variable being only the rotor magnetic flux Φ r( vector) will be described.FIG. 15 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the fifth embodiment. Here, since the state variable is only the rotor magnetic flux Φ r( vector) concerning the bearingless motor 1 as the equipment 40 to be controlled, FIG. 15 illustrates the observation unit 32 to which the voltage v s( vector) is input and the rotation speed estimation unit 33 that outputs the estimated axial rotation speed d|z^| / dt in response to the input of the rotor magnetic flux error. In the control device 30C for the bearingless motor 1 in FIG. 15, components identical to those in the first embodiment are denoted by the same reference numerals.A method of calculating the estimated axial rotational speed d|z^| / dt will be described. In view that the state variable is only the rotor magnetic flux Φ r( vector), the state equation of the plant 40 is expressed by the below formulas (33) and (34). Formula 33: Formula 34:Next, the observation unit 32 is constructed as in the following formula (35). Formula 35:Here, in FIG. 15, determinants in formula (35) are defined as A 2' ( matrix) and F (matrix) as in formulae (36) and (37) below. Formula 36: Formula 37:The right side of Formula (35) does not include the rotor magnetic flux Φ r( vector) that is difficult to directly measure, and all the values included in Formula (35) are known values or values calculated during operation. Therefore, the estimated rotor magnetic flux [Φ dr ^ Φ qr ^] T can be calculated using this formula. Here, the right side of F (matrix) in formula (37) is converted into formula (38) below. Formula 38:With Φ qr ≈0, Φ qr ^≈0, and Φ dr ≈Φ dr ^, Formula (38) becomes Formula (39) below. Formula 39:Therefore, after constructing the observation unit 32 so that [Φ dr ^ Φ qr ^] T can be calculated, it is possible to construct the rotation speed estimation unit 33 that receives an input of F (matrix) expressed by Formula (37), which is a function including the estimated rotor magnetic flux [Φ dr ^ Φ qr ^] T. By using F (matrix) as an input, the value of the estimated axial rotational speed d|z^| / dt can be estimated, and the value of the rotational angular velocity error Δω r= ω r ^-ω r can be estimated.In the fifth embodiment, the state variable representing the state of the plant 40 is only the rotor magnetic flux Φ r( vector), and the function including the axial rotation speed d|z| / dt and the rotation angular velocity error Δω r is input to the rotation speed estimation unit 33. Consequently, as in the second embodiment, since the two state variables are used, the calculation amount can be reduced as compared with the case of four state variables. In addition, a difference calculation for estimating the estimated axial rotational speed d|z^| / dt can be omitted.Sixth Embodiment.In examples described in the first to fifth embodiments, the control device 30 for the bearingless motor 1 includes the rotation speed estimation unit 33 that calculates and outputs the estimated axial rotation speed, i.e., an estimated value of the axial rotation speed of the rotor 20, in response to an input of at least one of the current error Δi s( vector), i.e., the difference between the estimated current i s ^ (vector) and the current detection value i s( vector) or the estimated rotor magnetic flux Φ r ^ (vector). However, the d-axis current command value i d* may be directly calculated from at least one of the current error Δi s( vector) or the estimated rotor magnetic flux Φ r ^ (vector) without calculating the estimated axial rotational speed d|z^| / dt as an intermediate variable.FIG. 16 is a block diagram illustrating an exemplary configuration of the bearingless motor control device according to the sixth embodiment. Note that components identical to those described in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. The control device 30D for the bearingless motor 1 in FIG. 16 includes an axial position controller 36 instead of the rotational speed estimation unit 33. the axial position controller 36 calculates and outputs the d-axis current command value i d* for controlling the axial position of the rotor 20 from at least one of the current error Δi s( vector) or the estimated rotor magnetic flux Φ r ^ (vector) obtained from a value calculated by the observation unit 32. The axial position controller 36 outputs the calculated d-axis current command value i d* to the current value deviation calculation unit 34 d.Although FIG. 16 illustrates the case where the control device 30 for the bearingless motor 1 in the first embodiment includes the axial position controller 36 instead of the rotation speed estimation unit 33, the control devices 30A, 30B, and 30C for the bearingless motor 1 in the second to fifth embodiments may include the axial position controller 36 instead of the rotation speed estimation unit 33.The control device 30 for the bearingless motor 1 in the sixth embodiment includes the axial position controller 36 that calculates the d-axis current command value i d* from at least one of the current error Δi s( vector) or the estimated rotor magnetic flux Φ r ^ (vector), and outputs the d-axis current command value i d*. Consequently, the d-axis current command value i d*, which corresponds to the axial displacement, rotational speed, or acceleration of the rotor 20, can be directly calculated.FIG. 17 is a block diagram illustrating an exemplary configuration of hardware for implementing the storage-less motor control device according to the first to sixth embodiments. FIG. 17 is an exemplary configuration in the case where the current controller 31, the observation units 32 and 32A, the rotation speed estimation unit 33, the axial position controller 36, and the d-axis current command value generation unit 35 that are main parts of the control devices 30, 30A, 30B, 30C, and 30D for the bearingless motor 1 are implemented by the processing circuit 61 including a processor 63 and a memory 64.The processor 63 is a central processing unit (CPU). The processor 63 executes a control program. The control program is a program describing the processing for operating the processing circuit 61 as the current controller 31, the observation units 32 and 32A, the rotation speed estimation unit 33, the axial position controller 36, and the d-axis current command value generation unit 35 that are main parts of the control devices 30, 30A, 30B, 30C, and 30D for the bearingless motor 1.The memory 64 is, in one example, volatile or nonvolatile memory such as a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable ROM (EPROM), or an electrically erasable programmable ROM (EEPROM). The memory 64 stores a control program. The memory 64 is also used as a temporary memory when the processor 63 executes various processes.An input unit 62 is a circuit that receives input signals from the outside to the control devices 30, 30A, 30B, 30C, and 30D. An output unit 65 is a circuit that outputs signals generated by the control devices 30, 30A, 30B, 30C, and 30D to the outside of the control devices 30, 30A, 30B, 30C, and 30D.The function of the processing circuit 61 may be implemented by a processing circuit that is dedicated hardware. The processing circuit, which is dedicated hardware, is, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a circuit that is a combination thereof. A part of the main parts of the control devices 30, 30A, 30B, 30C, and 30D for the bearingless motor 1 may be implemented by the processor 63 and the memory 64, and the rest may be implemented by dedicated hardware.The configurations described in the above-mentioned embodiments indicate examples. The embodiments may be combined with another well-known technique and with each other, and some of the configurations may be omitted or changed in a range not deviating from the spirit.List of reference characters1 Bearingless motor; 10 Stator; 11 Stator iron core; 12 Electric motor winding; 13 Support winding; 20 Rotor; 21 Shaft; 22 Permanent magnet; 30, 30A, 30B, 30C, 30D Control device; 31 Current controller; 32, 32A Observation unit; 33 Angular velocity estimation unit; 34d, 34q Current value deviation calculation unit; 35 d-axis current value command value generation unit; 36, 351 Axial position controller; 40 Plant; 41 Axial movement model; 61 Processing circuit; 62 Input unit; 63 Processor; 64 Memory; 65 Output unit; 331a, 331b, 331c Calculation unit; 332a, 332b, 332c, 332d, 351a P controller; 333 DC lock HPF; 334 PI controller; 352 Zero value output unit; 353 Switch.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedJP 2015-171165

[0006]

Claims

A control device for a bearingless motor, the bearingless motor including a rotor and a stator including an electric motor winding that generates torque, the rotor and the stator being arranged with a predetermined gap, the control device being configured to control the bearingless motor, the control device comprising: an observation unit for calculating at least one of an estimated current or an estimated rotor magnetic flux based on a voltage command value of the electric motor winding or a voltage detection value that is a detection value of a voltage applied to the electric motor winding, the estimated current being an estimated value of a current flowing through the bearingless motor, the estimated rotor magnetic flux being an estimated value of a rotor magnetic flux generated in the electric motor winding by the rotor; and a rotation speed estimating unit for calculating and outputting an estimated axial rotation speed, which is an estimated value of an axial rotation speed of the rotor, in response to an input of at least one of a current error or the estimated rotor magnetic flux, wherein the current error is a difference between the estimated current and a current detection value, which is a value of a current of the electric motor winding.The control device for the bearingless motor according to claim 1, wherein the estimated current and the current detection value are those converted into d-q axes which are biaxial rotation coordinates, and the rotation speed estimation unit outputs the estimated axial rotation speed based on at least one of a value obtained by multiplying the d-axis current error by a predetermined first coefficient or a value obtained by multiplying the q-axis current error by a predetermined second coefficient.The control device for the bearingless motor according to claim 1, wherein the rotation speed estimating unit sets a coordinate center of an axial position of the rotor as a center position magnetically facing the stator, and outputs the estimated axial rotation speed corresponding to a value obtained by time-differentiating an absolute value of the axial position.The control device for the bearingless motor according to claim 2, further comprising a current command value generation unit for outputting a command value of a current in the d-axis in response to an input of the estimated axial rotational speed.The control device for the bearingless motor according to claim 4, wherein the current command value generation unit outputs a command value of a positive current in the d-axis when the estimated axial rotation speed is a positive value and outputs a command value of a negative current in the d-axis when the estimated axial rotation speed is a negative value.The control device for the bearingless motor according to claim 1 or 2, wherein the observation unit performs estimation on the assumption that the rotor of the bearingless motor does not move in the axial direction, and the rotation speed estimation unit obtains an axial rotation speed from a relational expression between a current error and an axial rotation speed, the current error being a difference between an estimated current obtained by the observation unit and a current of a plant including the influence of the axial rotation speed.The control device for the bearingless motor according to claim 1, wherein the rotation speed estimation unit outputs the estimated axial rotation speed in response to an input of at least one of the current error or the estimated rotor magnetic flux, and outputs an estimated rotation angular velocity that is an estimated value of a rotation angular velocity of the rotor in response to an input of at least one of the current error or the estimated rotor magnetic flux.A control device for a bearingless motor, the bearingless motor including a rotor and a stator including an electric motor winding that generates torque, the rotor and the stator being arranged with a predetermined gap, the control device being configured to control the bearingless motor, the control device comprising: an observation unit for calculating at least one of an estimated current or an estimated rotor magnetic flux based on a voltage command value of the electric motor winding or a voltage detection value that is a detection value of a voltage applied to the electric motor winding, the estimated current being an estimated value of a current flowing through the bearingless motor, the estimated rotor magnetic flux being an estimated value of a rotor magnetic flux generated in the electric motor winding by the rotor; and an axial position controller for outputting a d-axis current command value for controlling an axial position of the rotor in response to an input of at least one of a current error or the estimated rotor magnetic flux, wherein the current error is a difference between the estimated current and a current detection value that is a value of a current of the electric motor winding.The control device for the bearingless motor according to any one of claims 1 to 8, further comprising: in a case where the voltage command value is used: a current detection unit for detecting a current of the electric motor winding; and a current controller for outputting the voltage command value so that the current detection value detected by the current detection unit matches the current command value.A motor system comprising: a bearingless motor including a rotor and a stator including an electric motor winding that generates torque, the rotor and the stator being arranged with a predetermined gap; and a bearingless motor control device for controlling the bearingless motor, the bearingless motor control device including: an observation unit for calculating at least one of an estimated current or an estimated rotor magnetic flux based on a voltage command value of the electric motor winding or a voltage detection value that is a detection value of a voltage applied to the electric motor winding, the estimated current being an estimated value of a current flowing through the bearingless motor, the estimated rotor magnetic flux being an estimated value of a rotor magnetic flux generated in the electric motor winding by the rotor; and a rotation speed estimating unit for calculating and outputting an estimated axial rotation speed, which is an estimated value of an axial rotation speed of the rotor, in response to an input of at least one of a current error or the estimated rotor magnetic flux, wherein the current error is a difference between the estimated current and a current detection value, which is a value of a current of the electric motor winding.A control method for a bearingless motor, the bearingless motor including a rotor and a stator including an electric motor winding that generates torque, the rotor and the stator being arranged with a predetermined gap, the control method for controlling the bearingless motor, the control method comprising: an observing step of calculating at least one of an estimated current or an estimated rotor magnetic flux based on a voltage command value of the electric motor winding or a voltage detection value that is a detection value of a voltage applied to the electric motor winding, the estimated current being an estimated value of a current flowing through the bearingless motor, the estimated rotor magnetic flux being an estimated value of a rotor magnetic flux generated in the electric motor winding by the rotor; and a rotation speed estimating step of estimating and outputting an estimated axial rotation speed, which is an estimated value of an axial rotation speed of the rotor, in response to an input of at least one of a current error or the estimated rotor magnetic flux, wherein the current error is a difference between the estimated current and a current detection value, which is a value of a current of the electric motor winding.

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