DESCRIPTION MOTOR CONTROL DEVICE AND ELEVATOR IN WHICH SAME IS USED
TECHNICAL FIELD
[0001] The present invention relates to a motor control device for a three-phase AC electric motor or the like, and an elevator using the same.
BACKGROUND ART
[0002] AC motors, in particular, PM motors (Permanent Magnet Synchronous Motors) have characteristics of small size and high efficiency, and in recent years, have been widely used for industrial devices and the like.
[0003] However, in PM motors, harmonic components are contained in induced voltage because of the structure thereof, and therefore have torque ripple which is disturbance oscillating with components having orders that are integer multiples (mainly, six times) of a motor electric angle
(hereinafter, the component having the sixth order is referred to as 6f component) with respect to generated torque. The torque ripple can cause problems such as vibration, noise, and mechanical resonance. Therefore, technology for reducing the torque ripple (hereinafter, referred to as torque ripple suppression control) is needed.
[0004] In order to perform the torque ripple suppression

control, it is necessary to acquire information corresponding to torque ripple which is a control target. Methods therefor are roughly classified into a feedforward method (hereinafter, referred to as FF method) in which information is acquired in advance through examination, analysis, or the like and then stored in a control device, and a feedback method (hereinafter, referred to as FB method) in which information is acquired online during driving of a motor. [0005] The former FF method has an advantage of enabling torque ripple suppression with high response, but has a disadvantage that a complicated work for acquiring torque ripple information in advance is needed and the torque ripple information acquired in advance becomes inappropriate due to aging of a motor or a device.
The latter FB method has an advantage that it is not necessary to perform such a complicated work for acquiring torque ripple information in advance and it is possible to perform torque ripple suppression control appropriately in accordance with aging of a motor or a device, but has a disadvantage that response of torque ripple suppression cannot be made higher than the torque ripple frequency and also there is a high technical barrier for acquiring information corresponding to torque ripple online. [0006] Considering the above, a learning control method using these two methods in combination is proposed (see, for

example, Patent Document 1 below). That is, when operation is performed online by the FB method, the present torque ripple suppression command value is stored, and when high response is needed, operation is performed by the FF method using the stored suppression command value. Alternatively, operation is basically performed by the FF method, and during a steady operation, the suppression command value is updated by the FB method.
CITATION LIST
PATENT DOCUMENT
[0007] Patent Document 1: Japanese Patent No. 5434369
SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION
[0008] Thus, in the learning method, switching between the FF method and the FB method is appropriately performed, whereby torque ripple suppression control can be performed while combining advantages of both methods. However, if the switching timing is not appropriate, a wrong suppression command value is learned. Therefore, setting of an operation sequence for managing the switching timing is important. This is particularly significant in the case where transfer characteristics of torque ripple cannot be grasped correctly, e.g., case where torque ripple is estimated from electric

information on the basis of a motor parameter for the purpose of system simplification.
[0009] For the torque ripple suppression control, it is necessary to estimate the 6f component information online. However, in an RL circuit model in a rotating coordinate system (dq coordinate system) often used in general, such estimation can become extremely difficult.
[0010] FIG. 15 shows an example of variation in a q-axis magnetic flux cpq when q-axis current iq is increased while a PM motor is controlled at a constant speed. The slope in this graph is a q-axis inductance. Here, the following two points become problems.
[0011] (i) Variation in a fundamental wave component of the inductance: the inductance varies in accordance with current due to magnetic saturation of the motor
(ii) Variation in a harmonic component of the inductance: the inductance forms a hysteresis minor loop
Here, the hysteresis minor loop means that, in an enlarged view in FIG. 15, the q-axis magnetic flux cpq can have a plurality of values with respect to the same q-axis current iq and thus the q-axis magnetic flux cpq varies so as to form a small loop.
[0012] Regarding the above (i), as the current increases, the inductance is saturated to decrease. Thus, error occurs between the circuit model of a motor recognized by a

controller and that of an actual motor, resulting in a problem that the transfer characteristics of torque are different.
[0013] Regarding the above (ii), even under the same current, the value of the inductance differs depending on the rotor position. Therefore, as in torque ripple, the inductance has harmonic components according to the motor electric angle, and thus forms a hysteresis minor loop. In the case of having such characteristics, even if the setting is made such that the inductance varies in accordance with the current in consideration of magnetic saturation characteristics, the inductance as seen on a coordinate system of harmonic is to vary in accordance with the rotor position. That is, even if the transfer characteristics of torque is correct, the transfer characteristics of torque ripple are different, and therefore it is difficult to acquire accurate information about torque ripple. [0014] The present invention has been made to solve the above problems, and an object of the present invention is to provide: a motor control device capable of performing torque ripple suppression control with high accuracy by appropriately managing an operation sequence when performing the torque ripple suppression control in accordance with variations in the motor speed and magnetic characteristics; and an elevator using the motor control device.

SOLUTION TO THE PROBLEMS
[0015] A motor control device according to the present invention includes: an AC motor; a current detection unit which detects at least currents for two phases among three phases; a current control unit which generates voltage command values on control coordinate axes, using detected current values; a torque estimation unit which estimates torque of the AC motor on the basis of the voltage command values and the current detection values; a torque ripple suppression unit which generates a suppression command for suppressing torque ripple of the AC motor, on the basis of estimation torque; and a suppression control parameter storage unit which stores a suppression control parameter for generating the suppression command, in association with a current command value and a speed of the AC motor. The motor control device further includes a control unit which executes an operation sequence of selecting, in accordance with a switching condition calculated from magnetic characteristics of the AC motor, one of three control modes of: an online control mode in which torque ripple suppression is performed by the torque ripple suppression unit; a learning control mode in which torque ripple suppression is performed by the torque ripple suppression unit and at the same time, the suppression control parameter storage unit stores the

suppression control parameter; and an offline control mode in which torque ripple suppression is performed using the suppression control parameter stored in the suppression control parameter storage unit.
An elevator according to the present invention includes: the motor control device having the above configuration; a car; a balance weight; a rope connecting the car and the balance weight; and a drive sheave which is rotated by a drive force of the AC motor and on which the rope is wound.
EFFECT OF THE INVENTION
[0016] The motor control device according to the present invention and the elevator using the same are configured to execute an operation sequence of selecting one of the three control modes of the online control mode, the learning control mode, and the offline control mode in accordance with a switching condition based on magnetic characteristics of the AC motor. Thus, it becomes possible to appropriately perform learning of suppression control parameters, whereby torque ripple can be effectively suppressed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] [FIG. 1] FIG. 1 is a block diagram showing the
configuration of a motor control device according to

embodiment 1 of the present invention.
[FIG. 2] FIG. 2 is a block diagram showing an example of the configuration of a torque ripple compensation command generation unit in the motor control device according to embodiment 1 of the present invention.
[FIG. 3] FIG. 3 is a block diagram showing operation in an online control mode of the motor control device according to embodiment 1 of the present invention.
[FIG. 4] FIG. 4 is a block diagram showing operation in a learning control mode of the motor control device according to embodiment 1 of the present invention.
[FIG. 5] FIG. 5 is a block diagram showing operation in an offline control mode of the motor control device according to embodiment 1 of the present invention.
[FIG. 6] FIG. 6 is a flowchart showing an operation sequence for switching the control mode of the motor control device according to embodiment 1 of the present invention.
[FIG. 7] FIG. 7 is a graph schematically showing the operation sequence for switching the control mode of the motor control device according to embodiment 1 of the present invention.
[FIG. 8] FIG. 8 is a graph schematically showing another operation sequence for switching the control mode of the motor control device according to embodiment 1 of the

present invention.
[FIG. 9] FIG. 9 is a graph schematically showing still another operation sequence for switching the control mode of the motor control device according to embodiment 1 of the present invention.
[FIG. 10] FIG. 10 is a block diagram showing the configuration of a motor control device according to embodiment 2 of the present invention.
[FIG. 11] FIG. 11 is a block diagram showing operation in an online control mode of the motor control device according to embodiment 2 of the present invention.
[FIG. 12] FIG. 12 is a block diagram showing operation in a learning control mode of the motor control device according to embodiment 2 of the present invention.
[FIG. 13] FIG. 13 is a block diagram showing operation in an offline control mode of the motor control device according to embodiment 2 of the present invention.
[FIG. 14] FIG. 14 is a flowchart showing an operation sequence for switching the control mode of a motor control device according to embodiment 4 of the present invention.
[FIG. 15] FIG. 15 is a characteristics graph showing an example of magnetic saturation characteristics of an AC motor.
[FIG. 16] FIG. 16 is a schematic configuration

diagram according to embodiment 5 in which the motor control device of the present invention is applied to an elevator.
[FIG. 17] FIG. 17 is a flowchart showing an operation sequence for switching the control mode of the motor control device provided to the elevator according to embodiment 5 of the present invention.
DESCRIPTION OF EMBODIMENTS [0018] . Embodiment 1
FIG. 1 is a block diagram showing the configuration of a motor control device according to embodiment 1 of the present invention.
[0019] The motor control device of the present embodiment 1 controls a PM motor (hereinafter, simply referred to as a motor) 9 which is an AC motor, via a power converter 3. The motor control device includes: a current command generation unit 10 which outputs current command values i*d, i*q on the basis of a torque command value i*; subtracters 6, 7 which subtract outputs of a three phase-dq converter 5 from output of the current command generation unit 10; a current control unit 1 which generates voltage command values v*d, v*q on control coordinate axes, using outputs of the subtractors 6, 7; a dq-three phase converter 2 which generates three-phase AC voltage on the basis of the voltage command values v*d, v*q from the current control unit 1; the power converter 3 which

controls power supplied to the motor 9, on the basis of output of the dq-three phase converter 2; a current detection unit 4 which detects at least currents for two phases among three-phase currents supplied to the motor 9; a rotational position detector 8 such as an encoder which detects the rotational position of the motor 9; and the three phase-dq converter 5 which converts the detected currents obtained by the current detection unit 4 to d-axis current id and q-axis current iq on control coordinate axes.
[0020] Further, the motor control device of the present embodiment 1 includes: a torque ripple suppression unit 8 0 which generates a suppression command for torque ripple suppression for the motor 9; a suppression control parameter storage unit 120 which stores a suppression control parameter for torque ripple suppression in association with the current command value and the speed of the motor 9; and a control unit 150 such as a microcomputer which controls the torque ripple suppression unit 80 and the suppression control parameter storage unit 120.
[0021] The torque ripple suppression unit 80 includes: a torque estimation unit 90 which calculates a torque estimation value x of the motor 9 on the basis of a voltage command value v dq, a current detection value i dq, and a rotational position 9re of the motor 9; and a torque ripple compensation command generation unit 100 which generates a

torque ripple compensation signal i*rip as the suppression command for suppressing torque ripple of the motor 9, on the basis of the rotational position 9re of the motor 9 and the torque estimation value T from the torque estimation unit 90, and outputs the torque ripple compensation signal T*rip to the current command generation unit 10.
[0022] The control unit 150 controls operations of the torque ripple suppression unit 80 and the suppression control parameter storage unit 120, and executes an operation sequence of selecting, in accordance with switching conditions {are_iovir core_highr iq_mg/ iq hys described later) set on the basis of the speed of the motor 9 and the magnetic characteristics (inductance characteristics shown above in FIG. 15) of the motor 9, one of three control modes of: an online suppression control mode in which torque ripple suppression is performed by the torque ripple suppression unit 8 0; a learning control mode in which torque ripple suppression is performed by the torque ripple suppression unit 80 and at the same time, the suppression control parameter storage unit 120 stores the suppression control parameter; and an offline control mode in which torque ripple suppression is performed using the suppression control parameter stored in the suppression control parameter storage unit 120. [0023] FIG. 2 is a block diagram showing an example of the

configuration of the torque ripple compensation command generation unit 100 described above. The configurations and operations of the parts shown in FIG. 1 and FIG. 2 will be further clarified through the operation explanation below.
[0024] Next, operation in the online control mode in which power of the motor 9 is estimated from voltage and current supplied to the motor 9 and torque ripple is suppressed on the basis of the estimated power, in the motor control device having the above configuration, will be described with reference to FIG. 3.
[0025] The torque estimation unit 90 estimates an induced voltage estimation value vector edq as estimated induced voltage of the motor 9 by calculation of the following expression (1) on the basis of a motor constant, an actual current vector idq composed of d-axis, q-axis actual currents iq, id, a voltage vector v dq composed of voltage command values v*d, v*q for the motor 9, and the electric angle 9re of the motor detected by the rotational position detector 8.
[0026] [Mathematical 1]

[0027] Here, R is a winding resistance of the motor, L is a self-inductance, Pm is the number of pole pairs, s is a

differential operator, urm is a mechanical-angle speed, and Qre is the speed (electric angle speed) of the motor 9.
[0028] Further, the torque estimation unit 90 estimates torque of the motor 9 by the following expression (2) on the basis of the induced voltage estimation value vector edq obtained by the above expression (1) and the actual current vector idq, and outputs this torque estimation value i to the torque ripple compensation command generation unit 100.
[0029] [Mathematical 2]

[0030] The torque ripple compensation command generation unit 100 extracts an oscillation component contained in the torque estimation value i and generates the torque ripple compensation signal i*riP so as to cancel the oscillation, and outputs the torque ripple compensation signal x*riP to the current command generation unit 10. As a method for generating the torque ripple compensation signal x*riP on the basis of the torque estimation value i, many techniques are known. Here, as an example, the torque ripple compensation command generation unit 100 having the configuration shown in FIG. 2 is employed.
[0031] In FIG. 2, first, an extraction unit 101a composing a processing unit 101 extracts a pulsation component

contained in the torque estimation value i. As a method for this calculation, any known technique can be used. For example, calculation of the following expression (3) based on Fourier series expansion with respect to the torque estimation value i can be used. [0032] [Mathematical 3]

[0033] Here, TCn is a cosine coefficient of the torque estimation value i, iSn is a sine coefficient of the torque estimation value x, FLPF(s) is a gain of a low-pass filter, n is the order of torque ripple, and A9est is a phase compensation setting value for compensating estimation delay of the torque estimation value i from actual torque, and is set in a phase compensation unit 101b composing the processing unit 101. It is noted that the compensation setting value A9est in this case is set in advance by being actually measured or calculated from a model.
[0034] Next, the cosine coefficient iCn and the sine coefficient iSn obtained in the processing unit 101 are inputted to subtractors 102a, 103a, respectively. The subtracters 102a, 103a and the suppression control units 102b, 103b perform calculation of torque ripple amplitude suppression values by calculation of the following expression

(4), to calculate a torque ripple compensation cosine
coefficient i*Cn and a torque ripple compensation sine
coefficient i*Sn, and outputs these to multipliers 105b, 106b,
respectively.
[0035] [Mathematical 4]

[0036] Here, Grip(s) represents transfer characteristics of the suppression control units 102b, 103b, and i**cn/ "£**sn represent torque ripple suppression command values.
[0037] The multipliers 105b, 106b and an adder 107 perform calculation of the following expression (5) to make conversion to a cyclic signal as a converted signal synchronized with the cycle of torque ripple, thereby outputting the torque ripple compensation signal i*riP. This torque ripple compensation signal i*riP is inputted to the current command generation unit 10, whereby torque ripple is suppressed.
[0038] Cyclic signal generation units 105a, 106a generate cyclic signals for which phase compensation has been performed by the phase compensation setting value A9i corresponding to control delay of a current control system, on the basis of the electric angle speed (hereinafter, simply

referred to as speed) core obtained by a differentiator 108 differentiating the electric angle 9re of the motor 9 obtained by the rotational position detector 8. [0039] [Mathematical 5]

[0040] Here, A9i represents a set value of phase compensation based on control delay of the control system. In this case, the phase compensation setting value A9i is set in advance by being actually measured or calculated from a model.
[0041] Next, operation in the learning control mode shown in FIG. 4 will be described.
In the learning control mode, in parallel with operation being performed in the online control mode, the suppression control parameter storage unit 120 is additionally activated to store, as suppression control parameters for generating the torque ripple compensation signal i rip, the torque ripple compensation cosine coefficient i Cn and the torque ripple compensation sine coefficient T*Sn outputted from the suppression control units 102b, 103b composing the torque ripple compensation command generation unit 100, in association with the q-axis current command value i*q and the speed oore of the motor 9.

[0042] Next, operation in the offline control mode shown in FIG. 5 will be described.
In the offline control mode, the torque estimation unit 90 is stopped. Therefore, control operations of the suppression control units 102b, 103b of the torque ripple compensation command generation unit 100 are also stopped. Therefore, in this case, by the control unit 150, the suppression control parameters T*Cn, "c*Sn corresponding to the q-axis current command value i*q and the speed core of the motor 9 and stored in the suppression control parameter storage unit 120 are read and outputted to the multipliers 105b, 106b. Thus, the calculations based on the above expression (4) and expression (5) are performed, and the torque ripple compensation signal i*riP is generated offline by the torque ripple compensation command generation unit 100. Then, the torque ripple compensation signal T*riP is inputted to the current command generation unit 10, whereby torque ripple is suppressed.
[0043] Next, a sequential operation for switching among the above three control modes will be described. This is separated into (a) a switching condition for setting an appropriate control mode with respect to the speed ure of the motor 9 and (b) a switching condition for setting an appropriate control mode with respect to the q-axis current command value i*q representing the magnetic characteristics

(inductance characteristics shown above in FIG. 15) of the motor 9.
First, the switching condition for setting an appropriate control mode with respect to the speed core of the motor 9 in the above (a) will be described.
[0044] At the time of initial starting, the torque ripple frequency is low and response of the online control cannot be enhanced. Therefore, operation is started in the offline control mode. Then, as a starting period, until the speed a)re of the motor 9 becomes equal to or greater than a predetermined first speed threshold value are_iow set in advance, the offline control mode continues.
[0045] Here, as an example of setting of the first speed threshold value «re iow/ tne case where operation in the offline control mode is to be performed until the frequency of torque ripple becomes equal to or higher than a speed response cosc will be described. As described above, torque ripple is oscillation that occurs with components having orders that are integer multiples of the motor electric angle, and therefore the frequency thereof is represented as nore. Therefore, such a speed condition that the torque ripple frequency becomes equal to or higher than the speed response ^sc is ^>sc ^ nG)re <-> core > cosc/n. That is, if the first speed threshold value core iow is set as core_iow > cosc/n [rad/sec] , operation in the offline control mode can be continued until

the frequency of torque ripple becomes equal to or higher than the speed response.
[0046] Even if the speed G)re of the motor 9 becomes equal to or greater than the first speed threshold value core iOWf the suppression control parameters T*Cnr "t*Sn continue varying during acceleration or deceleration, and therefore learning of the suppression control parameters x*cnr "t*sn is not performed and the control mode shifts to the online control mode.
[0047] When acceleration or deceleration is finished and the operation becomes a steady operation, the online control mode shifts to the learning control mode, and the suppression control parameters T*Cn, T*Sn are stored in the suppression control parameter storage unit 120 in association with the q-axis current command value i*q and the speed ure of the motor 9.
[0048] In the steady operation, if the speed core of the motor 9 is an extremely high speed, the frequency of torque ripple can become such a high frequency that exceeds the band of the control system. In such a case, it is difficult to appropriately suppress torque ripple, and the suppression control parameters T*Cn, i*Sn obtained at this time are also not appropriate. Therefore, a predetermined second speed threshold value ure_high (> <^re_iow) is set in advance, and if the speed G)re of the motor 9 is equal to or greater than the

second speed threshold value ure high? the control mode shifts to the offline control mode without shifting to the online control mode or the learning control mode. [0049] Here, an example of setting of the second speed threshold value core_high will be described. In the present embodiment, the q-axis current command value i*q is corrected to perform torque ripple suppression via the current control unit 1. Therefore, if the frequency of the correction signal is equal to or higher than a current control response cocc in the current control unit 1, the influence thereof attenuates. That is, if the torque ripple frequency nore and the current control response iq_mg) • [0053] As described above, in the present embodiment 1,

the control unit 150 executes an operation sequence of selecting one of the three control modes of the online control mode, the learning control mode, and the offline control mode in accordance with the conditions of both the speed oore of the motor 9 and the magnetic characteristics (here, in particular, the inductance characteristics) of the motor 9.
[0054] The operation sequence when the control unit 150 selects and switches among the three control modes in this case is shown in a flowchart in FIG. 6. It is noted that reference character S denotes a processing step.
That is, after starting, step S101 is executed to start operation in the offline control mode. During operation in the offline control mode, in step S102, determination of switching condition regarding the speed Mre of the motor 9 is performed. That is, whether the speed core of the motor 9 is equal to or greater than the first speed threshold value core iow is determined.
In addition, in step S103, determination of switching condition regarding the inductance characteristics (q-axis current command value i q) is performed. That is, whether the q-axis current command value i*q is equal to or smaller than the second current threshold value iq_hys is determined.
If at least one of the results of step S102 and

step S103 is negative, the offline control mode continues. On the other hand, only if the results of step S102 and step S103 are both positive, step S104 is executed to shift to the online control mode.
[0055] During operation in the online control mode, in step S105, determination of switching condition regarding the inductance characteristics (q-axis current command value i*q) is performed. That is, whether the q-axis current command value i*q is equal to or smaller than the first current threshold value iq mg is determined.
In addition, determinations of switching condition regarding the speed core are performed in steps S106, S107. That is, in step S106, whether the motor is in a steady state without being accelerated or decelerated is determined. In step S107, whether the speed core of the motor 9 is equal to or smaller than the second speed threshold value ore high is determined.
If at least one of the results of step S105 and step S106 is negative, determinations in step S102 and step S103 are further performed to determine whether or not to continue the online control mode.
If the results of step S105 and step S106 are both positive, determination in step S107 is performed. If the result thereof is negative, step S101 is executed to shift to the offline control mode. If the result of step S107 is

positive, step S108 is executed to shift to the learning control mode.
[0056] During operation in the learning control mode, determinations in steps S105, S106, S107 are performed to determine whether to continue the learning control mode or shift to the offline control mode or the online control mode. [0057] FIG. 7 schematically shows switching among the control modes as a graph.
In FIG. 7, the horizontal axis is divided by the switching conditions of the first speed threshold value core iow and the second speed threshold value are_h±gh, and the vertical axis is divided by the switching conditions of the first current threshold value iq mg and the second current threshold value iq_hysA thereby obtaining nines divided regions (I) to (IX) . In this case, the offline control mode is selected in all of the regions (I) to (III), (VI), and (VII) to (IX). In the region (IV), the online control mode is selected in a state other than the steady state, and the learning control mode is selected in the steady state. In the region (V), the online control mode is selected.
[0058] As described above, in the present embodiment 1, an operation sequence is provided in which one of the three control modes of the online control mode, the learning control mode, and the offline control mode is selected in accordance with the conditions of both the speed core of the

motor 9 and the magnetic characteristics (here, in particular, the inductance characteristics) of the motor 9. Thus, it becomes possible to appropriately perform leaning of the suppression control parameters, whereby torque ripple can be effectively suppressed.
[0059] Allocation of the control modes is not limited to that in the regions (I) to (IX) shown in FIG. 7. For example, as shown in FIG. 8, in a region where the q-axis current command value i q satisfies iq mg < i q < iq hys (region (V) in FIG. 8), the learning control mode may be selected instead of the online control mode. In a region where the q-axis current command value i*q satisfies iq > iq hys (region (VI) in FIG. 8), the learning control mode cannot be executed but the online control mode may be selected instead of the offline control mode.
[0060] In the above embodiment 1, the control mode is switched by selecting among the three control modes of the online control mode, the learning control mode, and the offline control mode in accordance with the conditions of both the speed core of the motor 9 and the q-axis current command value i*q which is the magnetic characteristics of the motor 9. However, without limitation thereto, as shown in FIG. 9, one of the three control modes may be selected in accordance with only the condition of the q-axis current command value i*q.

[0061] That is, in FIG. 9, the offline control mode is always selected if the q-axis current command value i*q is equal to or greater than the second current threshold value iqjiys (regions (III), (VI), (IX)), and the learning control mode is always selected if the q-axis current command value i*q is equal to or smaller than the second current threshold value iq_hys (regions (I), (II), (IV), (V), (VII), (VIII)). [00 62] Embodiment 2
FIG. 10 is a block diagram showing the configuration of a motor control device according to embodiment 2 of the present invention. In the present embodiment 2, FIG. 11 shows a block diagram during operation in the online control mode, FIG. 12 shows a block diagram during operation in the learning control mode, and FIG. 13 shows a block diagram during operation in the offline control mode.
[0063] The present embodiment 2 is characterized in that, instead of the rotational position detector 8 in embodiment 1, a rotational position estimation unit 130 is provided and a rotational position estimation value 9re estimated there is used for control calculation.
The other configuration is the same as that in embodiment 1 shown in FIG. 1 and FIG. 2, and therefore the detailed description thereof is omitted here. [0064] Methods for estimating the rotational position of

the motor 9 are roughly classified into two methods of a method using induced voltage and a method of directly estimating the position by using high-frequency voltage in the case where the motor 9 has saliency. In the former method, the rotational position can be estimated from only electric information, but position estimation cannot be performed in a low-speed region in which induced voltage is low. On the other hand, in the latter method, position estimation can be performed over a region from low speed to zero speed, but high-frequency voltage needs to be applied, which can cause noise or vibration.
[0065] Therefore, in general, rotational position estimation of the motor 9 is often performed as follows: a certain speed threshold value G)sh is set so that the method using high-frequency voltage is employed in the low-speed region in which the speed G)re of the motor 9 is lower than the speed threshold value «sh, and the method using induced voltage is employed in a middle or higher speed region in which the speed core is higher than the speed threshold value o)sh, and thus both methods are used while being switched. [0066] Accordingly, in the present embodiment 2, the first speed threshold value «re iow for switching the control mode is set so as to coincide with the speed threshold value G)sh for switching between the usage of induced voltage and the usage of high-frequency voltage described above, that is, so as to

satisfy ash (speed threshold value for switching) =
threshold value ore iow is set so as to satisfy core iow (first j
speed threshold value) = ore v (speed at which motor and load device resonate) + core m (margin speed) . [0072] Thus, operations in the online control mode and the

learning control mode are performed only when torque ripple of the motor 9 itself is dominant while avoiding mechanical resonance influence. Therefore, it becomes possible to appropriately perform learning of the suppression control parameters. [0073] Embodiment 4
The basic configuration of a motor control device according to the present embodiment 4 is the same as that in embodiment 1 shown in FIG. 1 and FIG. 2, and therefore the detailed description thereof is omitted here.
[0074] The present embodiment 4 is characterized in that a temperature detector (not shown) for detecting a temperature tm of the motor 9 is provided to the motor 9 and a temperature threshold value tm_high is set for the detected temperature tm. The control unit 150 performs control so that operation is performed in the offline control mode when tm_high < tm is satisfied.
[0075] Thus, operations in the online control mode and the learning control mode can be performed so as to avoid a high-temperature region in which the characteristics of the motor 9 greatly vary. Therefore, it becomes possible to appropriately perform learning of the suppression control parameters.
[0076] An operation sequence for the control unit 150 to select and switch among the three control modes on the basis

of the switching conditions in the present embodiment 4 is shown in a flowchart in FIG. 14.
[0077] In FIG. 14, as compared to FIG. 6, determination of switching condition regarding the temperature tm in step S202 is added as the determination for shifting from the online control mode to the learning control mode. If a determination result in step S202 is negative, the control mode shifts to the offline control mode (step S101). Only if the determination result in step S202 is positive, the control mode shifts to the learning control mode (step S202). [0078] It is noted that the configuration of the motor control device of the present invention is not limited to those shown in the above embodiments 1 to 4, but without deviating from the scope of the present invention, the above embodiments 1 to 4 may be freely combined with each other or each embodiment 1 to 4 may be modified or simplified as appropriate. [0079] Embodiment 5
FIG. 16 is a configuration diagram showing an example in which the motor control device of any of the above embodiments 1 to 4 is applied for controlling a motor that rotates a drive sheave 205 provided to a hoisting device which lifts and lowers a car of an elevator.
[0080] In the elevator according to the present embodiment 5, a car 203 and a balance weight 204 are connected via a

rope 202 wound on the drive sheave 205 as a hoisting device. The drive sheave 205 is connected to a rotary shaft of a PM motor 9, and is rotationally driven by the PM motor 9. In addition, the elevator includes a rotational position detector 8 and a control device 201 for performing drive control of the PM motor 9 to lift and lower the car 203 within a hoistway.
[0081] The control device 201 in this case is composed of the parts shown in FIG. 1 and FIG. 2 other than the PM motor 9 and the rotational position detector 8, and the basic configuration thereof is the same as that in embodiment 1 shown in FIG. 1 and FIG. 2. Therefore, the detailed description thereof is omitted here.
[0082] The present embodiment 5 is characterized in that a weight detector (not shown) is provided to the car 203, a weight threshold value Mm_high is set in advance for a detected car weight Mm and a weight Mw of the balance weight 204, and the control unit 150 performs control so that operation is performed in the offline control mode when I Mm high _ Mw | <
|Mmj - Mw| is satisfied.
[0083] If the car weight Mm is greater than a certain weight, the PM motor 9 is driven with high torque from the time of starting. That is, such current as to exceed the current threshold value iq_hyS (> iq_mg) and cause a hysteresis minor loop can be needed from the time of starting.

[0084] Accordingly, in the present embodiment 5, if such a hysteresis minor loop is predicted to appear beforehand, operation in the offline control mode can be performed initially, and thereafter, whether or not to shift to the online control mode or the learning control mode is doubly determined using the weight threshold value Mm_high and the current threshold value iqhys • Thus, it becomes possible to more safely and appropriately perform learning of the suppression control parameters.
[0085] An operation sequence for the control unit 150 to select and switch among the three control modes in the present embodiment 5 is shown in a flowchart in FIG. 17. It is noted that reference character S denotes a processing step.
In FIG. 17, as compared to FIG. 6, determination of switching condition regarding the car weight Mm in step S203 is added as the determination for shifting from the offline control mode to the online control mode. If a determination result in step S203 is negative, the control mode shifts to the offline control mode (step S101). Only if the determination result in step S203 is positive, the control mode shifts to the online control mode (step S103). [0086] The elevator of the present embodiment 5 has been described under the assumption that the motor control device having the configuration of embodiment 1 is provided. However, without limitation thereto, the motor control

devices having the configurations of the other embodiments 2 to 4 may be applied.

CLAIMS [1] A motor control device comprising:
an AC motor;
a current detection unit which detects at least currents for two phases among three phases;
a current control unit which generates voltage command values on control coordinate axes, using current detection values detected by the current detection unit;
a torque estimation unit which estimates torque of the AC motor on the basis of the voltage command values and the current detection values;
a torque ripple suppression unit which generates a suppression command for suppressing torque ripple of the AC motor, on the basis of estimation torque estimated by the torque estimation unit; and
a suppression control parameter storage unit which stores a suppression control parameter for generating the suppression command, in association with a current command value and a speed of the AC motor,
the motor control device further comprising a control unit which executes an operation sequence of selecting, in accordance with a switching condition calculated from magnetic characteristics of the AC motor, one of three control modes of: an online control mode in which torque ripple suppression is performed by the torque ripple

suppression unit; a learning control mode in which torque ripple suppression is performed by the torque ripple suppression unit and at the same time, the suppression control parameter storage unit stores the suppression control parameter; and an offline control mode in which torque ripple suppression is performed using the suppression control parameter stored in the suppression control parameter storage unit.
[2] The motor control device according to claim 1, wherein, in execution of the operation sequence, the control unit does not select the learning control mode when magnetic characteristics of a magnetic flux with respect to current of the AC motor forms a hysteresis minor loop.
[3] The motor control device according to claim 1, wherein, in execution of the operation sequence, a current threshold value or a torque threshold value is set which corresponds to a condition that magnetic characteristics of a magnetic flux with respect to current of the AC motor forms a hysteresis minor loop, and the control unit performs selection of the learning control mode in accordance with the current threshold value or the torque threshold value.
[4] The motor control device according to any one of

claims 1 to 3, wherein, in execution of the operation sequence, the control unit selects one of the three control modes in accordance with a speed threshold value calculated from transfer characteristics from a torque command value to a torque estimation value.
[5] The motor control device according to any one of claims 1 to 3, wherein, if a speed estimation unit is provided to the AC motor, in execution of the operation sequence, the control unit selects one of the three control modes in accordance with an operation condition of the speed estimation unit.
[6] The motor control device according to any one of claims 1 to 3, wherein, if the AC motor is connected to any load device, in execution of the operation sequence, the control unit selects one of the three control modes in accordance with a speed threshold value calculated from resonance characteristics of the load device.
[7] The motor control device according to any one of claims 1 to 6, wherein, in execution of the operation sequence, the control unit selects one of the three control modes in accordance with a temperature threshold value calculated from temperature characteristics of the AC motor.

[8] An elevator comprising:
the motor control device according to any one of claims 1 to 7;
a car;
a balance weight;
a rope connecting the car and the balance weight; and
a drive sheave which is rotated by a drive force of the AC motor and on which the rope is wound.
[9] The elevator according to claim 8, wherein
in execution of the operation sequence, the control unit selects one of the three control modes in accordance with a weight threshold value calculated on the basis of a weight of the car and a weight of the balance weight.