JPH0429583A - Method and apparatus for controlling motor - Google Patents

Abstract

PURPOSE:To accurately suppress vibration of a motor in a simple structure by sequentially varying the amplitudes of exciting currents to be supplied to phase windings of the motor at respective exciting coils, and moving the variation synchronously with the detected rotary position signal. CONSTITUTION:When a phase thetam and amplitude coefficient (m) to be supplied to a damping modulator MC are decided, it is divided into the case in which a rotary unbalance due to the deviation of the center of a shaft and the center of gravity is previously known and the case in which it is not previously known. In the former case, the phase thetam is fixed, and the coefficient (m) is varied in proportion to the rotating speed omegar obtained by differentiating a rotary position signal thetar. In the latter case, for example, there is no room for searching a rotary unbalance, or rotary unbalance is generated by an additive such as a tool, etc. In this case, the thetam and the m for minimizing the vibration are searched by scanning a table in a range of 0 - 2pi in terms of the phase thetam and in a range of 0 - 1 in terms of the coefficient (m).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control method and a control device for an electric motor having a vibration damping function.

[Conventional technology]

In general, self-excited vibrations that occur in a motor that rotates at high speed can be caused by rotational unbalance due to a shift in the center of gravity of the motor's shaft or shaft clearance, or can be caused by a driven load connected to the motor. Such vibrations greatly affect the function and performance of equipment equipped with the motor, and in extreme cases may even lead to damage to the motor itself.

As countermeasures against such vibrations, passive vibration damping mechanisms and active vibration damping mechanisms have been proposed.

As an example of a passive type, an automatic balance mechanism has been proposed in which a ring sealed with liquid or steel balls is attached to the driven shaft. This method absorbs vibrations by utilizing the property that liquid and steel balls are uniformly distributed within the ring due to the centrifugal force generated as the shaft rotates. It is called a passive vibration damping mechanism because it damps the vibrations that occur without suppressing the vibrations themselves.

On the other hand, there is an active vibration damping mechanism that actively suppresses vibrations. For example, in a magnetic bearing that magnetically receives the shaft of a motor, there is a method in which the excitation of the magnetic bearing is actively suppressed in accordance with the shaft rotation and vibrations generated, and a method in which the gap between the air pad and the shaft of an air bearing is controlled. A method of damping vibration by changing dynamic stiffness has been proposed.

However, the above-mentioned vibration damping methods, whether passive or active, focus on the vibration itself and attempt to suppress it.

On the other hand, there have been many proposals to use AC motors, such as induction motors and synchronous motors, in servo systems. For example, there are AC servo motors in which a vector control method is applied to an induction motor. The details of this method will be described later, but basically the current input to the AC servo motor is detected by a current detector, the rotation speed is detected by a speed detector, and the rotor position is detected by a position detector. However, current control, speed control, and position control are performed by feeding these back to each other.

The present invention further provides a control method for this AC servo motor.
By providing a motor vibration damping function in addition to the C servo control function, it is possible to cope with motor vibrations not only in servo systems but also in machine tools and the like.

Therefore, the vibration damping function according to the present invention can be said to be an active vibration damping mechanism in that it actively suppresses vibrations.

FIG. 8 is a block diagram of a conventional AC servo motor control device. In the figure, IM is an induction motor, SS is a rotational position detector, CT is a current detector, PI is a power converter, CA is a current control amplifier, PA is a power amplifier that collectively refers to CA and PI, and CG is a three-phase current command. This is a generation circuit.

The rotational position detector SS is, for example, a rotary encoder, and is an absolute encoder that outputs an absolute phase θr. It is also possible to output the rotational speed ωr obtained by differentiating the phase.

The power converter PI may convert alternating current to direct current with a built-in converter (not shown), and then convert the direct current to alternating current with a built-in inverter (not shown), and drive the motor with the output of the current control amplifier CA. Motor IM based on the power of the size
supply to.

The current detector CT detects the current flowing through each winding, and feeds back the detected currents iu, 'iv, and i to the corresponding current control amplifiers CA.

The current control amplifier CA is provided for each phase winding, adds the feedback detected currents iu, iviv and the corresponding current command values Iu, Iv, Iw, amplifies the result, and sends it to the power converter PI. send.

The three-phase current command generation circuit CG generates a current amplitude command I and a slip frequency W that is the difference between the slip frequency command ωS and the rotational speed ωr.
The current commands IuIv and Iw are generated based on the current commands IuIv and Iw.

FIG. 9 is a wiring diagram of a conventional excitation coil. As shown in the figure, there are four U-phase coils, Ul, U2U3. U4 are all connected in parallel and connected to power converter PI. The V-phase and W-phase are also connected in exactly the same way. Therefore,
The current for each phase is collectively detected by the current detector CT and fed back to the current control amplifier CA to collectively control the current for each phase.

[Problem to be solved by the invention]

In the above-mentioned conventional technology, measures to suppress vibration itself such as passive vibration damping mechanisms and active vibration damping mechanisms cannot completely relieve the unbalance caused by fluctuations in the slave side load in the passive type. Another problem with the active type is that it makes the damping mechanism extremely complex and expensive.

Furthermore, in the case of an AC servo motor, the control device has the disadvantage that, as described above, the excitation coils of each phase are connected in parallel and collectively controlled, so that delicate vibration control (vibration suppression) cannot be performed.

The purpose of the present invention is to improve the conventional AC servo motor control system and provide a motor vibration damping function in addition to the AC servo control function. An object of the present invention is to provide a method and apparatus for controlling an electric motor having a vibration damping function that can suppress vibrations with a simple structure and high precision.

[Means to solve the problem]

FIG. 1 is a diagram showing the principle configuration of the present invention.

The present invention sequentially changes the magnitude and phase of an excitation current supplied to each phase winding of a motor for each excitation coil, and moves this change in synchronization with a detected rotational position signal.

Specifically, according to the first invention, vibrations of a rotating electric motor are detected, and the magnitude and phase of the current supplied to each phase winding of the electric motor are sequentially changed in synchronization with the rotational speed of the electric motor, A method for controlling a motor is provided, in which the magnitude and phase of a current when the vibration of the motor becomes small is determined, and the current is supplied to the motor to keep the vibration of the motor as small as possible. According to a second aspect of the present invention, there is provided a control device for an electric motor in which the magnitude and phase of the excitation current supplied to each phase winding of the motor are sequentially changed for each excitation coil. a power amplifying means for supplying an amplified current; and a current for controlling the magnitude and phase of the current supplied to each phase of each of the power amplifying means based on vibrations detected from the electric motor so that vibrations of the electric motor are minimized. a control means, and vibration damping for supplying each phase current modulated to each of the power amplification means based on the magnitude and phase of the current output from the current control means and the rotational position signal detected from the electric motor. Provided is a motor control device characterized by comprising a modulation means.

[Function] In the present invention, in an induction motor or a synchronous motor, the excitation coils, which have conventionally been connected in parallel and controlled collectively, are individually controlled as shown in Fig. 3, and basically the same as when connected in parallel. Apply control to each coil.

On the other hand, the centrifugal force due to the deviation of the center of gravity of the motor shaft changes its magnitude depending on the motor rotation speed, and is generated in the radial direction while moving at the same rotation speed as the motor rotation speed. At a certain moment and at a certain rotation angle position, the excitation current of the motor is controlled to generate an attractive force between the rotor and the stator of the same magnitude and opposite direction as the centrifugal force, and to make this attractive force equal to the rotational speed of the motor. When moving at rotational speed, centrifugal force and suction force cancel each other out, eliminating vibrations caused by centrifugal force.

Furthermore, when the magnitude of the centrifugal force changes, the magnitude of the suction force is also changed in accordance with the magnitude of the centrifugal force.

In other words, the current applied to the excitation coil is modulated to an excitation intensity that is synchronized with the rotation of the rotor and has a magnitude and phase difference commensurate with the centrifugal force, in a manner that is superimposed on the individual control of each coil described above. As a result, the suction force changes in the circumferential direction, and rotational force is obtained while canceling centrifugal force.

〔Example〕

FIG. 2 is a block diagram of an embodiment of the present invention. Second
In the figures, the same components as in the prior art are given the same reference numerals. In the figure, VT is a vibration detector, PC is a vibration damping phase/amplitude command generation circuit as a current control means, and MC is a vibration damping modulation circuit.

As described above, the mechanical structure of the motor remains unchanged, and the lead wires are simply taken out for each pole of the winding, as shown in FIG.

Therefore, as shown in the figure, the number of current detectors, power converters, current control amplifiers, vibration damping modulation circuits, etc. is equal to the number of poles (four in this embodiment). That is, CTI to CT4 are current detectors, FIL to PI4 are power converters, and CAL to C
A4 is a current control amplifier, MCl-MC4 is a damping modulation circuit, and four sets are provided.

However, the power converter does not need to be 4 times as it is, but 1/4 the time.
All you need to do is install four units with the same performance.

In this way, the control device has a configuration in which power converters, etc. are connected in parallel as many as the number of poles, and the current command value supplied to these is multiplied by a command value for the purpose of damping vibration (vibration control command value). do.

As explained in Fig. 5, which will be described later, the vibration suppression command value of each exciting coil has a sinusoidal distribution centered on 1 in the circumferential direction so that the vibration at the target location is minimized, and the rotation of the rotor is Proceeds with a phase difference. The amplitude coefficient and phase difference of the sine distribution are determined by learning control in a short time from the start of rotation, and optimization can be continued at all times during rotation.

FIG. 4 is a block diagram of an embodiment of the vibration damping modulation circuit of FIG. 2. In FIG. 4, MT is a multiplier, AD is an adder, AMP is an amplifier, and SC is a sine wave oscillator that oscillates N types of sine waves shown in FIG. 5(C). In this case, the sine wave oscillator O8C includes a damping phase/amplitude command generation circuit PC.
The phase θm and amplitude coefficient m are manually inputted from , and the rotational position signal θr detected by the rotational position detector SS is inputted,
Outputs N types of sine waves as shown in the following formula.

5in(θr+θm+(2π/N) X i) River (1
) Here, N is the number of excitation coils (in this example, N=12
), where 1 is an integer from O to (N-1).

When the oscillator OSC outputs equation (1) from 1=D to 11 for each set, each multiplier MT multiplies the amplitude coefficient m, and the adder AD calculates the current of each phase from the current command generation circuit CG. A command value Iu·rvI- is added. As a result, for example, the following equation is obtained for the U phase.

Iu l =Iu (1+m-5in(θr+θm+(
2π/12)Xi))...(2) Here, Iul is i=Q, Iu2 is 1=3, Iu3 is 1
=6, and i=9 for Iu4.

Phase (2) and phase W can also be determined in exactly the same manner.

5(a), (b), and (C) are explanatory diagrams of the basic operation of the circuit of FIG. 4. In (a), when the vibration damping modulation circuit MC receives three-phase alternating current of UV and W phases from the three-phase current command generation circuit CG, the vibration damping modulation circuit MC receives the rotational position signal θr, the phase θm, and the amplitude coefficient m as shown in FIG. Iul~ by the circuit
Output Iw4.

In (b), when there are three phases of U, V, and W, and each phase has four sets, there are 12 exciting coils as shown in the figure.

That is, Ul to U4. Vl~V4. Wl ~ W4 (7
) 12 excitation coils.

(c) is an expanded version of figure (b), with U and V.

It is a figure explaining modulation of W. If the current values of each phase U, V, and W are modulated as shown in the figure to give them strengths and weaknesses (amplitude coefficient m), for example, even in the same U phase, a strong attractive force X will be generated in the modulated excitation coil, and the rotor will It is drawn to the side with the stronger bow suction force and rotates. However, as it is, the attraction force X is biased in one direction.
It is clear that vibrations are generated.

In the present invention, in order to rotate the suction force, the modulation curve as shown in Figure 26(c) is moved in synchronization with the rotational position θr detected by the rotational position detector ss or the rotational speed ωr obtained by differentiating this. It's about letting people know.

On the other hand, vibration of a motor shaft is generally caused by centrifugal force caused by a shift in the center of gravity. Therefore, if suction force is applied in a direction that cancels out this centrifugal force, the force relationship will be canceled out and vibrations should be suppressed. Therefore, in the present invention, as described above, by moving the modulation curve in synchronization with the rotational speed ωr and rotating the suction force, the centrifugal force is always canceled out and vibrations are suppressed.

FIG. 6 is a block diagram of an embodiment of the damping phase/amplitude command generation circuit PC shown in FIG. 2.

Here, when determining the phase θm and amplitude coefficient m to be supplied to the vibration damping modulation circuit MC, there are two cases in which the rotational imbalance caused by the deviation between the center of the shaft and the center of gravity is known in advance, and It is divided if it is not clear. In the former case, the phase θm is fixed, and the amplitude coefficient m changes in proportion to the rotational speed ωr obtained by differentiating the rotational position signal θr.

In the latter case, for example, there is no room to detect rotational imbalance due to production efficiency, or rotational imbalance is caused by an additional object such as a tool. in this case,
Scan the table with the phase θm in the range of 0 to 2π and the amplitude coefficient m in the range of 0 to 1 to find 6m where the vibration is the smallest.
and m.

This circuit is a circuit that inputs the vibration α of the motor detected by the vibration detector VT, and sends the phase θm and amplitude coefficient m obtained by learning control for the above two cases to the vibration damping modulation circuit MC.

As shown in FIG. 7, TB is a table storing various combinations of phases θm and amplitude coefficients m, and is stored in the ROM. SC is a scanning means for scanning the phase θm and amplitude coefficient m of the table TB, and outputs the phase θm and amplitude coefficient m as the scanning result.

The MOC is a mode control circuit, and is a means for switching between a mode in which the optimal θm and m are determined for the latter case by learning control before actual vibration measurement, and a mode in which actual vibration control is performed. Therefore, if the rotational imbalance is not known, at the learning control stage, the switch 5ll
ll, SW2 is set to the scanning means side (contact a side) and the phase θm and amplitude coefficient m of the table are scanned in advance,
These values are sequentially given to the vibration damping modulation circuit MC, and the vibration A of the system is
Find the phase θm and amplitude coefficient m when the value is the smallest. The obtained θm and m and the vibration A are held in the holding circuit HOL. Note that the vibration A is a value obtained by integrating vibrations at fixed time intervals by the vibration calculation circuit VC.

Next, set the switches SWI and SW2 to the contact side, and apply the set phase θm and amplitude coefficient m to the damping modulation circuit MC.
to perform actual vibration control.

On the other hand, if the rotational unbalance becomes large due to some external factor such as a tool change, and the vibration of the system increases, the value B of the vibration α that occurs at this time is determined by the vibration calculation circuit VC, and the comparator COM The minimum value of vibration A determined in advance by
Compare with. In this case, if vibration B is smaller, the phase θ
There is no need to change m and the amplitude coefficient m. However, if vibration B is larger, the mode control circuit MOC causes switch SWI.

Switch SW2 to the contact a side and scan the table TB again to find the minimum value of the vibration of this system as described above. Then, the switch is set to the contact side again to perform vibration control.

Note that the holding circuit HOL may be any holding circuit that compares the previous value and the current value and holds the smaller value.

FIG. 7 is an example of a table storing the relationship between θm and m described above, and is stored in the ROM. The horizontal axis is θm, and the vertical axis is the amplitude coefficient m. The range of θm is 0 to 2π, and the range of m is 0 to 1.

〔Effect of the invention〕

As explained above, according to the present invention, there is provided a method and method for controlling an electric motor that can accurately suppress vibrations of the electric motor using electrical means with a simple structure without adding a mechanical vibration damping device with a complicated structure. The device was obtained. In addition, even if a load is connected to this motor and there is no prior knowledge of the unbalance of the system and the vibrations caused by it, vibration can be suppressed in a short period of time from the start of rotation. can also respond quickly.

[Brief Description of the Drawings] Fig. 1 is a basic configuration diagram of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is an excitation coil connection diagram of the present invention, and Fig. 4 is a diagram of the second embodiment of the present invention. 5(a), (b), and (c) are detailed explanatory diagrams of the present invention. FIG. 6 is the damping phase/amplitude command of FIG. 2. FIG. 7 is an example of the table shown in FIG. 6, FIG. 8 is a block diagram of a conventional control device, and FIG. 9 is a conventional excitation coil connection diagram. (Explanation of symbols) IM...Induction motor, CT...Current detector, P
A...Power amplifier, PI...Power converter, CA
...Current control amplifier, MC...Vibration damping modulation circuit, CC
...Current control means, PC...Vibration suppression phase/amplitude command generation circuit, CG...3
Phase current command generation circuit, VT...8 vibration detectors, SS...rotational position detector. U-phase coil Excitation coil wiring diagram of the present invention No. ＋E U-phase coil Conventional excitation coil wiring diagram No. 1

Claims (1)

[Claims] 1. The vibration of a rotating electric motor is detected, and the magnitude and phase of the current supplied to each phase winding of the electric motor are sequentially changed in synchronization with the rotational speed of the electric motor. A method for controlling an electric motor, characterized in that the magnitude and phase of the current when the vibration becomes small are determined, and the current is supplied to the electric motor to keep the vibration of the electric motor as small as possible. 2. In a motor control device that sequentially changes the magnitude and phase of the excitation current supplied to each phase winding of the motor for each excitation coil, the electric power that supplies the amplified current to each phase winding of the motor. an amplifying means; a current controlling means for controlling the magnitude and phase of the current supplied to each phase of each of the power amplifying means based on vibrations detected from the electric motor so as to minimize vibrations of the electric motor; and the current controlling means. vibration damping modulation means for supplying each phase current modulated to each of the power amplification means based on the magnitude and phase of the current output from the electric motor and the rotational position signal detected from the electric motor. Characteristic electric motor control device.