JPH07222486A - Method and apparatus for starting drive of ac servo- motor - Google Patents

Abstract

PURPOSE: To provide a method and an apparatus for starting an AC servo motor in driving with a maximum torque using a low-cost general-purpose encoder. CONSTITUTION: In an AC servo motor, a stator 110, a rotor 112 with a permanent magnet, a current-feeding means 106 for feeding a current, to the stator 110 under control, a current-feeding means 108 for generating a current signal, a general-purpose encoder 114 for generating a signal, and a position control means 112 for generating a speed command signal, corresponding to the position command signal are provided. In addition, a speed-calculating means 112 for calculating the speed from the signal, a speed control means 124 for comparing the speed signal with the speed command signal and generating a current command signal, and a current control means 118 for comparing the current signal of a current-detecting means 108 with a current command signal from the speed control means 124 and generating a control signal to the current feeding means 106 are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a synchronous AC servomotor, and more particularly to a drive starting apparatus and method for a synchronous AC servomotor using a general-purpose encoder.

[0002]

2. Description of the Related Art Generally, a servo motor comprises a motor for generating power and a servo mechanism for controlling the motor. Servo motor is AC servo motor, D according to the power supply system
It is classified into a C servo motor, a DC brushless servo motor, and the like, and is classified into a synchronous servo motor and an asynchronous servo motor depending on the presence or absence of a restoring force when the position of the rotor of the servo motor is displaced.

A synchronous AC servomotor generally has a rotor and a stator, similar to a normal motor. Synchronous type A
The most important feature of the C servo motor is that the rotor is a permanent magnet. In order to maximize the torque of the motor in such a synchronous AC servomotor, it is necessary to match the phase of the current flowing through the winding of the stator with the magnetic flux of the permanent magnet at all times in accordance with the rotational position of the permanent magnet. Therefore, in order to improve the efficiency of the AC servomotor in the synchronous AC servomotor, it is necessary to accurately grasp the rotational position of the permanent magnet that is the rotor.

In order to accurately grasp the rotational position of the rotor, which is a permanent magnet, conventionally, a special encoder for magnetic pole detection that outputs a magnetic pole detection signal representing the magnetic pole of the rotor is used, or a general-purpose encoder and a rotor are used. A Hall sensor and a resolver were used in combination as an auxiliary detection device for detecting the rotational position of the permanent magnet.

A synchronous AC servomotor for detecting the rotational position of a rotor using a special encoder for outputting a magnetic pole detection signal is disclosed in Japanese Patent Laid-Open No. 6-102935.
Here, as an encoder for the AC servo motor, A,
The rotation position of the rotor is detected by using a special encoder that outputs the B and Z phases and the U, V, and W phases for magnetic pole alignment. Particularly, in the above publications, A, B, Z phases and U, V,
The W phases are connected to the same line, and when the motor is first turned on, the U, V, and W phases are used to determine the magnetic pole position, and thereafter, the A, B, and Z phases are used to change the magnetic pole position. By using the method of switching the current phase accordingly, it is possible to prevent the number of wires for driving the motor from increasing.

Further, another method for detecting the rotational position of the rotor is disclosed in JP-A-5-83978. Here, the rotational position of the rotor is detected by using the A, B, Z phases and the magnetic pole position commutation signal as the encoder of the AC servo motor.

Further, Japanese Unexamined Patent Publication No. 6-153576 discloses a method of detecting a rotational position of a rotor by using a general-purpose encoder and a special detection method. Here, by applying a voltage corresponding to an arbitrary magnetic pole position to the synchronous AC servo motor to detect in the rotation direction of the motor, sensing the current value at that time, and repeating the process of correcting the current phase again, the final The phase where the current is minimized is searched for, and thereafter, the A and B phase pulses are counted and the current phase changed according to the rotation angle of the rotor is supplied to operate the motor.

[0008]

However, in the above-mentioned conventional method, first, Japanese Patent Laid-Open No. Hei 6-102935.
, It was possible to reduce the number of wires by using the same line for the A, B and Z phases and the U, V and W phases.
There is a problem that the price of the AC servomotor becomes expensive by using a special encoder which is still expensive.

Further, in the above-mentioned Japanese Patent Application Laid-Open No. 5-83978, there is a problem in that the number of wirings of the encoder signal is large because the commutation signal for magnetic pole alignment is used, and in particular, an expensive feedback sensor must be used.

Further, in the above-mentioned Japanese Patent Laid-Open No. 6-153576, since the feedback current is detected to search for the minimum current, if the servo motor is assembled in the system, irregular friction torque or coupling will occur. Therefore, the calculation of the magnetic pole value may be inaccurate due to the influence of the eccentricity or the deviation angle on the specific current value. Therefore, there is a problem that the motor cannot always output the maximum torque thereafter.

Accordingly, it is an object of the present invention to provide a driving start method and apparatus for an AC servomotor capable of maximizing the torque of a rotor while using a low-priced general-purpose encoder.

A further object of the present invention is to provide a driving start method and apparatus for an AC servo motor which can accurately detect the rotational position of a rotor by using a low-cost general-purpose encoder.

[0013]

An AC servomotor drive starting device of the present invention for achieving the above object is rotatably disposed inside a stator and the stator and applies a magnetic flux to the stator. In the AC servomotor including a rotor, a current supply means for supplying a controllable current to the stator; a current current signal for detecting a magnitude of a current supplied from the current supply means to the stator. A general-purpose encoder for monitoring the rotor to generate A, B and Z phase signals; an A and B phase signal provided from the general encoder and a position command signal provided by a user Position control means for generating a speed command signal in response to the current speed signal of the rotor from the A or B phase signal provided from the general-purpose encoder to calculate the current speed signal of the rotor. A speed calculation means for generating; a speed control means for generating a current command signal by comparing a current speed signal from the speed calculation means and a speed command signal from the position control means; a current command signal from the speed control means A current control means for providing a control signal to the current supply means by comparing the current current signal from the current detection means and
The control signal uses an A or B phase signal provided from the general-purpose encoder, and is configured to include a current control unit determined by a magnetic pole angle calculation of the rotor.

Further, the current control means generates a locking current for locking the rotor when an initial current is supplied to the stator, and uses the A and B phase signals from the general-purpose encoder, Magnetic pole initialization calculation means for generating an initial current phase signal for the locking after confirming the locking of the rotor; the initial current phase signal provided from the magnetic pole initialization calculation means and the A or B phase from the general-purpose encoder A magnetic pole angle calculating means for generating a changed current phase signal which is changed according to the rotation angle of the rotor by using the signal; a rocking current signal from the magnetic pole initialization calculating means and a current command signal from the speed control means. Is selectively input, the selected signal is compared with the current current signal from the current detecting means to calculate the error, and And means for providing an initial current phase signal and the pole angle calculation and a change current phase signals from the means selectively input control signal to said current supply means by multiplying said error in an initialization operation means.

Further, according to the present invention, a stator, a rotor rotatably arranged in the stator to apply a magnetic flux, and an encoder for monitoring a rotational movement of the rotor to generate a feedback pulse. In the method for starting the driving of an AC servomotor, the method includes: after supplying power, supplying a locking current having an arbitrary phase to the stator to lock the rotor; and counting feedback pulses output from the encoder. A step of confirming whether or not the rotor is locked; a step of supplying a drive current having a phase shifted by 90 ° from a phase of the locking current to the stator when the rotor is locked; and an output from the encoder. The step of counting the number of feedback pulses to detect the rotation angle of the rotor and the phase of the drive current of the rotor. Rolling rotor torque by changing in accordance with the angle a driving start method of the AC servo motor and a step to maximize.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a drive starting device for an AC servomotor according to the present invention. As shown in the figure, the AC servo motor drive starting device includes a motor unit 100 for generating power and a servo mechanism for controlling the movement of the motor unit.

In the motor section 100, reference numeral 110 is a motor stator, and 112 is a rotor that applies magnetic flux to the stator. The stator 110 of the motor is wound with U, V and W windings, and each winding is supplied with currents I _U , I _V and I _W having a phase difference of 120 °. In this embodiment, for convenience of explanation, the number of magnetic poles of the rotor 112 is eight.

The current I _U supplied to the stator 110,
I _V and I _W are provided through the power supply input terminal 102, the rectifier circuit 104, the inverter 106, and the current detection unit 108. The AC power input to the power input terminal 102 is converted into DC by the rectifier circuit 104. The converted direct current is applied to the inverter 106 to generate a controllable current according to a drive signal provided from a drive circuit 116 described later. The current detecting unit 108 provides a current current signal obtained by detecting the magnitude of the current supplied to the stator 110 to the current control unit 118 described later through the line L4.

Drive circuit 1 for driving the inverter 106
16 is usually composed of a pulse width modulation circuit (not shown) and a base drive circuit (not shown). The pulse width modulation circuit is provided for each phase U output from the current control unit 118, which will be described later.
The voltages corresponding to the V and W current signals I _U , I _V , and I _W are input, the pulse width is modulated, and the modulated pulse is output to the base drive circuit. The base drive circuit receives the pulse modulated from the pulse width modulation circuit, and the inverter 106
A switching signal is output to the bases of the respective transistors Q1 to Q6.

On the other hand, the general-purpose encoder 114, which is one of the constituent elements of the servo mechanism, monitors the rotor 112 and A
B and Z phase signals are generated. These signals pass through the line group LG2 and the current control unit 118 and the position control unit 120.
And the speed calculation unit 122, respectively. The A, B and Z phase signals will be briefly described below.
The phase signals are all in the form of pulses. First, the Z-phase signal consists of pulses that are generated one by one when the rotor makes one revolution. On the other hand, the A-phase and B-phase signals consist of a large number of pulses evenly divided over 360 ° which is one rotation angle of the rotor, for example, 2000 pulses per rotation. The A and B phase signals have a phase difference of 90 ° depending on the rotation direction of the rotor.

The position control unit 120 compares the position command signal (external pulse input) designated by the user with the position feedback (A and B phase signals from the general-purpose encoder 114) signal, calculates the error to be corrected, A speed command (speed data) signal is output to the speed control unit 124 by multiplying the position gain value.

On the other hand, the speed calculation unit 122 is usually composed of a frequency quadrupling circuit and an up / down counter (both not shown), and the A phase and B phase input from the general-purpose encoder 114 through the line group LG2. The phase signal is multiplied by 4, and the speed value is output from the number of pulses counted during a predetermined time.

The speed control unit 124 compares the speed command signal provided from the position control unit 120 with the output signal from the speed calculation unit 122 to calculate the error, and the current command obtained by multiplying the position gain value. Signal through line L2
It is provided to the current control unit 118, which will be described later in connection with.

FIG. 2 is a detailed block diagram of the current controller 118 in the AC servomotor shown in FIG. Figure 2
As shown in, the current control unit 118 includes a switch control and magnetic pole initialization calculation unit 206, a magnetic pole angle calculation unit 208, a read-only memory (ROM) 210, a comparison unit 202, a drive circuit control signal generation unit 204, and two switches. SW
1 and SW2. The current control unit 118 is a drive circuit that always makes the phases of the currents I _U , I _V , and I _W provided to the stator windings orthogonal to the magnetic flux of the permanent magnet according to the rotational position of the permanent magnet that is the rotor. Control signal drive circuit 1
16 (FIG. 1) to maximize the torque of the motor.

In order to make the phases of the magnetic flux of the permanent magnet, which is the rotor, and the currents I _U , I _V , and I _W supplied to the stator orthogonal to each other, the position of the rotor must first be accurately grasped. I have to. This can be seen by supplying a constant current to the stator to lock the rotor. That is,
When I _U , I _V , and I _W are constantly supplied, the rotor is locked in a position parallel to each current direction. Therefore, since the phase angles of the currents I _U , I _V , and I _W for locking the rotor are known, the position of the rotor in a locked state can be known. In the present invention, whether or not the rotor is locked can be known by counting the number of pulses of the A-phase or B-phase signal output from the general-purpose encoder when the rotor rotates.
That is, if the number of pulses is zero, then the rotor is locked. When the rotor is locked, the current I provided to the stator windings orthogonal to the rotor flux
_U, I _V, the initial phase of the I _W can be easily obtained by addition or subtraction current I _U for causing rocking rotor, I _V, the electrical angle 90 ° to the phase of the I _W.

In one embodiment of the present invention, the initial phases of the currents I _U , I _V , and I _W provided to the stator winding are determined by the switch control and magnetic pole initialization calculation unit 206, and the current phases after that are determined. Is determined by the magnetic pole angle calculation unit 208.

Switch control and magnetic pole initialization calculation section 20
6 locks the rotor when the AC servomotor is first supplied with power, so that U, V and W of the stator are locked.
The current value of each phase is output through the line L7, and the A-phase or B-phase signal provided from the general-purpose encoder 114 (FIG. 1) through LG2 is counted to confirm whether the rotor is locked. When the locking of the rotor is confirmed, that is, when the A-phase or B-phase pulses are not counted any more, the switch control and magnetic pole initialization calculation unit 2
06 provides an initial current phase value for transmitting the maximum torque to the drive circuit control signal generator 204 and the magnetic pole angle calculator 208 through the line L8.

The magnetic pole angle calculation unit 208 uses the initial current phase value provided from the switch control and magnetic pole initialization calculation unit 206 as a reference, and A or B provided from the general-purpose encoder 114 (FIG. 1) through the line group LG2.
The current phase value corresponding to the rotation angle of the rotor obtained by counting the phase pulses is searched from the sine table stored in the ROM 210 and provided to the drive circuit control signal generator 204 through the line L9.

On the other hand, the switch SW1 is responsive to the switch control signal from the switch control and magnetic pole initialization calculation unit 206, in response to the current command signal from the speed control unit 124 (FIG. 1) or the switch control and magnetic pole initialization calculation unit 206. The current value for locking the rotor from the line L
6 to the comparison unit 202.

The switch SW2 responds to the switch control signal provided from the switch control and magnetic pole initialization calculation unit 206, and drives the circuit provided with the signals provided from the switch control and magnetic pole initialization calculation unit 206 and the magnetic pole angle calculation unit 208. It is provided to the signal generator 204.

The comparison unit 202 compares the current signal input through the line L6 with the current current signal input through the line L4, calculates an error between them, and provides the error to the drive circuit control signal generation unit 204.

The drive circuit control signal generator 204 is the comparator 2
The error output from 02 is multiplied by the phase value input from the switch control and magnetic pole initialization calculation unit 206 or the magnetic pole angle calculation unit 208 to convert into a current value corresponding to each phase,
A voltage signal proportional to this value is output to the pulse width modulation circuit of the drive circuit 116 (FIG. 1) through the line group LG4.

FIG. 3 is a flow chart showing the steps performed in the switch control and magnetic pole initialization calculation unit 206, and FIG. 4 shows the current waveform of each phase for determining the phase of the initial current.

In step S10 of FIG. 3, when power is first supplied, SW1 and SW2 are switched to obtain the initial phase, and L6 and L7 are switched to SW2 in SW1.
In, L8 and L10 are respectively connected.

In step 12, the locking angle θ _L (LOC) is set in order to fix the rotor position at a known position.
(KING ANGLE) is designated in advance, and step S14
Locking current signal corresponding to theta _L in I _LC (L
OCKING CURRENT) is specified, and step S
In 16 this is provided to the drive circuit 116 (FIG. 1) through the line group LG4.

This will be described in detail with reference to FIG. FIG. 4 shows current waveforms I _U , I _V , and I of each phase provided to the stator windings U, V, and W of the AC servo motor.
Indicates _W. As described above, I _U , I _V , and I _W are 120
There is a phase difference of °, and there are six modes I, II, III, IV, based on the fact that the direction of the current supplied to each phase changes.
It can be classified into V and VI. First, in order to lock the current position of the rotor to a known position, such as position C (or F, I) indicated by an inverted triangle on the windings (U, V, W) of each phase of the stator. A rocking angle θ _L is specified, and a current corresponding to the specified rocking angle is output through the line L7.

In steps S18 and S20, the A-phase or B-phase signal of the general-purpose encoder input through the line group LG2 is analyzed, that is, whether the rotor is locked or not depending on whether the A-phase or B-phase pulse is generated. To judge. If there is an A-phase or B-phase pulse, it will not be locked yet. If the rotor is not locked, step S18 is performed,
When the rotor is locked, step S22 is executed.

In step S22, the initial phase of each phase current is determined when the rotor is locked. The initial phase θ _S is obtained by setting θ _L −90 °. For example, as shown in FIG. 4, the maximum torque is applied to the rotor when the locking currents I _U , I _V , and I _W for locking the rotor are supplied with currents such as the position C indicated by an inverted triangle. The initial phase of the current of each phase is the phase at position A or E.

In step S24, the initial phase θ _{S is set} to the drive circuit control signal generator 204 and the magnetic pole angle calculator 2
08 to provide.

In step S26, after the initial phase is provided, SW1 connects the lines L2 and L6, and the switch SW2 connects the lines L9 and L10.

When the rotor rotates while the initial phase of the current of each phase is determined, the magnetic pole angle calculator 208 (FIG. 2) measures the rotation angle of the rotor from the A or B phase signal of the general-purpose encoder. When the electric current is supplied by the rotation, the motor continuously generates the maximum torque.

[0043]

As described above, according to the present invention, not only the cost of the AC servomotor can be reduced by accurately detecting the rotational position of the rotor by using the inexpensive general-purpose encoder, but The efficiency can be improved. Further, since the magnetic pole can be detected even if the general-purpose encoder is provided at an arbitrary position unrelated to the magnetic pole position of the rotor, there is a magnetic pole matching step for matching the phase between the permanent magnet and the general-purpose encoder during the assembly of the AC servo motor. The number of encoder lines can be reduced and the productivity of the AC servo motor can be increased, and the various signal lines can be reduced to improve the reliability of the AC servo motor.

[Brief description of drawings]

FIG. 1 is a block diagram showing a drive starting device of an AC servomotor according to the present invention.

FIG. 2 is a detailed block diagram of a current controller in the AC servomotor shown in FIG.

FIG. 3 is a flowchart showing steps performed in the switch control and magnetic pole initialization calculation unit shown in FIG.

FIG. 4 is a diagram showing a current of each phase provided to a stator winding of an AC servo motor.

[Explanation of symbols]

 100 Motor Unit 102 Power Input Terminal 104 Rectifier Circuit 106 Inverter 108 Current Detecting Unit 110 Stator 112 Rotor 114 General Purpose Encoder 116 Drive Circuit 118 Current Control Unit 120 Position Control Unit 122 Speed Calculation Unit 124 Speed Control Unit 202 Comparison Unit 204 Drive Circuit Control signal generator 206 Switch control and magnetic pole initialization calculator 208 Magnetic pole angle calculator 210 Read only memory

Claims (4)

[Claims] 1. An AC servomotor comprising a stator and a rotor rotatably arranged inside the stator and applying magnetic flux to the stator, comprising: a current supplying a controllable current to the stator. Supply means; current detection means for detecting the magnitude of the current supplied from the current supply means to the stator to generate a current current signal; and monitoring the rotor for A, B and Z phase signals. A general-purpose encoder for generating; a position control means for generating a speed command signal in response to the A and B phase signals provided by the general-purpose encoder and a position command signal provided by a user; A provided by the general-purpose encoder Alternatively, speed calculation means for calculating the rotation speed of the rotor from the B-phase signal to generate the current speed signal of the rotor; current speed signal from the speed calculation means and position control means. Speed control means for comparing the speed command signals to generate a current command signal; comparing a current command signal from the speed control means and a current current signal from the current detecting means with a control signal for the current supply means. An AC servomotor drive starting device, comprising: a current control means provided by the general-purpose encoder, wherein the control signal uses a phase A or B signal provided by the general-purpose encoder, and the current control means is determined by calculating a magnetic pole angle of the rotor. . 2. The current control means generates a locking current for locking the rotor when an initial current is supplied to the stator, and uses the A and B phase signals from the general-purpose encoder, Magnetic pole initialization calculation means for generating an initial current phase signal for the locking after confirming the locking of the rotor; the initial current phase signal provided from the magnetic pole initialization calculation means and the A or B phase from the general-purpose encoder A magnetic pole angle calculating means for generating a changed current phase signal which is changed according to the rotation angle of the rotor by using the signal; a rocking current signal from the magnetic pole initialization calculating means and a current command signal from the speed control means. Is selectively input, the selected signal is compared with the current current signal from the current detecting means to calculate the error, and Means for selectively inputting the initial current phase signal from the conversion calculation means and the changed current phase signal from the magnetic pole angle calculation means, multiplying the error by the error, and providing a control signal to the current supply means. Item 2. An AC servomotor drive starting device according to Item 1. 3. The drive start device for an AC servomotor according to claim 2, wherein the general-purpose encoder is provided independently of the magnetic pole position of the rotor. 4. An AC servo comprising a stator, a rotor rotatably arranged in the stator to apply a magnetic flux, and an encoder for monitoring a rotational movement of the rotor to generate a feedback pulse. In the method of starting drive of a motor, a step of supplying a locking current having an arbitrary phase to a stator to lock the rotor after power is supplied, and a step of counting feedback pulses output from the encoder to lock the rotor. A step of confirming whether the rotor is locked, a step of supplying a driving current having a phase shifted by 90 ° from a phase of the locking current to the stator when the rotor is locked, and a feedback pulse output from the encoder. And detecting the rotation angle of the rotor by adjusting the phase of the drive current to the rotation angle of the rotor. A method of starting driving of an AC servomotor, which comprises changing the torque of the rotor to a maximum by changing the torque.