JPH11341872A - Method for starting sensorless synchronous servomotor and controller thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a starting method of sensorless synchronous servomotor which assures reliable start of operation with a low level current. SOLUTION: This starting method is applied to the starting method, in which after a rotor 3 is fixed to the predetermined rotation starting position P with a fixed magnetic field, the rotor 3 is rotated. Before the rotor 3 is fixed to the normal rotation starting position P, the fixed magnetic field in the direction different from the fixed magnetic field is generated, and the rotor 3 is once fixed to a position Q which is different from the normal rotation starting position P. Thereafter, the fixed magnetic field of a stator coil 2 is switched to fix the rotor 3 to the normal rotation starting position P.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a control device for starting a sensorless synchronous servomotor used for various devices, for example, for driving a small motor or a grindstone forming tool of a grinding machine for processing small precision products. The present invention relates to an activation method and an activation control device suitable for controlling a motor for use in a vehicle.

[0002]

2. Description of the Related Art In the case of miniaturizing a servomotor, a further miniaturization can be achieved by using a servomotor that does not use a sensor of a shaft rotation position.
Closed loop control is also possible by performing the speed control based on the rotational speed detected from the back electromotive force of the motor.
Since the sensorless servomotor has an unknown origin position, it is necessary to fix the magnetic pole position (or phase angle) of the rotor at a predetermined rotation start position at the time of startup. Therefore, before the rotation, a fixed magnetic field is applied to the stator coil 52 as shown in FIG. As shown in FIG.
Even when 3 is not at the normal rotation start position, by applying a fixed magnetic field, the rotor 53 is rotated to the rotation start position as shown in FIG.

However, depending on the rotational position of the rotor 53 at the time of stop, even when a fixed magnetic field is applied, no torque may be generated or the generated torque may be smaller than the static friction resistance at the start of rotor rotation. Cannot fix the rotor 53 at the rotation start position. That is, as shown in FIG.
In the case where the magnetic pole No. 3 is at a position 180 ° opposite to the rotation start position or in the vicinity thereof, the rotor 53 and the stator coil 52 have the same polarity, so that torque zero and torque shortage occur, and the rotor 53 rotates. Can not. If the frictional resistance of the motor shaft is large or the starting torque of the motor is small,
The angle range α in which the start-up failure occurs is large. In such a case, even when the rotation of the magnetic field of the stator coil 52 starts, the behavior of the rotor 53 is unstable, and in many cases,
Causes loss of synchrony.

Conventionally, as a solution to this problem, a current for generating a fixed magnetic field is supplied at least 10 times the rated current, the number of motor poles is increased, or a preload of the bearing is reduced so that the range of zero torque is as narrow as possible. , Or when the start of the motor fails, the start is repeated again. However, these methods are not preferable in terms of motor life, miniaturization of the motor, rotation accuracy, and reliable control of the motor. For example, in a grinding machine that grinds a raceway of a miniature bearing, attempts have been made to employ a sensorless synchronous servomotor for rotationally driving a grindstone forming tool in order to reduce the size of the apparatus. But,
In order to realize high-precision machining, it is necessary to start the drive motor of the grinding wheel shape forming tool accurately and stably, and the bearing that supports the grinding wheel shape forming tool is sufficiently preloaded to increase the support rigidity. The need to increase the motor speed, and the lack of an appropriate motor start-up method, has hindered the realization of the use of a sensorless synchronous servomotor.

An object of the present invention is to provide a starting method and a control device that can start a sensorless synchronous servomotor reliably and with a low current. Another object of the present invention is to use a sensorless synchronous servomotor for a grindstone forming tool driving motor, without lowering the preload of the bearing, so that it can be started reliably and at a low current, It is an object of the present invention to reduce the size of a grinding wheel shape forming device of a grinding machine by employing a sensorless synchronous servomotor and to realize precision machining.

[0006]

A method of starting a sensorless synchronous servomotor according to the present invention comprises generating a fixed magnetic field in a stator coil to fix a rotor at a predetermined rotation start position, and then generating a rotating magnetic field in the stator coil. In the start-up method of rotating the rotor by rotating the rotor at the rotation start position, a fixed magnetic field in a direction different from the fixed magnetic field is generated in the stator coil before the rotor is fixed at the rotation start position, and the rotor is moved to a position different from the rotation start position. This is a method in which the magnetic field is fixed once, and then the fixed magnetic field of the stator coil is switched so that the rotor is fixed at the rotation start position. According to this method, by fixing the rotor position at a position different from the normal rotation start position for the first time, the rotor moves to the first predetermined position and stops. Rotor is in the first predetermined position and 1
If it is on the opposite side by 80 degrees, that is, if it is at a position where the torque becomes zero or insufficient with respect to the first predetermined position, the stop is maintained without moving at that position. For this reason, when the fixed magnetic field is applied to the next normal rotation start position to fix the rotor, the rotor can reliably avoid the position where the torque is zero or the torque is insufficient, and a reliable and stable starting operation can be obtained. Further, the magnetic field fixed current at this time may be a current that generates a torque greater than the static friction resistance when the rotor rotates, and the current value can be dramatically reduced.

A start-up control device for a sensorless synchronous servomotor according to the present invention comprises: a power supply for applying a voltage for generating a rotating magnetic field after applying a voltage for generating a fixed magnetic field to a stator coil; And a switching circuit for switching the connection state of the phase of the stator coil and switching the direction of generation of the fixed magnetic field. According to this activation control device, at the time of activation, a voltage for generating a fixed magnetic field is applied from the power supply means to the stator coil. This allows the rotor
It moves to a position corresponding to the fixed magnetic field and stops. When the rotor is at a position 180 ° opposite to the position corresponding to the fixed magnetic field, the rotor stops at that position. Thereafter, the switching circuit switches the phase between the power supply means and the stator coil, and generates a fixed magnetic field in a different direction from the first time in the stator coil. Thereby, the rotor is fixed at a position corresponding to the fixed magnetic field after the switching. At this time, the rotor can surely avoid the position where the torque is zero or the torque is insufficient. Therefore, by setting the stop position after the switching as the rotation start position, it is possible to reliably stop at the rotation start position. Thereafter, a voltage for generating a rotating magnetic field is applied to the stator coil from the power supply means, and the rotor rotates. Thus, according to this activation control device,
Before fixing the rotor to the normal rotation start position, control for fixing the rotor to another position is performed by switching the phase connection state by a switching circuit provided between the power supply means and the stator coil. As the device, a device which applies a generally used fixed magnetic field generation voltage and then applies a rotating magnetic field generation voltage can be used.

In the method of the present invention, the servomotor is
It may be a driving source that rotationally drives a grinding wheel shape forming tool of the grinding machine. By adopting this starting method as the driving source of the grinding wheel shape forming tool in this way, the grinding wheel shape can be formed with high accuracy, and high precision grinding can be performed. Also in the apparatus of the present invention, the servomotor may be a drive source for rotationally driving the grindstone forming tool of the grinding machine. By employing this starting device as the drive source of the grinding wheel shape forming tool of the grinding machine, the grinding wheel shape can be formed with high accuracy, and high precision grinding can be performed.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIG. In the starting method of this embodiment, the sensorless synchronous servomotor 1 includes, as the stator coil 2, U-phase coils u1, u2, V-phase coils v1, v2, and W-phase coils w1, This is an example in the case where the rotor 3 is a two-pole permanent magnet having three sets of coils w2. The connection method of the stator coil 2 is a star connection. This starting method is based on the premise that a fixed magnetic field is generated in the stator coil 2 to fix the rotor 3 at the normal rotation start position P, and then a rotating magnetic field is generated in the stator coil 2 to rotate the rotor 3. And Here, the stator magnetic field at the start of rotation is a magnetic field in which the position of U-phase coil u1 is the S pole and the position of U-phase coil u2 is the N pole. These U-phase coils u1 and u2 have N pole and S
It is assumed that the position corresponding to each pole is the normal rotation start position P of the rotor 3.

In this starting method, the position of the rotor 3 is temporarily fixed at a position Q different from the normal rotation start position P for the first time. That is, a fixed magnetic field in a direction different from the fixed magnetic field at the start of rotation is generated in the stator coil 2. The first fixed position Q may be within the angular range excluding the range α where the torque becomes zero or insufficient at the rotation start position P and the range 180 ° opposite to the range α. In the example of FIG. This is a position within the range of the angle ranges θ1 and θ2. Here, as shown in FIG. 3B, the rotor 3 is connected to the v-phase coils v1 and v2.
The position where the S pole and the N pole correspond to the first fixed position Q, respectively. As described above, when the fixed magnetic field of the stator coil 2 is generated in the direction to be the first fixed position Q, the rotor 3 in the arbitrary direction moves to the first fixed position Q and stops. When the rotor 3 is located in the range of zero torque or insufficient torque β with respect to the first fixed position Q, as shown in FIG.
Maintain the same position.

Thereafter, the rotor 3 is moved to the normal rotation start position P.
The fixed magnetic field of the stator coil 2 is switched so as to be fixed to. At the time of this switching, since the rotor 3 is always at the first fixed position Q or at a position 180 ° opposite to the first fixed position Q, the position where the torque is zero or insufficient is reliably avoided, and the rotor 3 is reliably moved to the normal rotation start position P. And stop (FIG. 1D). Thereafter, an alternating voltage is applied to the stator coil 2 to generate a rotating magnetic field, and the rotor 3 is rotated.

As described above, before fixing the rotor 3 at the normal rotation start position P, the rotor 3 is once fixed at another position Q, and then fixed at the normal rotation start position P. And stably fixed at the regular rotation start position P,
Rotation can be started. Moreover, the magnetic field fixed current at this time only needs to be a current value that generates a torque greater than the static friction resistance at the start of the rotation of the rotor 3, and the current value at the time of startup can be drastically reduced.

FIG. 2 shows an example of a start-up control device for the sensorless synchronous servomotor. The terminals of each phase U, V, W of the power supply means 4 are connected to the coils u1, v1, w1 of each phase of the motor 1 by wires 5-7. The power supply unit 4 is a unit that outputs a three-phase AC current whose frequency and voltage are controlled and outputs a DC voltage for generating a fixed magnetic field in the stator coil 2 when the motor 1 is started.
A switching circuit 8 for switching the connection state of the phases between the power supply means 4 and the stator coil 2 is provided on the wirings 6 and 7 of the two phases among the wirings 5 to 7. The switching circuit 8 includes branch wirings 6a, 6b,
7a, 7b, and relays CR1, CR2 for switching the connection state between the branch wirings 6a, 6b and between the branch wirings 7a, 7b (only the relay contacts are shown in the figure, and the relay coils are not shown). It is composed of These relays CR1 and CR2 are controlled by a command from the switching control means 10. The switching control means 10 is a means for turning on or off the relays CR1 and CR2 for a predetermined time only for a predetermined time in response to a predetermined motor start command.
In the switching control means 10, the relays CR1 and CR2 may have their functions as an ON delay time, an ON state maintaining time, and the like. Further, in the switching circuit 8 shown in the figure, appropriate switching means may be provided instead of the relays CR1 and CR2.

The operation of the activation control device will be described. FIG.
(A) shows a connection state at the time of resetting, that is, a state at the time of applying a fixed magnetic field at the time of normal rotation start, and (B) shows a connection state before resetting. Usually, at reset,
A fixed magnetic field voltage is applied between the U and V phases and between the W and V phases of the stator coil 2. Therefore, when the magnetic field is fixed for the first time, the relays CR1 and CR2 are turned on, the WV phase is switched, a voltage is applied, and a fixed magnetic field is generated with a phase different from that at the time of reset. Next, the relays CR1 and CR2 are turned off, the WV phase is restored, a voltage is applied, a fixed magnetic field at the time of reset is generated, and the relay is activated.

FIG. 3 shows a startup sequence. When the motor start signal ((a) in the figure) is turned on, the relays CR1 and CR2 are turned on in response to this ((b) in the figure). After the relay operation stabilization time T1 from the ON operation, the operation mode (FIG. 10C) becomes the first rotor fixed mode M1. The rotor fixed mode M1 has a predetermined positioning time T
After the OFF delay time T3, the relays CR1, C
R2 turns off. Thereafter, after the relay switching stabilization time T4, the operation mode is the second rotor positioning mode, that is, the normal rotor fixed mode M2 in which the positioning is performed to the normal rotation start position P. This rotor fixed mode M2 lasts for a predetermined reset time T5. Thereafter, the mode is the motor rotation mode. After the open loop control mode M3, the motor rotation mode
The closed loop control mode is set to M4. The motor control by the open loop is performed only for a predetermined time T6 (until the motor rotation speed rises to a rotation speed that can be accurately detected by the back electromotive force), and thereafter, the motor control mode by the closed loop is set.

FIG. 4 shows a head portion of a grinding wheel shape forming apparatus provided with the sensorless synchronous servomotor of the starting control system. The grinding wheel shape forming apparatus 20 is provided in a grinding machine for grinding a bearing ring of a rolling bearing, and forms a rotating grinding wheel 21 (FIG. 2B) with a grinding wheel shape forming tool 22 made of a diamond disk. Or to dress. The grindstone shape forming apparatus 20 includes a main shaft 23 on which a grindstone shape forming tool 22 is mounted and a rotor 3 of a motor 24.
Is a built-in motor type. Spindle 23
Is a stepped shaft having a large diameter at the mounting end of the grindstone forming tool 22. The large diameter portion 23a and the rear end of the normal diameter have bearings 26 and 27 such as angular ball bearings. Accordingly, the motor is rotatably installed in the spindle case 28. The spindle case 25 includes a dovetailed guided portion 28a.
And is installed on a frame (not shown) of the grinding machine.
The motor 24 includes a stator coil 2 installed in a spindle case 28 and a rotor 3 made of a permanent magnet provided on the outer periphery of the main shaft 23, and has the same configuration as the motor 1 shown in FIG. . As the activation control device for the motor 24, the one described with reference to FIG. 2 is used.

By employing the starting method of the present invention for the motor 24 serving as a driving source of the grinding wheel shape forming tool 22, the bearings 26 and 2 for supporting the grinding wheel shape forming tool 22 are provided.
Even if the preload of 7 is given enough, there is no step-out etc.
It can be started reliably and with low current. Therefore, it is possible to form or dress the grinding stone shape with high accuracy, and to perform high-precision grinding.

[0018]

According to the method and apparatus for starting the sensorless synchronous servomotor of the present invention, before fixing the rotor to the normal rotation start position, the rotor is temporarily fixed to a position different from the normal rotation start position, and thereafter, Since the rotor is fixed at the normal rotation start position and a rotating magnetic field is generated, the rotor can be started reliably and with a low current. In addition, when the starting control device generates a fixed magnetic field at the time of starting and fixes the rotor, the switching circuit switches the phase between the power supply means and the stator coil, thereby moving the rotor to a position different from the normal rotation start position. Once the rotor is fixed, control is performed to fix the rotor at the normal rotation start position, so that the rotor can be changed to a fixed rotor position at startup with a simple configuration.

[Brief description of the drawings]

FIG. 1A is a front view of a conceptual structure of a servomotor to which a starting method according to an embodiment of the present invention is applied, and FIG.
(D) are explanatory diagrams of the activation process.

FIG. 2A is a circuit diagram showing a circuit switching state at the time of reset of a start-up control device of a sensorless synchronous servomotor according to an embodiment of the present invention, and FIG. 2B is a circuit showing a circuit switching state before the reset. FIG.

FIG. 3 is a timing chart showing an operation sequence of the activation control device.

FIG. 4A is a cutaway side view of a grindstone shape forming apparatus in which the starting method and the starting control device are applied to a drive source, and FIG. 4B is a plan view thereof.

FIG. 5 is an explanatory diagram showing a method of starting a conventional sensorless synchronous servomotor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Motor 2 ... Stator coil 3 ... Rotor 4 ... Power supply means 8 ... Switching circuit 22 ... Grindstone shape forming tool P ... Regular rotation start position Q ... 1st rotor stop position

Claims (4)

[Claims] 1. A method for starting a sensorless synchronous servomotor, comprising: generating a fixed magnetic field in a stator coil to fix a rotor at a predetermined rotation start position, and then generating a rotating magnetic field in the stator coil to rotate the rotor. Before fixing the rotor at the rotation start position, a fixed magnetic field in a direction different from the fixed magnetic field is generated in the stator coil to temporarily fix the rotor at a position different from the rotation start position. A method of starting a sensorless synchronous servomotor that switches a fixed magnetic field of a stator coil so as to be fixed at a start position. 2. A power supply for applying a voltage for generating a rotating magnetic field after applying a voltage for generating a fixed magnetic field to the stator coil, and a power supply provided between the power supply and the stator coil. And a switching circuit for switching the connection state of the two phases to switch the direction of generation of the fixed magnetic field. 3. The method according to claim 1, wherein the servomotor is a drive source that rotationally drives a grindstone forming tool of a grinding machine. 4. The start-up control device for a sensorless synchronous servomotor according to claim 2, wherein the servomotor is a drive source that rotationally drives a grindstone forming tool of a grinding machine.