JPH0810992B2 - Method and apparatus for driving a synchronous AC servo motor - Google Patents

Description

The present invention relates to a method and apparatus for driving a synchronous AC servomotor, and more particularly to a synchronous AC servomotor capable of smoothly driving the servomotor when starting the servomotor. The present invention relates to a driving method and device.

[Prior Art] In the conventional synchronous AC servomotor control technology, a plurality of phase pulse signals (CS signals) are generated in synchronization with the rotation of the motor.
Two consecutive signals (A signal and B signal) used as reference pulses and 90 degrees out of phase, and an origin pulse signal (C
Signal) is used to obtain a position signal representing the rotor rotation position, that is, the magnetic pole position, and this position signal is converted into a digital or analog sine wave signal sin θ.
And the converted sine wave signal sin θ is multiplied by the torque command signal to obtain a current command signal used for controlling the drive current conducting circuit.

In the conventional technology, in controlling the servo motor, in order to generate the maximum torque, the energization of the phase current is controlled so that each phase current supplied to the motor has the same phase as each phase counter electromotive force. . It will be apparent to those skilled in the art that the position signal obtained by detecting the rotor rotational position using the encoder represents the phase of the phase back electromotive force.

When detecting the motor rotation position using an encoder,
An accurate rotor rotation position cannot be detected immediately when the motor is started. For example, when the rotor rotation position is detected based on the origin pulse output from the encoder, the rotor rotation position cannot be detected until the origin pulse is first output. Therefore, in this case, the phase of the phase current and the phase of the phase counter electromotive force cannot be matched until the origin pulse is detected, and the phase current will flow regardless of the rotor rotation position. Sometimes there is a problem that you can not get a smooth rotation.

Therefore, in order to solve such a problem at the time of starting, as shown in, for example, Japanese Patent Laid-Open No. 61-39885, the waveform of the origin pulse or the phase pulse signal rises or falls (hereinafter referred to as edge Until it detects), a step-like pseudo sine wave signal is created using a plurality of phase pulse signals, and when the edge of the origin pulse or the phase pulse signal is detected, it is generated based on the accurate position signal. A technique has been proposed in which a sine wave signal is supplied to smooth the rotation at startup.

[Problems to be Solved by the Invention] However, in this technique, control is performed by a position signal that does not change and is set based on a fixed position detected from the phase pulse signal until an edge is detected. Therefore, until the edge is detected (until the motor rotates 1 / p [p is the number of pole pairs of the motor]), control is performed using the same position signal that does not fluctuate, so speed control characteristics and torque control characteristics at startup Was not very smooth, and the rotation at startup was not always smooth. Also, with this technology, only a very rough position can be detected until the edge of the phase pulse signal from the start is detected, so in the worst case, until the motor makes 1 / p rotation [p is the number of pole pairs of the motor]. There is a problem that the current command signal based on the accurate position detection cannot be output, and the time until the accurate position detection is started becomes long.

An object of the present invention is to provide a driving method and apparatus for a synchronous AC servomotor that solves the problems of the above-mentioned conventional techniques.

[Means for Solving the Problems] In order to solve the above problems, the method of the present invention rotates the synchronous AC servomotor 1 as shown in FIGS. 1 to 3 showing an embodiment thereof. The position signal S representing the roller rotation position detected based on the output signal of the encoder 2 which outputs a signal synchronized with the signal is converted into a sine wave signal sin θ, and the sine wave signal sin θ is multiplied by the torque command signal V3 to obtain In the method of driving the synchronous AC servomotor that supplies the drive current based on the current command signals V4 and V5,
One cycle of V5 is divided into a plurality of modes, and the corresponding mode is detected based on the plurality of phase pulse signals CSU, CSV, CSW output from the encoder 2. Then, until the mode change is detected after the start-up, the number of the reference pulses En output from the encoder 2 is counted, and the count value is added to a predetermined initial value, or the subtraction from the initial value is performed. When the calculated value reaches the maximum count value or the minimum count value per mode, the calculated value is held. Then, the position signal is determined by the calculated value and the detected mode.

Further, in the device of the present invention, the rotor rotational position detecting means 100 for detecting the rotor rotational position based on the output of the encoder 2 for outputting the signal synchronized with the rotation of the synchronous AC servomotor 1 and outputting the position signal S is provided. Drive of a synchronous AC servomotor that includes a position signal S, converts the position signal S into a sine wave signal sinθ, and applies a drive current based on a current command signal V5 obtained by multiplying the sine wave signal sinθ with a torque command signal V3. In the apparatus, the rotor rotational position detecting means is constructed as follows.

The rotor rotational position detecting means of the present invention is a mode in which one cycle of the current command signal V5 is divided into a plurality of sections based on a plurality of phase pulse signals CSU, CSV, CSW output from the encoder 2 in a corresponding mode. Is detected between the mode detecting means 13 and the counter 14, which counts the number of reference pulses En output from the encoder 2 and is reset each time the mode detecting means 13 detects a change in the mode. The initial value setting means 16 for setting an initial value to a value between the maximum count value and the minimum count value of the reference pulse En, and the count value output from the counter 14 and the initial value are added or the count value is changed from the initial value. , A count limiter 18 that holds the calculated value when the calculated value output by the calculating means 17 reaches the maximum count value or the minimum count value, and the mode detection means 13 Switching means for outputting as the output of the detection counter 14 by supplying said change the output until the detection counter 14 in arithmetic unit 17 changes in
15 and position signal generating means 19 which receives the output of the mode detecting means 13 and the output of the calculating means 17 or the counter 14 and detects the rotor rotational position to generate the position signal S.

[Operation of the Invention] In the present invention, one cycle of the current command signal is divided into a plurality of modes, and the mode is detected from the relationship of the phase pulse signals. If the number of modes is n [a positive integer], correct position detection can be performed if the servo motor rotates 1 / np [p is the number of pole pairs] after starting at the latest. And until the change in the mode after startup is detected, in addition to the rough position found from the detected mode, in order to obtain the position signal based on the fine position determined by the counting process,
It is possible to obtain a current command signal that approximates a regular position signal, greatly improve the speed control characteristic and the torque control characteristic at the time of startup, and obtain smooth rotation.

In the counting process, add the reference pulse number output from the encoder to the preset initial value (1/2 of the maximum count value per mode to obtain the best result) or from the initial value Is subtracted. When the calculated value obtained by addition or subtraction reaches the maximum count value or the minimum count value per mode, the calculated value is held. Therefore, it is possible to prevent a significant difference between the actual position and the position detected by the counter process when the mode change is detected.

Further, in the device of the present invention, the method of the present invention can be implemented with a simple configuration, and in particular, the switching means 15 is provided and the arithmetic means 17 is provided with a counter until a mode change is detected at the time of startup.
Since the output of 14 is supplied and the count signal from the counter 14 is directly supplied to the position signal generating means 19 after the change of the mode is detected, the position signal at the time of start-up and after start-up can be obtained with a simple configuration. Obtainable.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a driving device when the present invention is applied to a three-phase synchronous AC servomotor. In the embodiment shown in FIG. 1, position detection is performed for two phases, U phase and V phase, and a phase current of three phases is supplied based on a current command signal of two phases. Shows the structure related to the rotor rotational position detecting means for one phase. 2 and 3 show the output waveforms of the respective parts of FIG.

In FIG. 1, an encoder 2 that outputs a plurality of signals synchronized with the rotation of the motor is attached to the motor 1. The encoder 2 detects the magnetic pole width of each phase of the motor and detects a phase pulse signal CSU of three phases that are out of phase with each other by equal angles.
It outputs CSV and CSW (FIGS. 2A to 2C) and a reference pulse En (FIG. 2E) having a pulse width in which 750 pulses are included in the pulse width of the one-phase pulse signal. The reference pulse can be created by appropriately utilizing the rising or falling of the A signal and the B signal whose phases are different by 90 degrees. As the encoder 2, either an optical encoder or a magnetic encoder may be used.

The reference pulse En output from the encoder 2 is a frequency-voltage conversion circuit 3 that converts the rotation speed of the motor into a voltage value.
Is converted into a speed detection signal V1 via a signal, and the deviation between the speed detection signal V1 and the speed command signal V2 is input to a speed amplifier 4 which performs a proportional-integral operation and converted into a torque command signal V3.
The torque command signal V3 is multiplied by a digital sine wave signal Sinθ obtained by converting the position signal S output from the rotor rotational position detecting means 100, which will be described in detail later, into a digital sine wave signal to obtain a digital amount. The current command signal V4 of is obtained.
The digital amount current command signal V4 is converted into an analog amount current command signal V5 via a digital-analog converter (D / A converter) 5. In the present specification, the term “current command signal” means the analog command current command signal V5 unless otherwise specified.

The current command signal V5 is input to the drive current conducting circuit 6,
The energizing circuit 6 is a current command signal V5 for the U phase and a current command signal V output from the control circuit for the V phase (not shown).
Based on 5 ', three phase currents are applied to the motor. The drive current conducting circuit 6 is a two-phase to three-phase conversion circuit 7 that produces a three-phase current command signal based on the two-phase current command signals V5 and V5 '.
And the pulse width modulation by amplifying the deviation between the three-phase current command signal and the current detection value from the current detector 10 that detects the phase current value.
A current amplifier / PWM circuit 8 for outputting a PWM waveform signal, a transistor circuit having a power transistor for supplying a motor with a current supplied from a power source (not shown) based on the PWM waveform signal, and a drive circuit for driving the transistor circuit And a power transistor circuit 9 composed of

Reference numeral 100 is a rotor rotation position detecting means for detecting the rotor rotation position of the U phase of the motor 1, and 12 is a sine for converting the position signal S output from the rotor rotation position detecting means 100 into a digital sine wave signal Sinθ. It is a wave conversion circuit. In FIG. 1, a portion surrounded by a dashed line (speed amplifier 4, frequency-voltage conversion circuit 3, sine wave conversion circuit 12 and rotor rotational position detecting means 100 is a CPU of a microcomputer.
It is composed by.

In this embodiment, as shown in FIG. 2, phase pulse signals CSU and CS
Using the rising or falling (edge) of U and CSW, one cycle of the current command signal V5 is divided into six equal sections. In the present specification, each of the six sections set by using the edges of the phase pulse signal is referred to as a “mode”, and is referred to as mode 0, mode 1 ... Mode 5 for convenience.

The mode detection means 13 determines which mode the current mode is, from the relationship between the three phase pulse signals, specifically, the combination of the polarities or levels of the phase pulse signals. If the mode is detected from the combination of the levels of the phase pulse signals in this manner, the rough rotor position can be detected even when the motor 1 is started (immediately after the control power is turned on). The mode detection means 13 outputs a mode detection signal S1 indicating the detected mode.

The counter 14 counts the reference pulse En output from the encoder 2 and outputs the count value to the switching means 15 as a count signal S2. The counter 14 is reset when the rising of the reset signal R input when the power is turned on and the mode detection signal S1 input from the mode detection means 13 indicates a mode change (mode change). The reference pulse is counted for each mode. For example, when the resolution M of the encoder 2 is 6000 (pulse / Rev), the multiplication number Q is 1, and the pole pair number P of the motor 1 is 4, the reference pulse number N per mode is N = MQ / 6P = 6000 × 1/6 x 4 = 250 (pelse / Mode). Therefore, if the counting is started from the beginning of the mode, the count signal S2 output from the counter 14 indicates an accurate position from the beginning of the mode.

The switching means 15 is a counter at the rising edge of the reset signal R.
The count signal S2 from 14 is output from the output terminal OUT2, and when the mode detection signal S1 is input from the mode detection means 13, the count signal S2 is output from the output terminal OUT1. When the motor 1 is started, that is, when the power is turned on, or when the starting switch is separately provided, the rising portion of the reset R signal is input to the switching means 15, so that the switching means.
15 supplies the count signal S2 to the calculating means 17. Computing means
Reference numeral 17 adds the count signal S2 and the initial value signal S3 representing the initial value output from the initial value setting means 16 or subtracts the count signal S2 from the initial value signal S3. That is, the calculating means 17 performs an operation of adding the count value counted by the counter 14 and the initial value set by the initial value setting means 16 or subtracting the count value from the initial value. In this specification, this process is called a count process.

The initial value set by the initial value setting means 16 is an appropriate number between the maximum count value and the minimum count value per mode, and in the present embodiment, the maximum count value of the reference pulse En per mode is the above-mentioned. Therefore, the initial value is set to 1/2 of the maximum count value, that is, 125. The initial value and setting do not have to be set to 1/2 of the maximum count value, but a number close to 1/2 of the maximum count value is preferable. This is because the position detection error at the time of startup can be reduced.

The count limiter 18 supplies the calculation signal S4 corresponding to the calculation value as it is to the position signal generating means 19 described later until the calculation value of the calculation means 17 reaches the maximum count value (250) or the minimum count value (0). When the calculated value reaches the maximum count value or the minimum count value, the counting operation of the counter 14 is stopped, or the calculated value (maximum count value or minimum count value) at that time is held and held in the position signal generating means 19. Continue to supply value.

The position signal generating means 19 includes a table indexing portion, and the mode detecting signal S1 output from the mode detecting means 13
And the count signal S2 output from the output terminal OUT2 of the switching means 15 or the calculation signal S output from the count limit 17
Based on 4 ', the rotor rotational position is set, and the position signal S corresponding to the rotor rotational position is retrieved and output from the table index section. And the sine wave conversion circuit 12 is built-in
A sinusoidal wave signal sinθ of a digital value is output from the sinθ table according to the position signal S.

[Operation of the Embodiment] The operation of the embodiment of FIG. 1 will be described with reference to FIG.
FIG. 3 shows the manner in which the rotor is started from the state in the range of mode 0, mode 2 and mode 4 in regions I to II.
Shown in I.

The case where the rotor of the motor 1 is rotated in the direction in which the count value of the counter 14 is up-counted, that is, the count value is increased will be described below. The calculation means 17 is the initial value set in the initial value setting means 16, 125 and the counter 1 in this embodiment.
Performs the operation of adding the count value of 4.

In FIG. 3, region I shows the state when the power of the motor 1 is in the range of the mode 1 and the motor is started when the rotor is in the range of mode 1. When the reset signal R rises at time t1, the switching means 15 supplies the count signal S2 (FIG. 3a) representing the count value output from the counter 14 to the calculating means 17, and the calculating means 17 has an initial value (125). The signal S4 representing the calculated value obtained by adding the count value to () is output.
Therefore, the position detected at time t1 at startup is
It is regarded as the position of the 125th pulse from the beginning of mode 0, that is, the center position of mode 0. As a result, the time
At t1, the position signal S at the position of the 125th pulse from the beginning of mode 0 is output and converted into a sine wave signal by the sine wave conversion circuit 12, and the value of the current command signal at the position of the 125th pulse from the beginning of mode 0 Is output from the D / A converter 5. Then, after that, the normal sine wave waveform shown by the broken line is shifted (shifted to the left in FIG. 3c) until the output of the calculation means 17 displays the maximum count value of 250.
Waveform is output.

When the calculated value reaches the maximum count value of 250, the count limiter 18 holds the calculated value (250). Time t2 to t3 when the calculated value is held and a constant current command signal is output
While the counter 14 continues counting during this period, the operation value is limited by the action of the count limiter 18.

At time t3, when the mode detection means 13 detects a mode change from mode 0 to mode 1, a mode detection signal
S1 is input to the switching means 15, the counter 14 and the position signal generating means 19, the counter 14 is reset and starts counting from 0, and the switching means 15 outputs the count signal S2 from the output section OUT1 to the position signal generating means 19 as it is. Supply. Therefore, after time t3, the current command signal has a regular sine wave waveform because accurate position detection is performed. When the count limiter 18 operates in this manner, the current command signal is held at the same value as the current command signal at the tip position in the next mode, so that the switching between the start-up operation and the normal operation is performed extremely smoothly. Be done.

Region II in FIG. 3 shows a state in which the motor is started from the latter half position of the mode 2.
In this case, since the starting position is behind the central portion of the mode 2 (125th pulse), a change in the mode is detected before the calculated value of the calculating means 17 reaches the maximum count value, and at the time t6, the normal change is detected. Switches to the current command signal with a sine wave.

Region III in FIG. 3 shows a state in which the mode 4 is activated from the first half position. The operation in this area is the same as that in the area I, and therefore the description thereof is omitted.

In the present embodiment, as can be seen from the waveform of FIG. 3, since a current command signal is obtained by utilizing a part of the sine wave waveform even at the time of starting, the step-like deduction command as in the prior art. The rotor can be smoothly rotated as compared with the case of using the corrugation. The current command waveform at startup is a waveform in which the normal current command waveform is out of phase except when it is started from the position corresponding to the initial value set by the rotor. Since the mode is divided into two modes, even in the worst case, if the rotor of the motor rotates 1 / 6P (P is the number of pole pairs), the mode change is detected and a normal current command waveform is output. Therefore, in the worst case, 1 / P
The speed control characteristic and the torque control characteristic of the motor at the time of start-up can be remarkably improved as compared with the conventional device that does not switch to the regular current command signal until the motor rotates.

Further, as seen in the area II of FIG. 3, when the count limiter 18 is activated from a position where it does not operate, a slightly large change occurs when switching to the current command signal of the regular sine wave waveform. Occurs, but since it is a moment, there is almost no problem in performance.

In the above explanation, the case of starting the motor was explained first, but if some kind of abnormality occurs during operation and a stop signal is output from the abnormal state detector (not shown) and the motor is stopped, the reset signal is reset again. It will be apparent to those skilled in the art that the same operation will be performed when the switch is turned on and restarted.

In the device of the above embodiment, the output of the couter 14 is switched by the switching means 15, and the current command signal is generated by commonly using the position signal generating means 19 and the sine wave conversion circuit 12 both at the time of starting and after starting. Therefore, the rotor position detecting means 10
The configuration of 0 can be simplified.

In the above-described embodiment, the calculation of adding the counter value of the counter 14 to the initial value is performed, but the calculation operation (down count) of subtracting the count value from the initial value may be performed. For example, when the direction of motor rotation is reversed, down counting is performed. In this case, the count limiter 18 holds the calculated value when the calculated value reaches the minimum count value (0).

In the above-described embodiment, the 6-section mode is adopted, but the number of modes can be further reduced. In that case, if an edge of another pulse signal output from the encoder is used in addition to the edge of the phase pulse signal, a finer mode can be obtained. If an encoder that outputs phase pulse signals of four phases as shown in FIG. 4 is used as the encoder, it can be divided into eight modes, and the speed of position detection can be further increased.

In the above embodiment, the portion surrounded by the alternate long and short dash line in the embodiment of FIG. 1 is constituted by the CPU processing, but it goes without saying that some or all of the constituent requirements of this portion can be constituted by a hard circuit. Is.

In the above embodiment, the current command signals for the U-phase and V-phase are used to supply the phase currents for the three phases.
It goes without saying that a current command signal may be obtained for each of the W phases and the phase current may be supplied based on each current command signal.

[Effect of the Invention] According to the method of the present invention, one cycle of the current command signal is divided into a plurality of modes, the mode is detected from the relationship of the phase pulse signals, and the change of the mode is detected after starting. Is
In addition to the rough position found from the detected mode,
Since the position signal is obtained based on the fine position determined by the counting process, it is possible to obtain the current command signal that is close to the normal position signal, and it is possible to greatly improve the speed control characteristic and the torque control characteristic at the time of starting. , You can get a smooth rotation. Further, according to the method of the present invention, if the number of modes is n [a positive integer], correct position detection can be performed if the servo motor rotates 1 / np [p is the number of pole pairs] after starting at the latest. Particularly, according to the method of the present invention, the calculated value obtained by adding the reference pulse number output from the encoder to the predetermined initial value or subtracting the reference pulse number from the initial value is the maximum count value or the minimum count per mode. Since the calculated value is held when the number is reached, it is possible to prevent the actual position when the mode change is detected from being significantly different from the position detected by the counting process.

Further, according to the device of the present invention, the method of the present invention can be implemented with a simple structure, and in particular, the switching means is provided to supply the output of the counter to the arithmetic means until a mode change is detected at startup. Since the count signal from the counter is directly supplied to the position signal generating means after the change of the mode is detected, it is possible to obtain the position signal at the time of activation and after activation.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an apparatus for carrying out a method for driving a synchronous AC servomotor according to the present invention, and FIG. 2 shows a current command signal divided into 6 modes by 3-phase pulse signals. FIG. 3 is a waveform diagram showing a state, FIG. 3 is a signal waveform diagram of a signal output from each part of the embodiment of FIG. 1, and FIG. 4 shows a state in which the current command signal is divided into 8 modes by a 4-phase pulse signal. It is a wave form diagram to demonstrate. 1 ... Servo motor, 2 ... Encoder, 3 ... Frequency-voltage conversion circuit, 4 ... Speed amplifier, 5 ... Digital-
Analog converter, 6 ... Drive current energizing circuit, 12 ... Sine wave converting circuit, 13 ... Mode detecting means, 14 ... Counter,
15 ... switching means, 16 ... initial value setting means, 17 ... computing means, 18 ... count limiter, 19 ... position signal generating means, 100 ... rotor rotation position detecting means.

Claims (4)

[Claims] 1. A position signal representing a rotor rotational position detected based on an output signal of an encoder that outputs a plurality of signals synchronized with the rotation of a synchronous AC servomotor, is converted into a sine wave signal, and the sine wave signal and In a driving method of a synchronous AC servomotor that supplies a drive current based on a current command signal obtained by multiplying with a torque command signal, one cycle of the current command signal is divided into a plurality of modes and output from the encoder. The corresponding mode is detected based on the multiple phase pulse signals, and the number of reference pulses output from the encoder is counted and the count value is set to a predetermined initial value until the mode change is detected after startup. Performs an operation of adding or subtracting from the initial value, and holds the operation value when the operation value reaches the maximum count value or the minimum count value per mode. The driving method of a synchronous AC servomotor, characterized in that determining the position signal by said mode detects that the operation value each. 2. The method of driving a synchronous AC servomotor according to claim 1, wherein the initial value is half the maximum count value. 3. A rotor rotation position detecting means for detecting a rotor rotation position based on an output of an encoder for outputting a signal synchronized with the rotation of a synchronous AC servomotor and outputting a position signal, the position signal being a sine signal. In a drive device for a synchronous AC servomotor that converts a wave signal and applies a drive current based on a current command signal obtained by multiplying the sine wave signal and a torque command signal, the rotor rotational position detecting means is Based on a plurality of phase pulse signals output from the encoder, a mode detecting unit that detects the corresponding mode from the mode in which one cycle of the current command signal is divided into a plurality of sections, and the reference pulse output from the encoder A counter that counts a number and is reset each time the mode detecting means detects a change in mode; and a counter that counts during one mode. Initial value setting means for setting an initial value to a value between the maximum count value and the maximum count value of the quasi-pulse, and the count value output by the counter and the initial value are added, or the count value from the initial value And a count limiter that holds the calculated value when the calculated value output by the calculating unit reaches the maximum count value or the minimum count value, until the mode detection unit detects a change in mode. Switching means for supplying the output of the counter to the arithmetic means and detecting the change and outputting the output of the counter as it is, and the rotor rotation position using the output of the mode detecting means and the output of the arithmetic means or the counter as inputs. Of a synchronous AC servomotor, characterized by comprising position signal generating means for detecting the position signal and generating the position signal. Operated device. 4. The synchronous AC servomotor according to claim 3, wherein the initial value set in the initial value setting means is half the maximum count value. Drive.