JPS58123391A - Automatic controller for synchronous motor for servo motor - Google Patents

Abstract

PURPOSE:To maintain a following speed of an automatic control system constant by increasing the gain of a current control system only during the period that a motor for a servo motor is in an accelerated or decelerated state. CONSTITUTION:One or more of amplifiers contained in an automatic control circuit, e.g., the amplifiers in a current control system and a position control system are set to variable gain regulation type, and an analog switch 17 is controlled by an amplifier gain control signal L, thereby increasing the gain of the amplifier. The following speed of an automatic control system can be maintained constantly irrespective of the variation in the counterelectromotive force by increasing the gains of the current control system or the current control system and the position control system only during the period that the motor for the servo motor is in accelerated or decelerated state.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to an improvement in an automatic control device for a synchronous motor for a servo motor.

Background of the 121 Technology Conventionally, permanent magnet type DC motors have been mainly used as servo motors, but recently there has been a tendency to use permanent magnet rotating field type synchronous motors. The reason for this is (a) because it is a brushless motor, there is no risk of wave interference, (b) there is no problem with commutator wear, and (c) the rotor is robust, making sudden acceleration and deceleration easy. It is possible and
In addition to the benefits of easy adjustment of dynamic balance, (d) By using a angular position sensor that accurately detects the angular position of a resolver, etc., the rotor of a synchronous motor can always accurately detect the presence of field poles. The angular position of the detected field pole is monitored, and a multiphase AC voltage is generated that generates a composite magnetic field at a geometric position corresponding to 7i electrical angle phase advance from the detected angular position of the field pole. This is because a technique has been developed to constantly maintain the internal phase difference angle of a synchronous motor at 100 by supplying an alternating voltage to the stator, making it easier to control a synchronous motor as a servo motor. That is, the torque T of the synchronous motor is: where ■ is the applied voltage, E is the back electromotive force, X is the inductance of the stator that generates the rotating magnetic field, and a is the internal phase difference angle.

However, when a power supply voltage having a frequency and phase such that the internal phase difference angle δ is always 100 is applied, sin δ is always “1”, and the stator inductance depends on the power supply voltage frequency, and the back electromotive force E
is proportional to the rotor speed, that is, the power supply voltage frequency, and the effects of stator inductance X and back electromotive force E are canceled out, so torque T can be abbreviated as T = K + V = K2 I This is because it depends entirely on the value of the power supply voltage, that is, the rotor current, and can be controlled extremely easily.

On the other hand, the control method of a permanent magnet rotating field type synchronous motor as a servo motor is based on a position control system, and generally a speed control system and a current control system are added as minor loops to this.

That is, a position command signal that instructs the driven mechanical system to move to a desired position is used as a basic signal, and this basic signal is combined with a position feedback signal representing the actual position of the driven mechanical system detected by a position sensor. The deviation between this and a speed feedback signal representing the speed of the servo motor is taken as a current command signal, and this and the current feedback signal I11. representing the current of the servo motor are used as a current command signal. ．． .

The deviation from the current value is used as a current control signal, and this current control signal is used to control the current of the servo motor, that is, the value of the power supply voltage.

(3) Prior art and problems An example of the control method of a permanent magnet rotating field type synchronous motor as a servo motor in the prior art outlined above will be explained in some detail with reference to Figures 1 and 2. Explain. In FIG. 1, A is a position command signal, B is a position feedback signal, which are compared by a comparator circuit 1,
The deviation is amplified by the position control system amplifier circuit 2 and applied as the speed command signal C to the comparator circuit 3, where it is compared with the speed feedback signal applied at the same time. It is amplified and applied as a current command signal E to a comparison circuit 5, which is compared with a current feedback signal F applied at the same time, and the deviation thereof is amplified by a first-class control system amplifier circuit 6 to produce a current control signal Q.
is applied to the synchronous motor power supply control circuit 7 to control the inverter 8, which is the AC power source of the synchronous motor 8M, to control the AC voltage supplied to the synchronous motor SM. In FIG. 1, TG is a speed sensor, 9 is a position sensor, 10 is a current sensor, and 11 is a resolver.

As shown in FIG. 2, the current control signal G is a signal H having the same phase as the angular position of the field pole detected by the resolver 11 serving as an angular position sensor, that is, Acos ω1, and is 7 electrical angles ahead of the angular position of the field pole. i.e. As
1nωt, and Q'5in(ωt-±π
) is converted to With this three-phase exchange one word, the first
If the inverter 8 shown in the figure is controlled and the generated voltage is supplied to the synchronous motor SM, the amplitude will be proportional to the current control signal G and the frequency will always be proportional to the rotor speed at that time. Correspondingly, a rotating magnetic field 4) sinω1 with an electrical angle advance from the angular position of the field pole is generated.
(a) From startup to stop, the magnetic field generated by the stator and the field poles of the rotor are always in synchronization, not only during acceleration, constant speed, and deceleration periods, but also during stoppage, and (b) the generated torque is , regardless of the rotational speed, control proportional to the current control signal given by the automatic control system is possible.

By the way, in order to supply current to the motor, a voltage that compensates for the back electromotive force is required, and this back electromotive force increases and decreases in proportion to the speed of the motor. Furthermore, the torque generated by the electric motor is divided into a component that covers external loads and various losses, and a component that accelerates the rotor.

Therefore, in the automatic control system described above, the following speed should change depending on the magnitude of the back electromotive force, that is, the magnitude of the rotational speed, and the presence/absence and magnitude of acceleration. In order for this change to be infinitesimal, the gain of the automatic control system must be infinite, or it is industrially unrealistic to manufacture an automatic control system with an infinite gain. Needless to say. Therefore, when allowing the above-mentioned change in the following speed, the deviation between the position command signal and the position feedback signal, in other words, the geometric gap between the desired position of the driven control system and the actual position. The servo mechanism becomes unstable and has defects that are difficult to image as a servo mechanism. This defect is a decisive cause of reducing the accuracy of servo systems, especially when multiple servo systems need to work together.
This is a shortcoming that must be resolved by all means.

(4) Object of the invention The object of the present invention is to have an automatic control circuit based on a position control system, to which a speed control system and/or current control system as a minor loop is added, and this control circuit In an automatic control device for a synchronous motor for a motor, the following speed is proportional to the output of the rotor and is related to the magnitude of the rotor speed, the presence/absence of acceleration, etc. Provides an automatic control device for a servo motor synchronous motor that is constant and does not cause position errors between multiple servo systems, especially when multiple servo systems need to work together. It is to be.

(5) Structure of the Invention The structure of the present invention is based on (a) a position control system as the main control system, to which a speed control system and/or current control system as an additional control system is added as a minor loop. (b) The amplitude is determined in proportion to the output signal of this automatic control device and corresponds to the rotational speed of the rotor detected by a separately provided angular position sensor such as a resolver. The frequency is determined by the angular position sensor and the angular position of the rotor field pole detected by the angular position sensor is, for example, medically or electrically angularly advanced than the angular position of the rotor field pole detected by the angular position sensor. A device (source control signal valve generator
ii''), ?・) has a quality power source such as an inverter that is controlled based on the output signal of this control signal light generator, and (d) its size is the same as that of the automatic control device described above. is proportional to the output signal of Generally, in an automatic control device that supplies two-phase or three-phase AC voltage as a power supply voltage to the stator of a synchronous motor for a servo motor, (e) a circuit that detects whether the motor for the servo motor is in an acceleration or deceleration state is installed. (g) This circuit has a circuit that generates a signal that has a constant relationship with the absolute value of the rotational speed of the servo motor motor only during the period when this circuit is detecting the acceleration/deceleration state. When the circuit is in a state of accelerated deceleration and has means for controlling the gain of at least one of the amplifiers included in the automatic control device described in (a) above, generally an amplifier in a current control system, based on the output signal of the circuit. The gain is increased, and the gain is decreased when the speed is constant. The goal is to keep the speed constant.

The idea of the present invention is that (a) when the motor is in an acceleration/deceleration state, a part of the torque generated by the electric motor is used for acceleration/deceleration, and (b) the torque used for acceleration/deceleration is reversed. Since it changes according to the electromotive force, (c) during this acceleration/deceleration period, by increasing or decreasing the current that generates the acceleration/deceleration torque that changes according to this back electromotive force, it is possible to achieve stability, which is the object of the present invention. (d)
Furthermore, we thought that it would be more effective to control the gain of the automatic control system rather than simply supplying additional current.

(6) Embodiment of the invention Hereinafter, with reference to the drawings, an embodiment of the invention will be described.
An automatic control device for a synchronous motor for a servo motor will be explained.

First, an amplifier gain control signal generation circuit as shown in FIG. 3 is provided. In the figure, 12 is an acceleration/deceleration state detection circuit, and 13 is an absolute value generation circuit that outputs the absolute value of the output of a speed sensor TG such as a tachometer generator 11L. this is,
It has a function to abstract whether the direction of rotation is clockwise or counterclockwise. 14 is an analog switch. 15 is a reference frequency oscillator, and 16 is a width modulation circuit. This extractor gain control signal generation circuit outputs a pulse train signal having a pulse width proportional to the rotor rotational speed, that is, the value of the back electromotive force, as the amplifier gain control signal only during acceleration/deceleration states. Ru.

Next, one or more of the amplifier circuits included in the automatic control circuit having the same configuration as shown in FIG. 1, such as a current control system amplifier circuit and a position control system amplifier circuit, are shown in FIG. 4. The analog switch 17 is controlled by the amplifier gain control signal, and the gain K of this amplifier circuit is determined as follows: 2 where K is the gain when the analog switch is in the "OFF" state.

R2 and R3 are the resistance values of the resistors R2 and R3 shown in FIG.

increases as follows. In the figure, 18 is an operational amplifier, which in this embodiment is a current error amplifier.

, ::・1 The input signal M of this amplifier gain control □ circuit is the output signal of the comparison circuit 5 shown in FIG. 1, and the output signal N is the input signal of the synchronous motor power supply control circuit 7.

As explained above, according to this embodiment, the gain of the current control system or the current control system and the position control system increases only during the period when the servo motor motor is in the acceleration/deceleration state, and the gain of the current control system and the position control system increases, so that the change in the back electromotive force is Regardless 1. The tracking speed of the automatic control system can be kept constant.

(7) As described in detail, the present invention has an automatic control circuit based on a position control system, to which a speed control system and/or current control system as a minor loop is added. In an automatic control device for a synchronous motor for a servo motor, which generates an angular position and has a frequency that is proportional to the output of this control circuit and corresponds to the momentary rotational speed of the rotor detected by an angular position sensor. , the following speed is constant regardless of the magnitude of the rotor speed, the presence or absence of acceleration, etc., and especially when multiple servo systems need to work together, the It is possible to provide an automatic control device for a synchronous motor for a servo motor in which position errors do not occur.

[Brief explanation of the drawing]

y41 is a block diagram of an automatic control device for a synchronous motor for a servo motor in the prior art, and FIG. 2 is a synchronous motor power supply control circuit in FIG. 1. Third
4 are block diagrams of an amplifier gain control signal generation circuit and an adjustable gain type amplifier circuit that constitute an automatic control device for a synchronous motor for a servo motor according to an embodiment of the present invention. A: Position command signal, B: Position feedback signal, C: Speed command signal, D:
... Speed feedback signal, E ... Current command signal, F ... Current feedback signal, G
......-Flow control signal, 1,3゜5...Comparison circuit, 2...Position control system amplifier circuit, 4...
... Speed control system amplifier circuit, 6 ... Current control system amplifier circuit, 7 ... Synchronous motor power supply control circuit, 8
・・・・・・AC power supply (inverter), 9・・・・・・
Position sensor, 10...Current sensor, 8M...
...Synchronous motor, TG...Speed sensor, U,
■, W...U phase, ■ phase, iW mutual trust, H...
...Signal with the same phase as the field pole, K...Signal with electrical angle phase advance at the field pole, 11...Angular position sensor resolver), L...Amplifier gain Control signal, 12...
...Deceleration state detection circuit, 13...Absolute value generation circuit, ...Analog switch, 15...
Reference frequency oscillation, 16... Width modulation circuit, 17.
...Analog switch, ...Operation amplifier, R,, R2, R3...Resistor, M, N...
Input/output signals of adjustable gain amplifier circuit.

Claims (1)

[Claims] It has an automatic control device in which a speed control system and/or a current control system as an additional control system are added to a position control system as a main control system, and has an amplitude proportional to an output signal of the automatic control device, Generates a plurality of alternating current signals having a frequency corresponding to the rotation speed detected by the angular position sensor, a phase having a certain relationship with the angular position detected by the angular position sensor, and having a certain mutual phase difference. In an automatic control device for a synchronous motor for a servo motor that is supplied with power from an AC iiL source that is controlled by an output signal of the power control signal generator, the automatic control device has a power control signal generator. It has a circuit that detects a deceleration state, and a circuit that generates a signal that has a constant relationship with the absolute value of the rotational speed of the rotor of the electric motor only while the acceleration/deceleration state detection circuit is operating, An automatic control device for a synchronous motor for a servo motor, comprising means for controlling the gain of at least one amplifier included in the automatic control device based on an output signal of the circuit.