JPS59125413A - Servomechanism using alternating-current induction motor - Google Patents

Abstract

PURPOSE:To minimize an overrun by performing rated rotation drive except in a proximity area and automatic control in the proximity area according to a deviation function, and changing settings of each area easily with high efficiency. CONSTITUTION:An induction motor 1 is driven through a chopping circuit 5 and a rotating-direction control circuit 6 and the opening degree of a valve 3 is varied by its power shaft through a speed reducing mechanism 2. The opening degree of the valve 3 is detected by a current value detector 7 and the deviation (e) of the current value from a command is detected 8. The chopping circuit 5 is controlled on the basis of the deviation (e) through an absolute value amplifier, V/F converter 23, and controller 24. A comparator 25, on the other hand, decides on a forward and a backward rotation. An analog setter 26 sets the range of the proximity range in said control and the range is compared 25 with the deviation; and the automatic control which varies the frequency according to the extent of the deviation in the proximity area or the rated control which locks it and is irrelevant to deviation except in the proximity area is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a servo mechanism that performs position control such as flow rate control using an AC induction motor.

<Object of the Invention> The object of the present invention is to control the rotational speed of the induction motor in a close range in which position control is performed using a single-phase or polyphase induction motor, and the deviation of a feedback signal from a target value is preset. The object of the present invention is to provide a servo mechanism in which the induction motor is automatically controlled as a function of deviation by a transformerless cycloconverter, and in the non-proximity region, the induction motor is directly connected to a commercial AC power source and driven to rotate at the regular rating.

(Structure of the Invention) The servo mechanism of the present invention includes a V/F conversion means that converts a voltage indicating the amount of deviation into a frequency, and a control pulse generator that generates multiphase control pulses using the output pulses of the V/F conversion means. means, an AC switch element provided between the AC source input terminal and each terminal of the AC induction motor, and switching control means for simultaneously controlling on/off a plurality of corresponding AC switch elements using the control pulse. The present invention is characterized in that it has a setting device for setting the range of the proximity region, and a locking means for fixing the generation state of the control pulse when the range is in the non-proximity region.

<Embodiment 1> Hereinafter, the present invention will be described in detail regarding an electric valve control device using a single-phase induction motor.

FIG. 1 shows a circuit diagram of an embodiment of the present invention. The single-phase induction motor 1 is, for example, a capacitor motor, and is driven to rotate in both forward and reverse directions by switching winding terminals V or W, and its output shaft is connected to a valve via a gear reduction mechanism 2 having a constant reduction ratio. Change the opening degree of 3. The commercial AC power source 4 is inputted to the chopping circuit 5 from the input terminal R3, frequency-converted, and one by one, the rotation direction control circuit 6 selects either the V or W winding terminal.

A circuit example of the chopping circuit 5 and the rotation direction control circuit 6 is shown in FIG.
．． Reference numeral 14 forms a bridge circuit, in which the control input lines 11a and 133 of the first and third AC switch elements 1.13 on opposite sides of the bridge are connected in common and on/off controlled by the transistor 15, and the other parts of the bridge are The control input lines 12a and 14a of the second and fourth AC switching elements 12.14-, which are opposite sides of the transistor 1, are commonly connected.
On/off control is performed by 6. Each AC switch element connects the collector and emitter electrodes of a power transistor Q between the DC output terminals of a full-wave rectifier circuit consisting of four diodes D1 to D4, and connects its base electrode to a control terminal C.
It was derived as follows.

The clockwise terminal U of the motor M is a bidirectional thyristor 17.
is connected to motor terminal X through terminal V for counterclockwise direction.
is connected to the motor terminal X via the bidirectional silica 8. The gate electrodes of the thyristors 17 and 18 are connected to the outputs Gl, G2 of the ignition circuits 19 and 20.

The opening degree of the valve 3 is converted into an electrical signal by an opening degree detector 7 such as a potentiometer, while a control target value is introduced from a flow rate sensor or its data processing device, and a deviation detector 8
The deviation between the control target value and the current opening value is detected. The comparator 21 determines whether this deviation is positive or negative, and when it is positive, the output level is, for example, H (high) and drives the ignition circuit 19 to drive the motor 1 clockwise. However, when it is negative, it is L (low) and drives the ignition circuit 20 to drive the motor 1 counterclockwise.

On the other hand, the deviation signal is amplified by an absolute value amplifier 22 and then converted by a V/F converter (voltage-frequency converter) 23 into a pulse train having a frequency proportional to the input voltage. The control unit 24 uses the output pulse signal of the V/F converter 23 to generate two-phase control pulses P1. P
2, and the first pulse train P1 causes the transistor 1 to
5 is on/off controlled, and the transistor 16 is on/off controlled by the second pulse train P2. On the other hand, comparator 25
compares the output voltage let of the absolute value amplifier 22 and the set voltage E of the analog setting device 26, and when the absolute value le+ of the voltage e becomes equal to or higher than the set voltage E, that is, the opening degree of the valve changes from the target value to a predetermined value. It determines that it is out of range and issues a lock signal. At this time, the control signals PI and P2 are locked and do not change over time, so the transistors 15 and 1
6, one of them remains on and the other remains off. Note that the gain of the absolute value amplifier 22 or the conversion constant of the V/F converter 23 can be adjusted.

Next, the effect will be explained. On the left, where the output of the deviation detector 8 is a positive voltage and the ignition circuit 19 is driven, the bidirectional thyristor 17 is on, the thyristor 18 is off, and the motor M
is rotated clockwise. On the other hand, when the opening state of the valve changes and the deviation becomes a negative voltage, the ignition circuit 20 is driven, the thyristor 17 is turned off, the thyristor 18 is turned on, and the motor M is driven to rotate counterclockwise. .

When the deviation changes from zero, the output voltage of the absolute value amplifier 22 increases in proportion to it, and the pulse frequency that is the output of the V/F converter 23 increases.

The waveforms of the control pulse signals pl and p2 are square waves having a phase difference of 180 degrees, and do not reach H level at the same time. When transistor 15 is on, AC switching elements 11 and 13 are on, while the other set of AC switching elements 12 and 14 are off. next,
When transistor 16 is on, AC switch element 1
2 and 14 are turned on, while the other set of AC switch elements 11 and 13 are turned off. Due to this on/off operation, the motor M has transistors 15 and 1.
An alternating current defined by the on/off operation of 6 is supplied. Therefore, the motor M is rotated by the rotating magnetic field due to the frequency of the on/off operation of the transistors 15 and 16, regardless of the frequency of the commercial AC power source.

Motor rotation control using the above-mentioned converted frequency is as follows:
This is executed when the feed bank signal is within a predetermined range from the target value, and when it exceeds the predetermined range, a lock signal from the comparator 25 is input to the control unit 24, and the transistor 15
, I6 are kept on and off for a long time. In this locked state, AC switch elements 11 and 13 or 12 and 1
The AC input at terminal R3 is directly applied to the motor M through 4, and the motor M is driven at the rated rotational speed by the commercial AC frequency F1. When the feed bank signal approaches a predetermined range of the target value, the control unit 14 is activated, and control is performed to reduce the speed as the feed bank signal approaches the target value. That is, when the commercial AC frequency is Fl and the frequency of the control pulse signal is f, the output frequency F2 applied to the motor M from the power output terminal is F2 = f - Fl - - - - (11. Therefore, , Fl = 60 Hz, and f = 60 Hz, F2 = 0, and the rotation of the motor M stops. At this time, the voltage indicating the deviation is e = Q.

When e≠0, F2≠0, and the motor M is rotationally driven by the frequency F2 determined by equation (1), and rotates clockwise or counterclockwise depending on whether the voltage e is positive or negative.

FIG. 3 shows how the synchronous frequency of the motor M changes with respect to the voltage e indicating the deviation. In a close range where the absolute value tel of the voltage e is small with respect to the set voltage E (according to equation 11, the frequency of the power applied to the motor M changes,
In a non-proximity region where the absolute value let of the voltage e is larger than the set voltage E, the commercial AC power is directly applied to the motor 1.

<Embodiment 2> Next, another embodiment of the present invention using a three-phase AC induction motor will be described. FIG. 5 shows the contents of the chopping circuit 5, and FIG. 6 shows a waveform diagram of the control pulse signal.

The chopping circuit 5 includes three switching circuits 51.5
2.53, and each switching circuit has 3 as shown in FIG.
Opening and closing are sequentially controlled by phase square wave pulse signals. Input terminals A, B, C of each switching circuit 51.52.53
are commonly connected to each other and connected to commercial AC power supplies R, S, and T, the output terminal DSESF is the output terminal of the first switching circuit, and the output terminals E and F are connected to the motor terminals U, V, and W, and the second
The output terminals of the switching circuit are the motor terminals, E and F are the output terminals of the third switching circuit, and the motor terminals are W and U.
, F are connected to motor terminals W, U, and V, respectively. As shown in Figure 5, the configuration inside each switching circuit is as follows: AC switch elements 54, 55, and 56 are connected between terminals AD, BE, and CF, respectively. Transistors Q1, Q2 for on/off control,
The base and emitter electrodes of Q3 are connected to the transistor drive circuit 5.
7, and the three transistors Q1, Q2, Q3 are controlled to be turned on and off all at once by a control pulse signal Pi (i=1.2.3).

In such a configuration, as in the fateful two-phase embodiment, equation (1) holds true, and the frequency applied to the terminals U, V, and W of the motor 1 in the proximity region is controlled by the control pulses P+ and P.
2. It can be controlled by the frequency of P3. Also,
In this embodiment, the direction of rotation of the motor 1 can be changed simply by changing the phase relationship of the control pulse signals as shown in FIG. 6Cb1, for example. In the locked state in the non-proximity area, one of the control pulse signals P1, P2, and P3 is output, and the rotation direction of the motor 1 can be switched by switching the output control pulse signal. .

<Effects of the Invention> According to the present invention, physical quantities related to the position of the controlled object, such as speed and acceleration, can be automatically adjusted according to the magnitude of deviation, while using a conventional induction motor and a reduction mechanism with a constant reduction ratio. It is possible to perform control that changes over time. In addition, when the deviation is larger than the set value, the commercial AC power is directly applied to the induction motor, resulting in high efficiency, and the set value that separates the close area and non-close area can be adjusted arbitrarily depending on the purpose of use. Therefore, control devices for various uses can be commonly mass-produced, and furthermore, the set values can be easily changed by the user.

Furthermore, due to the relationship between the gain that amplifies the deviation and the set value,
The occurrence of discontinuity between the proximal region and the non-proximate region has the advantage that deceleration is effectively performed when the controlled object approaches the target value, and overrun can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, and Fig. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a circuit diagram showing a specific example of the chopping circuit 5 and the rotation direction control circuit 6 shown in the figure, and FIG. 3 is a waveform diagram showing the control pulse signals Pl and P2 of FIG. 1. FIG. 4 is an explanatory diagram of the operation of the present invention. FIG. 5 is a circuit diagram showing a chopping circuit according to another embodiment of the present invention. FIG. 6 shows the control pulse signals PI, P2. It is a waveform chart showing Pa. 1-Induction motor 2-Deceleration mechanism 3-Valve (controlled object) 4-AC power supply 5-Chopping circuit 6--Rotation direction control circuit 7-Valve opening detector (current value detector) 8-Difference detector 23 ... - V/F converter 24 - control unit 25 - comparator (deviation determining means) 11.12.
13.14.54.55.56--AC switch element PI, P2. pa---Control pulse signal patent applicant
M-System Giken Co., Ltd. Patent Attorney Nishi 1) New Figure 2 Figure 3 Figure 6 3

Claims (1)

[Claims] An AC power input terminal, an AC induction motor that displaces a controlled object, a switching circuit including a plurality of AC switching elements provided between the AC power input terminal and the AC induction motor terminal, and a target value and a controlled object. A deviation detector detects the deviation of the current value of a control unit that controls on/off of the AC switch element using a control pulse signal; a setting device that sets a range of a proximity region where the deviation is equal to or less than a predetermined value; and a setting device that fixes the generation state of the control pulse signal when the deviation is in a non-proximity region. and a locking means for changing the frequency of the power supplied to the AC induction motor in accordance with the magnitude of the deviation in the proximate region, and changing the frequency of the power supplied to the AC induction motor in the non-proximity region regardless of the magnitude of the deviation. A servo mechanism configured so that the current is supplied directly to the AC induction motor.