JPS61288790A - Motor control circuit - Google Patents

Abstract

PURPOSE:To enable to smoothly control to position a motor by switching a DC gain and a frequency characteristic in response to the output of a phase compensator. CONSTITUTION:A controller first turns ON a switch element 7, and applies a speed deviation signal from a speed deviation signal generator 5 through a low pass filter 9 to a power supply circuit 10. When a speed command then reduces to zero, the element 7 is opened, a switch element 8 is closed, and a phase compensator 11 supplies a position error signal to the power supply circuit 10. Since the absolute value of the output of the compensator 11 is the forward voltage VD or higher of diodes 18, 19 at this time, a DC gain and a gain of low frequency band are low, and a DC motor is not abruptly accelerated. When the absolute value of the output of the compensator 21 reaches the voltage VD or lower, the DC gain and the gain of the low frequency band increase to accurately control to position the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a motor control circuit that controls the speed and positioning of a DC motor.

3/, Prior Art In recent years, with the increasing demand for high-speed mechanism operation and improved positioning accuracy in mechanism drives for information devices such as electronic typewriters and printers, DC motors and motor control circuits have come to be used. □It's starting to turn sour.

An example of the conventional motor control circuit mentioned above will be described below with reference to the drawings. FIG. 6 shows the configuration of a conventional motor control circuit. .

In FIG. 6, 1 is a movable member, 2 is a DC motor that drives the movable member 1, 3 is provided with a terminal a and a terminal, and is connected directly or indirectly to the DC motor 2, and as the DC motor 2 rotates. This is a position detector that applies two periodic position signals having a phase difference of π/2 to terminals a and 2, respectively. 4 is provided with a terminal C1 terminal d, a terminal e, and a terminal f, and inputs a position pulse, which is two pulse signals generated based on the above two position signals and applied to a terminal C9 terminal d, and inputs a position pulse to the above position pulse. Based on this, in accordance with a series of preset control procedures, a rotation direction command indicating the direction in which the DC motor 2 should rotate is output to terminal e, and a speed command, which is a digital signal indicating the target speed at which the DC motor 2 should rotate, is output to terminal f. It is a control device that

5 is proportional to the difference between the actual rotational speed of the DC motor 2 and the target speed indicated by the speed command applied to the terminal f,
This is a speed deviation signal generator that generates a speed deviation signal having a polarity corresponding to the rotation direction command applied to the terminal e, and outputs the two position pulses to the terminal C9 and the terminal d. 6 is a positioning control state in which the DC motor 2 is positioned by turning off the switch element 7 and turning on the switch element 8 when the speed command applied to the terminal f indicates zero; This switch switching circuit turns on the switch element 7 and turns off the switch element 8 when the command indicates a value other than zero, thereby setting the DC motor 2 in a speed control state in which the rotation speed is controlled.

10 is a power supply circuit that supplies power to the DC motor 2 using a chopper method. Reference numeral 21 denotes a phase compensator that compensates for the position signal applied to terminal a so that the motor control circuit obtains sufficient stability. The position error signal that is the output of the phase compensator 21 is transmitted to the power supply circuit 1o via the switch element 8, and the output of the speed deviation signal generator 6 is transmitted to the power supply circuit 1o via the switch element 7 and the low-pass filter 9. 1o will be informed.

Next, the circuit configuration of the phase compensator 21 will be explained. 2
6 is an operational amplifier, the non-inverting input of which is grounded, and the inverting input connected to the output via a resistor 25. Terminal a is connected to an operational amplifier 26 via a resistor 22 and a capacitor 23.
The terminal a is connected to the inverting input of the terminal a through the resistor 24, respectively.

The operation of the motor control circuit configured as described above will be explained below. The motor control circuit drives the movable member 1 from the current position where the movable member 1 is positioned by applying speed control to the DC motor 2 to rotate it, moves it to a target stop position, and positions the movable member 1. .

In the following explanation, the above two position signals applied to terminal a and terminal S are respectively V, , Vb, and the position pulse based on the above position signal vb applied to terminal d is Pd, (
Let v9 be the speed deviation signal that is the output of the fault M filter 9, and v8 be the position error signal that is the output of the switch element 8.

When the control device 4 outputs a speed command to the terminal quantity and a rotation direction command to the terminal e without switching, the switch changeover circuit 6 turns the switch element 7 on and the switch element 8 off, and the motor control circuit turns on. The speed control state is entered, and the DC motor 2 starts rotating in the direction indicated by the rotation direction command. The position detector 3 detects the sixth position as the DC motor 2 rotates.
As shown in the figure, position signals V a and V b, which are two pseudo sine waves having a phase difference of π/2, are output. The speed deviation signal generator 6 is connected to the terminal C9 and the terminal d, respectively.
It outputs two position pulses based on the two position signals va and vb, and also outputs the speed deviation signal. The speed deviation signal becomes a speed deviation signal v9 whose ripple component is attenuated by the low-pass filter 9, and is transmitted to the power supply circuit 1o. In the power supply circuit 10, the polarity of the speed deviation signal v9 is negative, that is, the polarity is negative.

The DC motor 2 is accelerated when the actual rotational speed of the current motor 2 is lower than the rotational speed indicated by the speed command, and conversely, the DC motor 2 is decelerated when the polarity of the speed deviation signal v9 is positive. Therefore, the speed is controlled so that the speed deviation signal v9 becomes zero, that is, the actual rotational speed of the DC motor 2 becomes equal to the rotational speed indicated by the speed command. Pd is input, speed commands are output one after another according to a preset control procedure, and the DC motor 2 is caused to drive the movable member 1.

When detected, zero is output to the speed command mentioned above. The switch changeover circuit 6 detects that the speed command has become zero, and turns the switch element 7 off and the switch element 8 on, thereby setting the positioning control state. The power supply circuit 10 accelerates the DC motor 2 when the polarity of the position error signal 8 which is the output of the phase compensator 21 via the switch element 8 is negative, and accelerates the DC motor 2 when the polarity is positive. Slow down. Therefore, the DC motor 2 is stopped and positioned at the point where the position error signal v8 becomes zero, that is, one point in FIG. 6.

In the positioning control state, the motor control circuit of the above configuration example constitutes a servo control loop. The open loop gain frequency characteristic of the above servo control loop is shown at N in FIG. Generally, in a servo control loop, the open loop gain in the low frequency band is set sufficiently high in order to suppress the influence of disturbances. The response of the motor control circuit having the characteristic indicated by N in FIG. If the open loop gain is set high in the low frequency band in order to suppress the influence of As a result, as shown at point M, the DC motor is accelerated excessively, making it impossible to perform smooth positioning and resulting in a problem that high accuracy cannot be achieved in the actual stopping position of the movable member. Furthermore, when using a DC motor with a low resonance point as shown at point R in Figure 7, the open loop gain frequency characteristic will be as shown in Figure 7 O, and the response will be as shown in Figure 8. However, there was a problem in that the DC motor oscillated. Furthermore, in order to prevent the above oscillation, if the gain is reduced from the characteristic shown in Figure 7 O to the characteristic shown in P, the response will be as shown in Figure 9, and the positioning error will be large and the effect on disturbance will be small. This has the problem of increasing the size of the motor, making it extremely difficult to design an appropriate motor control circuit.

In view of the above problems, the present invention realizes smooth positioning control, does not cause oscillation even when the resonance point of the DC motor is low, is less affected by external disturbances, and can position movable members with high precision. It provides a motor control circuit.

A foolproof way to solve problems 10.

In order to solve the above problems, the motor control circuit of the present invention is a phase compensator equipped with a switch circuit that receives a position signal as input and performs phase compensation, and also switches the DC gain and frequency characteristics in stages by detecting the output voltage. The output of the phase compensator supplies the input of the power supply circuit in the positioning control state.

According to the above-described configuration, the gain of the phase compensator is suppressed to a low value when the absolute value of the output of the phase compensator is equal to or higher than a preset value, and the absolute value of the output is adjusted to the writing setting. If the value is below, the above gain becomes large, so
When switching from speed control to positioning control, the gain of the phase compensator is low, so the output of the phase compensator does not become an excessively large value, and the DC motor is smooth without being subjected to unnecessary excessive acceleration. positioning is performed. In addition, when positioning is completed, the gain is kept low in the band near the resonance point of the DC motor, and the gain is kept high in the low frequency band.

Therefore, it does not cause oscillation and is less affected by disturbance9.
Highly accurate positioning can be achieved.

Embodiments Hereinafter, motor control circuits according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of a motor control circuit in one embodiment of the present invention. In FIG. 1, the same cylindrical parts as in the conventional example shown in FIG. 6 are given the same numbers, and their explanations will be omitted.

11 is a phase compensator. The circuit configuration of the phase compensator 110 will be explained below. 12 is an operational amplifier, its non-inverting input is grounded, and its inverting input is connected to the output of the operational amplifier 12 via a resistor 16, and also to the output of the operational amplifier 12 via a resistor 19 and a diode 18. ing. The anode of the diode 19 is connected to the cathode of the diode 18, the cathode of the diode 19 is connected to the anode of the diode 18, and a capacitor 20 is connected in parallel with the diode 18. The terminal & of the position detector 3 is connected to the operational amplifier 12 via a resistor 13 and a capacitor 14.
It is connected to the inverting input of the inverter 1 and also connected to the inverting input via the resistor 16.

The operation of the motor control circuit configured as described above will be explained below. In the following explanation, two periodic position signals applied to terminal a and terminal S are va, vb,
Based on the position signal vb, the position pulse applied to the terminal d is Pd, the output of the phase compensator 11 is v,1, the position difference signal which is the output of the switch element 8 is v8, and the output of the low-pass filter 9 The speed deviation signal is v9, diode 1
8. Let the forward voltage of the diode 19 be VD. The motor control circuit in this configuration example controls the speed of the DC motor 2 to drive the movable member, and when it detects the fall of the position pulse Pd shown at point D in FIG. Positioning at a point is the same as in the conventional example described above, and the speed control method is also the same as in the conventional example. Positioning control in this embodiment will be explained below.

In the phase compensator 11, when the absolute value of the output v11 is less than the voltage VD, both the diode 18 and the diode 19 are turned off, and the phase compensator 11 is configured with a resistor 13, a capacitor 137, a sensor 14, a resistor 16, and a resistor 16. Since either the diode 18 or the diode 19, which is a combination of the compensation circuit and the low-pass filter composed of the resistor 17, the capacitor 2o, and the resistor 16, is turned on, the arrow C in FIG.
As shown in , the DC gain and the gain in the low frequency band decrease, and B
The frequency characteristics are shown below. In FIG. 3, the control device 4
When detecting the fall of the position pulse Pd shown at point D, the speed command output to the terminal is set to zero, and the motor control circuit is switched from the speed control state to the positioning control state.

At this time, the absolute value of the output v11 of the phase compensator 11 is E
As shown in the dot, the voltage is higher than the voltage VD, so B in FIG.
As shown in FIG. 3, the DC gain and the gain in the low frequency band are low, and the absolute values of the output v11 and the output v8 at that time do not become excessively large, so the DC motor 2 is not accelerated rapidly and the gain in the low frequency band is low. As shown, position control can be entered smoothly. When the DC motor 2 approaches point F in Figure 3, the absolute value of the output (147, -7) becomes less than the voltage VD, and the DC gain and the gain in the low frequency band decrease as shown in Figure 2A. As a result, the positioning is performed at point F in FIG. 3 with high precision. FIG. 4 shows the open loop gain frequency characteristic in the positioning control state. In FIG. 4, even when the DC motor 2 has a resonance point at a low frequency as shown at point G,
Since the open loop gain is set sufficiently low at the resonance point, oscillation does not occur. Moreover, in the state where the position is at point F in FIG. 3, that is, the above output v1. When the absolute value of is less than the voltage VD, the open-loop gain has the frequency characteristics shown in Figure 4F, and since the gain is sufficiently high in the low frequency band, the influence of disturbance can be kept extremely low, and the DC The motor 2 is positioned with high precision. Furthermore, at point E in FIG. 3, the absolute value of the output ■111 is the voltage ■. Under the above conditions, the open loop gain has the frequency characteristics shown in FIG. 4I, and since the gain is sufficiently low in the low frequency wave band, smooth positioning is achieved without excessive acceleration of the DC motor 2. 167,
.

It is something.

As described above, according to this embodiment, by providing a phase compensation circuit that switches the DC gain and frequency characteristics in stages by detecting the output voltage, oscillation occurs even when a DC motor with a low resonance point is used. It is resistant to external disturbances and can position the above-mentioned DC motor with high precision, and because it can switch from speed control to positioning control with a smooth response, it can also achieve high precision in the actual stopping position of movable members. It is something.

In this embodiment, the DC motor 2 is a DC motor with a low resonance point, but the DC motor 2 may be a DC motor with a sufficiently high resonance point, and the capacitor 2° may be omitted.

Further, in this embodiment, the power supply circuit 1o is a chopper type circuit, but the power supply circuit 1o may be a power amplifier circuit.

Effects of the Invention As described above, the present invention provides a phase compensation means having a switch circuit that performs phase compensation by using a position signal and detects an output voltage to switch the DC gain and frequency characteristics in stages. As a result, even when using a DC motor with a low resonance point, it does not cause oscillation and is resistant to external disturbances.
Since the above DC motor can be positioned with high precision and with smooth response,
High accuracy can also be achieved in the actual stopping position of the movable member. Furthermore, the present invention can be realized at low cost with an extremely simple configuration, and enables the use of an inexpensive DC motor with a low resonance point, so it has extremely great utility value in industry, and its effects are tremendous. It is.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a motor control circuit in an embodiment of the present invention, Fig. 2 is a frequency characteristic diagram of a phase compensator, Fig. 3 is a waveform diagram of essential parts in an embodiment of the invention, and Fig. 4 is an open loop gain characteristic diagram of an embodiment of the present invention, FIG. 5 is a block diagram of a conventional motor control circuit, FIG. 6 is a waveform diagram of main parts in the conventional example, and FIG. 7 is an open loop gain in the conventional example. Characteristics 17A-1, FIG. 8, and FIG. 9 are waveform diagrams of main parts in the conventional example, respectively. 1...Movable member, 2...DC motor,
3...Position detector, 4...Control device,
5...Speed deviation signal generator, 6...Switch switching circuit, 9...Low pass filter, 1o...Power supply circuit, 11゜21・・・・・・
...Phase compensator.

Claims (3)

[Claims] (1) A movable member, a DC motor that drives the movable member, and two periodic positions that are directly or indirectly connected to the DC motor and have a phase difference of π/2 from each other as the DC motor rotates. a position detection means for generating a signal; the two position signals, a speed command which is a digital signal representing a target rotation speed at which the DC motor should rotate, and a rotation direction command representing a rotation direction in which the DC motor should rotate; is input, the two position signals are waveform-shaped to generate position pulses, which are two pulse signals with a phase difference of π/2, and the difference between the actual rotational speed of the DC motor and the speed command is calculated. means for generating a speed deviation signal that is proportional and has a polarity corresponding to the rotational direction command; and a phase compensation means that uses the position signal as input to perform phase compensation and detects the output voltage to switch the DC gain in stages. , a power supply means for supplying power to the DC motor; a control device that receives the position pulse as an input and outputs a rotation direction command and a speed command according to a preset control procedure;
A motor control circuit comprising a selection means for selecting either the speed deviation signal or the output of the phase compensation means and inputting the selected one to the power supply means. (2) The phase compensation means includes a switch circuit that detects the output voltage and switches the gain and frequency characteristics of the phase compensation circuit stepwise.
Motor control circuit described in section. (3) The motor control according to claim 2, wherein the switch circuit includes a diode, a capacitor connected in parallel to the diode, and a resistor connected in series to the diode. circuit.