JPH06284769A - Apparatus for controlling constant speed of dc motor - Google Patents

Abstract

PURPOSE:To obtain an apparatus for controlling the constant speed of a DC motor, which can control the speed of a motor at a constant value without the effect of the change of the motor current and has the excellent circuit efficiency. CONSTITUTION:A CD motor 1 undergoes chopper driving with a switching means 2. A driving signal VD is converted into the trigger signal with a delay circuit 5. The signal is made the driving signal for a sample hold circuit 6. Thus, an induced voltage Vs, which is proportional to the motor speed, is detected based on the terminal voltage of the motor, whose level is converted with an amplifier circuit 4. The reference triangular wave of an oscillating circuit 9 is compared with the output voltage of a proportional integrating circuit 10, wherein the induced voltage Vs is changed so that the voltage agrees with an applied voltage corresponding to a target speed E0 in a comparator 11. Thus, the duty ratio of the driving signal VD is set.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC motor constant speed control device for controlling a motor speed in drive control of a DC motor.

[0002]

2. Description of the Related Art FIG. 6 shows, for example, "motor and circuit technology",
(Published September 25, 1989), Engineering Book Co., Ltd., P9
FIG. 2 is a circuit diagram showing the conventional DC motor constant speed control device shown in FIG. 1, in which 1 is an armature resistance R and an induced voltage E.
Is a DC motor represented by an equivalent circuit, and 20 is a DC motor 1
, 8 is an input terminal to which a target voltage E0 proportional to the target speed is applied, R0 is connected between the input terminal 8 and the operational amplifier output terminal f,
Two resistors KR with the operational amplifier input terminal d as the intermediate point h
1, a variable resistor divided into KR, R1 is a fixed resistor connected between the operational amplifier output terminal f and the DC motor 1 and the operational amplifier input terminal e, 21 is connected in parallel to the fixed resistor R1, and the operational amplifier 20 is connected at startup. A capacitor to be protected, I is a current flowing from the operational amplifier output terminal f through the fixed resistor R1 to the DC motor 1, and I / K is a feedback current similarly flowing from the operational amplifier output terminal f through the variable resistor R0 to the input terminal 8.

Next, the operation will be described. Variable resistance R0
By setting the resistance ratios between the end point g and the middle point h of R and between the middle point h and the end point of R: R1, a feedback current I / K that is I / K times the motor current I flows through the variable resistor R0. Where K
Is a constant obtained by R0 / (R + R1). At this time, the potential of the operational amplifier input terminal d becomes E0 + R × I, and since the operational amplifier input terminals d and e have the same potential due to the concept of the virtual common point of the operational amplifier 20, the variable resistance R0
Under the same condition that the resistance ratio of (1) and the resistance ratio of (armature resistance R) :( fixed resistance Ri) are the same, the voltage at the operational amplifier input terminal d becomes equal to the motor terminal voltage. Therefore, a voltage drop of (resistance KR between the end point g and the intermediate point h of the variable resistor R0) × (feedback current IK) is subtracted from the voltage of the operational amplifier input terminal d, and (armature resistance R) × (motor Subtracting the voltage drop of the current I) reveals that the target voltage E0 and the induced voltage E are equal. Therefore, the output current of the operational amplifier 20 changes so that the induced voltage E matches the target voltage E0 with respect to changes in the target speed and the motor speed, so that the motor speed can be kept constant at the target speed.

[0004]

Since the conventional DC motor constant speed control device is constructed as described above, when the motor current I changes due to the change of the target speed or the change of the load applied to the DC motor 1, the electric power is changed. The loss changes, and the armature resistance value changes according to the change in the self-heating temperature due to the change. Therefore, the resistance ratio between the armature resistance R and the fixed resistance R1 also changes, and the difference generated between the set resistance ratio R: R1 of the variable resistance R0 appears as the difference between the motor speed and the target speed. . Also, the operational amplifier output terminal f and the fixed resistor R
1. Since the motor current I continuously flows in the series circuit of the DC motor 1, the power supplied from the power supply is constant, but the required power of the DC motor 1 changes depending on the speed, and thus in the control region. , DC motor 1 from power supply
There is a problem that the circuit efficiency is deteriorated because the remaining part after subtracting the power consumption of is the power loss in the operational amplifier 20 and the fixed resistor R1.

The present invention has been made in order to solve the above-mentioned problems, and the motor speed can be controlled to be constant without being affected by the change of the motor current of the invention of claim 1, and the circuit efficiency can be improved. An object of the present invention is to obtain a DC motor constant speed control device with good performance. It is another object of the present invention to provide a DC motor constant speed control device capable of preventing the control from becoming uncontrollable even when the target speed or the motor speed changes abruptly. A third object of the present invention is to provide a DC motor constant speed controller capable of absorbing the influence of noise and the like.

[0006]

D according to the invention of claim 1
The C motor constant speed control device connects a switching means to a DC motor in series, detects an induced voltage of the DC motor, takes a difference from a target voltage, and controls a duty ratio of a drive signal according to the voltage of the difference. It was done like this.

According to a second aspect of the present invention, there is provided a DC motor constant speed control device in which switching means is connected in series to the DC motor,
The induced voltage of the DC motor is detected, the difference from the target voltage is calculated, and the duty ratio of the drive signal is controlled according to the voltage obtained by clipping the difference voltage at a predetermined level.

According to a third aspect of the present invention, there is provided a DC motor constant speed control device in which switching means is connected in series to a DC motor,
The induced voltage of the DC motor is detected, the difference from the target voltage is calculated, the difference voltage is compared with the reference signal, and the duty ratio of the drive signal is controlled according to the voltage that gives the hysteresis characteristic to the comparison output. It is the one.

[0009]

In the DC motor constant speed control device according to the present invention, the DC motor is chopper-driven by the switching means which is turned on / off by the drive signal, and the DC motor is induced during the period when the motor current does not flow when the drive signal is on or off. The motor speed is kept constant at the target speed by detecting the voltage and setting the duty ratio of the drive signal so that the induced voltage matches the target voltage.

According to another aspect of the present invention, in the DC motor constant speed control device, the DC motor is chopper-driven by the switching means that is turned on / off by the drive signal, and the DC current is induced during a period when the motor current does not flow when the drive signal is on or off. The motor speed is kept constant at the target speed by detecting the voltage and setting the duty ratio of the drive signal so that the induced voltage matches the target voltage. Further, since the voltage of the difference between the detected induced voltage and the target voltage is clipped at a constant level, the duty ratio of the drive signal does not become 100% even if the target speed or the motor speed changes abruptly and the control is performed. It can be prevented from becoming impossible.

In the DC motor constant speed control device according to the third aspect of the present invention, the DC motor is chopper-driven by the switching means which is turned on / off by the drive signal, and the DC current is induced during the period when the motor current does not flow when the drive signal is on or off. The motor speed is held constant at the target speed by detecting the voltage and setting the duty ratio of the drive signal by the drive signal control unit so that the induced voltage matches the target voltage.
In addition, by giving a hysteresis characteristic to the comparison output between the detected induced voltage and the target voltage and the reference signal,
The effect of noise is absorbed.

[0012]

EXAMPLES Example 1. An embodiment of the inventions of claims 1 and 2 will be described below with reference to the drawings. FIG. 1 is a block diagram conceptually showing a DC motor constant speed control device. In FIG.
1 is a DC motor, 8 is an input terminal for the target voltage E0, 2 is D
The switching means 3 which is connected in series to the C motor 1 and comprises a transistor for chopper-driving the DC motor 1 by means of a drive signal VD which is turned on and off at a set frequency, is induced from the motor terminal voltage V when the DC motor 1 is turned off. An induced voltage detector for detecting a voltage, 4 is an amplifier circuit for converting the motor terminal voltage V in level, 5 is a delay circuit for converting the drive signal VD into a trigger signal for detecting the induced voltage, and 6 is a trigger signal of the delay circuit 5. Is a sample hall circuit that is driven by and extracts and holds only the induced voltage from the output waveform of the amplifier circuit 4.

Reference numeral 7 indicates the duty ratio of the drive signal VD of the switching means 2 so that the induced voltage Vs fed back from the induced voltage detector 3 matches the target voltage E0 proportional to the target speed applied to the input terminal 8. A drive signal control unit for controlling, 9 is an oscillating circuit for generating a reference triangular wave for determining the drive frequency of the switching means 2, 10 is a proportional-integral circuit for proportional-integral control of the difference between the target voltage E0 and the induced voltage Vs, and 11 is an oscillation. Reference triangular wave of circuit 9 and proportional-integral circuit 1
It is a comparator that generates a drive signal VD by comparing the output voltage of 0.

FIG. 2 shows an embodiment of an actual circuit configuration embodying the conceptual configuration of FIG. 1, and the portions corresponding to those of FIG. 1 are designated by the same reference numerals. In FIG. 2, DC
A diode 12 for flowing a flywheel current when the switching means 2 is off is connected to both ends of the motor 1. The amplifier circuit 4 is composed of an operational amplifier 4c, resistors 4d and 4e for determining its amplification degree, and voltage dividing resistors 4a and 4b for obtaining a reference voltage, and the terminal voltage V of the DC motor 1 is connected via the resistor 4d. It is configured to be input to the operational amplifier 4c.

The delay circuit 5 is switched by the drive signal VD applied from the comparator 11 to the switching means 2, and the transistor 5 which inverts this drive signal VD.
a, a resistor 5b that determines the delay time, and a capacitor 5c.

The sample and hold circuit 6 is composed of an analog switch 6a made of a transistor, a holding capacitor 6b and an operational amplifier 6c. The analog switch 6a is turned on by a "H" trigger signal which is an output of the delay circuit 5. By being formed, the output of the amplifier circuit 4 is sampled and the capacitor 6b is charged.

The proportional-plus-integrator circuit 10 includes a buffer output operational amplifier 10d, capacitors 10a and 10b, and a resistor 10.
It is composed of c. A proportional circuit is configured by the operational amplifier 10d and the capacitors 10a and 10b. The operational amplifier 10d, the capacitors 10a and 10b, and the resistor 10c.
The integrator circuit is configured by. Also, operational amplifier 1
The target voltage E0 is applied from the input terminal 8 to the positive terminal of 0d.

A clip circuit 13 composed of a Zener diode 13a and a resistor 13b is provided between the proportional-plus-integrator circuit 10 and the comparator 11. The Zener diode 13a clips the maximum value of the output voltage of the proportional-plus-integrator circuit 10 with the Zener voltage, and the resistor 13b is provided to protect the Zener diode 13a.

FIG. 3 is a timing chart showing a signal waveform in each part of FIGS. 1 and 2 for explaining the operation of the induced voltage detector 3.

Next, the operation will be described. DC motor 1
When the drive signal VD shown in FIG. 3A is input to the switching means 2 connected in series to the DC motor 1 and the DC motor 1 is chopper-driven, the motor current I shown in FIG. The motor terminal voltage V shown in () is generated.
Here, the motor terminal voltage V will be described.
In the period in which D is off, the flywheel current flows to the diode 12 immediately after the drive signal VD is turned off, and thus the reverse bias is applied for t1 time.
When consumed in the series circuit of the C motor 1 and the diode 12, the motor current I also stops flowing, and only the induced voltage proportional to the motor speed is generated.

Therefore, first, in order to equalize the induced voltage and the voltage level with respect to the speed of the target voltage E0 applied to the input terminal 8, the motor terminal voltage V is amplified by the amplifier circuit 4 in FIG.
The level is converted into the output waveform of the amplifier circuit shown in (d). In order to detect the induced voltage during the period when the motor current I does not flow, the drive signal VD is set to the transistor 5a of the delay circuit 5.
And the time constant of t <t2 time is set by the resistor 5b and the capacitor 5c, the delay circuit output waveform shown in FIG. 3 (e) rises with a delay of t2 time with respect to the fall of the drive signal VD. Form the trigger signal. When the trigger signal is at the "H" level, the analog switch 6a of the sample hold circuit 6 is turned on to charge the capacitor 6b with the voltage V _S1 corresponding to the induced voltage of the amplifier circuit output waveform. Then, when the trigger signal is at the “L” level, the analog switch 6a is turned off to hold the charging voltage of the capacitor 6b, so that the sample-hold circuit output voltage shown in FIG. 3 (f), that is, the voltage corresponding to the induced voltage Vs. Only detect.

Next, the comparator 11 compares the output voltage that changes according to the difference between the target voltage E0 by the proportional-plus-integral control of the proportional-plus-integral circuit 10 and the induced voltage Vs that is the output voltage of the sample-hold circuit and the reference triangular wave of the oscillator circuit 9. And the duty ratio of the drive signal VD is set. According to this control method, the induced voltage V with respect to the target voltage E0
When s is low, that is, when the motor speed becomes slower than the target speed, the output voltage of the proportional-plus-integral circuit 10 is increased to lengthen the duty ratio ON time, thereby increasing the average voltage of the drive signal VD applied to the DC motor 1. To increase the motor speed. Conversely, if the motor speed becomes faster than the target speed,
Reverse the operation to slow down the motor speed. If the motor speed matches the target speed by both operations, the proportional-integral circuit 1
By stopping the change of the output voltage of 0 and fixing the duty ratio of the drive signal VD, the motor speed is kept constant at the target speed.

Further, when the DC motor 1 is started or when the target speed or the motor speed is drastically changed, when the duty ratio of the drive signal VD becomes 100% and the switching means 2 is constantly turned on, an induced voltage is generated. Control cannot be performed because it cannot be detected. Therefore, the output voltage of the proportional-plus-integral circuit 10 is set to a value such that the OFF time at the maximum duty ratio of the drive signal VD becomes (t2 time of the delay circuit 5) + (minimum time at which the induced voltage can be detected) by the clip circuit 13. Limit the maximum value and set the maximum duty ratio of the drive signal VD to 10
If it is less than 0%, it can be controlled at all times.

Example 2. FIG. 4 shows an embodiment of the invention of claim 3, and the portions corresponding to those of FIG. In this second embodiment, the comparator 11
By inserting the resistor 14 between the input terminal b and the proportional-plus-integrator circuit 10, the capacitor 15 between the output terminal a, and the ground 16 A hysteresis circuit 17 that operates temporarily is added.

In FIG. 4, assuming that the resistor 14 is R0, the capacitor 15 is C1, the capacitor 16 is C2, and the potential of the output terminal a is V0, a reference triangular wave (reference signal) as a comparator input waveform shown in FIG. At the intersection of A and the output voltage B of the proportional-plus-integral circuit 10, when the level of the comparator output waveform shown in FIG.
Change the potential of C1 / (C1 + C2) × V0,
It returns to the original level with the time constant of 1 + C2) × R0.

Therefore, the level of the input terminal b is temporarily changed like B of the comparator input waveform shown in FIG. 5A to widen the difference from the level of the reference triangular wave. That is, by obtaining a temporary hysteresis characteristic, it is possible to strengthen against noise and external noise due to the switching operation of the switching means 2 without changing the driving frequency.

Although the capacitor 16 is connected between the input terminal b and the ground c in the second embodiment, the same effect can be obtained by connecting the capacitor 16 in parallel with the resistor 14.

Example 3. In the first and second embodiments, the case where the switching means 2 is connected to the ground side of the DC motor 1 has been described. However, the switching means 2 may be connected to the power supply side of the DC motor 1 and the same effect as above can be obtained. .

[0029]

As described above, according to the invention of claim 1,
Since the DC motor is chopper-driven by the switching means, the induced voltage is detected and the duty ratio of the drive signal of the switching means is controlled according to the magnitude of the induced voltage, the induced voltage is generated during the period when no current flows in the DC motor. Can be detected, and the motor speed can be controlled to be constant at the target speed without being affected by the change in the armature resistance value. Further, when the DC motor is driven by the chopper, the power supplied from the power supply to the series circuit of the DC motor and the switching means is changed in accordance with the duty ratio of the drive signal, so that the circuit efficiency can be obtained in the entire control region. There is an effect that can be.

According to the invention of claim 2, the DC motor is chopper-driven by the switching means, and
The induced voltage is detected and the duty ratio of the drive signal of the switching means is controlled according to the magnitude of the induced voltage.At that time, the voltage that is the difference between the detected induced voltage and the target voltage is clipped at a predetermined level. Since the drive signal is configured to be obtained, the duty ratio can be suppressed to less than 100% even if the target voltage or the motor speed drastically changes in addition to the above-described effects obtained by the invention of claim 1. ,
This has the effect of preventing loss of control.

Further, according to the invention of claim 3, the DC motor is chopper-driven by the switching means, and the induced voltage is detected and the duty ratio of the drive signal of the switching means is controlled according to the magnitude thereof. Then
Further, the voltage difference between the detected induced voltage and the target voltage is compared with the reference signal, and the drive signal is obtained based on the voltage having the hysteresis characteristic in the comparison output. In addition to the effect, there is an effect that it becomes stronger against noise due to switching operation and external noise without changing the driving frequency.

[Brief description of drawings]

FIG. 1 is a block diagram conceptually showing a DC motor constant speed controller according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a specific circuit configuration of the device.

FIG. 3 is a timing chart showing the operation of the device.

FIG. 4 is a block diagram showing a DC motor constant speed controller according to an embodiment of the present invention.

FIG. 5 is a timing chart showing the operation of the device.

FIG. 6 is a circuit diagram showing a conventional DC motor constant speed control device.

[Explanation of symbols]

 1 DC motor 2 switching means 3 induced voltage detection unit 7 drive signal control unit VD drive signal E0 target voltage Vs induced voltage

Claims (3)

[Claims] 1. A switching means which is connected in series to a DC motor and drives the DC motor with a chopper by a drive signal, an induced voltage detecting section for detecting an induced voltage of the DC motor, and an induced voltage detecting section. A DC motor constant speed control device comprising: a drive signal control unit that controls a duty ratio of the drive signal according to a voltage of a difference between an induced voltage and a target voltage. 2. A switching means that is connected in series to a DC motor and drives the DC motor by a chopper by a drive signal, an induced voltage detection unit that detects an induced voltage of the DC motor, and an induced voltage detection unit that detects the induced voltage. A DC motor constant speed control device comprising: a drive signal control unit that controls a duty ratio of the drive signal according to a voltage obtained by clipping a voltage of a difference between an induced voltage and a target voltage at a predetermined level. 3. A switching means that is connected in series to a DC motor and drives the DC motor with a chopper by a drive signal, an induced voltage detection unit that detects an induced voltage of the DC motor, and an induced voltage detection unit that detects the induced voltage. And a drive signal control unit for controlling the duty ratio of the drive signal in accordance with the voltage having a difference characteristic between the induced voltage and the target voltage and the reference signal and having a hysteresis characteristic. DC motor constant speed controller.