JPS60216779A - Control system for dc motor - Google Patents

Abstract

PURPOSE:To stably control a DC motor by starting the energization of the motor at every prescribed period, and stopping the energization by a pulse signal from an encoder. CONSTITUTION:A microcomputer 8 turns ON a transistor Q5 through an output circuit 10 simultaneously upon starting of the period of T=1/M.N (where M is the number of pulses of a rotation detection signal and N is a target rotating speed of a motor), turns On transistors Q1, Q4, and applies a positive going voltage to the DC motor 1. Then, when a rotation detection signal is input from a photointerrupter 7 of an encoder mounted in the motor 1 through an interrupt circuit 9, the drive of the transistor Q5 is eliminated by an output circuit 10 to eliminate the application of the voltage to the motor 1. When the rotation detection signal is obtained before the starting point of the period T, a reverse voltage is applied to the motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a DC motor control system using a microcomputer.

(Prior Art) Various methods have been proposed for controlling the rotational speed of a DC motor, but there is a tendency to use microcomputers to diversify control.

Conventionally used control methods include: ■ A method in which the induced voltage generated when the DC motor rotates is compared with a set voltage corresponding to the desired rotation speed, and the difference is fed back to the drive voltage applied to the DC motor. .

■Attach a tachometer that generates a voltage proportional to the rotational speed to the DC motor, compare the output voltage of the tachometer in Part B with the set voltage corresponding to the desired rotational speed, and calculate the difference between them to the DC motor. A method that provides feedback to the applied drive voltage.

■Phase Loop (PLL; Phase Lo
ckedLoop) to control the voltage applied to the DC motor so that the pulse train from the encoder attached to the DC motor and the pulse train of the frequency corresponding to the desired rotation speed are phase-synchronized.

etc.

However, in all conventional methods, the voltage applied to the DC motor is controlled in an analog manner.
When using a microcomputer for control, A/D,
It requires an interface circuit such as a D/A converter and an analog circuit for feedback, and also requires a tachometer such as a tachometer or a high-precision encoder, making the configuration complex and expensive. There was a drawback.

(Object of the Invention) The present invention has been proposed in view of the above points, and its purpose is to provide a DC motor control method that is suitable for control by a microcomputer, has a simple configuration, and can perform stable control. It's about doing.

(Structure of the invention) Hereinafter, the present invention will be described in detail with reference to the drawings showing examples.

FIG. 1 shows the mechanical configuration of an embodiment of the present invention. In the figure, 1 is a DC motor to be controlled, and a gear 3 is attached to its rotating shaft 2.
The gear 3 is meshed with another gear 4 to transmit power. Further, a slit plate 6 is attached to the rotating shaft 2, and a photo ink club tough is provided so as to sandwich the blade portion of the slit plate 6.

Incidentally, the slit plate 6 and the photointerrupter 7-, which constitute the encoder 1, are precise.

It is not necessary to use a highly accurate encoder such as that used for control, but a simple one that only has the function of generating a predetermined number of rotation detection signals (pulse signals) for each rotation of the DC motor 1 is sufficient. Furthermore, it goes without saying that the present invention is not limited to the illustrated configuration and can be used with other encoders.

Figure 2 shows an example of the circuit configuration related to control.
1 and 7 are a DC motor and a photointerrupter, respectively, in FIG. To explain the configuration in the figure, the photointerrupter 7 consists of a light emitting diode LED and a phototransistor PTr, and a signal generated at the emitter of the phototransistor PTr is sent to the interrupt circuit 9 of the microcomputer via a waveform shaping circuit formed by a transistor Q7. It is now entered. On the other hand, transistors Q,, Q2. Q, Q4 constitutes a drive circuit for the DC motor 1, and is designed to be capable of forward and reverse rotation. A series circuit of transistor Q2 of transistor Q2 and transistor Q4 of NPN type is connected between the positive power supply +V and the ground line, and transistors Q1. The collector of Q3 and the transistor Q2. A power terminal of the DC motor 1 is connected between the collector of Q4 and the collector of Q4. In addition, since the transistors Q, , Q2 perform complementary operations, their bases are connected to the collectors of each other by resistors R5゜R.
Connected via 4. Next, transistor Q3
The collector and base of are connected to the collector of transistor Q5 via diodes D1 and D2, and the collector and base of transistor Q
The collector and base of 4 are diode D3. These transistors Q are connected through D4 to the collector of transistor Q6.

Q is turned on from the output circuit 10 of the microcomputer 8,
Off is now controlled. Note that R1 is LE
D is the current setting resistor, R2 is the base resistor of the transistor Q7, and R3, R6, R are the respective transistors Q7. Q
,, is the collector resistance of Q6.

FIG. 3 shows the operating state of the present invention, where ■□ is the voltage applied to the DC motor 1 (the forward rotation direction is assumed to be positive);
■8 is the transistor Q detected by the photo-intertabber tough
7 is a rotation detection signal whose waveform has been shaped.

Therefore, the number of pulses of the rotation detection signal generated per one rotation of the DC motor 1 from the encoder l is calculated from the M1 DC motor 1.
When the target rotational speed of is N, the period is measured by the microcomputer, and at the same time as the start of the period Tl, the transistor Q5 is turned on via the output circuit 1o, the transistors Q and jQ4 are turned on, and the transistors Q2, . Q3 is turned off and a voltage in the forward rotation direction is applied to the DC motor 1. Next, when a rotation detection signal is obtained from the photointerrupter 7 of each encoder via the transistor Q7, this fact is input to the microcomputer via the interrupt circuit 9, and the output circuit 10 releases the drive of the transistor Q5. Then, the voltage application to the DC motor 1 is stopped. And the period T
Every l above <5. D□! , □, 3 degrees □□-2□.

Driving is performed.

That is, FIG. 3 shows the operation in a steady state, but if the rotational speed of the DC motor 1 were to slow down due to some influence from this state, the motor applied voltage vM
The phase difference between the rising edge of VS and the rising edge of the rotation detection signal VS becomes larger, the energization time T1 to the DC motor 1 becomes longer, the average voltage increases, and this works to correct the decrease in the rotational speed. This correction is possible until the energization time T1 reaches Tl, that is, until it reaches the DC level, and if the desired motor rotation speed cannot be obtained even at the DC level, it means that the DC motor 1 has exceeded its ability. Therefore, it can be seen that according to this method, the DC motor 1 can be controlled to the limit of its capacity.

On the other hand, if the rotational speed of the DC motor 1 increases due to some influence from the state shown in FIG. 3, then the motor applied voltage v1.
The phase difference between the rising edge of l and the rising edge of the rotation detection signal v8 becomes smaller, and the energization time T1 to the DC motor 1 is reduced, working to correct the increase in rotational speed. This correction is possible until the energization time TI becomes zero, that is, the drive voltage becomes zero. Zero drive voltage means that the DC motor l stops, so it is possible to make this correction in conjunction with the operation when the speed decreases as described above. It can be seen that the rotational speed can be controlled from zero to the maximum speed of the DC motor 1.

Next, FIG. 4 shows the operation when a sudden speed change (speed increase) occurs in the DC motor 1. That is, due to a rapid increase in the speed of the DC motor 1, the period T at point a
If the rotation detection signal is detected before the start point of l, the next period TJ5t starts from the rising edge of the rotation detection signal of B.
During the period T2 until this transition, the output circuit 10 turns on the transistor Q6, and the transistor Q2. Q is turned on, transistors Q, , Q4 are turned on, and voltage is applied to the DC motor 1 in the reverse direction. Then, in the next cycle Tl, no voltage is applied in the forward rotation direction, and then in the next cycle Tl
A similar operation is performed when a rotation detection signal is generated before the start point of . As a result of these operations, a sudden brake is applied to the DC motor 1, making it possible to quickly correct a sudden speed change of the DC motor 1.

By the way, when performing the operation shown in FIG. 3, the rotational speed of the DC motor 1 may vibrate at a low frequency.

This is because the mechanical response of the DC motor 1 and the response of the electrically applied control do not match, and correction for changes in the rotational speed of the DC motor 1 can be made immediately by changes in the energization time T1. Correction is added, but since the response of the mechanical system involves a certain amount of delay time, the correction ends up in an overcompensated state.

However, in order to prevent these vibrations, the DC motor 1
If the control is in a transient state due to a change in the rotation speed,
Correct the energization stop time T3 by taking into consideration the previous state,
It is effective to gradually shift to the steady state period Tl. Specifically, the energization time in the nth period is TI
, , the energization stop time in the n-1th cycle is T3. , then the energization stop time T3o in the nth cycle is...
・・・・・・・・・(2) This can be achieved by controlling the value to be . Note that A is 1
By selecting the constant A to an appropriate value, it is possible to match the response of the electrical system and the response of the mechanical system, thereby preventing unnecessary vibrations from occurring. Also, in steady state T
3=T3n-1, so from the above equation (2), T3. = Tjl −Tl.

That is, TI, +T3. = Tl, and is controlled to the period Tl at the target rotation speed.

(Effects of the invention) As described above, in the DC motor control method of the present invention,
An encoder that sends M rotation detection signals per rotation is attached to the DC motor, and energization to the DC motor is started at intervals of T#=-1211-N for the target rotation speed N, and Since the operation of stopping the energization when a rotation detection signal is obtained from the encoder is repeated, the control is pulse-like, so it is suitable for control by a microcomputer, and the effect is that stable control can be performed with a simple configuration. be.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the mechanical configuration of an embodiment of the present invention, FIG. 2 is a diagram showing the same circuit configuration, and FIGS. 3 and 4 are operational waveform diagrams. 1...DC motor, 2...Rotating shaft, 3
, 4...Gear,)...Encoder, 6
...Slit plate, 7...Photo interrupter, 8-...Microcomputer, 9...
...Interrupt circuit, 10...Output circuit, Q, j~
j Q,...transistor, Dl, ~, D4・
...Diode, LED...Light-emitting diode, PT"...Phototransistor, R1,
～, R7・・・Resistance, +■・・・Positive power supply

Claims (3)

[Claims] (1) An encoder that sends M rotation detection signals per rotation is attached to the DC motor, and energization to the DC motor is started every cycle of Tl = - -N for the target rotation speed N, and the encoder A DC motor side system characterized by repeating the operation of stopping energization when a rotation detection signal is obtained from the motor. (2) When a rotation detection signal is given from the encoder before the start of cycle TJII, a reverse voltage is applied to the DC motor during the period from when this rotation detection signal is generated to the next cycle, and 2. The DC motor control system according to claim 1, wherein positive direction current is not applied during the period of . (3) Current application time in the nth cycle Tln, n-1th
The energization stop time in the cycle is T3. , , If A is a constant, the energization stop time T3 . A direct current motor control method according to claim 1, wherein the DC motor control method is controlled to a value such that: