JPS59106892A - Speed control system for dc motor - Google Patents

Abstract

PURPOSE:To enable to set a speed over a wide range by controlling a DC motor at a constant speed on the basis of an acceleration until rising to the prescribed speed from the energization of the motor and an acceleration until decreasing to the prescribed speed by stopping the energization of the motor. CONSTITUTION:A controller 11 measures and stores data representing the negative acceleration alphaOFF produced by the relationship between data representing acceleration alphaON produced when the constant current is flowed through the armature of a DC motor 2 in a short time at the drive starting time and a load when the current is interrupted, and stores a calculation equation for predicting the ON time TON of the motor so that the deviations DELTAV+ and DELTAV- of the speeds predetermined for the set speed V become ¦DELTAV+¦=¦DELTAV-¦. At the constant speed control, the alphaON, alphaOFF, Ti, the speed (v) of the motor and the energization time TONi from the set speed V to the motor are calculated whenever an encoder 3 applies a pulse to turn ON the switching unit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a control device for rotating a DC motor at a constant speed at an arbitrary set speed.

Conventional technology Conventionally, as a constant speed control method for a DC motor, 1) the back electromotive force of the windings is generated in proportion to the rotational speed of the motor;
A method of constructing a resistance bridge circuit and using equilibrium conditions regarding resistance.

2) Using a rotation speed detection means that generates a voltage or frequency signal proportional to the motor rotation speed, this signal is converted from frequency to voltage, and the amount of current is proportional to the difference between the voltage and the voltage corresponding to one set speed. How to add a motor.

3) Using the same rotational speed detection means as in 2), compare the phase of this signal with a reference frequency corresponding to the set speed, pass the phase difference signal through a loop filter, and use this signal to control the amount of current to the motor. how to.

etc.

However, in method (2), the temperature characteristics of the back electromotive force are poor, making temperature compensation difficult. Although the method 2) is not affected by the temperature of the detection signal, there is a delay in response depending on the time constant of the low-pass filter that constitutes the frequency/voltage converter. The method 3) is used for fine adjustment when the motor rotation speed is close to the set value, and is often used in combination with the control method 2). However, this method also has the same drawbacks as 2). In order to speed up the rise response, there is a method of forcibly switching the filter output to a fixed value, but in order to vary the set speed over a wide range, it is necessary to switch the timing or change the filter time constant. The configuration becomes complicated.

4? to eliminate the above problems. Gansho 56-21
4411 specification discloses a speed control method for a DC motor in which the DC motor is operated intermittently at a fast speed and the motor is operated at a constant speed determined by the pulses of the DC motor, but in this case, the acceleration data is fixed. Therefore, when the load fluctuates or there is a temperature change (low F
It was difficult to respond.

OBJECTS OF THE INVENTION It is an object of the present invention to solve the above-mentioned drawbacks and to provide a control 1III device with a simple configuration that allows speed settings over a wide range and has a short response time.

SUMMARY OF THE INVENTION In general, a DC motor exhibits a constant acceleration determined by the motor torque and load when approximately a constant current is applied over a narrow range of rotational speeds. Furthermore, when the power to the motor is turned off, it exhibits a constant negative acceleration determined by the friction t of the load. Letting this acceleration be αoN and αOFF, these values should be measured and stored in a microcomputer at the start of motor drive (see Figure 1).
Control as shown is possible. That is, at the speed ■, the motor is energized for a certain time ToN, and the motor is accelerated to a rotational speed higher than the set speed V by a certain speed ΔV+. After that, the power to the motor is cut off until the encoder pulse for motor speed detection is input, and the set speed V
The speed is reduced by ΔV−. And ΔV+ and Δ
The energization time ToN to the motor is set so that V- is equal to
is predicted and determined by a computer from the above acceleration ON/OFF. Such control @It allows the average speed of the motor to be set to the set speed V.

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 shows an example in which the present invention is used to drive an optical scanning system of a variable magnification copying machine having multiple stages of copying magnification. (1) is a scanning system including an illumination system, and (2) is a DC motor for driving the scanning system.

(3) is an encoder for detecting the rotational speed of the DC motor (2), which produces pulses with a frequency proportional to the rotational speed of the DC motor (2).

Fig. 3 shows the configuration of a 1tilJ control device for controlling the speed of the DC motor (2) by 7gl, and (10) is a switching unit for turning on and off the power supply to the DC motor (2). It is also possible to switch between forward and reverse rotation.

tll) The mv control section uses a microcomputer to control the fd switching section (10), and the control f41 section (11) has an 8-bit internal timer.

The control unit (1) includes a set speed of the motor (2) that is set in accordance with the copying magnification of the copying machine, a scan command S that causes the scanning system (1) to rotate forward or reverse, and a stop (brake). Directive B
etc.) When various control signals are applied, the actual speed of the motor (1) is transmitted from the encoder (3) for speed detection of the DC motor (2) via the waveform shaping section (12).
A pulse having a pulse interval corresponding to this is applied, and a reference pulse of a fixed frequency for measuring the pulse interval from the encoder (3) is further applied from the reference oscillation unit (13). Then, during the interval between two adjacent pulses generated from the encoder (3), the number of pulses generated from the reference oscillator (13) is counted by an internal timer, and the counted value is The rotational speed of the DC motor (2) is stopped. In this example, the encoder (3) has a rotation rate of 50% per revolution of the DC motor (2).
On the other hand, the starting frequency of the reference oscillator is
200 kl-1z. For example, when the DC motor (2) is rotating at a constant speed of 40 Orpm, ? I
Pulses ar of the reference oscillation counted at the tlJ cape (11)
/'1600. When the rotational speed of the DC motor (2) becomes fast (the encoder (
Since the pulse interval from 3) becomes shorter, the processing of the microcomputer becomes difficult to follow, and as a result, the sensitivity of the detected speed of the G DC motor (2) decreases. In order to prevent such malfunctions, for example, the programs shown in Figs. 4 to 7, which will be described later, for controlling the speed of an encoder are stored, as well as a program for executing the energization copying operation. ing. It should be noted that the details of the copying operation are not related to the present invention and will not be explained here.

In the control unit (11), at the start of 1 drive, the DC motor illusion 2)
Data representing the acceleration αON that occurs when a constant current is passed through the armature for a short time, and the negative acceleration t(f-01) that occurs in relation to the load when the current is cut off.
゛Measure the data representing F and write down this data, and find the predetermined speed deviations ΔV+ and ΔV- with respect to the set speed V, and 1Δ■4-1-1Δv-1. The calculation formula for predicting the ON time 'rON of the motor is stored.

Then, during constant speed control, according to the rotation of the motor,
When one pulse P1 is applied from the encoder (3) to the control unit (11) shown in FIG. 1, the control unit +I])
v: J:, αoN7αoFF, Ti, motor speed v
and the set speed~', calculate the energization time TONi to the motor, and use the time 'ONi to calculate the switching unit (1
0) is turned on, a predetermined electric power is supplied to the DC motor 12+1, and the DC motor (2) is accelerated. After TONi,
When the motor speed becomes V+ΔV, the switching part (1
0) is off. This (complicated, DC motor (2)
The current supply to the DC motor (2) is then cut off, and the DC motor (2) is decelerated.

When the next pulse P2 is applied from the encoder (3) to the control unit (11), the time TONi-1-1 for the motor speed to reach V-+匈■,-1 is operated in the same manner as described above. is measured, and during this TONi-1-1 time, the switching unit (10) is turned on again to supply power to the DC motor (2),
To accelerate.

Thereafter, by the same operation, the motor can be driven every time a pulse is received from the encoder (3), and the DC motor 12 can be maintained at a constant speed.

The operation of the control section (11) will be described below with reference to the flowchart in FIG.

In the control section (11), the DC motor is controlled by a microcomputer that controls other processes of the copying machine. From now on, this process Wtl
The microcomputer for LRA is called a mask.

When the control section is reset due to the start of the copying operation, the main routine is started, and after performing internal cutting in step M1, it waits for an instruction from the 7-star.
In a certain step of the process, when it is time to scan the document, a scan signal S indicating that it is time to start scanning and data representing the set scanning speed V are output to the control section.

In the control section, the scan signal S is input in step M2,
In step M3, when the data of the set scanning speed V is input, in step M4, the encoder pulse interval Ts corresponding to the set speed V is calculated, and then scanning is started.

At the start of scanning, acceleration is first measured.

Prior to measuring this acceleration, in step 5, a flag IM01)E indicating an interrupt processing mode, which will be described later, is set to "1". If the flag IMODE is not O'', the imprinting process is in a mode that measures the encoder pulse m] interval.Next, in step M6, the parameter TI used in the interrupt process is determined.

After setting the initial values for Tre, T, and T, the switching unit is set to normal rotation/on in step M7 in order to measure the acceleration αON when the motor is energized.

Then, in step M8, interrupt processing is permitted.

When the switching unit is turned on and rotates in the normal direction, the motor starts rotating and a pulse is generated from the heel-coupled encoder. In step M9, the control section measures the encoder pulse interval using an encoder pulse interval measurement routine SAMPLE, which will be described later.

In the subroutines SAMPI and E, the pulse interval when called is set in the temporary memory register (Rt), and the previous pulse interval is also recorded in the register (V') (Ro), so that continuous Stores the encoder pulse interval. In step X10, the pulse interval of the encoder is compared with the pulse interval Ts corresponding to the current set speed, and it is checked whether the motor has reached the set speed or not. If the motor has not reached the set speed, pulse interval measurements are repeated until the motor reaches the set speed.

When the motor reaches the set speed, S is set in step M11.
The continuous encoder pulse interval R□ and IR1 measured from AMPLEf are substituted into the function F21 for calculating acceleration, and the acceleration αON when the motor is turned on is determined and stored in the register AoN.

Find the missing number, the acceleration αOFF when the motor is off.

First, in order to prevent the influence of mechanical vibrations and the like when the motor is turned off, the motor is turned on for an extra 141 seconds and then turned off.

This is done by measuring the pulse interval N times using Sfutub M12 to fM1.5fS AMPLE.
.

cormorant. However, the data measured here is ignored. After that, the motor is turned off in step M16, and the motor is turned off in step M1.
7. At M18, measurement of the pulse interval for determining the acceleration σOF'F is started. 1 for measurement, and the process is repeated until the set speed F1 is reached, which is the opposite of when the acceleration αON was obtained. Then, the measurement ends, step M1
9, substitute the continuous encoder pulse interval R□, R1 to the function F2 to find the acceleration αOFF,
Set in register (Ao FF).

When the measurement of accelerations αoN and αOFF is completed, constant speed control is started based on this data. At the beginning of constant speed control, the current speed is close to the set speed, so step M2
0 sets the motor energization time TON to O. Then, in step M21, a flag IMODE indicating a mode of interrupt processing, which will be described later, is set to 0" to set the motor to constant speed control. Thereafter, the motor is controlled at a constant speed to the set speed V by interrupt processing. Here, in the main routine, in step M22, the scan signal S is turned off (it continues to wait until the scan path r timing is reached).

When scanning of the original is completed, the scan signal S from the mask is turned off. In the main routine, step.

When this is detected in step M22, the interrupt processing is terminated and the constant speed control is terminated in step M23. Next, step M2
At step 4, the switching unit is set to reverse rotation, and the scanning system is returned to the scanning start position. At this time, constant speed control is not performed. When the scanning system approaches the scanning start position, the master outputs a brake signal B in step M25. As a result, in step M26 of the main routine, the switching section is set to the regenerative braking mode (the motor is set to 1st speed).

Thereafter, when the scanning system returns to the scanning starting position, the brake signal B from the mask is turned off. In the main routine, this is detected in step M27 and the process returns to waiting for the scan signal.

Next, separate processing will be explained based on the flowcharts of FIGS. 5 and 6.

There are two types of interrupt processing: INT-1'' and INT-E. Of these interrupts, INT-T is a process in which the internal timer register (Treg) of the microcomputer is connected to the external clock terminal (ECK). reference oscillator (13
) and when it overflows (an interrupt occurs).

The timer register (Treg) continues counting from zero again even after the OUT (-) flow, and continues counting every time this pulse arrives from the external clock terminals (F, CK).The other interrupt INT-E is connected to the external interrupt terminal (TNT) (On the third mountain,
When a pulse is input from the encoder (3), an interrupt is generated. When an interrupt occurs, execution of the main routine for copying operation is temporarily interrupted, and control is then transferred to the corresponding interrupt handling routine. , After the processing path r, the control rrIll can be returned to the original main routine.Also, if an interrupt occurs during one interrupt processing (1 in the other),
The latter interrupt is suspended until the former interrupt processing is completed, and after the former interrupt processing path T, control is transferred to the latter interrupt processing routine without returning the interrupt IEj to the main routine. Also, if an interrupt occurs at the same time (Koke, external interrupt will be handled one time first).

When the section switch 7, 41 (1) is set to forward rotation, the DC motor (2) starts rotating in the forward direction, and the encoder (3) starts rotating at a frequency proportional to the rotation speed V+ of the DC motor (2). ) pulses begin to be output. However, when the DC motor 2) starts rotating, the rotation speed is still low, so the pulse interval from the encoder (3) is long, and the timer register (Treg) overflows first. This (this causes a timer interrupt to occur, and the interrupt handling routine INT-T is controlled from the main routine.
will move. In the INT-T shown in Fig. 5, first, Stella acupuncture point 1
Check the current cutting processing mode flag IMODE. If pulse interval measurement mode (IMOI:)E\
o), the interval timer (TI) is updated by adding the current set time T to the timer register (Treg) to the interval timer (TI) at 7 times T6. Then, in step 1-7, the time until the next timer register (Treg) overflow is 1. m
Set a to end the process. Also, if the speed Mi control mode (rMODE-o'') is in Stellanovo 1, it is checked in step T2 whether the motor (2) is in the on state, and if it is in the on state, the motor is turned on or off in step T3.
Timer (ToN), timer register (Treg)
Subtract the initial value (1) of . If ToN) becomes negative or zero in the Stellar pot 4, the motor (2) is turned off in step T5. In the next step T6, (T) is added to the interval timer (TI) to update (TI). Finally, in step T7, (T)(ko(Treg)
The maximum value (Ema) (in this case, 28) is set, the process is terminated, and control is returned to the main routine. Timer
Since the register (Treg) continues to count from zero even after overflow, the next timer interrupt will occur when the pulse of the external link terminal ECK is 2 times.
8-256 counts later. This is equivalent to setting the timer register (Treg) number maX (-28). In this embodiment, the external clock terminal ECK
The oscillation frequency of the reference oscillator connected to 2 Q Q
k) Iz, so this time is ], 28m5.

Another interrupt processing INT-E is encoder (3)
When a pulse from INT-J is input to the external interrupt terminal (TNT), an external interrupt is generated and control is transferred to INT-J.

In INT-E in FIG. 6, first, in step E1, the interval timer (TI) is set to the current timer register (
Treg) values to find the current encoder pulse interval. Next, step E (current interrupt processing mode flag IMOI in step 2) is checked. if,
If pulse interval measurement mode <IMODE\〃0″),
In step EIO, the current encoder pulse interval TI is saved in the temporary memory register (R2), and in order to notify the main routine that the measurement of the pulse interval has ended, in step EIO, a request is made to set the pulse interval. Clear flag REQ. Then, in step E9, the interval timer (TI) is activated for the next measurement, and the process is terminated. Also, in step E2, constant speed control mode (IM (
month) E= non ), then in step E3 function F
3, find the current speed V of the DC motor (2). Then, in step E4, the motor on timer (TON)
ζ Temporarily set zero. Next (in step E5, this speed V and the preset set speed (target speed)
Assign (2) to the optimal time function F4. Function F4 does not have a fixed value, but if speed ∆ exceeds a certain value, the average speed until the next encoder pulse arrives will exceed the set speed V, even if the motor is not turned on at all. (Step E6-NO). In this J case, d: the value of the function F4 (cannot be found. Therefore,
In such a case (in step E4, the motor is turned off until the next encoder pulse arrives).
Here, the value of the interval timer (ToN) may be set to zero. When the function F4 is determined, step E6 sets the value of F4 to the motor on timer (ON), and step E7 sets the switching unit (1a) to the motor ON timer. 7'/de, (ToN
), the real time register (T r e g )
The number of threads produced in the maximum time ('mad) is stored in the timer (T), and its complement is stored in the timer register (Tr).
eg) Set +C1 and FL. Therefore, the function F
The time determined by 4 is a value converted to a count value of the reference oscillation frequency. Next (step E9), as in the pulse interval measurement mode, the interval timer (TI) is cleared, the INT-E process is ended, and control is returned to the main routine.

As described above, there are two interrupt processes TNT-T.

In the pulse interval measurement mode, the INT-E measures the encoder pulse interval that corresponds to the motor rotation speed, and in the constant speed control mode, it simultaneously controls the motor power and calculates the average rotation speed of the motor. Keep at set value.

Next, the subroutine S A M P I-E shown in FIG. 7 will be explained. SAMPL and E are subroutines for reading pulse intervals in the same way as interrupt processing in pulse interval measurement. In SAMPLE, first, step S
1 sets the pulse interval measurement request flag kEQ to 1,
Continue waiting for flag REQ to be reset. In the interrupt processing INT-E, when the measurement of the pulse interval is finished,
Set the pulse interval in the temporary storage register (k2) and reset the flag REQ at the same time. In SAMPLE,
When this is detected in step S2, in step S3, the previous measured value stored in the temporary memory register (k□) is temporarily stored and transferred to the instantaneous register (ko), and the current measured value is transferred from the register (k2) to the register ( R1,) Ic is read and processing is terminated. In this way, SAM P L
At E, the measured values of two consecutive pulse intervals are stored in a temporary storage register.

As explained above, in the present invention, when the motor is energized and the motor starts rotating, the acceleration until the motor reaches a predetermined speed (up to -L), and the motor speed is set to a predetermined value (after the motor starts up, the motor starts rotating). By stopping the power supply to the motor and actually measuring the specified speed (acceleration until this decreases), constant speed control of the motor is performed based on the measured acceleration, so even if the load and motor change, the control device cannot be changed. There is no need to do this, and furthermore,
Since there is no change in control parameters, standardization becomes possible when the allocation is made into software. Additionally, it is not affected by temperature rises during long-term operation, and can be controlled in a stable manner.

[Brief explanation of the drawing]

FIG. 1 is a time chart showing the operation of the control system of the present invention, FIG. 2 is a perspective view showing a driving device for an optical scanning system of a copying machine to which the present invention is applied, and FIG. 3 is an embodiment of the present invention. The block diagrams shown in FIGS. 4 to 7 are flowcharts showing one embodiment of the tltlJ control program of the present invention. (2)...DC motor, +3+...encoder, f
IO)...switching section, till...control section. Patent Applicant: Minolta Camera Co., Ltd. Agent Masuji Aoyama, 2 Names, 4 Figures 5, 7, 6

Claims (1)

[Scope of Claims] 1. Pulse generating means for generating a pulse signal with a frequency proportional to the rotational speed of a DC motor, means for detecting the rotational speed of the motor from the pulse interval of the pulse generating means, and a motor when energized. means for measuring the acceleration of the motor and the acceleration of the motor when the power is cut off, and storing the measured acceleration, and the rotation speed of the motor when the motor is energized for a predetermined time (TON) when the motor is rotating. , V+ for the target value V
Δv1, and then the rotational speed when the current is cut off for a predetermined time (TOFF) is V-ΔV2 (Δv1.Δv2 is a positive number), then TON 4-TOFF-'ゝ pulse interval ΔV = Δ■2 ■ Then, ToN or TOFF is calculated using the detected rotational speed of the motor and the stored acceleration, and ToN or TOFF is calculated at the time of the pulse generation.
4. A speed control method for a DC motor, characterized in that a constant speed V is obtained on average by controlling the energization to the motor.