JPS60197177A - Servo controller of motor - Google Patents

Abstract

PURPOSE:To set a drive system to a stable state in the shortest distance from the drive starting position by altering the switching position to phase comparing means from speed comparing means in response to a target speed. CONSTITUTION:When a scan start command is applied from a main controller through a serial signal line TXD, with the magnification at that time as a parameter a drive mode altering position data DP, a target speed data and scanning distance data are read out from a memory table. Then, an analog controller CU is set to a speed comparison control mode, and the target speed data is applied. When the counted value of an encoder pulse FB3 arrives at the mode altering position data DP, the controller CU is set to a phase comparison control mode. When the counted value arrives at the scanning distance data, a motor SVM is decelerated, stopped and then inverted.

Description

[Detailed description of the invention] ■Technical field The present invention relates to servo control of a motor, and in particular, when the motor starts up, control is performed only by a speed comparison control system.
The present invention relates to a servo control system for an electric motor that performs selective control to start phase comparison control when a predetermined condition is met.

■Prior Art For example, many copying machines are equipped with a variable magnification function to adjust the magnification of the original image and the copy image. This type of device is equipped with an optical scanning system to read the original image, but since the speed of the photoreceptor side that reproduces the copy image cannot be changed, this optical scanning system is required to change the magnification. It is common to change the scanning speed of

By the way, when driving the optical scanning system of a copying machine, for example, in relation to the size and operating speed of the device, the distance the scanning system moves from the start of scanning until the control system stabilizes at a predetermined speed, and It is necessary to shorten the time required in between.

Furthermore, after the scanning speed reaches the target speed, the system must be controlled to accurately maintain that speed in order to prevent image jitter and the like. Therefore, when performing this type of control, a control system that selectively uses a speed comparison control system and a phase comparison control system is generally adopted.

Whether the scanning speed has reached the target speed can be determined by checking whether the distance traveled by the movable object from the scanning drive starting position is equal to or greater than a predetermined value. Therefore, in general, a rotary encoder is connected to the drive shaft number of the motor, and the number of pulse signals output by the rotary encoder is counted from the start, and when the number reaches a predetermined value, the control mode of the drive system is updated.

However, for example, the scanner (optical scanning system) of a variable magnification copying machine
In this case, the target scanning speed changes depending on the magnification ratio. If the target scanning speed differs, the moving distance required from the start of driving until it reaches the target scanning speed will differ. Specifically, as shown in FIGS. 1a and 1b, when the target scanning speed is high (the variable magnification is small), a larger moving distance is required for the speed to reach the target speed than when the target scanning speed is low. Therefore, conventionally, the control mode update distance P has been set in accordance with the target scanning speed (maximum target speed) when the variable magnification is the smallest. However, with this, if the target speed is small, even if the speed reaches the target speed, the control mode will not change to phase control until the vehicle has traveled a predetermined distance further. In the speed comparison control mode, small speed fluctuations are likely to occur due to the influence of disturbances, so it is not preferable to perform image reading in this state, and as a result, the distance required for the scanner to start up becomes longer than necessary.

(1) Purpose The present invention aims to bring the drive system into a stable state in the shortest distance from the drive start position.

(2) Structure In this type of control system, as shown in FIG. 2b, the distance from when the drive system is started until it reaches the target speed is determined depending on the target speed. Therefore, for example, in a scanner whose target speed is determined according to the variable magnification, the mode change position M (Pl, P2, P3, etc.) is stored in advance for each variable magnification, and when the variable magnification is determined, the mode change position M (Pl, P2, P3, etc.) is If the mode change position is selected based on the magnification ratio, the phase comparison control mode can be immediately entered when the speed reaches the vicinity of the target speed at each magnification ratio, eliminating the need for unnecessary scanning.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 3 shows one type of motor control device embodying the present invention. Specifically, this is a scanner drive device for a copying machine. Referring to FIG. 3, digital control circuit D
CU, clock pulse generator OSC, analog control circuit ACU, motor driver DRV, waveform shaping circuit ST
Equipped with T etc.

The SVM is a DC servo motor that drives the scanner carriage.

A rotary encoder consisting of a rotating disk OK with slits and a transmission type photosensor PH3 is coupled to the drive wheel of this motor SVM.

When the motor SVM rotates, a pulse signal (encoder pulse) having a period corresponding to the motor rotation speed is obtained at the output terminal of the photosensor PH8. Photo sensor PH2 is
This is a sensor that detects the reference position (home position) of the carriage.

When PH2 detects the home position, it outputs the signal SHP.
occurs. The clock pulse generator O8C is a circuit that generates a pulse serving as a phase reference in the 1-phase comparison control mode, and the period of the pulse it outputs is set by the digital control circuit DCU.

Although not shown, the digital control circuit DC1J is internally equipped with a microprocessor, a counter, and the like.

Further, a serial transmission line TXD and a serial reception line RXD of a main control circuit of a copying machine (not shown) are connected to the serial data transmission line of the digital control circuit DCU. Signals such as a scan start instruction and variable magnification are transmitted through these signal lines.

Description will be made with reference to FIG. 4, which shows a specific circuit configuration of the analog control circuit ACU shown in FIG. 3. This circuit includes a 1-phase comparison circuit pcc, a digital/analog conversion unit DAU, a frequency/voltage conversion unit FVU, and a signal addition circuit SUM.

Friction compensation circuit 50. Amplifier AMP, current feedback circuit CFC
, a pulse width modulation circuit PWC, etc.

swt, SW2. SW3. SW4.
SW5. SW6. SW7. sws, SW9 and swi
o are analog switches, each with a signal line C
Digital control circuit DCU via SW (see Figure 3)
controlled by

The phase comparator circuit PCC compares the phase of the reference signal applied from the clock pulse generator OSC to the reference phase signal input terminal +Ref or -Ref with the phase of the feedback pulse signal FBI obtained from the rotary encoder. Output the level according to the result.

The digital/analog conversion unit DAU receives digital speed data DTV applied from the digital control circuit DCU.
Outputs an analog signal level according to the The frequency/voltage conversion unit FVU outputs a voltage level according to the frequency of the feedback pulse output by the rotary encoder, that is, the motor speed.

The pulse width modulation circuit PWC generates a pulse signal SdI+1 whose pulse width is modulated according to the level of the signal (error signal) output by the amplifier AMP, and transmits the pulse signal SdI+1 to the motor driver D.
Apply to RV.

The motor drive operation of the analog control circuit ACU will be briefly explained. When starting the drive of the motor SVM, the mode is the speed comparison control mode. In this operation mode, the cycle of pulses output by the rotary encoder is controlled so as to match the target speed. When the motor SVM is stopped, the rotary encoder outputs the pulse signal FB2.
does not occur.

Therefore, the output voltage (feedback voltage) of the frequency/voltage conversion unit FVU is zero. When predetermined digital speed data DTV is applied to the digital/analog conversion unit DAU in this state, a corresponding analog level (target speed voltage) appears at the output terminal of this unit DAU, and if the feedback voltage is zero, The level corresponding to this target speed voltage remains unchanged in the pulse width modulation circuit P.
WC number: is applied, and the motor SVM is energized according to its level.

When the motor 8VM is energized and starts rotating, the rotary encoder generates a pulse signal according to its rotation speed, which is applied to the frequency/voltage conversion unit FVU. A feedback voltage therefore appears at the output terminal of the unit FVU, which is dependent on the actual rotational speed of the motor. In this operating mode, a level corresponding to the difference between the target speed voltage and the feedback voltage appears at the output terminal of the amplifier AMP, so an error signal level is generated so that the rotational speed of the motor SVM always matches the target speed. Motor SVM is energized accordingly.

However, in this speed comparison control mode, there is a delay in the response of the control system, and furthermore, as the motor speed approaches the target speed, the control amount becomes smaller, so when a disturbance or the like occurs, relatively small speed fluctuations occur. Therefore, when the motor speed becomes close to the target speed, the mode shifts to the phase comparison control mode.

In the phase comparison control (PLL) mode, the phase comparison circuit FCC detects and outputs the phase difference between the feedback pulse FB1 obtained from the rotary encoder and the reference phase pulse output from the clock pulse generator O8C. , an error signal level corresponding to this phase difference is output from the amplifier AMP, and the motor SVM is thereby energized. The pulse signal output by the clock pulse generator O8C is very stable, so if even the slightest disturbance is applied to the motor SVM and the speed attempts to fluctuate, a large error signal is immediately generated to restore it to its original state. Control.

FIG. 5 shows a schematic operation of the digital control circuit DCU.

This will be explained with reference to FIG. When the power is turned on, each output port of the microcomputer is first set to the initial level (non-energized level), the memory is cleared, and each parameter number and initial value are set. Also, move the carriage to a predetermined position i.
! (a position slightly retreated from the home position).

The serial signal line TXD is monitored and waits until a scan start instruction is received from the main controller. When a start instruction is given, the current variable magnification ratio is read from the main controller via the serial signal line TXD. Next, the memory table is referred to using the read magnification ratio as a parameter. The contents of the memory table are shown in Table 1 below.

Table 1 First, drive mode change position data D corresponding to variable magnification ratio
P (any of PI-P5), and read target speed data and scanning distance data intermittently.

The analog control circuit ACU is set to the speed comparison control mode, and the target speed data DTV read from the table is applied to the digital/analog conversion unit DAU. Now, the analog control circuit ACU starts driving the motor SVM.

Wait until the photosensor PH2 detects the home position, and when the detection signal SHP is cursed, start counting the encoder pulses F and B3. The count of this pulse is
This is done using a hardware counter. Thereafter, the output of this counter, ie, the number of pulses, is monitored. When the number of pulses reaches the previously selected mode change position data DP↓;, the analog control circuit 118ACU is set to the phase comparison control mode.

When the number of pulses reaches the scanning distance data, the motor SVM is decelerated and stopped, and the motor drive direction is immediately reversed to return the carriage to the Baum position. When the home position is detected, the motor SvM is controlled to decelerate and stop, and the carriage is positioned at a predetermined position. Furthermore, the analog control circuit ACU is set to a non-energized state and the next scan start instruction is awaited.

In the above embodiment, the control mode switching timing is set based on the motor drive distance from the home position, but for example, a sensor may be placed at each control mode switching position for each variable magnification, and the timing may be changed according to the variable magnification. The control mode may be updated when the selected sensor detects the carriage. In the embodiment, the scanner of a variable magnification copying machine has been described, but the present invention can be practiced not only in a scanner of a device that similarly performs variable magnification, but also in any motor drive device in which a plurality of target speeds can be set.

(2) Effects As described above, according to the present invention, no matter which target speed is set, the control system can be set to the most stable state over the shortest distance.

[Brief explanation of drawings]

FIGS. 1a and 1b are graphs showing control mode change timing in conventional motor control. FIGS. 2a and 2b are graphs showing examples of control mode change timing in motor control of the present invention. FIG. 3 is a block diagram showing a scanner control device for a copying machine embodying the present invention. FIG. 4 is an electric circuit diagram showing a specific configuration of the analog control circuit ACU shown in FIG. 3. FIG. 5 is a flowchart showing the general operation of the digital control circuit DCU shown in FIG. DRVs motor driver (driving means) PH8: Photo sensor (detection means) DK: Disk FVU: Frequency/voltage conversion unit (speed comparison control means) OSC: Clock pulse generator (reference signal generation means) p
cc: Phase comparison circuit (phase comparison control means) ACU: Analog control circuit DCU: Digital control circuit (fli child control means) SVM
:DC servo motor SUM:Signal addition circuit 1a■ 2nd aa r1 full 1b■ 〒2b■ Tori 5■

Claims (4)

[Claims] (1) Drive means for driving the electric motor; detection means for outputting a signal according to the rotating speed of the electric motor; speed comparison control for applying a signal corresponding to the target drive speed and the output of the detection means to the drive means means; reference signal generating means for generating a pulse signal of a predetermined period; phase for comparing the phase of the signal from the reference signal generating means and the signal from the detecting means, and applying a signal according to the comparison result to the driving means; comparative control means;
and electronic control means for selectively using the speed comparison control means and the phase comparison control means and energizing the motor according to a predetermined instruction; The present invention is characterized in that conditions for switching between the speed comparison control means and the phase comparison control means are updated in accordance with the target drive speed. Servo control device for electric motor. (2) The electronic control means updates the position at which the speed comparison control means and the phase comparison control means are switched in accordance with the target drive speed of the electric motor, and the servo control of the electric motor according to claim (1) above is performed. Device. (3) The electronic control means determines the position based on the number of pulses of the signal output by the detection means. Said claim No. 2
) A servo control device for an electric motor as described in item 2. (4) The electronic control means is provided with a memory in which information on conditions for switching between the speed comparison control means and the phase comparison control means is stored in advance at a predetermined address associated with the variable magnification ratio. 2. A servo control device for an electric motor according to item (2) or item (3).