JPH066996A - Motor controller - Google Patents

Abstract

PURPOSE:To enhance safety and to detect reversal time of motor highly accurately at low cost by making a decision that the motor has actually inverted when the rotational speed of motor drops below a reference speed and performing abnormality processing if reversal point of motor is not detected within a predetermined time after provision of reversal instruction. CONSTITUTION:Upon receiving a reversal command from a body control section, a motor control section 6 delivers a reversal instruction to a driver 7. The motor control section 6 then counts pulses delivered from a photointerrupter 5 and cauclates rotational speed of a motor 1 during a unit minute time. The motor control section makes a decision whether the calculated rotational speed is lower than a reference speed or not and assumes that the motor 1 has reversed if the calculated speed is lower than the reference speed. If the speed of the motor 1 does not drop below the reference speed even upon elapse of sufficient time for detecting reversal of the motor 1, a decision is made that the motor 1 is abnormal and the motor 1 is stopped. This constitution enhances safety in the motor control employing a single phase encoder.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device, and more particularly to a motor control device capable of accurately detecting a reverse position of a motor when reversing the motor.

[0002]

2. Description of the Related Art For example, a motor for driving an optical system for illuminating and scanning a document in a copying machine or a facsimile machine, or a motor for driving an automatic document feeder mounted in a copying machine rotates in a first direction. And drives the optical system and the document conveying belt in the first direction, reverses them in the second direction at a predetermined timing, and drives the optical system and the document conveying belt in the second direction opposite to the first direction.

In such optical system driving and driving of the original conveying belt, it is necessary to accurately control the driving reversal position. For that purpose, it is necessary to detect when the motor, which is the drive source, actually switches from normal rotation to reverse rotation. By the way, the rotating motor has inertia, and even if a reverse command signal is given, it does not immediately switch from normal rotation to reverse rotation, and it does not depend on the reverse command signal and when the motor actually reverses from normal rotation to reverse rotation. , There is a time lag. Therefore, in the above-described optical system driving motor and the conveying belt driving motor of the automatic document feeder, the time between the reversal command signal given to the motor and the time when the motor actually reverses from normal rotation to reverse rotation is set. Accurate control cannot be performed unless the deviation is accurately detected and reflected in the control.

In the conventional reverse rotation control of a drive motor of an automatic document feeder, for example, there is a detection control at the time of motor reversal disclosed in Japanese Patent Laid-Open No. 61-174538. In the control described in this publication, the output pulse of the encoder connected to the motor is detected, and the difference between the time t1 when the inversion command signal is given to the motor and the time t2 when the encoder output stops changing is obtained. The time T between the time t1 when the inversion command signal is applied to the motor and the time t2 when the motor actually starts inversion is detected.

Further, in place of the control described in the above-mentioned publication, for example, a two-phase encoder that is interlocked with the motor shaft and has a phase difference of 90 degrees can be used to accurately detect the reverse position of the motor. it can. In a two-phase encoder having a phase difference of 90 degrees, generally, as the encoder rotates, pulses of A phase and B phase are output as shown in FIG. 7A. The A-phase pulse and the B-phase pulse have a phase difference of 90 degrees with each other. Therefore, when the motor rotates in the normal direction, as shown in FIG. 7B, when the B-phase signal level at the time when the A-phase pulse rises is detected, the B-phase level is, for example, high.

On the contrary, when the motor is rotating in the reverse direction, as shown in FIG.
As shown in C, when the phase A pulse rises, B
When the phase signal level is detected, the B phase signal level is low, for example. Therefore, by detecting the B-phase signal level at the time when the A-phase pulse rises, it is possible to accurately detect whether the motor is rotating in the normal direction or in the reverse direction.

[0007]

Among the above-mentioned conventional techniques, in the control described in Japanese Patent Laid-Open No. 61-174538, there is a deviation from when the inversion command signal is output to when the actual inversion is detected. Since the time T is relatively long and the time when the output of the encoder does not change cannot be accurately detected, the control method for detecting the time when the motor actually reverses has a drawback that the accuracy is not good. It was

On the other hand, in the method using the two-phase encoder having the 90-degree phase difference, the time when the motor actually reverses can be detected accurately, but the two-phase encoder is expensive and However, since the signal line from the encoder is of a two-phase type, there is one more line, which is not suitable for constructing an inexpensive device. Therefore, a motor control device having a simple structure and capable of accurately detecting the actual reversal time of the motor is desired. In inventing such a motor control device, since the two-phase encoder cannot be used as described above, it is necessary to detect the rotation speed of the motor based on the single-phase encoder. By the way, when the rotation speed of the motor is detected based on the single-phase encoder and the reversal time is detected, if the reversal of the motor is not detected, the reverse voltage is continuously applied to the motor. There is a defect.

Therefore, an object of the present invention is to provide a motor control device which does not have such a problem, has a simple structure, and is capable of accurately detecting the actual reversal point of the motor.

[0010]

The invention according to claim 1 is
Rotation signal output means connected to the rotation shaft of the motor and outputting a rotation signal in conjunction with the rotation of the motor; and speed calculation means for calculating the rotation speed of the motor based on the rotation signal output from the rotation signal output means. A means for outputting a reversal command to the motor, a discrimination means for discriminating whether or not the rotation speed of the motor calculated by the speed calculation means after the reversal instruction is output is equal to or lower than a predetermined reference speed, and the discrimination means is a rotation speed. In response to determining that the motor speed has become equal to or lower than the reference speed, the reverse detection means for determining the reverse time of the motor, and the output of the reverse command,
The motor control device includes an abnormality processing unit that performs abnormality processing when a motor reversal time is not detected within a predetermined time.

[0011]

According to the present invention, when the reversal of the motor is not detected within a predetermined time after the reversal command is output, it is determined that an abnormal situation has occurred and a predetermined protection operation is performed, so that the reversal of the motor is detected. It is possible to provide a safe motor control device that does not cause a dangerous state even when there is no such situation.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a motor drive control device according to an embodiment of the present invention. Referring to FIG. 1, the motor 1 is, for example, a DC servo motor and is for driving the load 2. As the load 2, for example, a transport belt of an automatic document feeder mounted on a copying machine can be considered.
Further, as the load 2, an optical system for original document illumination scanning of a copying machine can be considered. In addition, as the load 2, any driving member can be considered.

A detector 3 for detecting the rotating state of the motor 1 is connected to the rotary shaft of the motor 1. Detector 3
Is a single-phase encoder composed of, for example, a rotary disk 4 having a large number of radial slits and a photointerrupter 5 optically coupled to the rotary disk 4. With such a configuration, the detector 3 can be configured simply and inexpensively. In this embodiment, for example, a total of 70 to 80 slits are radially formed on the rotary disc 4. Therefore, when the motor 1 makes one rotation, 70 to 80 pulses are output from the photo interrupter 5.

The detector 3 is replaced with the above-mentioned structure,
Other devices, such as a frequency generator, that outputs a pulse that is cyclically linked to the rotation of the servo motor 1 may be used.
The output pulse of the photo interrupter 5 is given to the motor controller 6. The motor control unit 6 is provided with a microcomputer and a memory, and the motor control unit 6 controls the motor 1 to reverse and at the same time detects when the motor 1 is actually reversed.

The control signal of the motor control unit 6 is given to the driver 7, and the driver 1 rotates the motor 1.
FIG. 2 shows an inversion command signal output from the motor control unit 6, the actual rotation speed of the motor 1, and speed data and acceleration data detected by the motor control unit 6 based on the pulse output from the photo interrupter 5. FIG. 6 is a waveform chart showing the relationship of As shown in FIG. 2, when the reversal instruction is turned on, the actual speed of the motor 1 gradually decreases from the constant speed rotation on the forward rotation side at that timing, and the rotation of the motor 1 becomes 0 at time t2.
And then reverses from time t2.

The actual speed of the motor 1 is grasped in the motor control section 6 as stepwise speed data as shown in FIG. 2C based on the detection pulse of the photo interrupter 5. Further, the acceleration of the motor 1 is grasped in the motor control section 6 as shown in FIG. 2D based on the detection pulse of the photo interrupter 5. In the motor control unit 6, FIG.
C and pulse width data CW of the photo interrupter 5 as shown in FIG. 3 in order to calculate the data shown in FIG. 2D.
A circuit is provided for calculating DT.

Referring to FIG. 3, the pulse output from the photo interrupter 5 is given to the edge detection circuit 61. The edge detection circuit 61 detects, for example, the rising edge of the applied pulse and derives the detection output. The detected output is the up counter 6
It is given to 2 and counted. Further, the pulse width data CWDT calculation circuit is provided with a free running counter 63 of, for example, a 16-bit configuration that counts up the reference clock. The free running counter 63 uses, for example, a frequency f = 1.
The machine clock of the microcomputer of about 5 MHz is counted.

On the other hand, the output of the edge detection circuit 61 is given to the capture register 64 as a capture signal. The capture register 64 reads and holds the count number of the free-running counter 63 by using the capture signal given from the edge detection circuit 61 as a trigger. Therefore, the content of the capture register 64 is updated by the output of the edge detection circuit 61, that is, the rising edge of the pulse output from the photo interrupter 5.

Therefore, as shown in FIG.
At t1, the count number of the up counter 62 is UD
Cm and the count number of the capture register 64 at that time is CPTm. For example, the pulse width data CWDT given from the photo interrupter 5 is

[0020]

[Equation 1]

In FIG. 3, the up counter 6
Although it has been described that 2 is used, the up counter 62 may be replaced with an up / down counter that switches to down counting when it is detected that the motor 1 is reversed. In the above formula (1), considering the case of using the up-down counter,
The denominator on the right side is the absolute value.

The average acceleration during the unit minute time Δt is

[0023]

[Equation 2]

It can be obtained by By the way, when the motor 1 reverses, the actual speed of the motor 1 gradually decelerates from the forward rotation side, eventually becomes 0, and gradually increases to the reverse rotation side. However, in the speed data calculated in the motor control unit 6, even if the actual speed of the motor 1 becomes 0, the speed data does not become 0 as shown in FIG. is there.

Therefore, in one embodiment, when the speed data shown in FIG. 2C becomes equal to or less than a predetermined reference speed, it is considered that the motor 1 is reversed, or a more accurate reversal time of the motor 1 is determined. In addition, when the predetermined minute time Δt0 has passed since the speed data became lower than the reference speed, it is determined that the motor 1 has reversed. Also,
In another embodiment, the speed data shown in FIG. 2C is equal to or lower than a predetermined reference speed Nth, and in that case, the speed data shown in FIG.
The time when the acceleration data shown in D is reversed from negative to positive is regarded as the time when the motor 1 is reversed.

Further, in each of these embodiments, when the reversal of the motor 1 is not judged within a predetermined time after the reversal command is output, the protection processing is performed as an abnormal situation, The safety of motor control using a single-phase encoder has been improved. Next, an example of the control operation of the motor control unit 6 will be described with reference to the flowchart of FIG.

It is assumed that the motor 1 is a motor for driving a conveyor belt of an automatic document feeder installed in a copying machine, and the motor controller 6 is a controller for the motor. Then, the motor control unit 6 is given a reversal instruction from the main body control unit that controls the entire automatic document feeder.
In response, the motor control unit 6 outputs an inversion instruction to the driver 7. Further, the abnormality detection timer 3 is started (step S1).

Next, the timer 1 is started (step S2). The timer 1 is for measuring a unit micro time Δt. Next, the pulses input from the photo interrupter 5 are counted (step S3).
Then, pulse counting is continued until the unit minute time Δt elapses (steps S4, S3, S).
4).

As for the counting of this pulse, as described with reference to FIG. 3, the number of pulses is counted by the up counter 62, and the number of reference clocks during that time is counted by the capture register 64. When the unit minute time Δt elapses, the number of pulses (UDC) of the up counter 62 counted during the unit minute time Δt.
n-UDCm) and the change in the count number of the capture register 64 during the unit minute time Δt (CPTn-C
The pulse width data CWDT is obtained based on PTm), and the rotation speed N of the motor 1 is obtained based on equation (2) (step S5).

Then, it is judged whether or not the calculated speed N is less than or equal to the reference speed Nth (step S6). As a result of the determination, if the calculated N is not equal to or less than the reference speed Nth, then it is determined whether or not the timer 3 has timed up (step S7). The timer 3 is an abnormality detection timer as described above, and the time measured by the timer 3 is preset to a time sufficient for reversal detection. Therefore, as long as it is operating normally, the timer 3 does not time up at this point. Therefore, the control from step S2 is repeated, and the speed N during the next unit micro time Δt is calculated (steps S2 to S5).

On the other hand, if it is determined in step S7 that the timer 3 has timed out, that is, even if the time required for the reverse rotation detection of the motor 1 set by the timer 3 has elapsed, the motor 1 is still running. If the speed N is not equal to or lower than the predetermined reference speed Nth, it is determined to be in an abnormal state, the motor 1 is stopped (step S8), and this control ends.

Instead of immediately stopping the motor 1, for example, the driving may be stopped after the motor 1 is continuously rotated at a predetermined speed for a predetermined time. As described above, the characteristic feature of this embodiment is that the protection process is performed on the motor 1 based on the time-up of the timer 3. When the control of the motor 1 is normally performed, it is determined in step S6 that the calculated rotation speed N is equal to or lower than the reference speed Nth before the timer 3 times out. Then timer 2
Is started (step S9). The timer 2 is a timer for measuring a predetermined minute time Δt0.

After the timer 2 is started, when it is determined that the timer 2 has timed up by measuring a predetermined minute time Δt0 (step S10), it is determined that the motor 1 is reversed at that time (step S10). S11). When such control is performed, the time measured by the timer 2 is a minute time Δt0, so that the above-mentioned Japanese Patent Laid-Open No. 61-1
As in Japanese Patent No. 74538, since the reversal timing of the motor 1 is not detected by time observation based on the relatively long time T, there is an advantage that the reversal time of the motor 1 can be accurately determined.

Further, in this embodiment, the timer 2 is started after the rotational speed N of the motor 1 becomes equal to or lower than the reference speed Nth. However, whether the speed of the motor 1 is equal to or lower than a predetermined speed is determined. Judgment threshold (reference speed Nth)
It is also possible to consider that the motor 1 is reversed at the time when it is determined that the speed is equal to or lower than the reference speed Nth in step S6 by sufficiently lowering.

FIG. 6 is a flow chart for explaining another control operation of the motor control unit 6. The flowchart shown in FIG. 6 shows an example in which the motor control unit 6 uses the acceleration data to detect the reversal time of the motor 1. Referring to FIG. 6, when a reversing instruction is given to the motor control section 6 from the main body control section that controls the entire automatic document feeder, the motor control section 6 outputs the reversal instruction to the driver 7. , The abnormality detection timer 3 is started (step S21).

Then, the timer 1 is started (step S22). The timer 1 is for measuring a unit micro time Δt. Next, the pulses input from the photo interrupter 5 are counted (step S2).
3). Then, until the unit minute time Δt elapses,
The pulse counting continues. This pulse counting is performed by the up counter 6 as described with reference to FIG.
The number of pulses is counted at 2 and the number of reference clocks during that time is counted at the capture register 64.

When the unit minute time Δt elapses,
The pulse width is based on the number of pulses of the up counter 62 (UDCn-UDCm) counted during the unit minute time Δt and the change in the number of counts of the capture register 64 (CPTn-CPTm) during the unit minute time Δt. The data CWDT is obtained, and the rotation speed N of the motor 1 is obtained based on the equation (2) (step S2).
5).

Further, the acceleration α during the unit minute time Δt is calculated (step S26). The acceleration α is obtained by the above-mentioned formula (3). Then, the next step S2
In 7, it is determined whether or not the speed N calculated in step S5 is less than or equal to the reference speed Nth. As a result, if the calculated speed N is not less than or equal to the reference speed Nth, then
It is determined whether or not the timer 3 has timed out (step S28).

As described above, the timer 3 is an abnormality detecting timer, and is for measuring a time necessary and sufficient for detecting the reverse rotation of the motor 1. Therefore, in the normal state, the timer 3 does not expire at this point,
The control from step S22 is repeated, the speed N during the next unit minute time Δt is calculated, and the acceleration α during that time is obtained (steps S22 to S26).

If it is determined in step S28 that the timer 3 has timed out, the speed N of the motor 1 is set to the reference speed N within the time necessary and sufficient for reversing the motor 1.
Since it has not become less than th, it is judged to be abnormal and the motor 1 is stopped (step S29).
As described above, in this embodiment, the motor 1 is controlled so as to be immediately stopped as a protective operation based on the time-up of the timer 3.

Instead of immediately controlling the motor 1, the motor 1 may be driven at a predetermined low speed for a predetermined time and then stopped. In normal control, it is determined in step S27 that the calculated rotation speed N has become equal to or lower than the reference speed Nth before the timer 3 times out. Then, it is determined whether or not the acceleration α has become positive (step S30). Acceleration α
2D is negative while the motor 1 is decelerating and is positively reversed when the motor 1 is in an accelerating state, as shown in FIG. 2D. Therefore, when the acceleration α is not positive, that is, when the acceleration α is negative, the motor 1 is not reversing and is decelerating.

If the acceleration α is not positive, then it is determined whether the timer 3 has timed out (step S31). If the acceleration α does not become positive by the time the timer 3 times up, the reversal of the motor 1 is not detected within the time necessary and sufficient for reversal detection.
It is determined that there is an abnormal situation, and the motor 1 is stopped (step S29).

In a normal state, in step S31, it is determined that the timer 3 has not timed up, so in step S30, the reversal of the motor 1 is detected when the acceleration α becomes positive (step S30). S3
2). The flowcharts shown in FIGS. 5 and 6 above are
The control according to the embodiment of the present invention is not limited to the flowcharts of FIGS. 5 and 6, and various modifications can be made.

[0044]

The present invention is configured as described above, and the motor reversal timing can be accurately determined with an inexpensive structure, and if the motor reversal timing is not determined, Since it is determined that the motor is in an abnormal state and the motor is stopped, it is possible to provide a motor control device that is highly safe and can detect the reversal timing of the motor inexpensively and accurately.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a motor control device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a relationship between a reversal command, an actual motor speed, and detected motor speed data in the motor control device according to the embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a pulse width data calculation circuit in an embodiment of the present invention.

FIG. 4 is a diagram for explaining a calculation principle of a pulse width.

FIG. 5 is a flowchart showing the contents of motor reversal detection control in one embodiment of the present invention.

FIG. 6 is a flowchart showing the contents of motor reversal detection control in another embodiment of the present invention.

FIG. 7 is a waveform diagram for explaining the principle of detecting normal rotation and reverse rotation of a conventional two-phase encoder.

[Explanation of symbols]

 1 motor 2 load 3 detection device 5 photo interrupter 6 motor control unit

Claims (1)

[Claims] 1. A rotation signal output unit that is connected to a rotation shaft of a motor and outputs a rotation signal in association with the rotation of the motor, and a rotation signal output from the rotation signal output unit.
A speed calculation means for calculating the rotation speed of the motor, a means for outputting a reversal instruction to the motor, and a check as to whether or not the rotation speed of the motor calculated by the speed calculation means after the reversal instruction is output is below a predetermined reference speed. And a reversal detection unit that determines the reversal time of the motor in response to the discrimination unit determining that the rotation speed has become equal to or lower than the reference speed. A motor control device comprising: an abnormality processing unit that performs abnormality processing when a reversal time point is not detected.