JPH03218288A - Motor controller - Google Patents

Abstract

PURPOSE:To detect rotational state of a motor accurately, even when the retional speed is low, by providing means for comparing a period data, calculated through a calculating means, with the content of a memory means and judging the number of revolution of the motor with reference to a target number of revolution of the motor. CONSTITUTION:A control section 14 makes a judgement whether the content of a capture register 134 and an up/down counter is updated. If it is updated, the count set in a down counter is decremented by 1. Then, a judgement is made whether the count in the down counter is 0, and if it is not 0 current processing is completed, whereas when the count in the down counter is 0 a next operation prohibiting flag is reset to L.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a motor control device, and particularly to a motor control device that can accurately detect the rotational state of a motor at low speeds.

BACKGROUND ART In order to control a motor to a desired state, it is necessary to be able to accurately detect the rotational speed of the motor.

Conventional motor rotational speed detection devices generally detect rotational speed based on, for example, the number of output pulses of a rotary encoder coupled to a motor rotation shaft.

Problems to be Solved by the Invention When the motor rotation speed is relatively high, the number of pulses output from the rotary encoder is large, so the rotation of the motor can be accurately determined based on the number of pulses output within a certain time. Speed can be calculated.

However, as the motor rotation speed becomes slower,
Since fewer pulses are output from the low-resolution encoder, calculation of the motor rotational speed becomes difficult and inaccurate.

For example, in a method of counting the number of pulses of a low-return encoder output at regular intervals and calculating the motor rotation speed based on the number of pulses, the output interval of the pulses is smaller than the detection interval. If it is too long, there is a risk that it will be erroneously determined that the motor has stopped completely even though it has not.

The present invention was made in order to eliminate such drawbacks, and it is an object of the present invention to provide a motor control device that can accurately detect the rotational state of the motor even when the motor rotational speed becomes low. purpose.

Means for Solving the Problems This invention provides a rotation signal output means that is connected to a rotation shaft of a motor and outputs a signal that changes periodically in conjunction with the rotation of the motor, and a rotation signal output means that outputs a signal that changes periodically in conjunction with the rotation of the motor. It has a detection means for detecting a change in the signal, a calculation means for calculating period data of the signal based on the output of the detection means, and a storage means in which period data corresponding to the target rotation speed is stored in advance. The motor control device is characterized in that it includes a determining means that compares the calculated cycle data with the contents of the storage means and determines what state the motor rotation speed is with respect to the target rotation speed.

Further, the present invention further provides a counting means whose count value is changed by a predetermined value when the detection means does not detect any change in the signal during a fixed interval, and a count value of the counting means is predetermined. The present invention is characterized in that it includes a determining means for determining that the motor rotation speed has decreased to a predetermined rotation speed when the motor rotation speed reaches a predetermined rotation speed.

Effects> Based on the change in the rotation signal detected by the detection means, such as the rising edge of a pulse, period data of the signal, such as pulse width data, is calculated.

The calculated period data is compared with period data corresponding to the target rotation speed stored in advance in the storage means, and if the calculated period data is larger than the period data corresponding to the target rotation speed, the motor rotation speed is It is determined that the motor rotation speed is lower than the target rotation speed, if it is smaller, it is determined that the motor rotation speed is higher than the target rotation speed, and when the two match, it is determined that the motor rotation speed is the target rotation speed. .

Further, according to a preferred aspect of the present invention, when no change in the signal is detected at all during a fixed interval, the count value of the counting means is changed by a predetermined value, and when the predetermined value reaches a fixed value, , the motor is determined to have stopped.

Embodiment A control device for a DC servo motor for driving an optical system (illumination unit and reflection mirror) of a copying machine will be described below as an embodiment of the present invention.

FIG. 1 is a block diagram showing an example of the configuration of a control circuit for a DC servo motor for driving an optical system of a copying machine. This control circuit uses PWM (pulse width modulation) as the voltage applied to the DC servo motor.
n) signals are used.

This DC servo motor 0 is of a permanent magnet field type, and is rotationally driven by a driver section 11.
Move 7.

Rotary encoder 12 is installed on the rotation axis of servo motor 0.
are connected. As already known, the rotary encoder 12 outputs a speed detection pulse every time the servo motor 0 rotates by a predetermined minute angle. The rotary encoder 12 of this embodiment outputs A-phase and B-phase speed detection pulses (speed detection signals) that have the same period and are out of phase by 90 degrees, and when the servo motor 0 rotates once, each For example, 200 speed detection pulses are output.

Note that instead of the rotary encoder 12, another device that outputs a signal that periodically changes in conjunction with the rotation of the servo motor 10 may be used.

The speed detection pulse output from the low-resolution encoder 12 is given to the encoder signal input section 13. The encoder signal input unit 13 is a circuit for detecting the rotational speed of the servo motor 10 based on the speed detection pulse given from the rotary encoder 12, as will be described in detail later. The output of the encoder signal input section 13 is given to the control section 14.

The control unit 14 includes a CPU, an R for storing programs, etc.
It is equipped with an OM, a RAM for storing necessary data, etc., and is used to calculate the difference between the command speed and the detected speed, calculate the phase difference between the speed command signal and the speed detection signal, and to control the servo motor 10. PWM data calculation processing and the like are performed.

The control section 14 is given an operation command signal and a speed command signal (speed command clock) from a control section (not shown) of the main body of the copying machine. The speed command clock is signal-processed by the speed command signal input section 15 and then returned to the control section 14.

The PWM unit 16 receives PW from the control unit 14.
PWM of pulse width (output duty) according to M data
This is a unit for generating signals. The servo motor 1 is activated by the PWM signal output from the PWM unit 16.
0 rotation speed is controlled.

The driver section 11 determines the rotation direction of the servo motor 10 and performs braking based on a driver section drive signal given from the control section 14 .

Next, the configuration of this embodiment regarding detection of the rotational speed of the servo motor 10 will be explained.

FIG. 2 is a diagram showing an example of the configuration of the encoder signal input section 13. To explain with reference to FIG. 2, the encoder signal input section 13 includes a rising edge detection circuit 131 that detects the rising edge of the A-phase speed detection pulse sent from the rotary encoder 12, and a rising edge detection circuit 131 that up-counts the reference clock. For example, a 16-bit free running counter 133 and a rise detection output of the rise detection circuit 131 are used as capture signals, and a capture register 34 is provided which reads and holds the count of the free running counter 33 using the capture signal as a trigger.

The reference clock is a reference clock that serves as a reference for the operation timing of the entire circuit shown in FIG. 1, and when the circuit is composed of a microcomputer, a machine clock is used. Furthermore, if such a reference clock does not exist, a reference clock generation circuit may be provided.

The encoder signal input section 13 further includes an up/down detection section 135 and an up/down counter 136. The up/down detection section 135 includes a rise detection circuit 1
When the rising detection output of the A-phase speed detection pulse is given from 31, the level of the B-phase rotation pulse is determined, and depending on whether the B-phase rotation pulse is high level or low level, the servo motor 10 (Fig. 1) This is to determine whether the motor is rotating forward or backward. The up/down counter 9 136 counts up or down the detection output of the rising edge detection circuit 131 based on the determined output of the up/down detection section 135.

Next, the operation of the circuit shown in FIG. 2 will be explained.

The contents of the capture register 134 include the capture signal,
That is, it is updated every time the rising edge of the A-phase speed detection pulse is detected. Further, the up/down counter 136 counts the number of times the rising edge of the speed detection pulse is detected, in other words, the number of speed detection pulses.

Therefore, if n speed detection pulses are counted by the up/down counter 136 within a predetermined sampling time ΔT, and the number of reference clocks counted by the free running counter 133 during that period is measured, then
Based on this, the rotation speed N can be calculated.

In other words, the rotation speed N [rpm] of the servo motor 10 is the frequency of the reference clock f [Hzl], and the number of A-phase speed detection pulses output from the rotary encoder 10 and the coder 12 when the servo motor 10 rotates once is C.
[ppr], the contents of the current capture register 131 are CPTn, and the contents of the previous capture register 131 are CPTn.
PTn, CP the contents of the previous capture register 131
T. -+, it can be calculated as f... (1).

Here, in equation (1), since the reference clock frequency f and the speed detection pulse number C are constants, N=n A
= Animal A...(2) CPT, -CPT,
-, X However, A: LX60 C X: CPT, CPT0-+.

FIG. 3 shows a rotation speed detection processing procedure in which the control unit 14 reads out the contents of the capture register 134 and the up/down counter 136 every 11 sample times Δt to calculate the rotation speed data N.

The sample time Δt is Δt≧X=CPT. , -CPT, -+ ·= An appropriate time that satisfies (3) is set.

Next, explanation will be given with reference to FIGS. 2 and 3.

In the control unit 14, an internal timer keeps a constant sampling time Δt.
Each time the timer reaches (step S1), the timer is reset (step S2). And capture register 1
34 and the contents of the up/down counter 136 are read out (step S3).

Next, from the count number CPTll of the capture register 134 read this time (n is a natural number and increases as 1.2, 3, etc. at each detection timing),
The previously stored count number CPT of the capture register 134 that was read last time. After the reference clock number X within one sample time Δt is determined by subtracting -1, CPTfi is stored as 12 (step S4).

Also, the count number UDC of the up/down counter 136 read this time. (n is a natural number and increases as 1.2, 3, etc. at each detection timing.) From this, the count number of the up/down counter 136 that is already stored and read last time UD C n-1 After the number n of rotational pulses within one sample time Δt is determined by subtracting Δt, UDC is stored (step S5).

Then, based on the above equation (2), the servo motor 1
The rotation speed N of 0 is determined (step S6).

The above is an explanation of the method for calculating the rotation speed data N of the servo motor 10.

Next, control when stopping or reversing the servo motor 10 will be explained. In this embodiment, the deceleration control is continued without suddenly stopping or reversing the servo motor 10 until the rotation speed of the servo motor 10 falls below a predetermined extremely low rotation speed.

That is, when stopping the servo motor 10, for example, the control section 14 adjusts the PWM signal to first reduce the rotational speed of the servo motor 10. and,
Until the rotational speed of the servomotor 10 falls below a predetermined rotational speed, it is prohibited to completely stop the rotation of the servomotor 10. This reduces the risk of lamp burnout in the system and wear of the sliding members used to move the optical system.

More specifically, referring to FIG. 4, during deceleration control, the control unit 14 determines whether the contents of the capture register 134 and up/down counter 136 (see FIG. 2) have been updated at a predetermined interrupt timing, etc. A determination is made as to whether this is the case (step S11).

When the contents of the capture register 134 and the up/down counter 136 are updated, a predetermined number Z is set in a predetermined subtraction counter (step S12);
Calculate the pulse width W, (n is a natural number and increases as 1.2, 3, etc. every 14 calculation timings) based on the updated contents of the capture register 134 and up/down counter 136. is performed (step 813).

The pulse width W0 is calculated based on the following equation.

Wfi=X/n...(4)
However, X = C P T ,, C P T o− +
n = UDco - UDCo In other words, the pulse width W0 is not calculated based on the number of speed detection pulses detected within a certain period of time, for example, sample time Δt, as in conventional devices, but is calculated based on the rise of a certain rotation detection pulse. The width from the edge to the rising edge of the next rotational pulse is expressed by the number of reference clocks, and the number of reference clocks is the pulse width W. It is said that Therefore,
Pulse width W compared to conventional equipment. is calculated extremely accurately, and the rotational speed of the motor is detected accurately.

Then, the pulse width Wn is a predetermined value W. compared to
W, <W. In this case (YES in step S14), the next operation 15 prohibition flag that prohibits the next operation, for example, the operation to completely stop the servo motor 10, is set to "H" (step S15).
).

On the other hand, the pulse width is W. If ≧Wo (No in step S14), the next operation prohibition flag is reset to "L" (step S16).

As a result, in the control unit 14, the next operation prohibition flag is set to “H”.
, even if a stop command, reverse command, etc. is given from the control unit (not shown) of the copier main body, the stop control etc. cannot be performed immediately, and the next operation prohibition flag is set to "L". In other words, the stop control etc. are temporarily suspended until the rotational speed of the servo motor 10 becomes equal to or less than a predetermined speed.

Therefore, when the servo motor 10 is at a predetermined speed or higher, the servo motor 10 is not immediately stopped or reversed, so that shocks, vibrations, etc. that occur when the servo motor 10 is stopped or reversed are eliminated. It can be random or extremely small.

Therefore, in the copying machine, image distortion does not occur at the leading edge of the next copy, especially in the case of continuous copying 16.

By the way, in step Sll, if the values of the capture register 134 and the up/down counter 136 are not updated, a conventional control device would immediately determine that the servo motor ]0 has stopped.

However, in this embodiment, the servo motor 1 is
It is accurately determined whether or not 0 has been completely stopped.

If NO in step Sll, the count value Z set in the subtraction counter is decremented by "1" (step S17). Then, it is determined whether the count value of this subtraction counter is "0" (step 818).
), if the count 1 value of the subtraction counter is not "0", the current process is terminated, and if it is determined that the count value of the subtraction counter is "0", the next operation prohibition flag is set to "L". , and the next operation, which is to completely stop the motor 10, is made possible (step s19).

In other words, the rotation of the rotary encoder 12 within a certain period of time (in this embodiment, the certain period of time is, for example, a predetermined interrupt time width, but instead may be the sample time Δt in FIG. 3). However, the rising edge of the speed detection pulse is not output, and the capture register]. If the contents of 34 are not updated a predetermined number of times and the rising edge of the speed detection pulse is not detected within a predetermined times the predetermined time, the control unit 14 performs the next operation, for example, the control of the servo motor 1o. It is possible to perform the action of completely stopping the machine.

In the above embodiment, during deceleration control, it is determined whether or not the contents of the capture register 134 and up/down counter 136 have been updated (step S11);
Predetermined processing is performed both when there is an update and when there is no update, but the processing when there is an update of the contents, that is, step Sl
The deceleration control may include the processes of 1, S18 12, S13, S14, S15, and S16.

Alternatively, the process when the contents are not updated, that is, steps Sll, S17, S18. The deceleration control may include only the processing in S19.

The present invention is applicable not only to control of the optical system of a copying machine but also to a motor for controlling a reading device of a facsimile machine and other general motor control circuits.

Further, the present invention can be applied to the case where the applied voltage is calculated using other than PWM signals.

Effects of the Invention> Since the present invention is configured as described above, it is possible to accurately judge the state from when the motor rotates at a low speed until it stops, and it is possible to accurately judge the state from when the motor rotates at a low speed until it stops, and to determine whether the motor is at the target stopping speed or when the motor is stopped. The possible rotational speed can be detected accurately.

Furthermore, according to the present invention, since it is possible to accurately judge the rotational state at extremely low speeds, it is possible to perform stable control and control that suppresses the generation of vibrations and shocks when controlling the motor to stop or perform braking control. I can do that.

Further, according to the present invention, even when a rotation signal output means that outputs a signal that periodically changes in conjunction with the rotation of the motor, such as an encoder with not very high resolution, is used, the low speed state of the motor can be detected. Can be accurately determined.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the electrical configuration of a drive control circuit of a DC servo motor for driving an optical system to which an embodiment of the present invention is applied. FIG. 2 is a circuit block diagram showing the electrical configuration of the encoder input section according to the embodiment of the invention. FIG. 3 is a flowchart showing the rotational speed detection processing procedure in the embodiment of the present invention. FIG. 4 is a flowchart showing the details of the deceleration control process performed by the control section 14. In the figure, 10...DC servo motor, ]1...
Driver section, 12... Rotary encoder, 13...
・Encoder signal input section, 14...control section, 15...
・Speed command signal input section, 16... PWM unit, 20 is shown. 21

Claims (1)

[Claims] 1. Rotation signal output means connected to the rotation shaft of the motor and outputting a signal that changes periodically in conjunction with the rotation of the motor; detecting changes in the signal output from the rotation signal output means; A detection means for calculating period data of the signal based on the output of the detection means, and a storage means in which period data corresponding to the target rotation speed is stored in advance, and the period data calculated by the calculation means is stored in advance. A motor control device comprising: determining means for determining the state of the motor rotation speed relative to a target rotation speed by comparing the contents of the storage means. 2. The motor control device according to claim 1 further comprises: counting means for changing the count value by a predetermined value when the detection means does not detect any change in the signal during a certain interval;
and determining means for determining that the motor rotation speed has decreased to a predetermined rotation speed when the count value of the counting means reaches a predetermined value.