JPH03198677A - Motor controller - Google Patents

Abstract

PURPOSE:To obtain an accurate speed by outputting data corresponding to a center of large and small values of data of a plurality of times stored in a storage means as speed data for controlling a motor each time data regarding a motor rotating speed is calculated. CONSTITUTION:Data regarding the rotating speed of a motor 10 is calculated at each predetermined timing. When the data regarding the rotating speed of the motor 10 is calculated, data of past predetermined rotation stored already in a storage means of a controller 14 is sequentially shifted by one and the data calculated this time is stored in a latest data storage area. Data corresponding to a center of large and small values of data of predetermined number stored in the storage means is output as speed data to be used for controlling the motor 10. Thus, even if a speed detection signal is temporarily varied due to noise or the like, an accurate speed can be obtained without influence of its variation.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a motor control device.

<Background of the Invention> For example, in a DC servo motor control device for driving an optical system in a document reading device such as a copying machine, even if the motor load fluctuates due to changes in frictional resistance etc. as the optical system moves, it is difficult to follow the It is necessary to maintain the servo motor at a constant speed and move the optical system at a constant speed.

In order to keep the servo motor at a constant speed, it is necessary to accurately detect the actual rotational speed of the servo motor.

In conventional devices, the rotational speed of the servo motor is detected at predetermined timings based on the output (speed detection signal) of a speed detector such as an encoder connected to the servo motor.

However, the method of speed detection in conventional devices is
If the detected rotational speed is affected by noise or the like, there is a drawback that the motor rotational speed cannot be detected accurately.

Therefore, in order to eliminate errors caused by noise etc.
Some methods have been adopted, such as finding the average of the previously detected speed and the currently detected speed, and taking that as the current speed.

<Problem to be solved by the invention> However, in the method of calculating the average detection speed,
Since we are trying to reduce the error by averaging the detected speeds, even if an accurate rotational speed is detected, the speed will be averaged and will remain constant relative to the original speed (actual speed). This will result in a deviation of

Furthermore, if temporally large noise occurs, the noise error cannot be removed even if it is averaged, and a relatively large error remains in the speed after averaging.

For this reason, for example, if such large noise occurs in a steady state, speed unevenness will occur.

This invention was made in view of the above circumstances, and
It is an object of the present invention to provide a motor control device that can obtain an accurate speed without being affected by the fluctuation even if a speed detection signal fluctuates greatly over time due to noise or the like.

Means for Solving the Problems> The present invention provides a calculation means for calculating data regarding the motor rotation speed at each predetermined timing in a motor control device that performs feedback control of the motor so that the motor rotation speed becomes equal to the command speed. , has a plurality of storage areas that can store data related to the motor rotation speed for a predetermined plurality of times in chronological order, and shifts already stored data one by one each time data related to the motor rotation speed is calculated. and storage means for storing the data calculated this time in the latest data storage area, and means for retrieving data corresponding to the middle of the magnitude from among the plurality of data stored in the storage means as speed data to be used for motor control. It is characterized by having the following.

Function> Data regarding the motor rotation speed is calculated at each predetermined timing.

When the data regarding the motor rotation speed is calculated, the data for a predetermined number of times in the past already stored in the storage means are sequentially shifted one by one, and the data calculated this time is stored in the latest data storage area.

Of the predetermined number of data stored in the storage means, data corresponding to the middle of the magnitude is taken out as speed data to be used for the motor control.

<Embodiment> An embodiment of the present invention will be described below, taking as an example a case where the present invention is applied to a control circuit of a DC servo motor for driving an optical system (illumination unit and reflection mirror) of a copying machine.

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.
When the motor rotates once, each phase, for example, 200 speed detection pulses are output.

The speed detection pulse output from the low-resolution encoder 12 is given to the encoder signal input section 13. The encoder signal input section 13 is a circuit for detecting the rotation speed of the servo motor 0 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 human input section 13 is given to the control section 14.

The control unit 14 includes a CPU, an RO that stores programs, etc.
M, is equipped with RAM etc. to store necessary data,
Calculation process of difference between command speed and detected speed, calculation process of phase difference between speed detection signal and speed command signal, servo motor 10
Performs processing such as calculation of PWM data for controlling.

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 control section 14 executes arithmetic processing based on each input signal, calculates PWM data, and provides it to the PWM unit 16, and also provides a driver section drive signal to the driver section 11 described above.

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. Further, the driver unit drive signal determines the rotation direction of the servo motor 10 and performs braking.

By the way, in order to rotate the servo motor 10 at a desired command speed, it is necessary to accurately detect the rotation speed of the servo motor 10 as a premise.

Therefore, in this control circuit, the encoder signal input section 13
The configuration is as shown in FIG. 2, and the signal reading by the control section 14 is devised so that accurate speed detection can be performed.

To explain with reference to the m2 diagram, encoder signal input section 1
3 is a rise detection circuit 13 that detects the rise of the A-phase speed detection pulse sent from the rotary encoder 12;
1. The rising edge detection output of the free running counter 133 having, for example, a 16-bit configuration and the rising edge detection circuit 131 that counts up the reference clock is used as a capture signal.

A capture register 134 is provided which reads and holds the count of the free running counter 133 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. Also, if there is no such reference clock,
A reference clock generation circuit may also 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. Up/down counter 136
is based on the discrimination output of the up-down detection section 135,
The detection output of the rising edge detection circuit 131 is counted up or down.

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

The contents of the capture register 34 are the catch signal,
That is, it is updated every time the rising edge of the A-phase speed detection pulse is detected. In addition, up/down counter 13
6 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, within a predetermined sampling time Δτ, if the up/down counter 136 counts n rotation pulses, and during that time the free running counter 133 measures the number of reference pulses, the number of rotations will be calculated based on that. N can be calculated.

In other words, the rotation speed N [rpm] of the servo motor 10 is determined by the frequency of the reference clock being f [Hz], and the number of rotation pulses of the A phase output from the rotary encoder 12 when the servo motor 10 makes one rotation C [ppr]. ], the current content of the capture register 131 is CPT, and the previous content of the capture register 131 is CP T o-+, then it can be calculated as 0 - X60 (1).

Here, in equation (1), since the reference clock frequency f and the number of rotational pulses C are constants, N=nA-U...(2)C
PT, -CPTfi-1X However, A knee! -X60 X: CPT, CPT, -+.

FIG. 3 shows a motor rotational speed detection processing procedure by the control unit 14, and FIG. 4 shows two types of memories M1 and M2 used in this processing.

In FIG. 4, the memory M1 is for storing rotation speed data for five times in order from the newest to the oldest rotation speed data storage area. It has five storage areas E1 to E5 in order.

In other words, El is the current rotational speed data N. However, E2 contains the previous rotation speed data N. -1, E3 has the rotation speed data Nfn-21 two times ago, and E4 has the rotation speed data N three times ago. -1 is the rotation speed data Ntn-4 4 times before E5
+ are respectively memorized.

The memory M2 is for sorting, that is, arranging in order of size, the five rotational speed data N,...~N(n-4+) stored in the memory M1, and has five storage areas E.
It has 11 to E15. 5 stored in memory M1
rotation speed data N. -N(++-41 is sorted and stored in memory M2, for example, area E
5 rotation speed data N n-N t n -4)
The largest one is in area E12, the second largest one is in area E13, the third largest one is in area E12, and the third largest one is in area E13.
The fourth largest one is stored in area Ell, and the smallest one is stored in area Ell. Therefore, in area E13, memory M
Among the five rotation speed data stored in No. 1, the rotation speed data corresponding to the center of the magnitude is stored.

2 Returning to FIG. 3, the motor rotation speed detection process is performed every sample time Δt.

The sampling time Δt is set to an appropriate time that satisfies the following: Δt≧X−CP T, CP Tn−+ −(3).

Next, explanation will be given with reference to FIGS. 1 to 4.

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 the contents of the capture register 134 and up/down counter 136 are read (step S3).

Then, from the count number CPTf of the capture register 134 read this time, the count number CPTf of the capture register 134 read last time that has already been stored is calculated.
After the reference clock number X within one sample time Δ is obtained by subtracting i-+, CPT is stored (step S4).

In addition, by subtracting the previously stored count number UDC, -1 of the up-down counter 1336 read last time from the count number UDC, of the up-down counter 136 read this time, one sample time Δ is After the number of rotational pulses n is determined, U
DC, is stored (step S5).

Thereafter, the rotation speed N of the servo motor (current rotation speed data Nn) is calculated based on the above-mentioned equation (2) (step S6).

When the rotation speed data N, , is calculated, the five rotation speed data N7 to N(II-
41 is shifted (step S7). As a result, the rotation speed data up to that point is N. is stored in area E2 as N(II-1), rotational speed data N(n-11 is stored in area E3 as N(n-2), and rotational speed data N,,2) is stored as N(n-3).
), the rotation speed data N(a-3) is N in area E4.
) is stored in area E5, and the rotation speed data NLn-4, up to that point, is no longer stored.

Then, the rotation speed data N calculated this time. is area E1
(Step S8).

Next, five rotation speed data N stored in the memory M1. -N(*-4+ is sorted and stored in 4 memory M2 (step S9). As a result,
In the areas E11 to E15 of the memory M2, five rotation speed data N0 to N (11-41 are stored in ascending order. In this case, the area E13 stores five rotation speed data N.
4 to N (n-4), rotation speed data (center data N,) corresponding to the center of magnitude is stored.

Then, the central data N stored in the area E13 of the memory M2 is taken out as the current motor rotation speed N and stored in, for example, a buffer (step 510).

That is, in step SIO, the rotation speed data N corresponding to the middle of the five rotation speed data for the current time and the past four times is taken out as the current motor rotation speed N.

According to the above-mentioned motor rotation speed detection process, the rotation speed data N corresponding to the center of magnitude among the five rotation speed data for this time and the past four times is taken as the current rotation speed N. Even if the detection signal fluctuates and incorrect rotational speed data N, , is calculated in step S6, the rotational speed data N, ... will not be used as the rotational speed N. Therefore, accurate rotation speed detection is possible, and the motor rotation speed can be maintained at a desired speed.

Note that each time a speed detection pulse is output, the count number CPT of the capture register 134 is read out, the previous count number CPT is subtracted to calculate the cycle of the latest speed detection pulse, and based on this cycle, the cycle of the latest speed detection pulse is calculated. Rotation speed data N.

You may also ask for

Next, the speed command signal input section 15 will be explained in detail.

FIG. 5 is a block diagram showing a specific example of the configuration of the speed command signal input section 15. As shown in FIG. In the speed command signal input section 15,
A rise detection circuit 151 for detecting the rise of the speed command clock, a free running counter 152 for up-counting the reference clock, and a rise detection output of the rise detection circuit 151 are used as a capture signal, and the capture signal is used as a trigger to control the free running counter 152. It includes a capture register 153 that reads and holds the number of colors, and an up counter 154 that counts up the output pulses of the rising edge detection circuit 151.

Free running counter 152 is, for example, a 16-bit counter. This free running counter 152 may also be used in common with the free running counter 133 of the encoder signal input section 13 described above.

The operation of this circuit is as follows.

A speed command clock outputted from a control side microcomputer on the apparatus main body side, for example, a copying machine main body, is applied to a rising edge detection circuit 151, and a rising edge is detected. Since the output of the rising edge detection circuit 151 is given to the free running counter 152 as a capture signal, the contents of the capture register 153 are updated in response to the rising edge of the speed command clock. Therefore, by reading the contents of the capture register 153 based on a certain rising detection signal, reading the contents of the capture register 153 based on the next rising detection signal, and finding the difference, the free running counter in one cycle of the speed command clock can be calculated. A count of 152 can be measured. In other words, the rotation speed N is the command speed.

can be obtained.

Note that in this embodiment, each time the contents of the capture register 153 are updated, the difference between the count number after the update and the count number before the update is calculated. , the same reading method as the count number reading of the capture register 153 in the encoder signal input section 13 is used.

That is, the control unit 14 reads the contents of the capture register 153 and the contents of the up counter 154 at every predetermined sampling time Δt, calculates the difference between the count number read this time and the count number read last time in the capture register 153, and calculates the difference between the count number read this time and the count number read last time in the capture register 153. By dividing the difference by the difference between the count number read this time and the count number read last time in the up counter, a more accurate number of reference clocks within one cycle of the speed command clock is obtained.

FIG. 6 shows a procedure for calculating the phase difference between the speed command clock and the speed detection pulse by the control unit 14.

First, the rising edge detection circuit 13 of the encoder signal input section 13
1, when the rising edge of the speed detection pulse is detected (step 511), the count value of the free running counter 133 is read and the value is stored as the phase comparison value PDT (step 512). Since the free running counter 133 starts counting the reference clock from the start of motor control, the value of the phase comparison value PDT is a value corresponding to the time from the start of motor control to the current pulse rise detection point. Become.

Next, the phase reference value PPI. is calculated and stored according to the following equation (step 813).

PPl1l=PPI(-++ 10SPD...(
4) Here, PPI(n-1>'previously stored phase reference value 9 SPD: number of reference clocks during one period of speed command clock (SPD is a fixed value).

However, since the initial value of P P I L-1) is zero, the corresponding phase reference value P P1. The value of is SPD.

Thereafter, the phase difference PHDT is calculated using the following equation and stored (step 514).

PHDT-PP1 "-PDT" (5) SPD Then, the above processing is repeated. That is, every time the rising edge of the speed detection pulse is detected (step 511)
, reading the count value of the free running counter 133 and the phase comparison value PDT. Update (step 512)
, calculation and update of phase reference value PPl0 (step 51
3) and calculation of phase difference PHDT (step 514)
is repeatedly zeroed.

After the start of motor control, when the second rising edge of the speed detection pulse is detected in step Sll, the process proceeds to step 3.
The value of the phase reference value PPl7 calculated in step 13 is 2SPD, and becomes 3SPD when the third rising edge of the speed detection pulse is detected. That is, the phase reference value PPI calculated in step 813. The value is the product of SPD and the total number of speed detection pulses output from the start of motor control to the current rise of the speed detection pulse.

Since SPD is a fixed value depending on the period of the speed command clock, the phase reference value PPI calculated in step 813
n is a value corresponding to the time from the start of motor control to the time of the rise of the speed command clock corresponding to the speed detection pulse whose rise was detected this time.

Then, a value (phase comparison value PD
T, ) and the value (phase reference value PPI,) corresponding to the time from the start of motor control to the rising point of the speed command clock corresponding to the speed detection pulse whose rising edge was detected this time is calculated as the speed command value. The phase difference PHDT is obtained by dividing by a value (SPD) corresponding to the clock cycle. Therefore, even if the phase difference between the speed command clock and the speed detection pulse is one cycle or more of the speed command clock, the phase difference PHDT can be accurately detected.

Next, a method for calculating PWM data output from the control unit 14 will be explained.

The rotation speed N of the servo motor 10 is the command speed N.

The voltage vO that should be output to the servo motor 10 in order to make it follow
It is expressed by the following formula.

VO-V1+V2-(6) That is,
In this example, the speed difference ΔN (-N.

-N) is corrected by the control voltage v2 based on the phase difference PHDT. The reason for this is that proportional control based on the speed difference ΔN alone does not allow the acceleration when increasing the motor speed from the actual detection 2 speed to the target speed to change depending on the size of the target speed. This is because it takes a long time to reach , and the followability is not good.

Therefore, in order to improve followability, in this embodiment, the control voltage V1 based on the speed difference ΔN (-N.-N) is corrected by the control voltage V2 based on the phase difference PHDT.

The control voltage 2 due to the phase difference PHDT is obtained, for example, as follows, assuming that the maximum value of the predetermined control voltage v2 is α.

(a) When the phase difference is smaller than one period (-1<PHDT<+1) V2-a ・PHDT -(7)(b
) When the phase difference is one cycle or more and the phase of the speed detection signal is ahead of the phase of the speed command signal (PHDT≦-1) V2--α ... (8) 3 (c) The phase difference is 1 If the period is longer than that and the phase of the speed detection signal lags the phase of the speed command signal (PHDT≧+1) V2−1α (9) Therefore, the relationship between the phase difference PHDT and the control voltage V2 is , 7th
The relationship shown in the figure is obtained.

The control voltage v1 due to the speed difference ΔN is calculated using the following formula (%) Ra: amateur resistance [Ω] KT: ) torque constant [kgm/A] Ke: induced voltage constant [V/rpm Io = no-load current [ A] 4 (10) GD2: Moment of inertia due to load and motor [kg
m2] TBL: Sliding load [kgm.

The control unit 14 detects the rotation speed N of the servo motor 1o (step s6 in FIG. 3), and calculates the speed difference Δ from the command speed N0.
Each time N is calculated or the phase difference PHDT is calculated (step 514 in FIG. 6), the above equations (6) to (
1o), calculate VO and set PW accordingly.
Output M data. This PWM data is sent to the PWM unit 16, and the servo motor 10 is controlled via the driver section 11.

FIG. 8 is a block diagram showing a specific example of the configuration of the PWM unit 16, and FIG. 9 is a timing chart for explaining the operation of the PWM unit 16.

The PWM unit 16 includes a set signal generation section 161,
PWM data register 162 and down counter 163
and RS flip-flops 164 and 5.

The set signal generator 161 generates a set signal at regular intervals. This set signal generating section 161
is composed of, for example, a ring counter, and is configured to generate a set signal every time a certain number of reference clocks are counted.

The PWM data register 162 is for holding PWM data given from the control unit 14. The PWM data given from the control unit 14 is expressed by the above-mentioned formula (6
) is the voltage data determined by That is, it is the voltage vO obtained by correcting the voltage (1) in equation (10) with the control voltage V2 based on the phase difference data PHDT. This PWM data is used to determine the duty of the PWM output signal output from the PWM unit 16.

The down counter 163 counts down every time a PWM reference clock (in this embodiment, the PWM reference clock is a reference clock used in the encoder signal input section 13 and the speed command signal input section 15) is provided. When the set number is counted, a reset signal is output.

The operation of the PWM unit 16 is as follows.

When the set signal is output from the set signal generating section 161, the contents of the PWM data register 162, that is, the control section 1
The PWM data given from 4 is sent to the down counter 16.
3, and the flip-flop 164 is also set by the set signal. Therefore, the output of the flip-flop 164, that is, the PWM signal becomes high level.

Next, the down counter 163 counts down based on the PWM reference clock, and when the set count value reaches "0", a heliset signal is given to the flip-flop 164. Therefore, the output of flip-flop 164 is inverted to low level.

As a result, the duty is determined from the value held in the PWM data register 162, that is, the voltage data calculated by equation (6), and a PWM signal is derived from the PWM unit 16.

7. 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, a motor for controlling the operation of a robot, 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, even if the speed detection signal fluctuates over time due to noise etc., accurate speed can be obtained without being affected by the fluctuation. and good motor control is possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the electrical configuration of a drive control circuit for an optical system drive DC servo motor 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. 8. FIG. 4 is a diagram showing two memories M1 and M2 used for rotational speed detection processing in the embodiment of the present invention. FIG. 5 is a block diagram showing the electrical configuration of the speed command signal input section. FIG. 6 is a flowchart showing a phase difference detection processing procedure in an embodiment of the present invention. FIG. 7 shows the phase difference PHDT and the control voltage v based on the phase difference.
2 is a graph showing the relationship with 2. FIG. 8 is a block diagram showing a specific electrical configuration of the PWM unit. FIG. 9 is a timing chart showing the operation of the PWM unit. In the figure, 10...DC servo motor, 11...
Driver section, 12... rotary encoder, 13...
・Encoder signal input section, 14...control section, 15...
・Speed command signal input section, 16...PWM unit, M
1, M2...indicates memory. 9

Claims (1)

[Scope of Claims] 1. In a motor control device that performs feedback control of a motor so that the motor rotation speed becomes equal to a command speed, calculation means for calculating data regarding the motor rotation speed at each predetermined timing; It has multiple storage areas that can store data for a predetermined number of times in chronological order, and each time data related to motor rotation speed is calculated, the already stored data is shifted one by one and the data calculated this time is shifted one by one. A storage means for storing data in the latest data storage area, and a means for retrieving data corresponding to the middle of the plurality of data stored in the storage means as speed data to be used for motor control. Motor control device.