JPH03173384A - Step-out preventive device in rotating speed controller for motor - Google Patents

Abstract

PURPOSE:To prevent the step-out condition of a motor by a method wherein a step-out preventing device is provided with a judging means, judging whether a phase difference between a speed commanding signal and a speed detecting signal has exceeded a step-out judging range or not, a monitoring means and a motor stopping signal outputting means. CONSTITUTION:The rotation pulse of a rotary encoder 12 is given to an encoder signal inputting unit 13 while a detection output is given to a control unit 14. The control unit 14 controls a motor 10 based on a speed difference and a phase difference, obtained through the operating process of a speed difference between a commanding speed and an actual rotating speed and the operating process of a phase difference between a speed commanding signal and a speed detection signal, so that the rotating speed coincides with the commanding speed. The absolute value of the phase difference is judged whether it is smaller than a step-out judging value or not and the servomotor 10 is stopped forcibly when the absolute value of the phase difference is larger than the step-out judging value and the contents of a step-out judging counter has exceeded a step-out judging time.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a step-out prevention device in a motor control device, and particularly to a step-out prevention device in a motor rotation speed control device that controls the rotation speed of a motor using a PWM signal. It is related to the device.

<Background of the Invention> Some motor rotational speed control devices are designed to control using a PWM (pulse width modulation) signal.

Such a rotational speed control device is employed, for example, in a DC servo motor control device for driving an optical system in a document reading device such as a copying machine.

In a servo motor control device for driving an optical system, in particular, even if the motor load fluctuates due to changes in frictional resistance as the optical system moves, the servo motor can be kept at a constant speed with good followability, and the optical system must be moved at a constant speed.

Conventionally, the servo motor was kept at a constant speed? Therefore, proportional control has been performed in which a PWM signal is obtained using a voltage proportional to the speed difference between the target speed and the actual detected speed.

However, in conventional proportional control, the acceleration when increasing the motor speed from the actual detected speed to the target speed changes depending on the size of the target speed, and the larger the target speed, the smaller the acceleration, and the longer it takes to reach the target speed. It gets longer,
There was a drawback that followability was not good.

Let me explain more specifically.

The equation of motion when voltage V is applied to the motor is generally expressed by the following equation.

RaGD2. Fallen L+xEa.

375KT dt -V-Ra(Io+TBt,/Kv) -(1)
becomes.

However, Ra: amateur resistance [Ω] KT torque constant [kgm/A] KE: induced voltage constant [V/rpm] lo: no-load current [A] GD2: moment of inertia due to load and motor [kgi
2] T, , : sliding load [kga] n: rotational speed [rpm].

Solving this for n, if n = N p at t-0, then KE Also, d n 375 KT dt RaGD” KE.

From this formula, when the sampling speed is N, the voltage V
By substituting NP-N and t-0, the acceleration a during the time when the target speed is
1 If the difference is ΔN, the acceleration a when ΔN-K (No -N) is applied to V- by normal proportional control is expressed as V = K ΔN, N - No )
It is obtained by substituting into the following equation.

375KTKF knee- (N-ΔN)1 375KTKE RaGD2 X ((K/KE +.1) ΔN-"No.

... (4) Ra(1 o'+'Ts"t, / It))
・KE... (5) From this 2'', even if ΔN is the same value, the target speed N.

If N. is large, acceleration i is small, and N. It can be seen that if is small, a becomes large.

Therefore, the applicant has proposed a method in which the speed difference between the commanded speed (target speed) and the actual detected speed is determined, the phase difference between the commanded speed and the detected speed is determined, and the speed control based on the speed difference is corrected using the phase difference. We have developed a device that can control motors with good followability.

<Problems to be Solved by the Invention> By the way, for example, a DC servo motor for driving an optical system in a document reading device of a copying machine drives an illumination device, a mirror, etc. in order to read a document.

The motor and the lighting device and the motor and the mirror are connected by a power transmission mechanism including, for example, a rod, a wire, and the like. Load fluctuations occur in the motor due to changes in the surface condition of the rod in these power transmission mechanisms, the state of lubricating oil supplied to the rod, the direction in which the wire is pulled, and changes in temperature and humidity.

According to the motor rotational speed control device developed by the applicant, when this kind of load fluctuation occurs, the phase difference between the command speed and the detected speed is detected, and the speed control signal is corrected based on the phase difference component. , the motor rotation speed can quickly follow the command speed.

However, even when the speed control signal is corrected based on the detected phase difference component, if the phase difference between the subsequent climbing command speed and the detected speed continues, the detected speed will be lower than the command speed. This results in a so-called speed drift state in which the speed gradually deviates.

If this speed drift state continues for a certain period of time or more, step-out occurs. If step-out occurs, normal copying will not be possible, and for example, characters will be copied in a state where they are stretched or compressed.

When speed drift conditions such as those described above occur, typically
There is often some kind of abnormality in the power transmission mechanism of the optical system.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a step-out prevention device for a motor rotational speed control device that can detect an abnormality before a step-out occurs, stop the motor, and prevent the motor from falling out of step. With the goal.

Means for Solving the Problems> The present invention provides feedback control of the motor so that the rotation speed of the motor is equal to the command speed based on the speed difference and phase difference between a speed command signal and a speed detection signal. A step-out prevention device in a rotational speed control device,
At each predetermined timing, a determining means determines whether the phase difference between the speed command signal and the speed detection signal exceeds a predetermined range for determining step-out; If it is determined that the phase difference has exceeded the step-out determination range, the monitoring means monitors whether the state in which the phase difference exceeds the step-out determination range continues for a predetermined step-out determination time; The present invention is characterized by comprising a stop signal output means for outputting a motor stop signal when it is recognized that the state exceeding the step-out determination range continues for the step-out determination period.

Effect> At each predetermined timing, it is determined whether the phase difference between the speed command signal and the speed detection signal exceeds a predetermined step-out determination range.

When it is determined that the phase difference exceeds the range for determining step-out, it is monitored whether the state in which the phase difference exceeds the range for determining step-out continues for a predetermined period of time for determining step-out. .

Then, when it is recognized that the state in which the phase difference exceeds the step-out determination range continues for the step-out determination time, a motor stop signal is output, and the motor is stopped.

<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 drive 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 a configuration example of a drive control circuit for a DC servo motor for driving an optical system of a copying machine. This control circuit uses PWM (pulse width III) as the applied voltage to the DC servo motor.
The circuit uses latlon) signals.

This DC servo motor 10 is of a permanent magnet field type, and is rotationally driven by a driver section 11.
Move 7.

A rotary encoder 12 is attached to the rotating shaft of the servo motor 10.
are connected. As already known, the rotary encoder 12 outputs a rotation pulse every time the servo motor 10 rotates by a predetermined minute angle. The rotary encoder 12 of this embodiment has one servo motor 10.
By rotating, for example, 200 rotation pulses are output.

Further, the rotation pulses of the rotary encoder 12 include at least an A-phase rotation pulse and a B-phase rotation pulse, and both rotation pulses have an equal number (for example, 200 per rotation of the motor) and are out of phase with each other. The pulses are shifted by 90 degrees.

The rotation pulse output from the rotary encoder 12 is
The signal is applied to the encoder signal input section 13.

The encoder signal input section 13 is a circuit for detecting the rotation of the servo motor 10 based on rotation pulses given from the rotary encoder 12, as will be described in detail later. The detection output of the encoder signal input section 13 is the control section 1.
given to 4.

The control unit 14 is the center that controls the entire circuit,
Speed difference calculation processing that calculates the difference between the command speed and the detected actual rotational speed of the motor; Phase difference calculation processing that calculates the phase difference between the speed command signal and the speed detection signal; and Control processing for controlling the motor 10 so that the motor rotation speed becomes equal to the command speed, step-out prevention processing for preventing the motor from stepping out due to motor load fluctuations, etc. are performed.

The control unit 14 includes a memory and a timer used for control operations to be described later.

The control unit 14 is also given an operation command signal and a command speed. The command speed is determined by a speed command clock from a control section (not shown) of the main body of the copying machine.
The signal is applied to the control section 14, subjected to signal processing, and then sent to the control section 14. The details will be described later.

The control section 14 executes arithmetic processing based on each of these input signals, 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 is a unit for changing the pulse width (output duty) of a PWM signal based on the applied PWM data. The rotational speed of the servo motor 10 is controlled by a PWM signal output from the PWM unit 16. Further, the driver unit drive signal determines the rotation direction of the servo motor 10 and performs braking.

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

Therefore, in this drive control circuit, the configuration of the encoder signal input section 13 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 FIG. 2, encoder signal input section 1
3 includes an edge detection circuit 131 to which an A-phase rotation pulse (which serves as a speed detection pulse) outputted from the low reencoder 12 is applied. The edge detection circuit 131 detects the rising edge of the applied rotation pulse, that is, the speed detection pulse, and derives its detection output.

The encoder signal input unit 13 also includes a free running counter 133 of, for example, 16 bits, which counts up the applied reference clock, and a capture register 134.

The capture register 134 uses the edge detection output of the edge detection circuit 131 as a capture signal, and uses the capture signal as a trigger to read and hold the count number of the free running counter 133.

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 if the circuit is composed of a microcomputer, a machine clock is used.

Furthermore, if there is no such reference clock, 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 unit 135 determines the level of the B-phase rotation pulse when the A-phase edge detection output is given, and depending on whether the B-phase rotation pulse is at a high level or a low level, the servo motor 10 (see FIG. ) is used to determine whether the rotation is normal or reverse. The up/down counter 136 counts up or down the detection output of the edge detection circuit 131 based on the determination 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 by the speed detection pulse. In addition, the up/down counter 136 has the number of edge detection signals,
In other words, the number of speed detection pulses is counted.

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 can be calculated as follows (6).

Here, the frequency of the reference clock is f [Hz], the number of A-phase rotation pulses output from the rotary encoder 12 when the servo motor 10 rotates once is C [pprl, and the capture register 13 at the current sample timing.
CPT, the contents of 4.

Capture register 13 at the previous sample timing
Let the contents of 4 be CPT, , .

By the way, in equation (6), since the reference clock frequency f and the number of rotational pulses C are constants, N--1Δ...(
7) A CPT, -CPT, lX However, A:LX60X: CPT, -CPTfi-1.

FIG. 3 shows that the control unit 14 samples the contents of the capture register 134 and the up/down counter 136 at a sampling time Δ.
It is a flowchart showing the control operation for calculating the rotation speed N by reading every t.

Note that the sampling time Δt is Δt≧CPTfi−CPTfi, (8
) is set at an appropriate time.

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

Each time the internal timer reaches a certain sampling time Δt (step S1), the control unit 14 resets the timer (step S2), and reads the contents of the capture register 134 and the up/down counter 136 (step S3).
).

Then, after subtracting the count number CPT of the capture register 134 read last time stored in the memory from the read count number CPT of the capture register 134, the reference clock number X within one sample time Δ is obtained. CPT, is stored in memory (step S4).

Also, from the read count number UDC of the up/down counter 136, the count number UDC of the up/down counter 136 read last time stored in the memory
After subtracting -1 to find the number of rotational pulses within one sample time Δ, UDC is stored in the memory (step S5
).

Then, based on the above equation (6), the servo motor 1
0 rotation speed N is determined (step S6).

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

FIG. 4 is a block diagram showing a specific example of the configuration of the speed command signal input section 15. As shown in FIG. The speed command signal human power section 15 includes:
It includes an edge detection circuit 151 for detecting, for example, a rising edge of the speed command clock, a free running counter 152, a capture register 153, and an up counter 154.

The free running counter 152 is, for example, a 16-bit counter that counts up the applied reference clock. This free running counter 152
may be used in common with the free running counter 133 of the encoder signal input section 13 described above.

The capture register 153 uses the edge detection output of the edge detection circuit 151 as a capture signal, and uses the capture signal as a trigger to read and hold the count number of the free running counter 152.

The up counter 154 is for counting up the output pulses of the edge detection circuit 151.

The operation of this circuit is as follows.

A speed command clock outputted from the apparatus main body side, for example, a control side microcombiner of the copying machine main body, is applied to an edge detection circuit 151, and a rising edge is detected. Since the output of the 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,
Capture register 15 based on a certain edge detection signal
3, read the contents of the capture register 153 based on the next edge detection signal, and find the difference between them, thereby making it possible to measure the count number of the free running counter 152 in one cycle of the speed command clock. In other words, target rotation speed data (command speed data) 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, and reads the contents of the capture register 153 and the up counter 154.
Find the difference between the count number read this time and the count number read last time in , and divide it by the difference between the count number read this time and the count number read last time in the 7-step counter. We are trying to find a more accurate reference clock number.

Then, the speed difference ΔN between the command speed and the detected rotation speed N of the motor 10 is determined.

FIG. 5 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 edge detection circuit 13 of the encoder signal input section 13
When the rising edge of the speed detection pulse is detected by 1, (
In 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, phase reference value PP1. is calculated and stored according to the following equation (step 513).

PP 1. =PP I(II-1) +SPD
(9) Here, P P I (@-1): Previously stored phase reference value SPD: Number of reference clocks SPD during one period of the speed command clock (SPD is a fixed value).

However, since the initial value of P P r(, -11 is zero, the corresponding phase reference value PP1. The value of is SPD.

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

SPD Then, the above processing is repeated. That is, each time the rising edge of the speed detection signal is detected (step 511),
Reading the count value of the free running counter 133 and the phase comparison value PDT.

(step 512), phase reference value PPI.

(step 813) and the phase difference P
The HDT calculation (step 514) is repeated.

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 PP1. calculated in step 313. 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 S13
The value of , 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 PP1.) 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 is calculated as the speed command clock. Value according to the period of (SPD)
The phase difference PHDT is obtained by dividing by . Therefore, even if the phase difference between the speed command clock and the speed detection pulse is one period or more of the speed command clock,
The phase difference PHDT is accurately detected.

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

The voltage VO that should be output to the servo motor 10 in order to make the rotational speed of the servo motor 10 follow the command speed is calculated by the following formula, %, where the control voltage due to the speed difference ΔN is 1, and the correction voltage due to the phase difference PHDT is V2. % (11) The correction voltage V2 based on the phase difference PHDT is obtained as follows, assuming that the predetermined maximum value of the correction voltage V2 is α.

(a) When the phase difference is smaller than one cycle (-1<PHDT<+1) V2-αφPHDT ... (12) (
b) When the phase difference is one cycle or more and the speed detection pulse is ahead of the speed command clock (PHDT≦-1) V2--α ... (13) (C
) When the phase difference is one cycle or more and the speed detection pulse is behind the speed command clock (PHDT≧+1) V2-+α ... (14)
Therefore, the relationship between the phase difference PHDT and the correction voltage v2 is as follows:
The result is as shown in FIG.

The control voltage V1 due to the speed difference ΔN is calculated using the following formula (15) Ra: Amateur resistance [Ω KT torque constant [kg 1m/^] KE: Induced voltage constant [V/rpm] IO = No load Current [, A] GD2: Moment of inertia due to load and motor [kg
m2] TsL: sliding load [kgm].

The control unit 14 detects the rotational speed of the servo motor 10 (step S6 in FIG. 3), calculates the speed difference ΔN from the command speed, or calculates the phase difference PHDT (step 514 in FIG. 5). For each, the above formula (11) ~ (1
5) Calculate VO based on 2, 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. 7 is a block diagram showing a specific example of the configuration of the PWM unit 16, and FIG. 8 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 an RS flip-flop 164.

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 (1
This is voltage data obtained by 1). That is,
This is the voltage vO obtained by correcting the voltage V1 in equation (15) with the correction 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 each 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 (11), and a PWM signal is derived from the PWM unit 16.

FIG. 9 shows a step-out prevention processing procedure performed by the control section 14.

This process is performed every time the phase difference PHDT between the speed command clock and the speed detection pulse is detected in the phase difference detection process. That is, the detection timing is the same as the detection timing of the phase difference PHDT, and is performed every time Δt.

When the phase difference PHDT is detected, the absolute value I of the phase difference
It is determined whether PHDT l is smaller than the step-out determination value Y (step 521). The step-out determination value Y is determined in advance through experiments and the like, and is set to "1" in this embodiment. Therefore, in this step S21, it is determined whether the absolute value IPHDTI of the phase difference is smaller than "1".

The absolute value of phase difference I PHDT I is the step-out determination value Y (-1
) In the above case (NO in step S21), the contents K of the step-out determination counter are incremented by "1" (step 522), and the contents K of the step-out determination counter correspond to the step-out determination time T. It is determined whether or not the value Z exceeds the value Z (Stella 523).
is determined in advance through experiments and the like, and is determined to be "10" in this embodiment. Therefore, in step S23, it is determined whether the content K of the step-out determination counter exceeds "10".

If the content K of the step-out determination counter exceeds the value Z corresponding to the step-out determination time T, an abnormality signal is output (step 524) and this process is terminated.

Based on this abnormality signal, equipment for performing the copying operation of the copying machine, such as the servo motor 10, is forcibly stopped, and an abnormality indicator light, for example, is turned on to indicate that an abnormality has occurred in the optical system. to inform the operator. In response to this notification, the operator calls a specialist such as a service person to inspect and repair the abnormality.

If the content K of the step-out determination counter is less than or equal to the value Z corresponding to the step-out determination time T, the current process ends and the process waits until the next phase difference PHDT is calculated.

Further, in step 21 above, the absolute value of the phase difference PHDT
If l is smaller than the step-out determination value Y, the content K of the step-out determination counter is reset, that is, set to -0 (step 525), and the current process is terminated.

Since the above processing is performed every time the phase difference PHDT is calculated, it is determined that the absolute value PHDT l of the calculated phase difference is greater than or equal to the step-out determination value Y (here "1").
laZ (here rlO) corresponding to the time T for determining step-out
J) If a larger number of times (that is, on the "11th" anniversary in this case) continues, YES is determined in step S13, and an abnormality signal is output.

That is, when the state in which the absolute value I PHDT l of the phase difference is greater than or equal to the step-out determination value Y continues for a time longer than the step-out determination time T, an abnormal signal is output.

Note that after the rotational speed of the servo motor 10 reaches a drift state, the critical value at which the drift state cannot be resolved and the step-out occurs is determined in advance through experiments, and the step-out determination value Y and the step-out determination time T are determined in advance. It's decided.

Therefore, by the above processing, the copying operation is stopped before the motor 10 goes out of step, so that it is possible to prevent the characters to be copied from becoming larger or smaller when being copied.

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 detect an abnormality and stop the motor before a step-out occurs, thereby preventing the motor from falling out of step. can be prevented.

[Brief explanation of the drawing]

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 a rotational speed detection device for a DC servo motor for driving an optical system according to an embodiment of the present invention. FIG. 3 is a flowchart showing the rotational speed detection processing procedure in the embodiment of the present invention. FIG. 4 is a block diagram showing a specific example of the configuration of the speed command signal input section. FIG. 5 is a flowchart showing the phase difference detection processing procedure in the embodiment of the present invention. FIG. 6 shows the phase difference PHDT and the correction voltage V based on the phase difference.
1 is a graph showing the relationship with 1. FIG. 7 is a block diagram showing a specific electrical configuration of the PWM unit. FIG. 8 is a timing chart showing the operation of the PWM unit. FIG. 9 is a flowchart showing the step-out prevention 11-processing procedure in the embodiment of the present invention. In the figure, 10...DC servo motor, 11...Driver section, 12...Low reencoder, 13...
Encoder signal input section, 14...control section, 15...
A speed command signal human power section, 16...PWM unit is shown. 2nd figure 574- 3rd figure7th figure cause figure figure figure

Claims (1)

[Claims] 1. Speed of speed command signal and speed detection signal The motor rotation is based on the difference and phase difference. The motor is adjusted so that the rolling speed is equal to the command speed. of the motor that provides feedback control of the motor. Step-out prevention device in rotational speed control equipment And, Speed command signal at each predetermined timing The phase difference between the Check whether the specified range for detecting out of synchronization has been exceeded. Discrimination means for discriminating; The phase difference is used to detect out-of-step by the discrimination means. If it is determined that the range has been exceeded, the phase A condition in which the difference exceeds the range for detecting synchronization is a prediction. Does the specified period of time for detecting synchronization continue? monitoring means for monitoring whether or not the Also, by means of monitoring, the phase difference is out of step when it exceeds the range for determining out of step. When it is recognized that the test period has continued, Stop signal output to output motor stop signal The rotational speed control of the motor is equipped with means, A step-out prevention device for control equipment.