JPH06336943A - Step motor controller - Google Patents

Abstract

PURPOSE:To eliminate the occurrence of resonance due to swell vibration in a throttle valve by providing a speed keeping means for keeping a specific speed for a given time while extending an acceleration/deceleration cycle time when a specific condition is discriminated. CONSTITUTION:A step motor control device 17 has a sampling program 24 sampling a set objective value, varied following time elapse, even fixed time, and a step motor acceleration/deceleration program 25 acceleration/deceleration- cycle-controlling a step motor according to a difference between a sampling valve and the present position of the step motor. Also the device 17 has a resonance discrimination program 27 discriminating whether an acceleration/ deceleration time is conformed with a resonance period corresponding to the characteristic frequency of the driving system of the step motor or not, and moreover, a speed keeping program 28 extending the acceleration/deceleration cycle time to keep a specific speed for a given time. Consequently the occurrence of resonance due to swell vibration is eliminated in a throttle valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a step motor control device for rapidly accelerating and decelerating a step motor to a target stop position that changes when the target stop position of the step motor changes momentarily. The present invention relates to a step motor control device in which vibration generated by repeated acceleration and deceleration of a step motor is reduced.

[0002]

2. Description of the Related Art In recent years, a method of electronically controlling a throttle valve of an automobile engine by a step motor has been implemented, and a step motor control device for controlling driving and stopping of the step motor is widely used in automobiles. . Here, since it is necessary to control the opening / closing amount of the throttle valve by following the depression amount of the accelerator,
The step motor control device measures the amount of depression of the accelerator as analog data with a potentiometer or the like, samples the measured value of the potentiometer at a constant interval, A / D-converts the target value, and sets the step motor according to the target value. By controlling the stop position, the opening / closing amount of the throttle valve is controlled.

Controlling the stop position of the step motor in order to control the opening / closing amount of the throttle valve differs from a normal step motor control device in the following points. That is, the amount of depression of the accelerator changes from moment to moment depending on the operating state of the vehicle, and control of the opening / closing amount of the throttle valve with respect to the amount of depression of the accelerator also requires prompt responsiveness. However, a normal step motor control device does not change the target stop position within a short time, so the step motor is driven according to a preset speed pattern to the target stop position of the step motor, and the accuracy is improved. The focus was on stopping often.

With a growing demand for electronically controlling the amount of depression of the accelerator by using a step motor, a method of controlling the step motor used for opening and closing the throttle valve is disclosed in, for example, Japanese Patent Laid-Open No. 61-1388.
Japanese Patent No. 55 discloses a method of comparing the target value instructed by the accelerator with the current value of the step motor and controlling the rotation speed of the step motor according to the table stored in the storage means when the values differ. There is.

[0005]

However, the conventional step motor control device has the following problems. (1) The step motor control device samples a potentiometer that measures the amount of depression of the accelerator at regular sampling times to bring the step motor close to the sampled target value, and when the target value becomes constant, the step motor is switched on. It is controlled to stop. And
In order to quickly rotate the step motor to the target value,
Control is usually performed in which an acceleration / deceleration cycle is performed in which acceleration is rapidly performed at the start of rotation and deceleration is performed when the target value is approached. Repeated acceleration / deceleration cycles of the step motor generate swell vibrations in the drive system of the step motor including the throttle valve, and the position of the throttle valve becomes unstable. There was a problem that could not correspond to the amount of accelerator depression.

FIG. 6 shows a specific example of the case where vibration is generated by the step motor. In the figure, M indicates the change of the target value obtained by measuring the accelerator depression amount as analog data with a potentiometer, sampling it for a fixed sampling time A, and performing A / D conversion. Here, the sampling time A is generally about 6 msec (hereinafter referred to as ms) because the CPU in charge of the main control of the automobile controls various devices at the same time. P indicates the current step of the step motor. Also MS
PD indicates the condition of the drive pulse given to the step motor, and is specifically given as the drive frequency and the excitation time. Here, the drive frequency given to the step motor and its excitation time are given from the difference between the current position of the step motor and the target value, for example, using a table as shown in FIG.

That is, when M changes, the step motor is sequentially accelerated to MSPD = 1, 2 in the direction of eliminating the difference MA between the current position of the step motor and the target value. Then, when the current position of the step motor approaches the target value, the step motor is moved to the MSP in order to reduce the vibration at the time of stop.
The speed is gradually reduced to D = 2,1. The time of this series of acceleration / deceleration cycles is a total of B = 6.858 ms because the excitation time of MSPD = 1 is 2.000 ms and the excitation time of MSPD = 2 is 1.429 ms according to the table of FIG. When the opening degree of the throttle valve controlled by the step motor controller is measured, as shown in S,
Swell vibration is generated periodically. And because the throttle valve position becomes unstable due to the swelling vibration of the throttle valve, the intake amount of the engine becomes unstable,
There was a problem that the speed of the car could not correspond to the amount of accelerator depression. Further, when the swell vibration of the step motor becomes large, a step-out phenomenon occurs in which the step motor does not follow the command pulse, and there is a risk that the speed of the vehicle cannot follow the accelerator pedal depression amount.

(2) Further, when the step motor is driven immediately after it is stopped, even if the step motor controller stops the step motor, the drive system of the step motor is vibrating, so that the drive after the stop is stopped. There was a problem that the behavior of the throttle valve in became unstable for a while, and the vehicle speed did not follow the accelerator pedal depression amount. In order to avoid this, in the conventional step motor control device, for example, when the step motor is driven by being reversed, the time until the vibration converges after the throttle valve is once stopped at the target stop position, at least 20 to. Three
It was necessary to keep the throttle valve stopped for about 0 ms. Therefore, when the amount of depression of the accelerator changes, there is a problem that a delay occurs by that amount.

The present invention has been made in order to solve the above problems, and provides a step motor control device in which undulation vibration is less likely to occur even when the step motor is periodically accelerated / decelerated. With the goal.

[0010]

In order to achieve this object, a stepping motor control apparatus of the present invention includes a sampling means for sampling a set target value which changes with the passage of time at a constant sampling time, and a sampling means. The step of calculating the difference between the set target value and the current step motor position, accelerating the step motor according to the difference, decelerating the step motor when approaching the set target value, and stopping the step motor at the set target value A step motor control device having a step motor acceleration / deceleration means for performing a motor acceleration / deceleration cycle, wherein it is determined whether or not the acceleration / deceleration cycle time matches a cycle corresponding to a natural frequency of a drive system driven by the step motor. The resonance occurrence determining means and the resonance occurrence determining means determine that the acceleration / deceleration cycle time matches the cycle. When a predetermined time by extending the acceleration and deceleration cycle time, and a speed holding means for holding the speed constant.

In the step motor control device of the present invention, since the natural frequency of the drive system of the step motor for driving the throttle valve is 150 to 180 Hz, the cycle corresponding to 139 to 192 Hz multiplied by the safety factor. The caution period for occurrence of resonance is 5.2 to 7.2 ms. Therefore, the acceleration / deceleration cycle time is 5.2 to 7.2 m.
If it matches s, then repeat the final velocity step again.

[0012]

The step motor of the present invention having such a structure drives the throttle valve of the engine through the drive system. Here, the natural frequency of the drive system of the step motor including the throttle valve and the step motor is 15
It has been confirmed by experiments that the frequency is in the range of 0 to 180 Hz. Further, the sampling means of the step motor control device samples a set target value from the potentiometer, which measures the amount of depression of the accelerator, which changes with the passage of time, at a constant sampling time. Further, the step motor acceleration / deceleration means calculates the difference between the sampled set target value and the current position of the step motor, accelerates the step motor according to the difference, and sets the current position of the step motor to the set target value. When approaching, the step motor is decelerated and the step motor acceleration / deceleration cycle is performed to stop the step motor at the set target value.

Here, the acceleration / deceleration cycle time depends on the natural frequency of the drive system driven by the step motor, which is 150 to 180H.
When the cycle coincides with the cycle of 5.2 to 7.2 ms corresponding to 139 to 192 Hz obtained by multiplying z by the safety factor, the final step is repeated and the speed is kept constant for a predetermined time. Since the sampling is not repeated at the cycle corresponding to the natural frequency of the motor system, resonance due to swell vibration does not occur in the throttle valve, the throttle valve can be accurately controlled, and the intake air amount to the engine Can be controlled accurately. Also, when the step motor is stopped, the swell vibration of the throttle valve is small, so the vibration at the time of stop can be converged in an extremely short time. Can respond.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the step motor control device 17 according to the first embodiment. An intake pipe 13 for inhaling a mixed gas of gasoline and air is connected to an automobile gasoline engine 11. A throttle valve 12 for adjusting the amount of mixed gas supplied to the gasoline engine 11 is held in the intake pipe 13 so as to be rotatable about a throttle shaft 14 with respect to the intake pipe 13. The throttle shaft 14 is connected to the output shaft of the step motor 15 via a reduction mechanism. The step motor 15 is connected to the step motor drive circuit 18 of the step motor controller 17. Drive circuit 18
Is connected to the CPU 19, which is an arithmetic unit. CPU
A RAM 2 for temporarily storing data etc. in 19
3. A ROM 22 storing a control program and the like is connected.

The ROM 22 has a sampling program 24 for sampling the accelerator data measured by the potentiometer 16 at a constant sampling time T.
Is remembered. In addition, the ROM 22 calculates the difference between the sampled value and the current position of the step motor, accelerates the step motor 15 via the drive circuit 18 according to the difference, and the step motor 15 approaches the sampled value. A step motor acceleration / deceleration program 25 for decelerating the step motor 15 and stopping the step motor 15 at a sampling value is stored.

Further, the ROM 22 counts the acceleration / deceleration cycle time B and determines whether or not the acceleration / deceleration cycle time coincides with the cycle corresponding to the natural frequency of the drive system driven by the step motor 15. A resonance determination program 27, which is generation determination means, is stored. Also, the ROM 22
In the case where the resonance determination program 27 determines that the acceleration / deceleration cycle time B matches the cycle corresponding to the natural frequency, a speed hold for holding the speed constant for a predetermined time after the acceleration / deceleration cycle time has elapsed. A program 28 is stored. Further, the CPU 19 has a potentiometer 16
Accelerator data, which is analog data measured by
An A / D converter 20 for D conversion is connected. The A / D converter 20 has an input interface 2
It is connected via 1 to a potentiometer 16 for measuring the depression amount of the accelerator 26.

Next, the operation of the step motor control device 17 having the above configuration will be described. When the driver operates the accelerator 26, the potentiometer 16 measures the amount of movement of the accelerator 26 as linear analog data. The CPU 19 fetches the analog data of the potentiometer 16 from the input interface 21 at a constant sampling time T by the sampling program 24, A / D-converts it by the A / D converter 20, and RAM 23 as the sampled target value.
Remember. Here, in this embodiment, the sampling time is T = 6 ms, as in the conventional case.

FIG. 2 shows a diagram for explaining the control state of the step motor. In FIG. 2, TSTEP indicates the measurement value of the potentiometer 16 at the sampling time T = 6 m.
A value obtained by A / D conversion for each s, that is, a target step position at which the step motor 15 that drives the throttle valve 12 should be stopped is shown. STEP indicates the current step position of the step motor 15. Also MSP
D indicates the condition of the drive pulse given to the step motor, and specifically, as shown in FIG. 5, it is given as the drive frequency and the excitation time.

A method of accelerating and decelerating the step motor 15 will be described. FIG. 3 is a flowchart showing the operation of the step motor acceleration / deceleration program 25, the resonance determination program 27, and the speed holding program 28 of the step motor control device 17. This flowchart is started by a timer interrupt at the timing when the step motor 15 completes one step operation by the main program. Target step T
Toward STEP, the current step STEP of the step motor 15 is updated by one step (S1). Next, the difference between the target step TSTEP and the step STEP that the step motor 15 currently has is calculated, and the absolute value is set as the step difference DSTEP (S2).

Next, the step difference DSTEP is compared with the drive pulse MSPD, and if DSTEP> MSPD is not satisfied (S3, NO), the process proceeds to S4. Next, DSTEP =
If it is not MSPD (S4, NO), the determination is made and the process proceeds to S5. At this time, DSTEP <MSPD, and in order to decelerate the step motor 15, the value of MSPD is decremented by 1 (S5), the flag FACC indicating the acceleration state is set to 0, and the fact that the acceleration state is not stored is stored in the RAM 23. (S
6) Go to S13. If DSPD = MSPD, the step motor 15 is set to the constant speed state,
Proceed to S13 without changing D (S4, YES).

On the other hand, the step difference DSTEP is compared with the drive pulse MSPD. If DSTEP> MSPD (S3, YES), the process proceeds to S7 to accelerate the step motor 15. Then, the flag FACC indicating the acceleration state =
If it is not 1, it is determined that there is no acceleration condition so far and a new acceleration start request is made, and the process proceeds to S8 (S7, N
O). Further, when FACC = 1, the acceleration has been in progress since the previous time, so the process directly proceeds to S11 (S7, YES). Next, when an acceleration start request is made, it is checked whether or not the time CACC from the time when the previous acceleration request is made matches the cycle corresponding to the natural frequency of the drive system of the step motor 15. That is, when CACC is equal to or smaller than the lower limit value LVL1 of the cycle corresponding to the natural frequency, it is determined that the acceleration / deceleration cycle performed this time is different from the cycle corresponding to the natural frequency, and the process proceeds to S10. (S8, YE
S). In this embodiment, LVL1 = 5.2 ms.

When CACC is not smaller than LVL1 (S8, NO), the acceleration / deceleration cycle performed this time may match the cycle corresponding to the natural frequency. The upper limit value LVL2 of the cycle corresponding to the natural frequency is compared (S9). CACC is LVL
When it is equal to or larger than 2, it is determined that the acceleration / deceleration cycle performed this time is different from the cycle corresponding to the natural frequency, and the process proceeds to S10 (S9, YES). On the other hand, CAC
When C is smaller than LVL2, it is determined that the acceleration / deceleration cycle performed this time matches the cycle corresponding to the natural frequency, and the process proceeds to S13 (S9, NO).

In S10, in order to determine that the acceleration is permitted and to accumulate the elapsed time from the start of the current acceleration,
Clear CACC to 0. Next, 1 is added to MSPD (S11). Next, set the acceleration state flag FACC to 1
Then, the acceleration state is stored (S12), and the process proceeds to S13. Next, in FIG. 5, the excitation time corresponding to the MSPD is stored in the RAM 23 as STIME (S1).
3). Next, add STIME to CACC, RAM
It is stored in 23 (S14). As a result, the CACC counts the acceleration / deceleration cycle time.

Next, in the present embodiment, since the 4-phase step motor is controlled by the 1-2 phase excitation, the pattern shown in FIG. 4 is obtained from the lower 3 bits of the current step STEP of the step motor. The step motor 15 is excited for the drive frequency and the excitation time shown in 5 (S15). Next, the interrupt time is set after STIME (S16). Then, after the interruption time has elapsed, the process proceeds to S1 again.

Next, the above flow chart will be described with reference to a concrete example. At the position of step ST1 in FIG. 2, if that step is used as a reference, STEP = 0
By updating the step, STEP becomes 1 (S
1). Next, since TSTEP = 5 and STEP = 1, DSTEP = 4 (S2). And MSPD
= 0 and DSTEP = 4, DSTEP> MSPD
Next (S3, YES), the process proceeds to S7. In S7,
Since the previous step was not in the acceleration state, the acceleration state flag FACC = 0 (S7, NO), and the process proceeds to S8.
Here, CACC = 0 and the lower limit value LVL1 = 5.2 m
Since it is smaller than s (S8, YES), it is determined that acceleration is newly permitted, and CACC is set to 0 in S10.
Then, preparation is made to start a new CACC calculation (S10). Next, MSPD is increased from 0 to 1 (S11). Then, since the acceleration state is entered, a flag FACC indicating the acceleration state is set (S12).

Next, the excitation time of 2.000 ms corresponding to MSPD = 1 shown in FIG. 5 is read and stored as STIME (S13). Next, set CACC = 0 to STIME
= 2.000 ms, CACC = 2.000 m
s (S14). Next, the drive frequency 50 shown in FIG.
A drive pulse of 0 pps is applied to the step motor 15 via the drive circuit 18 from the lower 3 bits of the step in a predetermined excitation pattern shown in FIG. 4 (S15). Next, the next interrupt time is set to STIME (S16). As a result, the drive pulse is given for the time STIME = 2.000 ms. Then, the current position step STEP of the step motor becomes ST2.

In the case of ST2, DSTEP = 5-2 = 4
(S2), since MSPD = 1 (S3, YES),
Proceed to S7. Then, since FACC = 1 (S7,
(YES), the process proceeds to S11. Next, the MSPD is increased to 2 (S11), and then the excitation time 1.429 ms corresponding to MSPD = 2 shown in FIG. 5 is read out and stored as STIME (S13). Next, CACC = 2.000m
STIME = 1.429 ms is added to s, and CACC
= 3.429 ms (S14). Next, MSPD =
Since it is 2, a drive pulse having a drive frequency of 700 pps is given according to FIG. 5 (S15). Next, the next interrupt time is set to STIME (S16). This allows
The drive pulse is applied for a time of STIME = 1.429 ms. Then, the current position step STEP of the step motor becomes ST3.

In the case of ST3, DSTEP = 5-3 = 2
(S2), since MSPD = 2 (S3, YES; S
4, YES), and proceeds to S13. Next, the MSP shown in FIG.
An excitation time of 1.429 ms corresponding to D = 2 is read out and stored as STIME (S13). Next, CACC
= 3.429 ms and STIME = 1.429 are added to set CACC = 4.858 ms (S14). Next, since MSPD = 2, drive frequency 7
A drive pulse of 00 pps is given (S15). Next, STIME is set as the next interrupt time (S1
6). As a result, the drive pulse is applied for a time of STIME = 1.429 ms. Then, the current position step STEP of the step motor becomes ST4.

In the case of ST4, DSTEP = 5-4 = 1
(S2), since MSPD = 2 (S3, NO; S
4, NO), the MSPD is decelerated to 1 (S5), and the acceleration state flag FACC is set to 0 (S6). Next, the excitation time 2.000 ms corresponding to MSPD = 1 shown in FIG. 5 is read out and stored as STIME (S13). next,
CACC = 4.858 ms and STIME = 2.000 m
s is added to set CACC = 6.858 ms (S1
4). Next, since MSPD = 1, a drive pulse having a drive frequency of 500 pps is given according to FIG. 5 (S15).
Next, STIME is set as the next interrupt time (S16). As a result, STIME = 2.000m
The drive pulse is applied for a time of s. Then, the current position step STEP of the step motor becomes ST5.

In the case of ST5, DSTEP = 9-5 = 4
(S2), since MSPD = 1 (S3, YES),
Proceed to S7. Lower limit value LVL at CACC = 6.858 ms
1 is not smaller than 5.2 ms (S8, NO), and is not larger than the upper limit value LVL2 = 7.2 ms (S9, N).
0), go to S13. Next, the excitation time 2.000 ms corresponding to MSPD = 1 shown in FIG.
It is stored as E (S13). Next, CACC = 6.8
Add STIME = 2.000 ms to 58 ms, and add C
The ACC is set to 8.858 ms (S14). Next, MS
Since PD = 1, the drive frequency is 500 pp according to FIG.
A drive pulse of s is given (S15). Next, STIME is set as the next interrupt time (S16). As a result, the drive pulse is given for the time STIME = 2.000 ms. Then, the current position step STEP of the step motor becomes ST6.

In the step motor controller of this embodiment,
The acceleration / deceleration cycle time B = 6.858 ms corresponds to the natural frequency of the drive system of the step motor 15, and the resonance period is 5.
The resonance determination program 27 determines that resonance will occur when the values match with each other for 2 to 7.2 ms, and the speed holding program 2
8, the final step is repeated, so that the acceleration / deceleration cycle time B1 = 8.858 ms does not match the resonance cycle, so that it is possible to prevent the swell vibration generated by the repetition of the acceleration / deceleration cycle.

In the case of STEP6, DSTEP = 9-6 =
3 (S2) and MSPD = 1 (S3, Y
ES), and proceed to S7. Next, FACC = 0 and (S
7, NO), the process proceeds to S8. Here, CACC = 8.85
Since it is 8 ms and is larger than the upper limit value LVL2 = 7.2 ms (S9, YES), it is determined that acceleration is newly permitted, CACC is set to 0 in S10, and calculation of a new CACC is started. (S10). Next, MSPD is accelerated from 1 to 2 (S11). Since the acceleration state is entered, the flag FA indicating the acceleration state is displayed.
Set CC (S12).

Next, the excitation time of 1.429 ms corresponding to MSPD = 2 shown in FIG. 5 is read out and stored as STIME (S13). Next, set CACC = 0 to STIME
= 1.429ms is added, CACC = 1.429m
s (S14). Next, the drive frequency 70 shown in FIG.
A drive pulse of 0 pps is applied to the step motor 15 via the drive circuit 18 from the lower 3 bits of the step in a predetermined excitation pattern shown in FIG. 4 (S15). Next, the next interrupt time is set to STIME (S16). As a result, the drive pulse is applied for a time of STIME = 1.429 ms. Then, the current position step STEP of the step motor becomes ST7.

As described in detail above, according to the step motor controller 17 of the present embodiment, in STEP 5, the acceleration / deceleration cycle time B = 6.858 ms is the cycle corresponding to the natural frequency of the drive system of the step motor. When it is determined that the acceleration / deceleration cycle time is extended by a predetermined time, the acceleration / deceleration cycle time B1 = 8.858 ms of the step motor 15 coincides with the cycle corresponding to the natural frequency of the step motor drive system. Since the resonance due to the swell vibration does not occur in the throttle valve 12, the throttle valve 12 can be accurately controlled,
The amount of intake air to the gasoline engine 11 can be accurately controlled. Also, when the step motor 15 is stopped, the swell vibration of the throttle valve 12 is small,
Since the vibration at the time of stop can also be converged in an extremely short time, it is possible to promptly respond when the depression amount of the accelerator 26 changes again.

Although the present invention has been described with reference to some embodiments, the present invention is not limited to the above embodiments, and various modifications and improvements can be made without departing from the spirit of the present invention. This can be easily guessed.
In the present embodiment, only the period corresponding to the natural frequency of the drive system of the step motor that drives the throttle valve has been taken into consideration, but it is also possible to include integer multiples and fractional multiples of the natural frequency. Further, in the present embodiment, the control device for the step motor that drives the throttle valve has been described. However, when the target value changes from moment to moment, and when the step motor is required to have high responsiveness, it can be used in other applications. Applicable.

[0036]

As is apparent from the above description, according to the step motor control device of the present invention, when the acceleration / deceleration cycle time matches the resonance period corresponding to the natural frequency of the drive system of the step motor. When the resonance occurs in the resonance determination means, the speed holding means extends the acceleration / deceleration cycle time and repeats the final step.
Since the acceleration / deceleration cycle time does not match the resonance cycle, resonance due to swell vibration does not occur in the throttle valve, the throttle valve can be accurately controlled, and the intake air amount to the engine can be accurately controlled. . Also, when the step motor is stopped, the swell vibration of the throttle valve is small, so the vibration at the time of stop can be converged in an extremely short time. Can respond.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing a control state of a step motor controlled by the step motor control device.

FIG. 3 is a flowchart showing an operation of the step motor control device.

FIG. 4 is a data diagram showing an excitation pattern of a step motor.

FIG. 5 is a data diagram showing drive pulses for acceleration / deceleration of a step motor.

FIG. 6 is an explanatory diagram showing a control state of a step motor controlled by a conventional step motor control device.

[Explanation of symbols]

 12 Throttle valve 15 Step motor 16 Potentiometer 17 Step motor control device 18 Drive circuit 19 CPU 20 A / D converter 24 Sampling program 25 Step motor acceleration / deceleration program 27 Resonance determination program 28 Speed holding program B Acceleration / deceleration cycle time

Claims (2)

[Claims] 1. A sampling means for sampling a set target value, which changes with the passage of time, at fixed sampling times, and a difference between the sampled set target value and the current position of the step motor is calculated, and the difference is calculated. Step motor acceleration / deceleration means for performing a step motor acceleration / deceleration cycle for accelerating the step motor according to the above, decelerating the step motor when approaching the set target value, and stopping the step motor at the set target value In the acceleration / deceleration cycle, the acceleration / deceleration cycle time determines whether or not the resonance generation determination means determines whether or not the acceleration / deceleration cycle time matches a cycle corresponding to the natural frequency of the drive system driven by the step motor. When it is determined that the time matches the cycle, the acceleration / deceleration cycle time is extended to a predetermined time A stepping motor control device having a speed holding means for holding the degree constant. 2. The step motor control device according to claim 1, wherein the cycle corresponding to the natural frequency of the drive system of the step motor is 5.2 to 7.2 ms.