JP2002281787A - Speed control method of stepping motor, weaving control method in welding machine, metal body to be welded - Google Patents

Abstract

(57) [Problem] To provide a speed control method of a stepping motor capable of realizing large acceleration / deceleration without step-out. SOLUTION: a1 to a4 are integer numbers indicating the number of output pulses calculated in the previous long cycle, and b1 to b4 are integer numbers indicating the number of output pulses calculated in the present long cycle. That is, in the initial calculation, the number of pulses stored in a1 to b4 is output in this order every 2 ms. The sorting buffers c1 to c4 are buffers for rearranging the current output values b1 to b4 stored in the output pulse buffer. The output register has the function of a shift register, and outputs a number of pulses corresponding to the value in the leftmost register in the figure every 2 ms. Each time, the value of each register is shifted to the left.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control method for a stepping motor, a weaving control method in a welding machine using the stepping motor speed control method, and a metal to be welded using the weaving control method. It is about the body.

[0002]

2. Description of the Related Art In a welding machine for welding a metal body by using an arc, a welding wire is moved at a high speed in a width direction of a welding portion so that a molten metal spreads over the entire width direction of the welding portion. I have to. Such reciprocating movement of the welding wire is called weaving.

Conventionally, in order to perform such weaving, a welding torch has been driven by a servomotor. Servomotors are capable of high-speed acceleration / deceleration control, and have been considered to be optimal for use in weaving control that requires such a function.

[0004] However, the servomotor requires feedback control using an accessory device such as an encoder in order to control the position of the servomotor. There is a problem that the encoder malfunctions due to noise. In addition, since a feedback control device is required, there is a problem that the price is high.

[0005]

SUMMARY OF THE INVENTION In order to solve such a problem, the inventors have considered using a stepping motor instead of a servo motor for weaving control. Since the stepping motor does not require a sensor such as an encoder and does not perform feedback control, it has a feature of being resistant to noise and being inexpensive.

However, a commercially available stepping motor may lose synchronism when the acceleration / deceleration is increased. Also, even when operating at a constant speed, if the speed is odd with respect to the number of pulses, the number of command pulses must be changed frequently to maintain a constant speed on average, This can cause loss of synchrony.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is not necessary to frequently change the number of command pulses so as not to lose synchronism even if acceleration / deceleration is increased and to maintain a constant speed. A speed control method of a stepping motor capable of realizing a large acceleration / deceleration without step-out even in a stepping motor which is inexpensive and resistant to noise, and a weaving control in a welding machine using such a stepping motor control method. It is an object to provide a method and a metal body to be welded by such a welding machine.

[0008]

According to a first aspect of the present invention, there is provided a method of controlling a speed of a stepping motor, comprising: a first sampling cycle having a short period and a first sampling period having an integral multiple thereof. Two sampling periods are set, the command speed of the stepping motor is obtained for each first sampling period, and the number of output pulses corresponding to the command speed is calculated. The fractional pulses are sequentially accumulated in the output pulse at the next sampling time. The number of output pulses for each first sampling period is obtained, and the obtained number of output pulses is sorted in the second sampling and rearranged in the order of the number of output pulses. When moving from acceleration to constant-speed operation, or when moving from constant-speed operation to acceleration, during the second sampling period, the pulse number is smaller. A pulse corresponding to the number of output pulses is output in order of the first sampling cycle in descending order of the number of pulses. (2) When the motor shifts from deceleration to constant speed operation during deceleration, or when the motor shifts from constant speed operation to deceleration, During the two sampling periods, pulses corresponding to the number of output pulses are output in the first sampling period in ascending order from the largest pulse number to the smallest pulse number. (3) When the motor is operating at a constant speed, the second pulse is output. During the sampling period, control is performed to output pulses corresponding to the number of output pulses in each of the first sampling periods in order from the smallest pulse number to the largest pulse. The control for outputting pulses corresponding to the number of output pulses is alternately repeated for each second sampling period. A method for controlling the speed of a stepping motor, comprising: outputting the number of pulses calculated before sorting during the second sampling period when shifting to deceleration or shifting from deceleration to acceleration (claim 1). It is.

In this means, the speed pattern is basically determined for each second sampling period which is a long period, but a pulse is generated for each first sampling period which is a short period obtained by dividing the second sampling period. Output.

[0010] First, since pulses are output in a short cycle while considering changes in the speed pattern in a relatively long cycle, the speed of the stepping motor is smoothly changed. For this reason, the risk of step-out is reduced, and the acceleration / deceleration that can be stably realized can be increased accordingly.

Further, the number of output pulses for each first sampling period is sorted in the second sampling period.
And when moving from acceleration to constant speed operation during acceleration,
When shifting from constant speed operation to acceleration, during the second sampling period, pulses corresponding to the number of output pulses are output in the first sampling period in ascending order of the pulse number. In the middle, the number of output pulses monotonically increases and the motor speed does not decrease, so that step-out hardly occurs.

Similarly, when the motor shifts from deceleration to constant speed operation during deceleration, and when the motor shifts from constant speed operation to deceleration, the second
During the sampling period, pulses corresponding to the number of output pulses are output in the first sampling period in ascending order of the number of pulses, so that the number of output pulses monotonically decreases during deceleration, and the motor speed is reduced. Is no longer accelerated, so step-out is unlikely to occur.

When the motor is operating at a constant speed, control is performed such that during the second sampling cycle, pulses corresponding to the number of output pulses are output in the first sampling cycle in ascending order of the number of pulses from the smallest. And the control of outputting pulses corresponding to the number of output pulses in the first sampling cycle in the order from the largest pulse number to the smallest pulse number are alternately repeated in the second sampling cycle. In this case, the motor changes the speed only at a constant speed and acceleration or only at a constant speed and deceleration, and does not repeat acceleration and deceleration in a short cycle to adjust the fraction of the pulse. Therefore, step-out is unlikely to occur. According to this means, even if the fraction processing of the pulse is performed, the smooth operation can be performed, so that the command speed can be continuously changed.

When the motor shifts from acceleration to deceleration or from deceleration to acceleration, control is disturbed if a sorted signal is output. Therefore, during the second sampling period, the number of pulses calculated before the sorting is calculated. Is output as is.

In the above description, the acceleration, deceleration and constant speed are determined, for example, by comparing the average motor speed during the second sampling cycle with the previous sampling cycle and the current sampling cycle, and when the difference between these values is equal to or greater than a predetermined value. Is determined to be acceleration / deceleration, and if less than the predetermined value, it is determined to be constant. Also, by comparing the first output and the last output before sorting, if the latter is larger than the former by a predetermined value, it is determined that acceleration is performed, if the former is larger than the latter by a predetermined value, deceleration is performed, otherwise, it is determined that the speed is constant. Is also good.

The determination of the transition from acceleration to deceleration and from deceleration to acceleration is made, for example, as follows. That is, before sorting, the difference (absolute value) between the maximum speed at the first sampling timing during the current second sampling period and the speed at the first first sampling timing is equal to or greater than a predetermined value, and When the difference (absolute value) between the maximum speed at the first sampling timing in the cycle and the speed at the last first sampling timing is equal to or greater than a predetermined value, it is determined that the operation has shifted from acceleration to deceleration.

Similarly, before sorting, the difference (absolute value) between the minimum speed at the first sampling timing in the current second sampling cycle and the speed at the first first sampling timing is equal to or more than a predetermined value, and When the difference (absolute value) between the minimum speed at the first sampling timing in the second sampling cycle and the speed at the last first sampling timing is equal to or greater than a predetermined value,
It is determined that the mode has shifted from deceleration to acceleration.

In these determinations, there may be both a determination that the vehicle is operating at a constant speed and a determination that the vehicle is moving from acceleration to deceleration and from deceleration to acceleration. In this case, the latter is given priority. Is desirable.

A second means for solving the above-mentioned problem is:
The first means, wherein the first sampling cycle is set shorter than a rated sampling cycle (rated output cycle) of the stepping motor (Claim 2).

As described above, in the first means, the acceleration and deceleration of the stepping motor can be made smooth and unnecessary acceleration and deceleration can be eliminated. It can be shorter than the rated sampling period. Thereby, the acceleration / deceleration of the stepping motor can be made larger than the rating.

A third means for solving the above problem is as follows.
A method for controlling the speed of a stepping motor, comprising the steps of: when performing acceleration / deceleration, determining the number of output pulses by setting the speed pattern at the time of acceleration / deceleration to an S-shape. ).

When accelerating or decelerating with a stepping motor, the speed is generally ramped. However, according to this method, a large acceleration is applied to the stepping motor at the start and end of the acceleration / deceleration, and the stepping motor may lose synchronism. In this means,
Since the number of output pulses is obtained by setting the speed pattern at the time of acceleration / deceleration to an S-shape, the acceleration applied to the stepping motor can be reduced as compared with the case where acceleration / deceleration is performed in a ramp shape, and the stepping motor loses synchronism. Can be prevented. Therefore, rapid acceleration / deceleration can be performed accordingly.

A fourth means for solving the above-mentioned problem is:
This is a speed control method for a stepping motor in which the first means or the second means is combined with the third means (claim 4).

In the present means, the functions and effects of the first means or the second means and the third means are exhibited together,
The effect obtained by combining these can be obtained.

A fifth means for solving the above problem is as follows.
A weaving control method for a welding machine, comprising: using a stepping motor for weaving a torch in a welding machine; and controlling the stepping motor by any of the first to fourth means. 5).

According to this means, the weaving control of the welding torch can be performed smoothly and at high speed by using the stepping motor. Therefore, high-speed and precise weaving control can be realized by an inexpensive device which is resistant to noise. Can be.

A sixth means for solving the above-mentioned problem is:
A welded metal body welded using the fifth means (claim 6).

In this means, since welding is performed using high-speed and precise weaving control, the manufacturing cost is reduced.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following processing, it is assumed that the standard output cycle of the stepping motor is 8 ms, and the output is performed at a cycle of 2 ms by improving the standard output cycle.

FIG. 1 is a diagram showing a part of buffers and registers used for control. These buffers and registers can be realized by using a memory of a microcomputer. The output buffer register calculates and stores the number of pulses output every 2 ms (short cycle).
The current long cycle (8 ms), the integer value of the value in the previous long cycle, and its fraction are stored.

In the figure, a1 to a4 are integer values of the number of output pulses calculated in the previous long cycle, and b1 to b4 are integer numbers of the calculated output pulses in the current long cycle. That is, in the initial calculation, the number of pulses stored in a1 to b4 is output in this order every 2 ms. a'1 to b'4 are locations where fractions obtained when calculating the speed into the number of pulses are stored, and a method of processing the fraction will be described later.

The sorting buffers c1 to c4 are buffers for rearranging the current output values b1 to b4 stored in the output pulse buffer. The output register has the function of a shift register, and outputs a number of pulses corresponding to the value in the leftmost register in the figure every 2 ms. Each time, the value of each register is shifted to the left.

An example of a method of controlling a stepping motor according to an embodiment of the present invention using such buffers and registers will be described below with reference to flowcharts shown in FIGS. FIG. 2 is a flowchart showing the overall flow of control, and FIG. 3 is a flowchart showing a sorting function which is a central part of the technical idea of the present invention.

The flowchart shown in FIG. 2 is activated every short period of 2 ms. First, it is determined in S11 whether or not the timing is a long cycle timing of 8 ms. If the timing is not the long cycle timing, the process proceeds to step S16.

If it is the long cycle timing, the process proceeds to step S12, and the number of pulses to be output during the current 8 ms is calculated. That is, the number of output pulses for four times of the next 2 ms, 4 ms, and 6 ms is calculated. Here, it is assumed that the rotation number of the motor is a [rpm] when one pulse is output every 2 ms. If the speed command at a certain timing is b [rpm], the number of pulses to be output is b / a.
This value is usually not an integer.

In order to solve this problem, in the present embodiment, the following fraction processing is performed. In other words, if the calculated pulse number has a fraction, the fraction is absorbed by adding it to the calculation of the next output pulse. That is, assuming that the fraction in the previous output pulse calculation is c, the current output pulse number N and the output pulse fraction c ′ are: N = [b / a + c] (1) c ′ = b / a + c−N (2) However, [] indicates the largest integer that does not exceed the value in []. The number of output pulses calculated in this way is
The output pulse buffers are stored in b1 to b4. Then, the value of the fraction c 'is put in b'1 to b'4. afterwards,
The values of b1 to b4 in the output pulse buffer are transferred to the sort buffer, and the flow shifts to the sort processing in step S13.

In the sorting process, a process as shown in FIG. 3 is performed. First, in step S131, it is determined whether the stepping motor is accelerating. This compares the average value or integrated value of the previous output values a1 to a4 of the output pulse buffer with the average value or integrated value of the current output values b1 to b4, and the latter is a predetermined value compared to the former. If it is larger than this, it is determined that the vehicle is accelerating.
If the acceleration is being performed, the process proceeds to step S132, and the values of the sort buffer are rearranged in ascending order from the left.

Next, in step S133, it is determined whether or not the stepping motor is decelerating. This is because the average value or integrated value of the previous output values a1 to a4 of the output pulse buffer is compared with the average value or integrated value of the current output values b1 to b4, and the former is a predetermined value compared to the latter. If it is larger than the above, it is determined that the vehicle is decelerating.
If the vehicle is decelerating, the process proceeds to step S134, and the values of the sort buffer are rearranged in descending order from the left.

Next, in step S135, it is determined whether or not the stepping motor is at a constant speed. This is determined because neither the condition during acceleration nor the condition during deceleration is applied. In this case, step S1
When the process is shifted to 36 and the pulse number is rearranged in ascending order in the previous 8 ms, the pulse is rearranged in descending order, and in the previous 8 ms, the pulse number is rearranged in ascending order. That is, when the constant speed state continues, the data is rearranged alternately every 8 ms in ascending order and descending order.

Finally, 8 ms targeted in step 147
During the period, it is checked whether the speed command has switched from acceleration to deceleration or from deceleration to acceleration. Note that this check is performed before step S141, and when this condition is satisfied, sorting is not performed and step S16 is performed.
It may be made to shift to.

Whether or not this condition is satisfied is determined in the present embodiment as follows. That is, of the four pulse outputs output in 8 ms this time,
The difference between the maximum pulse number and the first output pulse number is equal to or greater than a predetermined value, and the difference between the maximum pulse number and the last output pulse number is equal to or greater than a predetermined value. If so, it is determined that the mode has shifted from acceleration to deceleration.

Also, of the four pulse outputs output in the current 8 ms, the difference between the first output pulse number and the minimum pulse number output is greater than a predetermined value, and the last output pulse number is the last output pulse number. If the difference between the number of pulses and the minimum number of pulses is equal to or greater than a predetermined value, it is determined that the mode has shifted from deceleration to acceleration.

In such a case, the pulses are not sorted, and the value transferred from the output pulse buffer to the sort buffer is left as it is in step S138. Steps S132 and S13 have already been performed.
4. If the sort has been performed in S136, the process is returned to the original state.

When the sorting process is completed as described above, the process proceeds to step S14 in FIG. 1, and the sorted result is transferred to the output registers d1 to d4. Then, in step S15, the current output values b1 to b1 of the output pulse buffer
b4, b'1 to b'4 are moved to the previous output values a1 to a4, a'1 to a'4.

Finally, in step S16, the number of pulses corresponding to the leftmost register of the output register shown in FIG. 1 is output, and the output register is shifted to the left.

4 to 7 show examples of actual speed control of the stepping motor. 4 shows an example of a constant speed operation, FIG. 5 shows an example of an acceleration operation, FIG. 6 shows an example of a deceleration operation, and FIG. 7 shows an example of a transition from an acceleration operation to a deceleration operation. In both figures,
The timing indicates ms from the start of control,
The motor speed is the number of pulses per 1 ms (kpps), the calculated number of pulses is the number of pulses to be output every 2 ms, the integer number of pulses is the number of pulses N calculated by the above equation (1), and the remaining number of pulses is This is the odd pulse number c ′ calculated by the equation (2). In any of the methods, the rated pulse output timing of the pulse motor is assumed to be every 8 ms, and a pulse is output every 2 ms obtained by dividing the pulse output timing into four.

FIG. 4 shows a case in which a constant speed operation is performed, in which the motor speed is 16.7 [kpps]. The theoretical number of calculated pulses at this time is 33.4.
At this time, the number of integer pulses and the number of remaining fraction pulses calculated by the equation (1) are as shown in the figure. In this embodiment, the number of integer pulses calculated every 8 ms is sorted. That is, the integer pulse number is arranged in ascending order from 0 to 6 ms, and the integer pulses are arranged in descending order from 8 ms to 14 ms, and this is alternately repeated every 8 ms. Of course, the integer pulses may be arranged in descending order in the first 8 ms, and the integer pulses may be arranged in descending order in the next 8 ms, and this may be alternately repeated.

In this way, the number of pulses after sorting is obtained, and this is output as an output pulse every 2 ms.
FIG. 4 shows the number of pulses before sorting and the number of pulses after sorting together. According to this, the variation of the number of output pulses, that is, the variation of the motor speed is reduced by the sorting function which is a feature of the present invention. It can be seen that step-out is less likely to occur.

FIG. 5 shows an example in which a speed command in an accelerating state is given to the stepping motor. In this case, the obtained integer number of pulses every 2 ms is sorted between 8 ms and then sorted. The number of pulses is obtained in the same manner as in the example shown in FIG. 4, but as a sorting method, the pulses are always arranged in ascending order of the number of pulses. In the case of FIG.
The integer pulse number and the sorted pulse number are the same.

FIG. 6 shows an example in which a speed command in a decelerating state is given to the stepping motor. In this case as well, the obtained integer number of pulses every 2 ms is sorted for 8 ms and then sorted. The number of pulses is obtained in the same manner as in the example shown in FIG. 4, but as a sorting method, the pulses are always arranged in descending order of the number of pulses. In the case of FIG.
The integer pulse number and the sorted pulse number are the same.

In the examples shown in FIGS. 4 to 6, the sum of the integer pulses every 2 ms in the current 8 ms cycle and the previous 8 ms
A constant speed state is determined when the sum of integer pulses every 2 ms in the cycle is less than 1, an acceleration state is determined when the former is greater than 1 and a deceleration state is determined when the latter is greater than 1 and greater than the former.

FIG. 7 shows an example of speed control when the speed command of the stepping motor shifts from acceleration to deceleration. In the first 8 ms, the motor is determined to be in an accelerating state, and sorting is performed in ascending order of the number of pulses.

In the next 8 ms, the sum of the integer pulses every 2 ms in the current 8 ms cycle is larger than the sum of the integer pulses in the previous 8 ms cycle.
Since the sum of the integer pulses per ms exceeds 1 [kpps],
It is once determined that the vehicle is in an acceleration state. However, the first output pulse number is larger than 50 [kpps], which is the maximum output pulse number in the section, and the last output pulse number is more than 50, which is the maximum output pulse number in the section. Is smaller than 2 so that it is determined that the transition period is from the acceleration state to the deceleration state, and the number of unsorted pulses is output as it is.

In the subsequent two 8 ms periods, it is determined that the vehicle is in the deceleration state, and the pulse numbers sorted in descending order of the output pulse number are output.

In the above description, sorting has been performed based on the standard output cycle of 8 ms.
For example, the sorting may be performed based on 16 ms, which is twice as long as the standard, or the sorting may be performed at a cycle irrelevant to the standard output cycle.

At the time of constant speed operation, as the reference cycle of sorting is increased, the cycle in which the speed fluctuation appears can be increased, and the step-out becomes more difficult to occur. For example, in the case of performing output in 2 ms, if sorting is performed every 32 ms, the number of speed fluctuations can be reduced to 1/4 of that in the case of performing sorting in 8 ms.

FIG. 8 shows an example of the acceleration pattern of the stepping motor. In a conventional acceleration / deceleration control of a stepping motor, as shown in FIG. 8A, acceleration (or deceleration) is performed in a ramp shape. However, in this case, as shown in FIG. 8A, a large acceleration instantaneously acts on the motor at the start and end of the acceleration, so that the motor is likely to lose synchronism. Therefore, the inclination of the ramp, that is, the acceleration cannot be made too large.

FIG. 8B shows an example of the acceleration control according to the embodiment of the present invention, in which the speed between the acceleration start point and the acceleration end point is set to the speed of the S-shaped pattern. Is controlled. Specifically, the acceleration start point A and the acceleration end point are connected by two parabolas that are point-symmetric with respect to the midpoint C between the acceleration start point A and the acceleration end point B, and the axes of these parabolas are shown in FIG. And the vertices thereof are points A,
B.

In this way, as shown in FIG. 8 (b), the acceleration increases in a ramp form from 0, reaches a maximum at the middle point C, then decreases in a ramp form and returns to 0 at the point B. Become. Therefore, since the maximum acceleration becomes smaller and smoother, the motor hardly loses synchronism. Therefore, the acceleration as a whole can be increased accordingly.

It should be noted that the pattern of the S-shaped curve is not limited to the one described above.
For example, of the acceleration time, the first ４ may be parabolic, the next ラ ン プ may be ramp-shaped, the next ４ may be parabolic again, or the first ３ may be parabolic. State, next one
A third may be a ramp shape, and the next third may be a parabolic shape again.

When the processing shown in FIGS. 1 to 7 is performed based on the acceleration / deceleration pattern determined as described above, smoother speed control is achieved, and the acceleration / deceleration of the stepping motor is reduced. Step-out is less likely to occur.

As described in the section of the prior art, weaving is performed in a welding machine to reciprocate a welding wire. The method itself of performing weaving using a motor is well known.
542 and JP-A-11-179543, the description thereof will be omitted.

In controlling these weaving,
In order to make the weaving trajectory a predetermined one, acceleration / deceleration control of the motor must be performed. In such a weaving control, a stepping motor is used as a motor, and if the stepping motor is controlled by the method of the present invention as described above, the speed change can be made smooth and rapid acceleration / deceleration can be performed. Does not lose synchronism,
Weaving speed can be increased. Therefore, weaving control can be realized with an inexpensive system without using a servomotor, and a system that is resistant to noise can be achieved because an encoder is not used.

When such a weaving control method is used, a metal body to be welded can be manufactured at low cost.

[0065]

As described above, according to the first aspect of the present invention, the speed of the stepping motor is changed smoothly. For this reason, the risk of step-out is reduced, and the acceleration / deceleration that can be stably realized can be increased accordingly.

In the invention according to claim 2, the acceleration / deceleration of the stepping motor can be made larger than the rated value. According to the third aspect of the present invention, the acceleration applied to the stepping motor can be reduced, and rapid acceleration and deceleration can be performed accordingly.

In the invention according to claim 4, claim 1 is
And the sub-invention according to claim 2 and the function and effect of the invention according to claim 3 can be obtained, and the function and effect obtained by combining these can be obtained.

According to the fifth aspect of the present invention, high-speed and precise weaving control can be realized by an inexpensive device which is resistant to noise. In the invention according to claim 6, since welding is performed using high-speed and precise weaving control, manufacturing costs are reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a part of a buffer and a register used for control.

FIG. 2 is a flowchart showing an overall flow of control.

FIG. 3 is a flowchart illustrating a sorting function.

FIG. 4 is a diagram showing an example of determining the number of pulse outputs during constant speed operation.

FIG. 5 is a diagram showing an example of determining a pulse output number during an acceleration operation.

FIG. 6 is a diagram showing an example of determining the number of pulse outputs during a deceleration operation.

FIG. 7 is a diagram illustrating an example of determining the number of pulse outputs when shifting from acceleration operation to deceleration operation.

FIG. 8 is a diagram illustrating an example of an acceleration pattern of a stepping motor.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Ikuo Mibu 3-2-2, Sachimachi, Hitachi-shi, Ibaraki Prefecture Within Hitachi Engineering Services Co., Ltd. (72) Inventor Kenichi Maeda 3-2-2, Sachimachi, Hitachi-shi, Ibaraki No. 2 F-term in Hitachi Engineering Services, Ltd. (reference) 5H580 AA03 BB10 FA13 FA24 GG04 GG08 HH39

Claims (6)

[Claims] 1. A method for controlling the speed of a stepping motor, comprising: setting a first sampling cycle of a short cycle and a second sampling cycle of an integral multiple of the first sampling cycle; When calculating the speed and obtaining the number of output pulses corresponding to the commanded speed, the fractional pulses are sequentially accumulated and added to the output pulses at the next sampling time to obtain the number of output pulses for each first sampling period. The number of output pulses obtained is sorted in the second sampling and rearranged in the order of the number of output pulses. (1) When the motor is accelerating, when moving from acceleration to constant speed operation, and when moving from constant speed operation to acceleration, During the second sampling period, the output pulse is output in the first sampling period in ascending order of the number of pulses during the second sampling period. (2) When the motor is decelerating, when shifting from deceleration to constant speed operation, and when shifting from constant speed operation to deceleration, the number of pulses is large during the second sampling period. Output pulses corresponding to the number of output pulses in the first sampling cycle in ascending order from the smallest one. (3) When the motor is operating at a constant speed, the pulses having the smaller number of pulses in the second sampling cycle are output. Control for outputting pulses corresponding to the number of output pulses in the first sampling cycle in the order of larger ones, and Control for outputting pulses corresponding to the number of output pulses in the first sampling cycle in the order of the largest number of pulses from the largest number of pulses (4) When the motor shifts from acceleration to deceleration, or when the motor shifts from deceleration to acceleration, A speed control method for a stepping motor, wherein the number of pulses calculated before sorting is output as it is during two sampling periods. 2. The speed control method for a stepping motor according to claim 1, wherein the first sampling period is:
A speed control method for a stepping motor, wherein the speed is set shorter than a rated sampling cycle (rated output cycle) of the stepping motor. 3. A method for controlling the speed of a stepping motor, wherein the speed pattern during acceleration / deceleration is determined as an S-shape during acceleration / deceleration, and the number of output pulses is obtained. Method. 4. A stepping motor speed control comprising a stepping motor speed control method according to claim 1 and a stepping motor speed control method according to claim 3. Method. 5. A stepping motor is used for weaving a torch in a welding machine, and the stepping motor is controlled by the stepping motor speed control method according to any one of claims 1 to 4. Weaving control method in a welding machine characterized by the above-mentioned. 6. A welded metal body which is welded by using the weaving control method according to claim 5.