JPH0797919B2 - Driving method of step motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose] Outline Industrial field of application Conventional technology Problems to be solved by the invention Means for solving problems (FIG. 1) Action Example (a) of one embodiment Description (Figs. 2 and 3) (b) Description of operation of one embodiment (Figs. 4 and 5) (c) Description of another embodiment [Outline] [Outline] Number of excitation phases of step motor In the method of driving the step motor by alternately changing the number of times, by increasing the excitation time of the one with a larger number of excitation phases and shortening the excitation time of the one with a smaller number of excitation phases, the rise delay of the excitation current of the step motor It is intended to prevent a decrease in torque and an unstable torque balance.

[Industrial application field]

The present invention relates to a step motor driving method for exciting an N-phase step motor in a (m-1) -m phase, and more particularly to a step motor driving method in which deterioration of dynamic characteristics due to delay in rising of exciting current of the step motor is improved. .

The stepper motor changes its position stepwise by a pulsed drive signal, so basically it is possible to perform desired positioning by open loop control, and a highly efficient and inexpensive drive mechanism can be realized, which is widely used in various fields. There is.

As a driving method of this step motor, a 1-2 phase excitation method of a 2-phase step motor and a 2-3 phase of a 5-phase step motor
There is known a so-called excitation phase number switching drive, such as a phase excitation method, which excites an N-phase step motor (m-1) -m phase (m≤N). In this driving method, the one-step angle is half the one-step angle θs peculiar to the step motor.
It can be set to s / 2 and high resolution can be obtained.

Since such a stepping motor is driven by passing a current through a winding (coil), a rise in the current of the coil is delayed and the torque is reduced. In particular, when the excitation phase number switching drive is used, a change in torque balance is brought about, and its solution has been desired.

[Conventional technology]

The excitation phase number switching drive method of the step motor is, for example, 2
Referring to FIG. 6 by taking 1-2 phase excitation of the phase stepping motor as an example, the switching transistors TR1 to TR4 of the exciting circuit 2 are respectively provided for the windings A and B of the stepping motor 1 shown in FIG. Are connected, the transistors TR1 to TR4 are turned on / off by the phase excitation signals A and B shown in FIG. 6 (B), and currents are passed through the windings A and B. In the example in the figure, 1 phase (phase) → 2 phases (+ A phase) → 1 phase (A phase)
It is driven in that order.

Such a step motor is shown by an equivalent circuit of an inductance L and a resistance R as shown in FIG. 7 (A), and the exciting current i flowing in the winding is And the time constant T becomes L / R.

Therefore, the excitation current waveform from the time when the transistor corresponding to the winding is turned on is as shown in FIG. 7 (B), and there is a delay in rising of the current for the time T or longer. For this reason, the chopper control is performed with reference to ic in FIG. 7 (B) so that the maximum current is suppressed to ic and the delay time is suppressed to about T, but the rise delay of the minimum T time cannot be prevented.

Such a delay in the rise of the current causes a decrease in torque and deterioration of the high-speed response frequency.

As a method of improving the rise time, it is sufficient to reduce the time constant T. Therefore, a method of connecting a resistor r in series to the motor winding and setting T = L / (r + R) has been conventionally used.

The current i of the motor at this time is Becomes

[Problems to be solved by the invention]

However, in the conventional technique, according to the equation (2),
Exciting current decreases. Therefore, in order to obtain the exciting current of the formula (1), a method of increasing the drive voltage Vo is adopted, but the resistance r, that is, r / (R + r) is dissipated as heat, and energy efficiency is increased. However, since there is a limit to increasing the driving voltage, it cannot be expected that the time constant will be improved so much.

Particularly, in the excitation phase number switching driving method such as 1-2 phase excitation, as shown in FIG. 7 (C), the rising delay of the excitation current of the newly excited phase is increased during the two-phase excitation after the one-phase excitation. As a result, the time during which two-phase excitation is performed becomes substantially extremely short.

For example, even if the phase 1-phase excitation is switched from the phase 1-phase excitation to the phase A 2-phase excitation at time t ₁ in FIG. 7C, and the phase A excitation is performed between the times t ₁ and t _2. Two-phase excitation is not sufficiently performed due to the delay in the rising of the current.

Therefore, due to the delay in the rise of the current, the torque at the time of two-phase excitation is extremely reduced, the torque balance between the one-phase excitation and the two-phase excitation is lost, speed unevenness and torque fluctuation occur, and high-precision rotation is difficult. In addition to the problem, there is also a problem that the maximum response frequency cannot be raised because it causes step-out.

In order to solve this, for example, JP-A-60-20797 proposes a 1-2 phase excitation method in which the two-phase excitation time is lengthened and the one-phase excitation time is shortened. ing.

In this proposal, in order to lengthen the two-phase excitation time and shorten the one-phase excitation time, the delay circuit is operated according to the excitation phase and the clock interval is lengthened only when the two-phase excitation is performed. There is.

However, in this proposal, in the step feed, the phase excitation time can be controlled by the control with and without delay, but in the case of acceleration / deceleration control, it is necessary to change the time interval according to the speed. There was a problem that could not be realized.

Therefore, it is an object of the present invention to provide a method of driving a step motor that can vary the excitation time according to the number of excitation phases even in acceleration / deceleration control.

[Means for solving problems]

FIG. 1 is a diagram for explaining the principle of the present invention, and shows 1-2 phase excitation as an example.

In the present invention, the width of the excitation time (two-phase excitation time in the figure) of the one with a large number of excitation phases (m-phase excitation) is set to (T + ΔT), which is longer than the conventional T, while the one with a smaller number of excitation phases (m -1) The excitation time (one-phase excitation time in the figure) width of the phase excitation is set to (T-ΔT), which is shorter than the conventional T, and the excitation phase number switching drive is performed.

That is, according to the present invention, the number of excitation phases of the step motor is alternately changed to drive the step motor, and the excitation time of the one having a larger number of excitation phases is lengthened and the excitation time of the one having a smaller number of excitation phases is increased. In the step motor driving method for driving by shortening, the memory stores the excitation time of the one with the larger number of excitation phases and the excitation time of the smaller number of the excitation phases according to a predetermined acceleration / deceleration characteristic. Every time, the processor alternately reads the excitation time of the one with the larger number of excitation phases and the excitation time with the smaller number of the excitation phases, and switches the number of excitation phases of the step motor each time the excitation time elapses. It is characterized by performing control.

[Action]

In the present invention, since the m-phase excitation time for the one with a larger number of excitation phases is longer, the total amount of (current value × time) during m-phase excitation increases as shown by the shaded area in FIG. Therefore, it is possible to prevent a decrease in torque during m-phase excitation due to a delay in the rising of the exciting current due to restrictions of the motor and the drive circuit, and stabilize the torque balance between the m-phase excitation and the (m-1) -phase excitation,
Prevents speed fluctuations and torque fluctuations, and enables highly accurate rotation and improvement of maximum response frequency.

Moreover, since the excitation time of the (m-1) phase is shortened,
The total operating time-the number of pulses (the amount of advance) does not change.

Further, in order to make the excitation time required for the acceleration / deceleration control variable, the excitation time for each excitation phase number according to the acceleration / deceleration control is stored in the memory, and this time is read to control the switching of the excitation phase number. I have to.

〔Example〕

 (A) Description of an Embodiment FIG. 2 is a configuration diagram of an embodiment for the present invention.

In FIG. 2 (A), the same components as those shown in FIG. 6 (A) are represented by the same symbols, and 3 is a processor (hereinafter, MP).
U)), which is composed of a microprocessor and executes the functions of the distribution circuit and the input control circuit of the step motor 1 by a program for the processing flow shown in FIG. 4 and FIG. Reference numeral 4 is a memory including a B register 3b for saving excitation phase data, an A register 3a for calculation, and an HL register 3c for address. In addition to storing a control program, it has a data area 4a for storing pulse rate data (phase excitation time data) according to the operation pattern, 5 is I / O (input / output)
It is a port and has an input port and an output port 5a. The output port 5a is composed of 8-bit D _{0 to} D ₈ , where D ₀ is a transistor TR1 of the excitation circuit 2, D ₂ is a transistor TR2, and D ₄ is a transistor TR2. to but transistor TR3, which D ₆ is connected to the transistor TR4, 6a denotes a data bus, MPU 3 and the memory 4, I /
6b is an address bus for exchanging data with the O port 5, and is for exchanging addresses with the MPU 3, the memory 4, and the I / O port 5.

It should be noted that d ₁ , d ₂ , d ₃ and d ₄ are diodes, respectively, which are connected in parallel to the windings (excitation coils) A and B of the step motor 1 to suppress spikes.

FIG. 2 (B) is an explanatory diagram of switching the number of excitation phases, and shows the relationship between 8-bit excitation phase data and the phases excited by this.

That is exciting phase data MPU3 is 8 bits "00000111", which when set to the output port 5a of the I / O port 5, D _0, since D ₂ is "1" transistors TR1, TR2 is When turned on, two-phase excitation of A phase and B phase is performed. Then MP
When U3 is shifted to the excitation phase data to the left of 1 bits Figure, the excitation phase data "00001110", and when it is set in the output port 5a of the I / O port 5, D ₂ is "1", The transistor TR2 is turned on, and one-phase excitation of only the B phase is performed. Similarly, every time the excitation phase data is left-shifted, the excitation phase is switched from 1 phase → 2 phases → 1 phase.

Therefore, the MPU 3 shifts the excitation phase data by 1 bit at each time determined by the pulse rate data of the memory 4, and the I / O
If it is set to the output port 5a of the port 5, the distribution operation, that is, the 1-2 phase excitation switching can be executed.

FIG. 3 is an explanatory diagram of an operation pattern of one embodiment of the present invention.

The operation pattern of the step motor should be divided into sections of the operation pattern, or linear acceleration / deceleration or exponential acceleration / deceleration should be performed collectively according to the measurement or calculation results of the frequency-torque characteristics of the step motor and the Masatsu load of the drive system. However, the acceleration / deceleration start-up and fall times or the number of steps are set as conditions.

For example, the operation pattern shown in FIG. 3 (A) shows a pattern of accelerating, moving to a constant speed, and decelerating after holding the position,
Acceleration / deceleration is linear acceleration / deceleration and is performed at the same time.

Then, the pulse rate data (phase excitation time data) T _{0 to} Tn are determined by the above calculation and the
T ₀ , acceleration / deceleration is determined to be T ₁ , T ₂ , T ₃ , T ₄ ... And constant speed is determined to be Tn.

In the present invention, the correction time ΔT is added to the pulse rate data thus determined for two-phase excitation,
For phase excitation, the correction time ΔT is subtracted to create the correction pulse rate data, and the operation pattern, number of steps,
It can be obtained under the intended conditions such as the total time.

This correction time ΔT can be obtained as an appropriate value by solving an operation equation such as phase plane analysis or Laplace transform, or may be obtained by experiment.

FIG. 3 (B) shows the pulse rate data obtained corresponding to FIG. 3 (A). In this example, the pulse rate data and the discrimination code are paired, and even-numbered addresses Y and Y +
A discrimination code is stored in 2 ... and odd addresses Y + 1, Y
The pulse rate data is stored in +3 ....

The discrimination code indicates distinction between stop, slewing, (acceleration / deceleration), and constant speed for the pulse rate data, where “0” (actually, 8-bit “00000000”) indicates slewing, and “1” and “2”. "(Actually 8-bit data) is constant speed, of which" 1 "is constant speed of 1-phase excitation," 2 "is constant speed of 2-phase excitation, and" 3 "(actually 8-bit data) is stopped. Shows.

For example, in the data area 4a of the memory 4, the address Y indicates the stop and hold of "3", the time T ₀ of the address Y + 1 is stored, and Y + 2, Y + 4, ..., Y + (2n-2)
"0" indicating slewing at the address is Y
+3, Y + 5, ..., Phase excitation time T ₁ at Y + 2n- ₁
+ ΔT, T ₂ −ΔT, ..., Tn−1 + ΔT are stored, and Y
+ 2n, Y + 2n + 2 indicates constant speed "1", "2"
However, accordingly, the phase excitation times Tn-ΔT and Tn + ΔT are stored in the addresses Y + 2n + 1 and Y + 2n + 3. Here, ΔT is subtracted where the one-phase excitation is applied, and ΔT is added where the two-phase excitation is applied.

Therefore, the MPU 3 can read out the data area 4a from the address Y in order to distinguish between holding, accelerating, and constant speed and obtain the phase excitation time, and the excitation phase data described above can be obtained according to the phase excitation time. Shift and set. If the data area 4a is read in the reverse direction, constant speed, deceleration,
Can be held stopped.

(B) Description of Operation of One Embodiment FIGS. 4 and 5 are flow charts of the operation processing of one embodiment of the present invention, showing the processing of the MPU 3.

First, when MPU3 has a start interrupt,
Predetermined phase excitation data in the A register 3a (here,
"00001110", B phase (indicating phase hold) is set, and the phase excitation data of the A register 3a is given to the output port 5a via the data bus 6a. As a result, as described above (see FIG. 2 (B)), the B phase is excited and the B phase is held.

Next, the MPU 3 saves the phase excitation data of the A register 3a in the B register 3b, and further sets the initial address which is the head of the data area 4a in the HL register 3c.

Next, MPU3 adds "1" to the address of HL register 3c,
The data area 4a of the memory 4 is accessed by the address of the HL register 3c, the contents of the address are read out via the data bus 6a, and set in the A register 3a. This address is an odd address, and therefore pulse rate data (phase excitation time) is set in the A register 3a.

The MPU3 subtracts "1" from the content (phase excitation time) of the A register 3a, checks whether the content of the A register 3a is zero, and if it is not zero, subtracts "1" from the content of the A register 3a again. Repeat this.

That is, the timer functions as if the read phase excitation time has elapsed.

Next, the MPU 3 performs the excitation phase switching process when the content of the A register 3a is zero, that is, when the read phase excitation time has elapsed.

That is, the phase excitation data saved in the B register 3 is transferred to the A register 3a, and the phase excitation data of the A register 3a is shifted to the left by 1 bit and the A register 3a is shifted as described in FIG. 2B. Apply phase excitation data to output port 5a. This switches the excitation phase.

Next, the MPU 3 saves the phase excitation data of the A register 3a in the B register 3b, increments the address of the HL register 3c by one step, and accesses the data area 4a of the memory 4 as an even address.

Therefore, the discrimination code is read from the data area 4a via the data bus 6a and set in the A register 3a.

The MPU 3 judges the discrimination code of the A register 3a, and if the discrimination code is not "1" (constant speed instruction), returns to the step.

In this way, 1 phase hold for T ₀ time, 2 phase excitation for (T ₁ + ΔT) time, 1 phase excitation for (T ₂ −ΔT), and so on.
After holding the position, the step motor 1 is accelerated and driven by 1-2 phase excitation.

Then, in the MPU3, the address of the HL register 3c becomes Y + 2n, the content "1" at the address Y + 2n of the data area 4a is read, and the MPU3 sets the read data in the A register 3a.
When it is determined that the content of "1" (constant speed instruction), the acceleration step escapes and the constant speed step is entered.

First, the MPU 3 advances the address of the HL register 3c by one.

As a result, the address of the HL register 3c becomes Y + 2n + 1, and the phase excitation time data of constant speed one-phase excitation can be read.

The MPU3 accesses the data area 4a of the memory 4 with the address of the HL register 3c, reads the content of the address, that is, the excitation time data (Tn-ΔT) of the constant-speed one-phase excitation, and A
Set in register 3a.

The MPU3 subtracts "1" from the content (phase excitation time) of the A register 3a, checks whether the content of the A register 3a is zero, and if it is not zero, subtracts "1" from the content of the A register 3a again. Repeat this.

That is, like the above, it functions as a timer for whether the read excitation time (Tn-ΔT) has elapsed.

Next, the MPU 3 performs the excitation phase switching process when the content of the A register 3a is zero, that is, when the phase excitation time of the read constant speed one-phase excitation elapses.

That is, the phase excitation data saved in the B register 3b is transferred to the A register 3a, and the phase excitation data of the A register 3a is shifted to the left by 1 bit and shifted in the A register 3a as described in FIG. 2B. Apply phase excitation data to output port 5a. This switches the excitation phase to two-phase excitation.

Next, the MPU 3 saves the phase excitation data of the A register 3a in the B register 3b.

The MPU3 checks via the data bus whether or not a stop instruction has arrived at the input port of the I / O port 5. If a stop instruction has arrived, the MPU3 finishes the constant-speed step and enters the deceleration step. Go to the step shown in FIG.

On the other hand, if it is determined that the stop instruction has not arrived, MP
U3 performs constant speed two-phase excitation processing.

That is, MPU3 adds "2" to the contents of HL register 3c, and
Set to + 2n + 3, and use the address contents of HL register 3c for memory 4
The data area 4a is accessed to read the address contents, that is, the phase excitation time data (Tn + ΔT) of the constant speed two-phase excitation and set it in the A register 3a.

The MPU3 subtracts "1" from the content of the A register 3a (phase excitation time), checks whether the content of the A register 3a is zero, and if it is not zero, subtracts "1" from the content of the A register 3a again. , Repeat this.

That is, similar to the above, it functions as a timer for whether the read excitation time (Tn + ΔT) has elapsed.

Next, when the content of the A register 3a is zero, that is, when the read phase excitation time (Tn + ΔT) has elapsed, the MPU 3 performs the excitation phase switching process.

That is, the phase excitation data saved in the B register 3b is transferred to the A register 3a, and the phase excitation data of the A register 3a is shifted to the left by 1 bit and shifted in the A register 3a as described in FIG. 2B. Apply phase excitation data to output port 5a. As a result, the excitation phase is switched to the one-phase excitation.

Next, the MPU 3 saves the phase excitation data in the A register 3a in the B register 3b, subtracts “2” from the address in the HL register 3c, and sets it as Y + 2n + 1, that is, the phase excitation time data storage address for constant speed one-phase excitation. , Go back to the step.

In this way, constant-speed 1-2 phase excitation (Tn- △
Repeat T) time, (Tn + △ T) time, MPU3 in steps
If it is determined that the stop instruction is received, the deceleration step is started.

First, the MPU 3 subtracts "3" from the address content of the HL register 3c. For example, since the address is set to Y + 2n + 1 in step, the content of the HL register 3c becomes Y + 2n-2 (even address).

Next, the MPU 3 accesses the data area 4a of the memory 4 with the address of the HL register 3c, reads the content of the address (discrimination code) via the data bus 6a, and sets it in the A register 3a.

The MPU 3 judges the discrimination code set in the A register 3a, checks whether it is "3" (stop), and if it is stopped, shifts to the one-phase holding step.

On the other hand, MPU3, if the contents of A register 3a is not "3",
Next, MPU3 adds "1" to the address of HL register 3c,
The data area 4a of the memory 4 is accessed by the address of the register 3c, the content of the address is read out via the data bus 6a, and set in the A register 3a. This address is an odd address, and therefore pulse rate data (phase excitation time) will be set.

The MPU3 subtracts "1" from the contents of the A register 3a, then checks whether the contents of the A register 3a is zero, and if not zero, again subtracts the contents of the A register 3a by "1" and repeats this. .

The MPU 3 repeats subtracting "1" from the content of the A register 3a, and when determining that the content of the A register 3a has become zero, the excitation phase switching processing is started.

That is, the phase excitation data saved in the B register 3b is transferred to the A register 3a, and the phase excitation data of the A register 3a is shifted to the left by 1 bit and shifted in the A register 3a as described in FIG. 2B. Apply phase excitation data to output port 5a.

This switches the excitation phase and returns to the beginning of the step.

Therefore, data is transferred in the opposite direction of acceleration, such as 2-phase excitation for (Tn-1 + ΔT) time of address Y + 2n-1 and 1-phase excitation for (Tn-2-ΔT) time of address Y + 2n-3. The contents of area 4a are read, the speed is reduced, and the address Y is reached.

At the step, the content of HL register 3c becomes Y and A
When the discrimination code "3" is set in the register 3a, the MPU3
This moves to the stop holding step.

First, MPU3 adds "1" to address Y of HL register 3c
The data area 4a of the memory 4 is accessed with the address of the HL register 3c, the content of the address is read out via the data bus 6a, and set in the A register 3a. This address is (Y + 1), and the one-phase holding time T ₀ is set in the A register 3a.

MPU3 subtracts "1" from the contents of A register 3a, A register 3a
When the content of the A register 3a becomes zero, that is, when the time T _{0 has} elapsed, the driving process of the step motor 1 is terminated and the process returns to the main routine.

After that, since the content of the output port 5a does not change, the step motor 1 continues to hold one phase.

In this way, the pulse rate data (phase excitation time data) determined according to the operation pattern of the step motor 1 is corrected with the correction time ΔT, and the two-phase excitation time is made longer than the above-determined time and the one-phase excitation time is increased. Is shortened to prevent the torque from decreasing during two-phase excitation and stabilize the torque balance.

Further, in this embodiment, since the acceleration / deceleration is performed with the same characteristic, the acceleration / deceleration can be executed with the same pulse rate table.

(C) Description of Other Embodiments In the above embodiments, the phase excitation time is corrected for acceleration, constant speed, and deceleration, but only during acceleration / deceleration and deceleration, depending on the load and required characteristics. This may be done only during acceleration, only during deceleration, or only during constant speed. For example, if it is performed only during acceleration, the torque shortage during acceleration will be eliminated and the torque balance will be stable, so high-speed and stable acceleration can be achieved, and if only during deceleration, the deceleration torque shortage will be solved even for large loads. In addition, since the torque balance is stable, high-speed and stable deceleration can be performed, and the stop position accuracy is improved.

Further, if it is performed at a constant speed, constant-speed feeding with stable torque balance becomes possible, and high-precision constant-speed feeding with little speed unevenness can be performed.

Next, in the above-mentioned embodiment, the same pulse rate table is used for acceleration and deceleration, but another table may be provided, and in this case, the acceleration characteristic and the deceleration characteristic can be changed. . Similarly, the correction time ΔT does not have to be the same for acceleration, constant speed, and deceleration, and may be changed for acceleration, constant speed, and deceleration depending on the characteristics of the step motor, required characteristics, and the like. At any time, it may be changed in the acceleration stage and the deceleration stage.

Further, it is not necessary to carry out the correction with the correction time ΔT every time, and it may be carried out, for example, once every other time, or may be carried out at the place where the torque shortage is supposed to be most depending on the operation pattern. Good.

Further, the 1-2 phase excitation of the 2-phase step motor has been described, but it can be applied to the (m-1) -m phase excitation of the N-phase step motor such as the 2-3 phase excitation of the 5-phase step motor. It may be used for quarter-step driving capable of half the step angle of -2 phase excitation. Similarly, the step motor drive is described as unipolar drive, but well-known bipolar drive may be used, and the timer function is provided by the MPU3, but a timer may be provided separately. It can also be applied to motors.

Although the present invention has been described with reference to the embodiments, the present invention can be variously modified according to the gist of the present invention, and these modifications are not excluded from the present invention.

〔The invention's effect〕

As described above, the present invention has the following effects.

Add the correction time to each excitation time for acceleration / deceleration and m
Since the phase excitation time is used and the correction time is subtracted to obtain the (m-1) phase excitation time, there is no speed unevenness in the acceleration / deceleration control, and highly accurate feed can be performed.

Further, since the maximum response frequency can be improved, high speed acceleration / deceleration driving can be performed.

Since the correction time is the same for acceleration and deceleration, one acceleration curve can be used to accelerate by reading in one direction and decelerate by reading in the opposite direction, and the capacity of the table of excitation time for acceleration / deceleration can be reduced, and the processor Processing is also simple.

[Brief description of drawings]

FIG. 1 is an explanatory view of the principle of the present invention, FIG. 2 is a configuration diagram of an embodiment for the present invention, FIG. 3 is an operation pattern explanatory diagram of an embodiment of the present invention, and FIGS. FIG. 6 and FIG. 7 are explanatory views of a conventional technique, which are operation flow charts of an embodiment of the invention. In the figure, 1 ... Step motor, 2 ... Excitation circuit, 3 ... Processor, 4 ... Memory, 5 ... I / O port.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuhiro Takashimizu 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Mitsunori Hiraishi, No. 35, Saho, Kato-gun, Hyogo Prefecture In-house (56) Reference JP 60-20797 (JP, A) JP 60-200798 (JP, A) JP 60-32597 (JP, A) JP 61-203898 (JP, A) ) JP-A-59-204496 (JP, A)

Claims (1)

[Claims] 1. The number of excitation phases of a step motor is alternately changed to drive the step motor, and the excitation time of the one having a larger number of excitation phases is lengthened and the excitation time of the one having a smaller number of excitation phases is set. In the step motor driving method of driving by shortening, in the excitation time determined according to a predetermined acceleration / deceleration characteristic, the excitation time of the larger excitation phase number obtained by adding the correction time and the excitation phase obtained by subtracting the correction time. The excitation time of the smaller number and the excitation time of the one having the larger number of excitation phases in one direction from the memory and the excitation time having the smaller number of the excitation phases are stored in the memory in advance. And are read alternately, for deceleration,
In the opposite direction from the memory, the excitation time of the one with the larger number of excitation phases and the excitation time with the smaller number of the excitation phases are alternately read, and the number of excitation phases of the step motor is switched every time each excitation time elapses. A stepping motor driving method characterized by performing control.