JP2001251897A - Apparatus and mtehod for cont rol of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and a method for the control of a stepping motor in which an oscillation amplitude can be suppressed largely, even if the motor constants or a load is changed. SOLUTION: The control apparatus comprises an inverter 23, which is used to electrify respective phases (a phase A, a phase B, a phase C) of a three-phase hybrid(HB) motor 10. The apparatus comprises a control circuit 40, to which an operation command is supplied and by which a commutation signal generated by being chopped is supplied to the inverter 23. The apparatus comprises a reflux-diode continuity detection circuit 30, which detects the time when the direction of rotation in the vibration of a rotor is reversed, in such a way that change in the electrification state of a reflux diode is detected. The control circuit 40 controls the commutation of the inverter 23 at output intervals TN, TN' which are calculated on the basis of the equation of the secondary vibration system of the rotor in the stepping motor 10, and it suppresses the vibration of the rotor when the commutation is controlled.

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 and a control method for suppressing vibration of a rotor when driving a step motor in an open loop.

[0002]

2. Description of the Related Art A step motor is applicable to a control system based on open-loop control and has advantages such as the ability to position a rotor by supplying a command pulse.
In recent years, it has been used as an actuator for various control devices, but when an open-loop control system is used, it is necessary to suppress noise, vibration, and the like.

In order to suppress this vibration, Japanese Patent Laid-Open No.
As disclosed in Japanese Patent Application Laid-Open No. 308499, Japanese Patent Application Laid-Open No. 5-64495, etc., two-phase excitation and three-phase excitation are alternately performed so that the drive current value is similar to a sine wave input approximation instead of a square wave. Has been proposed.

In addition, another method has been proposed in which vibration is settled by performing non-vibration settling by a control method called positive cast control. Typical examples thereof include anti-phase excitation damping and final step delay damping. As described in the literature such as "How to use a stepping motor: Industrial Research Committee: Hideo Hyakumeki, 1993, 6,20, P126-128", reverse-phase excitation damping is performed immediately before the rotor reaches a mechanical stability point. This is a drive control method in which the motor is excited in the reverse direction to perform braking, and returns to the original excitation again near the stable point.

Further, in the final step delay damping, once the pulse application is stopped just before the target one step, the rotor overshoots and approaches the target position. Therefore, the remaining one pulse is applied at the closest point. This is a drive control method for reducing vibration at the time of stop. The timing for applying the last one pulse is determined by, for example, a timer.

[0006]

However, in the above-described positive cast control, since the drive control is performed without grasping the position of the rotor, when the motor constant or the load changes, the drive control is performed accordingly. There is an unsolved problem that the control system must be tuned, and this tuning for each product is practically impossible in view of cost increase.

The present invention has been made to solve such a conventional problem, and has as its object to suppress the vibration even when the motor constant or the load changes, and to smoothly rotate the step motor. It is an object of the present invention to provide a stepping motor control device and a control method that can be used.

[0008]

According to a first aspect of the present invention, there is provided a stepping motor control apparatus comprising: an inverter for driving a stepping motor based on a supplied commutation signal; And a control means for generating a commutation signal to be supplied to the inverter means, the control means comprising: a second-order vibration system equation based on the natural vibration angular frequency, the initial value of the position, and the initial speed. Output interval calculation means for calculating the output interval of the commutation signal based on the following, and signal output means for outputting the commutation signal at the output interval calculated by the output interval calculation means. .

According to the first aspect of the invention, the natural vibration of the step motor is approximated to a secondary vibration system, and the output interval of the commutation signal to the inverter means is calculated based on the secondary vibration system equation. By outputting the commutation signal to the inverter means at the calculated output interval, the commutation signal is output at the maximum point of the rotor speed in consideration of the natural vibration of the rotor, and the commutation which advances the step motor by one step by the inverter means. Do.

According to a second aspect of the present invention, in the stepping motor control device according to the first aspect, the output interval calculating means sets the number of driving times to n, the natural vibration angular frequency to β, and the phase angle to φ during acceleration. , T _N = (π / 2−φ
_N ) / β is calculated to calculate a pulse interval T _N.

In the invention according to claim 2, the inverter is provided.
Commutation signal to advance step motor by one step
Output interval T to output_N The natural vibration each frequency β and phase
Angle φ _N The rotor speed is calculated based on
At the point of high accuracy, the commutation signal for the next step
Output and vibration-free settling can be performed.

Further, in the step motor control device according to a third aspect, in the invention according to the second aspect, the output interval calculating means includes a storage table representing a relationship between the number of driving times n and the phase angle φ _N. It is characterized by:

According to the third aspect of the present invention, the number of driving times n
By referring to the storage table based on
_N can be calculated, without performing complicated calculations,
The phase angle φ _N can be calculated, and the output interval T _N is calculated and stored in advance as 1 / β so that the sum operation and the product operation can be easily performed only once. Can be.

According to a fourth aspect of the present invention, in the stepping motor control apparatus according to the first aspect, the pulse interval calculating means sets the number of times of driving to n when the transition from the acceleration state to the constant speed state is performed. Assuming that the vibration angular frequency is β and the pulse interval during acceleration is T _N , T _N + T _N ′ = T _N +
It is characterized in that it is configured to calculate a pulse interval T _N ′ represented by (1 / β) sin ⁻¹ (1 / 2√n).

[0015] In the invention according to the claim 4, in the transition from the acceleration state to the constant speed state, the output interval of the constant speed during the output interval T _N at the time of acceleration _{T N '= (1 / β} ) sin -1 (1 / 2√
By adding n), the output of the commutation signal is delayed so as to shift to a constant speed state without generating vibration, and thereafter the commutation signal is supplied to the inverter means at every output interval T _N 'at the constant speed. Thus, the constant speed state is maintained.

Further, in the step motor control device according to a fifth aspect, in the invention according to the fourth aspect, the pulse interval calculating means includes a driving number n and sin ^-1 (1 / 2√n).
And a storage table that represents the relationship with

In the invention according to claim 5, the number of driving times n
By referring to the storage table based on
^-1 (1 / 2√n) can be calculated, and the output interval T _N 'at the constant speed can be calculated and 1 / β is calculated and stored in advance, so that the sum operation and the product operation can be performed. The output interval T _N ′ at the time of constant speed can be easily performed only by performing each operation once.

According to a sixth aspect of the present invention, in the step motor control device according to any one of the first to fifth aspects, the signal output means is a pulse width modulation means for forming a commutation signal to be supplied to the inverter means. And controlling the acceleration by controlling the duty ratio of the pulse width modulation means.

In the invention according to the sixth aspect, the commutation signal supplied to the inverter means is pulse-modulated by the pulse width modulation means and supplied, and the duty ratio thereof is controlled so that the drive current supplied to the step motor is controlled. Can be controlled to control the acceleration at the time of acceleration.

According to a seventh aspect of the present invention, in the stepping motor control device according to any one of the first to sixth aspects, the control means includes means for measuring a natural vibration angular frequency before starting drive control. It is characterized by having measuring means.

In the present invention, the natural vibration angular frequency β is measured by the natural vibration angular frequency measuring means before the start of the drive control, so that the optimum commutation signal for each step motor is provided. Control can be performed.

Further, in the step motor control device according to claim 8, in the invention according to claim 7, the natural vibration angular frequency measuring means drives the rotor by one step from a stop state before starting drive control. It is characterized by measuring the elapsed time at this time and calculating the natural vibration angular frequency.

In the invention according to claim 8, the rotor of the step motor is driven by one step from the stop state, and the elapsed time at this time is measured to calculate the natural vibration angular frequency β. At this time, for one step of the rotor, an encoder capable of measuring the rotation direction of the rotor is used to measure the time from when the rotor starts to rotate forward to the time when the rotor starts rotating reversely, or the time from when the rotor starts to rotate backwards to when the rotor rotates forward. Is doubled, the natural vibration angular frequency β can be calculated.

Still further, according to a ninth aspect of the present invention, in the invention according to the seventh aspect, when the stepping motor is a three-phase stepping motor, the natural vibration angular frequency measuring means includes a counter electromotive force appearing in an open phase. It is characterized in that it is configured to measure a waveform to calculate a natural vibration angular frequency.

According to the ninth aspect of the present invention, when the motor is a three-phase step motor, the forward / reverse rotation of the rotor can be detected from the back electromotive force waveform appearing in the open phase, and the rotor can be detected without using an encoder. By measuring the elapsed time of the forward / reverse rotation, the natural vibration angular frequency β can be calculated.

According to a tenth aspect of the present invention, there is provided a stepping motor control method comprising: generating a commutation signal based on a drive command; and supplying the generated commutation signal to an inverter means to perform open-loop drive control of the stepping motor. In the control method, when supplying a commutation signal to the inverter means,
2 based on natural vibration angular frequency, initial position value, initial speed
It is characterized by comprising a step of calculating an output interval of the commutation signal based on the following oscillation system equation, and a step of outputting a commutation signal to the inverter means at the calculated output interval.

According to the tenth aspect, the same operation as that of the first aspect can be obtained.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes a three-phase HB (hybrid) step motor applied as a driving means for moving a carriage of a printer, for example. A three-phase alternating current is supplied from the drive circuit 20 to the Y-connected coils of the step motor 10. The drive circuit 20 includes a converter 22 for converting a commercial AC power supply 21 into a DC power supply having a predetermined voltage (for example, 30 V), and an inverter 23 connected to an output side of the converter 22 as inverter means.

Here, the inverter 23 is connected to the positive power supply line.
L_P And the negative power line L_N Two N channels in between
Field-effect transistors (hereinafter simply referred to as transistors)
S) T _{A +}And T_A-Is the transistor T_{A +}Positive drain
Power line L_P And the source is transistor T_A-Dray of
Transistor T_A-Source to the negative power line L_N
Are connected in series with each other
Transistor T_{A +}And T _A-Similarly, two N channels in parallel
Channel field effect transistor (hereinafter simply referred to as transistor
) T_{B +}And T_B-Are connected in series.
Jista T_{B +}And T _B-As well as two N channels in parallel
Field-effect transistors (hereinafter simply referred to as transistors)
S) T_{C +}And T_C-Are connected in series, and
T_{A +}And T _A-On the converter 22 side of the
Large enough to stabilize voltage changes during commutation of inverter 23
It has a configuration in which a capacitor 24 having a capacity is connected. Each
Lanista T_{A +}, T_A-, T_{B +}, T_B-And T_{C +}, T_C-No
A current flows from the source side to the drain side between the rain and the source.
Reflux diode D for reflux_{A +}, D_A-, D_{B +}, D_B-as well as
D_{C +}, D_C-Is connected.

The transistor T of the inverter 23
The connection point of _{A +} and T _A− is connected to the A-phase coil of the step motor 10, the connection point of the transistors T _{B +} and T _B− is connected to the B-phase coil of the step motor 10, and the connection of the transistors T _{C +} and T _C− The connection point is connected to the C-phase coil of the step motor 10.

On the other hand, the commutation of the inverter 23
Star T_{A +}, T_A-, T_{B +}, T_B-And T _{C +}, T_C-At the gate
For example, a control circuit including a microcomputer
A commutation pulse as a commutation signal is supplied from the path 40.
And is controlled by

An operation command is input to the control circuit 40 from an external control device, a detection signal of the freewheeling diode conduction detection circuit 30 is input to the control circuit 40, and the stepping motor 10 is controlled based on the detection signal of the freewheeling diode conduction detection circuit 30. While measuring the natural vibration angular frequency β of the rotor at
Accelerate the step motor 10 based on the operation command,
In order to control the deceleration and the stop, a commutation pulse for one step is applied to each transistor T _{A +} , T _A− , T _{B +} ,
A commutation pulse whose pulse width has been modulated by the built-in pulse width modulation circuit 41 is output to the gates of T _B−, T _{C +} , and T _C− at an output interval calculated based on the natural oscillation angular frequency β and the number of driving times n.

Here, the reflux diode conduction detection circuit 30
Fig. 2 shows a portion corresponding to one phase, for example, the phase B.
As shown in FIG.
And a change detection unit 34. comparator
The unit 31 includes a transistor Tb ₊ And transistor Tb_- When
Is connected to its own non-inverting input terminal.
In addition, a diode forward voltage (V
F) operational amplifier connected so that it is applied in the positive direction
32 and its own inverting input terminal is connected to the connection point
Also, the diode forward voltage is applied to its own non-inverting input terminal.
(VF) is connected in such a way as to be applied in the opposite direction.
And a width device 33. In practice, for example, as shown in FIG.
Comparator section 31 and conduction diode change detection
A portion 34 is provided for each phase.

According to this configuration, the freewheel diode Db ₊
There the operational amplifier 32 becomes conductive outputs a high level signal, whereas, the return diode Db _- is an operational amplifier 33 becomes conductive state and outputs a high level signal.

The conducting diode change detection unit 34, from the output signal of the operational amplifier 32 and operational amplifier 33 feedback diode Db and a reflux diode Db _{+ -} detects that a change in the conduction state of which the direction of rotor rotation Is supplied to the control circuit 40 as a detection signal at the time point when is reversed. When becomes from the nonconductive state to the conductive state, _- more specifically, conducting diode change detection unit 34, a reflux diode Db ₊ is from a conductive state to a non-conductive state, a freewheeling diode Db
Alternatively, the reflux diode Db ₊ is from the nonconductive state to the conductive state, a freewheeling diode Db _- when changes from a conductive state to a non-conductive state, so as to output a signal indicative of the detect when the rotor rotation direction is reversed It is configured.

The principle by which the freewheeling diode conduction detecting circuit 30 can detect the reversal of the rotation direction of the rotor will be described below.

FIG. 3 is a diagram illustrating the principle in which the horizontal axis represents time and the vertical axis represents an electrical angle. The position where the electrical angle is 120 ° is the target position, and the rotor stops at the current electrical angle of 0 °. It is assumed that

At time t0, when a commutation pulse is supplied to the inverter 23 so as to advance the rotor of the stepping motor 10 by one step, the rotor becomes 1 in electrical angle.
Attempts to rotate 20 °, but due to the moment of inertia of the rotor and the electromagnetic attraction / repulsion between the rotor and stator,
The rotor performs damped oscillation as shown by the solid line.

Therefore, time t1 is a time point at which the rotor is decelerated and starts reverse rotation. When the rotation direction of the rotor changes, the polarity of the back electromotive force voltage also reverses. This can be easily understood by imagining, for example, that the N magnetic pole approaches the open-phase coil, but the N magnetic pole moves away due to the reverse rotation of the rotor.

The polarity of the back electromotive force voltage is detected by repeating P-side chopping and N-side chopping, and detecting a change in the conduction state of the freewheeling diode with respect to the open phase. The reason will be described below.

Now, the three-phase HB step motor 1 shown in FIG.
The terminal voltages of the A phase, B phase, and C phase of 0 are represented by Va, Vb,
Vc, and the back electromotive force of each of the A phase, the B phase, and the C phase is e
a, eb, and ec.

FIG. 4 shows a chopping sequence in the case where the open phase is the B phase. In the case where the N-side chopping and the P-side chopping are alternately performed, the transistor on / off control state and the inverter operation (inverter operation) are shown. ), The conducting diode and the polarity of the back electromotive force voltage eb are described in association with each other.

[0044] Now, as an example, in FIG. 1, the transistors Tc ₊ and the transistor Ta _- and is in the on state, state (P side chopping) which performs pulse width modulation control transistor Tc ₊ is changed from the ON state to the OFF state Is assumed. At this time, the terminal voltage Vb of the open phase is “Vb = e
b + (VSD−VF) / 2− (ea + ec) / 2: where VSD is the voltage between the source and drain of the transistor,
VF is the forward voltage of the diode.

Here, the back electromotive force voltage of each phase is 1
A position where the polarity of eb changes, that is, eb = 0, because it has three-phase symmetric voltage waveforms having phases different by 20 degrees.
In terms of an ea = -ec, freewheeling diode Db _- condition to conduct because "Vb <-VF", "eb <-
When the P-side chopping if the (VSD + VF) / 2 ", the return diode Db _- conducts.

[0046] Similarly for N-side chopping, the transistors Tc ₊ and the transistor Ta _- and is on, by performing a pulse width modulation control transistor Ta _- in the state in which has changed from the ON state to the OFF state, the return diode Db
_The condition for ₊ conduction is “eb> (VSD + VF) / 2”. Therefore, by repeating the P-side chopping and the N-side chopping, it is possible to detect the polarity of the back electromotive force by detecting which of the reflux diodes conducts, and thus it is possible to detect the time t1.

FIG. 5 schematically illustrates this state. In the N-side chopping, “eb> (VSD + VF)
/ 2 ”, the return diode Db ₊ conducts, and in the P-side chopping,“ eb> − (VS
D + VF) / 2 "
b _- is turned on.

As described above, when the polarity of the open-phase back electromotive force voltage is positive, when the N-side chopping is performed, the P-side (+
Side) and the polarity of the open-phase back electromotive force voltage is negative, and when P-side chopping is performed, the N-side (−) reflux diode becomes conductive.
While repeating side chopping and P side chopping,
If the time when the conduction state of the diode changes is detected, t1
Can be detected.

As an example of the detection at the time t1, detection of the conduction state of the freewheeling diode has been described. However, other methods, for example, by comparing the voltage of the open phase with the midpoint voltage, etc. It goes without saying that the polarity of the back electromotive force voltage may be determined. However, according to the above-described detection method, when the conduction state of one return diode and the other return diode provided for each phase has changed, the point in time when the rotation direction of the rotor is reversed is detected. The detection means can be realized with a simple configuration, and the impedance of the open phase is low when the freewheeling diode is conducting, so that the reverse rotation can be detected in a state where it is hardly affected by noise.

Next, the operation of the above embodiment will be described with reference to the control circuit 40.
6 will be described with reference to flowcharts of FIGS.

In the control circuit, when an operation command is input from an external control device while the step motor 10 is stopped,
Execution of the control process shown in FIG. 6 is started, and first, in step S1
Then, a process of measuring the natural vibration angular frequency β of the rotor in the step motor 10 is performed, and then the process proceeds to step S2, where the acceleration control process is performed, and then step S3 is performed.
To execute the constant speed control process, and then to step S
Then, the process proceeds to 4, and the deceleration control process is executed, and the process ends.

Here, as shown in FIG. 7, the natural vibration angular frequency measurement processing in step S1 is executed as a timer interrupt processing at predetermined time intervals set to a time short enough to measure the natural vibration angular frequency. First, in step S10,
It is determined whether or not the measurement completion flag FE indicating whether or not the measurement of the natural vibration angular frequency has been completed is set to “1”. When the measurement completion flag FE is reset to “0”, the measurement of the natural vibration angular frequency is performed. When it is determined that the process is not completed, the process proceeds to step S11, in which a commutation pulse for rotating the rotor of the step motor 10 by one step is output to the gate of each transistor of the inverter 23, and then the process proceeds to step S12.

In this step S12, it is determined whether or not a measurement state flag FS indicating whether or not the measurement has been started is set to "1". If this is reset to "0", the measurement is started. It is determined that the current time has elapsed, and the process proceeds to step S13, where the count value N _{C of the} counter is counted.
Is cleared to "0" and then the process proceeds to step S14.
After the measurement state flag FS is set to "1", the process proceeds to step S15, where it is determined whether or not a signal indicating that the time t1 has been detected has been input from the freewheeling diode conduction detection circuit 30, and no signal has been input. In some cases, the timer interrupt processing ends.

On the other hand, if the result of the determination in step S12 is that the measurement state flag FS is set to "1", it is determined that the natural vibration angular frequency β is being measured, and the flow shifts to step S16, where the current Count value N of the counter
_After incrementing _C by “1”, the step S
Move to 15. When the result of the determination in step S15 is that a signal indicating that time t1 has been detected is input from the reflux diode conduction detection circuit 30, the process proceeds to step S17, where the count value N _{C of the} counter is doubled, and Elapsed time after multiplying the interrupt cycle T _T (natural oscillation cycle)
In addition to calculating T _T2 , the natural vibration angular frequency β is calculated by performing the calculation of the following equation (1), and the reciprocal 1 / β is calculated and stored in a predetermined storage area.

Β = 2π / T _T2 (1) Next, the process proceeds to step S18, where the measurement completion flag F
After setting E to “1”, the process proceeds to step S19,
It is determined whether or not a signal indicating that time t2 has been detected has been input from the reflux diode conduction detection circuit 30. If the signal indicating that time t2 has not been input, the timer interrupt processing is terminated and the signal has been input. At step S20, the measurement completion flag FE and the measurement state flag FS are reset to "0", respectively, and then the natural vibration angular frequency measurement process is terminated, and the routine proceeds to step S2 in FIG.

Further, when the result of determination in step S10 is that the measurement end flag FE is set to "1", the flow directly jumps to step S19. The processing in step S1 in FIG. 6 and the processing in FIG. 7 correspond to the natural vibration angular frequency measuring means.

As shown in FIG. 8, the acceleration control process executed in step S2 of FIG.
After clearing the number of driving times n to “0”, step S2
The process proceeds to S2, where a commutation pulse for rotating the rotor by one step is output to the inverter 23, and the process proceeds to S23.

In step S23, a value obtained by incrementing the number of times of drive n by "1" is set as a new number of times of drive n.
Is referred to the phase angle calculation storage table based on the phase angle φ.
_N is calculated, and then the process proceeds to step S25 to calculate the output interval T _N of the commutation signal to the inverter 23 by performing the calculation of the following equation (2) based on the phase angle φ _N and the natural vibration angular frequency β. I do.

T _N = (π / 2−φ _N ) / β (2) Next, the processing shifts to step S26 to start the timer, and then shifts to step S27, where the timer count value _NT is calculated. It is determined whether or not the output interval T _N has been reached. If the output interval T _N has not been reached, the process waits until the output interval T _N has been reached. If the output interval T _N has been reached, the process proceeds to step S28 to stop the timer, and then proceeds to step S29. It is determined whether or not the acceleration state has been completed. When the acceleration state is continued, the process returns to step S22. When the acceleration state has been completed, the acceleration control processing is ended and the constant speed control processing in step S3 in FIG. Move to

Here, the reason why the output interval T _N of the commutation signal to the inverter 23 is calculated by the above equation (2) is as follows.

Inverter 23 for driving step motor
When the commutation pulse is given to the rotor, the operation of the rotor can be expressed as a secondary vibration system, and the state equation of the secondary vibration system can be expressed by the following equation (3).

Θ (s) = (sθ (0) + ω (0)) / (s ² + β ² ) (3) where θ (0) is the initial value of the position, and ω (0) is Initial speed.

Then, as shown in FIG. 11, when shifting to the acceleration state from the time t ₁ when the stepping motor 10 is stopped, first consider the case where the rotor is advanced by one step from the stopped state. At this time, the initial velocity ω (0) is “0”, and the initial position value θ (0) is “−1”.
Set as Here, the position is normalized by considering one step as “1”.

By substituting the initial velocity ω (0) = 0 and the initial position value θ (0) = − 1 at this time into the above equation (3), the above equation (3) becomes the following equation (4). Becomes

Θ (s) = − s / (s ² + β ² ) (4) This formula (4) is subjected to inverse Laplace transform and the position θ (t)
Is differentiated, the position θ (t) and the speed ω (t) expressed by the following equations (5) and (6) can be calculated.

Θ (t) = − cosβt (5) ω (t) = dθ (t) / dt = βsinβt (6) That is, the period T _{1 at} which βt becomes π / 2 = At π / 2β, the position θ (t) becomes “0”, and the velocity ω (t) becomes the maximum.
By rotating the next one step at a time t ₂ when the T ₁ is passed, it is possible to start rotating in the next second time step without rotor is reversed.

If the rotor is advanced by one step at this time t ₂ , the initial values are equivalent to ω (0) = β and θ (0) = − 1, and therefore these values are changed to the above (3). By substituting into the equation, Θ (s) = (− s + β) / (s ² + β ² ) (7), and by inverse Laplace transform and differentiation, θ (t) = − √ 2cos (βt + π / 4) (8) ω (t) = √2 · β · sin (βt + π / 4) (9)

Accordingly, θ (t) = 0 at the period T ₂ where βt + π / 4 = π / 2, so that the rotation of the third step is started at T ₂ = π / 4β, so that the rotor is rotated. The rotation of the third step can be started without reversing.

In this way, when the rotation of each step is sequentially repeated n times and accelerated, the initial value is ω _N
(0) = √ (n−1) · β, θ _N (0) = − 1,
The position θ (t) and velocity ω (t) are given by the following equation (10) and (1)
It is expressed by the expression 1).

Θ (t) = − √ncos (βt + φ _N ) (10) ω (t) = √n · β · sin (βt + φ _N ) (11) where φ _N is a phase Angle, φ _N = tan ⁻¹ √ (n−
The phase angle φ _N is calculated in correspondence with the number of driving times n, and the calculation result is used to create a phase angle calculating storage table using the number of driving times n as an index.
And the like.

Next, as shown in FIG. 9, the constant speed control process in step S3 of FIG.
Then, by referring to a storage table stored in advance based on the number of driving times n, sin ⁻¹ (1/1) for calculating the output interval T _N ′ is used.
2√n) is calculated, and the process then proceeds to step S32 to calculate an output interval T _N ′ for performing constant speed control according to the following equation (12).

T _N ′ = (1 / β) sin ⁻¹ (1 / 2√n) (12) The calculation of the expression (12) is based on the natural vibration angular frequency β stored in the predetermined area. And the si calculated in step S31
By multiplying by a value of n ^-1 (1 /） n), the multiplication is performed only by one multiplication process.

[0073] Then, the process proceeds to step S33, the timer is started, then the timer count value N _T2 is output interval T _N goes to Step S34 'to determine whether or not reached, the output interval T _N' When the output interval T _N ′ has not been reached, the process waits until the output interval T _N ′ has been reached.

In this step S35, the inverter 23
The step motor 10 and outputs a commutation pulse to advance one step with respect to, and then proceeds to step S36, and proceeds from re-start the timer step S37, the timer count value N _T2 is output interval T _N ' Doubled value 2T
_It is determined whether or not _N 'has been reached. If it has not reached 2T _N ', the process waits until it has reached, and if it has reached 2T _N ', the flow shifts to step S38 to determine whether or not to shift to deceleration. When the constant speed state is to be continued, the above-described step S3 is performed.
Returning to step 5, when shifting to deceleration, the process shifts to the deceleration control process of step S4 in FIG.

The reason why the output interval T _N 'is calculated by the above equation (12) in this constant speed control process is as follows.

Assuming that the position θ (t) and the speed ω (t) at the end of acceleration are expressed by the above equations (10) and (11),
At this point, the position θ (t) is “0” and the speed ω (t) is at the maximum point. Therefore, if a commutation pulse is supplied to the inverter 23 at this point, the acceleration state will be continued.

For this reason, the commutation pulse is not supplied to the inverter 23 at the end of the acceleration, and the supply timing of the commutation pulse is inverted at the position θ (t) to reach, for example, + ／ (the period during this period is T T). _N ′), it is possible to shift from the acceleration state to the constant speed state.

For this reason, θ (t) = 1/2 and t = T _N
Assuming + _TN ′, the above equation (10) is represented by the following equation (13).

[0079] 1/2 = -√ncos {β ( T N + T N ') + φ N} By modifying ............ (13) where, 1/2 = -√n {-sin (βT N') become _{sin (φ N + βT N)} + cos (βT N ') cos (φ N + βT N)} ...... (14). Here, sin (φ _N + βT _N ) = 1, cos (φ _N +
βT _N ) = 0, the above equation (14) is
5)

1/2 = √nsin (βT _N ′) (15) When the output interval T _N ′ is obtained from the equation (15), T _N ′ is obtained.
= (1 / β) sin ^-1 (1 / √n), and the above (12)
It becomes an expression.

[0081] Thus, by adding the output interval of the constant speed state T _N 'by delaying the output of the commutation pulse output interval T _N during acceleration completion, the position of the rotor θ a (t) + 1 /
2. In this state, the output interval T is doubled again.
By supplying a commutation pulse to the inverter 23 at _N ', the position θ (t) repeats between -1/2 and +1/2, whereby the constant speed state can be maintained.

Further, as shown in FIG. 10, the deceleration control process in step S5 in FIG.
The output interval T _N + T _N ′ of the commutation pulse for shifting to the deceleration state is calculated by performing the calculation of the following equation (16). T _N + T _N ′ = (π / 2−φ _N ) / β + (1 / β) sin ⁻¹ (1 / 2√n) (16) The calculation of the expression (16) is performed by the acceleration described above. This is performed by storing the value of the output interval T _N calculated last in the control process and the output interval T _N 'calculated in the constant speed control process, and adding these.

Then, the flow shifts to step S42 to restart the timer, and then shifts to step S43, where it is determined whether or not the timer count value _NT3 has reached the output interval _TN + _TN '. If not, the process waits until it reaches the limit. If the count has reached, the process proceeds to step S44 to output a commutation pulse for advancing the step motor by one step to the inverter 23, and then proceeds to step S45. The value obtained by decrementing “1” is set as a new number of drive times n, and then the process proceeds to step S46 to determine whether or not the number of drive times n is “0”. If the number of drive times n is “0”, The control process of FIG. 5 is terminated as it is, and when n> 0, the process proceeds to step S47.

In this step S47, the phase angle φ _N is calculated by referring to the phase angle calculation storage table based on the number of times of driving n, and then the flow shifts to step S48, where (2)
The output interval T _N is calculated by performing the same operation as in the equation, and then the process proceeds to step S49 to restart the timer, and then proceeds to step S50 to determine whether the timer count value _NT4 has reached the output interval T _N. If the output interval T _N has not been reached, the process waits until the output interval T _N has been reached. If the output interval T _N has been reached, the process proceeds to step S44.

The processes in steps S2 to S4 in FIG. 6 and the processes in FIGS. 8 to 10 correspond to the control means, of which the processes in steps S23 to S25 in FIG. 8 and the processes in steps S31 and S32 in FIG. And steps S41 and S41 in FIG.
8 correspond to the output interval calculating means.
Steps S35 to S36, Step S2 in FIG.
6 to S28 and steps S42 to S4 in FIG.
The processes in steps S4, S49 and S50 correspond to the signal output means.

Therefore, it is assumed that the step motor 10 is stopped and no operation command is input from an external control device. In this state, when an acceleration operation command is input to the control circuit 40 from an external control device,
First, the natural vibration angular frequency measurement processing of FIG.
1 (a), at time t0, the stepping motor 10
Is output to the inverter 23 for driving the rotor by one step, and the rotor is moved to the position θ as shown in FIG.
(t) is driven from -1 to 0, during which a natural vibration angular frequency β of the rotor of the step motor 10 is calculated, and its reciprocal 1 / β is calculated. The natural vibration angular frequency measurement processing is ended at the time point t ₁ when the inversion is performed, and the process proceeds to the acceleration control processing in FIG.

In this acceleration control process, first, the number of times n of driving is set to “0” (step S21), and then a driving pulse for advancing the rotor of the step motor 10 by one step is output to the inverter 23 (step S22).

As a result, as shown in FIG. 11A, the rotor starts to accelerate as the speed ω (t) increases from time t ₁ , and the position θ (t) becomes as shown in FIG. 11B. As shown in FIG.

Next, the number of times of drive n is incremented to set a new number of times of drive n = 1 (step S23). Then, based on the number of times of drive n = 1, a phase angle calculation storage table is referred to and the phase is calculated. Calculate the angle φ ₁ (step S2
4) Based on the calculated phase angle φ ₁ and the reciprocal 1 / β of the natural vibration angular frequency β, the output interval T _N is calculated by performing the calculation of the equation (2) (step S25).

[0090] Then, the timer is started (step S26), the count value N _T1 of the timer output interval T _N
Wait until, when the count value N _T1 at time t ₂ reaches the output interval T _N, and outputs from the timer to stop the second round of commutation pulses to the inverter 23 (step S
28, S29, S22).

At this time t ₂ , the rotor speed ω (t) becomes maximum and the position θ (t) becomes 1 as shown in FIG.
The position becomes “0” rotated by the step, and at this time t ₂ , a commutation pulse is output to the inverter 23,
The rotor speed ω (t) continuously increases again without reversing the rotor, and the position θ (t) rotates from −1 to “0”.

Thereafter, the number of driving times n is set to n = 2, and based on the number of driving times n = 2, the phase angle φ ₂ is calculated by referring to the phase angle calculation storage table. Based on φ ₂ and the reciprocal of the natural vibration angular frequency β, the calculation of the above equation (2) is performed to obtain a new second output interval T ₂
Is calculated, at time t ₃ when the output interval T ₂ has passed the third
The fourth commutation pulse is output to the inverter 23 to accelerate the rotor again, and then at time t ₄ , the fourth commutation pulse is output to the inverter 23 to accelerate the rotor again. Then, the fourth output interval T ₄ is calculated.

In this acceleration state, the position θ (t) becomes −1 and 0
, A positive average torque is generated to generate acceleration, and the acceleration state is continued.

[0094] During this acceleration, the constant-speed operation command from an external control device are inputted to the control circuit 40, the acceleration control processing of FIG. 8, the time t of the timer count value N _T1 reaches the output interval T _{4 In} step ₅ , the process proceeds to step S28 to stop the timer. Then, the process proceeds to step S28. Since the constant speed operation command has been input, the process proceeds to step S22 without outputting a commutation pulse to the inverter 23. After ending the acceleration control process, the process proceeds to the constant speed control process of FIG.

[0095] Therefore, the rotor of the step motor 10, as shown in FIG. 11 (a), since the commutation pulse at time t ₅ the original speed ω of (t) is "0" is not output to the inverter forward The state is reversed from the state to the reverse state, and the speed ω (t) decreases.

On the other hand, in the constant speed control process shown in FIG. 9, since the number of driving times n = 4, the storage table is referred to based on the number of driving times n = 4 and sin ⁻¹ (1 / 2√4) calculating the value of) (step S31), then the (12) by performing the calculation of the equation, 'is calculated, the constant speed control output interval T _4' constant speed control output interval T ₄ time has passed commutation pulses of one step at t ₆ is output to the inverter 23.

At the time T ₆ , the rotor of the step motor 10 rotates in the reverse direction, and the speed ω (t) is in a decelerating state.
The position θ (t) of the rotor reaches + 戻 っ and is a position returned by half a step. By commutating pulses in one step in this time t ₆ is supplied to the inverter 23,
The rotor of the stepping motor 10 without causing transient accelerating rotating forward again, the speed omega (t) becomes the deceleration state after reaching the maximum point at time t _7, the timer count value N _T3 at time t ₈ is When the output interval reaches twice the output interval T ₄ ′, a commutation pulse for one step is output to the inverter 23 again. Then, at time t ₉ , the speed ω (t) reaches the maximum point, and then the motor enters a deceleration state. _{When the} timer count value _NT2 is ₁₀ , the output interval T
_When it reaches twice ₄ ', a commutation pulse for one step is output to the inverter 23 again.

Accordingly, in this constant speed control state, the position θ (t) changes within a range of ± 1/2, so that the average torque becomes “0” and the rotor of the step motor 10 is driven at a constant speed. Is done.

[0099] Thereafter, when the deceleration command from an external control device are inputted to the control circuit 40 at the time when after time t _10, the constant speed control process in FIG. 9, the timer count value N
When _T3 reaches twice the output interval T ₄ ', step S36
Then, the process proceeds to step S37, and since the deceleration operation command has been input, the constant speed control process in FIG. 9 ends, and the process proceeds to the deceleration control process in FIG.

In this deceleration control process, an output interval T ₄ ′ until the rotor speed ω (t) of the step motor 10 reaches the maximum point in step S 41 and an output interval until the commutation pulse is output during acceleration are output. After calculating the output interval T ₄ + T ₄ ′ by adding T ₄ , the timer is restarted,
Count value N _T4 of the timer output interval T ₄ + T ₄ 'until it reaches the wait, output interval T ₄ + T ₄ at time t _11'
Is reached, the process proceeds to step S44 to output a commutation pulse for one step to the inverter 23,
The rotor of the step motor 10 is driven for one step.

[0102] Since the commutation pulse when position the rotor is reversed in the time t ₁₁ in the step motor 10 theta of (t) has reached the +1 is supplied to the inverter 23, the transition to the deceleration state without transients It is performed smoothly.

Thereafter, the number of driving times n is decremented by “1” to become n = 3, a phase angle φ ₃ corresponding to the number of driving times n = ₃ is calculated, and an output interval T ₃ corresponding thereto is calculated. timer count value n _T5 reaches the output interval T _3, the position theta (t) is again commutation pulse at time t ₁₂ to reach +1 is outputted to the inverter 23, then drive count n n = 2, and this Phase angle φ ₂ according to the number of driving times n = ₂
Is calculated, and the output interval T ₂ is calculated accordingly. When the timer count value NT ₅ reaches the output interval T ₂ , the position θ
Again commutation pulse at time t ₁₃ to (t) reaches +1 is outputted to the inverter 23, and further, the drive number n is n = 1, and the phase angle phi ₁ according to the number of times of driving n = 1 is calculated, is output interval T ₁ corresponding to this calculation, the timer count value N _T5 reaches the output interval T _1, the position theta (t) +1
Again commutation pulse at time t ₁₄ to reach is output to the inverter 23. Thereafter, when the process shifts to step S45, the number of times of driving n becomes n = 0, so that the deceleration control process ends without shifting from step S46 to step S47, and the control process of FIG. 6 also ends.

In the deceleration control state as described above, FIG.
As shown in (b), the position θ (t) falls within the range of 0 and +1.
Deceleration is generated by generating a negative average torque.
And the deceleration state is continued, and the driving frequency n becomes n = 1.
Output interval T₁ Time t has elapsed ₁₄For one step
Current pulse is output to the inverter 23,
In the same way as the final step delay damping in
Movement can be suppressed.

In the above embodiment, the acceleration / deceleration in the acceleration / deceleration state cannot be controlled. However, when the control circuit 40 supplies the commutation pulse of the inverter 23, the commutation signal is converted to the pulse width modulation circuit 41. By controlling the duty ratio at this time by forming a commutation pulse by pulse width modulation, the current value of the three-phase AC signal supplied to the step motor 10 can be controlled, thereby controlling the acceleration / deceleration. can do.

As described above, according to the above-described embodiment, in the acceleration state and the deceleration state, acceleration and deceleration can be performed without vibration, and when shifting from the acceleration state to the constant speed state and from the constant speed state to the deceleration state. The transition can also be made smoothly without vibration even when the transition to.

Moreover, since the measurement of the natural vibration angular frequency β is performed by grasping the conduction state of the return diode in the open phase, the rotor of the step motor 10 can be used without providing an encoder capable of detecting the rotation direction. The turning point from normal rotation to reverse rotation can be accurately detected,
By measuring the elapsed time from the time when the commutation pulse for one step is given to the inverter 23 to the time when the rotor switches from normal rotation to reverse rotation, the natural vibration angular frequency β can be accurately measured.

Then, a three-phase H having a step angle of 1.58 °, a holding torque of 700 gcm, and a moment of inertia of 80 gcm ^2.
FIG. 12 shows the results of an experiment of the position response characteristics by using a B step motor, mounting a rotary encoder on the rotation shaft of the step motor, measuring the position θ and the speed ω, and performing an experiment on the position response characteristics. In FIG. 12, the rotor position θ is shown in a range of ± π (electrical angle), and its initial position is set to −π. Also, a commutation pulse is given to the inverter when the commutation signal rises and falls. First, after the commutation pulse, the conduction of the open-phase freewheeling diode is detected to measure the natural oscillation angular frequency β, and two-step commutation is performed. At this time, the speed ω is substantially “0”, and the position θ has moved from the initial position −π by ３π (two steps). In the acceleration period, the commutation timing is determined based on the measured β, and the commutation is repeated at the time when the speed is maximum.
In the case of FIG. 12, the motor is accelerated three times, performs a constant speed operation of six pulses (one cycle of the electrical angle), decelerates three times, and stops. During acceleration, during the transition period from acceleration to constant speed and from constant speed to deceleration, unnecessary vibration does not occur during any of stop,
Good driving characteristics were obtained, indicating the validity of the method for controlling the commutation pulse described above.

Further, FIG.
FIG. 12 shows an experimental result of the position response when the frequency is increased by a factor of 5, and the vibration period is extended by 1.5 times as compared with the case of FIG.
Unnecessary vibration does not occur, and good acceleration / deceleration characteristics similar to those in FIG. 12 are obtained. This means that since the natural vibration period is measured by sensorless rotation direction detection, even if the moment of inertia changes, good drive characteristics can be obtained without any special setting.

In the above embodiment, the three-phase HB
Although the case where the present invention is applied to the step motor has been described, the present invention is not limited to this, and the present invention may be applied to other types such as a 5-phase hybrid step motor, a PM type step motor, a VR type step motor, and the like. Can be applied.

Further, in the above embodiment, the case where the present invention is applied to the three-phase HB stepping motor for driving the carriage of the printer has been described. However, the present invention is not limited to this. The present invention can be applied to a step motor that drives an arbitrary moving mechanism.

Further, in the above-described embodiment, the case where the measurement of the natural vibration angular frequency β is performed to detect the reversal of the rotation direction of the rotor of the step motor by detecting the common state of the return diode in the open phase. However, the present invention is not limited to this, and an encoder capable of outputting a pulse signal having a phase difference of, for example, 90 degrees, capable of detecting the rotation direction, is applied to the rotation axis of the step motor 10, and the rotation direction of the rotor is reversed. The point of time at which the operation is performed may be detected.

Further, in the above-described embodiment, the case where the position θ (t) is controlled in the range of ± 1/2 in the constant speed running state has been described. However, the present invention is not limited to this. The value may be set in an arbitrary range within a range of about ± 1/4 to ± 3/4. In this case, the value on the left side of Expressions (13) to (15) is changed to a value in the setting range. do it.

Further, in the above-described embodiment, the case where the vehicle shifts from the acceleration state to the constant speed state and shifts from the constant speed state to the deceleration state and stops is described. However, the present invention is not limited to this. The step motor can be controlled with various speed patterns, such as shifting from the acceleration state to the constant speed state and further shifting to the acceleration state, shifting from the deceleration state to the constant speed state and then shifting to the deceleration state again.

[0114]

As described above, claims 1 and 10
According to the invention, the natural vibration of the step motor is approximated to a secondary vibration system, and the output interval of the commutation signal to the inverter means is calculated based on the secondary vibration system equation. By outputting the commutation signal to the inverter means, a commutation signal can be output at the maximum point of the rotor speed in consideration of the natural vibration of the rotor, and the inverter means can perform commutation by advancing the step motor by one step. An effect is obtained that unnecessary vibration can be reliably suppressed even if the motor constant or the load changes.

According to the second aspect of the present invention, the output interval T _N for outputting a commutation signal for advancing the stepping motor by one step to the inverter means is calculated based on each frequency β and the phase angle φ _N of the natural vibration. By doing so, the commutation signal for the next step can be accurately output at the time when the rotor speed becomes maximum, and the effect that vibrationless settling can be performed can be obtained.

Further, according to the third aspect of the present invention, by referring to the storage table based on the number of driving times n,
The phase angle φ _N can be calculated, the phase angle φ _N can be calculated without performing a complicated operation, and the output interval T
_By calculating and storing the reciprocal 1 / β of the natural vibration angular frequency β in advance also in the calculation of _N , an effect is obtained that the sum operation and the product operation can be easily performed only once each. .

Further, according to the fourth aspect of the present invention, when shifting from the acceleration state to the constant speed state, the output interval T _N during acceleration is changed to the output interval T _N ′ at constant speed = (1 / β ) Sin
By adding ^-1 (1 / 2√n), the output of the commutation signal is delayed to shift to a constant speed state without generating vibration, and thereafter commutation is performed at every constant speed output interval T _N '. By supplying the signal to the inverter means, it is possible to obtain an effect that unnecessary vibration can be surely suppressed and a constant speed state can be maintained.

According to the fifth aspect of the present invention, sin ^-1 (1 / 2√n) can be immediately calculated by referring to the storage table based on the number of driving times n, and the constant speed can be calculated. output interval T _N when 'by previously calculated and stored even 1 / beta calculation of, only output interval T _N of the constant-speed performs the sum operation and product operation respectively once' easily The effect that can be performed is obtained.

According to the invention of claim 6, the commutation signal supplied to the inverter means is pulse width modulated by the pulse width modulation means and supplied, and the duty ratio is controlled to supply the commutation signal to the step motor. By controlling the driving current to be applied, the effect of controlling the acceleration / deceleration during acceleration / deceleration can be obtained.

Further, according to the seventh aspect of the present invention, the natural vibration angular frequency β is measured by the natural vibration angular frequency measuring means before the start of the drive control. The effect that commutation signal control can be performed is obtained.

Further, according to the invention of claim 8, the rotor of the snap motor is driven for one step from the stop state, and the elapsed time at this time is measured to calculate the natural vibration angular frequency β. At this time, for one step of the rotor, an encoder capable of measuring the rotation direction of the rotor is used to measure the time from when the rotor starts to rotate forward to the time when the rotor starts rotating reversely, or the time from when the rotor starts to rotate backwards to when the rotor rotates forward. Is doubled, the natural vibration angular frequency β can be accurately calculated.

Further, according to the ninth aspect of the present invention, when the motor is a three-phase step motor, it is possible to detect the forward / reverse rotation of the rotor from the back electromotive force waveform appearing in the open phase, and use an encoder. Instead, by measuring the elapsed time of the forward / reverse rotation of the rotor, it is possible to obtain the effect that each natural vibration frequency β can be accurately calculated.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a specific configuration of a freewheeling diode conduction detection circuit.

FIG. 3 is an explanatory diagram illustrating a principle of detecting a point in time when the rotation direction is reversed during rotor vibration.

FIG. 4 is an explanatory diagram showing a chopping sequence when the open phase is a B phase.

FIG. 5 is an explanatory diagram showing a conduction state of a freewheel diode.

FIG. 6 is a flowchart illustrating an example of a control process of a control circuit.

FIG. 7 is a flowchart showing a specific example of a natural vibration angular frequency measurement process of FIG. 6;

FIG. 8 is a flowchart illustrating a specific example of the acceleration control process of FIG. 6;

FIG. 9 is a flowchart illustrating a specific example of the constant speed control process of FIG. 6;

FIG. 10 is a flowchart showing a specific example of the deceleration control process of FIG.

FIG. 11 is a time chart for explaining the operation of the present invention.

FIG. 12 is an explanatory diagram showing an experimental result of a position response characteristic.

FIG. 13 is an explanatory diagram showing an experimental result of a position response characteristic when the moment of inertia is set to 2.5 times.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Three-phase HB (hybrid) step motor 20 Drive circuit 21 Commercial AC power supply 22 Converter 23 Inverter 30 Freewheeling diode conduction detection circuit 31 Comparator part 32 Operational amplifier 33 Operational amplifier 34 Conduction diode change detection part 40 Control circuit 41 Pulse width modulation circuit Da ₊ Freewheel diode Da _- freewheel diode Db ₊ freewheel diode Db _- freewheel diode Dc ₊ freewheel diode Dc _- freewheel diode Ta ₊ transistor Ta _- transistor Tb ₊ transistor Tb _- transistor Tc ₊ transistor Tc _- transistor

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yasufumi Akagi 3-1-1 Tsushimanaka, Okayama City, Okayama Pref. Okayama University Faculty of Engineering, Department of Electrical and Electronic Engineering F-term (reference) HH24 HH35

Claims (10)

[Claims] 1. A step motor control device comprising: inverter means for driving a step motor based on a supplied commutation signal; and control means for generating a commutation signal to be supplied to the inverter means based on a drive command. Wherein the control means comprises: an output interval calculating means for calculating an output interval of the commutation signal based on a secondary vibration system equation based on a natural vibration angular frequency, an initial value of a position, and an initial speed; And a signal output means for outputting the commutation signal at an output interval calculated by the means. 2. The output interval calculating means calculates T _N = (π / 2−φ _N ) / β, where n is the number of drives, β is the natural vibration angular frequency, and φ is the phase angle during acceleration. 2. The stepping motor control device according to claim 1, wherein the stepping motor control device is configured to calculate a represented pulse interval T _N. 3. The step motor control device according to claim 2, wherein said output interval calculating means includes a storage table indicating a relationship between the number of driving times n and a phase angle φ _N. 4. When the pulse interval calculating means shifts from the acceleration state to the constant speed state, the number of driving times is n, the natural vibration angular frequency is β, and the pulse interval during acceleration is T _{N. N} + _TN ′ = _TN + (1 / β) sin ⁻¹ (1 / 2√
2. The stepping motor control device according to claim 1, wherein the pulse interval T _N ′ represented by n) is calculated. 5. The method according to claim 1, wherein the pulse interval calculating unit calculates the number of driving times n.
5. The step motor control device according to claim 4, further comprising a storage table that represents a relationship between the step motor and sin ⁻¹ (1 / 2√n). 6. The signal output means includes pulse width modulation means for forming a commutation signal to be supplied to the inverter means, and the acceleration is controlled by controlling a duty ratio of the pulse width modulation means. The step motor control device according to any one of claims 1 to 5, wherein the step motor control device is configured as follows. 7. The step according to claim 1, wherein said control means includes a natural vibration angular frequency measuring means for measuring a natural vibration angular frequency before starting drive control. Motor control device. 8. The natural vibration angular frequency measuring means drives the rotor by one step from a stopped state before starting drive control, and measures an elapsed time at this time to calculate a natural vibration angular frequency. The step motor control device according to claim 7, wherein: 9. The natural vibration angular frequency measuring means is configured to calculate a natural vibration angular frequency by measuring a back electromotive force waveform appearing in an open phase when the step motor is a three-phase step motor. 8. The method according to claim 7, wherein
3. The step motor control device according to claim 1. 10. A step motor control method for generating a commutation signal based on a drive command and supplying the generated commutation signal to an inverter means to control open-loop driving of a step motor. Calculating the output interval of the commutation signal based on a natural vibration angular frequency, an initial value of the position, and a secondary vibration system equation based on the initial speed; and commutation at the calculated output interval. Outputting a signal to the inverter means.