JPH01186198A - Control method for stepping motor - Google Patents

Abstract

PURPOSE:To drive a stepping motor at the maximum speed without step-out, and to shorten the moving time by changing a stepping rate according to the detection of the step-out. CONSTITUTION:When a stepping motor 1 is driven at a certain stepping rate R1, the stepping rate is decreased to a low value such as R2 when a mis-step is detected. When the stepping rate is lowered to the R2, acceleration is decreased, and torque is increased, thus generating no mis-step in the next drive. Mis-step is detected by detecting a current position after driving the stepping motor 1, thus detecting step drive only by the number of steps controlled, in other words, detecting mis-step.

Description

[Detailed description of the invention] [Table of contents] Overview Industrial field of application Conventional technology Problems to be solved by the invention Means for solving the problems (Fig. 1) Working example (a) Structure of one example Explanation (Fig. 2) (b) Explanation of the drive of the step motor (Fig. 3, Fig. 4) (c) Explanation of the control method of one embodiment (Fig. 5, Fig. 6, Fig. 7) (d) Description of Other Embodiments Effects of the Invention [Summary] Regarding a step motor control method for driving a step motor in an open loop-Ill for a desired number of steps at a predetermined step rate, it is possible to enable high-speed drive and prevent missteps. A step motor control method in which a control unit controls excitation phase switching of a step motor at a predetermined step rate to drive the step motor a desired number of steps, the control unit controlling the step motor after driving. The current position is detected, the presence or absence of a misstep of the step motor is determined based on the detected current position, and the step rate is changed in accordance with the determination of the presence or absence of the misstep.

[Industrial application field]

The present invention relates to a step motor control method for driving a step motor using open loop control for a desired number of steps at a predetermined step rate.

Step motors are widely used in various moving mechanisms because they perform step operations.

In such a step motor, there is a need for a technology that can solve the conflicting problems of high-speed drive and prevention of missteps (stepping off).

[Conventional technology]

Closed-loop control and open-loop control are conventionally known as methods for controlling step motors.

In closed loop control, a position detector such as an encoder is provided on the step motor, and each time the step motor 1 is driven step by step, it is confirmed that the motor has moved one step based on the output of the position detector, and then the next step is driven.

In such a closed-loop control, the step motor can be driven without missteps even if the load fluctuates, so the operation is reliable, but high-speed driving is difficult and the configuration is complicated.

For this reason, open loop control is widely used.

In open loop control, the excitation phase is switched at a predetermined step rate to drive the step motor a desired number of steps, and the operation of the step motor is not checked at all during driving.

Therefore, the configuration can be simplified and high-speed driving is possible.

[Problem to be solved by the invention]

By the way, in open loop control, the step rate (steps/5 seconds) matches the speed of the step motor.

Therefore, in order to drive the step motor at high speed, the step rate may be increased.

However, in conventional control methods, the step rate is fixed to one type, so if a high-speed step rate is adopted, the required torque changes due to variations in the mechanism of the moving mechanism and fluctuations in the power supply and temperature, resulting in frequent missteps. (step-out) occurs, and device performance deteriorates.

For this reason, in the past, the step rate had to be determined to avoid missteps even under the worst conditions, and there was a problem in that it was difficult to increase the driving speed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for controlling a step motor that can be driven at high speed and prevent missteps.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

In the figure, 1 is a step motor, which may be either a rotary type or a linear type, and is driven in steps by excitation phase switching, and 8 is a control unit that controls excitation phase switching of the step motor 1 at a predetermined step rate. Step motor 1
is driven by a desired number of steps.

In the present invention, the control unit 8 checks the current position of the step motor 1 after driving, determines whether there is a misstep based on the current position, and changes the step rate based on the determination.

[Effect]

In the present invention, the step rate is made variable because the load changes not only due to the device itself but also due to the use environment such as the slippage of the guide rail due to temperature (mainly due to changes in oil clay).

Then, as shown in Fig. 1(B), there is a Stella play) R1
When the step motor 1 is driven, if a misstep is detected, the step rate is changed to a low value like R2.

If the step rate is set as low as R2, the acceleration will be reduced and the torque will be increased, so that no misstep will occur in the next drive.

By detecting the current position of the step motor after driving, a misstep can be detected to determine whether the step has been driven by the controlled number of steps, that is, whether a misstep has occurred.

〔Example〕

(a) Description of configuration of one embodiment FIG. 2 is a block diagram of one embodiment of the present invention, showing an optical disk device, in which a step motor 1 is used to move and position an optical head.

In the figure, the same components as those explained in FIG. 1 are indicated by the same symbols, and 2 is an optical disk, which is rotated by a spindle motor 2a, and information tracks are provided in a spiral shape at intervals of 1 to 2 microns. 3 is an optical head, which is positioned by moving straight in the radial direction of the optical disc 2 through a rotation-straight conversion mechanism 1a such as a steel belt by the rotation of the step motor 1, and irradiates the optical disc 2 with a light beam. It receives reflected light.

4a and 4b are step motor drive circuits, which supply the step motor 1 with an A-phase excitation current ia and a B-phase excitation current ib.
5 is a control register which supplies A-phase and B-phase drive pattern signals to the human phase and B-phase drive circuits 4a and 4b. a % A phase current control signal 1 a,, 1 a
t, 33-phase phase signal Pb, B-phase current control signal 1b, .
Ilb, is set, and the A-phase phase signal P a s A-phase current control signal 1aI, la@ is sent to the A-phase drive circuit 4a as an A-phase drive pattern signal, the B-phase phase signal Pb, the B-phase current control signal 1b, . 2b8 is outputted to the B-phase drive circuit 4b as a B-phase drive pattern signal.

6 is a track servo control circuit which creates a track error signal from the light reception signal of the optical head 3, generates a track servo signal TSV, and controls the light beam of the optical head 3 to follow the trunk; 7 is an RF generation circuit This is to create an RF (reproduction) signal from the light reception signal of the optical head 3.

Reference numeral 8 denotes the aforementioned control section, which is composed of a microprocessor, and drives the step motor 1 by controlling the excitation phase switching by the number of command steps A, and also controls the track servo control section 6.
It controls the operations of timer 8a and memory 8.
Contains b.

The memory 8b stores the number of steps A1, step rate table pointer B1, current stepper phase Y, and step rate down number S, as well as drive patterns S (Y) for each stepper phase, which will be described later in FIG. 4(C). drive pattern table S (Y), step rate table T (B) storing excitation phase switching time (waiting time) for variable deceleration control, which will be described later in FIG. 4(B), and step rate table T In (B), the number N of tables, the number M of stepper phases of the step motor 1, and the one down time t of the step rate are stored.

9 is a power amplifier, and a control unit (hereinafter referred to as MPU) 8
10 is a spindle servo circuit which servo-controls a spindle motor 2a that rotates the optical disk 2 according to instructions from the MPU 8.

The optical head 3 performs recording/reproduction by irradiating the optical disc 2 with light emitted from a 3° semiconductor laser as a light source through a lens 31, a polarizing beam splitter 32, a 1/4 wavelength plate 33, and an objective lens 34. , the reflected light from the optical disk 2 is passed through the objective lens 34.1/4 wavelength plate 33
, the light is received by a four-split photodetector 36 from a condenser lens 35 via a polarized beam splinter 32.

The objective lens 34 is provided with a track actuator 34a that moves in the track direction in the horizontal direction in the figure, and moves the objective lens 34 in the track direction to cause the light beam to follow the track.

In this optical disk device, when the MPU 8 receives a seek command from a higher level, it drives the step motor 1 to move the optical head 3 to a target track.

When the optical head 3 is positioned to the target trunk and the coarse control is completed, the MPU 8 turns on the trunk servo control circuit 6 and controls the drive of the track actuator 34a using the trunk error signal TES created from the light reception signal from the 4-division light receiver 36. Then, the optical beam is made to follow the track and fine JTJ (lens seek control) is performed.

Then, when the seek is completed, the MPU 8 waits for the arrival of a read/write command from the higher level.

In such an optical disk device, the inertia of the optical head 3 is large and the access speed depends on the step rate, so this is particularly effective.

(b) Description of driving the step motor FIG. 3 is a block diagram of a step motor drive circuit, and FIG. 4 is an explanatory diagram of a step motor drive table.

Figure 3 shows the drive circuit for one phase, and in Figure 2,
Since the step motor is a two-phase motor, a pair of motors as shown in FIG. 3 are provided for the A phase and B phase.

In the figure, 40 is an output circuit section, which includes four transistors T.
RI, TR2, TR3, and TR4 form an H-type bridge, which is a so-called bipolar drive excitation circuit, and diodes D1 to D4 for suppressing spikes are provided in parallel to each transistor TRI to TR4.
Inverter 11.12 is installed at the base of TR2, and transistors TR3 and TR4 (three (7) NOR
(N.

T OR) circuits N1 and N2 are provided.

Further, a drive voltage Vm is supplied to the collector sides of the transistors TRI and TR2, and the emitters of the transistors TR3 and TR4 are connected to a current detection resistor rd.

Reference numeral 41 denotes a logic input section, in which a Schmitt trigger circuit ST for removing noise from the phase signal Pa (Pb) inputted from the MPU 8 (control register 5) and transistors TRI to TR4 of the output circuit section 40 are connected during phase switching. A delay circuit DL for preventing a short circuit and an inverter 15 for inverting one output of the delay circuit DL and applying it to the inverter 11 and the NOR circuit N2 of the output circuit section 40 are provided. The other output is input to the inverter 12 and NOR circuit N1 of the output circuit section 40.

In addition, current control signals 1a, (j!b,), from the MPU 8
Four antagonists) Al-A4 are provided which generate current level signals in response to II az (lbz).

AND gate A1 takes the AND of the inverted signals of the current control signals 1a, , lag, and generates a large current level signal H3, and the AND gate A2 takes the AND of the inverted signals of the current control signals 1a, , lag, and the current control signal lat. and generates a medium current level signal MS, Antogae) A3 takes the AND of the current control signal 1a and the inverted signal of current control signal βa2, and generates a small current level signal LS, and Antogae) A4 generates a current control signal. The AND of the signals Ea, lat is performed to obtain the zero current level signal Z.
S is applied to the NOR circuits N1 and N2 of the output circuit section 40.

42 is a current detection unit, which includes four voltage dividing resistors rl, rz, r5, r4 that divide the reference voltage VR, and the divided voltages of each voltage dividing resistor V r 1 s V r 2, Vr3 (Vr,>V
rz>Vr,) is input to the e side as a reference voltage, and e detection potentials Vs of the current detection resistor rd are input. And gate A1, A2, A3
It operates according to high, medium, and small current level signals H3SMS and LS.

43 is a single pulse generating section, and 3 of the current detecting section 42
It is triggered by the rising edge of the output of one of the comparators C1, C2, C3 and generates a single pulse to
It is composed of monostable multi-by-break MMB output from R circuits N1 and N2.

Incidentally, the motor winding 1a (1b) of the step motor 1 is H
It is connected to a connection point between transistors TR1 to TR4 forming a type bridge, that is, a connection point between transistors TRI and TR3 and a connection point between transistors TR2 and TR4.

The basic operation of this circuit is that the direction of the current flowing through the winding 1a (lb) is selected by the phase signal Pa (Pb), and the magnitude of the flowing current is determined by the current control signal lat (lb+).
, l a2 (j! bz).

That is, the drive circuit is capable of taking four current values, large, medium, small, and zero, within a certain maximum drive current range, and is capable of quarter-step or microstep driving.

For example, if the phase signal Pa is "1" (high level), the transistors TRI and TR4 are turned on, and the winding 1
A forward current flows from the transistor TRI to the transistor TR4 through the transistor a.

Conversely, if the phase signal Pa is "O" (low level), the transistors TR2 and TR3 are turned on, and a reverse current flows through the winding 1a from the transistor TR2 to the transistor TR3.

On the other hand, the magnitude of the current flowing through the winding is determined by the current control ffi
No. 1 If both a + and la are 1" (high level), the zero current level signal ZS from A4 is NO.
R circuits N1 and N2, and transistors TR3 and T
R4 is turned off and no current flows through winding 1a, regardless of phase signal Pa.

In addition, the current control signal Ital is “1” (high level),
If la2 is “01” (low level), AND gate A
3 to small current level signal 1. S is generated, comparator C3 operates, and compares reference voltage Vr3 and detection potential Vs. When V s > V r3, an output is generated from comparator C3, triggering monostable multivibrator MMB, and generating a constant width pulse. is output to NOR circuits N1 and N2.

As a result, transistors TR3 and TR4 are turned off for a certain period of time regardless of phase signal Pa.

That is, the current flowing through the motor winding 1a is switched off for a certain period of time, and after the elapse of the certain period, the transistor TR3 or TR4 is turned on again by the phase signal Pa, and the current flows through the motor winding 1a.

Therefore, the current flowing through the motor winding 1a is controlled to be a constant current by the switching type regulation circuit.
Since this constant current is determined by the reference voltage Vr3 of the comparator C3, it is driven with a small current.

Similarly, the current control signal 1a is “0” (low level)
, ffaz are "1" (high level), the comparator C2 operates, and in a similar operation, the motor winding 1a is driven with a medium current, and the current control signal 1a.

, lat are both "0" (low level), the comparator C1 operates, and the motor winding 1a is driven with a large current in the same manner.

On the other hand, the distribution operation of the step motor 1 is performed by the MPU 8, and the control register 5 is stored in the table S(Y) of the memory 8b.
, T (B) and is rewritten at each switching timing.

For example, taking 1-2 phase excitation as an example, the MPU 8 changes the drive pattern as shown in FIG. 4(C).

In this example, the A-phase current control signals 1a, , la are set to the same la, and the B-phase current control signals 1b, , xb are set to the same z
b, using large current and zero current, and phase signal PazP
Determine the current polarity with b.

That is, as in step S1 (, Pa="l", βa=
'1'', pb-“0”, lb=”0”, then A
The phase current ia is zero, the B-phase current ib is negative, and one phase is excited.

Next, in step S2, when 11a is changed from "l" to 0, the A-phase current ia remains positive and the B-phase current Lb remains negative.
Excited in two phases.

Thereafter, 1-2 phase excitation is repeated until step S8,
In step S8, the process returns to step S1.

Therefore, one sequence has 8 steps, the A phase signal Pa is changed every 4 steps, and the B phase signal Pb is changed every 4 steps.
Similarly, the A-phase current control signal 1a (la, 1a-) is set to "1" every 4 steps, and the B-phase current control signal 1b (zb, , βbz
) is delayed by 2 steps and set to ``11'' every 4 steps.

The MPU 8 writes the pattern of each step 5l-38 in the table S (Y) in the no. 1-li 8b, and reads out the pattern of the next step at each excitation switching timing.
Set in control register 5.

This excitation switching timing is controlled by a step rate table T(B) as shown in FIGS. 4(A) and 4(B).

That is, as shown in FIG. 4(A), when the acceleration/deceleration control curve is set, the excitation time varies from the maximum T(1) to the minimum T.
(N).

Therefore, as shown in FIG. 4(B) with pointer B,
Step rate table T(1) to T(N)
If B) is prepared in the memory 8b, T(1) during acceleration.
Acceleration and deceleration control can be performed by changing the pointer B from T (N) toward T (1) during deceleration and reading out table T (B).

In other words, the excitation time (excitation phase switching interval) of the pattern shown in FIG. 4(B) becomes gradually shorter during acceleration, gradually becomes longer during deceleration, and remains the same during constant speed.

(c) Description of one embodiment of control method FIG. 5 is a track access processing flow diagram of one embodiment of the present invention, FIG. 6 is a step motor control flow diagram of one embodiment of the present invention, and FIG. 7 is one of the embodiments of the present invention. It is an explanatory diagram of an example operation.

The track access operation when a seek command is received from a higher level will be explained using FIG.

(2) The MPU 8 extracts the ID from the RF signal RFS output from the RF generation circuit 7 based on the light reception signal of the optical head 3, and detects the track address where the light beam is located.

Then, a difference ΔP, which is the difference between this trunk address (current address) Pr and the target track address Pa, is calculated.

(2) Next, the MPU 8 checks whether the difference ΔP is "0".

If OΔP=0, it is checked whether the optical beam can be positioned to the target trunk by seeking (movement in the track direction) of the lens 34 of the optical head 3.

For example, reading/writing can be performed even if the light beam is moved by about ±64 tracks under the control of the track actuator 34a, so it is checked whether ΔP is within this range.

If ΔP is within this lens seek range, the MPU 8 gives a control signal for a movement amount of 62 minutes to the track servo control circuit 6, drives the track actuator 34a, and tracks the light beam to the target track by moving the lens 34. Jump to move.

Then, return to step ■.

(2) On the other hand, if it is determined in step O that the difference ΔP is not within the lens seek range, the MPU 8 calculates the number of moving steps A of the step motor 1.

For example, if you move 20 trunks per step,
By dividing the difference ΔP by "20", the number of movement steps A can be obtained.

Next, the MPU 8 checks whether the stepper seek count value C, which indicates the number of times the step motor 1 has performed a seek operation in response to one seek command from a higher level, is rOJ.

If it is not C-0, the seek operation of the step motor 1 has already been executed in response to one seek command, so the number of moving steps A is compared with the predetermined number of steps that are considered to be missteps. .

If it is ARK, the MPU 8 does not regard it as a misstep and does not change the step rate.

Conversely, if A>K, the MPU 8 considers it to be a miss step, updates the step rate down count S to S+1, and decreases the step rate by one step.

■ In step ■, C=0 or A≦K or number of downs S
After updating, the MPU 8 executes coarse seek.

First, the MPU 8 turns off the track servo of the track servo circuit 6 and stops the track following operation of the light beam.

Next, the MPU 8 drives and controls the step motor 1 with a variable step rate, as will be described in detail in FIG.

Thereafter, the MPU 8 turns on the track servo of the track servo circuit 6 to restart the track following operation of the light beam.

Then, the stepper seek count value C is updated to C+1, and the process returns to step (2).

■ In this way, in step ■, the difference △P
If the MPU 8 determines -O, the light beam has been positioned on the target track, so the track access process ends.

At this time, the step rate seek count value C is reset to the initial value "0", and the step rate down number S is saved.

Next, control of the step motor will be explained with reference to FIG.

(2) The MPU 8 sets the table pointer B to "1" when starting control of the step motor.

■ The MPU 8 stores the current stepper phase Y in the memory 8b,
Compare the stepper phase number M (M=8 for 1-2 phase excitation in Figure 4), and if it is Y-M, set the current stepper phase Y to the first "1".
If Y=M, the current stepper phase Y is updated to the next Y+1.

If the rotation direction is the opposite direction, as shown in parentheses, compare it with Y=1, and if Y=1, update it to Y=M, and if Y≠1, update it to Y-Y-1.

Then, the MPU 8 uses the current stepper phase Y as a parameter,
The drive pattern table 5 (Y) in the memory 8b is read and the drive pattern signal is loaded into the control register 5.

As a result, the A-phase and B-phase currents ia, i, and b flowing from the A-phase and B-phase drive circuits 4a and 4b to the step motor l change, and one step drive is performed.

(2) The MPU 8 indexes the step rate table T (B) using the table pointer B, reads out the corresponding excitation time T (B), loads the complementary value into the timer 8a, and starts the timer 8a.

When the timer 8a counts up the excitation time T (B), the MPU 8 determines that the excitation time has elapsed based on the count-up output.

■Next, the MPU 8 reads the step rate down number S from the memory 8b, further reads the step rate down time t from the memory 8b, and sets the excitation time T (S) for varying the step rate to T (S). - Calculated by tx3.

Then, the MPU 8 loads the complementary value into the timer 8a and starts the timer 8a.

The timer 8a issues a count-up signal to the MPU 8 to count the excitation time T(S).

(2) Next, the MPU 8 updates the step number A1 pointer B to select the excitation time T (B) according to the acceleration/deceleration curve.

Therefore, the MPU 8 compares the remaining step number A and the pointer B.

If A=B, the vehicle has started decelerating or is decelerating; if A#B, the vehicle is accelerating or at a constant speed.

If it is A#B, MPU8 next uses pointer B and table T.
Compare with the number of tables N in (B).

If B-N, pointer B is the last T of table T (B)
(N), which is the highest frequency, so pointer B is not updated.

If B≠N, B is updated to B+1 because acceleration is in progress.

(2) Next, the MPU 8 updates the remaining step number A to A-1.

Then, the pointer B and the remaining step number A are compared.

In case of BAA, since the value of pointer B has exceeded the number of remaining steps, it is updated to B-A to slow down, and B≦
If A, do not update B.

(2) On the other hand, if it is determined to be B-A in step (2), the remaining step number A is first updated to A-1, and the pointer B is updated to A.

Therefore, as the number of remaining steps A decreases, the pointer B decreases, and the selected excitation time of table T(B) advances in the T(1) direction, that is, in the decreasing direction.

■ After step ■ or ■, MPU 8 points to point B.
Check whether is rOJ, and if B≠0, return to step (■).

On the other hand, if it is B-0, the step motor 1 has been driven for the number of steps, so the control of the step motor 1 is ended.

In this way, by adding step ■ in Fig. 6 and adding processing to set S-3+1 when A>K in step ■ in Fig. 5, if there is a misstep, the excitation time will be set to the specified T. T (S) is added to (B), and the step rate is set lower than that of the memory 8b under the best conditions.

This is shown in FIG. 7. When S=O, that is, the step rate according to table T (B), the excitation time under the best conditions (maximum speed) T (1) as shown in FIG. 7 (A),
Excitation phase switching is performed at T (2)- and T (N).

On the other hand, if it is not 5-J-o, that is, if there is a misstep, the excitation time will be T(3)-tXs, as shown in FIG. 7(B), Tl)+T(S), T(2) +T (S
)..., and the step rate is lowered.

Since S increases every time there is a misstep, the step rate is lowered step by step, and driving is performed at the optimum step rate.

In other words, when the power is turned on, the step rate is driven at the highest speed, but when a misstep is detected, the step rate is reduced and this continues until there are no more missteps. The fastest step rate without any missteps is automatically set.

The step rate down count S is reset when the power is turned on, and the optimum step rate is set again depending on the subsequent situation.

In this way, without considering variations in device characteristics,
The step rate can be set to a high speed, improving access speed.

Furthermore, it is possible to prevent continuous missteps from occurring under extreme conditions.

Furthermore, in this example, the step rate table T (
B) can be done with one type, and T due to the change in step rate.
(S) is calculated, so memory 8
There is no need to use the extra capacity of b.

(d) Description of other embodiments In the above embodiments, only reducing the step rate was explained, but for example, the number of successful coarse seeks of a certain number of steps or more is counted, and the count value is calculated when a miss step is detected. is cleared and the count value exceeds a certain value, and by returning the step rate one step at a time toward the initial value, it is possible to always drive at a step rate suitable for the conditions.

Furthermore, in the case of convertible optical discs, the step rate down count S may be returned to the initial value or updated to (S-1) when replacing the disc cartridge.

Furthermore, T(B) and T by steps ■ and ■ in Figure 6
(S) is counted separately, but T (B) +
T (S) may be determined and timed by the timer 8a.

Furthermore, the following modifications are possible in the present invention.

In the above embodiment, 1-2 phase excitation of the 2-phase step motor was explained, but any n-phase step motor may be used, and the excitation method may also be l-phase excitation, 2-phase excitation, quarter step drive, or microstep drive. Well-known ones such as the above can be used.

For example, in the quarter step, the A phase current control signal 1
a 1% l a z, B phase current control signal zb,, l
It is only necessary to make it possible to select a medium current by the combination of (b), and thereby it is possible to move half the step of 1-2 phase excitation, and the overshoot can be made small.

Furthermore, although the step motor drive circuit has been described as a bipolar drive circuit, it may be of any other well-known type, for example, a unipolar drive circuit, and the trunk of the optical disk is not limited to a spiral shape but may also be concentric circles. The head 2 can also be of other configurations, and the step motor is not limited to a rotary type, but may also be of a linear type.

Furthermore, although the explanation has been given using an optical disk device as an example, it can also be applied to other moving mechanisms such as magneto-optical disk devices and magnetic disk devices, and checking the current position is not limited to reading track addresses.
Detection may be performed using a linear scale or an encoder.

For example, with magnetic disks, there is no lens seek, so
Except for step ① in the 5th section, if it is set to K-1, it can be applied as is.

Although the present invention has been described above using examples, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to drive the device at the highest step rate according to the mechanical characteristics of the device and the surrounding environment without any missteps, thereby eliminating the need for step motors! It can be driven at maximum speed without 11 (missteps) and contributes to shortening travel time.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a block diagram of a step motor drive circuit configured as shown in Fig. FIG. 5 is a track access processing flow diagram according to an embodiment of the present invention; FIG. 6 is a step motor control flow diagram according to an embodiment of the present invention; FIG. 7 is an illustration of a step motor drive table according to an embodiment of the present invention. It is an explanatory diagram of an example operation. In the figure, 1-step motor, 2-optical disk, 3-optical head, 8.-control unit.

Claims (1)

[Claims] 1) The control unit (8) controls excitation phase switching of the step motor (1) at a predetermined step rate so that the step motor (1)
In the step motor control method for driving the step motor (1) for a desired number of steps, the control unit (8) controls the step motor (1) after the drive.
Detect the current position of the step motor (1) based on the detected current position.
1. A method for controlling a step motor, comprising: determining the presence or absence of a misstep; and changing the step rate in accordance with the determination of the presence or absence of the misstep.