JP2555591B2 - Driving method for pulse motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pulse motor driving method capable of correcting a positioning error due to residual magnetism in a pulse motor.

"Prior Art" Conventionally, microstep driving of a linear pulse motor is as follows.

That is, the linear pulse motor has two phases (A phase, B phase)
In the case of the system, the linear pulse motor is driven and controlled by subdividing one pitch by the number of divisions by giving the sine wave and cosine wave division while maintaining the winding current at the electrical angle of 90 °. For example, the exciting current of each phase of the linear pulse motor is set to 1 pitch (electrical angle 2π) 16
It is divided and the current of the A phase is reduced stepwise, while the current of the B phase is increased stepwise. As a result, the mover stops at a position proportional to the current of each phase,
In this case, move on the scale in 16 steps.

1 pitch in the above-mentioned micro step drive
FIG. 8 is a diagram showing how to give a two-phase current when divided into 16 steps.

[Problems to be Solved by the Invention] By the way, when the above-mentioned linear pulse motor is used for driving a magnetic head of a floppy disk drive, for example, a positioning accuracy on the order of microns is required. However, in the above-described conventional linear pulse motor, due to the remanence of the cores C and D, when the mover is reciprocated, a phenomenon occurs in which the stop position differs between going and returning, that is, hysteresis at the stop position occurs.

The reason for this will be described with reference to FIG. 6 for the case of one-phase excitation for simplicity.

The hysteresis at the stop position is because residual magnetism remains in the core C even when the current of the coil A is turned off. That is, the magnetic flux φr due to the residual magnetism causes an imbalance in the magnetic flux distribution between the magnetic pole on the mover side and the stator, which causes the stop position to differ between the going and returning. Assuming that the magnetic flux from the permanent magnet E between the magnetic pole P1 and the tooth is φp ₁ and that between the magnetic pole P3 and the tooth is φp ₂ , the magnetic flux φ between the magnetic pole P1 and the tooth is φ.
Is φr + φp ₁ and the magnetic flux φ between the magnetic pole P3 teeth is φr
A -Faipi _2, the amount corresponding to the difference between the number of magnetic fluxes mover receives a thrust in the arrow Y2 direction, by a distance corresponding to the thrust misalignment with respect to its rightful position when remanence is not present Occurs.

Similarly, from the direction opposite to the case where the mover I is above,
If it moves to the position shown in the figure, the residual magnetism exists in the pole of the non-excitation phase of the linear pulse motor in the same direction as the direction in which the non-excitation phase was excited immediately before the linear pulse motor stopped. The magnetic flux due to this residual magnetism causes an imbalance in the magnetic flux distribution between the magnetic poles on the mover side and the stator, and the magnetic head stops at a position different from the correct position to stop when no residual magnetic flux exists. The positional deviation in this case occurs in the opposite direction to the above positional deviation.

That is, the stop position differs by 2ΔX between going and returning.

As described above, in the conventional linear pulse motor, the stop position error due to the hysteresis always exists in the plus direction with respect to the traveling direction by several μm. Therefore, as in the case of the magnetic head drive in the floppy disk drive,
Care must be taken when using in places where high-precision positioning is required.

It should be noted that in order to eliminate the hysteresis, a magnetic material having a small residual magnetism, that is, a magnetic property having a small coercive force, may be used for the cores C and D, but this makes the material expensive and costly. However, it is impossible to completely eliminate the hysteresis. Also,
It may be possible to magnetically anneal the cores C and D, but this takes time.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to adjust a positioning error due to the above-mentioned hysteresis, particularly to the same stop position when reciprocating without changing the structure of the motor. An object of the present invention is to provide a driving method of a pulse motor that can reduce an error to an almost negligible level.

"Means for Solving Problems" The present invention provides a main winding and an auxiliary winding in each phase of a pulse motor, and when the exciting current flowing in the main winding of the same phase becomes zero, An exciting current having a polarity opposite to that of the exciting current flowing in the main winding immediately before is supplied to the auxiliary winding arranged in the same phase, and the auxiliary winding is supplied with the opposite exciting current. The above problem is solved by a method of driving a pulse motor, which is characterized in that the residual magnetism generated by the exciting current flowing in the main winding is demagnetized by the above method.

"Operation" When the main winding and auxiliary winding are placed in the same core and the exciting current flowing in each main winding becomes zero, what is the exciting current flowing in each main winding immediately before that? Excitation current of opposite polarity
The residual magnetism is demagnetized by controlling the current so that it flows through the auxiliary windings arranged on the same core as the main windings.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. In the present embodiment, the case where the linear pulse motor is driven by the microstep method in which the mechanical pitch is divided into 8 will be described.

FIG. 1 is a diagram showing a configuration of a linear pulse motor driven by a pulse motor driving method according to an embodiment of the present invention. FIG. 2 is a diagram showing the waveform of the current supplied to the exciting coil of the pulse motor, and FIG. 3 is a pulse motor drive circuit for supplying the current shown in FIG.

First, in FIG. 1, 1 is a first main winding for excitation, 2 is a second main winding for excitation, 1a is a first auxiliary winding corresponding to the first main winding 1, and 1a is a first auxiliary winding. It is a second auxiliary winding corresponding to the two main windings. Then, the first main winding 1 and the first auxiliary winding 1a are in the same core C, and the second main winding and the second auxiliary winding 2a are in the same core D in the same direction. It is arranged in a rolled state.

PM is a permanent magnet and is magnetized in the direction shown in the figure.

P ₁ , P ₂ , P ₃ , and P ₄ are magnetic poles on the mover side. Reference symbol S denotes a stator having teeth ...... on the upper surface formed at an equal pitch P.

Next, referring to FIG. In this figure, 3 is a counter. The counter is provided with a CW command pulse input terminal 3a and a CCW command pulse input terminal 3b, and a command pulse train signal for driving the linear pulse motor in the CW or CCW direction is input. Then, the counter 3 counts the input pulse train signal and creates eight kinds of address codes (A _{0 to} A ₇ ) that increase incrementally,
Output to bus B. A ROM 4 stores a data table TBL4 shown in FIG. This data table 4
Is the main winding 1 and auxiliary winding 1a of the linear pulse motor
The main winding current value information and the auxiliary winding current value information that determine the current waveforms IM and IS shown in FIGS. 2 (a), (b), and (c) to be supplied to the address A _{0 to} A ₇ Remembered in. The main winding current value information and the auxiliary winding current value information are current waveforms IM shown in FIGS. 2 (a), (b) and (c) for each π / 4 in electrical angle.
This is current value information obtained by quantizing IS and coding the quantized amplitude value. The auxiliary winding current value is a value determined for the following reason.

That is, the auxiliary winding arranged on the same core as the main winding 1.
Reference numeral 1a is a coil for demagnetizing the residual magnetism caused by the main winding 1. Therefore, the electrical angle position where the exciting current IM does not flow in the main winding 1, that is, c in FIG. 2 (a),
With g, it is possible to cancel the residual magnetism due to the main winding 1 by causing an appropriate magnitude of exciting current in the opposite direction of the exciting current flowing in the main winding 1 immediately before that to flow in the auxiliary winding 1a. Therefore, at the electrical angle position c, an exciting current of −C ₂ may be applied to the auxiliary winding 1a as shown in FIG. At the point of g, the exciting current G ₂ in the opposite direction to the exciting current flowing in the main winding 1 immediately before is passed through the auxiliary winding 1a. Further, since the maximum exciting current flows through the main winding 1, that is, the phase is excited at the electrical angle positions a, e, i, the exciting current does not flow through the auxiliary winding 1a. That is, IS is "0". In the microstep drive of a linear pulse motor, sine wave currents IM = I ₀ cos θe and im = I ₀ sin θe with different 90 ° phases are supplied to each phase in the limit, and are supplied to each phase as necessary. By locking the instantaneous value of the exciting current at a certain electrical angle position, one mechanical pitch can be further subdivided to control the stop position. Therefore, the auxiliary winding 1a shown in FIG. Electrical angle positions a, c, as shown in (b)
It suffices to supply a sinusoidal excitation current IS = -i ₀ sin θe having an appropriate maximum amplitude value connecting e, g and i.

For the same reason, in order to cancel the residual magnetism due to the exciting current im supplied to the main winding 2, an appropriate value of exciting current is = i ₀ cos θe as shown in FIG. Just let it flow.

The maximum amplitude value i ₀ of the exciting current flowing through the auxiliary windings 1a and 2a or the product of the maximum amplitude value i ₀ and the number of coil turns i _0.
N (AT) needs to be adjusted in advance depending on the material of the core.

Now, return to FIG. A D / A converter 5 converts the main winding current value information read from the data table TBL4 into analog information. The converted analog information is power-amplified by the amplifier 6 and supplied to the first main winding 1. On the other hand, the auxiliary winding current value information read from the data table TBL4 according to the CW and CCW command signals is converted into analog information by the D / A converter 7, and the analog information is power-amplified by the amplifier 8. It is supplied to the first auxiliary winding 1a.

A ROM 9 stores a data table TBL9 shown in FIG. This data table TBL9 is to be supplied to the second main winding 2 and the auxiliary winding 2a of the linear pulse motor, the current waveforms shown in (a), (b) and (c) of FIG.
Main winding current value information and auxiliary winding current value information that determine im and is are stored in addresses A _{0 to} A ₇ . The main winding current value information and the auxiliary winding current value information are coded by quantizing the current waveforms im and is shown in FIGS. 2 (a), (b) and (c) for each electrical angle π / 4. This is current value information.

A D / A converter 12 converts the main winding current value information read from the data table TBL9 into analog information.
The converted analog information is power-amplified by the amplifier 11 and supplied to the second main winding 2. Meanwhile, data table TBL9
The read out auxiliary winding current value information is converted into analog information by the D / A converter 12. Further, the analog information is power-amplified by the amplifier 13 and supplied to the second auxiliary winding 2a.

 Next, the operation of the embodiment will be described.

Now, eight pulses are input to the CW command pulse input terminal 3a. The counter 3 continuously outputs address data that incrementally increases in response to the input eight pulses. This address data is commonly applied to the address input terminals (not shown) of ROM4 and ROM9. ROM
4. CW command signal is input to ROM9. For this reason,
From the data table TBL4, the current value information to be supplied to the first main winding 1 and the current value information to be supplied to the first auxiliary winding 1a are consecutive, and are sequentially read from the area corresponding to the address A _0. On the other hand, from the data table TBL9, the current value information to be supplied to the second main winding 2 and the second auxiliary winding 2a
The current value information to be supplied to is continuously read out sequentially from the area corresponding to the address A ₀ .

Therefore, in the electrical angle of 0 to π / 4, that is, in the range of electrical angle positions a to b in FIG.
The exciting current corresponding to A ₁ is supplied to the auxiliary winding 1a by “0”, the main winding 2 by “0”, and the auxiliary winding 2a by the exciting current of A ₂ . Thereafter, each current value information is similarly read out. Counter 3 receives address data A ₀ until a stop command is input.
~ A ₇ is repeatedly output, so after all, (a) in Fig. 2,
Excitation currents IM, IS, im and is as shown in (b) are supplied to the first and second main windings 1 and 2 and the auxiliary windings 1a and 2a.

Therefore, as shown in the hysteresis curve in FIG. 7, the residual magnetic flux φr or −φr is canceled by the exciting current −Is or + Is flowing in the auxiliary winding and becomes zero. Therefore, even when the linear pulse motor is driven in microsteps. ,
There is no imbalance in the magnetic flux distribution between the magnetic poles of the mover and the stator, and the deviation of the stop position caused by this imbalance is corrected.

[Advantages of the Invention] As described above, according to the present invention, it is possible to reduce the error in the same stop position that occurs when the pulse motor is driven, especially when the pulse motor is reciprocated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a linear pulse motor for realizing a pulse motor driving method according to the present invention, and FIG.
FIG. 3 is a diagram showing an exciting current for exciting coils of respective phases in the same linear pulse motor, and FIG. 3 shows a configuration of a linear pulse motor driving circuit for realizing a pulse motor driving method according to the present invention. Figures, 4 and 5
Data tables TBL4, TBL9 stored in ROM4, ROM9
FIG. 6 is a diagram showing hysteresis at a stop position in a conventional linear pulse motor, FIG. 7 is a history curve diagram showing residual magnetic flux that causes hysteresis at the stop position, and FIG. 8 is a microstep drive. FIG. 6 is a waveform diagram of an exciting current when performing 1 ... first main winding, 1a ... first auxiliary winding, 2 ... second main winding, 2a ... second auxiliary winding, C, D ... core,
Pole of P ₁ to P ₄ moving element side, S ...... stator teeth of ~ ...... stator side, 3 ...... counter, 4,9 ...... ROM, 5,7,10,12
…… D / A converter, 6,8,11,13 …… Amplifier.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP 56-10099 (JP, A) JP 59-21300 (JP, A) JP 51-13911 (JP, A) JP 61- 189196 (JP, A) JP 62-296798 (JP, A) JP 58-207896 (JP, A) Actually opened 59-126581 (JP, U) Actually opened 61-13576 (JP, U) Actual development Sho 50-18910 (JP, U)

Claims (1)

(57) [Claims] 1. An exciting current flowing in the main winding immediately before an exciting current flowing in the main winding is zero when an auxiliary winding is arranged together with the main winding in each phase of the pulse motor. An exciting current having a polarity opposite to that of the main winding is supplied to the auxiliary winding arranged in the same phase as the main winding to demagnetize the residual magnetism generated by the exciting current flowing in the main winding. Driving method of pulse motor.