JPH0556696A - Pulse motor - Google Patents

Abstract

PURPOSE:To realize fine residual vibration suppression control by passing an output from an encoder, i.e., a position signal of a mover, through a differentiator to produce a speed signal which is then multiplied by a speed feedback gain through a multiplier and fed back to the drive signal for each phase coil. CONSTITUTION:Upon driving of a pulse motor 46, an encoder 41 detects displacement of a mover 42 to produce a position signal. Differentiators 44a, 44b, provided for respective phases, receive position signals from the encoder 41 and differentiate thus received position signals. Multipliers 45a, 45b, provided for respective phases, receive speed signals from the differentiators 44a, 44b and multiply them by a feedback gain to produce products which are then fed back to the driving signals for respective phase coils 49a, 49b. According to the invention, fine suppression control of residual vibration can be realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse motor for performing damping control, and more particularly to a pulse motor for suppressing residual vibration when stopped.

[0002]

2. Description of the Related Art A conventional pulse motor has an advantage that open loop control is possible and that a servo mechanism can be easily configured without using a detector such as an encoder, a potentiometer, or a tachometer. Has the drawback of lasting relatively long.

In order to solve this drawback, there have been the following conventional methods for suppressing residual vibration of a pulse motor.

(1) A counter electromotive force detection winding is added to the mover of the pulse motor, and speed feedback is performed based on the counter electromotive force signal detected by the counter electromotive force detection winding to perform vibration. There is a method to suppress it (Proceedings of the Autumn Meeting of the Precision Engineering Society of 1986, p.88, Development of a High-speed Positioning Device Applying a Linear Step Motor (2nd Report, Damping Control Using Back Electromotive Force) The University of Tokyo, Toshio Higuchi , Matsushita Electric Works Kaji Kawamura, Fujitsu Kawamura Hideyuki). (2) An encoder is added to the pulse motor, the position of the mover is detected by the encoder, high-resolution position information is obtained through an interpolating circuit, and this is sent to a microcontroller (CP).
This is a method of performing PID compensation by performing control calculation in (U) (Reference: 1987 IEEJ Rotating Machinery Study Group Material No. 25 p.
p. 17-25, Phase control method of step motor Tsukasa Yoshiura, Hiromi Onodera, Noriaki Wakabayashi). (3) This is a method of suppressing vibration by devising a switching pattern of the excitation phase, etc. (Sogi Ohki "Theory and Application of Smop Motors" Jikken Publishing Co., Ltd. (May 1, 1979)
Issued), pp. 78-81, "3-3-3, damping effect by drive system").

[0005]

However, the conventional residual vibration suppressing method for the pulse motor described above has the following problems. That is, in the method (1), the back electromotive force detection winding is separately required. The method (2) requires an interpolation circuit and a CPU for high-speed software operation. Further, in the above method (3), since the excitation phase switching pattern and the like are uniquely determined in advance, it is susceptible to load fluctuations and it is difficult to perform fine control.

An object of the present invention is to eliminate the need for a counter electromotive force detecting winding, an interpolating circuit and a CPU as in the prior art, yet to be less susceptible to load fluctuations when driving is stopped, and to suppress damping, especially residual vibration. It is an object of the present invention to provide a pulse motor capable of finely controlling the suppression.

[0007]

A pulse motor of the present invention has a mover having magnetic pole teeth and a stator provided facing the mover and having stators having magnetic pole teeth. In a pulse motor that operates a mover by supplying a drive signal, it has a pitch that is the same as the pitch of the magnetic pole teeth, detects the displacement of the mover, and outputs a position signal, and differentiates the position signal from the encoder. And a multiplier provided for each phase for multiplying the output of the differentiator by a feedback gain and feeding the output back to the drive signal of the coil for each phase. Is characterized by.

[0008]

In the pulse motor having the above structure, the encoder detects displacement of the mover and outputs a position signal when the pulse motor is driven. When the differentiator provided for each phase receives the position signal from the encoder, the differentiator differentiates and outputs the position signal. When the multiplier provided for each phase receives the output (speed signal) from the corresponding differentiator, the output (speed signal) is multiplied by the feedback gain to feed back the output to the drive signal of the coil of each phase. ..

This makes it possible to perform damping suppression control, particularly residual vibration suppression control, without using a conventional counter electromotive force winding, an interpolating circuit and a CPU, and being less susceptible to load fluctuations when driving is stopped. It can be done in great detail.

[0010]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 3 is a perspective view showing an embodiment of the linear pulse motor according to the present invention.

In the figure, in the flat plate linear pulse motor 1, the mover 3 is movable in the arrow direction via the ball 14 and the roller 15 supported by the retainer 5 on the stator 2. The stator 2 includes a yoke 11 and a coil 1.
2 and magnetic pole teeth 13 and fixed to the reinforcing plate 4. A V-shaped groove 19 is formed on the upper surface of the reinforcing plate 4, and the ball 14 supported by the retainer 5 is fitted therein. By inserting the ball 14 into the V-shaped groove 19, the moving direction of the retainer 5 with respect to the reinforcing plate 4 is defined. A V-shaped groove 18 is also formed on the lower surface of the mover 3, and the ball 14 of the retainer 5 fits into this V-shaped groove 18. This insertion defines the moving direction of the mover 3 with respect to the retainer 5.

From the above, the mover 3 has the V of the reinforcing plate 4.
It moves in a direction parallel to the groove 19. A mounting plate 6 is screwed to the reinforcing plate 4 and is mounted in a device such as a floppy disk drive via the mounting plate 6.

Reflective encoder (linear encoder) 2
0 is attached to the outside of the mover 3 of the linear pulse motor 1 in the moving direction, and detects the unevenness of the magnetic pole teeth 8 formed on the mover 3 by etching or the like. The magnetic pole teeth 8 formed on the mover 3 have peaks and valleys alternately arranged at a constant pitch. The reflective encoder 20 is composed of a light projecting unit including an LED and a laser light source, and a light receiving unit including a photodiode and a phototransistor. The reflective encoder 20 is also capable of transmitting position signals with a 90 ° phase shift.

The rotary pulse motor is also shown in FIG.
The present invention can be applied by adding a reflection type encoder (linear encoder) similarly to the above.

FIG. 4 is a perspective view showing another embodiment of the linear pulse motor according to the present invention. In FIG.
The difference is that an external linear encoder, here an optical encoder 31 is provided instead of the reflective encoder 20. Therefore, in the linear pulse motor 1'of FIG. 4, the same reference numerals are used for the same or corresponding parts as in FIG.

Here, the optical encoder 31 is attached to the mounting plate 6
And a scale portion 35 externally attached at a position facing the position detection portion 32 of the slider 33 as a mover and having a slit 34 having the same pitch as the magnetic pole teeth 8. To be done. The position detector 3
2 irradiates light to the slit part (the part where the slit 34 is formed) of the scale part 35 that moves together with the slider 33, detects the reflected light, detects the movement amount (displacement) of the slider 33, and outputs a position signal. To do.

FIG. 1 is a block diagram showing an embodiment of a linear pulse motor according to the present invention. In the figure, 41 is a linear encoder, 42 is a mover magnetic pole tooth 42a (see FIG. 3,
4 is a stator having a magnetic pole tooth 8 in FIG. 4) and a stator 43. The linear encoder 41 has a mover magnetic pole tooth 42.
The unevenness of a is detected, and according to the displacement x of the mover 42, 90
The two position signals e _A and e _B which are out of phase are output to differentiators 44a and 44b, respectively. Differentiator 44
a, 44b, respectively located signal e _A, a speed signal by differentiating the e _B vector e _A, the vector e _B multiplier 4
5a and 45b. The multipliers 45a and 45b multiply the velocity signals vector e _A and vector e _B by the velocity feedback gain G and output the result to the subtractors 46a and 46b.

The subtractors 46a and 46b subtract the output signals from the multipliers 45a and 45b from the position command value signal (current command value signal) from the controller 48 and output the subtracted signals to the current amplifiers 47a and 47b. Current amplifier 47a,
47b is a stator 43 of the linear pulse motor 40 according to the levels of the outputs from the subtractors 46a and 46b, respectively.
The currents I _A and I _B are supplied to the exciting coils 49a and 49b. The linear encoder 41 corresponds to the reflection type encoder of FIG. 3 and the optical encoder 31 of FIG.
Corresponds to the mover 3 in FIG. 3 and the slider 33 in FIG. 4, and the stator 43 corresponds to the stator 2 in FIGS. 3 and 4. As the linear pulse motor 40, the linear pulse motor 1 of FIG. 3 or the linear pulse motor 1 ′ of FIG. 4 is applied.

FIG. 2 is a block diagram showing an embodiment of a linear pulse motor according to the present invention. Since this figure corresponds to FIG. 1, in FIG. 2, the same reference numerals are used for the same or corresponding parts as in FIG.

In FIG. 2, the controller 48 fetches a command value given to the A and B phases by a position command to designate the stop position of the linear pulse motor 40 from the current table 51 stored in the built-in memory, and the subtractor 46a. , 46b
And outputs signals with a 90 ° phase shift.

[0021] Figures 5 and 6, the position signal e _A, e _B (the output of the linear encoder 41) and a speed signal vector e _A when the mover 42, respectively, of FIG 1 is displaced at a constant speed, vector e _B is a diagram showing a (differentiator 44a, the output of 44b).

The stable point at the time of A phase excitation is the displacement x of the mover 42.
= 0, and A-phase when the, B-phase thrust distribution F _A, respectively F _B, here _{F A = -Ksin (2πx / Pm} ) · I A F B = Kcos (2πx / Pm) · I B, K: thrust constant, Pm: motor magnetic pole tooth pitch,
x: where the displacement of the mover 42 is, the phase of the output of the linear encoder 41 is e _A = sin (2πx / Pe−π / 2 · Pe) = cos (2πx / Pe) e _B = cos (2πx / Pe + 2π / 2 · Pe) = sin (2πx / Pe) where Pe is the encoder pitch, and x is the displacement of the encoder, that is, the displacement of the mover.

Further, as shown in FIG. 3, the unevenness of the magnetic pole teeth 8 is directly detected by the reflective encoder 20, or, as shown in FIG. 4, the slit pitch of the scale portion 35 of the optical encoder 31 is set to the magnetic pole teeth 8 of the magnetic pole teeth 8. By making the pitch the same, in the present invention, Pm = Pe (= P).

Under the above conditions, the velocity feedback control is performed as shown by the thick line in FIG.
As will be described later, the same effect can be obtained by adding a mechanical viscous resistance coefficient to the conventional viscous resistance coefficient of the equation of motion of the linear pulse motor. Therefore, as can be seen from the step response waveform of FIG. 7, the damping when the linear pulse motor is stopped, that is, the residual vibration of the linear pulse motor can be suppressed with higher accuracy than in the conventional case. Note that FIG.
7A is a diagram showing a step response waveform, FIG. 7A shows a case of a conventional example in which velocity feedback control is not performed as in FIGS. 1 and 2, and FIG. 7B is a diagram of FIG. 1 and FIG. The case of the present invention in which the speed feedback control (damping control) is performed as described above is shown. In FIG. 7, the horizontal axis represents time and the vertical axis represents the displacement x of the mover. Further, by adjusting the speed feedback gain G, it is possible to easily adjust the magnitude of attenuation of the residual vibration of the linear pulse motor.

Regarding the principle of obtaining such an effect,
This will be described in detail below.

The equation of motion of the linear pulse motor is expressed by the following equation.

[Equation 1] Here, M: moving part mass D: viscous drag coefficient K:
Thrust constant x: displacement of the movable portion (displacement encoder) f: Load thrust Pm: magnetic pole tooth pitch I _A, I _B: phase current

Further, the encoder signal (position signal) e _A ,
e _B is expressed by the following equation.

[Equation 2] Where k: encoder amplitude Pe: encoder pitch

The vectors e _A and e _B which are velocity signals after passing the encoder signals e _A and e _B through a differentiator are as follows by differentiating with time.

[Equation 3]

_A value obtained by multiplying the vectors e _A and e _B by the velocity feedback gain G is negatively fed back to each phase current, and the exciting currents I _A (t) and I _B (t) are set as follows.

[Equation 4]

The exciting currents I _A (t) and I _B (t) are
Substituting into the above equation of motion (1) and setting Pm = Pe = P,

[Equation 5] Becomes Therefore,

[Equation 6] Becomes As can be seen from the two items on the left side of equation (2),
It can be seen that the same effect as adding mechanical viscous resistance can be obtained as compared with the equation (1), and the magnitude of damping can be easily adjusted by changing the velocity feedback gain G.

As can be seen from the above description, in the present invention, for example, the linear pulse motor shown in FIGS. 3 and 4 is further subjected to speed feedback control as shown in FIGS. The effect of is obtained. That is, (a) As can be seen from the two items on the left side of the equation (2),
The same effect as adding mechanical viscous resistance is obtained. (B) Also, the magnitude of attenuation of the residual vibration of the linear pulse motor can be easily adjusted by changing the speed feedback gain G. (C) From the above (a) and (b), it is possible to obtain a very good suppressing effect as shown in FIG. 7B against damping, particularly residual vibration, when the driving of the linear pulse motor is stopped. (D) Since it is not necessary to use the various residual vibration suppressing methods described in the conventional example, the conventional counter electromotive force winding, the interpolating circuit, and the CPU are unnecessary, and the load is reduced when the drive is stopped. It is less susceptible to fluctuations, and damping control, particularly residual vibration suppression control, can be finely performed.

The present invention is not limited to this embodiment,
Various applications and modifications are conceivable without departing from the scope of the present invention. For example, in FIG. 3, the reflective encoder 20
Although the magnetic pole teeth 8 of the mover 3 are detected by the present invention, the present invention is not limited to this.
0 may be provided on the mover 3 side to detect the magnetic pole teeth 18 of the stator 2. Further, the present invention can be widely applied to not only linear pulse motors but also pulse motors. In particular, the present invention is effective when applied to a pulse motor of a magnetic head feed mechanism for a magnetic disk device, a floppy disk device, a hard disk device, an optical disk device, and the like.

[0033]

As described above, according to the present invention, an encoder having the same pitch as the magnetic pole teeth is provided, the displacement of the mover is detected by the encoder, and the position signal output from the encoder is differentiated. Since the speed signal is passed through the converter, the speed signal is further multiplied by the speed feedback gain by the multiplier to be fed back to the drive signal of the coil of each phase, the following effects can be obtained. (1) Since the output signal of the encoder is used, the conventional counter electromotive force detection winding is unnecessary. (2) Since the output signal of the encoder is directly used in an analog manner, the conventional interpolation circuit becomes unnecessary. Further, since the differentiator can be realized by hardware, it is possible to eliminate the conventional CPU. (3) Since the speed signal which is the output of the differentiator is continuously fed back to the drive signal (current command value) of the coil of each phase, it is less affected by the load fluctuation, and by adjusting the speed feedback gain, The magnitude of attenuation of residual vibration of the pulse motor can be easily adjusted. Therefore, when the driving of the pulse motor is stopped, it is possible to perform the residual vibration suppression control of the pulse motor that is extremely finer than that in the conventional case.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a linear pulse motor according to the present invention.

FIG. 2 is a block diagram showing an embodiment of a linear pulse motor according to the present invention.

FIG. 3 is a perspective view showing an embodiment of a linear pulse motor according to the present invention.

FIG. 4 is a perspective view showing another embodiment of the linear pulse motor according to the present invention.

5 is a diagram showing position signals e _A and e _B when the mover 42 of FIG. 1 is displaced at a constant speed.

6 is a diagram showing a vector e _A and a vector e _B which are velocity signals when the mover 42 of FIG. 1 is displaced at a constant velocity.

FIG. 7 is a diagram showing a step response waveform.

[Explanation of symbols]

 1, 1'Linear pulse motor 2 Stator 3 Mover 8 Magnetic pole tooth 20 Reflective encoder 31 Optical encoder 32 Position detector 33 Slider 34 Slit 35 Scale part 40 Linear pulse motor 41 Linear encoder 42 Mover 42a Mover magnetic pole tooth 43 Stator 44a, 44b Differentiator 45a, 45b Multiplier 46a, 46b Subtractor 49a, 49b Excitation coil

Claims (1)

[Claims] 1. A mover having a magnetic pole tooth, and a stator provided facing the mover and having a coil and magnetic pole teeth, and supplying a drive signal to the coil of each phase to provide the mover. In the pulse motor for operating, the encoder that has the same pitch as the pitch of the magnetic pole teeth, detects the displacement of the mover, and outputs a position signal, and each phase that differentiates and outputs the position signal from the encoder. A differentiator provided for each, and a multiplier provided for each phase for multiplying the output of the differentiator by a feedback gain to feed back the output to the drive signal of the coil of each phase, Pulse motor to.