JPH01177899A - Drive system of stepping motor - Google Patents

Abstract

PURPOSE:To drive a stepping motor, which is hardly vibrated, by passing a target position command through a digital filter and preparing a stopping position command damping the vibrations of the stepping motor. CONSTITUTION:A digital filter 1 outputs a value acquired by filtering a target position command (r) to ROMs 2a, 2b for a fine-feed circuit 5 as the stopping position command (u) of a two-phase linear stepping motor 4 at every previously set sampling time. The values ia, ib of phase currents are output respectively to amplifiers 3a, 3b from the ROMs 2a, 2b. The amplifiers 3a and 3b receive the values ia, ib of currents and make currents flow through each phase of the two-phase linear stepping motor 4 and drive the motor, and the motor is made to reach a stepping-motor position (x).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a step motor drive system, and particularly to open loop control of a step motor, such as feeding control of a magnetic head in a floppy disk device.

[Conventional technology]

A step motor is a motor that rotates (or moves) by a fixed angle (or distance) each time an input pulse is applied, and has been widely used as a drive unit for positioning devices because it can simplify the servo mechanism. For example, N.C.
In machine tools, it is used as a table drive actuator for positioning the X-Y table, in magnetic disk devices such as floppy disk drives, it is used as a magnetic head drive actuator to position the magnetic head on the data track, and in printer equipment, it is used as a carriage drive actuator to position the print head. It's being used.

As an example of a step motor drive method, taking as an example a bipolar drive of a two-phase linear step motor, the combination of the directions of the currents applied to each phase, that is,
A method is used in which each phase is excited by a combination of four types of current directions: positive/positive, positive/negative, negative/negative, and negative/positive.

[Problem that the invention seeks to solve]

The motion of the step motor when using this drive method is
It is expressed as a spring-mass system in the following equation (1).

Here, M is the mass of the movable part of the step motor, 8 is the positional deviation between the position of the linear step motor and the stop position, μ is the viscous resistance coefficient, and k is a constant determined from the thrust generated by the linear step motor.

Therefore, as can be seen from equation (1), with the drive method described above, if the viscous drag coefficient is small or the frictional force is small, the step motor will not easily converge to the target stop position and will continue to vibrate. However, the problem is that it takes a long time to settle.

SUMMARY OF THE INVENTION An object of the present invention is to provide a step motor drive system that requires less vibration to drive the step motor at high speed and with high precision.

Means for Solving Problem C] The step motor driving method of the present invention receives a step motor target position command, transforms this target position command,
a digital filter that generates a stop position command; a storage element that receives the stop position command and outputs an excitation current value to each excitation phase of the step motor; and a memory element that outputs an excitation current value to each excitation phase of the step motor in accordance with the output value of the storage element. It is equipped with a micro-feeding circuit consisting of an amplifier for applying voltage.

[Effect]

By passing the target position command of the step motor through a digital filter, a stop position command that suppresses the vibration of the step motor is created, and this stop position command is given to the micro-feed circuit that performs micro-step drive to create a step with less vibration. Enables motor drive.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram illustrating a step motor drive system comprising a two-phase linear step motor, a microfeed circuit for microstep drive using a read-only memory, and a digital filter according to an embodiment of the present invention. ' The target position command r is a signal indicating the target position of the two-phase linear step motor 4. When a target position command r is given to the digital filter 1, the digital filter 1 outputs the target position command r at each preset sampling time.
2-phase linear step motor 4
The read-only memory (ROM) of the minute feed circuit 5 is used as the stop position command U of 2. ．． Output to 2k. Read-only memory 2. ．． 2b stores in advance the current values to be applied to each phase of the linear step motor 4 corresponding to the stop position of the two-phase linear step motor 4.

Read-only memory 2. ．． 2. When the stop position command U is given to the read-only memory 2. is the value i of the current applied to one phase of the two-phase linear step motor 4, and the read-only memory 2b is the value i of the current applied to the other phase of the two-phase linear step motor 4.
P)3-. 3b, respectively. Amplifier 3. and 3
．． receives the current value f&Ab and flows a current to each phase of the two-phase linear step motor 4 to drive the motor and make the step motor reach the position X.

FIG. 2 is a diagram showing an example of the configuration of the digital filter 1 using a 2-conversion operator. +
a! In aZ2+ bIn bIn CI and d
l is a parameter of the digital filter 1 and is a real constant.

Also, z-1 is a time delay equal to the sampling time, and Zl+22 is a state variable of the digital filter. 7. 8. 9 indicates an addition element.

For example, when the natural frequency of the step motor 4 is 200 Hz and the sampling time is 100 μsec, each parameter of the digital filter 1 can be selected as follows. The natural frequency is a value determined from the slope of the stiffness curve of the step motor at the point where the stiffness curve crosses zero and the mass of the moving part of the step motor. Further, the characteristics of the digital filter having the following parameter values are set so as not to pass signals around 200 Hz.

a ++ =0.994274 a +z=8
．． 46646X10-'a,, = -108,29
4a,,=0.707929b,-4,47626x
lO-9bz =8.46646xlO-'C, --
Focusing on the time 3382, 12ct, =1.0kT, the digital filter 1 calculates the stop position command U(kT) according to the following algorithm. Here, T represents sanswange time.

zt((k+1)T)"aIl' 2+(kT)+a
+z' Kg (kT) +b, -r (kT) (
1) zg ((k+1)T) = all ' 2 + (kT)
+ azz 'zz(kT)+b!・r (kT)
(2) u(kT) = c+ + Zz(kT)
+ dl-r(kT) (3) However, ((k+1)
T) indicates the next sampling time after kT time.

Figure 3 shows (i) the target position command, (ii) the stop position command as the output of the digital filter, and (iii) the motor when using the above-mentioned step motor with a natural frequency of 200 Hz and the corresponding digital filter. When the target position command r shown in FIG. 3(i) is given to the digital filter 1 at time t0, which is a diagram showing the position, it is transformed and the stop position command U shown in FIG. 3(ii) is generated. . This stop position command U is input to the minute feed circuit 5, and the two-phase linear step motor 4 is moved as shown in FIG. 3 (iii).
The motor is driven to the position X with less vibration as shown in the figure.

FIG. 4 is a diagram showing the target position command, stop position command, and motor position when a so-called 3 m5ec seek operation used in a floppy disk device is performed for three tracks. The target position command is given at 1.7m5ecs, 4.7m5ec, and 7.7m5ec, and the stop position command changes accordingly. The timing at which the stop position command is output from the digital filter is every 100 μsec, as described above. Since the frequency component of the stop position command does not include a component near 200 Hz, the step motor reaches the target position with almost no vibration.

As described above, according to this embodiment, it is possible to drive a step motor with less vibration, and as a result, high-speed operation can be realized.

In this example, we have explained that the digital filter has characteristics that do not pass frequency components near the natural frequency of the step motor, but it is also possible to set other digital filters, such as those that have low-pass filter characteristics or those that have integral characteristics. It is also possible.

〔Effect of the invention〕

According to the present invention, a step motor target position command is passed through a digital filter to create a stop position command that suppresses vibration of the step motor, and this stop position command is given to a microfeed circuit that performs microstep drive. This makes it possible to drive a step motor with less vibration.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a step motor drive system comprising a two-phase linear step motor, a micro-feed circuit for micro-step drive using read-only memory, and a digital filter according to an embodiment of the present invention, and FIG. A diagram showing an example of the configuration of a digital filter using a z-conversion operator, FIG. 3 is a diagram showing the relationship between a target position command, a stop position command, and a motor position according to the present invention, and FIG. 4 is a diagram showing a floppy FIG. 3 is a diagram showing a target position command, a stop position command, and a motor position when a so-called 3 m5ec seek operation used in a disk device is performed for three tracks. 1...Digital filter 2-. 2b...Read-only memory 3, . 3b
...Amplifier 4...Two-phase linear step motor 5...
・Minute feed circuit? , 8.9... addition element aIl, a12*a21・a2'l+bhb2・CI−
dl...Digital filter parameter 1m+'b...Read-only memory output r...
...Target position command U...Stop position command X...Step motor position z -1...Time delay "l+2!"...Digital filter state variable,
- Immediately (i) (ii) Figure 3

Claims (1)

[Claims] (1) A digital filter that receives a step motor target position command, transforms the target position command, and generates a stop position command, and receives the stop position command and supplies excitation current to each excitation phase of the step motor. A method for driving a step motor using microstep drive, comprising a memory element that outputs a value and a micro-feed circuit that includes an amplifier that applies a current to the step motor in accordance with the output value of the memory element.