JPH08149890A - Drive equipment for stepping motor - Google Patents

Abstract

PURPOSE: To make it possible to drive smoothly even though a low-cost DA converter having a small number of bits is used by using psendo sine wave waveform data divided in angle direction as drive waveform data stored in drive waveform data generator. CONSTITUTION: Stored drive waveform data are latched, latched data are DA converted, and psendo sine wave waveform data divided in angle direction are used as drive waveform data stored in a drive waveform data generator 2 in a drive equipment supplying data to a coil 10 of each phase. These data of the psendo sine wave are divided by 250 for example for the angle range of 0 to 2π (rad). As stated above, the data of the psendo sine wave to be stored in the drive waveform data generator 2 are divided in angle direction, so that motor rotation can be performed in fine steps. Thus, even though a low-cost DA converter 6 having a small bit number is used, smooth motor drive 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 stepping motor driving device which is inexpensive and enables smooth driving.

[0002]

2. Description of the Related Art As a method of driving a stepping motor (pulse motor) more smoothly, a method of supplying a pseudo sine wave current to a stator coil of the motor (this is generally called a microstep or ministep method). ). The closer the pseudo sine wave current flowing through the stator coil is to the sine wave, the smoother the drive can be obtained. When a stepping motor is used for stage control of an electron microscope or the like, in the case of high-magnification observation, the normal driving method (rectangular wave driving) causes the field of view to move stepwise, and the amount of movement per unit step is It is large and very uncomfortable for the observer. In such a case, the method of flowing a sine wave through the stator coil is advantageous.

[0003]

Various methods of supplying a sine wave current to the stator coil are conceivable. For example, when a DA converter is used, the obtained pseudo sine wave waveform is the same as that of the DA converter. The larger the number of bits, the closer the waveform becomes to a sine wave, and smoother driving becomes possible. However,
A DA converter having a large number of bits becomes expensive.

The present invention has been made in view of the above circumstances, and an object thereof is to realize a driving device of a stepping motor which can be smoothly driven even when an inexpensive DA converter having a small number of bits is used. It is in.

[0005]

A stepping motor driving device according to the present invention includes a driving waveform data generator in which driving waveform data of a stepping motor is stored, and a driving waveform data generator receiving a driving pulse. A stepping motor drive device comprising: means for generating and latching drive waveform data for each phase of a stepping motor; and means for simultaneously converting the latched data into a DA converter by a DA converter and supplying the data to the coils of each phase. , Drive waveform data stored in the drive waveform data generator,
It is characterized by using pseudo sine wave waveform data divided in the angular direction.

[0006]

The stepping motor drive device according to the present invention uses the pseudo sine wave waveform data divided in the angular direction as the drive waveform data stored in the drive waveform data generator to realize smooth motor rotation. .

[0007]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a driving device for a stepping motor according to an embodiment of the present invention. Reference numeral 1 is an up / down counter, and a drive pulse for driving a stepping motor is input to the counter 1. Reference numeral 2 is a drive waveform data generator that stores drive waveform data for driving the stepping motor, and is composed of a ROM. The value of the up / down counter 1 is input to the drive waveform data generator 2 to generate a lower address. As the number of bits of this address is larger, a pseudo sine wave closer to a sine wave can be obtained.

For example, when driving a five-phase stepping motor, the drive waveform requires five pieces of data having phase differences with each other. That is, five data having different phases by 2π / 5 must be generated for each drive pulse. In this embodiment, when a drive pulse is received, the drive waveform data generator 2 generates five pieces of data until the next drive pulse is received. A synchronous counter 3 is provided to generate the upper address of the drive waveform data generator 2. The synchronization counter 3 is initialized each time a drive pulse is received, and in synchronization with the oscillator 4, generates a high-order address of the drive waveform data generator 2.

Reference numeral 5 is a latch, and the latch 5 holds the drive waveform data of each phase at the same time when the upper address generated by the synchronous counter 3 changes. A DA converter 6 DA-converts the data held in the latch 5. Reference numeral 7 denotes a latch signal generator, which generates a latch signal for each phase at the same time when the upper address of the drive waveform data generator 2 changes. Further, the latch signal generator 7 outputs the latch signal of each phase and then simultaneously outputs the latch signal to the DA converter 6 for all the phases to simultaneously DA-convert the waveform data of each phase.

The output of the DA converter 6 is supplied to the comparator 8, and the output of the comparator 8 is supplied to the gate circuit 9. From this gate circuit 9, an exciting current is supplied to the coil 10 of the stepping motor. Comparator 8
Compares the output of the DA converter 6 with the current flowing through the motor coil 10 (the current value of the reference resistor 11 for detecting the motor current value), and performs chopping drive. The current detected by the reference resistor 11 is returned to the comparator 8 via the amplifier 12. This chopping drive is performed to control so that a current larger than the set current does not flow in the coil, and is performed simultaneously for all phases based on the signal from the chopping signal generator 13. A latch 5, a DA converter 6, a comparator 8, a gate circuit 9, a coil 10, a reference resistor 11,
The amplifier 12 part is actually provided for the number of motor phases. The operation of such a configuration will be described below.

First, in the case of performing sine wave drive, as shown in FIG.
When a drive pulse for driving the motor shown in is generated, the drive pulse is generated by the up / down counter 1
Is supplied to the synchronous counter 3. The synchronous counter 3 is initialized by this drive pulse as shown in FIG. The up / down counter 1 counts drive pulses, and the output value of the drive waveform of each phase is designated by this count value.

The synchronous counter 3 initialized by the supply of the drive pulse is the oscillator 6 shown in FIG.
2D is generated in synchronism with the sync pulse of FIG. At the same time as the change of the upper address generated by the synchronous counter 3, the latch signal of each phase is generated from the latch signal generator 4. With this latch signal, the waveform data from the drive waveform data generator 2 is latched in each latch 5.

FIG. 2 (e) shows the latch signals AE. The latch signal generator 4 outputs the latch signals (A to E) of the respective phases, and then simultaneously supplies the latch signals (F) to the DA converter 6 for all the phases, and outputs the waveform data latched by the latch 5 to the DA converter 6. At the same time, DA conversion is performed. For each phase, the DA-converted waveform data is supplied to the motor coil 10 via the comparator 8 and the gate circuit 9, and the stepping motor is driven. 2 (f) shows the latch signals (A to E).
Shows the data (A ′ to E ′) output from the drive waveform data generator 2 and latched by the latches of the respective phases.

Here, the current flowing through the motor coil 10 flows through the detection resistor 11, and the amount of the current is detected by the amplifier 13 which detects the voltage. The detected current amount is input to the comparator 8, and when it reaches a specified current, the gate circuit 9 is turned off and the motor current is cut off. as a result,
The output of the comparator changes again, the gate circuit 9 is turned on, and a current is passed through the motor coil 10. Thus, chopping drive is performed.

As described above, the waveform data of all phases of the motor are simultaneously supplied to the motor coil every time the drive pulse is supplied, so that the motor is smoothly driven. here,
Inside the drive waveform data generator 2, pseudo sine wave data for all phases are stored. The data of this pseudo sine wave is divided in the angular direction, and 0 to 2π (ra
The angle range of d) is divided into, for example, 250 (equivalent to 8 bits which is a multiple of 5). FIG. 3 shows the waveform of the pseudo-sinusoidal wave of the phase A divided in this angular direction. In this figure, the vertical axis is data (current) and the horizontal axis is address (angle).
Is. In this way, since the pseudo sine wave data stored in the drive waveform data generator 2 is divided in the angular direction, it is possible to rotate the motor in fine steps. The data from π to 2π are offset by MSB. The MSB is used as a signal that determines the direction of the current flowing through the motor coil.

As described above, according to the present invention, the pseudo sine wave data as the drive waveform data is divided in the angular direction, but this division is data having a narrower interval than the minimum resolution data of the DA converter used. Thus, the motor can be rotated at fine intervals even if a DA converter having a small number of bits is used. For example, 8-bit DA
When the data is divided into 250 in the data direction by using the converter, data that changes angularly at about 7.25 ° is obtained, and by using the 12-bit DA converter, 40 in the data direction is obtained.
When the data is divided into 90, data that changes every 1.79 ° is obtained, but the sine wave data is 0 to 2π (ra
For example, if (d) is divided into 250 (equivalent to 8 bits which is a multiple of 5), data that changes every 1.44 ° is obtained.

When the sine wave waveform is divided in the angular direction, there are many identical data near the maximum value of the data, but the amount of change in the data of the other phases at that time is large, so that the whole is smooth. The rotation of the motor can be realized. That is, in FIG. 3, the same value of 11 points or 10 points is obtained at the maximum value of the phase current shown by M in the data of the A phase, but at this time, the other phase (B
In ~ D), the change in the amount of current is large, resulting in smooth motor rotation.

[0018]

As described above, the driving apparatus for a stepping motor according to the present invention uses the pseudo sine wave waveform data divided in the angular direction as the drive waveform data stored in the drive waveform data generator. Therefore, even if an inexpensive DA converter with a small number of bits is used, it is possible to realize smooth driving of the motor.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a driving device for a stepping motor according to the present invention.

FIG. 2 is a time chart for explaining the operation of the embodiment of FIG.

FIG. 3 is a diagram showing a pseudo sine wave waveform divided in the angular direction.

[Explanation of symbols]

 1 Up-down counter 2 Drive waveform data generator 3 Synchronous counter 4 Oscillator 5 Latch 6 DA converter 7 Latch signal generator 8 Comparator 9 Gate circuit 10 Motor coil 11 Reference resistance 12 Amplifier 13 Chopping signal generator

Claims (1)

[Claims] 1. A drive waveform data generator in which drive waveform data of a stepping motor is stored, and a drive waveform is supplied from a drive waveform data generator to generate drive waveform data for each phase of the stepping motor and latch it. In the drive device of the stepping motor provided with means and DA converter for simultaneously converting the latched data by the DA converter and supplying the converted data to the coils of each phase, as the drive waveform data stored in the drive waveform data generator, A stepping motor drive device using pseudo sine wave waveform data divided in the angular direction.