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AN1115 PDF даташит

Спецификация AN1115 изготовлена ​​​​«ST Microelectronics» и имеет функцию, называемую «ST52X301 FOR STEPPER MOTORS FUZZY CONTROL».

Детали детали

Номер произв AN1115
Описание ST52X301 FOR STEPPER MOTORS FUZZY CONTROL
Производители ST Microelectronics
логотип ST Microelectronics логотип 

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AN1115 Даташит, Описание, Даташиты
AN1115
® APPLICATION NOTE
ST52x301 FOR STEPPER MOTORS FUZZY CONTROL
Authors: G. Grasso, M. Lo Presti
1. INTRODUCTION
This application note is intended to explain how to control a stepper motor by using ST52x301 Fuzzy
Microntroller.
Stepper Motors are well known in position controls field applications and are particularly used in Robo-
www.DataStihcese,t4CUo.cmomputer peripherals, Industrial servo quality drivers and so on. One of the main advantages of
stepper motors is the strong relation between electrical pulses and rotation discrete angle steps. This al-
lows to exactly know the shaft position of the motor without using a position sensor.
Depending on the building characteristics of the motor and its driving techniques, it is possible to have a
wide range of stepper motors. Generally speaking, permanent magnetic cores are referred to as Stepper
Motor while soft iron cores are referred to as Variable Reluctance Motors.
2. FUNCTIONAL DESCRIPTION
The Stepper Motor’s operating principle used in the current implementation, is described in fig. 1. A 12-
pole stator is energized by means of a 3-phase winding. Each coil is assembled in order to generate, in
the space, the same number of magnetic poles. The rotor consists in a permanent magnetic core sha-
ded in order to produce 8 magnetic poles.
The poles produced by the stator current force the rotor to move in order to be aligned to the rotor ma-
gnetic field. This implies an alignment of the rotor core’s nearest pole to the stator energized poles.
When the phase Φ1 is energized, the rotor pole P1 is aligned to the field. Then, if the phase Φ1 is de-
energized and Φ2 is energized, a new set of magnetic poles will be created in the stator. This new ma-
gnetic field will force the rotor to move in counterclockwise direction to align its poles to the field. This ac-
tion yields a shaft rotation of a step angle q.
Generally, for a q-phase motor with Nr rotor teeth, the following equation is given:
Then, in our application:
Step_angle
=
360°
qNr
15°=
360°
3x8
The spin direction can be controlled by a phase excitation sequence. Excitation sequence Φ1, Φ3 and
Φ2 will move the rotor clockwise.
From energy considerations, it can be shown that:
T=f(i, dL )
dθ
This general relation is true for any kind of stepper motor. For instance, the strong relation between T
and dL/dθ allows the Variable Reluctance motor to move.
January 1999
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AN1115 Даташит, Описание, Даташиты
AN1115 - APPLICATION NOTE
Figure 1
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3. DRIVING TOPOLOGY
A variety of configurations is possible to energize the winding phase in a better way, nevertheless, the
simplest driving topology will be investigated here.
Due to the internal connections of our motor, a unipolar driver is used. Fig.2 shows the basic topology
used to energize the three phases of the motor.
Figure 2
2/16
®









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AN1115 Даташит, Описание, Даташиты
ST52x301 FOR STEPPER MOTORS FUZZY CONTROL
Motor specifications impose a maximum voltage of 24V for each phase and a phase current of 0.5A
then, there are no problems to use Darlington BJT as switches.
When the phase Ph1 is energized (Q1 on), the voltage Vcc is applied to the phase coil; then the current
raises with a rise-time related to the inductance value L and to the back-EMF of the coil. Roughly, the
maximum value for the current is limited by a winding resistance unless the controller avoids the current
to go above a fixed level. To perform this current limitation it is possible to “sense” the current level in the
phase and reduce the applied voltage to the phase coil. A Pulse Width Modulation is the simplest way to
control the mean value of the applied voltage. Fig. 3 shows the basic principle of modulation.
Figure 3
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During the powering-time of each phase, ST52x301 can modulate Ton and Toff of the PWM signal in or-
der to increase or decrease the mean applied voltage.
As we will see later, the AND gates can be replaced by a software “AND” inside the main program of
ST52x301.
4. CURRENT CONTROL BY USING ST52X301 TRIAC-PERIPHERAL
ST52x301 provides up to 4 Analog inputs in the range between 0 and 2,5V with a conversion time of
33µs each.
Converted values are stored in 8-bit internal registers until the following conversion. Due to the input ran-
ge, ADC resolution is 10 mV. Choosing the appropriate value for Rsense it is possible to read all the
working current of each phase winding.
Moreover, ST52x301 provides a Triac-Driver peripheral to manage directly a Triac in several working
modes. For example, In PWM mode, the user only needs to fix the PWM frequency and the duty-cycle of
the wave. For instance, we can fix a constant PWM frequency according to the maximum switching fre-
quency of the Darlington in order to maximize switches efficiency. After that, we can control the duty-cy-
cle of the PWM wave to achieve the desidered voltage on the phase coil.
® 3/16










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