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Número de pieza | AN1115 | |
Descripción | ST52X301 FOR STEPPER MOTORS FUZZY CONTROL | |
Fabricantes | ST Microelectronics | |
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® 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
1/16
1 page Figure 5
ST52x301 FOR STEPPER MOTORS FUZZY CONTROL
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® 5/16
5 Page ST52x301 FOR STEPPER MOTORS FUZZY CONTROL
Three “start” blocks allow ADC, Timer and Triac peripheral to work. After that, a software loop form the
main routine. In this loop, ST52x301 waits for an interrupt (Timer or Triac INT) and an INT coming from
the program counter goes ahead to the “Speed” and “Torque” blocks.
Figure 12
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In these blocks Timer and Triac counter will be refreshed with the new value.
The main point of the software program is the INT subroutines. The following figure shows the phase ge-
neration by means of interrupt routines.
In the Timer Interrupt sub-routine, the first block switches phases among three different variables’ va-
lues. The variable “phase” changes among “1”, “2”, “4”. These values will be sent to the parallel port.
With Timer Prescaler settings, a switch occurs about one hundrend milliseconds. The Parallel port will
produce three sequential square waves on P0, P1, P2 pins.
In the Triac Interrupt sub-routine, a flag switches on each coming INT, between set and reset of PWM
out. The Triac Interrupts routine is executed about every 150 µs.
RESULTS AND CONCLUSION
By using ST52x301 Fuzzy Controller it is easy to implement motor driving by using few components.
Presented stepper motor control is good compromise between system costs and motor performances.
The graphical programming environment reduces the development time also for not expert program-
mers.
This application note was intended to show how easy is the use of ST52x301 as Controller in the servo-
drives. A lot of improvement could be done in the presented control by changing the software and fuzzy
algorithm.
® 11/16
11 Page |
Páginas | Total 16 Páginas | |
PDF Descargar | [ Datasheet AN1115.PDF ] |
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