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PDF AN1113 Data sheet ( Hoja de datos )
| Número de pieza | AN1113 | |
| Descripción | BRUSHLESS MOTOR FUZZY CONTROL | |
| Fabricantes | ST Microelectronics | |
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AN1113
APPLICATION NOTE
Brushless Motor Fuzzy Control by using ST52x301
Authors: G. Grasso, M. Di Guardo
INTRODUCTION
Brushless DC motors (BLDC) are becoming widely used in the field of control motors. These kind of syn-
chronous motors are used as servo drives in applications such as computer peripherals equipment, ro-
botics, and as adjustable-speed drives in load-proportional capacity-modulated heat pumps, large fans ,
compressors and so on.
Brushless DC motors are referred to by many aliases as brushless permanent magnet, permanent ma-
gnet AC motors, permanent magnet synchronous motors, etc. The confusion arises because a brush-
less motor does not directly operate off a dc voltage source. It is generally driven (supplied) from an in-
verter which converts a constant voltage to a 3-phase voltage with a frequency corresponding
instantaneously to the rotor speed.
One of the advantages of BLDC motor is the sparks absence. The brushes of a DC motor have several
problems as regards to brushes’ life and dust residues, maximum speed and electrical noise. BLDC mo-
tors are potentially cleaner, faster, more efficient, less noisy and more reliable. However, BLDC motors
require a more complex electronic control.
This application note will show how this complexity can be reduced by using ST52x301 Fuzzy controller.
AN OUTLINE OF BRUSHLESS MOTORS
The Brushless motor has the physical appearance of a 3-phase permanent magnet synchronous machi-
ne.
The brushes and commutator have been eliminated and the windings are connected to the control elec-
tronics. Electronics replaces the function of the commutator and energizes the proper winding. The ener-
gized stator winding leads the rotor magnet and switches just as the rotor aligns with the stator.
In synchronous motor drives, the stator is supplied with a set of balanced three-phase currents, whose
frequency is f.
If p is the number of the poles in the motor, then:
f
=
p
4π
ωs
(1)
where ωs (rad/s) is the flux synchronous speed or, that is the same, the rotor speed. This equation links
the rotor speed to the phases switching frequency of the electronic drive.
The above currents produce a constant amplitude flux φs in the air gap, which rotates at the synchro-
nous speed ωs. Since the flux amplitude is proportional to the current amplitude, it is enough to manage
winding current level to control the rotor torque.
From Brushless theory [3-4] it is possible to demonstrate that
Tem =Kt Φf Iph sin (δ)(2)
where kt is a constant, φf is the field-flux, δ is called torque angle. δ represents the angle between the
phase linked flux φfph1 and the relative stator current Iph1.
January 1999
1/18
1 page  
Brushless Motor Fuzzy Control by using ST52x301
"Ref" value from AD Channel0 and the instantaneous Hall signal period by means of a digital port. A
software task performs the "error" calculation
error = VREF − speed.
The variable "Error" also forms the Fuzzy Input for the "Fuzzy Controller" block. A Fuzzy algorithm uses
three rules to compute the fuzzy-out, achieving an incremental variable to drive the inverter in real-time
mode.
This incremental method allows to manage the speed in a closed loop real-time control, since software
task time is very short.
The first rule is fully activated when "error" value is "neg", i.e. when Vref <<speed. This implies that the
actual speed of the shaft is higher than "Ref". Then the action to carry out is to reduce the phase current
Figure 6. Fuzzy algorithm
I. To achieve this, it is necessary to decrease the PWM duty-cycle. The displayed value "-10" is a good
compromise between system stability and step response of the system. This value was assigned after
some trials by using only human reasoning. Instead, If the duty step is higher, for example "-20", the sy-
stem will sooner reach the "Speed_Ref" but the overshoot in a step response could lead to instability.
The above explanation is similar for the other rules.
The implemented 3-rules fuzzy algorithm is the simplest way to control the speed. A more accurate con-
trol could be done by using first derivative of the speed to improve the action strenght by means of other
rules.
HARDWARE DESCRIPTION
® 5/18
5 Page 
Figure 13. Dynamical performances
Brushless Motor Fuzzy Control by using ST52x301
Speed_Ref
2ω
Motor Speed
ω
Tr = 150 ms
REFERENCES
[1] Paul C. Krause "Analysis of Electric Machinery" - McGraw-Hill
[2] "Power Products- Application Manual", STMicroelectronics
[3] Mohan, Undeland, Robbins "Power Electronics: Converters, Applications and Design"
John Wiley & Sons
[4] Yasuhiko Dote, Sakan Kinoshita "Brushless Servomotors - Fundamentals and Applications" Oxford
Science Publications
[5] FUZZYSTUDIO™ 3.0 - User Manual, STMicroelectronics, 1998
® 11/18
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet AN1113.PDF ] | |
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