ELECTRICAL ACTUATORS
Josep Amat and Alícia Casals
Automatic Control and Computer Engineering Department
ACTUATORS
1 – Pneumatic actuators
Cylinders
Motors
2 – Hydraulic actuadors
Cylinders
Motors
3 – Electrical actuators
D.C. motors.
A.C. motors
Steeper motors.
D.C. Motors.
F
Force.
H
I
Motor
D.C. Motors.
Motor torque
with a one turn
coil
Motor torque
with two turns
coil
Brushes
Motor torque
with multiple
turns coil
Casing
Stator
Stator
Rotor
Rotor
D.C. Motors.
Stator
Stator
(Inductor)
Rotor
(Induced)
Serial excitation
Parallel excitation
D.C. Motors.
V = I· (Re + Rr) + Vcem
I
Stator
T = KI· I ·FI
V
Vcem = Kv· w
T
Tr
V1
w
v2
wO
,
Serial excitation
wO
D.C. Motors.
V = I· (Re + Rr) + Vcem
I
Stator
T = KI· I ·Fo
V
Vcem = Kv· w
T
V1
V2
Permanent magnet
dc motor
Tr
w
wO
D.C. Motors.
Control techniques
PWM
A.C. Motors.
50 Hz.
 3.000 r.p.m.
50 Hz. = 50 r.p.s x 60 = 3.000 r.p.m.
Triphasic voltage produces a rotator magnetic field
that steers the rotor, if it is a magnet
A.C. Motors.
ac
F0 = 50 Hz.
The permanent magnet triphasic motor has a
constant speed. Synchronic motor
A.C. Motors.
Control techniques
ac/dc
dc/ac
f
The speed of a triphasic motor with permanent magnet
rotor can be controlled by varying the frequency of the
feeding signals.
A.C. Motors.
+V
0V
AB
A
B
Control technique: using a dc / ac converter
Electrical Actuators
DC Motors.
AC Motors.
Stepper Motors
Synchronous
Asynchronous
(Induction)
U
V
W
V
V
S
N
U
U
W
W
Synchronous A.C. Motor
the rotor is a permanent
magnet
i
Induction motor
(asynchronous), the rotor is
composed of one or more
windings in short-circuit
Rotor of an asyncronous a.c.
motor (Rotor as squirrel cage)
A.C. Motor.
D.C. Motor.
(Synchronous)
T
T
Tr
v2
V1
w1
A
B
wO
f1
f1
w
w1
Tr
w
A.C. Motor.
D.C. Motor.
(Synchronous)
T
T
Tr
V2
V1
w1
U
V
Tr
wO
W
w
w2 w0
w
f0 = 50 Hz.
Stepper Motors
S
S
S
S
N
S
S
S
S
S
N
N
N
N
N
S
N
N
N
N
Control of the position of the rotor in a stepper
motor using multiple pole pairs
Stepper Motors
N
S
S
S
N
S
S
S
N
S
N
S
N
N
N
S
N
N
S
N
Reduction of the number of pole pairs to a minimum,
groups of three that share the same coils:
Three phases stepper motor
Stepper Motors
N
S
S
N
S
S
N
S
S
N
N
S
N
N
S
N
N
S
N
S
S
N
S
S
N
S
S
Stepper motor control in three phases
N
N
S
N
N
S
N
N
S
Stepper motors.
0
N S N S N S N S N S N S N S N S N S N
0
N S N S N S N S N S N S N S N S N S N
0
N S N S N S N S N S N S N S N S N S N
1
S N S N S N S N S N S N S N S N S N S
1
N S N S N S N S N S N S N S N S N S N
1
S N S N S N S N S N S N S N S N S N S
1
0
S N S N S N S N S N S N S N S N S N S
S N S N S N S N S N S N S N S N S N S
Control of a two bodies stepper motor of two phases
Internal structure of a two bodies stepper motor, of two phases
Stepper Motors.
Control techniques of a two phases stepper motor