lesson

1. Industrial Actuators
Roselito E. Tolentino

2. Actuators
• A mechanical device that converts electrical
energy into other form of energy usually
motion.
• Types of Actuator:
– Electric motor actuator
– Hydraulic fluid actuator
– Pneumatic fluid actuator

3. ACTUATORS – Electric Motor
• Advantages
– Lower initial and operating cost than hydraulic
and pneumatic system
– Most accurate servo-type positioning and
velocity control can be achieved
– Clean – no oil leaks
• Disadvantages
– Less force capability vs. hydraulic system
– Little holding strength when stopped (might sag
if load is heavy; mechanical breaks are required)

4. ACTUATORS – Pneumatic System
• Advantages
– Quick response
– Lower initial and operating cost than a hydraulic
system
– Clean – no oil leaks
• Disadvantages
– Accurate positioning and velocity control are
impossible (requires mechanical stops)
– Weak force capability
– Not so much holding strength when stopped (might
sag with heavy loads)

5. ACTUATORS – Hydraulic System
• Advantages
– Greatest force capability (can handle heavy loads)
– Great holding strength when stopped ( will not sag)
– Accurate servo-type positioning and velocity control can be
achieved
– Intrinsically safe in flammable environments such as
painting
• Disadvantages
– High initial and operating costs
– Messy – tends to leak oil (even during periods when the
robot is not in motion)

6. Electric Motors
• Electric Motors or Motors convert electrical energy
to mechanical motion
• Motors are powered by a source of electricity –
either AC or DC.
• Principle of How Motors Work:
– Electrical current flowing in a loop of wire will produce
a magnetic field across the loop.
– When this loop is surrounded by the field of another
magnet, the loop will turn, producing a force (called
torque) that results in mechanical motion.

7. Electric Motor
• Mainly rotating but also linear ones are
available
• linear movement with gear or with real linear
motor

8. Types of Electric Motors
Electric Motors
DC Motors
Special Purpose
Motors
Permanent Magnet
DC (PMDC)
Series Motor
Shunt Motor
Compounded
Motor
Induction
Motor
Synchronous
Motor
AC Motors
Separately Excited
motor
Stepper motor
Brushless DC
motor
Hysteresis motor
Reluctance motor
Universal motor

9. DC MOTORS
• A rotary electrical machines that converts direct current
electrical energy into mechanical energy
• DC Electric Motors use Direct Current (DC) sources of electricity:
◦ Batteries
◦ DC Power supply
• simple, cheap, easy to control
• 1W - 1kW
• can be overloaded
• brushes wear
• limited overloading
on high speeds
video

10. DC-motor control
• To control the direction of rotation - H-
bridge
• To control the speed of rotation - PWM
• Torque is increased through gears

11. Operation with S1-S4 corresponding to the
diagram

12. Power Amplifier for DC Motor Control

13. Controlling DC Motor Speed
• We do not change the supplied voltage
• The most effective way to adjust the speed is
by using Pulse Width Modulation.
• Pulse-Width Ratio or Duty Cycle = ton / tperiod

14. Controlling DC Motor Speed
• This means that you pulse the motor on and off at varying rates, to simulate a
voltage.
• When the time that the voltage is high (the duty cycle) is half the total time in
question, the effective voltage is about half the total voltage.
• When the duty cycle is reduced to one quarter of the total time, the effective
voltage is about one quarter of the total voltage.
•

15. Example 1:
• If Speed, current and voltage applied to a
motor is proportional, In a pulse with period
of 500 Hz, how long must a pulse be high to
reduce the speed to 1/4?

16. SERVO MOTORS
• DC motors equipped with a servo mechanism
for precise control of angular position.
• The servo motors usually have a rotation limit
from 90° to 180°.
• Some servos also have rotation limit of 360° or
more. But servos do not rotate continually.
• Their rotation is restricted in between the
fixed angles.

17. Servo System
• Servo is mechanism based on feedback
control.
• The controlled quantity is mechanical.
• Refers to an error sensing feedback control
which is used to correct the performance of a
system

18. Servo Control of an Electrical Motor

19. Servo Motor

20. Servo Motors
• Servomotors usually have three cables: power, ground
and PWM signal
• Servo require a PWM signal with 50 Hz frequency
(20ms period)
• The pulse should be between 1.0ms and 2.0ms long
(this sets servo to its extreme left or right position
• Note:
– Servo speed cannot be set ( servo tries to get to new
position as fast as possible)
– Servo do not provide feedback to the external component

21. Servo Motors Pulse Angle Relation

22. Example1:
• What is the duty cycle of the pulse to be fed to
the servomotor to make it rotate from 0 to 30
degrees?

23. Example2:
• What is the angle of the servo motor if length
of the high pulse is 1.125 ms?

24. STEPPER MOTOR
• Stepper motors are another kind of motors
that do not require feedback
• A stepper motor can be incrementally driven,
one step at a time, forward or backward

25. Stepper Motor Characteristics
• Number of steps per revolution (e.g. 200 steps
per revolution = 1.8° per step)
• Max. number of steps per second (“stepping
rate” = max speed)
• Driving a stepper motor requires a 4 step
switching sequence for full-step mode
• Stepper motors can also be driven in 8 step
switching sequence for half-step mode (higher
resolution)

26. Stepper Motors Construction

27. Types of Stepper Motor
• Unipolar Stepper
Motor
• Bipolar Stepper
Motor

28. Stepping Sequences

29. Wave Drive Stepping Sequences
Step 1a 2a 1b 2b
1st
1 0 0 0
2nd
0 1 0 0
3rd
0 0 1 0
4th
0 0 0 1

30. Wave Drive Stepping Sequences
Step 1a 2a 1b 2b
1st
1 0 0 0
2nd
0 1 0 0
3rd
0 0 1 0
4th
0 0 0 1

31. High Torque Drive Stepping Sequences
Step 1a 2a 1b 2b
1st
1 0 0 1
2nd
1 1 0 0
3rd
0 1 1 0
4th
0 0 1 1

32. Half Step Drive Stepping
Sequences
Step 1a 2a 1b 2b
1st
1 0 0 1
2nd
1 0 0 0
3rd
1 1 0 0
4th
0 1 0 0
5th
0 1 1 0
6th
0 0 1 0
7th
0 0 1 1
8th
0 0 0 1

33. Controlling Stepper Motor Speed
• The speed of the stepper motor is
proportional to the speed of pulse signals
(pulse frequency).
video

34. Example1:
• How many steps are needed to rotate a
stepper motor with 200 steps per revolution
to 120 degrees?

35. Example2:
• How fast does a stepper motor (with step size
of 0.72degree per steps) rotates in RPM if it
will be supplied with a 1Khz pulse?

36. Linear Motor
• A linear motor is an electric motor that has
had its stator and rotor "unrolled" so that
instead of producing a torque (rotation)
• It produces a linear force along its length

37. Hannes Daepp
Basics of Linear Motors [1],[4]
I
• Analogous to Unrolled DC Motor
• Force (F) is generated
when the current (I)
(along vector L) and the
flux density (B) interact
• F = LI x B

38. Analysis of Linear Motors [1],[5]
• Analysis is similar to that of rotary machines
• Linear dimension and displacements replace
angular ones
• Forces replace torques
• Commutation cycle is distance between two
consecutive pole pairs instead of 360 degrees

39. Components of Linear Motors [2],[3]
• Forcer (Motor Coil)
– Windings (coils) provide current (I)
– Windings are encapsulated within core
material
– Mounting Plate on top
– Usually contains sensors (hall effect
and thermal)
• Magnet Rail
– Iron Plate / Base Plate
– Rare Earth Magnets of alternating polarity
provide flux (B)
– Single or double rail
F = lI x B

40. Applications[3],[5],[6]
• Small Linear Motors
– Packaging and Material Handling
– Automated Assembly
– Reciprocating compressors and
alternators
• Large Linear Induction Machines
(3 phase)
– Transportation
– Materials handling
– Extrusion presses
Video