INTRODUCTION TO ACTUATOR

BY: Dr. S. Nagarajan

November, 2021

INTRODUCTION TO SENSOR AND ACTUATOR

ACTUATORS
•An actuator is a component of a machine that is responsible for
moving and controlling a mechanism or system, for example by
opening a valve.
In simple terms, it is a "mover".

•An actuator requires a control signal and a source of energy.

• The control signal is relatively low energy and may be

electric voltage or current, pneumatic or hydraulic pressure,
or even human power. (so an amplifier may be required to
provide sufficient power to drive the actuator)

• When it receives a control signal, an actuator responds by

converting the signal's energy into mechanical motion.
BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR
Normally, the actuators are used in conjunction with thepower
supplyand acoupling mechanismas shown in figure below.

► The power unit provides eitherAC or DCpower at the rated

voltage and current.
► The coupling mechanism acts as the interface between the
actuator and the physical system.
► Typical coupling mechanisms include rack and pinion, gear
drive, belt drive, lead screw and nut, piston and linkages.
BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR
Types of Actuators
1.Mechanical Actuators

2.Electromechanical actuators
) Electric motors

) DC servomotors

) AC motors

) Stepper motors

) Solenoids
3. Hydraulic actuators
) Use pressurized liquid as driving force
4.Pneumatic actuators
) Use compressed air as the driving force

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Mechanical Actuator:
•In mechanical actuators normally
a rotary motion is converted into linear motion to perform an
operation.
•Such actuator normally involves gears, rails, pulley,
chain, springs etc to operate.

A basic example of a mechanical actuator is

chain block hoisting –
in which mechanical motion of chain
over the sprocket is utilized
to lift a rated load.
Electromechanical
Actuators

► The most common electromechanical actuator is a motor

that converts electrical energy to mechanical motion.
► Motors are the principal means of converting electrical
energy into mechanical energy in industry.
► Broadly they can be classified as
DC motors,
AC motors,
Stepper motors and Servo motors.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Electrical Actuators
• The electrical energy is used to actuate a mechanical
system using magnetic field i.e. EMF
•Example: electrical motor operated valve and magnetic valve
actuator or solenoid valve.
►Electrical switches are the choice of actuators for most of the
on-off type control action.
►Switching devices such as diodes, transistors, triacs, MOSFET,
and relays accept a low energy level command signal from the
controller and switch on or off electrical devices such as motors,
valves, and heating elements.
►For example, a metal-oxide field-effect transistors (MOSFET) switch
is shown in figure below

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

DC MOTORS
►DC motors operate on DC voltage and varying the
voltage can easily control their speed.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Cont...
►They are widely used in applications ranging from
thousands of horsepower motors used in rolling mills to
fractional horsepower motors used in automobiles (starter
motors, fan motors, windshield wiper motors, etc.).
►Although they are costlier, they need DC power supply
and require more maintenance compared to AC motors

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

AC MOTORS
►AC motors are the most popular since they use standard AC
power, do not require brushes and commutator(electrical
switches used for reversing the current), and less expensive.
►AC motors can be further classified as the induction motors,
synchronous motors and universal motors according to their
physical construction.

►The induction motor is simple, rugged and maintenance free.

They are available in many sizes and shapes based on
number of phases used. For example,

) Three-phase induction motor is used in large-horsepower

applications, such as pump drives, steel mill drives...
) Single-phase induction motors are widely used in many household

appliances BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Cont...

►The synchronous motor is one of the most efficient

electrical motors in industry, so it is used in industry to reduce
the cost of electrical power.
►In addition, synchronous motors rotate at synchronous
speed, so they are also used in applications that require
synchronous operations.
►The universal motors operate with either AC or DC power
supply. They are normally used in fractional horsepower
application.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Stepper Motor and
Servomotor
Stepper motor

Servo motor

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

STEPPER MOTORS

►The stepper motor is a discrete (incremental) positioning device

that moves one step at a time for each pulse command input.

►Since they accept direct digital commands and produce a

mechanical motion, the stepper motors are used widely in
industrial control applications.

►They are mostly used in fractional horsepower applications.

►With the rapid progress in low cost and high frequency solid-state
drives, they are finding increased applications.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Cont...
►The winding -1 is between the top and bottom stator pole,
and the winding-2 is between the left and right motor poles.

►The rotor is a permanent magnet with six poles resulting in a

single step angle of 30.
Unipolar Stepper Motor

BY: MOTI T.FEYISA

►With appropriate excitation of winding-1, the top stator pole
becomes a north pole and the bottom stator pole becomes a south
pole. This attracts the rotor into the position as shown.
►Now if the winding-1 is de-energized and winding-2 is energized,
the rotor will turn 30.
►With appropriate choice of current flow through winding-2, the
rotor can be rotated either clockwise or counterclockwise.
►By exciting the two windings in sequence, the motor can be made
to rotate at a desired speed continuously.
Applications of stepper motors:
• Floppy disc head drives, Printer carriage drives
• Positioning of printer heads and pens in X-Y plotters
• NC and CNC machine tool slide drives
• Automatic teller machines(ATM), Camera iris control
mechanisms
• Recording heads in computer disc drives
• Paper feed motors inBY:typewriters
MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR
and printers.
Servo Motors
►A servomotor is a rotary actuator that allows for precise
control of angular position.
►Servo motors has an output shaft which can be positioned to
specific angular positions by sending the servo( a coded signal)
►As long as the coded signal exists on the input line, the servo
will maintain the angular position of the shaft.
►As the coded signal changes, the angular position of the shaft
changes
►Feedback causes the amplitude of the error signal to decrease,
slowing the speed at which the load is moving
►Servo systems are also classified according to their functions:
Position, Velocity, and
Acceleration.

Applications: Robotics, CNC machinery or

automated manufacturing .
BY: MOTI T.FEYISA
Electromagnetic Actuators
►The solenoid is the most common electromagnetic actuator.

►A DC solenoid actuator consists of a soft iron core enclosed

within a current carrying coil. When the coil is energized, a
magnetic field is established that provides the force to push or
pull the iron core.
►AC solenoid devices are also encountered, such as AC
excitation relay.

BY: MOTI T.FEYISA

Cont...
►A solenoid operated directional control valve is shown in figure
below.
►Normally, due to the spring force, the soft iron core is
pushed to the extreme left position as shown.
►When the solenoid is excited, the soft iron core will move to
the right extreme position thus providing the electromagnetic
actuation.
Solenoid operated directional control valve

BY: MOTI T.FEYISA

FLUID POWER SYSTEM
►Fluid power is the technology that deals with the generation ,
control and transmission of power-using pressurized fluids.
►Fluid power is the muscle that moves industry, because fluid
power is used to push, pull, regulate or drive virtually all the
machine of modern industry.
►Two types of fluid power:
►Hydraulic and
►pneumatic system.

►A fluid power system can be broken down into four main

divisions in an electrical system.
) Power sources (pump or air compressor)
) Fluid power line
) Control valves

) Actuators (rotating and non rotating cylinders)

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR
HYDRAULIC SYSTEM
►Hydraulic actuators offers a high power-to-weight ratio,
► large forces at low speeds both linear and rotary actuation.

►It is applicable for very large robots and civil service robots.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Components

► 1. Tank 2. Pump 3. Electric motor

► 4. Control valves 5. ACTUATORS 6. Piping and Hoses
BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR
Hydraulic Actuators

►Hydraulic actuators use pressurized oil that is incompressible.

They can produce very large forces coupled with large motion in a
cost-effective manner.
►Cylinders which are help full to convert fluid power to
mechanical power
►Hydraulic actuators are used at high pressure, produce large
force and precise movements
►Made from steel to with stand the force applied on it

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

 Types of Hydraulic Actuator (Cylinder)

Double Acting Cylinder Single Acting Cylinder

Double Rod Cylinder

BY: MOTI T.FEYISA

Telescopic Cylinders
INTRODUCTION TO SENSOR AND ACTUATOR
Applications of Hydraulic
Systems
► Heavy Plant Steel press
► Large-scale precision -motion
tables
► Mobile Systems
► Steering, brakes
► Propulsion and transmission
► Aerospace
► Aero on actuation in aircraft
► Fin actuation in missiles/rockets

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

PNEUMATIC
SYSTEMS
► Pneumatic systems are widely used in industrial automation
using pressurized air as a source of power to drive linear and
rotary cylinders controlled by solenoid valves.
► A pneumatic system carries power by employing
compressed gas, generally air, as a fluid for transmitting
energy from an energy-generating source to an energy-using
point to accomplish useful work.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Cont...

►Air is drawn from the atmosphere through an air filter and

raised to required pressure by an air compressor.
►As the pressure rises, the temperature also rises; hence, an
air cooler is provided to cool the air with some preliminary
treatment to remove the moisture.
►The treated pressurized air then needs to get stored to
maintain the pressure.
► With the storage reservoir, a pressure switch is fitted to start
and stop the electric motor when pressure falls and reaches
the required level, respectively.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Components

► Air Tank
► Air
compressor
► Electric motor
► Control valves
► ACTUATOR
► Air hoses

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Pneumatic Actuators
►Pneumatic actuators use air under pressure that is most
suitable for low to medium force, short stroke, and high speed
applications.

►Pneumatic actuators and motors do just the opposite.

►Theyextract energy from compressed air and convert into
mechanical energy to perform useful work.

►There are two types of actuators:

► 1. Linear actuators (Pneumatic cylinders)
►2.Rotary actuators (Air motors)

BY: MOTI T.FEYISA

Rotary Actuators
Linear Actuators
Advantages of Pneumatic

► Low inertia effect of pneumatic components due to

low density of air.
► Pneumatic Systems are light in weight.
► Operating elements are cheaper and easy to
operate,
► Power losses are less due to low viscosity of air,
► High output to weight ratio.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Disadvantages for Pneumatic
►Suitable only for low pressure and hence low force
applications,
►Compressed air actuators are economical up to 50 kN only.

►Generation of the compressed air is expensive compared to

electricity,
►Exhaust air noise is unpleasant and silencer has to be used.

►Rigidity of the system is poor,

►Weight to pressure ratio is large,

►Less precise. It is not possible to achieve uniform speed

due to compressible of air,
►Pneumatic systems is vulnerable to dirt and contamination

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Applications
►Pneumatic are good for straight movements, but, with
the right linkage can be used for rotation or other
movements.
►Manufacturing

) Robot grippers
) Movement of parts
) Assembly operations

►Medical Systems
) Drills/cutting tools
) Suction and clamping
►Robotics

) Animatronics
) Grippers
Characteristics of Actuators
►Depending upon the intended application of the robot the
major required actuator characteristics are:

►Actuator weight;
►Power-to-weight ratio;

►Operating pressure;

►Stiffness and compliance;

►Reduction gear.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Selection Criteria
►The selection of the proper actuator is more complicated than
selection of the sensors, primarily due to their effect on the
dynamic behavior of the overall system.
►Furthermore, the selection of the actuator dominates the power
needs and the coupling mechanisms of the entire system.
►The coupling mechanism can sometimes be completely avoided
if the actuator provides the output that can be directly interfaced to
the physical system.
►For example, choosing a linear motor in place of a rotary motor
can eliminate the need of a coupling mechanism to convert rotary
motion to linear motion.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Cont...
In general, the following performance parameters must be
addressed before choosing an actuator for a specific need:
►Continuous power output: The maximum force/torque
attainable continuously without exceeding the temperature
limits
►Range of motion: The range of linear/rotary motion

►Resolution: The minimum increment of force/torque attainable

►Accuracy: Linearity of the relationship between the input and

output Peak force/torque.
The force/torque at which the actuator stalls.
►Heat dissipation: Maximum wattage of heat dissipation in
continuous operation.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Cont...
►Speed characteristics: Force/torque versus speed
relationship.
►No load speed: Typical operating speed/velocity with no
external load.
►Frequency response: The range of frequency over which
the output follows the input faithfully, applicable to linear
actuators.
►Power requirement: Type of power (AC or DC), number of
phases, voltage level, and current capacity
►In addition to the above-referred criteria, many other factors
become important depending upon the type of power and the
coupling mechanism required.

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

MEMS and Microsystems
What Is MEMS?
MEMS = Micro Electro Mechanical System
•Any engineering system that performs electrical and mechanical
functions with components in micrometers is a MEMS.
(1µm = 1/10 of human hair)
•A MEMS (micro-electromechanical system) is a miniature
machine that has both mechanical and electronic components.

The core element in MEMS generally consists of two principle

components :

1. Sensing or actuating element and

2. Transduction unit
Microsystems = sensors + actuators+
BY: MOTI T.FEYISA
signal transduction
INTRODUCTION TO SENSOR AND ACTUATOR
Commercial MEMS and Microsystems
Products
Micro Sensors: Micro Actuators:
►Acoustic wave ►Grippers, tweezers and tongs
sensors ►Motors - linear and rotary
►Biomedical and
►Relays and switches
biosensors
►Valves and pumps
►Chemical sensors
►Optical equipment (switches,
►Optical sensors
lenses and mirrors, shutters,
►Pressure sensors phase modulators, filters,
►Stress sensors waveguide splitters, latching and
► Thermal sensors
fiber alignment mechanisms)

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

Micro sensors are built to sense the existence and the
intensity of certain physical, chemical or biological
quantities , such as temperature ,pressure, force ,sound,
light, nuclear radiation, magnetic flux and chemical
components.

The transduction unit converts the input power supply into

the form such as voltage for a transducer, which functions
as the actuating element.
MEMS as a Microsensor

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

MEMS as A Microactuator- Motor

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

An electrostatic driven micro motor produced by LIGA process.
(LIGA- German words – lithography, electroplating and
moulds)

All three components – the rotor (center gear),

the stator and the torque transmission gear are made of
nickel.
The toothed rotor’s dia is of 700 microns and the gear is 250
micron dia.
The gap between rotor and stator is 4 microns.

The height of the unit is 120 microns.

Components of Microsystems

A micro system is an engineering system that contains MEMS components

that are designed to perform specific engineering functions.

A micro system includes three major components - micro sensors,

actuators and a processing
BY: MOTIunit .
T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR
Micromechatronics Systems

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR

• Most microsystems are designed and constructed to
perform single functions.

•Incorporating signal processing and closed loop

feedback control systems in a microsystems makes the
integrated system as “intelligent” systems.
Application in Automotive
Principal areas of application of MEMS and
microsystems:

►Safety

►Engineand power train

►Comfort and convenience
►Vehicle diagnostics and health monitoring
►Telematics, e.g. GPS, etc

(5) Combustion sensor

(1) Manifold or Temperature manifold (6) Gasoline direct injection pressure
absolute pressure sensor sensor
(2) Exhaust gas differential pressure (7) Fuel tank evaporative fuel pressure
sensor sensor
(3) Fuel rail pressure sensor (8) Engine oil sensor
(4) Barometric absolute pressure (9) Transmission sensor
sensor (10)Tire pressure sensor
BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR
THANK YOU!

BY: MOTI T.FEYISA INTRODUCTION TO SENSOR AND ACTUATOR