ACTUATORS

On receipt of the controller command(s) a relay

switch and /or correcting element or final control
element comes into action to implement the
decision of the controller.
Action like : opening of a door, closing of a door
,printing ,firing a bullet ,answering a question etc.
It can be implemented through any one or
combination of various mechanical, electrical,
hydraulic, pneumatic equipment & devices.
Types of Actuators :Mechanical, electrical,
hydraulic, and pneumatic actuators .
Electrical Actuating System
 Introduction
*Electrical actuators : Switches,
Contacts, Relays, Solid state device
switches, motors.
*Machines and systems involve
various types of movements: variety
of motors,
*Range: Smallest motors(watch) to
largest motors(Ship propulsion) .
 ELECTRICAL RELAYS, SOLENOIDS
• Switches :SPST ,SPDT ,DPDT
• Fuses :
• Magnetic Switches :
• Solenoids and Relays :Reed Relays
• Relay timers :
(i)On delay relay timer,
(ii)Off delay relay timer
Switches :SPST ,SPDT ,DPDT
On delay relay timer
 SOLID-STATE SWITCHES
Semiconductor devices such as:
• diodes,
• transistors,
• thyristors,
• DIACs, and
• TRIACs,
They can perform high-speed switching.
 ELECTRIC MOTORS
*An electric motor :An electromechanical
device.
*Converts electrical power into mechanical
power and offers rotary or converted linear
motion through available mechanical power.
*Classification: Type of electrical energy input,
construction, or application.
*It can run on DC, AC, and dual power supply,
that is, DC or/and AC supply.
*Power rating: Milli watts to millions of watts
 Types of DC Motors

DC Motors Types :
(i)Brushed DC Motors with Field
Windings
•Self-excited DC motors : Series,
shunt, compound
•Separately Excited DC motors
(ii) Brushless DC Motors
 Self-excited DC motors
• Field coil as well as armature windings are
excited by the same source.
 Separately -excited DC motors
Field coil and armature winding are excited by
separate sources.
•
 Brushless DC (BLDC) Motor
*The drawback of a brush-type motor is
eliminated by making an electronic
commutation process to output an AC
trapezoidal voltage signal.

• A BLDC motor is fed with a DC supply, like a

DC motor, behaves similar to a synchronous
motor.
 DC Servo Motor
• A DC servo motor: A precise position, speed, and
acceleration control.
• Components : Motors (DC or AC), gear train
feedback mechanisms, potentiometric position
control, and ICs for closed-loop control.
• DC servo motor has a fixed armature
voltage/current with a variable field current, fed
through a DC rectifier pulse known as pulse code
modulated (PCM) signal.
 Stepper Motor
*A stepper motor: Asynchronous motor to
output a mechanical discrete movement against
the supply of electrical pulses to its phase
windings.
*Rotor Movement: Function of frequency of the
electrical pulse applied as well as on the
sequence of application of the pulses.
*Total shaft movement and displacement:
Functions of duration of time.
Types of Stepper Motor Winding
 Step Implementation

Two sets of identical winding

Steps : 15 ,30 ,45,60 90 ….degrees
(above step angle are normal)
 AC Motors
* Runs at AC supply.
*Types: 1Ф type or 3Ф type.
*Types of Three-phase AC motors:
Synchronous motors and
Asynchronous/Induction motors (IMs).
*A synchronous motor : Always runs
at the same speed, called the
synchronous speed.
*A three-phase IM: Squirrel-cage type
or Slip-ring type
 Single Phase AC Motors
It is basically a two phase motor as its phase is split
 Universal Motors
Runs on DC as well as AC power supply used in house
hold .
 Application
• DC Shunt motor: lathe, pumps, fan, saw machine
• DC series : electric traction, high speed tools
• Compound motor: rolling mill, load with large
momentary torque
• Servo motor : robotics, CNC machinery
• Stepper motor: CNCs, computer control, precision
positioning, laser cutting, digital camera for auto
focusing ect.
• 3Ф IM : punches, shears, elevators, hoist
• Universal Motors : Food processor, hair dryers, fans,
pumps, vacuum cleaner
• 1Ф IM : household appliances, office machinery for
individual load, clocks, drills, pump and refrigerators
• (capacitor start and run) : belt drives, small conveyors,
blowers and refrigerators
 Mechanical Actuating System
Mechanisms : Devices considered as
motion converters. Eg. IC engine ( linear
reciprocating motor to rotary motion)
A combination of kinematic chains with at
least one chain fixed to a transit motion.
Types of Mechanisms
(a) simple (four links)
(b) Compound (more than four links)
Change of speed - gear

Force Amplification - Lever

Transfer of rotation
Timing Belt
about one axis to
rotation about another -
 rack and
pinion

belt and chain drive

Cam
 Motion of an object
Translational Rotational

Degrees of Freedom :
Number of degrees of freedom of a motion
=Number of components needed to produce
the motion

Kinematics is used for study of motion

without regard to force or energy
 Power flow in machine
•
 Mechanisms in Mechatronic
• Based on types of motion :
Serial combination
1. Rotary to rotary (R–R)
Parallel Combination
2. Rotary to translation (R–T) Hybrid Combination
3. Translation to rotary (T–R) Linear – screw drivers
4. Translation to translation (T–T) Belt-pulley
5. Helical to rotary (H–R)
6. Helical to translation (H–T) Non Linear –
7. Inversion of mechanism: Slider-crank mechanism
 Components of Mechanism
• Joints - link between 2 or more nodes to
generate relative motion
• Links – part of mechanism moving
relative to a rigid body for transmitting a
required force with or without negligible
deformation. Rigid link, Flexible link, Fluid
link.

Contains two
different elements of
two joints
 Kinematic Chains
• Four-bar Chains Crank, coupler
and lever / rocker

Used in automobiles such as motor car engine,

bikes and bicycle
 Gears
Transmit power and transfer a motion from one
shaft to another.
• Transmits Less power compared to chain ,
rope or belt
• Increase or decrease velocity ratio in various
machines
• Needs small space
• More efficient and effective
• Costly
• Eg. Watches , cranes
 Types of Gear Drive Systems

• Spur gear
• Helical gear
• Crossed helical gear
• Bevel gear
• Worm gear
• Pinion–rack
 Gear Trains
Group of gear shaft wheels for increasing or
decreasing the speed of shaft wheel.
 Clutches
A coupling device used to separate the engine
and mechanical transmission .
 Belt/Rope Pulley Drives
• Transmission of mechanical power from one
shaft to another. Long distance transmission.
• Linear i/p – o/p
characteristics.
• Transmission due to
frictional force
between pulley and
belt.
 Cam–follower Mechanisms
To generate non-uniform linear or rotary follower
motion from uniform input motion of the cam.
Cam i/p or driving member
Follower o/p or driven member
Displacement
Pick
Follower

Rise Return Back

Dwell Dwell

0 90 180 270 360

Follower motion Profile
Knife (Point) Edge Cam Followers
• Eccentric cams ( pumping system)
• Heart-shaped cams(uniform speed) OFFSET

• Pear-shaped cams ( engine valve

control)
Roller-type Followers (oil lubrication)
 Ratchets and Pawls
• Lock a mechanism when loaded
• Wind up a cable of a drum & prevent
unwinding
 Belt and Chain Drives

Driving pully

• Uses frictional force developed to transmit power

between shaft
• Transmission of torque takes place due to
difference in tension between the tight side and
slack side
Types of Belts Rectangular cross section
• Flat belts ɳ =98% with noise
Crowned pulley
• Round belts
• V belts
• Timing belts

• Toothed wheel
grooved belt grooved pulley
• Support slow
and Fast speed
• Constant
Timing Belt angular velocity V Belt
without slip
 Bearings
Stationary element used to support, guide & restrain
rotating shaft or axle to confine their motion

• Minimum frictional loss &

• Maximum accuracy
• Grease or lubricating oil
Types
• Linear Bearings
• Journal Bearings
• Hydrodynamic Bearings
 Chapter 13
Hydraulic and Pneumatic
Actuating Systems
 Introduction
• Mechanical actuators issues: Heavy weight, friction,
noise, temperature rise, and sometimes pollution.
• A hydraulic signal: Produced by hydraulic pressure and
is used for higher-power control devices
• Pneumatic signal: Produced by air or gas pressure.
• Used to actuate large valves and other high-power
devices.
• A hydraulic and pneumatic system is collectively called
a fluidic system.
 Components of Hydraulic Circuits

• Reservoir.
• Pump
• Pressure gauge
• Flow meter
• Pressure relief valve
• Flow valve
• Accumulator
• Fluid control valve
• Check valve
• Hydraulic motor
 Valves /Types of Valves

Valve symbols
 Pressure Control Valves

• Pressure Relief (Limiting) Valves

• Pressure Regulators
• Pressure Sequencing Valves
 Directional Control Valves
Poppet Valve Spool Valve
 Methods of Spool Actuation

• Manual
• Mechanical actuation.
• Pneumatic actuation
• Electrical actuation
• Hydraulic actuation
 Linear Actuators—hydraulic Cylinders
• A fluid power hydraulic cylinder performs its
task under pressure for movement which is
directly proportional to the applied force or
power; thus, it is treated as a linear actuator
• Classification of Cylinder
(a) single-acting cylinders (SACs) and
(b) double-acting cylinders (DACs).
 Flow Control Valves
• Flow control in hydraulic and pneumatic
circuits is required for the speed control of the
system using a linear or rotary motion.
• Types of flow control:
Fixed flow valves,
variable flow valves,
and pressure-compensated flow control valves
Contd...
 Pneumatic Systems

• A pneumatic system is like a hydraulic system

• Components :a compressor,
- an air treatment unit,
- a reservoir,
-a DCV with air as the medium
Contd...
 Pneumatic Valves

• Directional Control Valves

• Spool Valves
 Pneumatic Cylinders
Types of Pneumatic cylinders :
-single-acting and
_ double-acting types
 Pneumatic Circuits
• A pneumatic circuit components: a
compressed air ,an SAC or a DAC with a
three-way or a 5/2-way valve.
Contd...
 Thanks
• Thanks