3. HYDRAULIC ACTUATORS
• Hydraulic Actuators are used in
industrial process control, employ
hydraulic pressure to drive an output
Principle : Pascal’s Law
“Pressure exerted anywhere in
a confined incompressible fluid is
transmitted equally in all directions
throughout the fluid, acts upon every
part of the confining vessel at right
angles to its interior surfaces”.
F = PxA
4. WORKING OF HYDRAULIC ACTUATION SYSTEM
•Α directional control valve
controls the direction of oil flow in
the system and, therefore, the
direction of motion of the cylinder
•The valve has four ports,
labeled Ρ, Τ, Α, and Β. Ρ and Τ
stand for pressure and tank (or
reservoir), and Α and Β are output
ports. The valve can be operated
in three different positions.
Case 1 Lever is moved away from valve
5. case 2 Lever is moving towards valve
• The oil from the pump flows through
path Ρ-Α of the valve to the upper end
of the cylinder.
• The oil pushes the piston downward,
which lowers the attached load. At the
same time, the oil at the lower end of
the cylinder flows back to the reservoir
through path Β-Τ of the directional
6. case 3 : Lever is idle in position
• When the directional control valve
lever is released, the valve
automatically returns to the center
•In this position, all four ports are
blocked and oil cannot escape from
either side of the cylinder.
•. This stops the movement of the piston
and causes oil to flow from the pump
back to the reservoir through the
pressure relief valve.
7. PNEUMATIC ACTUATOR
• A pneumatic actuator converts energy (typically in the form of compressed Air) into
motion. The motion can be rotary or linear, depending on the type of actuator.
• A Pneumatic actuator mainly consists of a piston, a cylinder, and valves or ports.
• Pneumatic systems are very common, and have much in common with hydraulic
systems with a few key differences
8. WORKING OF PNUEMATIC ACTUATORS WORKING OF PNUEMATIC ACTUATORS
• Pneumatic actuators are generally relatively simplistic and
depend on their own ability to convert potential energy into
9. Electric MotorsElectric Motors
• Electric motors are the most common source
of torque for mobility and/or manipulation in
• The physical principle of all electric motors is
that when an electric current is passed
through a conductor (usually a coil of wire)
placed within a magnetic field, a force is
exerted on the wire causing it to move
10. Components Of An Electric MotorComponents Of An Electric Motor
The principle components of an electric motor are:
•North and south magnetic poles to provide a strong magnetic field. Being made
of bulky ferrous material they traditionally form the outer casing of the motor and
collectively form the stator
•An armature, which is a cylindrical ferrous core rotating within the stator and
carries a large number of windings made from one or more conductors
11. Components Of An Electric MotorComponents Of An Electric Motor
• A commutator, which rotates with the armature and consists of copper contacts
attached to the end of the windings
• Brushes in fixed positions and in contact with the rotating commutator contacts.
They carry direct current to the coils, resulting in the required motion
12. Components Of An Electric MotorComponents Of An Electric Motor
13. How Do Electric MotorsHow Do Electric Motors Work?Work?
• The classic DC motor has a rotating armature in the form of an electromagnet
• A rotary switch called a commutator reverses the direction of the electric current
twice every cycle, to flow through the armature so that the poles of the
electromagnet push and pull against the permanent magnets on the outside of the
• As the poles of the armature electromagnet pass the poles of the permanent
magnets, the commutator reverses the polarity of the armature electromagnet.
• During that instant of switching polarity, inertia keeps the motor going in the proper
14. Piezoelectric motorPiezoelectric motor
• A piezoelectric motor or piezo motor is a type of electric motor based upon the
change in shape of a piezoelectric material when an electric field is applied.
• Piezoelectric motors make use of the converse piezoelectric effect whereby the
material produces acoustic or ultrasonic vibrations in order to produce a linear or
• A bi-laminar actuator is made from a piezoelectric smart material that returns to its
original shape after a force is to applied to it.
• “A flexing or bending actuator is designed to produce a relatively large mechanical
deflection in response to an electrical signal.”
• “Two thin strips of piezoelectric ceramic are bonded together, usually with the
direction of polarization coinciding, and are electrically connected in parallel.”
16. Basic Working PrincipleBasic Working Principle
• “When electrical input is applied, one ceramic layer expands and the other
contracts, causing the actuator to flex.”
+ - + -
17. MEMS ACTUATORSMEMS ACTUATORS
V-Shaped Thermal Actuators
These actuators are based on the constrained thermal expansion of
the angled beams (a result of Joule heating when a current is passed through the legs
of the actuator), resulting in motion of the centre shuttle in the direction shown by
the arrow in the figure.