ACTUATORSAND OPTICAL SPEED SENSOR

AND APPLICATION IN AUTOMATIC TRANSMISSION

By guided bySARATH.P.R U.PRAKASH12402052U7

INTRODUCTIONAn actuator is a kind of motor that controls or moves

mechanisms or systems.

Actuators are extremely useful devices and have diverse range of uses in engineering.

It is operated from a source of energy usually from electric current ,hydraulic fluid pressure , pneumatic pressure.

An actuator is a mechanism by which a control system acts on environment

The control system can be an electronic system , software based..

Type of medium

Hydraulic pneumatic

electrical

ACTUATORS

HYDRAULIC ACTUATORS

PRINCIPLEPascal’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 = P x A

Hydraulic refers to means and mechanisms of transfer of power through liquids.

Hydraulic systems convert mechanical power to fluid power , transmit the fluid power to some location , convert back this fluid power to mechanical power to do useful work.

Hydraulic systems are used when large force are required.

PARTS

CYLINDER AND PISTON

DIRECTION CONTROL VALVE

PUMP

PRESSURE RELIEF VALVE

WORKING OF HYDRAULIC ACTUATION SYSTEMΑ directional control valve controls the direction of oil flow in the system

and, therefore, the direction of motion of the cylinder piston.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 body

case 2 Lever is moving towards valve body

• 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 control valve.

case 3 : Lever is idle in position

• When the directional control valve lever is released, the valve automatically returns

to the center (neutral) position.

•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.

ADVANTAGES and DISADVANTAGESActuation of large control surface with minimal input.Variable speed and direction.overload protection.Greater load carrying capacity.Leakage may occurHigh fire riskTemperature changes alters the viscosity of the fluid.

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

WORKING OF PNUEMATIC ACTUATORS 

ADVANTAGES AND DISADVANTAGES Infinite availability of source

Safe and clean

Negligible maintenance

Low cost

Easy to leak

Potential noises

ELECTRIC MOTORS

•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.

COMPONENTS OF AN ELECTRIC MOTORThe principle components of an electric motor are:

• STATOR

• ROTOR

• COMMUTATOR

• BRUSHES

DC MOTORThe classic DC motor has a rotating armature in the form of an

electromagnetA 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 motor

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 direction

WORKING

PM

BRUSH

ARMATURE

COMMUTATOR

STEPPER MOTORWhat is a stepper motor?

1. Motor that moves one step at a time

2. Brushless motor

3. each step is defined by a step angle

4. Rotation of the angle is proportional to the input impulse

2

1

S

N

1

2

Outside Casing

Stator

Rotor

Internal components of a Stepper Motor

OPTICAL SPEED SENSORS

• First appeared in general motor vehicles

• It uses photocell , light emitting diode(LED) and two blade mirrored reflector to generate electrical signal

• More fast and accurate

• Located inside the speedometer head at the back of the control panel

When the vehicle is in motion the speedometer cable spins the two blade reflector

Each time the reflector rotates through the LED beam , the light is reflected to the photocell

This generates an electric signal and also electric pulses

the computer is programmed to convert the pulses to the electronic measurement of vehicle speed

OPTICAL SPEED SENSOR

Application in automatic transmissionSince the optical speed sensors are fast and accurate ,they

have wide application in automatic transmission.

Using the data from the optical speed sensors the ,the gear can be shift automatically at the desired speed.

Thus the vehicle can be operated at optimal efficiency without much skill of driver.

For the torque converter clutch operation speed sensor data is necessary.

Conclusion

Actuators have wide application in our daily life

Hydraulic ,electric and pneumatic actuators are used I almost all automobiles.

Optical speed sensors are necessary for automatic transmission.

referenceErylmaz B, Wilson BH (2000). Combining

leakage and orifice flows in a hydraulic servo valve model. J. Dynamic Systems Measurement Control, 122: 576-579

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