Actuators er.sanyam s. saini (me regular)

Fluid Power: Hydraulics and Pneumatics

Actuators

Presented by:-

Er. Sanyam S. SainiME (I&CE) (Regular)2012-14

OutlinesIntroduction to Actuators.Classification of ActuatorsPneumatic Actuators & Classifications- (i). Introduction; (iv). Working ; (ii). working Principle; (v). Advantages & Disadvantages; (iii). Construction; (vi). Applications Hydraulic actuators & Classifications- - (i). Introduction; (iv). Working ; (ii). working Principle; (v). Advantages & Disadvantages; (iii). Construction; (vi). Applications Electrical Actuators & Classifications- - (i). Introduction; (iv). Working ; (ii). working Principle; (v). Advantages & Disadvantages; (iii). Construction; (vi). Applications 23/18/2013Er. Sanyam S. Saini

Introduction to Actuators.

An actuator is something that actuates or moves something. An actuator is a device that coverts an input energy into motion or mechanical energy.

The input energy of actuators can be manual (e.g., levers and jacks), hydraulic or pneumatic (e.g., pistons and valves), thermal (e.g., bimetallic switches or levers), and electric (e.g., motors and resonators).

Actuators are final element in a control system.

The actuator was discovered by Logan in 1969.33/18/2013Er. Sanyam S. Saini

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4Introduction to ActuatorsAn actuator is that creates motion in a straight line, as contrasted with circular motion of a conventional electric motor.

Linear actuators are used in machine tools and industrial machinery, in computer peripherals such as disk drives and printers, in valves and dampers, and in many other places where linear motion is required.

Hydraulic or pneumatic cylinders inherently produce linear motion; many other mechanisms are used to provide a linear motion from a rotating motor3/18/2013Er. Sanyam S. Saini

Classification of ActuatorsPneumatic

Hydraulic

Electrical/Electronic53/18/2013Er. Sanyam S. Saini

Pneumatic Actuators6

3/18/2013Er. Sanyam S. Saini

A set of devices into with one or more pneumoengines, which are determined to start mechanisms or some other objects by means of pressed working gas is called pneumatic actuator, or pneumoactuator.

The devices intended for transformation of potential and kinetic energy of the stream of compressed gas in mechanical energy of the output link that can be, for example, a rod of the piston, a shaft of the turbine or the case of the jet device is called pneumatic engines of the automated actuator.

They are devices providing power and motion to automated systems, machines and processes.

A pneumatic cylinder is a simple, low cost, easy to install device that is ideal for producing powerful linear movement.

7Pneumatic Actuators3/18/2013Er. Sanyam S. Saini

Adverse conditions can be easily tolerated such as high humidity, dry and dusty environments and cleaning down with a hose.The bore of a cylinder determines the maximum force that it can exert.The stroke of a cylinder determines the maximum linear movement that it can produce.Thrust is controllable through a pressure regulator.Pneumatic actuators include linear cylinders and rotary actuators.

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8Basic Construction

1 cushion seal 2 magnet 3 cushion sleeve 4 barrel 5 guide bush 6 rod and wiper seal 7 front end cover 8 front port 9 reed switch10 piston rod11 wear ring12 piston seal13 rear end cover14 cushion screw3/18/2013Er. Sanyam S. Saini

9Types of Pneumatic ActuatorPneumatic actuators are made in a wide variety of sizes, styles and types including the following Single acting with and without spring returnDouble actingRod lessRotaryClampingBellows3/18/2013Er. Sanyam S. Saini

10Single acting spring returnSingle acting cylinders have a power stroke in one direction only

Normally inNormally out3/18/2013Er. Sanyam S. Saini

11Double actingDouble acting cylinders use compressed air to power both the outstroke and instroke.Superior speed control is possible3/18/2013Er. Sanyam S. Saini Non cushioned cylinders are suitable for full stroke working at slow speed.Higher speeds with external cushions.

12Advantages of Pneumatic Actuators.Simplicity of realization relatively to small back and forth motions;Sophisticated transfer mechanisms are not required;Low cost;High speed of moving;Ease at reversion movements;Tolerance to overloads, up to a full stop;High reliability of work;Explosion and fire safety;Ecological purity;Ability to accumulation and transportation.3/18/2013Er. Sanyam S. Saini

13Disadvantages of Pneumatic Actuators.Compressibility of the air ; Impossibility to receive uniform and constant speed of the working bodies movement ;Difficulties in performance at slow speed;Limited conditions - use of compressed air is beneficial up to the definite values of pressure;Compressed air requires good preparation3/18/2013Er. Sanyam S. Saini

Hydraulic Actuator14


IntroductionA hydraulic drive system is a drive or transmission system that uses pressurized hydraulic fluid to drive hydraulic machinery.

The term "hydraulic actuator" refers to a device controlled by a hydraulic pump.

A familiar example of a manually operated hydraulic actuator is a hydraulic car jack. Typically though, Principle Used in Hydraulic Actuator System


Working Principle of Hydraulic Actuator Pascals Law

Pressure applied to a confined fluid at any point is transmitted undiminished and equally throughout the fluid in all directions and acts upon every part of the confining vessel at right angles to its interior surfaces.

Amplification of Force

Since pressure P applied on an area A gives rise to a force F, given as, F = PA Thus, if a force is applied over a small area to cause a pressure P in a confined fluid, the force generated on a larger area can be made many times larger than the applied force that crated the pressure. This principle is used in various hydraulic devices to such hydraulic press to generate very high forces.


17Construction of Hydraulic Actuator A hydraulic drive system consists of three parts:

1.Generator (e.g. a hydraulic pump), driven by an electric motor,

2. Combustion engine or a windmill; valves, filters, piping etc. (to guide and control the system)

3. Motor (e.g. a hydraulic motor or hydraulic cylinder) to drive the machinery.3/18/2013Er. Sanyam S. Saini

18Hydraulic Actuator Parts of a typical cylinder


19Working of Hydraulic ActuatorsHydraulic actuators or hydraulic cylinders typically involve a hollow cylinder having a piston inserted in it. An unbalanced pressure applied to the piston provides force that can move an external object. Since liquids are nearly incompressible, a hydraulic cylinder can provide controlled precise linear displacement of the piston. The displacement is only along the axis of the piston. The piston forms sealed, variable-volume chambers in the cylinderSystem fluid forced into the chambers drives the piston and rod assemblyLinear movement is produced3/18/2013Er. Sanyam S. Saini

20Classifications of Hydraulic ActuatorCylinders are typically classified by operating principle or by construction typeSingle-acting or double-actingTie rod, mill, threaded end, or one pieceSingle-acting cylinders exert force either on extension or retraction.They require an outside force to complete the second motionDouble-acting cylinders generate force during both extension and retractionDirectional control valve alternately directs fluid to opposite sides of the pistonForce output varies between extension and retraction


21Hydraulic ActuatorSingle- and Double-Acting Cylinders

Single-actingDouble-acting3/18/2013Er. Sanyam S. Saini

22Hydraulic ActuatorTie-Rod Cylinder


23Hydraulic Actuator Mill cylinders


24Hydraulic ActuatorThreaded-end cylinder


25Infinitely variable control of gear-ratio in a wide range and an opportunity to create the big reduction ratio;Small specific weight, i.e. the weight of a hydro actuator is in ratio to transmitted capacity (2-3 kg / kWt);Opportunity of simple and reliable protection of the engine from overloads;Small sluggishness of the rotating parts, providing fast change of operating modes (startup, dispersal, a reverser, a stop);Simplicity of transformation of rotary movement into reciprocating one; Opportunity of positioning a hydraulic engine on removal (distance) from an energy source and freedom in making configuration.Advantages of Hydraulic Actuators3/18/2013Er. Sanyam S. Saini

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Disadvantages of Hydraulic Actuators26Efficiency of a volumetric hydraulic actuator is a little bit lower, than efficiency of mechanical and electric transfers, and during regulation it is reduced;Conditions of operation of a hydraulic actuator (temperature) influence its characteristics;Efficiency of a hydraulic actuator is a little reduced in the process of exhaustion of its resource owing to the increase in backlashes and the increase of outflow of liquid (falling of volumetric efficiency);Sensitivity to pollution of working liquid and necessity of high culture service.3/18/2013Er. Sanyam S. Saini

27Applications of Hydraulic Actuators


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Electrical Actuators

IntroductionAn electrical motor is an Transducer & an Actuator because it converts electrical current into a large magnetic field which then turns a shaft. (Mechanical energy)

All electric motors use electromagnetic induction to generate a force on a rotational element called the rotor.

The torque required to rotate the rotor is created due to the interaction of magnetic fields generated by the rotor, and the part surrounding it, which is fixed, and called the stator.


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Classification of Electrical Actuators303/18/2013Er. Sanyam S. Saini Solenoid

Electrical Motors

Stepping Motors

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SolenoidSimple form of electromagnet that consists of a wire bobbin of isolated copper, or of another appropiate conductor, who is coiled in spiral around the surface of a cylindrical body, generally with transverse circular section.

When the electrical current is sent across these wound, they act as electromagnet.

The created magnetic field is the motive force used to open the valve.3/18/201331Er. Sanyam S. Saini

Electric Motors323/18/2013Er. Sanyam S. Saini Electromechanical device that converts electrical energy to mechanical energyThe 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.Mechanical energy used to e.g.Rotate pump impeller, fan, blowerDrive compressorsLift materialsMotors in industry: 70% of electrical load

Electric Motors333/18/2013Er. Sanyam S. Saini

Electric Motors

Alternating Current (AC) Motors

Direct Current (DC) MotorsSynchronousInductionThree-PhaseSingle-Phase

Self Excited

Separately ExcitedSeriesShuntCompound

Applications 343/18/2013Er. Sanyam S. Saini

Stepper Motors353/18/2013Er. Sanyam S. Saini A stepper motor possesses the ability to move a specified number of revolutions or fraction of a revolution in order to achieve a fixed and consistent angular movementThis is achieved by increasing the numbers of poles on both rotor and statorAdditionally, soft magnetic material with many teeth on the rotor and stator cheaply multiplies the number of poles (reluctance motor)

Construction 363/18/2013Er. Sanyam S. Saini This figure illustrates the design of a stepper motor, arranged with four magnetic poles arranged around a central rotorNote that the teeth on the rotor have a slightly tighter spacing to those on the stator, this ensures that the two sets of teeth are close to each other but not quite aligned throughout

Construction 373/18/2013Er. Sanyam S. Saini Movement is achieved when power is applied for short periods to successive magnetsWhere pairs of teeth are least offset, the electromagnetic pulse causes alignment and a small rotation is achieved, typically 1-2o

Working 383/18/2013Er. Sanyam S. Saini

The top electromagnet (1) is charged, attracting the topmost four teeth of a sprocket.


The top electromagnet (1) is turned off, and the right electromagnet (2) is charged, pulling the nearest four teeth to the right. This results in a rotation of 3.6


The bottom electromagnet (3) is charged; another 3.6 rotation occurs.


The left electromagnet (4) is enabled, rotating again by 3.6. When the top electromagnet (1) is again charged, the teeth in the sprocket will have rotated by one tooth position; since there are 25 teeth, it will take 100 steps to make a full rotation.

Advantages 423/18/2013Er. Sanyam S. Saini Stepper motors have several advantages:Their control is directly compatible with digital technologyThey can be operated open loop by counting steps, with an accuracy of 1 step.They can be used as holding devices, since they exhibit a high holding torque when the rotor is stationary

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Actuators er.sanyam s. saini (me regular)