SERVOMECHANISM & ITS IMPORTANCE

Presenters

Khurram Sohail AU-036 Faizan Saleem AU-043 Muhammad Hashim AU-011 Sidra Shakil AU-015

DefinitionDefinition

Servomechanism is an automatic control system in which the output is constantly compared with the input through feedback so that the error or difference between the two quantities can be used to bring about the desired amount of control.

DescriptionDescription

What is the use of servomechanism? The term correctly applies only to systems where the feedback or

error-correction signals help control mechanical position or other parameters.

The car's cruise control uses closed loop feedback, which classifies it as a servomechanism. A servomechanism is unique from other control systems because it controls a parameter by commanding the time-based derivative of that parameter Servomechanism may or may not use a servomotor.

Servomechanisms were first used in military fire-control and marine navigation equipment. Today servomechanisms are used in automatic machine tools, satellite-tracking antennas and remote control airplanes, automatic navigation systems on boats and planes, and antiaircraft-gun control

Diagram

A common type of servo provides position control.

The servo consists of some control circuitry mounted on the circuit board, a motor which provides movement, a gear train which multiplies the torque of the motor, an output shaft which is the output of the servo, and a feedback potentiometer. 

Servos are commonly electrical or partially electronic in nature, using an electric motor as the primary means of creating mechanical force. Other types of servos use hydraulics, pneumatics, or magnetic principles.

Usually, servos operate on the principle of negative feedback, where the control input is compared to the actual position of the mechanical system as measured by some sort of transducer at the output. Any difference between the actual and wanted values (an "error signal") is amplified and used to drive the system in the direction necessary to reduce or eliminate the error.

Purpose of Servomechanism

Automatic ControlAccurate control of motion without the need for human attendants.

Regulation and Self-calibrationMaintenance of accuracy with mechanical load variations, changes in the environment, power supply fluctuations, and aging and deterioration of components.

Power AmplificationControl of a high-power load from a low-power command signal.

Remote Control/Shaft RepeaterControl of an output from a remotely located input, without the use of mechanical linkages.

Basic components of Servomechanism All servomechanisms have at least these basic components: a command

device, an error detector, an error-signal amplifier, a feedback element and a device to perform any necessary error corrections ( the servomotor ). The command device receives information, usually from outside the system, that represents the desired position of the controlled device. This information is converted to a form usable by the system (such as a voltage) and is fed to the same error detector as is the signal from the controlled device. The error detector compares the feedback signal (representing actual position) with the command signal (representing desired position). Any discrepancy results in an error signal that represents the correction necessary to bring the controlled device to its desired position. The error-correction signal is sent to an amplifier, and the amplified voltage is used to drive the servomotor, which repositions the controlled device.

Importance of Servomechanism in Engineering

As you know servomechanism is used to correct the performance of a setup automatically, by means of error-sensing feedback. Therefore it brought a new revolution in field of engineering. Servomechanisms were first used in military

Such as antiaircraft radar tracking control system.

Servomechanism in AutomobilesServomechanism in Automobiles

A servo is used in automobiles to amplify the steering or braking force applied by the driver. However, these devices are not true servos, but rather mechanical amplifiers. Now a day’s electromechanical system are used in vehicles to improve the performance and safety.

Types of Servo in Automobile:Types of Servo in Automobile:

Pneumatic Hydraulic

Importance in automobileImportance in automobile

Hydraulic-vacuum servo Braking system:

servo (brake booster) Connected with master cylinder. Consists of 2 chambers separated by

diaphragm. Vacuum and Air. When pedal is pressed hydraulic from master

cylinder enters into servo and opens the air control valve.

The result is additional force pushing the pistonof main brake cylinder, slight press upon pedal will be amplified through servo

You can check importance of servo mechanism by your self.

Stop the engine and press the brake pedal you will feel difficulty in it.

Position sensors in AutomobilePosition sensors in Automobile

Explaining this principle; we frequently use the steering of an automobile as an active servo system. I don't mean the proportional hydraulic control of the power steering system. The person behind the wheel does not calculate how many degrees of rotation the steering wheel must be turned for taking that five degree right hand banked turn that I'm approaching. All of the parameters of how quickly to turn, how far to turn and when to turn are done by feedback through the grey matter processor of the driver monitoring if the car stays in lane. Some systems in a car now have silicon processors doing some feedback control.

Active Body Control System Active Body Control System (ABC)(ABC)

ABC is basically an advance chassis technology introduced by Mercedes-Benz.

This system monitors how much car dips or lifts during acceleration, braking n making sharp turns.

This system will correct any problems involving positioning of the vehicle to prevent car from losing control.

Components:

sensors(13)

microprocessor gets information from sensors, check whether vehicle is in safe or unsafe situation and directs signal to hydraulic servo to correct vehicle’s positioning.

hydraulic mechanism(4)(uses automatic feedback to correct the position of vehicle with in fraction of seconds by counter balancing the positioning).

The four spring struts are equipped with microprocessor-controlled plunger cylinders which almost completely compensate yawing, pitching and rolling movements of the vehicle body.

Some properties of ABCSome properties of ABC

The system also incorporates height adjustable suspension, which in this case lowers the vehicle up to eleven millimeters between the speeds of 60 km/h (37 mph) and 160 km/h (99 mph) for better aerodynamics, fuel consumption, and handling.

The ABC system also allows self-leveling suspension, which raises or lowers the vehicle in response to changing load (i.e. the loading or unloading of passengers or cargo.

etc….

Electronic Fuel InjectorElectronic Fuel Injector All fuel injection systems include air-flow metering devices to control the

quantity of fuel discharged through throttle flow devices called "injectors”.

Electric-injectors consist of a solenoid-operated valve which quantifies flow into a nozzle from a constant pressure source by the amount of time it is opened.

The main object of this invention is to implement "closed-loop" fuel injection for spark-ignition engines.

An electronic fuel injection system includes an electrically-driven fuel pump which supplies and develops the fuel pressure necessary for the system.

The fuel is injected by solenoid-operated fuel injection valves into the cylinder intake port.

The injection valves are controlled by an Electronic Control Unit (ECU) which governs the amount of fuel injected by the length of time they stay open from a constant pressure source.

The quantity of fuel flow only dependent upon the fuel pressure to the injector.

Electronic Fuel InjectorElectronic Fuel Injector

Conclusion

servo is a mechanical or electromechanical system for control of the position or speed of an output. Negative feedback is incorporated to minimize discrepancies between the output state and the input control setting An Automatic device used to correct the performance of a mechanism by means of an error-sensing feedback. The term servomechanism properly applies only to systems in which the feedback and error-correction signals control mechanical position or one of its derivatives such as velocity or acceleration’s a type of control system that automatically corrects errors in the position, velocity, or acceleration of an object. Industry uses servomechanisms to control automatic machines such as robots.

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