Introduction To Marine Automation 2o6p3x

Auto 1 – Marine Automation

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Ref: Marine Automation, by Augusto U. Escolano

Ch 1 - General ●

Development of Automatic Control - Man's brute strength or animal's - mechanical devices such as wheels or levers - natural resources such as wind for powering sailing vessels, windmills and waterfalls for waterwheels - steam engine. It provided power that could be harnessed at will.

Development of Automatic Control ●

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Early machines are manual in nature and the adjustments had to be reset frequently to maintain the desired output or performance. Newer equipment - relieve people of monotonous activities so more time is devoted to other endeavors. - complex controls that humans cannot duplicate.

Development of Automatic Control ●

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The invention of the diesel engine provided power to produce electricity The tracking apparatus of position was used in automatic steering of ships Application of negative to an amplifier improved its frequency response and stability.

Electro-technical Control System ●

Solenoid - electromechanical device made up of coil which produces a magnetic field when electric current is ed through it. In some applications, the coil surrounds an iron plunger which becomes magnetized and moves in one direction upon application of current. - produces a direct linear stroke, limited to a maximum distance of around 100mm

Electro-technical Control System ●

Solenoid

Electro-technical Control System ●

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DC motor – when fitted with a tachometer and driven by a thyristor drive, can an excellent speed control but has high maintenance requirements for brushes and commutator. AC induction motor – maintenance free but a fixed speed device. Both DC & AC motors are rotary and their outputs need to be converted to linear motion

Electro-technical Control System ●

Electrical System Based on a Three-Phase Motor

Hydraulic Control System ●

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Ram – consists of a movable piston connected directly to the output shaft. If fluid is pumped into pipe A, the piston will move up and the shaft will extend; if into pipe B, the shaft will retract. Some method of retrieving fluid from the nonpressurized side of the piston must be incorporated.

Hydraulic Control System

Hydraulic Control System - Precise control at low speeds - No over travel protection is required - the pump needs external power source - hydraulic fluids need to be very clean - leaks of fluid from the system are unsightly, slippery, and environmentally very undesirable

Pneumatic Control System

Pneumatic Control System - operating pressure are lower than in a hydraulic system, so actuators are larger. - return air is simply vented to the atmosphere.

Comparison ●

Electro-technical - small & adaptable with cheap flexible transmission line - no moving parts, but generates heat - stable, generally accurate - low power consumption, direct application to computer but needs final control element transducers

Comparison ●

Pneumatic - no heat generation and safe in explosive atmosphere - less susceptible to power supply fluctuation but have time lags - direct application without transducer or too large final power actuators

Comparison ●

Hydraulic - instant responds as fluid is virtually incompressible - readily provide any type of motion - accurate position control - high power amplification

A Simple Control Loop ●

Measurement

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Comparison

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Judgment

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Operates

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confirms

Automatic Control ●

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Has the ability to judge its own work and performs its duty to the machine, such as measurement, comparison, and judgment. Example is the automatic control of liquid level in a boiler. 1. desired value

6. servo-motor

2. voltage

7. power source

3. differential xformer 8. float 4. adjuster

9. boiler

5. current

10. feed water

Automatic Control ●

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control system or closed loop control system Detects quantities like temperature, pressure, flow, voltage, current or the position of a machine in order to coincide them with the designated desired value, and compares and judges them with the desired value, and makes a machine perform correction action automatically according to the difference between the quantities.

Automatic Control ●

Uniformity of goods and attain mass production.

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Economical and safe operation

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Simplify facilities and ensure long life

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Improved labor condition and safety

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Reduce manual labor and related expenses

Automatic Operation ● ●

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Open loop control system Automation (automatic operation / automatization) Automatic control

Block Diagram Symbols

Analog Device vs Digital Device ●

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Analog – the equation describing the operation of the device is analogous to that for the actual system Digital – extensively used in programming Because of their ability to solve complicated mathematical equations, they are incorporated as part of the control system to compute desired information [email protected]