chapter1 intro to automation

LDD 30402 – Automation & Control

AZJ, MSH Chapter 1 - Intro to Automation

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11.. OOVVEERRVVIIEEWW OOFF AAUUTTOOMMAATTIIOONN SSYYSSTTEEMM 1.1 Definition of automation system - The ability of a system or device to perform work intelligently with minimum or without human supervision or intervention. 1.2 How automation arises? Manual Repetitive Similar work done over and over again using physical strength with minimum or without tools.

Ex: Loading and unloading of rice pack from padi field to truck. Mechanization Work is done by machine under direct supervision.

Ex: Filling machine fills rice into sacks, conveyor belt transfers the sacks to another man to load it into a truck.

MANUAL REPETITIVE

MECHANIZATION

AUTOMATION



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Automation Work is done by machine intelligently with minimum or without human supervision.

Ex: - Auto filling of rice pack to ensure even quantity per sack;

- Intelligent Conveyor system that do auto sorting for accepting and rejecting packages; and - Robotics arm to do lifting and transferring works.

1.3 Why we need automation? - Increase product standards with consistent quality. - Higher throughput. - Reduce labour dependencies. 1.4 Who needs automation? - Small and medium industries (SMI), - Multi-national companies (MNC), 1.5 Where does automation apply to? - Assembly line, - Test and finishing packaging (repetitive process), - Hazardous environment. - On board a modern ship. - Etc. 1.6 Benefits of automation? - Cost reduction in terms of labour requirement. - Increase efficiency in terms of quality and quantity. - Flexible to market demand (faster and flexible) i.e. changes in product and changes in process.



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- Reliable: automation processes can sustain long hours but still maintain its desired performance (consistent quality and durability). - High repeatability: output from the automatic machine can be scheduled and control accordingly. - Safe: automated machines reduce and minimize human contact or interaction in hazardous environment. - A solution for labour shortage. 1.7 Examples of automation - Industrial environment: conveyor system, pick and place system, ship control and monitoring system (SCAMS), fire fighting system, CCTV and security alarm system, etc. - Domestic environment: automatic door/gate, washing machine, smart house, etc. - Commercial environment: building automation system (BAS), lifts and escalators, automatic teller machine (ATM), supervisory control and data acquisition (SCADA), etc. - Public utilities: traffic lights, etc. 1.8 Automated system. - Automated system functions by the motion of specific hardware controlled by dedicated software. - What is hardware? : It is the physical element in the automated system such as

sensors, keyboard, monitor, PLC, PC, etc. - What is software? : It comprises of sets of instruction that tell PLC or PC what to

do. It can be written in ladder diagram, codes of certain computer languages, logic presentation, etc.

- How automation works? : Automated system responds upon the processing of its instruction or programme. The system should know its environment by having input signals from various sensors. The input signals exist in the form of compressed fluid, incompressible fluid (pneumatic/hydraulic), or electrical. The relationship between input and output, and elements associated with them are as below.



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- Input elements: electrical, pneumatic, and hydraulic. (sensor) - Ex.:

- Output elements: electrical, pneumatic, and hydraulic. (actuator) - Ex.:



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- Processing element: electrical, pneumatic, and hydraulic. (processor) - Ex.:



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1.9 Sensor. - Definition: Sensors are parts of a control system which is responsible for collecting and preparing process status data and passing it to the processor. - Functions:

The ability to control a process or machine is dependent on the ability to sense what is happening.

A sensor in an automated system is a device that can: o Detect the presence of objects o Detect the difference between objects sensed (whether metallic or non-

metallic) o Measure temperature o Measure flow rate o Measure force o Measure velocity o Measure position o Measure acceleration

- Distinguishing features of sensors:

Contact sensor: Are the most widely used form of actuator motion or positioning sensing. It is achieved with mechanically operated valves such as roller valves, plunger valves, one way trip valves, whisker valves and etc.

Contactless sensors: must be chosen wherever physical contact of the sensing mechanism with the object to be detected is either impossible or undesirable. Such applications range from food processing, liquid sensing, extreme lightweight object sensing (ex: paper sheet), to the sensing of gauge hands on pressure gauge or weighing machines, and strip material correction when being rolled onto reels for powder storage in tanks and silos.

- Signal: represent information and may take the form of a value or curve of a physical variable, and may refer to the transmission, processing or storage of information.

Analogue signals: is a signal where various data are assigned point for point to a continuous value range of the signal parameter. The data content can therefore assume any desired value within certain limits.

Example: pressure gauge



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Further example: temperature range of thermometer, reading on tachometer, speedometer in motor vehicles.

Digital signals: used in control systems that have one or two possible levels or

conditions; therefore they are binary signals. We can represent this signal in numerical form by assigning one of the levels a value of ‘1’and the other a value of ‘0.’ i.e. the two values in a binary system.



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Further example: counter, digital measuring equipment. Types of input and output signals:



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A sensor may be incorporated with transmitter or converters in order to produce an output signal type different from the input signal type.

- Selection criteria for sensors:

In selecting a sensor for a particular problem, various physical and technical factors must be considered in order to determine the most suitable sensor for the problem. Below is a list of evaluation criteria which must be weighted differently in accordance with the task in hand.



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1.10 Processor. - Definition: the signal which are fed to the inputs from the signal generators (sensors) are processed and fed to the outputs. - Functions: signal processing is carried out in the processor by means of various basic functions. The basic functions in the field of signal processing comprise of:

Logic function: AND, OR, NOT, NOR, NAND gates. Timing function: is carried out by means of functional elements to delay, shorten

and expand signals. Memory function: is carried out with functional element, e.g. double pilot valves

and self holding circuits (electrical/pneumatic). - Type of signal processing:

Pneumatic signal processing o Logic function

The pneumatic AND element is the ‘two pressure valve’. The pressure valve has two inlets ‘X’ and ‘Y’ and one outlet ‘A’.

o Timing function

Timing function in pneumatic system is done by a pneumatic timer.



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o Memory function

5/2 way directional control valve, air operated (double pilot valve.

Electrical signal processing (ex: relays) o Logic function

In electrical signal processing, two normally-open contact are connected in a parallel basis to produce an OR function.

o Timing function

Time relay (switch-on delay timing characteristic).



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Time relay (switch-off delay timing characteristic).

o Memory function

Dominating Reset Dominating Set

Electronic signal processing

In an electronic hard-wired-programmed control, contacts (N/O, N/C, etc) are replaced by electronic functional element. The sequence is determined by the functions of the modules (NOR, AND, etc) and the wiring, If alternations are required, the effort involved is considerable. In order to avoid these disadvantages, programmable logic control (PLC) were developed and built in the USA (1970).



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1.11 Actuator. - Definition: The signal from the processor are amplified if necessary and passed on to the actuators. The desired actions are finally carried out in a process by the actuators. These actions might for example, be the generation of movements, of works of the most varied types (mechanical, electrical, thermal) or of reports of important process statues, etc. - The motion generated by the actuators might be:

Linear motion o Ex: pneumatic cylinder

Rotary motion o Ex: Electric motor

Generation of large forces o Hydraulic cylinder

- Hydraulic is best suited for the generation of large forces. It may be used to control machines such as hydraulic presses, lathes and grinders and is commonly found in automation control systems.

- the generation of large forces involves the following energy conversion:

chapter1 intro to automation

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