Automation And Its Present Uses Computer Science Essay

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The word automation comes from the Greek word "automaton", is a self-operating machine. The word was coined in 1946 by the Ford Motors vice president, Dale S. Harder. He used it to describe automatic or semiautomatic machines which were used for assembly of automobiles. Sometimes these machines are also described as "robots". The big progress within computer and control systems has extended the definition of automation. Automation had existed for many years, using mechanical devices to automate small production tasks. By adding a computer the flexibility has increased which allows it to do almost any sort of task.

Definitions:

"Making products under the control of computers and programmable controllers. Manufacturing assembly lines as well as stand-alone machine tools (CNC machines) and robotic devices fall into this category." [1] 

Or

"The act of implementing the control of equipment with advanced technology; usually involving electronic hardware; "automation replaces human workers by machines" [2] 

Companies can save money because it does not need to pay for vacation days, paid days off and other benefits. In addition, many factories hire dozens of production workers for shift teams and need to close down on holydays. Industrial automation, however allows a factory to run 24 hours a day, 7 days a week and 365 days a year, without paying overtime. This alone can add up to significant savings. But they still need employers to monitor these huge automated manufacturing lines, but not nearly as many.

Types of Automation

Fixed Automation

Fixed automation can be used for making the same product over and over again, also moving objects from a machine to another one. The process will be done exactly the same every time. By building dedicated equipment which are low in flexibility you will have a high rate manufacturing process. It can be very difficult to make changes in the product design. The only sense of using fixed automation is if you know that your product life cycles are long.

The type of factory's using this ether has mass production or a continuous flow.

Example: A factory making toothpicks will have a mass production of the same toothpick, and the process will be the same every time.

Programmable Automation

Programmable automation is designed to have changeable sequence and configuration that can be changed by the machines electronic control. This is specifically suited for car producing.

This is also useful for small businesses that don't have the economy to run continuous production lines and factory's that makes season items. But every time reprogram the system is done, physically adjustments to the machine may have to be made. This will result in some lost production time.

Example: A certain car model has to me mass produced for at period of time, and the body shape is made exactly the same every time. But after a period it's replaced with a new model. Now the manufacturer only has to reprogram the robots on the production line.

Flexible Automation

In flexible automation, the production equipment is designed to make very fast changes. This is used when changes is made several times a day. The changes will be allowed by operators, and the changes is made fast to have as little idle time as possible. Normally you will have graphical interface, to make it easier for the operator.

Example: A palletizing system is an operation of loading objects such as a corrugated carton in different sizes on a pallet in defined patterns. Every time the carton size change, the operator only have to change the preprogrammed option on the control panel.

Where is it used

Industrial automation is used in all modern factories around the world, now only simple manufacturing processes. Within the manufacturing ambit, robots are used to do a task that doesn't require any form of rationalized intelligence. If the process is the same time after time, a robot may be more dependable then a human.

http://www.idro-expo.com/files/images/automotive/assemblyline/Samand-Line-01.jpgThey are also used a lot for pick & place applications. "Pick up part, put it in machine, take the part out and put it into next machine".

For example in the auto motor industry has seen a lot of changes the last many years, more and more robots are replacing workers on the assembly lines. They place the main structure, on the automated production line. Then the robots start welding all the parts onto the frame one by one, meanwhile transferred down a big conveyor belt. All of this used to be done manually but now it is all done by robots, and is done more accurate and in less time. Also the inspecting of the body is done by robots, by taking pictures of the frame and comparing them to a computer model.

Hardware

Alot of different hardware it used in industrial automation. In this part some of the some of the most widely used hardware will be described.

PLC

Back in the 60's, a growing demand on flexibility rising. The car manufactures need a new control system for the production machines, which would be able to replace existing relay and logic control.

http://deao.en.ecplaza.net/1.jpgThe desired control system should meet the following main requirements:

Programmable control for flexibility for rapid conversion of production equipment. Vis med latinske bogstaverControls must function smoothly in an industrial environment. RVis med latinske bogstaverequirements for temperature, dust and dirt, supply voltage must be minimal. Input/output signals must be digital and voltage should be within the typical industrial area (24V DC to 230V AC). Furthermore, the control should be able to deal with analog input / output signals and to be modular so that an expansion or replacement can be quick and simple.

Programming of the control must be simple, quick to be change and general user-friendly.

The result was a PLC, Programmable Logic Controller, which was designed to work in an industrial environment, and connected to production equipment from input and output modules.

That a PLC is programmable means that by using a programming device for programming the controller system.

Logic controller system means that the logical core functions AND, OR and NOT can be programmed.

Besides these, also the following bit instructions:

Timer

Counter

Flip-Flop

Shift registers

And a lot more.

Today PLC control systems are an integrated part of almost all automatic control. Since the first PLC in the seventies, there has been an enormous development both technically and economically, so that we now have a product with a significantly greater capacity than before.

PLCs have a greater performance, storage capacity, speed, number of inputs and outputs, processing of analog signals, programming devices and communication between different devices.

At the same time, the price of each product has lowered, and this makes an economic benefit even with small automation tasks.

The PLC can be divided into six main function blocks:

Programming

Terminal

Power Supply

PLC

Output

Program and data memory

CPU

Input

Power Supply

The power supply changes voltage typically from 230V AC to a 24V DC, which is used internally in the PLC to supply the individual blocks.

CPU

Central Processing Unit - is the most important unit, this is where all functions are performed. It is here the microprocessor is located. The microprocessor performs calculations, communicates with other blocks and manages program executions.

Program and data memory

Different types of memory blocks are needed for the CPU to run a program. Memory can be regarded as a dresser with a number of drawers. In these drawers data is being read/written, which is necessary for the program execution.

System Memory

In this memory, data is stored that gets the microprocessor to run / understand a written program. This memory was developed by the manufacturer and is called a static memory. This means that this memory only can be read and that data is retained during power failure.

Data Memory

The microchip needs a memory to store internal data as intermediate results, timer values, auxiliary relays etc. during program execution. This memory is a dynamic memory, which means that it can be both read and written by the microprocessor.

Program Memory

There is the part of memory which a user through a programming unit has access. This is there you saved the instructions that the user wants the PLC to perform.

Input/output

The interface between the PLC and the machine/process is designed to adapt the process voltage to the PLC.

Input

Input interface process and translate input signals into so that they a usable by the PLC. Input devices can consist of digital or analog devices. A digital input card handle devices that either gives a signal that it is on or off such as a limit switch, pushbutton, photo sensors or sensors. An analog input card converts a voltage or current (e.g. a signal that can be 4 to 20mA), and turn it in to a digital number. Examples of analog devices are flow meters, pressure transmitters and temperature transmitters.

Output

Output interface translates PLC output signals to signals that the process can use. Devices can also consist of digital or analog types. A digital output card is used for turning a device on or off such as lights, relays, alarms and valves. An analog output card will convert a digital number received from CPU to an analog voltage or current. Typical outputs signals can range from 4-20mA and are used to drive mass flow controllers and pressure regulators etc.

The reason why the common range for analog in-/outputs is 4-20 mA, is that if it was 0-20 mA, the zero may be because of a wire break.

Programming Terminal

To program a PLC requires a programming terminal and special software from the PLC manufacturer. Programming terminal can be a dedicated terminal or a normal computer. The most widely used for of programming is ladder logic. Ladder logic uses symbols, instead of words, the symbols looks like the symbols you would have in relay logic control. A finished program will look like a ladder but actuality it is an electrical circuit. The completed program is downloaded from the PC to the PLC using a special cable that's connected to the front of the CPU. The CPU is put into run mode, and then starts scanning the ladder logic program.

Example on a ladder program:

Assume that S1 is the "start" button, B1 is the "stop" button and C is the output that tells the motor to run. Imagine power flowing through the ladder logic example. In this example when the operator presses the "Start" button (labeled S1) power will flow through the contact. The ]/[ contact means "not on" or off. So assuming that the "stop" button (labeled B1) is not pressed then power will flow through the B1 contact and power the output labeled M1 and turn on the motor.

Note the contact labeled M1 below the contact labeled A. This is called a "seal" circuit since contact M1 "seals" in contact S1. Remember the power flow analogy. If it was only the top row: S1, B1, and M1 then every time the operator took their finger off the "start" button (contact S1) then the motor would stop. But contact M1 is placed in parallel with contact S1 so that once the output M1 turns on then the input M1 is turned on in parallel with contact S1. Therefore the only way to stop the motor is to press the "stop" button (contact B1).

Variable-frequency drive

Frequency Converters can be divided into two types, static- and rotating frequency converter. The rotary frequency converter consists in principle of a generator that is driven by a motor. It is possible to produce higher frequency, if the drive motor has less polpar than the generator.

Since the late '60s, the static frequency converter had an incredibly rapid development. The development of microprocessors and semiconductor technology, along with the price of these units led to a major advance in the field frequency converters.

The static frequency converter is exclusively composed of electronic components. It as contains the word static says no moving parts and therefore maintenance free.

The frequency converter can be divided into three main components:

Rectifier circuit

The Single- and three phase rectifier converts an AC voltage to a pulsating DC voltage. It can be either constructed of diodes, thyristors or both. There are two basic types of rectifiers - controlled and uncontrolled. A rectifier consisting of diodes is uncontrolled. A rectifier, which consists of thyristors is controlled. If diodes and thyristor is combined, then the rectifier is half-driven.

Fixed DC Voltage

The between circuit can be considered as a storage facility from which the engine can draw its energy through the inverter. The between circuit can be constructed after three different principles and which type depends of the rectifier and inverter, which the circuit is built with.

Variable DC current

This type consists of a very large coil and can only be combined with the controlled rectifier. The Coil converts the variable voltage from the rectifier circuit to a variable dc voltage. The load determines the size of the motor voltage.

Constant DC voltage

This circuit may consist of a filter which capacitor and coil. Also it can be combined with both types of rectifiers. The filter smooth's the pulsating DC voltage in rectifier.

In a controlled rectifier, voltage is maintained constant at a given frequency. The voltage supplied to the inverter is DC voltage with variable amplitude.

In uncontrolled rectifiers is the voltage supplied to the inverter a dc voltage with constant amplitude.

Variable DC voltage

In this circuit a chopper added in front of the filter. The chopper includes a transistor, which acts as a switch, so the rectifier voltage can be switched on and off. The control circuit regulates the chopper by comparing the variable voltage after the filter with input signal. If there is a difference, ratio adjustments will be made to when the transistor is on or off. The DC voltage effective value becomes variable, and its size depends on the length of time during which the transistor is open.

The filter capacitor and coil keeps the voltage constant at a given frequency.

Inverter circuit

The inverter circuit is the last part in the drive before the engine. It is here that the final adjustment of output voltage occurs.

The Frequency converters ensure good operating conditions throughout the control range by adjusting the output voltage to the load conditions.

The inverter ensures that the supply to the motor is a variable size. This means that it is in the inverter, the motor voltage frequency is generated. Control of the inverter depends on what is received, a variable or a constant volume.

If the voltage or current is variable, then the inverter only has to produce the frequency. If the voltage is constant, the inverter is used to generate the variable frequency and voltage.

Control circuit

This is the part which controls all the circuits in the frequency converter.

Today, the control circuit is built from digital components around a microprocessor. The processor controls the output voltage as well as frequency, it also monitors the engine's consumption. With the introduction of a microprocessor, it has been possible to program a quantity values and thereby adjust the frequency converter for different modes of operation and engines.

Here are some of the most common features:

Engine Data

Here you set the size of the engine's power output. Some frequency converters know a number of standard motors and can be based on efficacy information even suggest the rest of the motor data information. It is only necessary to modify the other engine data, if the engine deviates from the standard. Some of the other data's on the engine is full load current, voltage and frequency.

If the engine deviates from a standard engine, it may also be necessary to adjust the voltage-frequency relationship for a sensible operation.

Operating Data

Here you set the highest and lowest frequency, how long and how much congestion is acceptable. Also slip compensation, so the engine includes a nearly fixed speed independent of load, ramp times to achieve soft start and brake.

Control data

Control circuitry is equipped with a number of inputs and outputs, both digital as analog. Normally the digital inputs are used for start, stop and reverse the engine, and analog input is normally used for controlling the frequency with. These analog inputs are mostly of a current or voltage type. 0-20 mA or 4-20 mA has become a widely accepted industry standard. When it is voltage, 0-10 V is seen as a generally accepted standard.

Control circuitry is also equipped with a number of outputs, these are used to get a return call from the frequency converter. For example: current frequency, motor overload and disconnections because of errors.

Conclusion

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