slide 1 standard grade computing automated systems

Standard Grade Computing

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Automated Systems


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Why Use Automated Systems?These are systems in which computers are used to control

machines and equipment. They are used because:

(a) they are fast. Computers react in fractions of a second. Machines under their control will act and react much quicker than ones controlled by humans.

(b) they can operate in dangerous environments. Eg North Sea oil platforms, chemical factories, nuclear power stations.

(c) they can cope with repetitive tasks without making mistakes or slowing down.


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(d) they are accurate. Automated systems follow instructions precisely and can thus guarantee 100% accuracy.

(e) they are efficient. Because they are accurate there is no waste and thus no time lost mending errors.

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(f) they are adaptable (can be used for different tasks). Automated systems can be designed to be flexible and handle a range of different tasks eg spray painting, welding

or carrying.


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Types of Automated systems(1) Robots

What Is A Robot?

• A robot is a machine which is controlled by a computer.

• Robots are FLEXIBLE because they can be REPROGRAMMED to perform different tasks. • A dedicated machine can only do ONE TASK.It is NOT REPROGRAMMABLE. eg A Washing Machine


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Robot Anatomy

ShoulderElbow

Wrist

End Effector

Waist


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Interface

Robots are connected to a computer by a device called an INTERFACE. The interface makes sure that the right messages are sent between the computer and the robot in a form that they can both understand.

INTERFACE


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CreditEnd Effector

• Tool attached to the end of a robot arm.• The part that carries out the function of the robot.

Example:Welding electrode, suction cup, paint spray, gripper, electromagnet.

LOOK UP - ‘Standard Grade Computing Studies’ p129 to see what some of these look like


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Stationary robotsThey are fixed in one spot to perform their task. Eg a stationary robot arm stationed at the side of a conveyor belt

welding parts onto a car body.

Mobile robotsThey are fitted with wheels or tracks and are powered by electric motors. A mobile robot might be used for transporting dangerous chemicals inside a chemical plant.


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(ii) Magnetic Guidance SystemsAn electric cable which gives off a magnetic field is set in the factory floor. The robot is fitted with magnetic sensors which can detect a magnetic field and feed the data to the control computer. The computer guides the robot along the correct path.

Sensors

Buried Wire

Magnetic Field


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There are two ways to make robots mobile:

(i) Light guidance systemThe path for the robot is set by a white line painted on the factory floor. A light source shines a light directly onto the white line. Light Sensors on either side of the light source detect and measure the amount of light reflected off the floor. If the amount of reflected light detected is uneven then robot is guided back onto the correct path.

Light Sensor Lamp Light Sensor


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Credit

Degrees of FreedomThe number of different ways a robot arm can move.

Example:

2 3

4

1

ShoulderElbow

Wrist

End Effector

Waist


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YAW, PITCH and ROLL are the terms used to describe the different types of movement made by the robot arm.


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Robots can be controlled by1. A Computer Program

The program is usually in a high level language. New programs can be written OFF-LINE. The advantage of this is that the robot is still working while the program is written. The robot can then be stopped and re-programmed to perform different tasks.

. 2. Lead-through programming

The human operator will lead the robot through the taskthat has to be done. The computer will store the movementsof the robot performing the task.

3. Remote controlUsing a joystick/keypad a human can control the robot arm and record each movement of the arm.


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Control of Automated Systems

Automated systems are controlled by instructions (software) stored in and sent out from a computer system. There are two types of control which can be used on any automated system:

1. Open loop In an open loop control system the processor is instructed to perform a task and it does not stop until it has finished the task. Example:dishwasher, washing machine etc..

Computer Machinecontrol

information


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Open loop control systems

• In an open loop system the processor is instructed to perform a repetitive task and doesn’t stop until it has finished.


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More open loop control systems

Washing Machine Toaster


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2. Closed loopA closed loop control system uses one or more sensors to detect what is going on around it, and it can change what it’s doing depending on the information it gets from the sensors known as feedback.

Computer

sensors detect action

machine takes action

Decision

feedback


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More closed loop control systems

• There are many different types of sensor that can be used for burglar alarms. All of them measure whether a person has entered or is about to enter a room. The most popular types of sensor for burglar alarms are door switches and infra-red detectors.

• Burglar Alarms


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• Door switches are fitted somewhere around the edge of the door. When the door opens, the switch signals to the computer, which sounds the alarm.

• Burglar Alarms

• Infra-red detectors detect invisible infra-red light. All warm objects give out infra-red light. The detector constantly looks for any movement of infra-red light. When a burglar moves in front of the sensor it signals to the computer which sounds the alarm.


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• Some greenhouses have computer-controlled equipment for growing crops such as strawberries all year round.

• Greenhouses

• Sensors measure the temperature inside the greenhouse. If the temperature is too high, the machine opens the windows.

• If the temperature is too low, the machine closes the windows and may switch on a heater. Watering, feeding and lighting can also be controlled automatically.


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Sensors

• Sensors can provide information to a robot about its surroundings.

• This allows the robot to respond to the changing environment.

Example: A robot picking up an egg will not crack it if it can monitor the pressure applied to the egg.


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Types of sensors:

(a) Pressure Sensors - used to sense pressure when handling objects, bumpers on mobile robots.

(b) Heat Sensors - used in places of extreme temperatures eg. furnace or refrigeration plant.

(c) Light Sensors - used to find light or lack of it.

(d) Optical Sensors - it is possible to identify very simple objects by ‘sight’ eg. squares.

(f) Magnetic Sensors - used to detect electromagnetic field around an underground cable for navigation.


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Sensors are devices which detect and measure levels of energy. Such measurements are known as analogue, because they vary continuously.

However, computers are digital devices.

0 1 1 0 1 0 0 1 0


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A sensor converts the analogue signal into an electrical signal.This varying electrical signal is converted into digital data by the interface. There are two types of interfaces:

Credit 1. Analogue to Digital (A/D)

Sensor A/D converter Computer

Analogue signal Digital signal

2. Digital to Analogue (D/A)

Computer D/A converter Machine

Digital signal Analogue signal


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Types of Converter

Transducer

A transducer is a device which changes an external physical input (temperature, pressure or light) into a digital signal.

Digitiser

A digitiser converts a visual image from a video or TV camera into digital form that the computer can process.


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A/D and D/A Converters

The A/D and D/A converters are commonly stored on a ROM chip. The converters are in constant use in an automated system and storing them permanently in ROM avoids the need for constant loading and storing operations between backing storage and RAM.

F/G/CReal Time ProcessingAs the signal from the sensor is converted into digital data it is fed into the processor which then checks the data immediately and responds to it..


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Simulation

A simulation is the imitation of a real - life system by a computer. Example: weather forecasting, where simulation can be used to predict likely developments in the weather pattern.

Advantages:• Mimic real - life situations for a fraction of the cost.• Allow people to practice dangerous manoeuvres

without any damage to them, others or machinery.Eg. training air plane pilots and nuclear power plant workers.


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CAD / CAM

Computer Aided Design (CAD)

This is a computer system used for commercial design workwhich consists of: a powerful computer, large high resolution colour monitor and a high quality colour plotter. Designers can create objects, plans or designs in 2 or 3 dimensions and store them on backing store. They can then be easily edited, rotated, viewed from different angles before being resaved or printed out.


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Computer Aided Manufacture (CAM)

This is the use of computer controlled machines to produce objects. The machines can be either a range of robots or Computer Numeric Controlled (CNC) machines used for cutting shapes from metal. Once instructions are fed to them they will accurately cut the required shape eg car body parts


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Implications For Automation

1. Social• Redundancies - computers are cheaper and quicker.• Retraining - new jobs: maintenance, installation, updating

hardware & software, managerial, supervisory etc.• Improved life style - more leisure time - no more boring, repetitive and dangerous jobs.• Health issues through prolonged use of computer: repetitive strain injury, eye strain etc..


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2. Technical(i) Safety

• Moving parts of machinery must be covered.• Area of movement of robot arm must be clearly marked with barrier.• Path for robot vehicle must be marked with separate path for humans.• Robot vehicles are fitted with collision detectors, lights and siren.

(ii) Quality controlUsing automated systems the quality of a product can be kept consistent.


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Credit

(iii) Systems Analyst

The tasks performed by a systems analyst when changing to an automated workplace include:

• Is the workplace suitable for automation?• Organise the layout of the workplace.• Consider safety of people and robots in the design.• Recommend hardware, including robots.• Recommend software.• Monitor, evaluate and improve process.


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(iv) Physical layout To design the physical layout of the factory the following details must be looked at:

• positioning of the robot arm• paths for the mobile robots• electrical or data communication wiring for the robot arms• necessary safety procedures connected with the new system.


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3. Economic(i) Cost

Initial cost: cost of installing an automated system.Replacement cost: update hardware & software.Running cost: maintenance, consumables, power.

Credit(ii) Manual system

Labour Intensive - low level of equipment and lots of staff. Wage rises, holidays, sick, strikes...

(iii) Automated systemCapital Intensive - high level of equipment and few staff. Substantial initial investment.


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(iv) Production increases due to:• increased speed of manufacture, accuracy and 24 hour operation. • decreased costs in terms of wages and waste.• high quality of goods produced.

This leads to savings in the long term.

slide 1 standard grade computing automated systems

Documents

interface slide

standard grade computing

washing machine slide

wire magnetic field

stationary robot arm

light sensors

magnetic guidance systems

mobile robots