1prepared by: mazhar javed awan control although many people assume that businesses mainly use...

1Prepared by: Mazhar Javed Awan

ControlControl Although many people assume that Although many people assume that

businesses mainly use computers in businesses mainly use computers in offices offices to help workersto help workers to perform administrative to perform administrative tasks, they also have many other uses in the tasks, they also have many other uses in the workplace.workplace.

For exampleFor example, computers can be used to , computers can be used to control many different types of machinery, control many different types of machinery, including industrial robots.including industrial robots.

Components of Computer ControlComponents of Computer Control A computer (or microprocessor). A computer (or microprocessor). Some sensors to Some sensors to enable the enable the

computer to detect quantitiescomputer to detect quantities such as temperature or pressure. such as temperature or pressure.

Some devices for the computer to Some devices for the computer to turn on and off. turn on and off.

An interfaceAn interface to connect the to connect the sensors and devices to the sensors and devices to the computer. computer.

Some Some software to read datasoftware to read data from from the sensors and turn the devices on the sensors and turn the devices on and off. and off.


RobotsRobots An An industrial robotindustrial robot is ‘a is ‘a

reprogrammable, multi-functional reprogrammable, multi-functional manipulator designed to move manipulator designed to move material, parts, tools or material, parts, tools or specialised devices through specialised devices through various programmed motions for various programmed motions for the performance of a variety of the performance of a variety of tasks’.tasks’.

Uses:Uses: To To spray paintspray paint or for welding or for welding

body panels.body panels. Washing machineWashing machine is restricted to is restricted to

washing clothes.washing clothes.


Industrial RobotsIndustrial Robots Industrial robots are comprised of Industrial robots are comprised of

three parts:three parts: The manipulatorThe manipulator – this is the moving – this is the moving

‘arm’ to which various tools can be ‘arm’ to which various tools can be attached.attached.

The power supplyThe power supply – usually a – usually a hydraulic compressor (for robots that hydraulic compressor (for robots that need lots of strength) or electrical need lots of strength) or electrical generator (for lightweight robots).generator (for lightweight robots).

The controlling computerThe controlling computer – which – which controls the robot.controls the robot.


Why use Robots Why use Robots

They can They can repeat tasksrepeat tasks in exactly the same way in exactly the same way each time each time

As long as they have power, they As long as they have power, they never tirenever tire They can They can survive in placessurvive in places where people can't where people can't They can They can carry out tasks too dangerouscarry out tasks too dangerous for for

people people They They never get borednever get bored when they repeat the when they repeat the

same task over and over same task over and over They have They have many types of sensorsmany types of sensors to gather to gather

and process data and process data


RobotsRobots The controlling computer uses a very low The controlling computer uses a very low

electrical current and requires an interface to electrical current and requires an interface to allow it to work with the other parts of the allow it to work with the other parts of the robot.robot.

The The interface also allows conversioninterface also allows conversion from from digital to analogue and analogue to digital.digital to analogue and analogue to digital.

Robots on the moveRobots on the move When robots move from one place to When robots move from one place to

others ,then there are following others ,then there are following problemsproblems.. How are How are robots able to navigaterobots able to navigate themselves? themselves? How do How do robots avoid collidingrobots avoid colliding with each with each

other?other? How is the How is the power providedpower provided??


Robots how to solve Robots how to solve problemsproblems

Sometimes robots Sometimes robots need to move from one need to move from one location to anotherlocation to another (e.g. robotic fork lift (e.g. robotic fork lift trucks in an automated warehouse).trucks in an automated warehouse).

These robots require These robots require self-contained power self-contained power sourcessources (e.g. batteries) and additional (e.g. batteries) and additional autonomy (i.e. the ability to make simple autonomy (i.e. the ability to make simple decisions based on limited information).decisions based on limited information).

Also Also keep a recordkeep a record of the distance they of the distance they have travelled and the angles they have have travelled and the angles they have turned through.turned through.

On each robot there is an On each robot there is an ultrasonic ultrasonic detectordetector ,which emits a beams of infrared ,which emits a beams of infrared radiation.If anything gets in the way of the radiation.If anything gets in the way of the beam, the robot just stops. beam, the robot just stops.


SensorsSensors

A sensor is something which A sensor is something which can can measure physical quantitiesmeasure physical quantities in the in the surrounding environment.surrounding environment.

Robots need informationRobots need information as well as as well as programming in order to function. This programming in order to function. This information is provided by sensors.information is provided by sensors.

An example might be a An example might be a heat sensorheat sensor which measures the temperature in a which measures the temperature in a room or a pressure sensor which senses room or a pressure sensor which senses when someone has walked over it.when someone has walked over it.

. .


SensorsSensors

The types of sensors required by The types of sensors required by robots include:robots include: Mercury tilt switchesMercury tilt switches – these are – these are

switches that sense titling movement.switches that sense titling movement. Light sensorsLight sensors – these are sensors that – these are sensors that

detect different levels of light and dark.detect different levels of light and dark. Push switchesPush switches – these are switches – these are switches

that operate when something is opened that operate when something is opened or closed (e.g. the switch that controls or closed (e.g. the switch that controls the light in a fridge is a push switch).the light in a fridge is a push switch).


SensorsSensors Temperature sensorsTemperature sensors – these detect – these detect

changes inchanges in the temperature.the temperature. Sound sensorsSound sensors – these detect different – these detect different

levels and frequencies of sound.levels and frequencies of sound. Proximity sensorsProximity sensors – these detect how – these detect how

close something is or if something is being close something is or if something is being moved away.moved away.

Position sensorsPosition sensors – these detect the angle – these detect the angle between one part of the robot arm from between one part of the robot arm from another.another.

pH sensorspH sensors – these detect how acidic – these detect how acidic something is.something is.

Humidity sensorsHumidity sensors – these detect how – these detect how much moisture is present in the atmosphere or much moisture is present in the atmosphere or in a sample.in a sample.


Sensors Measures Where to used

Heat Temperature Living room for central heating system

Humidity Water vapour in the air Swimming pool, greenhouse

Infra-red Infra-red radiation e.g. body heat Security alarm systems

Light Light levels External security lights

PH Acid/alkali levels e.g. pH of soil Environmental experiments, river pollution

Pressure Pressure Burglar alarm systems, automatic doors

Smoke Smoke in the atmosphere Offices

Sound Levels of sound Security alarm systems

Tilt Angle of tilt Windows in security alarm system

Touch Detects if one object bumps into another Computer controlled robots

Sensor MeasurementsSensor Measurements


The interfaceThe interface

Name given to the hardware and Name given to the hardware and associated software needed to peripheral associated software needed to peripheral units and computers.units and computers.

The The sensors feed their informationsensors feed their information to to the controlling computer via the interface.the controlling computer via the interface.

The interface also The interface also feeds commandsfeeds commands to to the manipulator from the controlling the manipulator from the controlling computer.computer.

The information from the sensors and the The information from the sensors and the commands to the manipulator usually commands to the manipulator usually pass through a buffer.pass through a buffer.


The bufferThe buffer The buffer The buffer stores datastores data (information coming in or (information coming in or

commands going out) so that the speed of data commands going out) so that the speed of data transfer is at a level that the various parts of the transfer is at a level that the various parts of the robot can cope with.robot can cope with.

For example, if data transfer was too quick, the For example, if data transfer was too quick, the controlling computer might commandcontrolling computer might command the the manipulator to do something new before it has manipulator to do something new before it has completed a previous task.completed a previous task.

This could be very dangerous and could cause the This could be very dangerous and could cause the manipulator’s actuatorsmanipulator’s actuators (special electrical motors (special electrical motors that act like the manipulator’s muscles) to burn that act like the manipulator’s muscles) to burn out.out.

This is a particular problem with stepper motors This is a particular problem with stepper motors (an actuator that can be moved only a very small (an actuator that can be moved only a very small amount, or very slowly, or very quickly, or amount, or very slowly, or very quickly, or forward or in reverse).forward or in reverse).


ActuatorActuator An actuator is often part of a An actuator is often part of a

computer control system.computer control system. The actuator is a mechanical device The actuator is a mechanical device

or motor or motor which carries out the which carries out the action or decision made by the action or decision made by the control systemcontrol system. .

For example, in a greenhouse, For example, in a greenhouse, sensors may measure the sensors may measure the temperature. When the temperature. When the temperature rises too much, the temperature rises too much, the control system will send a signal to control system will send a signal to open the windows or vents. open the windows or vents.

The actuator is the motor which will The actuator is the motor which will open the vents. Likewise, when the open the vents. Likewise, when the temperature drops, the control temperature drops, the control system will send a message to the system will send a message to the actuator (motor) to close the vents.actuator (motor) to close the vents.


Stepper MotorStepper Motor

Is a motor Is a motor which turns in series of which turns in series of small stepssmall steps..

Pulse Pulse sent from the computer sent from the computer instructinstruct the motor to turn through the motor to turn through the required angle.the required angle.

Can also be Can also be sped up or slow down sped up or slow down or reverse or forward direction.or reverse or forward direction.

To To connect a stepper motor to connect a stepper motor to computercomputer, we use a buffer., we use a buffer.

Stepper motor Stepper motor used in robot armsused in robot arms..


Computer controlComputer control

There are various types of computer There are various types of computer control.control.

These include:These include: Open-loop control.Open-loop control. Close-loop control.Close-loop control.


Open-loop controlOpen-loop control The first type, Open Loop System, The first type, Open Loop System, only looks at its input only looks at its input

signalsignal in order to decide what to do. in order to decide what to do. It It of what is happening to its output. of what is happening to its output. An open-loop control program assumes that commands, when An open-loop control program assumes that commands, when

given, given, take affect.take affect. If a robot If a robot arm is given a command to move and something arm is given a command to move and something

stopsstops it, an open-loop control program will act as though the it, an open-loop control program will act as though the arm has moved.arm has moved.

In open-loop control, In open-loop control, output does not affect inputoutput does not affect input.. Examples of 'open-loop' systems:Examples of 'open-loop' systems: a) You a) You set the microwave oven to runset the microwave oven to run for two for two

minutes. After cooking for two minutes, the control minutes. After cooking for two minutes, the control system turns the microwave off. It has no idea system turns the microwave off. It has no idea whether your food is still frozen, burnt or cooked whether your food is still frozen, burnt or cooked perfectly.perfectly.

b) You b) You program the video recorder to start program the video recorder to start recordingrecording the football game at 7.30pm. However, the football game at 7.30pm. However, because the news program finished early, you miss because the news program finished early, you miss the first vital 15 minutes of the match. Because the the first vital 15 minutes of the match. Because the system is only checking its input(time), it had no idea system is only checking its input(time), it had no idea that the starting time of the match had changedthat the starting time of the match had changed. .


Closed-loop controlClosed-loop control A closed-loop A closed-loop control program uses control program uses

feedbackfeedback to check that its commands have to check that its commands have taken affect.taken affect.

Definition:Definition: Feedback is Feedback is where the outputwhere the output of of a system affects the input.a system affects the input.

The feedback from The feedback from sensors attached to a sensors attached to a robot armrobot arm informs the program of the arm’s informs the program of the arm’s actual position, and if something has stopped actual position, and if something has stopped the arm from moving, the program will take the arm from moving, the program will take remedial action (e.g. display a warning remedial action (e.g. display a warning message).message).

When this When this happens instantly this is called happens instantly this is called ‘real time‘real time controlcontrol

This stage is called processing. The computer This stage is called processing. The computer can only follow the can only follow the rules that it has rules that it has programmed into the controlprogrammed into the control system, it system, it cannot make its own decisions.cannot make its own decisions.

ExampleExample: computer : computer disk drive may use of disk drive may use of feedbackfeedback


Process ControlProcess Control

Once the input data from the sensors has been Once the input data from the sensors has been received by the computer, it can then begin to received by the computer, it can then begin to process it.process it.

The data will be The data will be compared against a set of rulescompared against a set of rules which have been programmed into the control system which have been programmed into the control system and a decision will be made. This stage is called and a decision will be made. This stage is called processingprocessing. .

The The computer can only follow the rules that it computer can only follow the rules that it has programmedhas programmed into the control system, it cannot into the control system, it cannot make its own decisions.make its own decisions.

Process Control is Process Control is usedused in nuclear power stations, oil in nuclear power stations, oil refineries and in the chemical industries.refineries and in the chemical industries.

Various sensors are used to relayVarious sensors are used to relay the electronic the electronic signals back to computerssignals back to computers


The advantages of The advantages of computer controlcomputer control

Can Can operate 24 hours a dayoperate 24 hours a day without taking a without taking a break. break.

Can Can work without holidayswork without holidays or sick days or sick days Will Will work without any wageswork without any wages. . Will Will repeat actions over and overrepeat actions over and over and over and over

again again Can Can process data from sensorsprocess data from sensors very quickly very quickly Can take Can take account of hundreds of inputsaccount of hundreds of inputs at at

the same time the same time Can make Can make reliable and accurate decisionsreliable and accurate decisions Can be Can be used in used in dangerous or awkwarddangerous or awkward

environments where it wouldn't be a good idea environments where it wouldn't be a good idea to send humans to. to send humans to.

Changes can be madeChanges can be made by quickly by simply by quickly by simply reprogramming the systemreprogramming the system


The disadvantages of The disadvantages of computer controlcomputer control

There are There are high initial costshigh initial costs because computer- because computer-controlled are more expensive to buy and set up.controlled are more expensive to buy and set up.

Fewer workers will be employedFewer workers will be employed if computer- if computer-controlled systems are introduced, thus leading to a controlled systems are introduced, thus leading to a rise in the numbers of people who are unemployed.rise in the numbers of people who are unemployed.

The The software for the control system is specialistsoftware for the control system is specialist and may cost a lot of money to develop and may cost a lot of money to develop

If the computer malfunctions the If the computer malfunctions the system will not system will not workwork

If there is a If there is a power cut the system will not workpower cut the system will not work The The computer can’t react to unexpected eventscomputer can’t react to unexpected events

like a human could. It can only respond in the way it like a human could. It can only respond in the way it has been programmed to. has been programmed to.

It It can cause some concern if total controlcan cause some concern if total control for a for a system and the decisions are handed over to a system and the decisions are handed over to a computer. computer.


Examples of Computer Examples of Computer ControlControl

At homeAt home Washing machines Washing machines Microwave cookers Microwave cookers Dishwashers Dishwashers Electric kettles Electric kettles Fridges Fridges Video recorders Video recorders Remote control television Remote control television Central heating systems Central heating systems Burglar Alarm system Burglar Alarm system External Security lights External Security lights



At workAt work Air conditioning systems Air conditioning systems Lifts Lifts Automatic doors Automatic doors Factory robots Factory robots



Outside the homeOutside the home Traffic light systems Traffic light systems Car park barriers Car park barriers Cars – engine management systems Cars – engine management systems Lifts Lifts Rides at theme parks Rides at theme parks Computer controlled lighting systems at Computer controlled lighting systems at

discos and concerts discos and concerts Remote controlled car Remote controlled car


Simple Greenhouse Simple Greenhouse Temperature Control Temperature Control

SystemSystem A greenhouse temperature control system A greenhouse temperature control system

consists of :consists of : A temperature sensor. A temperature sensor. A heater. A heater. The system is used to keep the The system is used to keep the

temperature of the greenhouse above temperature of the greenhouse above 20°C. If the temperature drops below 20°C. If the temperature drops below 20°C then a heater is turned on to warm 20°C then a heater is turned on to warm the greenhouse up. the greenhouse up.

Input and Output DevicesInput and Output DevicesInputInput OutpuOutputt

Temperature SensorsTemperature Sensors HeateHeaterr

1prepared by: mazhar javed awan control although many people assume that businesses mainly use...

Documents

use robots

controlling computer

lightweight robots

mazhar javed awan robots

specialised devices

administrative tasks

variety of tasks

mazhar javed awan control