Learning Objectives Today we will Learn: What is meant by a Control System Examples of Control systems How control systems work

Control systems A control system is any device that has a processor or microchip embedded with the equipment.

Control systems A control system manages the behaviour of a device

Control systems At home Washing machines Dishwashers Burglar Alarm system

Control systems Outside the home Car park barriers Lifts Computer controlled lighting systems at discos and concerts

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

Parts of a control system

Pre-set Values STEP 1: The microprocessor stores a pre-set value input by the user via a touch screen, dial or knob

Sensors Sensors play a major part in control systems STEP 2: Sensors collect data from the environment An example might be a Temperature sensor that measures the temperature in a room

Sensors STEP 3: Once sensors have taken a reading or measurement, they send that reading straight back to the micro-processor

Sensors But the micro-processor cannot understand the signal sent from the sensor WHY??

Sensors STEP 4: Sensors send measured data (in analog format) to a convertor. STEP 5: ADC (Analog to Digital Convertor) converts data from analog to digital. STEP 6: Convertor sends the digital data to Microprocessor.

Processing STEP 7: Once the input data from the sensors has been received by the computer, the micro- processor can compare it with the pre-set value and decide what it needs to do. For example switch something on or off.

Output STEP 8: Once the processing has taken place and a decision has been made, the computer will send the correct signal to the actuator or output device. For a central heating system, this might be to turn the heating on or off. For a greenhouse watering system this might be to turn the sprinklers on or off.

PLC A programmable logic controller is a digital computer used for automation of e.g. machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines.

PLC A programmable logic controller is a digital computer used for automation of e.g. machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used for a single purpose/one program It accepts analogue and digital inputs and compares them with pre-set values. There is no human input – only sensors Depending on the results it activates the output devices

PID A (proportional–integral–derivative controller) is used to program a PLC It calculates the difference between the input value and the pre-set value It then makes proportional changes to the output so that the pre-set value is eventually reached rather than just turning the output device on or off it turns it on or off for a short-time then checks the output with the pre-set value. This is repeated until the desired value is reached.

PID Controller “we want the heating and cooling process in our house to achieve a steady temperature of as close to 22°C as possible” The Setpoint (SP) is the value that we want the process to be. The PID controller looks at the setpoint and compares it with the actual value of the Process Variable (PV). The PID controller in our Heating and Cooling system looks at the value of the temperature sensor in the room and sees how close it is to 22°C. A proportional–integral–derivative controller

PID Controller If the SP and the PV are the same – then the controller doesn’t have to do anything, it will set its output to zero. However, if there is a disparity between the SP and the PV then the action will either be cooling or heating depending on whether the PV is higher or lower than the SP

PID Controller Let’s imagine the temperature PV in our house is higher than the SP. It is too hot. The air-con is switched on and the temperature drops. The sensor picks up the lower temperature, feeds that back to the controller, the controller sees that the “temperature error” is not as great because the PV (temperature) has dropped and the air con is turned down a little. This process is repeated until the house has cooled down to 22°C and there is no error.

EWT Embedded web technology Combines microprocessors, input sensors, output actuators, control software, Internet and the Word Wide Web The devices that use EWT can control any device from the internet For example, turning on/off and adjusting the temperature for an oven using a computer or portable device

Air Conditioning System 1.Touch screen is used to input the required temperature 2.Temperature sensor collects data about the room temperature 3.The temperature sensor sends data to the analogue to digital convertor 4.The convertor converts the analogue data into digital format 5.The convertor sends the data to the micro-processor 6.The microprocessor compares the temperature of the room to the preset value 7.If temperature of the room is above the pre-set value the fans remain on/are switched on by the microprocessor or microprocessor increases their speed 8.If temperature of the room is below the pre-set value the fans remain/switched off by the microprocessor

Central Heating System 1.A number pad is used to input the required temperature. 2.Temperature sensor monitors temperature of room 3.Data from the sensors is converted to digital (using an ADC) 4.The convertor sends the digital signal to the micro- processor 5.Microprocessor compares temperature data from the sensor with the pre-set value 6.If the temperature is higher/lower than preset value a signal is sent to the actuator 7.if lower microprocessor/actuator switches the heater on 8.if higher microprocessor/actuator switches the heater off

Refrigeration 1.A knob allows users to set the desired temperature 2.Temperature sensor monitors temperature of the fridge 3.The temperature sensor sends data to the analogue to digital convertor 4.The convertor converts the analogue data into digital format 5.The convertor sends the data to the micro-processor 6.Microprocessor compares temperature data from the sensor with the pre-set value 7.If the temperature is higher/lower than preset value a signal is sent to the actuator 8.if lower microprocessor/actuator switches the cooler on 9.if higher microprocessor/actuator switches the cooler off

Intensive Care 1.Sensors monitor the patients heart rate, pulse rate, body temperature, blood pressure 2.The computer is pre-set with normal range of values which is compared with the ones fed back by the sensors 3.Microprocessor compares the data from the sensors with the pre-set values 4.If the data received is higher/lower than the pre-set value then the computer sounds an alarm

Discrete vs Continuous Process Control 1.Continuous Process Control is an on/off or start/stop process for example fitting the wheels on cars by robots. Robots stops and when the next car comes the process is repeated. 2.Continuous process control is used in processes which appear to be unending. For example, maintaining the temperature in a room

Computer Controlled ROBOTS in car manufacturing

A robot arm consists of 7 metallic sections with six joints, each joint being controlled by a separate stepper.

Computer Controlled ROBOTS in car manufacturing Robots can perform the following jobs on a car production line: Painting car bodies Putting on car wheels Drilling the holes in car bodies Tightening bolts Assembling the electric circuits Inserting car engines

Computer Controlled ROBOTS in car manufacturing A robot arm has many different end effectors so that a variety of jobs can be carried out. These are the devices attached to the end of the robot arm. For example: Cameras to inspect work Grippers to pick parts and place them somewhere Welding guns Vacuum cups to pick up delicate objects Drills to make holes in the car body Screwdrivers Spray guns Sanders to produce a shiny finish

Computer Controlled ROBOTS in car manufacturing Advantages of using robots: A robotic arm has greater accuracy than a human The running costs are lower compared with paying a person Robotic arms don’t get tired, so work is of a consistent standard The whole process can be continuous, without having to stop at shift change overs

Robots

Smart Homes home-automation.html Define the term smart home What is the back bone of a smart home? Describe how one of the controllers work (e.g. X10) Describe wearable technology and it’s uses (e.g. SFIT) Write down the hardware and software needed to make smart homes work Summarise the benefits and drawbacks of smart homes