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 within the equipment.

Control systems A control system manages the behaviour of a device. Examples:

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 Dial Touch screen Sensors Microprocessor Actuator (a device that sends a signal to activate an output device)

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 analogue format) to a convertor. STEP 5: ADC (Analogue to Digital Convertor) converts data from analogue to digital. STEP 6: Convertor sends the digital data to the 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.

Learning Objectives Today we will Learn: What is meant by process control The differences between batch, discrete and continuous process control

Discrete vs Continuous Process Control Discrete Process control is used when specific items are produced. It 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.

Discrete vs Continuous Process Control Continuous process control is used in processes which appear to be unending. For example, maintaining the temperature in a room

Discrete vs Continuous Process Control 3. Batch process control Used in processes where specific amounts of raw materials are combined together and mixed for a certain length of time. E.g. food manufacturing The amount of each ingredient added is controlled by the computer, length of time for each stage and the temperature.

PLC A programmable logic controller is a digital computer that accepts analogue and digital inputs and compares inputs with the pre-set values. Depending on the results, it activates the output devices. A PLC is used only for a single purpose such as operating a machine.

PID Controller A PID is used for programming a PLC A proportional–integral–derivative controller A PID is used for programming a PLC It does the comparison and calculates the difference between the input value and the pre-set value and makes the PLC to activate an output.

PID Controller A proportional–integral–derivative 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.

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.

Air Conditioning System Touch screen is used to input the required temperature Temperature sensor collects data about the room temperature The temperature sensor sends data to the analogue to digital convertor The convertor converts the analogue data into digital format The convertor sends the data to the micro-processor The microprocessor compares the temperature of the room to the preset value 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 If temperature of the room is below the pre-set value the fans remain/switched off by the microprocessor

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

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

Intensive Care Sensors monitor the patients heart rate, pulse rate, body temperature, blood pressure The computer is pre-set with normal range of values which is compared with the ones fed back by the sensors CONVERSION 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

Process Control Process control is the use of microprocessors or computers to control a process. It is used in: Chemical processing Car manufacture Temperature control Food and drink industries

Computer Controlled ROBOTS in car manufacturing

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 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 1)What are robots? 2) Give examples of areas in which robots are used 3) Give examples of robots 4) Advantages and disadvantages of using robots 5) Ethical issues related to robots 6) Components that make robots

Advantages of Computer Control Can operate 24 hours a day without taking a break. Can work without holidays or sick days Will work without any wages. Will accurately repeat actions over and over again Can process data from sensors very quickly Can take account of hundreds of inputs at the same time Can make reliable and accurate decisions Can be used in dangerous or awkward environments

Disadvantages of Computer Control The software for the control system is specialist and may cost a lot of money to develop If the computer malfunctions the system will not work If there is a power cut the system will not work The computer cannot react to unexpected events as perhaps a person could. It can only respond in the way it has been programmed.

Robots

Robots

Robots

Robots