There are three main methods of process control: batch, continuous, and discrete. Batch process control involves combining raw materials in fixed amounts for a set time and temperature. Continuous process control is used for never-ending processes like oil refining. Discrete process control produces specific items in a start-stop manner like car manufacturing. Process control systems use programmable logic controllers (PLCs) and proportional-integral-derivative (PID) control to monitor inputs like temperature and adjust outputs to meet preset values.

1. Process control By the end of the presentation you should be able to answer the following questions: Using examples, explain the different methods of process control systems Using an example, describe how PLC and PID work

2. Examples of where process control takes place: Oil refining Chemical processing Car manufacture Temperature control industries e.g. refrigeration plants such as meat factories Paper mills Food & beverage industries

3. Process control methods Batch process control Continuous process control Discrete process control

4. Batch process control Used in processes where there are specific amounts of raw materials that are combined together and mixed for a certain amount of time. Examples: Food processing such as ready made meals or Beverage processing such as coca-cola

5. Food Batch process control example: Ingredients are measured into a large vessel and mixed together for a fixed time at a fixed temperature. The computer controls: The amount of each ingredient is added The length of time for each stage The temperature for each stage

6. Continuous process control Used in processes that appear unending For example, where a process is continuous such as the refining process for petroleum Or, where is it necessary to maintain the same low temperature continually such as a refrigeration plant that processes meat Used to produce very large quantities of a product

7. Discrete process control Used to produce specific items Known as an On/Off or Start/Stop process For example, in car manufacturing, a robot arm has 1 job and so it will repeat the same job on many cars. (Starting and stopping with every new car)

8. TASK: What is an Open loop system? What is a Closed loop system? Closed Loop System : A control systems that carries on working continuously, they don’t just stop after one decision has been made. Open Loop System: Only looks at its input signal in order to decide what to do. It takes no account at all of what is happening to its output.

9. What controls these processes? Process control is overseen by: A Programmable logic controller (PLC), this is a type of computer or microcomputer

10. Programmable logic controller (PLC) A type of computer/microcomputer used for a single purpose Accepts analogue and digital inputs Uses a set of logic statement to compare input data with pre-set values Used where the pre-set values are constant such as refrigeration plant

11. The system/program used on the PLC computer/microcomputer: Proportional integral derivative (PID) Used with closed loop systems This is when a variable such as a temperature is being continually monitored using a sensor that is connected to the PLC (which compares the input with the pre-defined values) The PID is responsible for calculating the difference between the input and the pre-set value This is then used by the PLC to proportionally change the output to reach the pre-defined values The PID will continuously monitor the difference

12. Questions Describe the purpose of a programmable logic controller. Where are PLCs used in industry? What role does the PID play in the PLC? What are the advantages of PLCs? How have PLCs impacted on the workforce? 6. Then read the EWT article on the OLC & make notes 7. Print out your spreadsheet slide about the function given last lesson

13. Task Watch the videos on the OLC>Control Systems> Process Control Discuss and decide what methods of process is being used.

14. Embedded web technology (EWT) Developed by NASA So that experiments in space could be conducted by NASA staff anywhere in the world It integrates microprocessors, input sensors, output actuators and software needed to control these Example: There is an oven that can be controlled remotely from anywhere in the world. The embedded software can be accessed over the web and then used to control the over temperature Example: surgeons can monitor astronauts hearts from earth using EWT Read the NASA article on the OLC>Unit 2> Control