W1 intro to process control

What is a process

A process is anything that takes inputs does something to them and produces outputs

What is control

Control means measuring something important and adjusting something else to keep it where you want

What is process control

Process control is keeping an important variable at a desired value despite disturbances

Why is process control needed

Process control is needed for safety product quality efficiency and environmental protection

What is a controlled variable CV

The controlled variable is the quantity you want to keep at a specific value

What is a setpoint SP

The setpoint is the desired value of the controlled variable

What is a sensor

A sensor measures the controlled variable

What is a controller

A controller compares the measured value to the setpoint and decides what action to take

What is a manipulated variable MV

The manipulated variable is what you adjust to control the process

What is an actuator

An actuator is the physical device that changes the manipulated variable

What is a disturbance

A disturbance is anything that pushes the process away from the setpoint

What is a batch process

A batch process runs with a fixed amount of material then stops and is emptied

Give a real life example of a batch process

Cooking pasta washing clothes or brewing beer

What is a continuous process

A continuous process runs all the time with constant input and output flow

Give a real life example of a continuous process

A shower or a heat exchanger

What is steady state

Steady state is when process variables do not change with time

What is dynamic behaviour

Dynamic behaviour is when process variables change with time

What is a mass balance

A mass balance accounts for what goes in what goes out and what builds up

State the mass balance idea in words

What goes in minus what goes out equals what accumulates

What is accumulation

Accumulation is material that builds up inside the system

What is a non reactive system

A non reactive system has no chemical reactions and only mixing heating or cooling

Give an example of a non reactive system

Mixing hot and cold water or blending liquids

What is a reactive system

A reactive system involves chemical reactions that create or consume substances

What is a blending process

A blending process mixes multiple input streams to produce a desired output composition

Is a blending process reactive or non reactive

A blending process is non reactive

What is composition in a blending process

Composition is how much of each component is in the mixture

What is the controlled variable in a blending process

The output composition is the controlled variable

What is the manipulated variable in a blending process

The flow rate of one input stream is the manipulated variable

What is feedback control

Feedback control measures the output and corrects the process after an error occurs

Give a real life example of feedback control

Adjusting the shower temperature after feeling it is too cold

What is feedforward control

Feedforward control measures a disturbance and corrects the process before an error occurs

Give a real life example of feedforward control

Turning up hot water before someone flushes the toilet

What is the main advantage of feedback control

Feedback control corrects for any disturbance even if it was not predicted

What is the main disadvantage of feedback control

Feedback control only reacts after an error has occurred

What is the main advantage of feedforward control

Feedforward control prevents errors before they affect the output

What is the main disadvantage of feedforward control

Feedforward control requires disturbance measurement and cannot fix unknown disturbances

Why combine feedforward and feedback

Combining them gives prediction plus correction

What is a linear process

A linear process responds proportionally to small changes in input

What does linear mean in simple terms

Small input change causes small predictable output change

What is a nonlinear process

A nonlinear process does not respond proportionally to input changes

What is linearisation

Linearisation approximates a nonlinear system as linear near a normal operating point

Why do engineers use linearisation

Linear systems are easier to analyse and control

What is the overall goal of process control

To keep important variables at desired values despite disturbances

What are the advantages of batch processes?

Batch processes are flexible, cheaper to set up, and easy to change products.

What are the disadvantages of batch processes?

Batch processes have low efficiency, higher variability, and lower safety.

What are the advantages of continuous processes?

Continuous processes are efficient, stable, safer, and good for large scale production.

What are the disadvantages of continuous processes?

Continuous processes are expensive, complex, and difficult to modify.

What are the advantages of non reactive processes?

Non reactive processes are simpler, safer, and easier to model.

What are the disadvantages of non reactive processes?

Non reactive processes are limited to mixing, heating, or cooling only.

What are the advantages of reactive processes?

Reactive processes allow product formation and high value chemicals.

What are the disadvantages of reactive processes?

Reactive processes are complex, harder to control, and pose safety risks.