When learning about different control strategies it often helps to see the strategy in action.
I therefore made a Processing sketch for my students to play around with that illustrates proportional control applied to a motor.
You can see the sketch in action here:
Click me! I’ll take you where you want to go!
The white triangle simulates the angle of a motor (Process Variable – this would be the feedback of a real life system provided by a potentiometer for example)
The red line is used to visualise the set point
Click the left mouse button to create a new set point at the angle you clicked at.
The system will then use proportional control to get the motor’s angle to match the set point’s angle.
You can also press the top left button to turn the simulated friction on and off.
Note how proportional control cannot overcome that friction by itself and remember how integral control is used to solve the problem by generating an output that increases in magnitude based on the length of time that the error exists!