https://www.rs-online.com/designspark/give-your-robot-the-mobility-control-of-a-real-mars-rover-part-1
PID - proportional integral derivative control
P stands for proportional gain
I for integral time
D for derivative gain
Example: car cruise control
P or proportional is described as in the farther you get from the desired speed (the setpoint), the more you press the gas pedal and the closer you get to the desired speed, the less you press on it. However, if you get to the desired speed, you would not press the gas pedal and the end results is your car slows down and stays a little below the desired speed.
I for integral. If you wait a little, if there is no improvement, you push a little more on the pedal. If you are stuck below the desired speed for a long time without progress, you push the gas pedal a little further. If you still do not make it to the desired speed for some time, you again push the pedal a little further down. Once you get to the desired speed you leave the pedal where it is. Integral control gives you accuracy but you have to wait.
For “D” or derivative, you react to sudden changes. Let’s say a strong wind gust pushes your car. Suddenly your speed surges fast upward toward the desired speed. You become startled so you release the gas pedal.
As the speed surge ends and the speed stabilizes, you will then return the pedal to where it was.
Derivative control manages sudden surges and may prevent overshooting your target speed.
A PID controller combines proportional control with additional integral and derivative adjustments, which help the unit automatically compensate for changes in the system
The PID controller's job is to measure process conditions, and calculate feedback and adjust output to force the process level to match a setpoint