The PID controller equation is built around 3 constants, the proportional, integral, and derivative coefficient. Each of these constants can be adjusted to achieve a desired control response.
The graph above shows how the response of PID controller can change based on the set coefficients. In this example, the system is subjected to a setpoint change. The controller with K = 0.5 reacts rather slowly and reaches the setpoint with no overshoot. This condition is referred to as overdamped. The controller with K = 1.6 reacts extremely fast and severely overshoots the setpoint. The controller adjusts accordingly so that the output eventually settles down at the setpoint. This condition is referred to as underdamped. Finally, the controller with K = 1.1 reaches the setpoint quickly with minimal overshoot. Each PID controller application is different than the next and the coefficients need to be adjusted appropriately to achieve the desired response.
PID controllers are useful in the automotive industry for maintaining a constant speed or separation distance during cruise control. The controller will measure the actual distance compared to the desired distance and adjust the speed in order to minimize the delta.
PID controllers can help a robot achieve a desired movement or position. The PID controller will measure how far off the course the robot is, and adjust the steering to remain on the course.
A PID can be used to continually measure and adjust temperature. The PID controller will measure the current temperature vs. the desired temperature and adjust the heat source in order to minimize the difference.
