Setting the PID parameters (controller gain, integral and derivative times) to achieve a desired process response is known as loop tuning. A well tuned loop takes the process value to the set point within the desired time frame, removes disturbances and can tolerate some variations or uncertainities in the process (i.e., it is robust).

Often measures of disturbances or uncertainities or even desired settling times are difficult to get and the control engineer has to have a feel for the process to tune the loop correctly. For this reason, loop tuning is considered both an art and a science.

While the art portion of tuning is developed with experience, there are many tools for the science part of the job. There are many commercial tuning packages available, but I recently came across this tool from Whitehouse Consulting that is free for evalulation purposes. The tool works out tuning parameters using different methods for various types of control algorithms.