Editing Proportional–integral–derivative controller (section)

===Optimal behavior===
The optimal behavior on a process change or setpoint change varies depending on the application.

Two basic requirements are ''regulation'' (disturbance rejection&nbsp;– staying at a given setpoint) and ''command tracking'' (implementing setpoint changes). These terms refer to how well the controlled variable tracks the desired value. Specific criteria for command tracking include [[rise time]] and [[settling time]]. Some processes must not allow an overshoot of the process variable beyond the setpoint if, for example, this would be unsafe. Other processes must minimize the energy expended in reaching a new setpoint.