Editing Proportional–integral–derivative controller (section)

===Applicability===
The use of the PID algorithm does not guarantee [[optimal control]] of the system or its [[Nyquist stability criterion|control stability]] {{See below|{{section link||Limitations}}, below}}. Situations may occur where there are excessive delays: the measurement of the process value is delayed, or the control action does not apply quickly enough.  In these cases [[Lead–lag compensator|lead–lag compensation]] is required to be effective. The response of the controller can be described in terms of its responsiveness to an error, the degree to which the system [[overshoot (signal)|overshoots]] a setpoint, and the degree of any system [[oscillation]]. But the PID controller is broadly applicable since it relies only on the response of the measured process variable, not on knowledge or a model of the underlying process.