PID controller
The PID controller is probably the most-used (alongside much cruder Bang-bang control) feedback control design. "PID" is an initialism for "Proportional-Integral-Derivative", referring to the three terms operating on the error signal to produce a control signal. If is the control signal sent to the system, formula_15 is the measured output and formula_16 is the desired output, and tracking error formula_17, a PID controller has the general form