Cruise control
Videos
Cruise control is a system that automatically controls the speed of an automobile. The system is a servomechanism that takes over the car's throttle to maintain a steady speed set by the driver.
Cruise control on a Citroën Xsara
Cruise control on a 2000 Jeep Grand Cherokee steering wheel
Cruise control unit in the speedometer-cable and vacuum valve
A proportional–integral–derivative controller is a control loop mechanism employing feedback that is widely used in industrial control systems and a variety of other applications requiring continuously modulated control. A PID controller continuously calculates an error value as the difference between a desired setpoint (SP) and a measured process variable (PV) and applies a correction based on proportional, integral, and derivative terms, hence the name.
Early PID theory was developed by observing the actions of helmsmen in keeping a vessel on course in the face of varying influences such as wind and sea state.
Pneumatic PID (three-term) controller. The magnitudes of the three terms (P, I and D) are adjusted by the dials at the top.
Response of PV to step change of SP vs time, for three values of Kp (Ki and Kd held constant)