The Cruise Control is a system that is capable of automatically maintaining the desired speed (i.e. speed set by the driver) of the vehicle without the need to press the accelerator pedal. This system is particularly useful while driving at a constant speed as it significantly reduces driver fatigue.
The system uses many components for its operation. They are:
After attaining the desired speed, the driver can activate this system with the help of steering mounted controls. Usually, buttons named ON, OFF, SET/ACCL are provided. However, they vary largely from manufacturer to manufacturer. ON and OFF buttons are for activation and deactivation respectively, while the SET/ACCL button helps to actually set the required speed.
But, the vehicle must attain that speed prior to setting. Thus, the system comes to know the speed of the vehicle from the speed of the driveshaft. Alternatively, it takes the input from the wheel speed sensors and sets throttle fixed at that location. In addition, the manufacturers mostly prefer vacuum operated actuator mechanism to hold the throttle in position.
Almost all cruise control systems get disabled as soon as the driver touches either the brake or the clutch pedal. It means that these systems are programmed in such a way that they turn 'OFF' upon the human intervention.
Block diagram of Cruise Control System