Many modern mid to high range cars are equipped with cruise control. With the press of a button, a set speed can be automatically maintained. By utilising this feature, the driver can cruise at a more economic pace or at a required speed limit without the need to continuously check the speedometer.
The cruise control system is an example of a feedback mechanism. A sensor within the system measures the car's speed and in turn governs the carburettor. If the speed starts to decrease, for example when driving up a hill, the fuel flow will be boosted by the carburettor. Similarly, if the car increases in speed the carburettor will feed less fuel to the engine.
The sensor is usually an electromagnet which is located on the drive shaft. This produces an electric signal which is proportional to the speed. A motor can then work the carburettor based on signals received from the drive shaft via the cruise control.
The governing operation is usually carried out by a microprocessor. The microprocessor can consecutively read the sensor signal and then forward a control signal to the motor. One of the advantages of using a microprocessor, is that it has the ability to perform in more ways than simply controlling speed. As it gains information on the speed and fuel flow, it can additionally calculate and display the results of the speed, distance and fuel consumption.
