Adaptive Cruise Control in Audi A8 Design and Operation

(Self Study Program, It can help you analyze some Automotive Electronic part and function)
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Determining speed of vehicle in front
=> Use is made of a physical phenomenon
known as the „Doppler effect“ to establish the
speed of the vehicle in front.
There is a basic difference depending on
whether the object reflecting the waves transmitted
is stationary with respect to the transmitter
or moving.
=> If the distance between transmitter and
object decreases, the frequency of the
reflected waves increases and vice versa.
This change in frequency is evaluated by the
electronics and supplies the speed value for
the vehicle in front.
Example demonstrating the Doppler effect:
As a fire engine approaches, the siren signal
sounds to be of a constantly high pitch (high
frequency).
As the vehicle moves further away, the tone
sounds lower (sudden frequency change –
lower frequency).
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