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The Cooperative Adaptive Cruise Control (CACC) is an extension to the Adaptive cruise control concept. CACC realises longitudinal automated vehicle control. In addition to the feedback loop used in the ACC, which uses Radar or LIDAR measurements to derive the range to the vehicle in front, the preceding vehicle's acceleration is used in a feed-forward loop. The preceding vehicle's acceleration is obtained from the Cooperative Awareness Messages it transmits using DSRC or WAVE technology (IEEE 802.11p). Generally, these messages are transmitted several times per second by future vehicles equipped with ITS capabilities. == Benefits of CACC over ACC == ACC systems, like human drivers, may not exhibit string stability. This means that oscillations which are introduced into a traffic flow - by braking and accelerating vehicles - may be amplified in the upstream direction. This leads to so-called phantom traffic jams (in the best case) or head-tail collisions (in the worst case). It has been shown that ACC systems designed to maintain a fixed following ''distance'' will not be string stable. ACC systems designed to maintain a fixed following ''time'' may or may not be string stable. CACC addresses this problem, and in either case may improve stability, by reducing the delay of the response to the preceding vehicle. In human drivers this delay depends on reaction time and actions such as moving the foot from throttle to brake pedal. In ACC this delay is reduced, but there still is a large phase delay because of the estimation algorithm needed to translate the discrete range measurements (supplied by radar or lidar) to a metric of change in range over time (i.e. acceleration and deceleration of the lead vehicle). CACC utilized vehicle to vehicle communications so that the vehicle has information not just on the vehicle immediately in front (through sensors), but also on a leading vehicle or vehicles further in front, through vehicle to vehicle communications of key parameters such as position, velocity, acceleration. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cooperative Adaptive Cruise Control」の詳細全文を読む スポンサード リンク
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