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SUPPLEMENTAL NISSAN NEWS　　　 From: Corporate Communication Dept.
A30-SN-8089 　　　Date : November 25, 1998

Nissan Develops Adaptive Cruise Control System

Tokyo ‐ Nissan Motor Co., Ltd. today announced the development of a new adaptive cruise control (ACC) system that automatically maintains a set headway distance to a preceding vehicle. This system has been developed with an eye toward incorporating it in an Intelligent Transport System (ITS) and is scheduled to be commercialized next summer.

This ACC system uses the vehicle speed set by the driver as an upper limit for automatically controlling the host vehicle’s speed so as to maintain a certain desired distance from a vehicle ahead. The driver can set the speed at any arbitrary level between approximately 50 and 100 km/h, and the headway distance to a forward vehicle can be set at three different levels.

In terms of its specific operation, the system measures the distance to a preceding vehicle and the relative velocity of the vehicles, based on information obtained by a millimeter-wave radar installed at the front of the host vehicle. Using that data, it automatically controls the host vehicle’s speed by activating the throttle actuator or the brake actuators so as to maintain the set distance between the two vehicles. The millimeter-wave radar unit transmits a radio wave pulse and computes the distance to a forward object from the time it takes for the reflected wave to be received. The relative velocity is calculated from the difference in frequency between the transmitted and reflected waves.

In the event a preceding vehicle decelerates or another vehicle cuts in front of the host vehicle so that the headway distance is shorter than the value set by the driver, the ACC system automatically closes the throttle valve to decelerate the host vehicle until it returns to the preset distance. When the situation necessitates even greater deceleration, the system also automatically applies the brakes. Once the headway distance becomes longer than the set distance, as a result of the preceding vehicle or the host vehicle changing lanes, for example, the ACC system automatically opens the throttle valve and gradually accelerates the host vehicle until the set distance is reached. It then acts again to maintain the desired headway distance to preceding traffic.

The driver can override the operation of the ACC system by braking or accelerating the vehicle manually. In this case, the control system is released and precedence is given to the driver’s action.

Major Features of Adaptive Cruise Control System
(1) By automatically accelerating or decelerating the host vehicle to maintain a set headway distance to a preceding vehicle, the ACC system can help to coordinate driving behavior with the flow of traffic and also reduce driver fatigue and stress.
(2) It is a highly practical system with ample braking capability because it can control both the throttle and the brakes when decelerating the host vehicle. Moreover, the braking control function provides smooth deceleration comparable to that ordinarily obtained when the driver decelerates a vehicle.
(3) The range of conditions under which the system can be used has been expanded by adopting a millimeter-wave radar, which is capable of recognizing forward traffic regardless of rain or other inclement weather conditions.

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Contact: Foreign Media Section
Corporate Communications Dept.
Tel: 81-3-5565-2147