The number of traffic accidents and injuries continues to increase year by year, and annual traffic fatalities in Japan remain. Under these conditions, there is an urgent need for technologies which can mitigate the serious damage caused by car accidents, as well as prevent the accidents themselves. Some members of this study have played active roles in a study up for the Advanced Safety Vehicle (ASV), a project conducted by the Japanese Ministry of Land, Infrastructure, Transport and Tourism, and are involved with ASV research and development. An ACC system maintains the vehicle at the speed set by the driver, and when it detects a preceding vehicle travelling at a slower speed than the driver’s vehicle, it controls the vehicle speed to match the speed of the preceding vehicle. It also performs following control to maintain the level of distance between vehicles which was set by the driver (a distance proportional to the vehicle speed). There has been past research for ACC systems aimed at designing a vehicle following distance control system using linear approximation and linear control logic. When a vehicle is driving at high speed. Such as on an expressway, sideslip occurs when the vehicle corners. It is known that this sideslip operates toward the outside of the turn when the vehicle is at slow speed, and toward the inside of the turn when the vehicle is at high speed. Research and development of 4WS systems that steer the rear wheels in order to reduce this sideslip and improve driving performance have been carried out.
ACC System Configuration
Constant velocity control: when there are no vehicles straight ahead, or when there is a large distance between the driver’s vehicle and the preceding vehicle, the system maintains a constant vehicle velocity.
(2) Deceleration control: when a vehicle traveling ahead at a slower speed is detected, the system uses the throttle to decelerate the driver’s vehicle. If this deceleration is insufficient, the system uses the brake to decelerate the vehicle.
(3) Following control: when the driver’s vehicle is following behind the preceding vehicle, the system controls the throttle and brake so that the time interval between the vehicles (which corresponds to a distance between the vehicles that is proportional to the velocity of the driver’s vehicle) is the time which was set by the driver.
(4) Acceleration control: when, due to a lane change, there is no longer a vehicle ahead of the driver’s vehicle, the system accelerates the vehicle up to the velocity set by the driver, and then maintains a constant velocity. When the driver’s vehicle approaches a vehicle ahead of it without slowing down enough, an alert buzzer and display prompt the driver to apply the brakes or take other appropriate action.
Conclusion
Improving the preceding vehicle lock-on performance by improving the Millimeter Wave Radar unit and making full use of object identification logic and path estimation logic resulted in improved driving stability. This performance was achieved even on an expressway with continuous sharp turns in a mountainous region, or an expressway with multiple lanes and heavy traffic in an urban area. The preceding vehicle identification performance was approximately the same as or better than the performance of other such systems in the industry. For the acceleration/deceleration performance, which has a large effect on occupant comfort, when the lane was changed during tracking and the preceding vehicle sped up, the acceleration performance satisfied the need for a smooth feeling of acceleration with a short response delay. Conversely, when the driver’s vehicle caught up with the preceding vehicle, a smooth and comfortable feeling of deceleration was achieved.
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