Passive Roadside Reflectors and Communications Systems for Improvement of Radar Reliability

The use of radar in automotive applications such as adaptive cruise control is limited to detecting target vehicles directly in front of the host vehicle. Vehicles around a curve on a highway and cross traffic vehicles at an intersection cannot be detected by current radar systems. This is primarily due to the limited beam width angle of the radar. The first part of this report examines and evaluates the novel concept of using passive roadside reflectors (PRRs) to increase the utility of the radar system. PRRs on the shoulder and the median of a road are designed that would enable the radar system to pick up cross traffic at highway intersections. Both simulations and experiments demonstrate that this concept could be effectively used for cross traffic distance measurement. A limitation of this technology is that cross traffic cannot be detected when the radar equipped vehicle is very close to the intersection due to the lateral offset of the radar from the location of the PRR. However, the system is still valuable for providing future warning of cross traffic at rural intersections. A number of options are explored for the use of PRRs to improve radar measurements on highway curves. These include the use of tangential flat plate reflectors, skewed flat plate reflectors and convex reflectors. Algorithms for distance measurement with each of these options are derived and evaluated through simulations. The use of skewed flat plate reflectors is also evaluated experimentally and found to work effectively. The effective range of the radar on highway curves could be doubled by the use of the developed system. The second part of this report describes the development of wireless sensors that can be embedded into the road and can detect the passing of a vehicle as well as the velocity of the vehicle. By embedding such sensors into the road the location of different vehicles on a curve can be estimated by the vehicle receiving wireless information from the embedded sensors. In 2 order to ensure that the developed sensors are maintenance-free, unique technology that enables the sensors to operate by harvesting energy from vibrations of the road has been developed. The developed sensors harvest energy using piezoelectric patches and then utilize this energy for wireless transmission. This ensures that the embedded sensors do not need power supply lines nor do they need batteries that require replacement. Experimental results show that the developed sensor can be embedded in the road and can reliably detect the passing of a vehicle. The design of the sensors and experimental results are presented in the report. All the proposed tasks of the project have been completed. Details on the completed tasks are provided in the following pages.