LED를 이용한 자율주행용 위치센서에 관한 연구

Abstract

Currently, the navigation system of automobiles uses various positioning sensors as well as GPS (Global Positioning System) or Wi-Fi. In the case of smart phones, not only GPS and Wi-Fi, but also inertial navigation system (INS), Camera Vision, and recently, the technology of magnetic sensors is also used.In the automobile navigation system, the motion measurements of the body such as GPS, DGPS (Differential GPS), and Odometer are used. The use of such a variety of positioning sensors is due to the measurement error that positioning sensors can have and the high reliability of positioning results [2].In view of the advantages and disadvantages of the commonly used position sensors, GPS is vulnerable to other radio interference because the signals received from the ground are weak, and it is very difficult to receive signals in the environment where LOS (Line of Sight) is not guaranteed, such as indoors, underground, and building canyons.Wi-Fi has different positioning accuracy depending on the number of AP (Access Point) and installation interval. INS accumulates the bias and noise of the sensor over time, which tends to reduce positioning accuracy and reliability considerably [2]. It is difficult to apply to autonomous vehicles due to the error of location estimation. Especially, GPS, which is widely used in the estimation of the location of the vehicle, is used to measure the current location using satellites with navigation signal transmission function over 20,000 km above the surface of the ground and but it is not available to measure the location in tunnels and shadow areas. [3] In the case of LED (Light Emitting Diode), the fields of utilizing existing lighting as LED lighting are increasing due to miniaturization and long life, and thus, street lamps of roads are also being replaced with LED lighting. [3] In addition, LEDs convert electricity to light at the speed of about 30nm to 250nm [4], which enables them to transmit data through light signals. Currently, the research on indoor positioning technology using visible light wireless communication is actively conducted, and the localization of LED lighting located in the ceiling is underway. Positioning techniques using TDOA (time difference of arrival) are also being studied, and various location estimation studies such as hybrid localization technique using visible light network and zigbee network are in progress. However, these results are mostly conducted in indoor environments, and methods for solving both positioning accuracy and hardware implementation difficulty are still in lack [3]. In this paper, we propose a technique to estimate the position of the lane using the color temperature of 3000k, 4500k, and 6000k of LED by setting the color x and y coordinates of LED as absolute location in a different way from the existing VLC (Visible Light Communication) and to estimate the position by using the frequency sensitivity ratio by applying different frequencies. Since the position is measured using the chromaticity and frequency sensitivity ratio of LED, positioning is possible in the places where GPS signals are difficult to receive. In particular, this paper is focused on the environment of tunnels that are hard to receive GPS signals [6-9,20].