Adaptive Wearable Navigation System for Visually Impaired and Blind People

Abstract

In recent years there has been a major interest in the localization and guiding of people in indoor and outdoor environments. Different methods to accomplish this are available. The application of each can depend on the environment and on the precision of localization that is required. An important field of research is precise pedestrian localization, navigation, and guidance for visually impaired and blind people, often depending on other people. Available systems and technologies do not yet allow to navigate freely and independent. In Germany at least 500.000 people are visually impaired and 150.000 are blind . Worldwide around 246 million people are visually impaired and 39 million are blind (Resnikoff et al., 2004). Visually impaired and blind people navigate on a daily basis. To avoid obstacles, they use different tools for orientation and navigation. These tools are selected based on each individuala s residual vision capabilities, and own preferences. Tools and navigation aids such as the white cane, guide dog, guide person, or monocular if the remaining vision is sufficient, etc. are used. These tools are helpful and indispensable, but users still encounter many problems and insecurities, due to certain limitations. For example, the white cane can be interpreted as an extension of the arm and is used to touch the environment at an extended distance. This kind of information is trustworthy for the user and there is for now no other system or method that could supply this type of information in such a simple and reliable form. Nevertheless, the information provided by this tool is not enough for an efficient and safe navigation. The white cane can be used to detect known reference points or to avoid obstacles; it can be used as a guiding tool. A major problem visually impaired and blind people encounter, is exploring unknown environments. When they explore an environment, they usually need to be accompanied by a visually capable person explaining the environment. In this process, one searches for landmarks or reference points. These landmarks are later used to orientate. It needs a long period of adaptation until the person is able to move alone in a previously unknown environment. This should be improved with a so far not available electronic-based navigation system, which should localize and guide the user safely through indoor and outdoor environments. Available methods for pedestrian positioning are for example GNSS, field strength measurements (WLAN, GSM and Bluetooth), pedestrian dead reckoning PDR, and so forth (Beauregard, 2006). GNSSs are the main methods being used for outdoor localization. For a precise indoor localization GPS cannot be used due to attenuation and scattering of the signals (Beauregard, 2006). Preferred methods for indoor localization are the use of pre-installed indoor communication infrastructures, laser, radar, sonar, camera, motion sensors, etc. Assuming that not all buildings have a pre-installed communication infrastructure, the field strength measurement methods also cannot be used. For an independent precise indoor localization, it is crucial to perform sensor fusion (Beauregard, 2006). One goal of this work is to specify for indoor environments a wearable system that incorporates different localization methods and scans the environment that the blind person is exploring to construct a map while simultaneously the persons position is tracked. The collected data will be useful for later guiding this person throughout the explored environment. A further goal is to find out the properties a navigation system must have to aid visually impaired and blind people in a safe and efficient manner. In other words, we want to answer the following question: How do we guide blind and visually impaired pedestrians through an unknown environment if we have a precise outdoor and indoor localization system? Which factors have to be taken into consideration to guide the user by such a system. The primary hypothesis of this dissertation is that such a navigation system has to be precise. But, more importantly, has to be able to adapt to the user's needs and preferences. To ensure that the user is guided and arrives safely at the destination, the individual techniques a person uses have to be taken into consideration.