Electronic Travel Aids
Electronic travel aids are devices that give off a warning by auditory or/and tactile signals when an obstacle is in the way and allow the user to avoid it. Several devices have been developed to improve the mobility of blind people: talking GPS, devices for landmark identification, ultrasonic obstacle detection cane, Mini guide, Palm sonar .In indoor or outdoor crowded environments, ultrasonic devices are limited due to multiple reflections.
The major disadvantages of these solutions are:
- They only detect obstacle existence and distance without specifying indication about their nature which is important for the user to know.
- The existing Electronic travel aids are inaccurate in detecting some obstructions that are not protruding but present potential threat such as descending stairs, holes, etc.
- The system communicates its recommendations, through intensity or frequency variations.
Thus feedback information is often sent to the user through vibration or sound signals. Therefore training course is needed to keep the user informed about how to understand and react in real time to alerts that are transmitted regarding the existence of obstacles as well as their recognition. On the one hand, such training can be sometimes more expensive than the product itself. On the other hand, it is often difficult and complex for the users to assimilate it properly.
Furthermore, in the case, where information is transmitted as an acute sound, that may happens several times especially when the obstacle is very close, it may be embarrassing for the when they are in public. This paper is focused, on the development of the smart cane using two types of sensors which are ultrasonic sensors and monocular camera. Selection of these sensors takes into account their area of operation and their performances. Selection also depends on several other factors as: cost, type of scene, type of obstacle to be detected, detection range and desired precision of the measurements.
The main idea consists in merging data provided by the two sensor types to allow more accurate information, to be transmitted to the user via a Bluetooth module a voice message specifying the nature of object, characteristics and the distance between the detected obstacles and the device. In this paper, we explore ultrasonic sensor potentials in object detection and mainly stairs recognition. This type of sensors has significant potential in robotic applications. And widely used in collision avoidance systems and in localization and navigation of mobile robots. In addition to robotic application, ultrasonic sensors are used in many other applications in different fields such as echography in medical field, non-destructive testing of materials.
They are capable to perform under low visibility conditions making it ideal for night as well as day use. Hence, ultrasound sensor seems to be a good solution for our system to detect and recognize several objects. However, recognition of the object under different viewing conditions is still a challenge for autonomous systems. Many features can be extracted from the ultrasonic signal, providing different information and descriptions that are used to describe the detected object.
