Abstract
Depth mapping can be carried out by ultrasound measuring devices using the time of flight method. Ultrasound measurements are favorable in such environments, where the light or radio frequency measurements can not be applied due to the noise level, calculation complexity, reaction time, size and price of the device, accuracy or electromagnetic compatibility. It is also usual to apply and fusion ultrasound sensors with other types of sensors to increase the precision and reliability. In the case of visually impaired people, an echolocation based aid for determining the distance and the direction of obstacles in the surroundings can improve the life quality by giving the possibility to move alone and individually in unlearnt or rapidly changing environments. In the following considerations, a model system is presented which can provide rather reliable position and distance to multiple objects. The mathematical model based on the time of flight method with a correction: it uses the measured analog sensor signals, which represent the probability of the presence of an obstacle. The device consists of multiple receivers, but only one source. The sensor fusion algorithm for this setup and the results of indoor experiments are presented. The mathematical model allows the usage, processing, and fusion of the signals of up to an infinite number of sensors. In addition, the positions of the sensors can be arbitrary, and the mathematical model does not restrict them to be placed in regular formations.
Highlights
The largest part of the information from our environment is collected usually by our sights.in the case of lack or damaged sight, the other senses become emphasized
The theoretical background of finding the obstacles is based on the time of flight method and uses sensor fusion
The algorithm determines the probability of the obstacle being present in each point of the scanned 3D space using a 4D matrix. This fourth dimension is composed of the three spatial coordinates and the sensor number as the fourth dimension, and, by the fusion, this fourth dimension is reduced
Summary
The largest part of the information from our environment is collected usually by our sights. In the case of lack or damaged sight, the other senses become emphasized. A part of the visually obtainable information can be gained by other means, but the visually handicapped people are still restricted in their movements in such places, which are not known to them. Thanks to the level of the technology, new methods were developed to give feedback to the user about the environment. Most of the solutions use cameras, to recognize defined objects or read text or to make a depth map [1,2,3,4,5]. The feedback is in most cases an audio feedback, like a warning sound or the system loudly reading the recognized text. The sound is one of the most important input channels if the sight is not functioning fully
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