Approximately 90% of visually impaired people live in developing countries according to WHO projections. Since they the low cost is a very essential criterion, it is a must to make the device as economical as possible. The initial research started off with analysing echolocation. Echolocation is the same as active sonar, using sounds made by the animal itself. Ranging is done by measuring the time delay between the animal's own sound emission and any echoes that return from the environment. The relative intensity of sound received at each ear as well as the time delay between arrival at the two ears provide information about the horizontal angle (azimuth) from which the reflected sound waves arrive. Echolocation had also been mastered by various humans too, who use clicks to find their way around, strengthening my hypothesis that soundscape based navigation was possible.
The selection of the correct sensor for the correct measurement of distance was extremely important because it needed to be cost effective, have a wide beam, and at the same time be able to detect versatile objects. In terms of accuracy, the infrared sensor was an obvious choice, but since it could only detect objects that weren’t black, it wasn’t used. I used an ultrasonic sensor (HC SR-04), which has a wider beam and can be used on all rigid bodies. Various positions were tested for the mounting of the sensor- 1.) When mounted on the chest it could just detect objects in front 2.) When mounted on the palm of the hand the direction the palm was pointing was proving too difficult to judge for the blindfolded test subject 3.) when mounted on the head, it gives the most swivel angle, hence was used. The original idea was to have two units mounted on the other sides of the head to test the curvature of any object in front, however when conducting experiments, the pulses from both the sensors were nterfering causing bogus values to be returned by the sensors. Hence the idea of having two sensors working seamlessly was abandoned.
1.) Swivel angle covered by the system- 195°
2.) Values returned by the sensor- When graphed.
Additional tests with obstacles- The blindfolded test subject was introduced to an environment with obstacles, a normal car parking area. He was able to detect obstacles as far as 3 metres (In an unknown environment). Initial disorientation was observed. Experimental testing exposed flaws with the system such as few inaccurate values returned by the sensor and problems with detecting soft objects and sometimes amounts of noncomprehendible noise. This was primarily produced by pointing the sensor towards objects that are rapidly shifting in position, or many objects kept at a faraway distance (caused by the beam angle). It also produced some unexpected results like being able to detect guide rods.