Aid system for visually impaired people at spatial orientation

The paper is devoted to the analysis of possibilities of infrared lasers and ultrasonic sensors of distance measurement in assisting visually impaired people.

reflected signal is usually inversely proportional to the distance from the object to the infrared transceiver. The maximum distance is the threshold for determining the presence of the object. An example of such a sensor is the sensor range Sharp GP2Y0A02YK0F (figure 1) is an analog infrared sensor to determine the presence of an object at a distance of from 20 to 150 cm [9]. The main disadvantage of this sensor is that the distance measurement is used triangulation method. For this reason, the measurement results depend on the angle of incidence of IR radiation on a controlled surface, which is unacceptable for the considered problem.
A significant drawback of optical, including laser, sensor is bad resistance to weather conditions. For example, contamination of the detector leads to the impossibility of detecting objects, while ultrasonic sensors with the same degree of contamination continue to work, but with less sensitivity.
The system to help people with impaired vision is currently developed. The main purpose of such systems is to provide information on the nature of the obstacles. As measurement sensors in such a system typically uses a pair of ultrasonic sensors. This seems the most reasonable, the more that existing ultrasonic sensors, such as used in Parking Systems (Parktronic), have small dimensions, allowing to place them inside a regular orthopedic cane. Ultrasonic sensors can have separate transmitters and receivers, and combined.
The first of these is the sensor HC-SR04 ( figure 2). This ultrasonic sensor can measure the distance to obstacles in the range from 2 cm to 4 m. It is the most preferable in terms of price/quality, but its dimensions, components 40×20×15 mm, not allow you to place it inside the cane. Parking sensors use a combined emitter and receiver. The most effective parking sensors at a distance from 25 cm to 1.8 meters are the sensors which correspond to a desired range of distances.
There are separate modules ultrasonic sensors (sonar), such as LV-MAXSONAR-EZ1 (figure 3), allowing to detect objects at distances up to 6.45 m. This sonar is one of the typical decisions on the basis of ultrasonic sensors MaxSonar-UT firms Maxbotix. Module output signals on the distance of the object present in three forms: analog signal, PWM and serial data R x and T x . There is also a sealed design given module ultrasonic sensor LV-MAXSONAR-WRC1 (figure 3 b).   Table 1, where added the most accessible sensor ParkMaster A [10]. The diameter of the sensors themselves is almost the same and ranges from 16.4 mm for the sensor used with the LV-MAXSONAR-EZ1 to 18.8 mm sensor ParkMaster A. the Problem is, the Board size of the module LV-MAXSONAR-EZ1 is 19.9×22.1 mm, which eliminates the placement of the Board of the stick. As a way out of this situation, you can offer accommodation module LV-MAXSONAR-EZ1 in rubber cane tip diameter reaches 50 mm, and use this module to detect obstacles like a step or a curb. Sensor to detect the steps down it is advisable to place the handle of the cane and used as a sensor ParkMaster or A sensor selected from the module LV-MAXSONAR-EZ1. Surface mount the sensor on the body of the cane implies the contact with the dust particles, water and maybe some reagents, which are applied to the road surface, resulting in a preferred use of the sensor is totally enclosed. Most of the sensors that are built in sealed design, protection of its internal structure correspond to the degree of IP67, which allows it to be completely closed against the ingress of dust and moisture. You should also use a sensor with a broad temperature range (-40÷70°C). Another option to consider is the beam width, which is usually contained in the technical documentation for the sensor or can be determined experimentally.
After assembly of the device, load the program memory of the microcontroller and layout of all elements in the cane, it was necessary to test the sample.
To do this, use normal laboratory conditions with obstacles of the type of steps down and steps up. The program was configured so that when approaching certain obstacles used the same algorithm like parking sensors on the cars that is, the closer the obstacle, the higher the pitch of the sound, and the farther away from obstacles so that it will be lower ( figure 4).
The fundamental difference from the rest of the competing devices is to scan all the objects not only in the horizontal plane, but also below it, i.e. the presence of ledges, stairs leading down, and wells and hole.

Conclusion
The device showed good results when scanning a space in motion, in laboratory conditions. At the exit to the street, it was immediately revealed that one of obvious drawback is the device output. In a typical street environment due to noise sound with conventional piezoelectric sensors is not audible when using headphones. The user can also experience some discomfort because of people with impaired vision, a person receives compensation for a lack of vision in enhanced auditory senses, and a person cannot prevent them from functioning.
It can be concluded that the most effective would be to use not only one type of output signal (signaling of danger) but several at the same time. Additional information channel for a person can be a source of vibration in the handle of the cane. In this case, when using the vibration signal in the form of periodic bursts of pulses can be frequency of the vibration signal coding type of obstacle (step up or step down), and the frequency of the pulse train to be used for coding distance to the obstacle, i.e. the closer the obstacle, the higher the frequency of the pulse train. In order to be able to use the cane as a regular cane for walking, it is necessary to highlight the moments when it takes a fixed position in space. It can be implemented that including the system processing of the measuring information twoaxis accelerometers. In the layout system aid visually impaired people was used 2 ultrasonic sensors HC-SR04, which provided the performance of the system if an obstacle is detected and the type of the step up, and step down.