Usually blind people use white canes to provide navigation assistance to the user. But it is very limited in its ability and cannot easily detect obstacles. Therefore the main objective of this paper is to design a navigation system for the blind person which can be used both in the indoor and outdoor environment. For this ultrasonic devices are used to determine the range of the obstacles and micro controller to act accordingly. Since the blind people are more efficient in hearing than the normal people, the system is focused on alerting the user through vibration and voice feedback about the surrounding obstacles.
The System Architecture:
The navigation system makes use of GPS, voice and ultrasonic sensors for obstacle detection. The proposed navigation system mainly focuses on two components: sensing of the immediate surrounding environment against the obstacles and provide warning about the obstacles by means of vibration and voice feedback. The fig 1 explains the system architecture block diagram. The detection of the obstacle can be done by using ultrasonic sensors, the implementation of the vibrational alert and voice feedback system using vibrator motor and ISD 2560 ChipCorder respectively. The ultrasonic sensor TS601 is used in the system, which detect the barriers in the path. The control system is developed using PIC16F877A micro controller.
Fig 1: System Architecture
PIC16F877A micro controller is used to measure the distance between the person and the obstacle using the sensor and also controls the motor circuit to act as a warning system. Simultaneously micro controller interfaces with ISD 2560 to produce speech output so that the person can know the direction of the obstacle. Three sensors are used in this system to detect the direction of the obstacle. To work in different conditions an algorithm has been developed for the navigation system.
Design Flow of the System:
Fig 2: Design Flow
When the system is turned ON, by sending ultra sound in three directions, it continuously checks for the obstacles. If there is no obstacle the system continues its search, but if there is some obstacle, a speech output is produced by the vibrator motor of the respective side. Fig 2 shows the navigation system work flow.
Fig 3: Navigation System Processing
|Distance Between The Obstacle and the White Cane
||Response in the Vibrator Motor
|Distance is less than 30 cm
||Motor vibrates in high speed
|Distance is in between 30 cm to 50 cm
||Motor vibrates in moderate speed
|Distance is in between 50 cm to 70 cm
||Motor vibrates in minimal speed
Table 1: Alarm System Process
|Direction of the Obstacle Respective to the White Cane
||Announcement in the Speaker/Headphone
||Obstacle to the left
||Obstacle to the right
|Front and Right
||Obstacle upfront and to the right
|Left and Right
||Obstacle to the left and right
|Front and Left
||Obstacle upfront and to the left
Table 2: Voice Feedback Process
Fig 3 explains the exact operation of the navigation system. The response of the sensor activates the vibrator and the voice alarm accordingly. For example, if the ultrasonic sensor position at the front detects the strong reflection of wave coming only from the front, meaning that there is an obstacle in the front. The vibrators are wrapped around the wrist of the user. Since the obstacle is detected by the front sensor, the vibrator for the front obstacle vibrates continuously and recorded voice keep playing “obstacle on the front”. This announcement continues until the user moves away from the obstacle.
Similarly, if the sensor receives strong ultrasonic waves from the left or right, the system will provide vibration and voice feedback accordingly as shown in table 2. Again, if the sensor do not detect any obstacles, then the vibrator and the voice feedback will be inactive which means the user can walk in any direction. Hence, this navigation system will be effective, low cost and user friendly solution for navigation problems of the visually impaired person.