A Design Of The Ultrasonic Guidance System For The Blind Based On ARM

The number of the blind in China is the largest in the world. The blind live in the dark. They have many troubles in working, living and communicatinon. Above all, the most is how to walk safely. Bats develop unique ultrasonic auditory system by evolutionary processes. Bats can fly and prey in the dark. They can discriminate the existence, distance, orientation and velocity of the moving objects, as well as the size, figure and structure of the targets by receiving and processing echoes of emitted ultrasonic sounds. This subject, imitating the obilities of bats on ultrasonic, using the method of echolocation and time of flight, develops a prototype instrument based on the previous works. The prototype instrument acquires the power of reflected ultrasonic as well as the distance of obstacles.The first chapter discusses the world research situation and application on the ultrasonic guidance tecnique for the blind. The researching background and importance are introduced. At the same time, the researching situation and tactic plans at international are set out. In this chapter, four different types of ultrasonic guidance system for the blind are highlighting introduced. And their respective advantages and disadvantages are compared. Finally, the thesis advances the research's meaning and relates its mostly content.The second chapter introduces the ultrasonic generation, the process of ultrasonic reflection in the dissemination and ultrasonic attenuation. Through analysis the ultrasonic sensor internal construction and several important parameters of ultrasonic sensors, presents the working mechanization and characters of ultrasonic sensor. Finally, be based on the basic principle of ultrasonic distance measurement, given the distance of several common methods, sensor pointing angle, frequency, temperature, pulse width, firing blind and so on.In chapter 3 and chapter 4 design the hardware circuit in detail. The core hardware of the system is ARM Cortex-M3 core-based STM32. The guidance system for the blind have four sensor, they are point to the front, top, left, and right directions, ultrasonic is send by the sensor, echo signals are received by the sensor too. This system is made up of the microcomputer controll circuit, the transmit circuit of ultrasonic, the prepositive proportional amplifier circuit, TGC circuit, the filter circuit and so on, is detailedly described in this paper.In chapter 5 introduces the software part of the design, analysis the experimental results by experimental comparison. It's help to improve the system.The general picture is drawn in the last chapter and the research direction in this field for the future are also indicated in this part.This system is made up of ultrasonic sending, receiving and signal processing, the obstacle within the 34cm ~ 3m can be recognized. The system has the advantages of low power, low cost, easy to expand, abundant hardware and software are resources. So the system has certain practical value applied prospect.