The principle of ultrasonic ranging is that the ultrasonic transmitting device emits ultrasonic waves. It is based on the time difference when the receiver receives the ultrasonic waves, which is similar to the principle of radar ranging. The ultrasonic transmitter emits ultrasonic waves in a certain direction and starts timing at the same time as the launch time. The ultrasonic waves propagate in the air and return immediately when they encounter obstacles on the way. The ultrasonic receiver stops timing immediately when it receives the reflected waves.
(The propagation speed of ultrasonic waves in the air is 340m/s. According to the time t (seconds) recorded by the timer, the distance (s) between the emission point and the obstacle can be calculated, that is: s= 340t/2)
Ultrasonic waves have strong directivity and can propagate far in the medium. Therefore, ultrasonic waves are often used for distance measurement. For example, distance meters and level measuring instruments can all be realized by ultrasonic waves. . The use of ultrasonic detection is often fast, convenient, simple to calculate, easy to achieve real-time control, and can meet industrial practical requirements in terms of measurement accuracy. Therefore, it has also been widely used in the development of mobile robots.
In order for a mobile robot to automatically avoid obstacles and walk, it must be equipped with a ranging system so that it can obtain distance information (distance and direction) from obstacles in a timely manner. The three-directional (front, left, and right) ultrasonic ranging system introduced in this article is to provide a movement distance information for the robot to understand the environment in front, left, and right.
In order to study and utilize ultrasonic waves, many ultrasonic generators have been designed and manufactured. Generally speaking, ultrasonic generators can be divided into two categories: one is to generate ultrasonic waves electrically, and the other is to generate ultrasonic waves mechanically. Electrical methods include piezoelectric type, magnetostrictive type and electric type, etc.; mechanical methods include Galtonic flute, liquid whistle and airflow whistle, etc. The ultrasonic waves they generate have different frequencies, powers and acoustic wave characteristics, and therefore have different uses. The more commonly used one is the piezoelectric ultrasonic generator.