How to use PHA-21-G ultrasonic transducer to locate indoors

Indoor positioning is an application that has been proposed in recent years. How to use ultrasonic transducers for indoor positioning? Take a recent university experiment with the DYA-21-G ultrasonic transducer as an example, here is a brief introduction.

Figure 1 PHA-21-G horizontal non-directional air transducer as emission source   

   The site is in an indoor space, about 20×30 meters, and the roof height is about 3.5 meters. There is an automatic trolley on the ground, the length × width is 1 meter × 0.6 meters. Use the DYA-21-G horizontal non-directional air transducer as the emission source and place it flat on the cart. According to different experimental requirements, there can be more than one trolley in different areas. During the movement of the trolley, the PHA-21-G air transducer continuously emits ultrasonic waves of about 21Khz, which is a 180-degree emission state to the roof.

In order to achieve the effect of indoor positioning, when the car is running to a certain position, at least three receiving transducers must be able to receive the ultrasonic waves from the PHA-21-G ultrasonic distance transducer. Then the density problem should be considered when arranging the receiving transducer on the roof. The site is 30 meters wide and 20 meters long. The schematic diagram of the transducer arranged on the roof is as follows:

Figure 3 Schematic diagram of the distribution of receiving transducers for roof positioning 

 The distribution of the receiving transducers located on the roof can be changed according to the transmitting angle of the transmitting transducer. Generally speaking, the larger the transmitting angle, the less the number of receiving transducers required.

In order to improve the positioning accuracy, a transmitting antenna can be added to the trolley for simultaneous signal transmission. When the transmitting transducer is transmitting, use the antenna to broadcast the transmitting time, so that the receiving transducer on the roof can receive the transmitting time, which can improve the positioning accuracy.