A Three-Dimensional Pen-Like Ultrasonic Positioning System Based on Quasi-Spherical PVDF Ultrasonic Transmitter

In this article, a three-dimensional (3D) pen-like positioning system based on the high-precision 3D ultrasonic (US) positioning method is presented. The high-precision 3D US positioning method can achieve millimeter-level accuracy in 3D positioning within a working area of 2 m × 1.5 m × 1.5 m. In order to improve the real-time performance of the proposed system, the 3D positioning of an electronic pen is realized by a high-precision time-of-flight (TOF) detection method based on the dynamic threshold and average zero-crossing detection. The average zero-crossing detection overcomes the limitations of the traditional zero-crossing detection that is sensitive to noise. The proposed positioning method can achieve high positioning accuracy without conducting complex calculations. The positioning accuracy of the proposed system is verified experimentally. In the experiment, a total of 60 test positions were uniformly set within the workspace, and static and dynamic positioning accuracy experiments were performed at all test positions. Experimental results showed that the static and dynamic positioning errors were less than 0.32 mm and 1.0 mm, respectively; thus, high positioning accuracy was achieved. In addition, the experimental results showed that the proposed systems could support 3D air writing. Accordingly, the proposed system can meet the crucial requirements of 3D human-computer interaction applications.