Development of an ultrasonic linear encoder

• Published in: Sensor review Vol. 43; no. 3; pp. 221 - 230
• Main Authors: Chang, Chung-Ping, Hong, Song-Fu, Chen, Tzu-Guang
• Format: Journal Article
• Language: English
• Published: Bradford Emerald Publishing Limited 09.05.2023; Emerald Group Publishing Limited
• Subjects: Automatic control; Automatic gain control; Coders; Displacement measurement; Distance measurement; Error analysis; Interpolation; Investigations; Lasers; Modules; Motion control; Sensors; Signal processing; Time of flight method; Transducers; Transmitters; Ultrasonic transducers; Velocity; Linear encoder; Frequency multiplication; Positioning stage; Heterodyne signal processing; Ultrasonic transducer
• ISSN: 0260-2288; 1758-6828; 0260-2288
• DOI: 10.1108/SR-07-2022-0262

Purpose In this investigation, a linear encoder system based on the ultrasonic transducer has been proposed. Ultrasonic transducers are usually designed for distance measurements, such as the time of flight method and sonar system. These applications are defined as discrete-length measurement technologies. The purpose of this study is to develop a continuous displacement measurement system using ultrasonic transducers. Design/methodology/approach A modified signal processing based on heterodyne signaling is implemented in this system. In the proposed signal processing, there is an automatic gain control module, a phase-shifting module, a phase detection module, an interpolation module and especially a frequency multiplication module, which can enhance the resolution and reduce the interpolation error simultaneously. Findings The proposed system can generate the encoding signals and is compatible with most motion control systems. For the experimental result, the maximum measurement error and standard deviation are about −0.027 and 0.048 mm, respectively. It shows that the proposed encoder system has the potential for displacement measurement tasks. Originality/value This study reveals an ultrasonic linear encoder that is capable of generating an incremental encoding signal, accompanied by a corresponding signal processing methodology. In contrast to the conventional heterodyne signal processing approach, the proposed multiplication method effectively reduces the interpolation error that arises because of multiple reflections.