Shliusar Y. Embedded Self-Diagnostics of Sensor Devices Based on Ultrasonic Piezoelectric Transducers

The dissertation is devoted to the development and investigation of signal converters for ultrasonic sensor systems based on piezoelectric transducers with a built-in self-diagnostics function. The work proposes new approaches to modeling, analysis, optimization, and hardware–software implementation of signal paths aimed at improving the stability and reliability of sensor systems during operation. The first chapter reviews the current state of the art and analyzes the problems of ultrasonic sensor devices based on piezoelectric transducers. The principles of measurement signal formation based on the time-of-flight of ultrasonic waves are considered. The structure of signal paths and the factors leading to degradation of the electromechanical parameters of transducers are analyzed. The limitations of existing approaches to in-operation health monitoring of sensors are demonstrated. The second chapter is devoted to the development of mathematical and SPICE models of the analog front-end of ultrasonic sensor signal converters. Approaches to constructing SPICE macromodels of piezoelectric transducers and signal paths, taking into account destabilizing factors, are proposed. A method of built-in selfdiagnostics based on the analysis of informative features formed in the transmitting and receiving channels of signal conversion is developed. The third chapter presents the optimization of circuit design solutions for signal converters with a built-in self-diagnostics function. The operating modes of electronic circuits for transmitting and receiving piezoelectric transducers are investigated. Driver circuits for actuator channels operating in a self-oscillating mode are developed and optimized. Criteria for evaluating signal waveforms in receiving paths and requirements for their circuit components are formulated. The fourth chapter is devoted to the hardware–software implementation and experimental validation of the signal converter with a built-in self-diagnostics function. The implementation is carried out using a programmable system-on-chip (PSoC). Experimental validation of the signal converter is performed as part of an ultrasonic distance sensor, which confirms the operability of the proposed circuit and algorithmic solutions and allows evaluation of their efficiency under conditions close to real operation. The work combines theoretical research, circuit design and SPICE modeling, as well as experimental testing of the developed prototypes. The obtained results ensure improved stability, informativeness, and reliability of signal converters for ultrasonic sensors and can be used in the development of autonomous and safetycritical sensor systems. The conclusions summarize the main scientific and practical results, provide recommendations for the application of the proposed solutions, and outline directions for further research. The appendices contain materials on hardware–software implementation, results of experimental studies, as well as a list of scientific publications and conference presentations of the author related to the dissertation topic. Keywords: ultrasonic sensor devices, sensor systems, piezoelectric transducers, embedded self-diagnostics, signal converters, SPICE modeling, signal paths, Time-of-Flight, impedance characteristics, degradation processes, metrological characteristics, hardware–software systems.