| PhD Viva

Name of the Speaker: Mr. Harikumar Ganesan (EE16D204)
Guide: Dr. Sankaran Aniruddhan
Co-Guide: Dr. Boby George, Dr. Saleem Haneefa
Online meeting link: https://meet.google.com/vft-apfg-swo
Date/Time: 28th November 2023 (Tuesday), 11:00 AM
Title: Advanced Interfacing Techniques for Differential Inductive Position Sensors

Abstract

Differential inductive position sensors are extremely popular in industrial, automotive, rail, military, under-water and space sectors and are often used as secondary transducers in measurement of pressure, fluid level, tensile force etc. The rugged, non-contact nature, and the simplicity of design of these sensors contribute to their enhanced reliability, which is paramount in such applications. The conventional signal conditioning electronics for these sensors, however, are at a relatively higher level of complexity compared to the sensing element. At the minimum, they consist of two parts, the excitation circuit, which must have good amplitude and frequency stability, and the demodulation circuit, ranging from asynchronous type to phase sensitive type with additional phase correction circuits for better performance. For simplifying the interfacing scheme, thereby improving compactness and robustness, a new Relaxation Oscillator (RO) that performs both excitation and demodulation in a single circuit, for the most popular differential inductive position sensor, Linear Variable Differential Transformer (LVDT), is presented in this work.

Direct Interface Circuit (DIC) signal conditioning approaches for sensors have become popular in recent times in the interest of miniaturization and cost reduction. In these techniques, a microcontroller directly excites the sensor to obtain a time-modulated signal which is measured using a digital timer. However, the performance is typically poorer due to timing source drifts, noise, quantization and other limitations. In the interest of retaining simplicity, along with performance, a hybrid method employing a dual-slope technique using a microcontroller along with minimal analog circuits, to yield a high-performance interfacing scheme for the LVDT is also presented in this work.

The incorporation of microprocessors into the sensing package brings other advantages in addition to digital output, such as flexible error compensation, remote monitoring, networking and co-operation with other sensors. Such smart sensors are emerging as building blocks for the current ‘Industry 4.0’ revolution in achieving large scale autonomy and improved efficiency. In order to reduce down times and associated economic impacts, ‘sensor integrity information’ is crucial - i.e., the upstream controller must not only have access to the sensor’s estimate of the measurand, it must know whether it is reliable so that mitigation measures like isolating the degraded sensor or using a redundant alternate sensor can be undertaken. A method to generate an additional sensor integrity output, based on detection of in-band and out-of-band Radio Frequency (RF) interference, using a microcontroller-based interfacing scheme for a planar LVDT is also presented in this work, along with a sensor frequency switching-based mitigation scheme.

The schemes proposed have been validated through mathematical analyses, extensive simulation studies and practical experiments. The details will be presented in the seminar.