Department of Mechanical engineering
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Item Extraction of Modal Parameters of Micromachined Resonators in Higher Modes(Springer, 2014-01) Rao, Venkatesh K.P.In this paper, a micro machined resonator is fabricated using SOI MUMPs process. A total of 50 out-of-plane mode shapes and their corresponding modal parameters (resonant frequency and damping) are extracted. With the applied voltage, due to joule heating, natural frequency (f n ) and Quality (Q) factor change. This can be effectively used for tuning the resonator. A detailed modal analysis is carried out using an FEM simulator to compute the modal parameters across all the modes and results are within 5% of the data measured using a Laser Vibrometer. Q is estimated using the half-power point approach for the first 42 modes. It is also observed that Q goes up by a factor > 2 for modes beyond 27, as only a portion of the structure contributes to modal displacement. At higher voltages, thermal softening is observed due to local heating which results in structure behaving like a coupled resonator. Under these conditions, peak splitting is observed. This structure can be used in different sensor and actuator applications depending on the mode of operation.Item Coupled Field Analysis of Hemispherical Resonator Gyroscope(International Journal of Vehicle Structures & Systems, 2022) Rao, Venkatesh K.P.This work deals with the electromechanical analysis of the Hemispherical Resonator Gyroscope (HRG). The HRG is a type of Coriolis vibratory gyroscope (CVG), which uses Coriolis force to measure the input angular rate. For any CVG drive and sense mode, frequencies play a critical role, which decides the sensitivity and bandwidth of a sensor. In this study, we carry out modal analysis to evaluate the natural frequencies and corresponding mode shapes of an HRG. As HRG is an electromechanical structure, the device is driven at resonance in the drive direction, and the Coriolis force leads to motion in the sense direction. In this study, we present the piezoelectric based HRG; coupled field simulations are carried out to evaluate the performance characteristics of a sensorItem Design and Analysis of Single Drive Tri-Axis MEMS Gyroscope(Springer, 2022-11) Rao, Venkatesh K.P.MEMS based single and dual-axis gyroscopes have been widely explored for potential application in automotive, space, defense, and consumer electronics sectors. Tri-axis gyroscopes based on MEMS, however, have been sparsely studied. This work presents a novel design for tri-axis MEMS gyroscope and an analytical model to obtain the natural frequencies in drive and sense modes. These frequency values have been compared with the numerically obtained frequencies using Finite Element Analysis (FEA). The analytical results lie within 10% of their numerically obtained values. The frequency matching process involves many iterations of geometric dimensions if the end application requires minor design changes. The proposed analytical model will make the design customization easy as the frequencies of each mode will be expressed as a function of critical geometrical parameters saving multiple numerical runs required for design optimization.Item Modulating the Mechanical Resonance of Huh-7 Cells Based on Elasticity of Adhesion Proteins(IEEE, 2023-07) Rao, Venkatesh K.P.The atomic force microscope (AFM) has been used in cell biology for a decade. AFM is a unique tool for investigating the viscoelastic characteristics of live cells in culture and mapping the spatial distribution of mechanical properties, giving an indirect signal of the underlying cytoskeleton and cell organelles. Although several experimental and numerical studies were conducted to analyze the mechanical properties of the cells. We established the non-invasive Position Sensing Device (PSD) technique to evaluate the resonance behavior of the Huh-7 cells. This technique results in the natural frequency of the cells. Obtained experimental frequencies were compared with the numerical AFM modeling. Most of the numerical analysis were based on the assumed shape and geometry. In this study, we propose a new method for numerical AFM characterization of Huh-7 cells to estimate its mechanical behavior. We capture the actual image and geometry of the trypsinized Huh-7 cells. These real images are then used for numerical modeling. The natural frequency of the cells was evaluated and found to be in the range of 24 kHz. Furthermore, the impact of focal adhesion (FA’s) stiffness on the fundamental frequency of the Huh-7 cells was investigated. There has been a 6.5 times increase in the natural frequency of the Huh-7 cells on increasing the FA’s stiffness from 5 pN/nm to 500 pN/nm. This indicates that the mechanical behavior of FA’s leads to change the resonance behavior of the Huh-7 cell. Hence FA’s are the key element in controlling the dynamics of the cell. These measurements can enhance our understanding of normal and pathological cell mechanics and potentially improve disease etiology, diagnosis, and therapy choices. The proposed technique and numerical approach are further useful in selecting the target therapies parameters (frequency) and evaluating of mechanical properties of the cells.