Studies in Nonlinear and Stochastic Phenomena and Quality Factor Enhancement in a Nanomechanical Resonator

University of Minnesota M.S.M.E. thesis.July 2019. Major: Mechanical Engineering. Advisor: Subramanian Ramakrishnan. 1 computer file (PDF); xiii, 117 pages.Nonlinear damping has recently been experimentally observed in carbon nanotube and graphene-based nanoelectromechanical (NEMS) resonators and shown to be an effective means to achieve higher quality (Q) factors. Moreover, it has been shown that white noise excitation can be exploited to shrink the resonance width of the frequency response characteristics of the resonator as a pathway to higher Q factors. Motivated thus, this thesis is a study of certain fundamental characteristics of the nonlinear dynamics of a nanoelectromechanical resonator in both the deterministic and stochastic regimes with a focus on the influence of those characteristics on the Q factor. Using a Duffing oscillator based model, this thesis: (1) derives an analytical expression between oscillation amplitude and frequency of a NEMS resonator using the harmonic balance method to study the frequency response characteristics and validates the results using numerical simulation, (2) studies the deterministic dynamics of a NEMS resonator deriving an analytical relationship between the phase angle and maximum oscillation of the resonator response, (3) derives an analytical expression between the resonance frequency and resonance amplitude, (4) studies the hysteresis characteristics both in the stochastic and deterministic regimes elucidating the effects of nonlinear damping and external excitation on the hysteresis region, (5) finds that stochastic excitation with increasing intensity can shrink the hysteresis width, (6) shows that increasing the magnitude of the linear damping coefficient results in the decrease of Q-factors, (7) shows that in the combined presence of both parametric and external excitation, increasing the ratio of pump frequency to external forcing frequency results in lower resonant frequency and lower resonance width, (8) observes that in the parametrically driven nanomechanical resonator, higher parametric oscillation amplitude increases the resonance amplitude with a small impact on the resonance frequency, (9) solves the stochastic model using the Euler-Maruyama method and generates frequency response curves where it is found that higher noise intensity of Levy stable stochastic process can increase the Q factor, (10) finds that the Q factor is increased by decreasing the nonlinear damping and external harmonic driving amplitude. In summary, this thesis presents a set of novel results on the nonlinear, stochastic dynamics of a NEMS resonator and discusses the implications of the results for achieving enhanced Q factors. The results are of interest both from a theoretical viewpoint as well as in sensing applications using a nanoresonator

The van der Pol physical reservoir computer

The van der Pol oscillator has historical and practical significance to spiking neural networks. It was proposed as one of the first models for heart oscillations, and it has been used as the building block for spiking neural networks. Furthermore, the van der Pol oscillator is also readily implemented as an electronic circuit. For these reasons, we chose to implement the van der Pol oscillator as a physical reservoir computer (PRC) to highlight its computational ability, even when it is not in an array. The van der Pol PRC is explored using various logical tasks with numerical simulations, and a field-programmable analog array circuit for the van der Pol system is constructed to verify its use as a reservoir computer. As the van der Pol oscillator can be easily constructed with commercial-off-the-shelf circuit components, this PRC could be a viable option for computing on edge devices. We believe this is the first time that the van der Pol oscillator has been demonstrated as a PRC

A new automation approach for fuel station management system

Makine ve araç sayısı modern dünyada günden güne artmaktadır. Araçlar ve makinalar benzinle çalıştıkları için yakıta olan bağımlılık gün geçtikçe artmaktadır. Benzin istasyonlarındaki pompaların önündeki uzun kuyruklar günümüzde çok karşılaşılan değerli zamanın israfıdır. Bangladeş’te benzin istasyonları manuel olarak işletilmekte bu da gecikmelere sebep olmaktadır. Bu çalışmada benzin istasyonlarının hesaplarını koruyabilmek için otomatik yakıt yönetim sistemi geliştirilmiştir. Bu deney sonucu olarak bütün işlemlerden sonra fatura otomatik olarak yazdırabilmekte ve işlemler internet yolu ile uzaktan da kontrol edilebilmektedir. Bu sistem benzin istasyonlarındaki işlemleri hızlandıracağı gibi olası aksaklıklar da giderebilir.Day by day the number of vehicles and machines are increasing in the modern world. In the present day’s scenario, the demand of fuel is increasing because of vehicles and machines are depending on fuel. The long line in front of fuel stations, especially in front of gas pumps is a common scenario in the daily life that waste the valuable time. In Bangladesh, the fuel stations are operated manually that causes the delay. In this paper, we have developed an automated fuel management system that can maintain the account of the fuel stations. The results of this experiment print a receipt automatically after every transaction and can monitor the transactions from remote place via Internet. This management system also helps the fuel stations to become faster and can reduce corruptions in transactions of fuel stations

A four-state adaptive Hopf oscillator.

Adaptive oscillators (AOs) are nonlinear oscillators with plastic states that encode information. Here, an analog implementation of a four-state adaptive oscillator, including design, fabrication, and verification through hardware measurement, is presented. The result is an oscillator that can learn the frequency and amplitude of an external stimulus over a large range. Notably, the adaptive oscillator learns parameters of external stimuli through its ability to completely synchronize without using any pre- or post-processing methods. Previously, Hopf oscillators have been built as two-state (a regular Hopf oscillator) and three-state (a Hopf oscillator with adaptive frequency) systems via VLSI and FPGA designs. Building on these important implementations, a continuous-time, analog circuit implementation of a Hopf oscillator with adaptive frequency and amplitude is achieved. The hardware measurements and SPICE simulation show good agreement. To demonstrate some of its functionality, the circuit's response to several complex waveforms, including the response of a square wave, a sawtooth wave, strain gauge data of an impact of a nonlinear beam, and audio data of a noisy microphone recording, are reported. By learning both the frequency and amplitude, this circuit could be used to enhance applications of AOs for robotic gait, clock oscillators, analog frequency analyzers, and energy harvesting