Acoustics, Dynamics, and Controls Commons^™

Generation Of Inhomogeneous Acoustic Waves Using An Array Of Loudspeakers, Samuel E. Wonfor, Trevor A. Kyle, J. Stuart Bolton, Jeffrey F. Rhoads

The Summer Undergraduate Research Fellowship (SURF) Symposium

In previous studies it has been shown that pressure fields created by inhomogeneous sound waves (waves which decay in a direction perpendicular to their propagation direction) are able to transmit energy into objects more effectively than ones created by conventional sound waves. This behavior may be useful in the detection of hidden explosive threats. To explore this, a device capable of constructing inhomogeneous waves is being developed. The proposed device is an acoustic array consisting of several high-frequency speakers. The speakers are independently driven to construct a desired inhomogeneous pressure field on a target surface. Inhomogeneous pressure fields were reconstructed …

Examination Of Ordering Effects In Sound Evaluations, Yiyun Zhang, Patricia Davies, Daniel Carr

The Summer Undergraduate Research Fellowship (SURF) Symposium

It is difficult to predict sound annoyance responses because annoyance is an inherently subjective concept and the evaluation standard could be different from each person. Usually, annoyance models are functions of strengths of sound characteristics only, and these models can help engineers to improve sounds that machines make and minimize annoyance levels, but other factors can also influence annoyance ratings of products. The main goal of this research was to investigate ordering effects in sound evaluations when people are hearing a set of sounds in sequence. Of particular interest is how the response to a sound influences the response to …

Dynamic Characterization Of Periodic Lattice Of Elastically-Connected Bi-Stable Elements Under Seismic Excitation, Lingwei Meng, Myungwon Hwang, Andres F. Arrieta Ph.D.

The Summer Undergraduate Research Fellowship (SURF) Symposium

Metamaterials are engineered materials, typically in periodic arrangements, which exhibit unconventional or extreme properties not found in nature. Understanding the dynamics of metamaterials enables the design of structures with specific functionalities. The dynamics of metamaterials in linear regime has been relatively well studied in recent years, however the unique phenomena arising from nonlinearities in metamaterials are yet to be explored. In this paper, we focus on an array of bi-stable elements connected by elastic springs under various forms of external excitations acting on the entire system. The general equations of motion are derived to handle any degree-of-freedom (DoF) systems of …

Stability Analysis Of A Flexible Vehicle Model Controlled By Human Pilot Models, Abhishek Ajmani, Anil Bajaj

The Summer Undergraduate Research Fellowship (SURF) Symposium

There is a constant race among automobile manufactures to design safer vehicles while minimizing weight to reduce power consumption. Additionally, organizations like NASA and SpaceX are persistently working toward creating reliable, lightweight rovers to be used on the surface of Mars. However, the lightweight requirement often increases vehicle flexibility, which further develops a tendency toward instability in the lateral (sideways) direction. This investigation develops a mathematical model that represents the dynamics of a flexible vehicle in forward motion, and a heuristic human pilot model is proposed which controls the vehicle. Following such formulation, the combined vehicle and pilot model is …

Cyber-Physical System Characterization And Co-Regulation Of A Quadrotor Uas, Seth E. Doebbeling

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

An Unmanned Aircraft System (UAS) is a Cyber-Physical System (CPS) in which a host of real-time computational tasks contending for shared resources must be cooperatively managed to obtain mission objectives. Traditionally, control of the UAS is designed assuming a fixed, high sampling rate in order to maintain reliable performance and margins of stability. But emerging methods challenge this design by dynamically allocating resources to computational tasks, thereby affecting control and mission performance. To apply these emerging strategies, a characterization and understanding of the effects of timing on control and trajectory following performance is required. Going beyond traditional control evaluation techniques, …

Novel Transducer Calibration And Simulation Verification Of Polydimethylsiloxane (Pdms) Channels On Acoustic Microfluidic Devices, Scott T. Padilla

USF Tampa Graduate Theses and Dissertations

The work and results presented in this dissertation concern two complimentary studies that are rooted in surface acoustic waves and transducer study.

Surface acoustic wave devices are utilized in a variety of fields that span biomedical applications to radio wave transmitters and receivers. Of interest in this dissertation is the study of surface acoustic wave interaction with polydimethylsiloxane. This material, commonly known as PDMS, is widely used in the microfluidic field applications in order to create channels for fluid flow on the surface of a piezoelectric substrate. The size, and type of PDMS that is created and ultimately etched on …

Development Of The Compact Jet Engine Simulator From Concept To Useful Test Rig, Henry H. Haskin

Mechanical & Aerospace Engineering Theses & Dissertations

NASA had a goal to develop a set of modeling tools for designing next generation civil transport aircraft with reduced noise, emissions and increased fuel efficiency by 2016. To verify the models, a database of aerodynamic and acoustic data was needed for an unconventional flying wing design that was predicted to meet the goals. A Compact Jet Engine Simulator (CJES) was needed as the jet source for the 5.8% scale model. Ultra-Compact Combustor Technology from the Air Force Research Laboratory was used to reduce the conventional burner acoustic test rigs down to the required scale size. The Air Force design …

Guided Target Control System Final Design Report, John Barry, Zachary Eagan, Ryan Mackintosh

Mechanical Engineering

Daimler Automotive, the parent company of Mercedes-benz requires improved methods for testing their Autonomous Emergency Braking Systems. To this end they have presented a series of four senior projects to California Polytechnic State University in San Luis Obispo. One of the Projects is to build a facsimile of a human crossing the street. The other three projects of which this is a part; are to produce an autonomous car facsimile. These projects are intended for use in testing new Autonomous Emergency Braking Systems and may serve as the basis for future senior projects.

Small-Scale Intelligent Vehicle Design Platform, Christopher Grant, Jay Miley, Evan Phillips

Mechanical Engineering

Intelligent Vehicle Design is a growing field with the potential to save many lives by actively minimizing the impacts of human error. Though there are many ways to research intelligent vehicle control, full-scale implementations are expensive and dangerous and computer simulations have extremely steep learning curves. Researchers and students need an accessible, adaptable, and robust development platform to rapidly create and test autonomous control algorithms. While small-scale platforms are often designed from the ground up for specific projects, this requires analysis, design, and manufacture. The goal of this project is to develop a small-scale intelligent vehicle that can be configured …

Passive Bottom Reflection-Loss Estimation Using Ship Noise And A Vertical Line Array, Lanfranco Muzi, Martin Siderius, Christopher M. Verlinden

Electrical and Computer Engineering Faculty Publications and Presentations

An existing technique for passive bottom-loss estimation from natural marine surface noise (generated by waves and wind) is adapted to use noise generated by ships. The original approach—based on beamforming of the noise field recorded by a vertical line array of hydrophones—is retained; however, additional processing is needed in order for the field generated by a passing ship to show features that are similar to those of the natural surface-noise field. A necessary requisite is that the ship position, relative to the array, varies over as wide a range of steering angles as possible, ideally passing directly over the array …

Characterization Of A Small Electro-Mechanical Contact Using Non-Conventional Measurement Techniques, Kelsey M. Johnson

Mechanical Engineering ETDs

Currently there are limitations in computing chatter behavior of small electrical contacts embedded in components using finite element models. Reduced order models (ROM) have been developed of such electrical contact sub-assemblies to assess the chatter behavior of the contacts during vibration and shock environments. The current ROM method requires experimental validation. This ROM also neglects the damping effects of the viscous fluid that typically surrounds such sub-assemblies. Dynamic ring-down testing of the electrical contacts in air was performed and will provide a validation data set for the current ROM. Additionally, dynamic ring-down testing of the electrical contact was performed in …

Room Acoustics: Measurement And Correction With A Portable Digital Signal Processor, Azad Jalali

Thinking Matters Symposium Archive

The frequency response of a listening space is often of great interest to anyone pursuing an accurate and undistorted listening experience. Here we successfully implement sine- sweep deconvolution on a hardware platform to demonstrate an easy, digitized way to measure and guide improvements to the audio dynamics of a room.

P26. Global Exponential Stabilization On So(3), Soulaimane Berkane

Western Research Forum

Global Exponential Stabilization on SO(3)

Electroencephalographic Signal Processing And Classification Techniques For Noninvasive Motor Imagery Based Brain Computer Interface, Md Erfanul Alam

College of Graduate Studies: Theses & Dissertations

In motor imagery (MI) based brain-computer interface (BCI), success depends on reliable processing of the noisy, non-linear, and non-stationary brain activity signals for extraction of features and effective classification of MI activity as well as translation to the corresponding intended actions. In this study, signal processing and classification techniques are presented for electroencephalogram (EEG) signals for motor imagery based brain-computer interface. EEG signals have been acquired placing the electrodes following the international 10-20 system. The acquired signals have been pre-processed removing artifacts using empirical mode decomposition (EMD) and two extended versions of EMD, ensemble empirical mode decomposition (EEMD), and multivariate …

An Effective Methodology For Suppressing Structure-Borne Sound Radiation, Lingguang Chen

Wayne State University Dissertations

ABSTRACT

AN EFFECTIVE METHODOLOGY FOR SUPPRESSING

STRUCTURE-BORNE SOUND RADIATION

by

LINGGUANG CHEN

December 2017

Advisor: Dr. Sean F. Wu

Major: Mechanical Engineering

Degree: Doctor of Philosophy

This dissertation is primarily concerned with the development of an effective methodology for reducing structure-borne sound radiation from an arbitrarily shaped vibrating structure. There are three major aspects that separate the present methodology from all the previous ones. Firstly, it is a non-contact and non-invasive approach, which is applicable to a class of vibrating structures encountered in engineering applications. Secondly, the input data consists of a combined normal surface velocity distribution on a portion …

Analytical And Boundary Element Solutions Of Bulk Reacting Lined Ducts And Parallel-Baffle Silencers, Jundong Li

Theses and Dissertations--Mechanical and Aerospace Engineering

Lined silencers of various configurations are used to attenuate the noise from building HVAC equipment, gas turbines, and other machinery. First-mode analytical solutions are presented for sound attenuation along rectangular lined ducts, parallel-baffle silencers, and circular lined ducts. The sound absorptive lining is treated using a bulk property model. The analytical solutions entail solving a nonlinear characteristic equation in the transverse direction after the rigid-wall boundary condition is applied. The solution is compared to the boundary element solution and a local impedance analytical solution for several test cases.

Simulation Of Horse-Fence Contact And Interaction Affecting Rotational Falls In The Sport Of Eventing, Gregorio Robles Vega

Theses and Dissertations--Mechanical and Aerospace Engineering

Rotational falls, or somersault falls, have led to serious and fatal injuries during the cross-country phase of Eventing competitions. Research to improve the safety of the sport began in 2000 after five fatal injuries occurred in the 1999 Eventing season. These efforts led to safety devices such as air jackets, improved helmets, and frangible/deformable fences. The focus of this thesis is to develop a more complete understanding of the horse-fence interaction as the approach motion transitions to a rotational fall. To achieve this, a large distribution of inertial properties was compiled through the development of a cylinder-based inertia approximation and …

Advances In Multi-Agent Flocking: Continuous-Time And Discrete-Time Algorithms, Brandon Wellman

Theses and Dissertations--Mechanical and Aerospace Engineering

We present multi-agent control methods that address flocking in continuous-time and discrete-time settings. The method is decentralized, that is, each agents controller relies on local sensing to determine the relative positions and velocities of nearby agents. In the continuous-time setting, each agent has double-integrator dynamics. In the discrete-time setting, each agent has the discrete-time double-integrator dynamics obtained by sampling the continuous-time double integrator and applying a zero-order hold on the control input. We demonstrate using analysis, numerical simulations, and experimental demonstrations that agents using the flocking methods converge to flocking formations and follow the centralized leader (if applicable).

Impedance-To-Scattering Matrix Method For Large Silencer Analysis, Peng Wang

Theses and Dissertations--Mechanical and Aerospace Engineering

Large silencers used in the power generation industry usually have a very large cross section at the inlet and outlet. Higher-order modes will populate the inlet and outlet even at very low frequencies. Although the silencer itself is often modeled by a three-dimensional analysis tool such as the boundary element method (BEM) or finite element method (FEM), a direct computation of the transmission loss (TL) from the BEM or FEM model can be challenging without incorporating certain forms of modal expansion.

A so-called “impedance-to-scattering matrix method” is proposed to extract the modes at the inlet and outlet from the BEM …

A Transfer Matrix Approach To Determine The Low Frequency Insertion Loss Of Enclosures Including Applications, Shujian He

Theses and Dissertations--Mechanical and Aerospace Engineering

Partial enclosures are commonly used to reduce machinery noise. However, it is well known in industry that enclosures sometimes amplify the sound at low frequencies due to strong acoustic resonances compromising the performance. These noise issues are preventable if predicted prior to prototyping and production. Though boundary and finite element approaches can be used to accurately predict partial enclosure insertion loss, modifications to the model require time for remeshing and solving. In this work, partial enclosure performance at low frequencies is simulated using a plane wave transfer matrix approach. Models can be constructed and the effect of design modifications can …