Mechanical Engineering Commons^™

Extremum-Seeking For Nonlinear Discrete-Time Systems With Application To Hcci Engines, H. Zargarzadeh, S. Jagannathan, J. A. Drallmeier

Electrical and Computer Engineering Faculty Research & Creative Works

For many control applications, identifying an optimal operating point by maximizing/minimizing a performance function is important. This paper applies the extremum-seeking method to nonaffine, nonlinear discrete-time systems stabilized by an optimal adaptive controller. First, a novel averaging method is used for the nonlinear discrete-time systems to show that their output unique extrema are stable equilibrium points. Then, a singular perturbation method in discrete time is employed to show that the overall closed loop system will dynamically converge to the extremum. The applicability of this scheme is numerically verified on a Homogeneous Charge Compression Ignition (HCCI) model validated experimentally and expressed …

Active-Passive Networked Multiagent Systems, Tansel Yucelen, John Daniel Peterson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper introduces an active-passive networked multiagent system framework, which consists of agents subject to exogenous inputs (active agents) and agents without any inputs (passive agents) and analyze its convergence using Lyapunov stability. Apart from the existing relevant literature, where either none of the agents are subject to exogenous inputs (i.e., average consensus problem) or all agents are subject to these inputs (i.e., dynamic average consensus problem), the key feature of our approach is that the states of all agents converge to the average of the exogenous inputs applied only to the active agents, where these inputs may or may …

Thermomechanical Modeling Of Cone Sample Of Zrb2-Sic Ceramic Under Arc-Jet Conditions, Lokeswarappa R. Dharani, Jun Wei

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The effects of oxidation on mechanical behavior of a cone sample of ZrB2-SiC ceramic under arc-jet test conditions is studied by a finite element (FE) model. First a steady-state heat transfer FE method was employed to conduct the thermal analysis and obtain the temperature distribution in the inner body of the cone. Then, resulting temperature distribution is applied to the thermomechanical finite element analysis to calculate the thermal stress distribution in the cone body. Due to the mismatch of material properties between the bulk ZrB2-SiC and its new products after oxidation, the outer oxide layers constrain the thermal deformation of …

Proper Orthogonal Decomposition Technique For Sub-Optimal Control Of Flexible Aircraft Wings Using Discrete Actuators, M. Kumar, S. N. Balakrishnan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Distributed parameter systems are, generally, described by a set of partial differential equations. Control design of these systems is a very complex task as compared to that of the lumped parameter systems that are defined by a set of ordinary differential equations. In this paper, we present a stabilizing state-feedback control design approach for a class of second order system, where the system can be controlled by discrete actuators in the spatial domain. The control methodology is developed by combining the technique of 'Proper Orthogonal Decomposition' and Approximate Dynamic Programming. The Proper Orthogonal Decomposition technique is utilized to obtain a …

Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models And Constrained Control Inputs, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a new state feedback model reference adaptive control approach for uncertain systems with gain scheduled reference models in a multi-input multi-output (MIMO) setting with constrained control inputs. A single Lyapunov matrix is computed for multiple linearization of the nonlinear closed loop gain scheduled reference system, using convex optimization tools. This approach guarantees stability of the closed loop gain scheduled reference model. Adaptive state feedback control architecture is then developed, and its stability is proven for the case with constrained control inputs. The resulting closed-loop system is shown to have bounded solutions with bounded tracking error, with the …

Decentralized Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Control theoretic concepts for decentralized adaptive control of uncertain systems with gain scheduled reference model is developed. For each subsystem a single Lyapunov matrix is computed, using convex optimization tools, for multiple linearization near equilibrium and non-equilibrium points of the nonlinear closed loop gain scheduled reference subsystem. This approach guarantees stability of the closed loop gain scheduled reference model. Then, decentralized adaptive state feedback control architecture is developed and its stability is proved. Specifically, the resulting closed-loop system is shown to have bounded solutions with bounded tracking error for all the subsystems. Simulation results for two different models of a …

Resilient Networked Multiagent Systems: A Distributed Adaptive Control Approachy, Gerardo De La Torre, Tansel Yucelen, John Daniel Peterson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Control algorithms of networked multiagent systems are generally computed distributivity without having a centralized entity monitoring the activity of agents; and therefore, adverse events such as attacks to the communication network and/or failure of agent-wise components can easily result in system instability and prohibit the accomplishment of system-level objectives. This paper studies resilient coordination of networked multiagent systems in the presence of misbehaving agents, i.e., agents that are subject to such adverse events. In particular, we consider a class of adverse conditions consisting of exogenous disturbances and interagent uncertainties and present a distributed adaptive control architecture to retrieve the nominal …

Decomposition Of Ionic Liquid Ferrofluids For Multi-Mode Spacecraft Propulsion, Steven P. Berg, Brynne Coleman, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Ionic liquid ferrofluids based on mixtures of [Emim][EtSO4] and [Bmim][NO3] fuels and hydroxylammonium nitrate oxidizer were synthesized by adding iron oxide nanoparticles. The resulting propellants were then tested for decomposition capability. Spot plate testing indicated that the temperature required to initiate rapid decomposition dropped from 115 °C to 75 °C with a 30% by weight addition of iron oxide for the [Bmim][NO3] propellant. Adding more iron oxide resulted in an increase in onset temperature. The [Emim][EtSO4] propellant had a much lower decrease in onset temperature, bottoming out at 90 °C. Batch reactor tests under vacuum showed that 10% addition of …

Reference Control Architecture In The Presence Of Measurement Noise And Actuator Dynamics, Gerardo De La Torre, Tansel Yucelen, Eric Johnson

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In this paper the command governor-based model reference control architecture is developed and analyzed for uncertain dynamical systems in the presence measurement noise and actuator dynamics. Specifically, the command governor is a dynamical system that adjusts the trajectory of a given command in order to enable an uncertain system to be able to follow an ideal reference system capturing a desired closed-loop dynamical system behavior both in transient-time and steady-state. In this paper, we present modifications to the original command governor approach in order to increase its robustness properties against measurement noise and actuator dynamics. In particular, the modified architecture …

Control-Oriented Modeling For Open-Cathode Fuel Cell Systems, Joseph Ishaku, Nima Lotfi, Hesam Zomorodi, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Due to numerous advantages of Polymer Electrolyte Fuel Cells (PEMFCs), they are becoming the mainstream fuel cell of choice for different applications. Open-cathode PEMFCs, in particular, are gaining increased popularity in low to medium power applications due to their simple structure and low parasitic losses. However, in order to achieve safe operation, increased durability and optimal performance, advanced control algorithms, which typically require control-oriented models, need to be implemented on open-cathode fuel cell systems. The open-cathode fuel cell system includes the fuel cell stack and all of the auxiliary components that are vital for its operation. In this paper, control-oriented …

Verifiable Frequency-Limited Adaptive Control Performance Based On Linear Matrix Inequalities, Mario Luca Fravolini, Tansel Yucelen, Daniel Wagner, Ali Albattat, Paolo Valigi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive controllers are often criticized for the lack of clear and easy verification procedures that relate design parameters to time domain performance especially during transients. For this reason, it is a challenge to rigorously certify existing adaptive control algorithms. To that end, we propose a validation framework where stability and performance requirements are formulated in terms of Linear Matrix Inequalities. This brings the advantage that adaptive controller design and verification can be analyzed and optimized via the solution of a convex optimization whose objective is to guarantee the evolution of the error components within an a-priori specified domain. This approach …

Radical Species Generation And Their Lifetime Extension By A Femtosecond And Nanosecond Dual-Laser System, Cheng Hsiang Lin, Zhi Liang, Jun Zhou, Hai-Lung Tsai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

For Many Material Processes, Desired Radical Species at Excited States Are Produced Which Interact with a Given Substrate for a Certain Period of Time Allowing Chemical Reactions between Them to Occur and Complete. Hence, It is Important to Maintain the Population of the Excited Radical Species for an Extended Period of Time, I.e., their Lifetime, Which is Defined as the Time for Emission Intensity to Decay to 1/e of the Initial Intensity. in This Study, a Femtosecond-Nanosecond (Fs-Ns) Dual-Laser System Was Employed to Generate Desired Radical Species Via the Fs Laser And, Then, to Extend the Lifetime of the Radical …

Association Between Vitamin D Receptor Gene Polymorphisms (Fok1 And Bsm1) And Osteoporosis: A Systematic Review, Zahra Mohammadi, Fateme Fayyazbakhsh, Mehdi Ebrahimi, Mahsa M. Amoli, Patricia Khashayar, Mahboubeh Dini, Reza Nezam Zadeh, Abbasali Keshtkar, Hamid Reza Barikani

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Osteoporosis is a Health Concern Characterized by Reduced Bone Mineral Density (BMD) and Increased Risk of Fragility Fractures. Many Studies Have Investigated the Association between Genetic Variants and Osteoporosis. Polymorphism and Allelic Variations in the Vitamin D Receptor Gene (VDR) Have Been Found to Be Associated with Bone Mineral Density. However, Many Studies Have Not Been Able to Find This Association. Literature Review Was Conducted in Several Databases, Including MEDLINE/Pubmed, Scopus, EMBASE, Ebsco, Science Citation Index Expanded, Ovid, Google Scholar, Iran Medex, Magiran and Scientific Information Database (SID) for Papers Published between 2000 and 2013 Describing the Association between Fok1 …

The Effect Of Different Rollover Conditions Of The Vibrator On Human Injury, Qin Li, Hang Liu, Zhiqiang Huang, Yaping Ding, Xiaoping Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Vibrator, as a crucial vehicle of oil and gas exploration, is challenged by the complex terrains. The probability of rollover accident is therefore high in bumpy terrain in which the drivers' life is seriously threatened. Finite element numerical analysis was used to study the injury of the driver's head, neck and chest in the rollover accidents of domestic KZ-28 type vibrator on different conditions. The injuries of three parts were evaluated based on the human injury criteria. Driver's safety on different rollover conditions was comparatively analyzed. The results indicated that the injury degree of human head caused by vibrator rollover …

Assessment Of Multi-Mode Spacecraft Micropropulsion Systems, Steven P. Berg, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Multi-mode spacecraft micro propulsion systems which include a high-thrust chemical mode and high-specific impulse electric mode are assessed with specific reference to cube sat-sized satellite applications. Both cold gas Freon-14 propellant and ionic liquid chemical monopropellant modes were investigated alongside pulsed plasma, electrospray, and helicon electric thruster modes. Systems involving chemical monopropellants have the highest payload mass fractions for a reference mission of a 500 m/s delta-V and 6U sized cube sat for electric propulsion usage below 55% of total delta-V. For higher electric propulsion usage, cold gas thrusters delivered a higher payload mass fraction due to lower system inert …

Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a new model reference adaptive control approach for uncertain systems with gain scheduled reference models in a multi-input multi-output (MIMO) setting. Specifically, adaptive state feedback for output tracking control problem of MIMO nonlinear systems is studied and gain scheduled reference model system is used for generating desired state trajectories. Using convex optimization tools, a single Lyapunov matrix is computed for multiple linearization's near equilibrium and non-equilibrium points of the nonlinear closed loop gain scheduled reference system. This approach guarantees stability of the closed loop gain scheduled system. Adaptive state feedback control scheme is then developed, and its …

Adaptive Architectures For Distributed Control Of Modular Systems, Tansel Yucelen, Jeff S. Shamma

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We consider the distributed control of large-scale modular systems, i.e., systems consist of physically interconnected (and possibly heterogeneous) submodules that use local information to achieve a given set of global objectives. A graph-theoretic approach is used to model the unknown physical interactions between submodules and utilize an adaptive control algorithm to learn and cancel the effect of such interactions as well as the submodule-level modeling uncertainties asymptotically by allowing submodules to locally communicate with each other through the graph. The key feature of our framework is to bound the mismatch error between the actual and desired closed-loop modular system performance …

Control-Oriented Modeling Of Laser Metal Deposition As A Repetitive Process, Patrick M. Sammons, Douglas A. Bristow, Robert G. Landers

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Laser Metal Deposition (LMD) is an additive manufacturing process whose dynamics are driven by complex heat transfer and fluid flow phenomena. The LMD process, along with every additive manufacturing process, is fundamentally a two-dimensional process possessing both temporal (or spatial) domain dynamics and propagation of information from layer to layer. However, modeling the two-dimensionality of the process for use in control has received little attention. Here, a model aimed at capturing the important nonlinear two-dimensional physical processes of the melt pool shape, while maintaining simplicity, is presented. The model is expressed in a form that lends itself to the design …

Thermal-Electromagnetic Analysis Of Infrared Antennas, Edward C. Kinzel, Brian Slovick, James Ginn, Brian Lail, Glenn Boreman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Antenna-coupled Metal-Oxide-Metal (MOM) diodes have been demonstrated for sensing and proposed for energy harvesting at THz, infrared, and even visible frequencies. The design of the antenna allows engineering of the response of the device with respect to polarization, wavelength and angle of incidence. The classic understanding of the antenna coupled MOM diode is that the electric field generated by the antenna causes electrons to tunnel through the barrier oxide. This is supported by the fact that when the oxide separates metals with different work functions, a properly polarized field can produce an asymmetric tunnel current under zero bias. Losses in …

Improving Scoliosis Rehabilitation, Ryan Neufeld

Mechanical and Aerospace Engineering Theses - Archive

Scoliosis, a disease that mainly affects children, is a deformity of the spinal column in all three dimensions. Treatment for scoliosis aims at straightening the spine with minimal discomfort to the patient. Current treatments involve wearing a polymeric brace that based on its design, exerts force on the spine in order to straighten it. The shape of the brace and the locations where the brace should apply forces are defined based on the experience of the orthotics specialist. Currently used braces are not equipped with sensors to monitor the loads generated and possibly aid in the rehabilitation process. The rehabilitation …

Computational Study Of Data Center Hotspot Mitigation With Snorkels As An Alternative Rack-Level Containment Strategy, Chris Onyiorah

Mechanical and Aerospace Engineering Theses - Archive

One of the major concerns of companies around the world is business continuity and with that comes the need to prevent operational dysfunction by keeping their information systems available and functional. IT professionals therefore, are constantly striving towards network sustainability by boosting the cooling cycle and infrastructure in data centers, while also reducing overall energy consumption. The combination of increasing IT workloads and packaging densities place stringent requirements on data center cooling systems and so, various traditional airflow management technologies have been implemented that propose significant energy savings and potential reduction in net annual cost for running data centers.In this …

Data Center Cooling Augmentation Using Micro-Encapsulated Phase Change Material, Ruddhi Shashikumar Deshmukh

Mechanical and Aerospace Engineering Theses - Archive

The ever increasing information technology heat load and data center cooling energy are the main reasons to investigate the performance of microencapsulated phase change slurry over other heat transfer fluids. In recent years, more effort is being made on the development of a new technique to use the phase change materials as pump-able heat transfer fluid and as heat storage system. Thermal Energy Storage (TES) using Phase Change Materials for data centers offers a very effective method of cutting electric power costs for owners and easing demand on the power grid. Thermal storage systems have been around for decades and …

Phoresis Of A Solid Particle In Real Fluid, Yuan Ting Wu

Mechanical and Aerospace Engineering Dissertations - Archive

For micro- and nano-scale particles driven by interfacial non-contact forces in fluid, known as phoresis, this dissertation provides a general formulation and a systematic investigation. It starts with an analytical continuum-mechanics formulation that covers various important aspects of an interfacial structure, including viscosity and mass density variations as well as a body force field, in real fluid. It then reduces to specific solutions due to characteristic mechanisms. A closed-form analytical solution to the case of viscosity variation (which manifests itself as Navier's slip boundary condition) is derived. Furthermore, a novel mechanism for thermophoretic mobility driven by near-surface phase transition is …

Moving Obstacle Detection And Avoidance For Unmanned Ground Vehicle, Gangadhar Rajashekaraiah

Mechanical and Aerospace Engineering Theses - Archive

This thesis presents the development and implementation of an autonomous obstacle avoidance algorithm for UGV (Unmanned Ground Vehicle). The research improves the prior work by enhancing the obstacle avoidance capability to handle moving obstacle as well as stationary obstacles. A mathematical representation of the area of operation with obstacles is formulated by PTEM (Probabilistic Threat Exposure Map). The PTEM quantifies the risk in being at a position in an area with different types of threat. Threat in this context means UGV getting close to or running into stationary and moving obstacles. A LRF (Laser Range Finder) sensor mounted on the …

Computational Flow Analysis Of A Flapping Micro-Flyer Wing For Cycle-Averaged Force Production, Nitesh Rajendra Rajput

Mechanical and Aerospace Engineering Theses - Archive

Human engineers have been trying long to mimic creations of nature for their own benefits. One such area of interest is the insect based micro flapping wing flyers for their wide employment in commercial as well as military applications. These micro air vehicles (MAVs) are capable of performing acts that can be too dangerous for humans to perform, such as tactical reconnaissance in a combat zone. The maneuverability required of these MAVs call for a careful design and thorough study of their aerodynamic performance. This research goal is to provide an estimation of the forces generated during the flapping motion …

Scaling Laws For Radial Foil Bearings, Srikanth Honavara Prasad

Mechanical and Aerospace Engineering Theses - Archive

The effects of fluid pressurization, structural deformation of the compliant members and heat generation in foil bearings make the design and analysis of foil bearings very complicated. The complex fluid-structural-thermal interactions in foil bearings also make modeling efforts challenging because these phenomena are governed by highly non-linear partial differential equations. Consequently, comparison of various bearing designs require detailed calculation of the flow fields (velocities, pressures), bump deflections (structural compliance) and heat transfer phenomena (viscous dissipation in the fluid, frictional heating, temperature profile etc.,) resulting in extensive computational effort(time/hardware). To obviate rigorous computations and aid in feasibility assessments of foil bearings …

Precipitation, Orientation And Composition Effects On The Shape Memory Properties Of High Strength Nitihfpd Alloys, Emre Acar

Theses and Dissertations--Mechanical and Aerospace Engineering

NiTiHf high temperature shape memory alloys are attractive due to their high operating temperatures (>100 ^oC) and acceptable transformation strain compared to NiTi. However, NiTiHf has limitations due to their lack of ductility and low strength, resulting in poor shape memory properties. In this study, Pd has been added to NiTiHf alloys in an attempt to improve their shape memory behavior. A combined approach of quaternary alloying and precipitation strengthening was used.

The characterization of a Ni_45.3Ti_29.7Hf₂₀Pd₅ (at. %) polycrystalline alloy was performed in compression after selected aging treatments. Transmission electron …

A Design Pathfinder With Material Correlation Points For Inflatable Systems, Jared T. Fulcher

Theses and Dissertations--Mechanical and Aerospace Engineering

The incorporation of inflatable structures into aerospace systems can produce significant advantages in stowed volume to mechanical effectiveness and overall weight. Many applications of these ultra-lightweight systems are designed to precisely control internal or external surfaces, or both, to achieve desired performance. The modeling of these structures becomes complex due to the material nonlinearities inherent to the majority of construction materials used in inflatable structures. Furthermore, accurately modeling the response and behavior of the interfacing boundaries that are common to many inflatable systems will lead to better understanding of the entire class of structures. The research presented involved using nonlinear …

Filtered-Dynamic-Inversion Control For Fixed-Wing Unmanned Aerial Systems, Jon Mullen

Theses and Dissertations--Mechanical and Aerospace Engineering

Instrumented umanned aerial vehicles represent a new way of measuring turbulence in the atmospheric boundary layer. However, autonomous measurements require control methods with disturbance-rejection and altitude command-following capabilities. Filtered dynamic inversion is a control method with desirable disturbance-rejection and command-following properties, and this controller requires limited model information. We implement filtered dynamic inversion as the pitch controller in an altitude-hold autopilot. We design and numerically simulate the continuous-time and discrete-time filtered-dynamic-inversion controllers with anti-windup on a nonlinear aircraft model. Finally, we present results from a flight experiment comparing the filtered-dynamic-inversion controller to a classical proportional-integral controller. The experimental results show …

Multidimensional Modeling Of Pyrolysis Gas Transport Inside Orthotropic Charring Ablators, Haoyue Weng

Theses and Dissertations--Mechanical and Aerospace Engineering

During hypersonic atmospheric entry, spacecraft are exposed to enormous aerodynamic heat. To prevent the payload from overheating, charring ablative materials are favored to be applied as the heat shield at the exposing surface of the vehicle. Accurate modeling not only prevents mission failures, but also helps reduce cost. Existing models were mostly limited to one-dimensional and discrepancies were shown against measured experiments and flight-data. To help improve the models and analyze the charring ablation problems, a multidimensional material response module is developed, based on a finite volume method framework. The developed computer program is verified through a series of test-cases, …