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- Adaptive Control (7)
- Control System Synthesis (4)
- Learning Systems (4)
- Iterative Methods (3)
- Neurocontrollers (3)
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- Optimal Control (3)
- Feedback (2)
- Motion Control (2)
- Nonlinear Control Systems (2)
- Solid Freeform Fabrication (2)
- Time-Varying Systems (2)
- 3-D Modeling (1)
- 3D Modeling (1)
- Accerleration Control (1)
- Adaptive Critic Design (1)
- Adaptive Extrusion Force Control (1)
- Aeroelastic Analysis (1)
- Air Conditioning (1)
- Aluminum (1)
- Arc Welding (1)
- Binders (1)
- Boundary-Value Problems (1)
- Ceramic Paste Extrusion (1)
- Closed Loop Systems (1)
- Computational Argumentation (1)
- Conflict Resolution (1)
- Contour Reconstruction (1)
- Control Engineering Computing (1)
- Convergence (1)
- Convergence of Numerical Methods (1)
Articles 1 - 29 of 29
Full-Text Articles in Mechanical Engineering
Determination Of Vibrational Energy Levels And Transition Dipole Moments Of Co2 Molecules By Density Functional Theory, Zhi Liang, Hai-Lung Tsai
Determination Of Vibrational Energy Levels And Transition Dipole Moments Of Co2 Molecules By Density Functional Theory, Zhi Liang, Hai-Lung Tsai
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An Efficient Method is Presented to Calculate the Intra-Molecular Potential Energies and Electrical Dipole Moments of CO2 Molecules at the Electronic Ground State by Solving the Kohn-Sham (KS) Equation for a Total of 101 992 Nuclear Configurations. the Projector-Augmented Wave (PAW) Exchange-Correlation Potential Functionals and Plane Wave (PW) Basis Functions Were Used in Solving the KS Equation. the Calculated Intra-Molecular Potential Function Was Then Included in the Pure Vibrational Schrödinger Equation to Determine the Vibrational Energy Eigen Values and Eigen Functions. the Vibrational Wave Functions Combined with the Calculated Dipole Moment Function Were Used to Determine the Transition Dipole Moments. …
A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai
A Plasma Model Combined With An Improved Two-Temperature Equation For Ultrafast Laser Ablation Of Dielectrics, Lan Jiang, Hai-Lung Tsai
Mechanical and Aerospace Engineering Faculty Research & Creative Works
It remains a big challenge to theoretically predict the material removal mechanism in femtosecond laser ablation. To bypass this unresolved problem, many calculations of femtosecond laser ablation of nonmetals have been based on the free electron density distribution without the actual consideration of the phase change mechanism. However, this widely used key assumption needs further theoretical and experimental confirmation. by combining the plasma model and improved two-temperature model developed by the authors, this study focuses on investigating ablation threshold fluence, depth, and shape during femtosecond laser ablation of dielectrics through nonthermal processes (the Coulomb explosion and electrostatic ablation). The predicted …
Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai
Three-Dimensional Modeling Of The Plasma Arc In Arc Welding, Gu Xu, J. Hu, Hai-Lung Tsai
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell's equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as …
High Bandwidth Control Of Precision Motion Instrumentation, Douglas A. Bristow, Jingyan Dong, Andrew G. Alleyne, Srinivasa M. Salapaka, Placid M. Ferreira
High Bandwidth Control Of Precision Motion Instrumentation, Douglas A. Bristow, Jingyan Dong, Andrew G. Alleyne, Srinivasa M. Salapaka, Placid M. Ferreira
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This article presents a high-bandwidth control design suitable for precision motion instrumentation. Iterative learning control (ILC), a feedforward technique that uses previous iterations of the desired trajectory, is used to leverage the repetition that occurs in many tasks, such as raster scanning in microscopy. Two ILC designs are presented. The first design uses the motion system dynamic model to maximize bandwidth. The second design uses a time-varying bandwidth that is particularly useful for nonsmooth trajectories such as raster scanning. Both designs are applied to a multiaxis piezoelectric-actuated flexure system and evaluated on a nonsmooth trajectory. The ILC designs demonstrate significant …
Adaptive Control Of Freeze-Form Extrusion Fabrication Processes, Xiyue Zhao, Robert G. Landers, Ming-Chuan Leu
Adaptive Control Of Freeze-Form Extrusion Fabrication Processes, Xiyue Zhao, Robert G. Landers, Ming-Chuan Leu
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing process that extrudes high solids loading aqueous ceramic pastes in a layer-by-layer fashion below the paste freezing temperature for component fabrication. Due to effects such as the air bubble release, agglomerate breakdown, change in paste properties during extrusion as a result of liquid phase migration, etc., the extrusion force is difficult to control. In this paper, an adaptive controller is proposed to regulate the extrusion force. Recursive Least Squares is used to estimate extrusion force model parameters during fabrication and a low-order control scheme capable of tracking general reference trajectories is designed …
Freeform Fabrication Of Zirconium Diboride Parts Using Selective Laser Sintering, Ming-Chuan Leu, Erik B. Adamek, Tieshu Huang, Greg Hilmas, Fatih Dogan
Freeform Fabrication Of Zirconium Diboride Parts Using Selective Laser Sintering, Ming-Chuan Leu, Erik B. Adamek, Tieshu Huang, Greg Hilmas, Fatih Dogan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Using the Selective Laser Sintering (SLS) process, both flexural test bars and 3D fuel injector components have been fabricated with zirconium diboride (ZrB2) powder. Stearic acid was selected as the binder. Values of SLS process parameters were chosen such that the green parts could be built with sharp geometrical features and that the sintered parts could have good mechanical properties. After binder burnout and sintering, the SLS fabricated ZrB2 test bars achieved 80% theoretical density, and the average flexural strength of the sintered samples was 195 MPa. These values demonstrate the feasibility of the SLS process for …
Direct 3d Layer Metal Deposition, Jianzhong Ruan, Lie Tang, Todd E. Sparks, Robert G. Landers, Frank W. Liou
Direct 3d Layer Metal Deposition, Jianzhong Ruan, Lie Tang, Todd E. Sparks, Robert G. Landers, Frank W. Liou
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Multi-axis slicing for solid freeform fabrication (SFF) manufacturing processes can yield non-uniform thickness layers, or 3D layers. Using the traditional parallel layer construction approach to build such a layer leads to a staircase which requires machining or other post processing to form the desired shape. This paper presents a direct 3D layer deposition approach. This approach uses an empirical model to predict the layer thickness based on experimental data. The toolpath between layers is not parallel; instead, it follows the final shape of the designed geometry and the distance between the toolpath in the adjacent layers varies at different locations. …
Direct-To-Part Machining Waste Recycling Using Laser Metal Deposition, Todd E. Sparks, Frank W. Liou
Direct-To-Part Machining Waste Recycling Using Laser Metal Deposition, Todd E. Sparks, Frank W. Liou
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Laser metal deposition typically uses metal powders as the build material of choice. The ability to reprocess waste materials using this technology would significantly reduce the material cost and cradle-to-grave energy content of parts produced using these methods. This capability will also greatly increase the utility of laser deposition, to potential industrial uses. This paper explores the usage of machining chips as an alternate source of build material. Topics covered include material handling, material preprocessing, and comparison to powder- based deposition.
Layer-To-Layer Height Control For Laser Metal Deposition Processes, Lie Tang, Jianzhong Ruan, Todd E. Sparks, Robert G. Landers, Frank W. Liou
Layer-To-Layer Height Control For Laser Metal Deposition Processes, Lie Tang, Jianzhong Ruan, Todd E. Sparks, Robert G. Landers, Frank W. Liou
Mechanical and Aerospace Engineering Faculty Research & Creative Works
A Laser Metal Deposition (LMD) height controller design methodology is presented in this paper. The height controller utilizes the Particle Swarm Optimization (PSO) algorithm to estimate model parameters between layers using measured temperature and track height profiles. The process model parameters for the next layer are then predicted using Exponentially Weighted Moving Average (EWMA). Using the predicted model, the powder flow rate reference profile, which will produce the desired layer height reference, is then generated using Iterative Learning Control (ILC). The model parameter estimation capability is tested using a four-layer deposition. The results demonstrate the simulation based upon estimated process …
Modeling And Experimental Results Of Concentration With Support Material In Rapid Freeze Prototyping, Frances D. Bryant, Ming-Chuan Leu
Modeling And Experimental Results Of Concentration With Support Material In Rapid Freeze Prototyping, Frances D. Bryant, Ming-Chuan Leu
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Ice structures with complex geometries and overhung areas are created by the Rapid Freeze Prototyping (RFP) process in a sufficiently cool environment by freezing water into ice as the main material in conjunction with a eutectic dextrose-water solution as the sacrificial support material. The supported areas in an ice structure are removed via an increase in temperature in a separate environment after the structure is completely fabricated. To understand to what extent these two materials mix during fabrication, two methods of modeling the concentration changes that occur near the interface of the main and support materials have been developed. The …
Microstructural Characterization Of Diode Laser Deposited Ti-6al-4v, Tian Fu, Zhiqiang Fan, Syamala R. Pulugurtha, Todd E. Sparks, Jianzhong Ruan, Frank W. Liou, Joseph William Newkirk
Microstructural Characterization Of Diode Laser Deposited Ti-6al-4v, Tian Fu, Zhiqiang Fan, Syamala R. Pulugurtha, Todd E. Sparks, Jianzhong Ruan, Frank W. Liou, Joseph William Newkirk
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Laser Direct Metal Deposition (DMD) is an effective approach to manufacturing or repairing a range of metal components. The process is a layer-by-layer approach to building up a three dimensional solid object. The microstructure influences mechanical properties of the deposited parts. Thus, it is important to understand the microstructural features of diode laser deposited parts. This paper presents a microstructure analysis of a diode laser deposited Ti-6Al-4V onto a Ti-6Al-4V substrate. laser deposited parts. This paper presents a microstructure analysis of a diode laser deposited Ti-6Al-4V onto a Ti-6Al-4V substrate.
Product Focused Freeform Fabrication Education, Frank W. Liou, Ming-Chuan Leu
Product Focused Freeform Fabrication Education, Frank W. Liou, Ming-Chuan Leu
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Presented in this paper is our experience of teaching freeform fabrication to students at the Missouri University of Science and Technology, and to high school students and teachers. The emphasis of the curriculum is exposing students to rapid product development technologies with the goal of creating awareness to emerging career opportunities in CAD/CAM. Starting from solid modeling, principles of freeform fabrication, to applications of rapid prototyping and manufacturing in industry sponsored product development projects, students can learn in-depth freeform fabrication technologies. Interactive course content with hands-on experience for product development is the key towards the success of the program.
Reinforcement Learning Based Dual-Control Methodology For Complex Nonlinear Discrete-Time Systems With Application To Spark Engine Egr Operation, Peter Shih, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Reinforcement Learning Based Dual-Control Methodology For Complex Nonlinear Discrete-Time Systems With Application To Spark Engine Egr Operation, Peter Shih, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Electrical and Computer Engineering Faculty Research & Creative Works
A novel reinforcement-learning-based dual-control methodology adaptive neural network (NN) controller is developed to deliver a desired tracking performance for a class of complex feedback nonlinear discrete-time systems, which consists of a second-order nonlinear discrete-time system in nonstrict feedback form and an affine nonlinear discrete-time system, in the presence of bounded and unknown disturbances. For example, the exhaust gas recirculation (EGR) operation of a spark ignition (SI) engine is modeled by using such a complex nonlinear discrete-time system. A dual-controller approach is undertaken where primary adaptive critic NN controller is designed for the nonstrict feedback nonlinear discrete-time system whereas the secondary …
Issues On Stability Of Adp Feedback Controllers For Dynamical Systems, S. N. Balakrishnan, Jie Ding, F. L. Lewis
Issues On Stability Of Adp Feedback Controllers For Dynamical Systems, S. N. Balakrishnan, Jie Ding, F. L. Lewis
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper traces the development of neural-network (NN)-based feedback controllers that are derived from the principle of adaptive/approximate dynamic programming (ADP) and discusses their closed-loop stability. Different versions of NN structures in the literature, which embed mathematical mappings related to solutions of the ADP-formulated problems called “adaptive critics” or “action-critic” networks, are discussed. Distinction between the two classes of ADP applications is pointed out. Furthermore, papers in “model-free” development and model-based neurocontrollers are reviewed in terms of their contributions to stability issues. Recent literature suggests that work in ADP-based feedback controllers with assured stability is growing in diverse forms.
A New Contour Reconstruction Approach From Dexel Data In Virtual Sculpting, Kemal Yuksek, Weihan Zhang, Boryslaw Iwo Ridzalski, Ming-Chuan Leu
A New Contour Reconstruction Approach From Dexel Data In Virtual Sculpting, Kemal Yuksek, Weihan Zhang, Boryslaw Iwo Ridzalski, Ming-Chuan Leu
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper presents a novel method of contour reconstruction from dexel data solving the shape anomalies for the complex geometry in virtual sculpting. Grouping and traversing processes are developed to find connectivity between dexels along every two adjacent rays. After traveling through all the rays on one slice, sub-boundaries are connected into full boundaries which are desired contours. The complexity of the new method has been investigated and determined as O(n). We also demonstrate the ability of the described method for viewing a sculpted model from different directions.
Sulphur-Tolerant Anode For Solid Oxide Fuel Cell, David J. Bayless, Jason P. Trembly
Sulphur-Tolerant Anode For Solid Oxide Fuel Cell, David J. Bayless, Jason P. Trembly
Mechanical and Aerospace Engineering Faculty Research & Creative Works
An anode for a solid oxide fuel cell. The anode is not harmed by sulfur-containing compounds, nor is its resistance increased thereby. The anode has two layers, including a “protective” layer (A) and a layer (B) that oxidizes molecular hydrogen The protective layer has a diffusion rate for molecular hydrogen that exceeds its diffusion rate for sulfur-containing compounds, and has an oxidation rate for sulfur-containing compounds that exceeds its oxidation rate for molecular hydrogen. The first anode layer can be selected fro the group of Lanthanum Strontium Titanate (LST) and Lanthanum Strontium Vanadate (LSV), and the second anode layer is …
Frequency Domain Analysis And Design Of Iterative Learning Control For Systems With Stochastic Disturbances, Douglas A. Bristow
Frequency Domain Analysis And Design Of Iterative Learning Control For Systems With Stochastic Disturbances, Douglas A. Bristow
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In this work we examine the performance of iterative learning control (ILC) for systems with non-repeating disturbances and random noise. Single-input, single- output linear time-invariant systems and iteration-invariant learning filters are considered. We find that a tradeoff exists between the convergence rate and converged error spectrum. Optimal filter designs, which are dependant on the disturbance and noise spectra, are developed. We also present simple design guidelines for the case when explicit models of disturbance and noise spectra are not available. A numerical design example is presented.
Formation Control Of Car-Like Mobile Robots: A Lyapunov Function Based Approach, S. A. Panimadai Ramaswamy, S. N. Balakrishnan
Formation Control Of Car-Like Mobile Robots: A Lyapunov Function Based Approach, S. A. Panimadai Ramaswamy, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In literature leader - follower strategy has been used extensively for formation control of car-like mobile robots with the control law being derived from the kinematics. This paper takes it a step further and a nonlinear control law is derived using Lyapunov analysis for formation control of car-like mobile robots using robot dynamics. Controller is split into two parts. The first part is the development of a velocity controller for the follower from the error kinematics (linear and angular). The second part involves the use of the dynamics of the robot in the development of a torque controller for both …
Weighting Matrix Design For Robust Monotonic Convergence In Norm Optimal Iterative Learning Control, Douglas A. Bristow
Weighting Matrix Design For Robust Monotonic Convergence In Norm Optimal Iterative Learning Control, Douglas A. Bristow
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In this paper we examine the robustness of norm optimal ILC with quadratic cost criterion for discrete-time, linear time-invariant, single-input single-output systems. A bounded multiplicative uncertainty model is used to describe the uncertain system and a sufficient condition for robust monotonic convergence is developed. We find that, for sufficiently large uncertainty, the performance weighting can not be selected arbitrarily large, and thus overall performance is limited. To maximize available performance, a time-frequency design methodology is presented to shape the weighting matrix based on the initial tracking error. The design is applied to a nanopositioning system and simulation results are presented.
Design Of A Linear Time-Varying Cross-Coupled Iterative Learning Controller, K. L. Barton, Douglas A. Bristow, Andrew G. Alleyne
Design Of A Linear Time-Varying Cross-Coupled Iterative Learning Controller, K. L. Barton, Douglas A. Bristow, Andrew G. Alleyne
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In many manufacturing applications contour tracking is more important than individual axis tracking. Many control techniques, including iterative learning control (ILC), target individual axis error. Because individual axis error only indirectly relates to contour error, these approaches may not be very effective for contouring applications. Cross-coupled ILC (CCILC) is a variation on traditional ILC that targets the contour tracking directly. In contour trajectories with rapid changes, high frequency control is necessary in order to meet tracking requirements. This paper presents an improved CCILC that uses a linear time-varying (LTV) filter to provide high frequency control for short durations. The improved …
Optimal Controller Synthesis Of Variable-Time Impulsive Problems Using Single Network Adaptive Critics, Xiaohua Wang, S. N. Balakrishnan
Optimal Controller Synthesis Of Variable-Time Impulsive Problems Using Single Network Adaptive Critics, Xiaohua Wang, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper presents a systematic approach to solve for the optimal control of a variable-time impulsive system. First, optimality condition for a variable-time impulsive system is derived using the calculus of variations method. Next, a single network adaptive critic technique is proposed to numerically solve for the optimal control and the detailed algorithm is presented. Finally, two examples-one linear and one nonlinear-are solved applying the conditions derived and the algorithm proposed. Numerical results demonstrate the power of the neural network based adaptive critic method in solving this class of problems.
Optimal Neuro-Controller Synthesis For Variable-Time Impulse Driven Systems, Xiaohua Wang, S. N. Balakrishnan
Optimal Neuro-Controller Synthesis For Variable-Time Impulse Driven Systems, Xiaohua Wang, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
This paper develops a systematic scheme to solve for the optimal controls of variable time impulsive systems. First, the optimality conditions for variable time impulse driven systems are derived using the calculus of variation. After wards, a neural network based adaptive critic method is proposed to numerically solve the two-point boundary value problems formulated based on the optimality conditions derived. Finally, two examples - one linear and one nonlinear - are presented to illustrate the conditions derived and to show the power of the neural network based adaptive critic method proposed.
Incorporation Of Evidences Into An Intelligent Computational Argumentation Network For A Web-Based Collaborative Engineering Design System, Xiaoqing Frank Liu, Ekta Khudkhudia, Ming-Chuan Leu
Incorporation Of Evidences Into An Intelligent Computational Argumentation Network For A Web-Based Collaborative Engineering Design System, Xiaoqing Frank Liu, Ekta Khudkhudia, Ming-Chuan Leu
Computer Science Faculty Research & Creative Works
Conflicts among the stakeholders are unavoidable in the process of collaborative engineering design. Resolution of these conflicts is a challenging task. In our previous research, a web based intelligent collaborative system was developed which provides decision-making support, using computational argumentation techniques. Enhancements were done to this system to incorporate the priorities of the stakeholders and to detect arguments that self conflict. As an effort to make this system more effective and more objective in the process of decision making, we develop a method to assess the effect of evidences in the argumentation network, using Dempster-Shafer theory of evidence and fuzzy …
Mixing Effectiveness Of Various Damper-Plenum Configurations, Harry J. Sauer, Pankaj Hande, Fathi Finaish
Mixing Effectiveness Of Various Damper-Plenum Configurations, Harry J. Sauer, Pankaj Hande, Fathi Finaish
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Improper mixing of outside air and return air streams in building air conditioning systems has been recognized for years. The problems may lead to nuisance cycling, frequent freeze-stat trips and serious consequences of a frozen or ruptured conditioning coil. It was thought that typical solutions for the problem usually consist of preferred placement of outside air and return air duct penetrations to the mixing box, manipulation of the inlet damper angles and velocity ratio between the outside air and return air streams and the insertion of static flow mixers in the mixing box to help improve the thermal stratification. This …
Monotonic Convergence Of Iterative Learning Control For Uncertain Systems Using A Time-Varying Filter, Douglas A. Bristow, Andrew G. Alleyne
Monotonic Convergence Of Iterative Learning Control For Uncertain Systems Using A Time-Varying Filter, Douglas A. Bristow, Andrew G. Alleyne
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Iterative learning control (ILC) is a learning technique used to improve the performance of systems that execute the same task multiple times. Learning transient behavior has emerged as an important topic in the design and analysis of ILC systems. In practice, the learning control is often low-pass filtered with a ldquoQ-filterrdquo to prevent transient growth, at the cost of performance. In this note, we consider linear time-invariant, discrete-time, single-input single-output systems, and convert frequency-domain uncertainty models to a time-domain representation for analysis. We then develop robust monotonic convergence conditions, which depend directly on the choice of the Q-filter and are …
Output Feedback Controller For Operation Of Spark Ignition Engines At Lean Conditions Using Neural Networks, Jonathan B. Vance, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Output Feedback Controller For Operation Of Spark Ignition Engines At Lean Conditions Using Neural Networks, Jonathan B. Vance, Brian C. Kaul, Jagannathan Sarangapani, J. A. Drallmeier
Electrical and Computer Engineering Faculty Research & Creative Works
Spark ignition (SI) engines operating at very lean conditions demonstrate significant nonlinear behavior by exhibiting cycle-to-cycle bifurcation of heat release. Past literature suggests that operating an engine under such lean conditions can significantly reduce NO emissions by as much as 30% and improve fuel efficiency by as much as 5%-10%. At lean conditions, the heat release per engine cycle is not close to constant, as it is when these engines operate under stoichiometric conditions where the equivalence ratio is 1.0. A neural network controller employing output feedback has shown ability in simulation to reduce the nonlinear cyclic dispersion observed under …
Micromachined Nanoporous Membranes For Blood Oxygenation Systems, Vijayakrishnan Ambravaneswaran, Susheil Uttamaraj, Zeynep Çelik-Butler, Robert C. Eberhart, Charles J. Chuong, Richard E. Billo, Michael A. Savitt
Micromachined Nanoporous Membranes For Blood Oxygenation Systems, Vijayakrishnan Ambravaneswaran, Susheil Uttamaraj, Zeynep Çelik-Butler, Robert C. Eberhart, Charles J. Chuong, Richard E. Billo, Michael A. Savitt
Mechanical and Aerospace Engineering Faculty Research & Creative Works
Nanostructured membranes with precisely engineered nanopores were fabricated on a thin silicon nitride membrane, using a combination of bulk micromachining and focused-ion-beam drilling. These membranes are designed to preserve microscale blood channel dimensions, thereby permitting the red cell shape change that enhances gas exchange in the pulmonary capillary. The membranes were tested for their mechanical stability and the results were verified with finite element analysis. Initial studies have proven the membranes to be robust, and capable of withstanding pressures typically experienced in blood oxygenator channels. A novel MEMS-based blood oxygenation system employing the nanoporous membranes is also presented. The oxygenation …
Nonlinear H(Infinity) Missile Longitudinal Autopilot Design With Theta-D Method, Ming Xin, S. N. Balakrishnan
Nonlinear H(Infinity) Missile Longitudinal Autopilot Design With Theta-D Method, Ming Xin, S. N. Balakrishnan
Mechanical and Aerospace Engineering Faculty Research & Creative Works
In this paper, a new nonlinear H 1 control technique, called μ¡D H 1 method, is employed to design a missile longitudinal autopilot. The μ ¡D H 1 design has the same structure as that of linear H 1 , except that the two Riccati equations that are part of the solution process are state dependent. The μ ¡D technique yields suboptimal solutions to nonlinear optimal control problems in the sense that it provides an approximate solution to the Hamilton-Jacobi-Bellman (HJB) equation. It is also shown that this method can be used to provide an approximate closed-form solution to the …
Efficient Uncertainty Quantification Applied To The Aeroelastic Analysis Of A Transonic Wing, Serhat Hosder, Robert W. Walters, Michael Balch
Efficient Uncertainty Quantification Applied To The Aeroelastic Analysis Of A Transonic Wing, Serhat Hosder, Robert W. Walters, Michael Balch
Mechanical and Aerospace Engineering Faculty Research & Creative Works
The application of a Point-Collocation Non-Intrusive Polynomial Chaos method to the uncertainty quantification of a stochastic transonic aeroelastic wing problem has been demonstrated. The variation in the transient response of the first aeroelastic mode of a three-dimensional wing in transonic flow due to the uncertainty in free-stream Mach number and angle of attack was studied. A curve-fitting procedure was used to obtain time-independent parameterization of the transient aeroelastic responses. Among the uncertain parameters that characterize the time-dependent transients, the damping factor was chosen for uncertainty quantification, since this parameter can be thought as an indicator for flutter. Along with the …