Mechanical Engineering Commons^™

High Fidelity Dynamic Modeling And Nonlinear Control Of Fluidic Artificial Muscles, Jonathon Earl Slightam

Dissertations (1934 -)

A fluidic artificial muscle is a type of soft actuator. Soft actuators transmit power with elastic or hyper-elastic bladders that are deformed with a pressurized fluid. In a fluidic artificial muscle a rubber tube is encompassed by a helical fiber braid with caps on both ends. One of the end caps has an orifice, allowing the control of fluid flow in and out of the device. As the actuator is pressurized, the rubber tube expands radially and is constrained by the helical fiber braid. This constraint results in a contractile motion similar to that of biological muscles. Although artificial muscles …

Hip Joint Function In People With Femoroacetabular Impingement Syndrome, Philip Malloy

Dissertations (1934 -)

Femoroacetabular impingement syndrome (FAIS) is a clinical hip disorder that represents symptomatic contact between the proximal femur and rim of the acetabulum during normal hip range of motion. FAIS has been described as a precursor to hip joint osteoarthritis (OA), and results in physical impairments and functional limitations in young individuals and active adults. Despite tremendous growth in arthroscopic hip surgery for FAIS, little is known about how this disorder affects dynamic hip joint function. The purpose of this dissertation was to investigate hip joint function, during clinical and functional activities, both before and after arthroscopic hip surgery for FAIS. …

Analytical Modeling Of A Novel Microdisk Resonator For Liquid-Phase Sensing: An All-Shear Interaction Device (Asid), Mohamad Sadegh Sotoudegan

Dissertations (1934 -)

Extensive research on micro/nanomechanical resonators has been performed recently due to their potential to serve as ultra-sensitive devices in chemical/biosensing. These applications often necessitate liquid-phase sensing, introducing significant fluid-induced inertia and energy dissipation that reduces the resonator’s performance. To minimize the detrimental fluid effects on such devices, a novel microdisk resonator supported by two tangentially-oriented, axially-driven “legs” is investigated analytically and effects of the system parameters on the resonator/sensor performance are explored. Since the device surface vibrates primarily parallel to the fluid-structure interface, it is referred to here as an “all-shear interaction device,” or ASID. Analytical modeling of the ASID …

Health Condition Monitoring And Fault-Tolerant Operation Of Adjustable Speed Drives, Jiangbiao He

Dissertations (1934 -)

Adjustable speed drives (ASDs) have been extensively used in industrial applications over the past few decades because of their benefits of energy saving and control flexibilities. However, the wider penetration of ASD systems into industrial applications is hindered by the lack of health monitoring and fault-tolerant operation techniques, especially in safety-critical applications. In this dissertation, a comprehensive portfolio of health condition monitoring and fault-tolerant operation strategies is developed and implemented for multilevel neutral-point-clamped (NPC) power converters in ASDs. Simulations and experiments show that these techniques can improve power cycling lifetime of power transistors, on-line diagnosis of switch faults, and fault-tolerant …

Dynamic Modeling Of Human Gait Using A Model Predictive Control Approach, Jinming Sun

Dissertations (1934 -)

This dissertation aims to develop a dynamic model of human gait, especially the working principle of the central nervous system (CNS), using a novel predictive approach. Based on daily experience, it should be straightforward to understand the CNS controls human gait based on predictive control. However, a thorough human gait model using the predictive approach have not yet been explored. This dissertation aims to fill this gap. The development of such a predictive model can assist the developing of lower limb prostheses and orthoses which typically follows a trial and error approach. With the development of the predictive model, lower …

Mechatronics Design Process With Energy Optimization For Industrial Machines, Aderiano Medeiros Da Silva

Dissertations (1934 -)

The need for designing industrial machines with higher energy efficiency, reliability, flexibility, and accuracy has increased to satisfy market demand for higher productivity at reduced costs in a sustainable manner. As machines become more complex, model-based design is essential to overcome the challenges in mechatronic system design. However, a well-designed mechanical system with a well-designed and tuned control system are not sufficient for machines to operate at high-performance conditions; this also heavily depends on trajectory planning and the appropriate selection of the motors controlling the axes of the machine. In this work, a model-based design approach to properly select motors …

A Hybrid Controller For Stability Robustness, Performance Robustness, And Disturbance Attenuation Of A Maglev System, Feng Tian

Dissertations (1934 -)

Devices using magnetic levitation (maglev) offer the potential for friction-free, high-speed, and high-precision operation. Applications include frictionless bearings, high-speed ground transportation systems, wafer distribution systems, high-precision positioning stages, and vibration isolation tables. Maglev systems rely on feedback controllers to maintain stable levitation. Designing such feedback controllers is challenging since mathematically the electromagnetic force is nonlinear and there is no local minimum point on the levitating force function. As a result, maglev systems are open-loop unstable. Additionally, maglev systems experience disturbances and system parameter variations (uncertainties) during operation. A successful controller design for maglev system guarantees stability during levitating despite system …

Nanogap Device: Fabrication And Applications, Jun Hyun Han

Dissertations (1934 -)

A nanogap device as a platform for nanoscale electronic devices is presented. Integrated nanostructures on the platform have been used to functionalize the nanogap for biosensor and molecular electronics. Nanogap devices have great potential as a tool for investigating physical phenomena at the nanoscale in nanotechnology. In this dissertation, a laterally self-aligned nanogap device is presented and its feasibility is demonstrated with a nano ZnO dot light emitting diode (LED) and the growth of a metallic sharp tip forming a subnanometer gap suitable for single molecule attachment.

For realizing a nanoscale device, a resolution of patterning is critical, and many …

Plastic Deformation Investigation Of High Energy Input Friction, Tao Yan

Dissertations (1934 -)

In this dissertation, plastic deformation of friction surfaces under high energy input is investigated. The plastic deformation of the friction surface and subsurface was studied and models were established to estimate deformation.

In order to calculate the plastic deformation at friction surface, an algorithm based on Ramberg-Osgood relationship was generated, and a single material model was developed based on this algorithm. Work hardening caused by plastic deformation and thermal softening caused by elevated temperature were considered in the model. To validate the model, an apparatus was designed to perform friction tests under different conditions. A special steel specimen with a …

Theoretical Analysis Of Torsionally Vibrating Microcantilevers For Chemical Sensor Applications In Viscous Liquids, Tao Cai

Dissertations (1934 -)

Dynamically driven microcantilevers excited in the transverse (or out-of-plane) direction are widely used as highly sensitive chemical sensing platforms in various applications. While these devices work very well in air, their performance in liquids is not efficient because of the combination of increased viscous damping and effective fluid mass. In order to improve the characteristics of microcantilevers in liquid environments, some other vibration modes such as the torsional mode and lateral (or in-plane) flexural mode have been proposed.
In this work, the characteristics of torsionally vibrating rectangular microcantilevers with length L, width b and thickness h in viscous liquids are …

Profile Synthesis Of Planar Variable Joints, Brian James Slaboch

Dissertations (1934 -)

Reconfigurable mechanisms provide quick changeover and reduced costs for low volume manufacturing applications. In addition, these mechanisms provide added flexibility in the context of a constrained environment. A subset of planar reconfigurable mechanisms use variable joints to provide this added adaptability.

In this dissertation, the profile synthesis of planar variable joints that change from a rotational motion to a translational motion was investigated. A method was developed to perform automated profile synthesis. It was shown that combinations of higher variable joints can be used to create kinematically equivalent variable joints that are geometrically different.

The results were used to create …

Analysis Of Laminated Anisotropic Plates And Shells Via A Modified Complementary Energy Principle Approach, Martin Claude Domfang

Dissertations (1934 -)

The present work is concerned with the finite element structural analysis of laminated anisotropic plates and shells. New elements based on a modified complementary energy principle are proposed to improve the analysis of such composite structures. Third order deformation plate and shell models incorporating a convergence parameter are developed to govern the general displacement field.

An eight-node isoparametric quadrilateral element with two independent cross-sectional rotations and three normal displacements is utilized to describe the displacement field. The present modified complementary energy formulation incorporates a number of in-plane strain functions of various orders. The corresponding in-plane stresses for each lamina are …

Direct Numeric Simulation Of Shock Wave Structures Without The Use Of Artificial Viscosity, Kenneth Bernard Jordan

Dissertations (1934 -)

The purpose of this work is to directly simulate shock wave structures without the use of artificial viscosity. The commonly used artificial viscosity model is replaced with an irreversibility model. Irreversibilities are not typically taken into account when modeling the shock processes because shocks are resolved in a large domain where the thickness of the shock is thin compared to the numeric grid resolution. The result is the shock is poorly resolved. In addition processes other than shock processes are adiabatic and reversible. The result is artificial viscosity, a form of irreversibility, is added to the numeric cells near the …

The Effect Of Cryogenic Treatment On The Fatigue Life Of Chrome Silicon Steel Compression Springs, Debra Lynn Smith

Dissertations (1934 -)

The purpose of this dissertation is to explore the effect of cryogenic treatment on the fatigue life of compression springs. Product manufacturers are constantly searching for ways to make their products last longer. This dissertation addresses three questions: (1) What is the effect of cryogenic treatment on the fatigue life of chrome silicon steel compression springs? Does the life increase, decrease, or remain the same? (2) What is the effect of cryogenic treatment on the Percent Load Loss (Stress Relaxation) of chrome silicon steel compression springs? (3) What are the possible changes in the material that cause these effects?

The …

Determination Of Cap Model Parameters Using Numerical Optimization Method For Powder Compaction, Cong Lu

Dissertations (1934 -)

Many advantages are inherent to the successful powder metallurgy (P/M) process especially in high volume manufacturing. The strength/density distribution of the compacted product is crucial to overall success. The finite element analysis (FEA) method has become an effective way to numerically simulate strength/density distribution in a P/M compact. The modified Drucker-Prager cap (DPC) model has been shown to be a suitable constitutive relationship for metal powder compaction simulation. The calibration of the modified DPC model involves a procedure known as a triaxial compression test. Equipment for completing a triaxial compression test on metal powders is neither readily available nor standardized …