Motivated by the interests to understand bio-structure deformation and exploit their advantages to create bio-inspired systems for engineering applications, a curvature-based model for analyzing compliant mechanisms capable of large deformation in a three dimensional space has been developed. Unlike methods (such as finite element) that formulate problems based on displacements and/or rotational angles, superposition holds for curvatures in the case of finite rotation but not for rotational angles; thus the curvature-based formulation presents an advantage in presenting nonlinear geometries. Along with a generalized constraint that relaxes traditional boundary constraints (such as fixed, pinned or sliding constraint) on compliant mechanisms, the method of deriving the compliant members in the same global referenced frame is presented. The attractive features of the method, which greatly simplifies the models and improves the computation efficiency of multi-body system deformation where compliant beams play an important role, have been experimentally validated. To demonstrate the applicability of this proposed method to a broad spectrum of applications, three practical examples are given; the first example verifies the generalized constraint by analyzing the multi-axis rotation motion within a natural human knee joint and investigates the human-exoskeleton interactions through dynamic analysis. The second example studies a deformable bio-structure by incorporating the generalized joint constraint into the curvature-based model for automated poultry meat processing. The last example designs a bio-inspired robot with a compliant mechanism to serve as a flexonic mobile node for ferromagnetic structure health monitoring. The analytical models have been employed (with experimental validation) to investigate the effects of different joint constraints on the mechanism deformations. It is expected that the proposed method will find a broad range of applications involving compliant mechanisms.

The overall goal of my research was to advance our understanding of the potential for novel compliant flooring systems to reduce the risk for fall-related injuries in older adults, including fall-related traumatic brain injury (TBI). This entailed an assessment of how these floors affect the competing demands of fall-related TBI – impact severity attenuation in concert with minimal concomitant impairments to balance control and postural stability. Two studies are included as part of this thesis. The first study used a mechanical drop tower to assess the effects of four traditional flooring systems and six novel compliant flooring conditions on the impact dynamics of a surrogate headform during the impact phase of simulated ‘worst- case’ head impacts. The second study entailed an assessment of the effect of two traditional and three novel compliant floors on the initial phase of the compensatory balance reactions of older adult men and women living in a residential-care facility environment following an externally induced perturbation using a tether-release paradigm. Overall, this thesis demonstrates that novel compliant floors substantially attenuate the forces and accelerations applied to the head during simulated worst- case impacts when compared to traditional flooring surfaces such as vinyl and carpet with underpadding. These benefits are achieved without compromising indices of balance control, supported by the finding that parameters characterizing early compensatory balance reactions were unaffected by the novel compliant floors tested. This work supports the introduction of pilot installations of novel compliant flooring systems into environments with high incidences of falls to test their effectiveness at reducing fall-related injuries in clinical settings.

Cellular structures are present from the atomic level all the way up to patterns found in human skeleton. They are prevailing structures in the nature and known for their excellent mechanical, thermal, and acoustic properties. Two typical types of cellular structures, lightweight structures and compliant mechanisms, are investigated. Lightweight structures are rigid and designed to reduce weight, while increasing strength and stiffness. Compliant mechanisms are designed to transform motions and forces. Most available artificial lightweight structures are patterns of primitives. However, the performance of lightweight structures can be enhanced by using adaptive cellular structures with conformal strut orientations and sizes, like the trabeculae in femoral bone. Bending, torsion, and nonlinear behaviors of compliant mechanisms have not been sufficiently studied. In order to design adaptive cellular structures, a new unit cell, the unit truss is proposed. The unit truss approach facilitates the design of adaptive cellular structures for enhanced mechanical properties via geometric modeling, finite element analysis, shape optimization, and additive fabrication. Four research questions, which address representation, structural analysis, design synthesis, and manufacturing respectively, are raised and answered. Unit truss enables representation and mechanics analysis for adaptive cellular structures. A synthesis method using engineering optimization algorithms is developed to systematically design adaptive cellular structure. Two examples, graded cellular structure for prosthesis and compliant mechanism for morphing wings, are studied to test the unit truss approach.

The aim of this study is to design a compliant lock mechanism for a dishwasher, using a systematic approach. Functionally binary pinned-pinned segment that exhibits bistable behavior is utilized. Pseudo-rigid-body model of the whole mechanism and the half segment is developed separately and the corresponding calculations are carried out. Among current solutions a different method namely &ldquo / arc fitting method&rdquo / is developed and it is utilized to construct the model. A software code is written to get the exact solutions, which require the evaluation of elliptic integrals. Results are compared with the analytical model and confirmed with physical prototype. Predefined tip forces are seen to provide the transition from one stable position to other. Durability, reliability and compactness characteristics are particularly considered.

This thesis develops a finite element based dynamic modeling method for design and analysis of compliant mechanisms which transfer input force, displacement and energy through elastic deformations. Most published analyses have largely based on quasi-static and lump-parameter models neglecting the effects of damping, torsion, complex geometry, and nonlinearity of deformable contacts. For applications such as handling of objects by the robotic hands with multiple high-damped compliant fingers, there is a need for a dynamic model capable of analyzing the flexible multibody system. This research begins with the formulation of the explicit dynamic finite element method (FEM) which takes into account the effects of damping, complex geometry and contact nonlinearity. The numerical stability is considered by evaluating the critical time step in terms of material properties and mesh quality. A general framework incorporating explicit dynamic FEM, topology optimization, modal analysis, and damping identification has been developed. Unlike previous studies commonly focusing on geometry optimization, this research considers both geometric and operating parameters for evaluation where the dynamic performance and trajectory of the multibody motion are particularly interested. The dynamic response and contact behavior of the rotating fingers acting on the fixed and moving objects are validated by comparing against published experimental results. The effectiveness of the dynamic modeling method, which relaxes the quasi-static assumption, has been demonstrated in the analyses of developing an automated transfer system involved grasping and handling objects by the compliant robotic hands. This FEM based dynamic model offers a more realistic simulation and a better understanding of the multibody motion for improving future design. It is expected that the method presented here can be applied to a spectrum of engineering applications where flexible multibody dynamics plays a significant role.

This paper presents designs for Multistable Shape-Shifting Surfaces (MSSS) by introducing bistability into the Shape-Shifting Surface (SSS). SSSs are defined as surfaces that retain their effectiveness as a physical barrier while undergoing changes in shape. The addition of bistability to the SSS gives the surface multiple distinct positions in which it remains when shifted to, i.e. by designing bistability into a single SSS link, the SSS unit cell can change into multiple shapes, and stabilize within the resulting shape, while maintaining integrity against various forms of external assaults normal to its surface. Planar stable configurations of the unit cell include, expanded, compressed, sheared, half-compressed, and partially-compressed, resulting in the planar shapes of a large square, small square, rhombus, rectangle, and trapezoid respectively. Tiling methods were introduced which gave the ability to produce out-of-plane assemblies using planar MSSS unit cells. A five-walled rigid storage container prototype was produced that allowed for numerous stable positions and volumes. Applications for MSSSs can include size-changing vehicle beds, expandable laptop screens, deformable walls, and volume-changing rigid-storage containers. Analysis of the MSSS was done using pseudo-rigid-Body Models (PRBMs) and Finite Element Analysis (FEA) which ensured bistable characteristics before prototypes were fabricated.

In order to operate safely and naturally in human-centered environments, robots need to respond compliantly to force and contact interactions. While advanced robotic torsos and arms have been built that successfully achieve this, a somewhat neglected research area is the construction of compliant wheeled mobile bases. This thesis describes the mechatronics behind Trikey, a holonomic wheeled mobile base employing torque sensing at each of its three omni wheels so that it can detect and respond gracefully to force interactions. Trikey's mechanical design, kinematic and dynamic models, and control architecture are described, as well as simple experiments demonstrating compliant control. Trikey is designed to support a force-controlled humanoid upper body, and eventually, the two will be controlled together using whole-body control algorithms that utilize the external and internal dynamics of the entire system. / text

No description available.

Conventional solder balls used in microelectronic packaging suffer from thermo- mechanical damage due to difference in coefficient of thermal expansion between the die and the substrate or the substrate and the board. Compliant interconnects are replacements for solder balls which accommodate this differential displacement by mechanically decoupling the die from the substrate or the substrate from the board and aim to improve overall reliability and life of the microelectronic component. Research is being conducted to develop compliant interconnect structures which offer good mechanical compliance without adversely affecting electrical performance, thus obtaining good thermo-mechanical reliability. However, little information is available regarding the behavior of compliant interconnects under shock and impact loads. The objective of this thesis is to study the response of a proposed multi-path compliant interconnect structure when subjected to shock and impact loading. As part of this work, scaled-up substrate-compliant interconnect-die assemblies will be fabricated through stereolithography techniques. These scaled-up prototypes will be subjected to experimental drop testing. Accelerometers will be placed on the board, and strain gauges will be attached to the board and the die at various locations. The samples will be dropped from different heights to different shock levels in the components, according to Joint Electron Devices Engineering Council (JEDEC) standards. In parallel to such experiments with compliant interconnects, similar experiments with scaled-up solder bump interconnects will also be conducted. The strain and acceleration response of the compliant interconnect assemblies will be compared against the results from solder bump interconnects. Simulations will also be carried out to mimic the experimental conditions and to gain a better understanding of the overall response of the compliant interconnects under shock and impact loading. The findings from this study will be helpful for improving the reliability of compliant interconnects under dynamic mechanical loading.

The overall goal of my research was to advance our understanding of the potential for novel compliant flooring systems to reduce the risk for fall-related injuries in older adults, including fall-related traumatic brain injury (TBI). This entailed an assessment of how these floors affect the competing demands of fall-related TBI – impact severity attenuation in concert with minimal concomitant impairments to balance control and postural stability. Two studies are included as part of this thesis. The first study used a mechanical drop tower to assess the effects of four traditional flooring systems and six novel compliant flooring conditions on the impact dynamics of a surrogate headform during the impact phase of simulated ‘worst- case’ head impacts. The second study entailed an assessment of the effect of two traditional and three novel compliant floors on the initial phase of the compensatory balance reactions of older adult men and women living in a residential-care facility environment following an externally induced perturbation using a tether-release paradigm. Overall, this thesis demonstrates that novel compliant floors substantially attenuate the forces and accelerations applied to the head during simulated worst- case impacts when compared to traditional flooring surfaces such as vinyl and carpet with underpadding. These benefits are achieved without compromising indices of balance control, supported by the finding that parameters characterizing early compensatory balance reactions were unaffected by the novel compliant floors tested. This work supports the introduction of pilot installations of novel compliant flooring systems into environments with high incidences of falls to test their effectiveness at reducing fall-related injuries in clinical settings.