The objective of this thesis is to develop an analysis approach for formulation of transduction or input/output representations for magnetostrictive actuators. This transduction model is developed through application of an electro-magneto-mechanical impedance modeling approach which combines both the mechanical dynamics and coupled behavior of the actuator device. Lumped and continuous mechanical impedance elements model the actuator dynamics and the constitutive relationships for Terfenol-D characterize the electro-magneto-mechanical interaction. Experimental analysis of a Terfenol-D actuator serves to verify the developed models and provides an indication of actuator non-linearity. The developed transduction model allows for various device behavior analysis including dissipative power consumption, force and stroke output, and efficiency as a transducer. An actuator design strategy based upon the dynamics of the actuator and a driven external system is presented and allows for analysis of various actuator behaviors in terms of device parameters. The Terfenol-D actuator as a collocated actuator/sensor is also made possible with the transduction model. / Master of Science

The harmonic excitation of simply supported Euler plates is performed experimentally using arrays of piezoceramic patch pair actuators bonded to the plate surface. The experimental techniques used are presented, and the effects of patch location, relative actuator phasing, and excitation frequency on modal excitation are demonstrated. In addition, experimental results are compared to a previously developed closed-form solution which predicts the modal distribution due to such excitation. Finally, a finite element model of a simpler 2-D case of beam actuation is employed to illustrate the effects of the adhesive layers between the patches and structure on modal excitation. Results show that the closed-form solution is capable of predicting both the relative modal distribution and absolute modal amplitudes for different experimental configurations and indicate that with knowledge of the system resonant frequencies and nodal lines, experimental parameters such as excitation frequency, patch location, and relative patch phasing can be logically manipulated to produce a desired vibrational response. The results of the finite element analysis reveal that the net effect of the finite adhesive layer depends on both the stiffness and thickness of the layer, and that increasing either of these parameters can result in multiple consequences, which can combine to positively or negatively affect modal excitation levels. / Master of Science

Epoxy composite laminated piezoelectric stress-enhanced actuators (ECLIPSE) have been developed for potential applications by the United States Air Force and others. This class of actuators offers several advantages over other unimorph actuators such as lighter weight, design flexibility, and short production time. Anisotropic differential thermal expansion is utilized in the design of the actuators to achieve large out-of-plane curvature and place the brittle piezoelectric ceramic in residual compression. The numerous composite material choices and configurations can be used to control characteristics of the actuator such as radius of curvature and force output. ECLIPSE actuators were characterized during this study. They were made from layers of Kevlar 49/epoxy composite and a lead zirconate titanate ceramic (PZT) plate. All ECLIPSE actuators tested were built with a PZT plate with the same dimensions and material, but had different layup configurations. By changing the stacking order of the composite and PZT material, characteristics of the actuator were altered. The performance of each ECLIPSE actuator was compared. The maximum achievable displacement of each actuator was measured by cyclically applying an electric field at low frequency between zero and the maximum electric field allowable for the piezoelectric material. The frequency was also increased to a resonance condition to characterize the fatigue behavior of these actuators. In addition, the force output of various actuators was measured with a four-point bending apparatus. The experimental data was compared to a classical lamination theory model and an extended classical lamination theory model. These models were used to predict actuator behavior as well as to calculate the stress and strain distribution through the thickness of the actuator.

Recent advancements in actuator technologies, computation, and control have led to major leaps in capability and have brought humanoids ever closer to being feasible solutions for real-world applications. As the capabilities of humanoids increase, they will be called on to operate in unstructured real world environments. This realization has driven researchers to develop more dynamic, robust, and adaptable robots. Compared to state-of-the-art robots, biological systems demonstrate remarkably better efficiency, agility, adaptability, and robustness. Many recent studies suggest that a core principle behind these advantages is compliance, yet there are very few compliant humanoids that have demonstrated successful walking. The work presented in this dissertation is based on several years of developing novel actuators for two full-scale linearly actuated compliant humanoid robots, SAFFiR and THOR. Both are state-of-the-art robots intended to operate in the extremely challenging real world scenarios of shipboard firefighting and disaster response. The design, modeling, and control of actuators in robotics application is critical because the rest of the robot is often designed around the actuators. This dissertation seeks to address two goals: 1) advancing the design of compliant linear actuators that are well suited for humanoid applications, and 2) developing a better understanding of how to design and model compliant linear actuators for use in humanoids. Beyond just applications for compliant humanoids, this research tackles many of the same design and application challenges as biomechanics research so it has many potential applications in prosthetics, exoskeletons, and rehabilitation devices. / Ph. D.

Nessa pesquisa é apresentada uma inovação tecnológica em aplicações de controle de posição em máquinas e/ou dispositivos: o Controlador de Posição Linear Hidro- Pneumático. Para os casos nos quais têm-se grandes esforços combinados com pequenos deslocamentos, normalmente esse trabalho é feito com o uso de Sistemas Servo-Hidráulcos nos quais, devido às características mencionadas do nicho de mercado visado pela presente proposta, representam um custo elevado quando comparado com a solução Hidro-Pneumática aqui descrita. Salienta-se a simplicidade da infra-estrutura requerida para a instalação dessa alternativa, e também a redução do desperdício energético com relação à tecnologia tradicional com a Servo-Hidráulica. Observou-se nos testes com o protótipo, um excelente desempenho do sistema em termos de rapidez de resposta, como ainda no quesito resolução de posicionamento cujos valores encontrados apresentam-se na casa de 0,05 segundos e 0,01 mm, respectivamente. O pequeno tamanho físico obtido com essa nova tecnologia é outro item relevante, permitindo-se o seu emprego em locais de reduzido espaço disponível. . Resultados de simulações numéricas e de testes experimentais são apresentadas, bem como perspectivas de desenvolvimentos futuros. / This research presents a technological innovation for applications in machine / device position control: the Hydro-Pneumatic Linear Position controller. In cases where great efforts are combined with small dislocations, this task is normally accomplished by means of Servo Hydraulic Systems that, due to particular characteristics of the market envisaged by the present proposition, represent elevated costs, when compared to those of the hydro-pneumatic solution described here. This work presents an analytical numerical model for the devise as well as an experimental prototype. It worth noting the infra-structure simplicity required for this alternative implementation, and also the reduction in energy waste when compared to the traditional servo-hydraulic technology. The prototype experimental tests demonstrated the system excellent behavior in what concerns answer speed and position resolution whose values were respectively in range 0.05 s and 0,01 mm. The small physical size obtained with this technology is another relevant item, which allows the device use in places of reduced available space. Numerical simulation and experimental test results are presented as well as perspectives of future developments

Nessa pesquisa é apresentada uma inovação tecnológica em aplicações de controle de posição em máquinas e/ou dispositivos: o Controlador de Posição Linear Hidro- Pneumático. Para os casos nos quais têm-se grandes esforços combinados com pequenos deslocamentos, normalmente esse trabalho é feito com o uso de Sistemas Servo-Hidráulcos nos quais, devido às características mencionadas do nicho de mercado visado pela presente proposta, representam um custo elevado quando comparado com a solução Hidro-Pneumática aqui descrita. Salienta-se a simplicidade da infra-estrutura requerida para a instalação dessa alternativa, e também a redução do desperdício energético com relação à tecnologia tradicional com a Servo-Hidráulica. Observou-se nos testes com o protótipo, um excelente desempenho do sistema em termos de rapidez de resposta, como ainda no quesito resolução de posicionamento cujos valores encontrados apresentam-se na casa de 0,05 segundos e 0,01 mm, respectivamente. O pequeno tamanho físico obtido com essa nova tecnologia é outro item relevante, permitindo-se o seu emprego em locais de reduzido espaço disponível. . Resultados de simulações numéricas e de testes experimentais são apresentadas, bem como perspectivas de desenvolvimentos futuros. / This research presents a technological innovation for applications in machine / device position control: the Hydro-Pneumatic Linear Position controller. In cases where great efforts are combined with small dislocations, this task is normally accomplished by means of Servo Hydraulic Systems that, due to particular characteristics of the market envisaged by the present proposition, represent elevated costs, when compared to those of the hydro-pneumatic solution described here. This work presents an analytical numerical model for the devise as well as an experimental prototype. It worth noting the infra-structure simplicity required for this alternative implementation, and also the reduction in energy waste when compared to the traditional servo-hydraulic technology. The prototype experimental tests demonstrated the system excellent behavior in what concerns answer speed and position resolution whose values were respectively in range 0.05 s and 0,01 mm. The small physical size obtained with this technology is another relevant item, which allows the device use in places of reduced available space. Numerical simulation and experimental test results are presented as well as perspectives of future developments

Doctor of Philosophy / Department of Chemistry / Christopher T. Culbertson / During the last five years, great advancements in microfluidics have been achieved with the development of “sample-in-answer-out” systems. Such systems have begun to realize the true potential of analytical miniaturization since the concept of the “micro-Total Analysis System” was first envisioned. These systems are characterized by the elegant integration of multiple fluid-handling channel architectures that enable serial execution of sample preparation, separation and detection techniques on a single device. While miniaturization and portability are often identified as key advantages for microfluidics, these highly integrated systems are heavily reliant upon large off-chip equipment, i.e. the microchip is often tethered to the laboratory via multiple syringe pumps, vacuum pumps, solenoid valves, gas cylinders and high voltage power supplies. In this dissertation, a procedure for the facile integration of dielectric elastomer (DE) actuators (called IDEAs) onto microfluidic devices is described. Poly(dimethylsiloxane) (PDMS) is commonly used as a microchip substrate because it is cheap and easy to fabricate, mechanically robust and optically transparent. The operation of an IDEA exploits the ability of PDMS to behave as a smart material and deform in the presence of an electric field. In Chapter 2, the fabrication of IDEA units on a standard microchip electrophoresis device is described. IDEA-derived injections were used to evaluate the physical performance of this novel actuator configuration. In Chapter 3, the analytical merits of IDEA-derived injections were evaluated. Sampling bias caused by electokinetic injection techniques has been problematic for conventional microchip electrophoresis systems due to the lack of fluid access. The hydrodynamic injections created by IDEA operation were found to be highly reproducible, efficient, and possess a negligible degree of sampling bias. In Chapter 4, the spatial characteristics of microchannel deformation due to IDEA actuation have been investigated using fluorescence microscopy. It was determined that the DE compresses more along the edge of the channel than in the middle of the channel. This information can be used to design a new generation of more efficient IDEAs.

Smartness of technical systems relies also on appropriate actuators and sensors. Different to the prevalent definition of smartness to be embedded machine intelligence, in this paper elegance and simplicity of solutions is postulated be a more uniform and useful characterization. This is discussed in view of the current trends towards cyber physical systems and the role of components and subsystems, as well as of models for their effective realization. Current research on actuators and sensing in the fluid power area has some emphasis on simplicity and elegance of solution concepts and sophisticated modeling. This is demonstrated by examples from sensorless positioning, valve actuation, and compact hydraulic power supply.

No description available.

We present work to transfer decentralized neuromuscular control strategies of human locomotion to powered segmented robotic legs. State-of-the-art robotic locomotion control approaches, like centralized planning and tracking in fully robotic systems and predefined motion pattern replay in prosthetic systems, do not enable the dynamism and reactiveness of able-bodied humans. Animals largely realize dexterous segmented leg performance with leg-encoded biomechanics and local feedback controls that bypass central processing. A decentralized neuromuscular controller was recently developed that enables robust locomotion for a simulated multi-segmented planar humanoid. A portion of this controller was used in an active ankle-foot prosthesis to modulate ankle torque during stance, enabling level and inclined ground walking. While these results suggest that the neuromuscular controller is a promising alternative control method for both fully robotic systems and powered prostheses, it is unclear if the controller can be transferred to multi-segmented robotic legs. The goal of this thesis is to investigate the feasibility of controlling a multi-segmented robotic leg with the proposed neuromuscular control approach, which may enable robots and powered prostheses to react to locomotion disturbances dynamically and in a human-like way. Specifically, work in this thesis investigates two hypotheses. Hypothesis one posits that the proposed decentralized swing-leg controllers enable more robust foot placements into ground targets than state-of-the-art impedance controls. Hypothesis two posits that neuromuscular swing-leg control enables more human-like motion than state-of-the-art impedance control. To transfer neuromuscular controls to powered segmented robotic legs, we use a model-based design approach. The initial transfer is focused on neuromuscular swing-leg controls, important for maintaining dynamic stability of both fully robotic systems and powered prostheses in the presence of unexpected locomotion disturbances, such as trips and pushes. We first present the design of RNL, a three segment, cable-driven, antagonistically actuated robotic leg with joint compliance. The robot’s size, weight, and actuation capabilities correspond to dynamically scaled human values. Next, a highfidelity simulation of the robot is created to investigate the feasibility of transferring neuromuscular controls, pre-tune hardware gains via optimization, and serve as a benchmark for hardware experiments. An idealized version of the swing-leg controller with mono-articular actuation, as well as the neuromuscular interpretation of this controller with multi-articular actuation is then transferred to RNL and evaluated with foot placement experiments. The results suggest that the proposed swing-leg controllers can accurately regulate foot placement of robotic legs during undisturbed and disturbed motions. Compared to impedance control, the proposed controls achieve foot placements over a range of ground targets with a single set of gains, which make them attractive candidates for regulating the motion of legged robots and prostheses in the real-world. Furthermore, the ankle trajectory traced out by the robot under neuromuscular control is more human-like than the trajectories traced out under the proposed idealized control and impedance control. In parallel to this control transfer, a synthesis method for creating compact nonlinear springs with user-defined torque-deflection profiles is presented to explore methods for improving RNL’s series elastic actuators. The springs use rubber as their elastic element, which, while enabling a compact spring design, introduce viscoelastic behavior in the spring that needs to be accounted for with additional control. To accurately estimate force developed in the rubber, an empirically characterized constitutive rubber model is developed and integrated into the series elastic actuator controller used by the RNL test platforms. Benchtop experiments show that in conjunction with an observer, the nonlinear spring prototype achieves desired behavior at actuation frequencies up to 2 Hz, after which spring behavior degrades due to rubber hysteresis. These results show that while the presented methodology is capable of realizing compact nonlinear springs, careful rubber selection that mitigates viscoelastic behavior is necessary during the spring design process.