Autism spectrum disorder (ASD) affects about 1.5 million individuals in the US alone. The consequences of ASD affect families, caregivers, and social structures. This thesis adds to a growing group of people performing research on mitigating the effects of autism through robotics. Children with ASD tend to interact with robots more easily than with other humans. The goal of robotic therapy is not to help children interact with robots, but to generalize the behavior to humans. An articulated spine is a key to human emotional expression through shaping, weight shifting, and flow. Despite this importance, this feature is all but lacking in robots. The primary contribution of this work is a novel 3-link planar spine with compliant, partial-gravity-compensating springs, capable of reproducing simple emotion-conveying poses for use in robot-based therapy for children with ASD. The design was based on the movements of expression experts using motion tracking markers. This information was used to optimize the number of links in the spine and their corresponding lengths. It is the goal of this research to make robotic therapy more effective for the children, raising the potential for life-changing results.

Bistable microrelays have many possible applications and have the potential to reduce the size, weight, power consumption, and cost of products in which they are used. This research outlines the current state of microrelays, presents three new compliant bistable micromechanisms, and characterizes their performance as microrelays. The characterization includes a treatment of a new force-tester, a preliminary contact resistance study, contact-force measurements, switching time measurements, insertion loss, AC isolation, breakdown voltage, and DC isolation. This document also includes recommendations for further research.

The objective of this thesis is to develop design approaches and models for prosthetic ankle joints using kinematic models of the human ankle and compliant mechanisms technology. Compliant mechanisms offer several potential design advantages over traditional rigid-body designs including high reliability and low cost. These design advantages are ideal for use in prosthetics. Some prosthetic ankle/foot systems currently on the market have multiple degrees of freedom yet are expensive. Additionally, even though these systems have multiple degrees of freedom, none of them are designed after the actual movements of the biological ankle. In this thesis a two, single degree-of-freedom hinge joint model, which is a kinematic model based on the biological ankle during walking, is used to develop compliant prosthetic ankle joints. The use of the model together with compliant mechanisms may provide the ability to develop highly functional prosthetic ankle joints at a lower cost than current high-performance prosthetic systems. Finally, a design approach for ankles may facilitate future development for knees, hips or other biological joints.

The purpose of this research is to investigate the use of compliant mechanisms in space applications and design, analyze, and test a compliant space mechanism. Current space mechanisms are already highly refined and it is unclear if significant improvements in performance can be made by continuing to refine current designs. Compliant mechanisms offer a promising opportunity to change the fundamental approach to achieving controlled motion in space systems and have potential for dramatic increases in mechanism performance given the constraints of the space environment. A compliant deployment hinge was selected for development after industry input was gathered. Concepts for large-displacement compliant hinges are investigated. A design process was developed that links the performance requirements of deployment to the design parameters of a deployment hinge. A large-displacement monolithic compliant rotational hinge, the Flex-16, is designed, analyzed, and tested. It was developed for possible application as a spacecraft deployment hinge and designs were developed using three different materials (polypropylene, titanium, and carbon nanotubes) and manufacturing processes (CNC milling, electron beam manufacturing metal rapid prototyping, and a carbon nanotube framework) on two size scales (macro and micro). A parametric finite element model allowed for prediction of prototype behavior before fabrication. The Flex-16 hinge is capable of 90 degrees of deflection without failure or contact and can be designed to meet industry requirements for space.

Despite many advances in the design methods for compliant mechanisms, it is still not possible to know if a set of user-specifications has a solution. Furthermore, practical considerations such as failure limits and manufacturing limitations cannot be easily incorporated into existing methods. To address these issues, we have recently developed the concept of feasible stiffness and inertia maps. This thesis extends the concept of feasible maps and proposes another kind of maps that comprehensively depict the nonlinear kinetoelastostatic behaviour of compliant mechanisms. Feasible maps drawn as per user-specifications, with compliant mechanisms of the database overlaid on it, instantly inform the reader whether the specifications are feasible; whether the specifications are stringent; whether any mechanisms in the database meet the specifications, and whether any mechanism can be interactively modified to meet the specifications including size, strength and manufacturability. This thesis extends the earlier work on feasible maps by relaxing one condition that all beam segments in a compliant mechanism must retain their relative proportions. This is achieved by using size optimization. Thus, a certain degree of automation is brought into the procedure, which enhances the ease of use of the feasible maps. Illustrative examples are presented and implementation into a software is demonstrated. A major contribution of this work is the development of the concept of kinetoelastostatic maps of compliant mechanisms with fixed topology, shape, and relative proportions of beam segments in them. The map is drawn on a 2D plot using two non-dimensional quantities, one that captures the response of the mechanism and the other that combines the force, geometry, and material parameters. The map encloses a region that indicates the kinetoelastostatic capability of the mechanism. Another contribution of this work is the observation that the enclosed region can be parameterized using average slenderness ratio of the beam segments. The resulting curves help designers in assessing the capability and limits of a mechanism in terms of geometric advantage, mechanical advantage, normalized output displacement, inherent stiffness, etc. Numerous examples are presented to explain various uses of the non-dimensional maps.

Compliant (flexible) structures play an important role in several biofluid problems including flow in the lungs, heart and arteries. Atherosclerosis is a vascular disease which causes a remodelling of the arterial wall causing a restriction (stenosis) by thickening the intima and the formation of vascular plaque by the deposit of fatty materials. This remodelling alters the compliance of the artery stiffening the arterial wall locally. A common location for this to occur is in the carotid artery which supplies blood to both the brain and the face. It can lead to complete occlusion of the artery in the extreme case and is a major cause of stroke and ischemic infarction. Stroke is the third largest cause of death in the U.S.A., but even if not fatal it can cause coma, paralysis, speech problems and dementia. Atherosclerosis causes a change in the local hemodynamics. It can produce areas of flow separation and low wall shear stress, which can lead to endothelial dysfunction and to promotion of plaque growth. In-vitro modelling with artificial flow phantoms allows the fluid mechanics of the circulatory system to be studied without the ethical and safety issues associated with animal and human experiments. Extensive work has been performed using both experimental and computational techniques to study rigid models representing the arterial system. Computational methods, in which the equations governing the flow and the elastic walls are coupled, are maturing. There is a lack of experimental data in compliant arterial systems to validate the numerical predictions. This thesis sets out to address the problems associated with the in vitro experimental analysis of compliant structures representing the human vasculature. A novel construction technique that produced idealised compliant geometries representing both a healthy and stenosed carotid artery from transparent silicone material was developed. A complete analysis was performed of the circumferential and longitudinal response of the geometry, which allowed for dynamic similarity between in vitro and in vivo conditions to be achieved. Inherent difficulties associated with thin walled phantom construction were overcome, which included the design of a novel endplate that allowed for a smooth transition from the flow system to the flow phantom and a bottom up silicone injection system that ensured the phantom was free of bubbles. The final phantom evolution had a wall thickness that could be produced to within a tolerance of 5%. The constructed flow phantom was ported to a flow system producing a physiological inlet flow waveform scaled to in vitro conditions via Reynolds and Womersley number matching. Experimental analysis was performed using a laser based optical technique, particle image velocimetry (PIV). A novel Light Emitting Diode (LED) illumination system was also implemented to obtain to obtain high speed planar PIV measurements. The combined set up of the LED light source, driver unit components and fibre optics for high speed imaging costs in the region of $US 650 which provides a far cheaper option in comparison to the pulse laser system (In the region of $US 50,000). Results obtained in the healthy geometry were compared to a rigid geometry with the same dimensions. It was found that compliance reduced the peak velocity experienced. It also caused a reduction in wall shear stress (WSS) observed and acted to ameliorate the magnitude of the WSS. This is physiologically significant as high WSS can promote atherosclerosis. The introduction of a stenosis caused an increase in the peak velocity observed over the cardiac cycle. A large increase in WSS can be seen to occur in the stenosis throat in both a symmetric and asymmetric stenosed geometry. It is also evident that stenosis eccentricity is important, with asymmetry (where the centre of the stenosis does not coincide with the centre of the artery) producing a major change in WSS and flow field. The study of the flow field downstream of a symmetric stenosis exit showed a Kelvin-Helmholtz vortex ring system to occur between the jet exiting the stenosis throat and the low velocity reverse flow region that surrounded it. The strength of these vortices varied between the acceleration and deceleration phase, demonstrating the failings of a quasi-steady assumption. It was shown that varying the external pressure applied to the flow phantom, along with stenosis eccentricity, affected the inlet flow and pressure waveform and the failings of the common assumption to idealise the physiological flow wave with a sinusoidal input was presented.

This thesis investigates the potential benefits and challenges of using compliant mechanisms in the design of haptic interfaces. The benefits and challenges are presented with an emphasis on their inherent springback behavior and an active compensation approach. Design criteria for compliant mechanism joint candidates are reviewed and several joints are surveyed. Quantitative calculations of axial stiffness and maximum stress for five candidates are presented. Generalized analytical models of springback force and compensation torque are created to simulate the implementation of each joint candidate in a two degree-of-freedom planar pantograph. We use these models in the development and discussion of an analytical approach to predict the motor torques needed to actively compensate for the effects of springback. This approach relies on virtual work analyses of the haptic pantograph to determine the springback forces, compensation torques, haptic workspace, and available haptic force after compensation. A key to estimating the available haptic force is knowing that the force capability is different depending on the local springback force. If a component of the desired haptic force aligns with the springback force, then the two can work together, thus increasing the maximum magnitude of available haptic force beyond the nominal amount. Analytical and experimental results are presented. A detailed method of implementation is given along with a hardware demonstration of active compensation.

This dissertation introduces a novel three-dimensional pseudo-rigid-body model (3-D PRBM) for straight cantilever beams with rectangular cross sections. The model is capable of capturing the behavior of the neutral axis of a beam loaded with an arbitrary force end-load. Numerical integration of a system of differential equations yields approximate displacement and orientation of the beam's neutral axis at the free end, and curvatures of the neutral axis at the fixed end. This data was used to develop the 3-D PRBM which consists of two torsional springs connecting two rigid links for a total of 2 degrees of freedom (DOF). The 3-D PRBM parameters that are comparable with existing 2-D model parameters are characteristic radius factor (mean: γ = 0.8322), bending stiffness coefficient (mean: KΘ = 2.5167) and parametric angle coefficient (mean: cΘ = 1.2501). New parameters are introduced in the model in order to capture the spatial behavior of the deflected beam, including two parametric angle coefficients (means: cΨ = 1.0714; cΦ = 1.0087). The model is verified in a few locations using ANSYSTM and its use in the design of compliant mechanisms is illustrated through spatial compliant versions of crank slider and double slider mechanisms.

This thesis presents a) a scheme for selecting the most suitable flexure hinge compliance equations, and b) a simple methodology of deriving kinetostatic models of micro-motion stages by incorporating the scheme mentioned above. There were various flexure hinge equations previously derived using different methods to predict the compliances of circular flexure hinges. However, some of the analytical/empirical compliance equations provide better accuracies than others depending on the t/R ratios of circular flexure hinges. Flexure hinge compliance equations derived previously using any particular method may not be accurate for a large range of t/R ratios. There was no proper scheme developed on how to select the most suitable and accurate hinge equation from the previously derived formulations. Therefore, the accuracies and limitations of the previously derived compliance equations of circular flexure hinges were investigated, and a scheme to guide designers for selecting the most suitable hinge equation based on the t/R ratios of circular flexure hinges is presented in this thesis. This thesis also presents the derivation of kinetostatic models of planar micromotion stages. Kinetostatic models allow the fulfillment of both the kinematics and the statics design criteria of micro-motion stages. A precise kinetostatic model of compliant micro-motion stages will benefit researchers in at least the design and optimisation phases where a good estimation of kinematics, workspace or stiffness of micro-motion stages could be realised. The kinetostatic model is also an alternative method to the finite-element approach which uses commercially available software. The modelling and meshing procedures using finite-element software could be time consuming. The kinetostatic model of micro-motion stages wasdeveloped based on the theory of the connection of serial and parallel springs. developed based on the theory of the connection of serial and parallel springs. The derivation of the kinetostatic model is simple and the model is expressed in closed-form equations. Material properties and link parameters are variables in this model. Compliances of flexure hinges are also one of the variables in the model. Therefore the most suitable flexure hinge equation can be selected based on the scheme aforementioned in order to calculate the kinetostatics of micro-motion stages accurately. Planar micro-motion stages with topologies of a four-bar linkage and a 3-RRR (revolute-revolute-revolute) structure were studied in this thesis. These micromotion stages are monolithic compliant mechanisms which consist of circular flexure hinges. Circular flexure hinges are used in most of the micro-motion stages which require high positioning accuracies. This is because circular flexure hinges provide predominantly rotational motions about one axis and they have small parasitic motions about the other axes. The 3-RRR micro-motion stage studied in this thesis has three-degrees-of-freedom (DOF). The 3-RRR stage consists of three RRR linkages and each RRR linkage has three circular flexure hinges. A Pseudo-Rigid-Body-Model (PRBM), a kinetostatic model and a two-dimensional finite-elementanalysis (FEA) model generated using ANSYS of micro-motion stages are presented and the results of these models were compared. Advantages of the kinetostatic model was highlighted through this comparison. Finally, experiments are presented to verify the accuracy of the kinetostatic model of the 3-RRR micromotion stage. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1289361 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007

Micro-motion devices may share a common architecture such that they have a main body of compliant material and some direct actuation elements (e.g., piezoelectric element). The shape of such a compliant material is designed with notches and holes on it, and in this way one portion of the material deforms significantly with respect to other portions of the material a motion in the conventional sense of the rigid body mechanism. The devices of this kind are called compliant mechanisms. Computer tools for the kinematical and dynamic motion analysis of the compliant mechanism are not well-developed. In this thesis a study is presented towards a finite element approach to the motion analysis of compliant mechanisms. This approach makes it possible to compute the kinematical motion of the compliant mechanism within which the piezoelectric actuation element is embedded, as opposed to those existing approaches where the piezoelectric actuation element is either ignored or overly simplified. Further, the developed approach allows computing the global stiffness and the natural frequency of the compliant mechanism. This thesis also presents a prototype compliant mechanism and a test bed for measuring various behaviors of the prototype mechanism. It is shown that the developed approach can improve the prediction of motions of the compliant mechanism with respect to the existing approaches based on a comparison of the measured result (on the prototype) and the simulated result. The approach to computation of the global stiffness and the natural frequency of the compliant mechanism is validated by comparing it with other known approaches for some simple mechanisms.