published_or_final_version / Industrial and Manufacturing Systems Engineering / Master / Master of Philosophy

Insects posses an incredible ability to navigate their environment at high speed, despite having small brains and limited visual acuity. Through selective pressure they have evolved computationally efficient means for simultaneously performing navigation tasks and instantaneous control responses. The insect’s main source of information is visual, and through a hierarchy of processes this information is used for perception; at the lowest level are local neurons for detecting image motion and edges, at the higher level are interneurons to spatially integrate the output of previous stages. These higher level processes could be considered as models of the insect's environment, reducing the amount of information to only that which evolution has determined relevant. The scope of this thesis is experimenting with biologically inspired visual control of flying robots through information processing, models of the environment, and flight behaviour. In order to test these ideas I developed a custom quadrotor robot and experimental platform; the 'wasp' system. All algorithms ran on the robot, in real-time or better, and hypotheses were always verified with flight experiments. I developed a new optical flow algorithm that is computationally efficient, and able to be applied in a regular pattern to the image. This technique is used later in my work when considering patterns in the image motion field. Using optical flow in the log-polar coordinate system I developed attitude estimation and time-to-contact algorithms. I find that the log-polar domain is useful for analysing global image motion; and in many ways equivalent to the retinotopic arrange- ment of neurons in the optic lobe of insects, used for the same task. I investigated the role of depth in insect flight using two experiments. In the first experiment, to study how concurrent visual control processes might be combined, I developed a control system using the combined output of two algorithms. The first algorithm was a wide-field optical flow balance strategy and the second an obstacle avoidance strategy which used inertial information to estimate the depth to objects in the environment - objects whose depth was significantly different to their surround- ings. In the second experiment I created an altitude control system which used a model of the environment in the Hough space, and a biologically inspired sampling strategy, to efficiently detect the ground. Both control systems were used to control the flight of a quadrotor in an indoor environment. The methods that insects use to perceive edges and control their flight in response had not been applied to artificial systems before. I developed a quadrotor control system that used the distribution of edges in the environment to regulate the robot height and avoid obstacles. I also developed a model that predicted the distribution of edges in a static scene, and using this prediction was able to estimate the quadrotor altitude.

A interação de várias substancias bioativas com monocamadas de fosfolipídios foi investigada usando isotermas de pressão e potencial de superfície, incluindo as drogas farmacológicas dipiridamol (DIP), clopromazina (CPZ) e trifluoperazina (TFP), além da melatonina (MEL) e o colesterol (COL). Os fosfolipídios empregados foram o zwiteriônico dipalmitoil fosfatidil colina (DPPC) e o aniônico dipalmitoil fosfatidil glicerol (DPPG) espalhados na superfície de água ultrapura, sendo que as monocamadas servem como modelo simples de membranas. A cooperatividade na interação entre fosfolipídios e moléculas com atividade biológica foi essencial para entender os acentuados efeitos na expansão (ou condensação) das monocamadas e as mudanças no momento de dipolo (até 10% de aumento na expansão em relação à monocamada do fosfolipídio puro para as misturas DIP/DPPC) que ocorreram a concentrações molares muito baixas entre 0,2-0,4% do DIP. Tais efeitos foram observados para todas as cinco substâncias investigadas, em todos os regimes de pressão. Nas altas concentrações, o comportamento da interação depende do tipo de mólecula e também de se a monocamada é de DPPC ou DPPG. Para o DPPC, as drogas farmacológicas foram expelidas da interface em vários graus a altas pressões, e existia um máximo de concentração da droga acima do qual ocorria a saturação, provavelmente porque as moléculas em excesso foram para a subfase. Essas concentrações críticas foram de 2% em mol para o DIP e a CPZ e de 5% em mol para a TFP. Para o DIP, em particular, os resultados das isotermas foram correlacionados com experimentos de espectroscopia de FTIR e microscopia de fluorescência \"in situ\", realizados por colaboradores, os quais permitiram a determinação de uma localização precisa da droga estudada. Não existe inserção do DIP na região da cauda hidrofóbica da monocamada do DPPC, com a interação ocorrendo com o grupo fosfato no zwiteríon, cujas pequenas mudanças na orientação induzidas pelo DIP levam a grandes mudanças no momento de dipolo. Como o DPPG está carregado negativamente sobre a superfície da água pura, não existe saturação nos efeitos de expansão com o aumento da concentração das drogas. O aumento do momento de dipolo efetivo na monocamada mista é atribuído a alterações na densidade de carga superficial pela adsorção da droga catiônica, que reduz a contribuição negativa do potencial da dupla camada, quando comparado com o da monocamada de DPPG puro. Os resultados do COL e a MEL devem ser considerados separadamente devido a sua natureza distinta, embora um comportamento cooperativo também tenha observado com grandes efeitos nas baixas concentrações. Tanto o COL como o MEL induzem mudanças na expansão das monocamadas de DPPC até a máxima concentração empregada, 20% molar. Para o COL foi observado um efeito de condensação a baixas concentrações, o qual foi seguido por uma expansão a altas concentrações, confirmando assim resultados prévios da literatura. Todas as monocamadas mistas COL/DPPG apresentavam-se expandidas, também confirmando alguns resultados da literatura para lipídios (diferentes do DPPC) quando misturados com o COL. A interação da MEL com o DPPC foi essencialmente similar à do COL, apesar do fato de a MEL pura não formar monocamadas estáveis. Sua interação com o DPPG foi peculiar já que o efeito que esta induz satura a 5% em mol. Isto também difere do comportamento das drogas farmacológicas. A MEL é neutra em todos os pHs, portanto, sua intenção com as membranas modelo de DPPG e DPPC só pode ocorrer via dipolo. O mesmo se aplica ao colesterol, o que justifica as diferenças no comportameto destas duas moléculas quando comparadas com as drogas (DIP, CPZ, TFP), que são carregadas sobre a água pura, nas misturas com os dois fosfolipídios (DPPG e DPPC). / The interaction of various bioactive substances with phospholipids monolayers has been investigated using surface pressure and surface potential isotherms, which include the pharmaceutical drugs dipyridamole (DIP), chlorpromazine (CPZ) and trifluoperazine (TFP), in addition to melatonin (MEL) and cholesterol (COL). The phospholipids employed were the zwitterionic dipalmitoyl phosphatidyl choline (DPPC) and the anionic dipalmitoyl phosphatidyl glycerol (DPPG) spread onto ultra pure water surfaces, where the monolayers served as simple model membrane systems. Cooperativity in the interaction between phospholipid and bioactive molecules was essential to account for the large effects of expansion (up to 10% increase in area in relation to the pure phospholipid monolayer for the DIP/DPPC mixture) of the monolayers and changes in dipole moment, which occurred at very low concentrations, e.g. 0.2 - 0.4 mol% of the substance. Such large effects were observed for all 5 substances investigated, at all surface pressure regimes. At higher concentrations, the interaction behavior depended on the type of molecule and also on whether the host monolayer was DPPC or DPPG. For DPPC, the pharmaceutical drugs were expelled at varying degrees from the interface at high surface pressures, and there was a maximum drug concentration above which the effects saturated, probably because the molecules in excess were lost to the subphase. These critical concentrations were 2mol% for DIP and CPZ and 5mol% for TFP. For DIP, in particular, the results from isotherm were correlated with in situ FTIR spectroscopy and fluorescent microscopy experiments, carried out by collaborators, which allowed the precise location of the drug to be determined. There is no insertion of DIP into the hydrophobic tail region of the DPPC monolayer, with interaction taking place with the phosphate group in the zwitterion, whose small changes in orientation induced by DIP lead to the large changes in dipole moment. Because DPPG is negatively charged on a pure water surface monolayer, there is no saturation of the expansion effects with the increase in drug concentration. The increase in the effective dipole moment of the mixed monolayers are attributed to alterations in the surface charge density by adsorption of the cationic drugs, which then reduces the negative contribution of the double-layer potential as compared to the pure DPPG monolayer. The results for COL and MEL must be considered separately owing to their distinct nature, even though a cooperative behavior was also observed with large effects at low concentrations. Both COL and MEL induce changes in the DPPC monolayers up to the highest concentration employed, viz. 20mol%. For COL, a condensation effect was observed at low concentrations, which was followed by monolayer expansion at high concentrations, thus confirming previous results in the literature. All COL/DPPG monolayers were more expanded than pure DPPG, also confirming previous results from the literature. While the interaction of MEL with DPPC was essentially similar to that of COL, in spite of the fact that MEL does not form stable monolayers on its own, its interaction with DPPG was somewhat peculiar in that the effects it induced saturate at 5mol%. This also differs from the behavior of the pharmaceutical drugs. MEL is neutral over a wide range of pHs, and therefore its interaction with DPPC and DPPG monolayers must occur via dipole interaction. The same applies to COL, and this explains why the behavior of these two substances is different from the drugs (DIP, CPZ and TFP) that are charged on the water surface, in the interaction with DPPC and DPPG.

Many domains, such as geographical and biological sciences, can benefit from the ability of wireless sensor networks to provide long term, high temporal and spatial resolution sensing. Such networks must be able to trade off various requirements against each other to extend network lifetime while still providing useful, good quality data. The challenges faced by equipment in the field can very unpredictable and therefore a wireless sensor network should be able to cope with these challenges and return to a balanced state. Using readily available, low-cost components, this work was inspired by the human endocrine systems ability to maintain homeostasis, or balance, in a large number of parameters simultaneously. This work developed a number of endocrine inspired methods. These were aimed both at improving the power usage of nodes in a wireless sensor network and improving the quality of the data collected. Methods for improving power consumption and data quality were achieved. These methods were successfully deployed, for the purposes of environmental monitoring on a mesh network consisting of 20 nodes, for a period of almost 6 months. Analysis showed that the use of power by individual nodes was improved and that the endocrine inspired methods, aimed at improving data quality, were successful. Node lifetimes were extended, duplicate data reduced and the quality of data improved. The use of low-cost, readily available components was largely successful, and challenges and changes to these components were discussed.

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Insects are confronted with the problem of locating food, mates, prey and hosts for their young over long distances, which they often overcome using chemical plume tracking. Tracking a plume of chemical back to its source is made difficult due to the complexity of plume structure. Turbulence and shifts in the wind direction prevail over diffusion in the spreading of an airborne chemical from a point in most cases, producing intricate plumes consisting of filaments of high chemical concentration interspersed with regions of clean air. It has been proposed that insects achieve plume tracking in this environment through variations of anemotaxis, which involves travelling upwind when an attractive chemical is perceived. This study aimed to investigate anemotaxis through the use of a mobile robot to test the efficacy of algorithms which mimic the way insects achieve plume tracking and also to determine whether these algorithms are an effective means of plume tracking for a mobile robot under a range of conditions. To achieve the aims of this study, various plume-tracking algorithms were implemented on a mobile robot built to model a plume-tracking insect and their performance was compared under a range of wind conditions. The algorithms tested were based upon a range of plume-tracking hypotheses. The simplest algorithm was surge anemotaxis, where the robot surged upwind in the presence of an attractive chemical and performed crosswind casting (back and forth motion) in the absence of chemical. The other algorithms tested were the counterturner, where the robot zigzagged upwind, and two bounded search methods. To allow these algorithms to be appropriately implemented, a robot model was constructed that could move in two dimensions and sense the wind velocity and ion level at a point in space. An ion plume was used instead of a chemical plume in each test as it behaves in a similar manner to a chemical plume, but ion sensors have response and recovery times far more rapid than conventional chemical sensors, similar to insects. The plume-tracking robot was tested in three series of tests. Initially, the entire range of plume-tracking algorithms was tested in a wind tunnel with fixed wind direction for a range of wind speeds and release positions. The second series of tests compared the performance of the surge anemotaxis and bounded search algorithms, again in a wind tunnel, but with a wind shift of 20° during some of the tests. The algorithms were tested with and without a direct crosswind surge response to detected wind shifts. The third set of tests examined the performance of the simple and wind shift response algorithms outdoors using natural wind to produce the plume. All algorithms tested achieved successful plume tracking in some conditions. The surge anemotaxis and triangular bounded search algorithms were particularly successful. The tests also showed that the paths obtained from tests undertaken in natural outdoor wind conditions varied greatly from those undertaken in a wind tunnel. This indicates the need to test plume-tracking algorithms in natural environments. This is vital both in the investigation of insect plume-tracking behaviour, as insects navigate in these environments, and in the process of producing plume-tracking robots that are capable of operating effectively in these conditions. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1287973 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2007

Despite the notable progress in physically-based rendering, there is still a long way to go before we can automatically generate predictable images of biological materials. In this thesis, we address an open problem in this area, namely the spectral simulation of light interaction with human skin, and propose a novel biophysically-based model that accounts for all components of light propagation in skin tissues, namely surface reflectance, subsurface reflectance and transmittance, and the biological mechanisms of light absorption by pigments in these tissues. The model is controlled by biologically meaningful parameters, and its formulation, based on standard Monte Carlo techniques, enables its straightforward incorporation into realistic image synthesis frameworks. Besides its biophysicallybased nature, the key difference between the proposed model and the existing skin models is its comprehensiveness, i. e. , it computes both spectral (reflectance and transmittance) and scattering (bidirectional surface-scattering distribution function) quantities for skin specimens. In order to assess the predictability of our simulations, we evaluate their accuracy by comparing results from the model with actual skin measured data. We also present computer generated images to illustrate the flexibility of the proposed model with respect to variations in the biological input data, and its applicability not only in the predictive image synthesis of different skin tones, but also in the spectral simulation of medical conditions.

Despite the notable progress in physically-based rendering, there is still a long way to go before we can automatically generate predictable images of biological materials. In this thesis, we address an open problem in this area, namely the spectral simulation of light interaction with human skin, and propose a novel biophysically-based model that accounts for all components of light propagation in skin tissues, namely surface reflectance, subsurface reflectance and transmittance, and the biological mechanisms of light absorption by pigments in these tissues. The model is controlled by biologically meaningful parameters, and its formulation, based on standard Monte Carlo techniques, enables its straightforward incorporation into realistic image synthesis frameworks. Besides its biophysicallybased nature, the key difference between the proposed model and the existing skin models is its comprehensiveness, i. e. , it computes both spectral (reflectance and transmittance) and scattering (bidirectional surface-scattering distribution function) quantities for skin specimens. In order to assess the predictability of our simulations, we evaluate their accuracy by comparing results from the model with actual skin measured data. We also present computer generated images to illustrate the flexibility of the proposed model with respect to variations in the biological input data, and its applicability not only in the predictive image synthesis of different skin tones, but also in the spectral simulation of medical conditions.

The use of examples in idea generation is a common practice intended to provide inspiration from existing products to the designing of new ones. Examples can be taken from the Internet, engineering textbooks, analogical databases, literature, a company’s prior designs, or from a competitor company, prior work by the designer, and many other sources. These examples are represented in various ways, such as hand sketches, pictures, computer-aided designs (CAD), physical models, activity diagrams, shape grammars, text descriptions, etc. Design representations can also be broken down by function in the form of functional models and decompositions. The use of these visual or physical examples allows engineers to get a clearer picture of how a design or component works and enables them to have a better understanding of the overall design and function. Each representation has inherent advantages and disadvantages in the way that they portray a design. Examples are sources for analogies. Analogies from nature, where biological organisms have solved challenging problems in novel ways, are very useful in engineering idea generation and solution retrieval. This process is called biologically inspired design. Engineers often use biologically inspired design to solve problems while increasing creativity and expanding the solution space. Using this method, engineers are able to learn from nature and apply biological principles to real world engineering problems to make effective designs and produce innovative solutions. It is important to have a clearer understanding of how the use of the representations and characteristics of examples as external stimuli affect the idea generation process in engineering design. Understanding these processes will be invaluable in offering guidelines for how engineering design should be done and what types of external stimuli should be used to allow for innovation and creativity to be enhanced. This dissertation presents four studies that focus on understanding ways that examples can be used to improve the idea generation process. Three of these studies focus on how the representation of externally imposed examples, which may be used as analogues, influences creativity during idea generation while also minimizing design fixation, which occurs when designers adhere to the features of their own initial design solutions or to features of existing examples. The fourth study focuses on the use of examples as sources for analogical mapping and how these examples produce innovative solutions during idea generation. The first study compares CAD, sketch, and photograph representation presented individually. The second study compares CAD and sketch representation presented together, and the third study examines function tree and sketch representations. The fourth study looks at the real-world context and impact of examples used as sources for analogical mapping to inspire innovative solutions. The results of the studies show that CAD representations of good examples are effective in allowing engineers to identify the key working principles of a design and help to develop higher quality design concepts. CAD representations also cause more fixation to the example’s features. Function trees do not cause nor break fixation compared to a control condition, but do reduce fixation compared with sketches. Biological examples can be successfully used as analogues during engineering idea generation to create novel and effective design solutions to relevant and real-world engineering problems.

Biological research over the past several decades has elucidated some of the mechanisms behind highly mobile, efficient, and robust locomotion in insects such as the cockroach. Roboticists have used this information to create biologically-inspired machines capable of running, jumping, and climbing robustly over a variety of terrains. To date, little work has been done to develop an at-scale insect-inspired robot capable of similar feats, due to limitations in fabrication, actuation, and electronics integration at small scales. This thesis addresses these challenges, focusing on the mechanical design and fabrication of a sub-2g walking robot, the Harvard Ambulatory MicroRobot (HAMR). The development of HAMR includes modeling and parameter selection for a two degree of freedom leg powertrain that enables locomotion. In addition, a design inspired by pop-up books that enables fast and repeatable assembly of the miniature walking robot is presented. Finally, a method to drive HAMR resulting in speeds up to 37cm/s is presented, along with simple control schemes. / Engineering and Applied Sciences