Providing robots with distributed, robust and accurate tactile feedback is a fundamental problem in robotics because of the large number of tasks that require physical interaction with objects. Tactile sensors can provide robots with information about the location of each point of contact with the manipulated object, an estimation of the contact forces applied (normal and shear) and even slip detection. Despite significant advances in touch and force transduction, tactile sensing is still far from ubiquitous in robotic manipulation. Existing methods for building touch sensors have proven difficult to integrate into robot fingers due to multiple challenges, including difficulty in covering multicurved surfaces, high wire count, or packaging constrains preventing their use in dexterous hands. In this dissertation, we focus on the development of soft tactile systems that can be deployed over complex, three-dimensional surfaces with a low wire count and using easily accessible manufacturing methods. To this effect, we present a general methodology called spatially overlapping signals. The key idea behind our method is to embed multiple sensing terminals in a volume of soft material which can be deployed over arbitrary, non-developable surfaces. Unlike a traditional taxel, these sensing terminals are not capable of measuring strain on their own. Instead, we take measurements across pairs of sensing terminals. Applying strain in the receptive field of this terminal pair should measurably affect the signal associated with it. As we embed multiple sensing terminals in this soft material, a significant overlap of these receptive fields occurs across the whole active sensing area, providing us with a very rich dataset characterizing the contact event. The use of an all-pairs approach, where all possible combinations of sensing terminals pairs are used, maximizes the number of signals extracted while reducing the total number of wires for the overall sensor, which in turn facilitates its integration. Building an analytical model for how this rich signal set relates to various contacts events can be very challenging. Further, any such model would depend on knowing the exact locations of the terminals in the sensor, thus requiring very precise manufacturing. Instead, we build forward models of our sensors from data. We collect training data using a dataset of controlled indentations of known characteristics, directly learning the mapping between our signals and the variables characterizing a contact event. This approach allows for accessible, cheap manufacturing while enabling extensive coverage of curved surfaces. The concept of spatially overlapping signals can be realized using various transduction methods; we demonstrate sensors using piezoresistance, pressure transducers and optics. With piezoresistivity we measure resistance values across various electrodes embedded in a carbon nanotubes infused elastomer to determine the location of touch. Using commercially available pressure transducers embedded in various configurations inside a soft volume of rubber, we show its possible to localize contacts across a curved surface. Finally, using optics, we measure light transport between LEDs and photodiodes inside a clear elastomer which makes up our sensor. Our optical sensors are able to detect both the location and depth of an indentation very accurately on both planar and multicurved surfaces. Our Distributed Interleaved Signals for Contact via Optics or D.I.S.C.O Finger is the culmination of this methodology: a fully integrated, sensorized robot finger, with a low wire count and designed for easy integration into dexterous manipulators. Our DISCO Finger can generally determine contact location with sub-millimeter accuracy, and contact force to within 10% (and often with 5%) of the true value without the need for analytical models. While our data-driven method requires training data representative of the final operational conditions that the system will encounter, we show our finger can be robust to novel contact scenarios where the shape of the indenter has not been seen during training. Moreover, the forward model that predicts contact locations and applied normal force can be transfered to new fingers with minimal loss of performance, eliminating the need to collect training data for each individual finger. We believe that rich tactile information, in a highly functional form with limited blind spots and a simple integration path into complete systems, like we demonstrate in this dissertation, will prove to be an important enabler for data-driven complex robotic motor skills, such as dexterous manipulation.

Humans in the modern world can survive without the Aristotelian senses of vision, hearing, smell or taste, but no one is completely without the ability to sense touch. This sense is essential for everything from basic tasks like tool manipulation to the complex interactions that underlie social bonding, sexual reproduction and pleasure. Touch receptors are embedded in the skin, at the interface of our bodies and the world. A remarkable array of varied receptor types tile our skin to signal different features of the objects we touch and alert us to their shape and texture. An early investigator of the neurological basis of touch, Maximillian von Frey, proposed in 1895 that the morphological diversity of neural endings in the skin could represent functional specificity. It is indeed the evolution of diverse receptor structures that has endowed the sensory organ of our skin with remarkable somatosensory functions. Here I explore the evolution of mechanosensing, and discuss how diversity in form and organization of touch receptors, from the cellular to organismal level, can shape the function of touch reception.

In comparison with other methods assuming that multi-contacts between tool and object are point or line based contacts, our body-based haptic interaction model involves the intrinsic contacts with different tool/object materials acquired from the real world for the realistic haptic simulation. Our studies in interactive haptic deformations is to marry the merits of traditional deformable modeling techniques in computer graphics with force-enabled deformations guided by real-world physics laws, simulating the realistic tangible sensation of interactive haptic manipulation with user-specified constraints in touch-enabled virtual environments. The multi-resolution rendering framework developed in our system unifies the graphics/haptics rendering processes based on the construction of hierarchical imposter representations of surface and volumetric models, and the optimal haptic-scene performance at run time is employed to meet both the visual and haptic perceptual qualities. The proposed work is extensible to support users perceptually experience the virtual objects with different materials through the tangible interfaces in the augmented virtual worlds. In general, haptic perception and manipulation can be further constructed uniformly in the multi-resolution rendering framework. The future work includes investigating multiple force evaluation methods and haptic contact models and in addition integrating them into the unified haptic-scene framework, for the rich and dexterous experiences in large, touch-enable virtual environments. / The body-based haptic interaction model is proposed and developed for simulating the contacted forces between the haptic tools and interacting object, based on Hertz's theory establishing the intrinsic stress distribution related to real material properties. In comparison with the common force evaluation models, the proposed body-based haptic interaction model involves the intrinsic contacts with different tool/object materials acquired from the real world for the realistic haptics simulation. For adding the haptic sensations with touch-enabled soft objects, the thesis first studies multiple force-reflecting deformable objects in volume sculpting, then soft object deformation of Loop subdivision surfaces, and further the soft object freeform deformation through mass-spring Bezier volume lattice. The constrained haptic deformations based on the metaballs are experimented to effectively control the interactive force distribution within the influence range, making the deformable simulation of objects easy to control and manipulate. Lastly, the unified multi-resolution rendering framework of touch-enabled virtual environments is proposed and developed, with level-of-detail imposter representations of both graphics and haptics perceptions. The hierarchical graphics/haptics imposter descriptions of hybrid models (e.g. surfaces/volumes) within the virtual environment are constructed in advance, to maximize the optimal performance of the rendering processes during the interactive haptic-scene navigation and explorations. / This thesis dissertation is mainly devoted to investigate the realistic haptics techniques in touch-enabled virtual environments. It has three major parts: the body-based haptic interaction model to simulate the realistic, physical tool-object interactions based on Hertz's contact theory and applications; the realization of interactive haptic manipulation of deformable objects with volume/surface representations, and further development of constrained haptic deformations based on the metaballs; the integration of multi-resolution rendering framework with level-of-detail impostor representations of graphics and haptics objects, to support the optimal rendering performance during the interactive navigation of touch-enabled virtual environments. / Virtual Reality (VR) applications strive to simulate real or imaginary scenes with which users can interact and perceive the effects of their actions in real time. Adding haptic information such as vibration, tactile array, force feedback simulation enhances the sense of presence in virtual environments. Realistic haptic modeling & rendering is the core component in feeling and manipulating virtual objects within the virtual environments. Haptics interfaces present new challenges in data processing analysis, physical modeling, interactive visualization and tangible simulations, especially in the situation where it is crucial for the operators to touch, grasp and manipulate rigid/soft objects in the virtual worlds. / Chen Hui. / "April 2006." / Adviser: Hanqiu Sun. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6498. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 177-185). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Fung Wai Keung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 146-151). / Acknowledgements --- p.viii / Abstract --- p.1 / Chapter 1 --- Overview --- p.3 / Chapter 1.1 --- Tactile Sensing in Human and Robot --- p.4 / Chapter 1.1.1 --- Human Hands and Robotic Hands --- p.4 / Chapter 1.1.2 --- Mechanoreceptors in skin and Tactile Sensor Arrays --- p.7 / Chapter 1.2 --- Motivation --- p.12 / Chapter 1.3 --- Objectives --- p.13 / Chapter 1.4 --- Related Work --- p.14 / Chapter 1.4.1 --- Using Vision Alone --- p.15 / Chapter 1.4.2 --- Integration of Vision and Touch --- p.15 / Chapter 1.4.3 --- Using Touch Sensing Alone --- p.17 / Chapter 1.4.3.1 --- Ronald S. Fearing's Work --- p.18 / Chapter 1.4.3.2 --- Peter K. Allen's Work --- p.22 / Chapter 1.5 --- Outline --- p.26 / Chapter 2 --- Geometric Models --- p.27 / Chapter 2.1 --- Introduction --- p.27 / Chapter 2.2 --- Superquadrics --- p.27 / Chapter 2.2.1 --- 2D Superquadrics --- p.27 / Chapter 2.2.2 --- 3D Superquadrics --- p.29 / Chapter 2.3 --- Model Recovery of Superquadric Models --- p.31 / Chapter 2.3.1 --- Problem Formulation --- p.31 / Chapter 2.3.2 --- Least Squares Optimization --- p.33 / Chapter 2.4 --- Free-Form Deformations --- p.34 / Chapter 2.4.1 --- Bernstein Basis --- p.36 / Chapter 2.4.2 --- B-Spline Basis --- p.38 / Chapter 2.5 --- Other Geometric Models --- p.41 / Chapter 2.5.1 --- Generalized Cylinders --- p.41 / Chapter 2.5.2 --- Hyperquadrics --- p.42 / Chapter 2.5.3 --- Polyhedral Models --- p.44 / Chapter 2.5.4 --- Function Representation --- p.45 / Chapter 3 --- Sensing Strategy --- p.54 / Chapter 3.1 --- Introduction --- p.54 / Chapter 3.2 --- Sensing Algorithm --- p.55 / Chapter 3.2.1 --- Assumption of objects --- p.55 / Chapter 3.2.2 --- Haptic Exploration Procedures --- p.56 / Chapter 3.3 --- Contour Tracing --- p.58 / Chapter 3.4 --- Tactile Sensor Data Preprocessing --- p.59 / Chapter 3.4.1 --- Data Transformation and Sensor Calibration --- p.60 / Chapter 3.4.2 --- Noise Filtering --- p.61 / Chapter 3.5 --- Curvature Determination --- p.64 / Chapter 3.6 --- Step Size Determination --- p.73 / Chapter 4 --- 3D Shape Reconstruction --- p.80 / Chapter 4.1 --- Introduction --- p.80 / Chapter 4.2 --- Correspondence Problem --- p.81 / Chapter 4.2.1 --- Affine Invariance Property of B-splines --- p.84 / Chapter 4.2.2 --- Point Inversion Problem --- p.87 / Chapter 4.3 --- Parameter Triple Interpolation --- p.91 / Chapter 4.4 --- 3D Object Shape Reconstruction --- p.94 / Chapter 4.4.1 --- Heuristic Approach --- p.94 / Chapter 4.4.2 --- Closed Contour Recovery --- p.97 / Chapter 4.4.3 --- Control Lattice Recovery --- p.102 / Chapter 5 --- Implementation --- p.105 / Chapter 5.1 --- Introduction --- p.105 / Chapter 5.2 --- Implementation Tool - MATLAB --- p.105 / Chapter 5.2.1 --- Optimization Toolbox --- p.107 / Chapter 5.2.2 --- Splines Toolbox --- p.108 / Chapter 5.3 --- Geometric Model Implementation --- p.109 / Chapter 5.3.1 --- FFD Examples --- p.111 / Chapter 5.4 --- Shape Reconstruction Implementation --- p.112 / Chapter 5.5 --- 3D Model Reconstruction Examples --- p.120 / Chapter 5.5.1 --- Example 1 --- p.120 / Chapter 5.5.2 --- Example 2 --- p.121 / Chapter 6 --- Conclusion --- p.128 / Chapter 6.1 --- Future Work --- p.129 / Appendix --- p.133 / Bibliography --- p.146

Thesis (M.S.)--Florida State University, 2004. / Advisor: Dr. Carl A. Moore, Florida State University, College of Engineering, Dept. of Mechanical Engineering. Title and description from dissertation home page (viewed 6/21/04). Includes bibliographical references.

Thesis (M.E.)--University of Canterbury, 2009. / Typescript (photocopy). "June 2009." Includes bibliographical references (leaves 94-98). Also available via the World Wide Web.

Thesis (Ph.D)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2010. / Committee Chair: Tsukruk, Vladimir; Committee Member: Shofner, Meisha; Committee Member: Srinivasarao, Mohan; Committee Member: Thio, Yonathan; Committee Member: Weissburg, Marc. Part of the SMARTech Electronic Thesis and Dissertation Collection.

This PhD thesis describes the design and development of a new resonator based tactile sensitive probe. This new sensor was proposed because of the increasing need for high-sensitivity, high-speed touch-sensitive probes in coordinate metrology due to the ever-growing demand for precision and reliability at sub-micron level accuracy. Extensive background research on the current development of touch trigger probes has shown that designs based on the resonator principle have potential for minimising lobing effects and the false triggering associated with most commercially available probes. Resonant based sensors have been investigated over many decades and used very successfully in a wide range of applications. However their commercial exploitation in the field of precision engineering has not been particularly successful. One reason for such slow progress is the complexity of the interaction between oscillatory probes and typical engineering surfaces in less than ideal environments. The main aim of this research was to design a high precision resonator based tactile sensitive probe and to investigate the causes of parametric changes on resonant touch sensors both before and during contact with a variety of engineering surfaces in order to achieve a better understanding of contact mechanisms. The four main objectives were: preliminary design and characterisation of a resonator based touch sensor; development of the mathematical model which predicts parametric changes on a resonant probe considering both near surface effects and mechanical contact; experimental verification of mathematical predictions; and an investigation into possible commercial exploitation of the new probe in precision applications. A novel resonator based tactile sensor that utilises the piezoelectric effect was designed and characterised. The design exploits the fact that when a stiff element (probe) oscillating near or at its resonance frequency comes into contact with the surface of another body (workpiece), the frequency of vibrational resonance of the probe changes depending on the properties of the workpiece. The phase-locked loop frequency detection technique was employed to track changes in frequency as well as in the phase of the resonant system. The initial characterisation of the touch sensor has shown a sensitivity to contact of less then 4 mN, a high triggering rate and good repeatability. The potential for application in measuring material properties was also demonstrated. As a result of the characterisation a comprehensive mathematical model was developed. This novel model was based on Hertzian contact mechanics, Rayleigh's approximate energy method and work carried out by Smith and Chetwynd on the analysis of elastic contact of a sphere on a flat. The model predicts that phase and frequency shift of a resonator based sensor can either increase or decrease depending on the dominant phenomena (added mass, stiffness and damping) in the contact region. Observation of dynamic characteristics at either side of the resonant frequency can be used to identify the predominant effect. In order to confirm the model experimentally, another prototype probe was developed. The new sensor was engaged in observations of contact mechanisms with engineering surfaces. The experimental results have showed favourable agreement with the developed mathematical model. This enabled a better understanding of contact phenomena uncovering possibilities for the application of resonant sensors in many other areas. The research has shown that the new probe has potential in contact measurements where it can be used for the quantitative assessment of the physical properties of different materials (modulus of elasticity, density and energy dissipation) and also in non-destructive hardness testing. It was shown that the device can be successfully used in coordinate metrology as a touch trigger probe and as a 3D vector probe. Finally, applications can also be found in surface topography as a surface characterisation instrument. It is intended that the research described in this thesis will make an important contribution in the area of resonator based probes, providing a better understanding of the causes of parametric changes on the oscillatory sensor during contact with the object being measured. Consequently, this will enable a more effective exploitation of resonant probes for a broad range of precision applications.

Thesis (M.S.)--Ohio University, June, 1999. / Title from PDF t.p.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 325-341). Available also in a digital version from Dissertation Abstracts.