Dissertations / Theses on the topic 'Tactile sensory development'

The fact that sensory modalities do not become functional at the same time raises the question of how sensory systems and their particular experiential histories might influence one another. Few studies have addressed how modified stimulation to earlier-emerging modalities might influence the functioning of relatively later-developing modalities. Previous findings have shown that enhanced prenatal tactile and vestibular (proximal) stimulation extended and delayed normal patterns of auditory and visual responsiveness to species-typical maternal cues in bobwhite quail respectively. Although these results were attributed to the increased amount of sensory stimulation, these results may be a function of when prenatal augmented proximal exposure took place. To address this issue the present study exposed groups of bobwhite quail embryos to equivalent amounts of augmented tactile and vestibular stimulation either at a time when a later-emerging modality (auditory or visual) was beginning to functionally emerge or when it had already functionally emerged. Results indicate that differences in the timing of augmented tactile and vestibular stimulation led to differences in subsequent auditory and visual responsiveness. Embryos were unable to learn a maternal call prior to hatching when enhanced proximal stimulation coincided with auditory functional emergence implicating a deficit in auditory functioning, but did learn a maternal call when enhanced proximal stimulation occurred after auditory functional emergence. Augmented proximal stimulation that coincided with visual functional emergence did not appear to influence normal visual responsiveness, but when proximal stimulation occurred after visual emergence, chicks displayed an accelerated approach response to species-typical visual cues. These findings support the view that the timing of enhanced stimulation to earlier-emerging modalities is important, and have meaningful implications for intersensory theory and research.<br>Ph. D.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 82-86).<br>MEMS (Microelectromechanical System) pressure sensor arrays are gaining attention in the field of underwater navigation because they are seen as alternatives to current sonar and vision-based systems that fail to navigate unmanned undersea vehicles (UUVs) in dark, unsteady and cluttered environments. Other advantages of MEMS pressure sensor arrays include lower power consumption and that their passive nature makes them covert. The goal of this work focuses on the development of a flexible pressure sensor array for UUVs, where the sensor array is inspired by the ability of fish to form three-dimensional maps of their surroundings. Fish are able to decipher various pressure waves from their surroundings using the array of pressure sensors in their lateral line sensory organs that can detect minute pressure differences. Similarly, by measuring pressure variations using an engineered pressure-sensor array on the surface of an UUV, this project hopes to aid UUVs in the identification and location of obstacles for navigation. The active material of the pressure sensor array is a porous polydimethylsiloxane (PDMS)-carbon black composite made out of a sugar sacrificial scaffold that shows great promise for satisfying the proposed applications. The proposed device structure is flexible, easily fabricated, cost efficient and can be implemented on a large-area and curved UUV surface. Although hysteresis occurs during the electromechanical test, the piezoresistivity of this porous PDMS-carbon black composite is reversible and reproducible. Compared to its non-porous counterpart, this porous composite shows a six-times increase in piezoresistivity and a greatly reduced Young's Modulus. When tested underwater, this porous composite was able to differentiate water waves that had a frequency of 1 Hz and 2 Hz, which is promising for its underwater application. This porous composite was also extended to the application of tactile sensors using a different device architecture, which showed excellent response under mechanical testing.<br>by Mun Ee Woo.<br>S.M.

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.

Glaucoma is a group of diseases that lead to a progressive loss of vision in the majority of the cases due to elevated intraocular pressure (IOP). Glaucoma is the second leading cause of blindness after cataract. According to the National Eye Institute's report, there were almost 2.7 million detected cases in the United States in 2010.Everybody older than 40, African Americans and Hispanics at any age, are at high risk and would need frequent IOP measurement in order to diagnose the disease at an early stage. Majority of the existing tonometers measure the IOP through the cornea and their operation requires clinical professionals. As a result, the measurement has to take place at the doctor's office and requires local anesthesia. This work demonstrates a novel multi-probe tactile-tonometer, which is operated by the patients and measures the IOP through their eyelid. Finite element (FE) models were used to estimate the static, mechanical response of the eye, due to indentation at different IOPs. The models include hyperelastic behavior of the sclera and cornea. The thickness variation of the sclera, throughout the geometry was also considered. Volumetric constraint was applied on the eye cavity, but its actual anatomic structure was neglected. In-vitro indentation tests were performed on enucleated porcine eyeballs, as a proof of concept of tactile-tonometry. Eye/patient specific calibration method was demonstrated, in order to further improve accuracy ("Forward Biomechanics"), and in-vivo estimation of biomechanical properties of the eye ("Inverse Biomechanics"). The method uses simplified FE models and a feed forward artificial neural network (ANN). The tactile-tonometer was implemented for human use, and clinical studies were performed on a small number (10) of human subjects. Based on the measurements from the recruited 10 patients (3 females, 7 males) with a mean age ±SD of 43±19.33 and the measured IOP range of 9.25-21.25mmHg, the novel technique has a mean of differences of ≈ 0mmHg and its 95% limits of agreement are ±4.84mmHg with respect to the Goldmann Applanation Tonometer.

In this thesis, the design, fabrication and characterisation of a bio-inspired microelectromechanical systems (MEMS) based tactile sensor array is presented. A vast amount of research has been carried out in the area of tactile sensing and various transduction methods have been explored. However, currently no device exists with a performance comparable to that of the biological tactile sensors of the human fingertip in terms of robustness, sensitivity, spatial resolution and dynamic performance. The sensors developed in this work employ the principles of electrical capacitance and are fabricated from commercially available siliconon- oxide wafers using simple process steps. Each sensor is formed from two plates of highly conductive silicon separated by an air-gap formed from sacrificial etching of the oxide layer. Deflection of the 2 \(\mu\)m thick upper plate of the sensor as a result of applied mechanical stimulus, causes a change in capacitance which is the output of the sensor. Within the array, the individual sensors are spaced 150 \(\mu\)m apart (centre-centre pitch of 570 \(\mu\)m) and therefore offer the potential for high spatial resolution. To protect the sensor array from mechanical shock and provide skin like compliance, the use of suitable packaging materials was explored. The use of poly dimethyl siloxane (PDMS) as a suitable skin-like material was demonstrated. Modification of the surface topography of the packaging layer to include ’fingerprint’ like features was explored and its benefits highlighted. Sensor characterisation experiments revealed that the sensing device was sufficiently sensitive to allow the discrimination of different textures (with feature spacing down to 0.2 mm) through tests conducted using gratings varying in spatial periodicity and fabrics. Based on the results, the sensors can be used as an analogue of the slowly adapting tactile receptors (Merkel disks) for robotic finger applications.

"This thesis presents an extension of sensitive manipulation which transforms tactile sensors away from end effectors and closer to whole body sensory feedback. Sensitive manipulation is a robotics concept which more closely replicates nature by employing tactile sensing to interact with the world. While traditional robotic arms are specifically designed to avoid contact, biological systems actually embrace and intentionally contact the environment. This arm is inspired by these biological systems and therefore has compliant joints and a tactile shell surrounding the two primary links of the arm. The manipulator has also been designed to be capable of both industrial and humanoid style manipulation. There are an untold number of applications for an arm with increased tactile feedback primarily in dynamic environments such as in industrial, humanoid, and prosthetic applications. The arm developed for this thesis is intended to be a desktop research platform, however, one of the most influential applications for increased tactile feedback is in prosthetics which are operate in ever changing and contact ridden environments while continuously interacting with humans. This thesis details the simulation, design, analysis, and evaluation of a the first four degrees of freedom of a robotic arm with particular attention given to the design of modular series elastic actuators in each joint as well as the incorporation of a shell of tactile sensors. "

碩士<br>南台科技大學<br>電子工程系<br>96<br>There existed handful of commercially available tactile sensors. However, most of the sensors are large, cumbersome and provide mainly pressure sensing. The purpose of this study is to design a polymeric sensor capable of measuring both directions and magnitudes of the applied force. Potential applications are in medical, dental, sports, robotic, civil and infrastructure etc. The basic concept of measuring pressure and shear forces is to utilize a polymeric capacitor array. A design of a sandwich structure consists of an array of capacitors where capacitors are made of two flexible metal electrodes supported by two thin elastomer substrates and separated by a thin silicone gel. A force induction on the capacitors causes the capacitors’ gap space and area coverage to change. Both pressure and shear can then be derived based on the changes in the capacitors by using a simple summation and differentiation of these capacitors. A simple readout circuit is constructed to detect changes in the capacitance in the array based on the output signal, to provide the force information. Using a data acquisition system and National Instrument LabVIEW program, the signals are analyzed and magnitude and directions of the forces are displayed in real time.

碩士<br>國立臺灣大學<br>機械工程學研究所<br>92<br>In this thesis, we develop a tactile sensor system with high performance. The tactile sensor is integrated into the fingertip of prosthetic hand (NTU-Hand IV) to monitor the force distribution. To enhance the grasping ability, we apply the Tension Spline Algorithm to trajectory generation of NTU-Hand IV’s fingertip. Also, the force control of grasping is implemented with the tactile sensor system. In the development of the tactile sensor system, we use polymer layer to combine the high sensitive pressure-conductive rubber with thin-flexible printed-circuit board. Meanwhile, the hardware-firmware system and the graphical user interface are developed to monitor resistive-array sensor and handle the force distribution. In trajectory generation, the Tension Spline Algorithm is integrated into multi-trajectory generation by adjusting of tension factor, and the position-force controller is used to implement the grasping planning for NTU-Hand IV. Besides, that Tension Spline Algorithm applied to the image processing domain is also proposed to gain better force distribution monitor.

In this study, analytical and Finite Element Method (FEM) are employed to determine the contact pressure on the surface of a tissue being grasped by an endoscopic grasper, in Minimally Invasive Surgery (MIS). Normally, an endoscopic grasper has corrugated teeth in order to maintain a firm grip on slippery tissues. Because it is very important to avoid damage while grasping and manipulating tissue during endoscopic surgery, it is essential to determine the exact contact pressure on the surface of the tissue. To this end, a comprehensive closed form analysis is undertaken followed by the finite element and experimental analyses of the grasping contact pressure on viscoelastic materials which have similar properties as that of biological tissues. The behavior of a grasper with wedge and semi-cylindrical teeth is examined when pressed into a linear viscoelastic material. Initially, a single tooth penetrating into a solid is studied and then is extended to the multi teeth grasper. The elastic wedge and semi-cylinder penetration is the basis of the closed form analysis. Also the effects of time are included in the equations by considering the corresponding integral operator from viscoelastic stress-stain relations. In addition, a finite element analysis is carried out. Finally, the experimental results will be presented to validate both analytical and FEM analysis. The results of this study provide a closed form expression for grasping contact pressure, force and contact area along with the variations of stress in tissue obtained through FEM analysis. The variation of contact pressure and the rate of growth of the contact area with time are also presented. In order to determine the properties of the biological tissues during MIS, we present the design, analysis, fabrication and assembly of four-tooth annular micro-fabricated tactile sensors incorporated to the upper and lower jaws of an endoscopic surgical grasper tool. Two viscoelastic models, namely, Kelvin-Voight and Kelvin are employed for tissue characterization. The relationship between the force ratio, compliance and the equivalent viscous damping of the tissue are studied. The designed sensor uses a Polyvinylidene Fluoride (PVDF) film as its sensing element. The sensor consists of arrays of rigid and compliant elements which are mounted on the tip of an endoscopic surgical grasper tool. The relative force between adjacent parts of the contact object is used to measure the viscoelastic properties.

Development of Piezoresistive Tactile Sensors and a Graphical Display System for Minimally Invasive Surgery and Robotics Masoud Kalantari, PhD Concordia University, 2013 This PhD work presents a new tactile and feedback systems for minimally invasive surgery (MIS)and robotics. The thesis is divided into two major sections: the tactile sensing system, and the graphical display system. In the tactile sensing system, piezoresistive materials are used as measuring elements. The first part of the thesis is focused on the theoretical modeling of piezoresistive sensing elements, which are semiconductive polymer composites. The model predicts the piezoresistive behavior in semiconductive polymer composites, including their creep effect and contact resistance. A single force sensing resistor (FSR) is, then, developed by using the semiconductive polymer composite materials. The developed FSR is used in the structure of a novel tactile sensor as the transduction element. The developed tactile sensor is designed to measure the difference in the hardness degree of soft tissues. This capability of the sensor helps surgeons to distinguish different types of tissues involved in the surgery. The tactile sensor is integrated on the extremity of a surgical tool to provide tactile feedback from the interaction between surgical instruments and the tissue during MIS. Mitral valve annuloplasty repair by MIS is of our particular interest to be considered as a potential target for the use of the developed tactile sensor. In the next step, the contact interaction of the tactile sensor with soft tissues is modelled, parametrically. Viscoelastic interaction is considered between the tactile sensor and atrial tissue in annuloplasty mitral valve repair; and a parametric solution for the viscoelastic contact is achieved. In addition to the developed sensor, a novel idea regarding measuring the indentation rate, in addition to measuring force and displacement is implemented in a new design of an array tactile sensor. It is shown that the indentation-rate measurement is an important factor in distinguishing the hardness degree of tissues with viscoelastic behaviour. The second part of the thesis is focused on the development of a three-dimensional graphical display that provides visual palpation display to any surgeon performing robotic assisted MIS. Two matrices of the developed piezoresistive force sensor are used to palpate the tissue and collect the tactile information. The collected data are processed with a new algorithm and graphically rendered in three dimensions. Consequently, the surgeon can determine the presence, location, and the size of any hidden superficial tumor/artery by grasping the target tissue in a quasi-dynamic way.

abstract: Human fingertips contain thousands of specialized mechanoreceptors that enable effortless physical interactions with the environment. Haptic perception capabilities enable grasp and manipulation in the absence of visual feedback, as when reaching into one's pocket or wrapping a belt around oneself. Unfortunately, state-of-the-art artificial tactile sensors and processing algorithms are no match for their biological counterparts. Tactile sensors must not only meet stringent practical specifications for everyday use, but their signals must be processed and interpreted within hundreds of milliseconds. Control of artificial manipulators, ranging from prosthetic hands to bomb defusal robots, requires a constant reliance on visual feedback that is not entirely practical. To address this, we conducted three studies aimed at advancing artificial haptic intelligence. First, we developed a novel, robust, microfluidic tactile sensor skin capable of measuring normal forces on flat or curved surfaces, such as a fingertip. The sensor consists of microchannels in an elastomer filled with a liquid metal alloy. The fluid serves as both electrical interconnects and tunable capacitive sensing units, and enables functionality despite substantial deformation. The second study investigated the use of a commercially-available, multimodal tactile sensor (BioTac sensor, SynTouch) to characterize edge orientation with respect to a body fixed reference frame, such as a fingertip. Trained on data from a robot testbed, a support vector regression model was developed to relate haptic exploration actions to perception of edge orientation. The model performed comparably to humans for estimating edge orientation. Finally, the robot testbed was used to perceive small, finger-sized geometric features. The efficiency and accuracy of different haptic exploratory procedures and supervised learning models were assessed for estimating feature properties such as type (bump, pit), order of curvature (flat, conical, spherical), and size. This study highlights the importance of tactile sensing in situations where other modalities fail, such as when the finger itself blocks line of sight. Insights from this work could be used to advance tactile sensor technology and haptic intelligence for artificial manipulators that improve quality of life, such as prosthetic hands and wheelchair-mounted robotic hands.<br>Dissertation/Thesis<br>Ph.D. Mechanical Engineering 2013