A Large Area Tactile Sensor Patch Based on Commercial Force Sensors

This paper reports the design of a tactile sensor patch to cover large areas of robots and machines that interact with human beings. Many devices have been proposed to meet such a demand. These realizations are mostly custom-built or developed in the lab. The sensor of this paper is implemented with commercial force sensors. This has the benefit of a more foreseeable response of the sensor if its behavior is understood as the aggregation of readings from all the individual force sensors in the array. A few reported large area tactile sensors are also based on commercial sensors. However, the one in this paper is the first of this kind based on the use of polymeric commercial force sensing resistors (FSR) as unit elements of the array or tactels, which results in a robust sensor. The paper discusses design issues related to some necessary modifications of the force sensor, its assembly in an array, and the signal conditioning. The patch has 16 × 9 force sensors mounted on a flexible printed circuit board with a spatial resolution of 18.5 mm. The force range of a tactel is 6 N and its sensitivity is 0.6 V/N. The array is read at a rate of 78 frames per second. Finally, two simple application examples are also carried out with the sensor mounted on the forearm of a rescue robot that communicates with the sensor through a CAN bus

A Survey of Tactile Human-Robot Interactions

Robots come into physical contact with humans in both experimental and operational settings. Many potential factors motivate the detection of human contact, ranging from safe robot operation around humans, to robot behaviors that depend on human guidance. This article presents a review of current research within the field of Tactile Human–Robot Interactions (Tactile HRI), where physical contact from a human is detected by a robot during the execution or development of robot behaviors. Approaches are presented from two viewpoints: the types of physical interactions that occur between the human and robot, and the types of sensors used to detect these interactions. We contribute a structure for the categorization of Tactile HRI research within each viewpoint. Tactile sensing techniques are grouped into three categories, according to what covers the sensors: (i) a hard shell, (ii) a flexible substrate or (iii) no covering. Three categories of physical HRI likewise are identified, consisting of contact that (i) interferes with robot behavior execution, (ii) contributes to behavior execution and (iii) contributes to behavior development. We populate each category with the current literature, and furthermore identify the state-of-the-art within categories and promising areas for future research

Soft pneumatic devices for blood circulation improvement

The research activity I am presenting in this thesis lies within the framework of a cooperation between the University of Cagliari (Applied Mechanics and Robotics lab, headed by professor Andrea Manuello Bertetto, and the research group of physicians referencing to professor Alberto Concu at the Laboratory of Sports Physiology, Department of Medical Sciences), and the Polytechnic of Turin (professor Carlo Ferraresi and his equipe at the Group of Automation and Robotics, Department of Mechanical and Aerospace Engineering) This research was also funded by the Italian Ministry of Research (MIUR – PRIN 2009). My activity has been mainly carried on at the Department of Mechanics, Robotics lab under the supervision of prof. Manuello; I have also spent one year at the Control Lab of the School of Electrical Engineering at Aalto University (Helsinki, Finland). The tests on the patients were taken at the Laboratory of Sports Physiology, Cagliari. I will be describing the design, development and testing of some soft pneumatic flexible devices meant to apply an intermittent massage and to restore blood circulation in lower limbs in order to improve cardiac output and wellness in general. The choice of the actuators, as well as the pneumatic circuits and air distribution system and PLC control patterns will be outlined. The trial run of the devices have been field--‐tested as soon a prototype was ready, so as to tune its features step--‐by--‐ step. I am also giving a characterization of a commercial thin force sensor after briefly reviewing some other type of thin pressure transducer. It has been used to gauge the contact pressure between the actuator and the subject’s skin in order to correlate the level of discomfort to the supply pressure, and to feed this value back to regulate the supply air flow. In order for the massage to be still effective without causing pain or distress or any cutoff to the blood flow, some control objective have been set, consisting in the regulation of the contact force so that it comes to the constant set point smoothly and its value holds constant until unloading occurs. The targets of such mechatronic devices range from paraplegic patients lacking of muscle tone because of their spinal cord damage, to elite endurance athletes needing a circulation booster when resting from practicing after serious injuries leading to bed rest. Encouraging results have been attained for both these two categories, based on the monitored hemodynamic variables

Dynamically reconfigurable Artificial Sensate Skin

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2006.Includes bibliographical references (p. 207-211).The idea of an Artificial Sensate Skin device that mimics the characteristics and functions of its analogous living tissue whether human or animal is not new. Yet, most of the current related work has been focused in the development of either materials, flexible electronics or ultra-dense sensing matrices and Wide Area Sensor Networks. The current work describes the design and implementation of a new type of Artificial Sensate Skin. This Artificial Sensate Skin is implemented as a low-power, highly scalable and mechanically flexible Wired Sensor Network. This Skin is composed of one or many Skin Patches which in turn are composed of one or many Skin Nodes. Each node is able to measure Strain, Pressure, Ambient Light, Pressure, Sound and Mechanoreception. Each Skin Patch can either work as a stand-alone device or as a data extraction device if this is attached to a Personal Computer through a different type of device referred to as Brains. Each Skin Node and therefore each Skin Patch :is Dynamically Adaptable meaning that they can adapt to external stimuli by either modifying their behavior or by completely changing their code.(cont.) Construction of a sensate skin in such a modular fashion promises intrinsic scalability, where peer-to-peer connections between neighbors can reduce local data, which can then be sent to the brain by the high-speed common backbone. The current project also involves the design and implementation of the software components needed; these include a PC Graphical User Interface, application software and the firmware required by the embedded microcontrollers. Results show that needed resources like bandwidth are greatly minimized because of the addition of embedded processing power. Results also indicate that the platform can be used as a scalable smart material to cover interactive surfaces, or simply to extract a rich set of dense multi-modal sensor data.by Gerardo Barroeta Pérez.S.M

Sensitive Skin for Robotics

This thesis explores two novel ways of reducing the data complexity of tactile sensing. The thesis begins by examining the state-of-the art in tactile sensing, not only examining the sensor construction and interpretation of data but also the motivation for these designs. The thesis then proposes two methods for reducing the complexity of data in tactile sensing. The first is a low-power tactile sensing array exploiting a novel application of a pressure-sensitive material called quantum tunnelling composite. The properties of this material in this array form are shown to be beneficial in robotics. The electrical characteristics of the material are also explored. A bit-based structure for representing tactile data called Bitworld is then defined and its computational performance is characterised. It is shown that this bit-based structure outperforms floating-point arrays by orders of magnitude. This structure is then shown to allow high-resolution images to be produced by combining low resolution sensor arrays with equivalent functional performance to a floating-point array, but with the advantages of computational efficiency. Finally, an investigation into making Bitworld robust in the presence of positional noise is described with simulations to verify that such robustness can be achieved. Overall, the sensor and data structure described in this thesis allow simple, but effective tactile systems to be deployed in robotics without requiring a significant commitment of computational or power resources on the part of a robot designer.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Propuesta y Evaluación de Algoritmos para la Corrección de Errores en Sensores Táctiles

Los sensores táctiles suelen ser matrices de unidades detectoras denominadas tácteles, utilizados habitualmente en robótica para proporcionar capacidades de percepción en aplicaciones que requieren de contacto físico con objetos. Así, es posible determinar su forma, tamaño, textura o dureza permitiendo a los robots interactuar de forma autónoma y con seguridad en un entorno que puede mostrar condiciones cambiantes. Sin embargo, la necesidad de cubrir grandes áreas de contacto de manera flexible y con bajo coste, lleva a utilizar sensores que presentan errores de histéresis, no linealidad, deriva o dispersión. Esto provoca una escasa presencia efectiva de estos sensores en las plataformas robóticas existentes en la actualidad. En esta tesis, en primer lugar, se estudia el efecto de estos errores sobre la información de control derivada de las imágenes táctiles obtenidas como respuesta de un sensor al contacto con un objeto, y que se utiliza en tareas de manipulación robótica. Se realiza el estudio sobre dos sensores táctiles piezo-resistivos, uno flexible de bajo coste y propenso a errores, y otro comercial con menores limitaciones. En segundo lugar, a nivel de táctel, se exploran y proponen algoritmos de corrección de las no linealidades de histéresis complejas mostradas por el sensor de bajo coste, que permitan obtener medidas precisas y fiables de la presión ejercida sobre su superficie. Se analizan tres métodos utilizados por otro tipo de sensores y actuadores: el modelo generalizado de Prandtl-Ishlinskii, un modelo modificado del método clásico de Prandtl-Ishlinskii y un modelo basado en polinomios que aproximan las curvas externas de los bucles de histéresis. Además, como aportación principal de esta tesis, se propone un nuevo algoritmo de modelado denominado ELAM. Este método se basa en la determinación por algoritmos de aproximación de unos puntos intermedios en las curvas y la aplicación de distintas estrategias de mapeo lineal de las curvas externas a las internas del bucle de histéresis medido experimentalmente. El análisis de las medidas y pruebas realizadas, muestra que los errores a nivel de matriz tienen una influencia sobre los parámetros de control similar a otras fuentes admitidas como la dispersión y la resolución limitada. La información extraída del contacto del objeto con un sensor de bajo coste es suficientemente buena en términos de distribución espacial y orientación como para ser utilizada en aplicaciones robóticas, pero no lo es sobre la fuerza de contacto, por lo que en aplicaciones que necesiten una alta precisión en la medida de la presión ejercida, será necesario compensar los errores del sensor. En este sentido, se demuestra que el método ELAM propuesto en esta tesis, consigue un modelo con un ajuste mucho más preciso a los datos experimentales que los otros métodos evaluados. Además, se trata de un método flexible, simple de implementar en dispositivos como FPGAs para aplicaciones en tiempo real, con pocos parámetros de control, apropiado para ciclos de histéresis complejos de otros tipos de sensores o actuadores y que permite corregir los errores de histéresis, no linealidad y dispersión en la respuesta de los sensores táctiles