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Atactile sensor is a device that measures information arising from physical interaction with its environment. Tactile sensors are generally modeled after the biological sense ofcutaneous touch which is capable of detecting stimuli resulting from mechanical stimulation, temperature, and pain (although pain sensing is not common in artificial tactile sensors). Tactilesensors are used inrobotics,computer hardware andsecurity systems. A common application of tactile sensors is intouchscreen devices onmobile phones andcomputing.
Tactile sensors may be of different types includingpiezoresistive,piezoelectric, optical, capacitive and elastoresistive sensors.[3]
Tactile sensors appear in everyday life such as elevator buttons and lamps which dim or brighten by touching the base.
Sensors that measure very small changes must have very high sensitivities. Sensors need to be designed to have a small effect on what is measured; making the sensor smaller often improves this and may introduce other advantages. Tactile sensors can be used to test the performance of all types of applications. For example, these sensors have been used in themanufacturing ofautomobiles (brakes, clutches, door seals,gasket),battery lamination, bolted joints,fuel cells etc.
Tactile imaging, as a medical imaging modality, translating the sense of touch into a digital image is based on the tactile sensors. Tactile imaging closely mimics manual palpation, since the probe of the device with a pressuresensor array mounted on its face acts similar to human fingers during clinical examination, deforming soft tissue by the probe and detecting resulting changes in the pressure pattern.
Robots designed to interact with objects requiring handling involving precision,dexterity, or interaction with unusual objects, need sensory apparatus which is functionally equivalent to a human's tactile ability. Tactile sensors have been developed for use with robots.[4][5][6][better source needed] Tactile sensors can complement visual systems by providing added information when the robot begins to grip an object. At this time vision is no longer sufficient, as the mechanical properties of the object cannot be determined by vision alone. Determining weight, texture,stiffness,center of mass, curvature,coefficient of friction, andthermal conductivity require object interaction and some sort of tactile sensing.
Several classes of tactile sensors are used in robots of different kinds, for tasks spanning collision avoidance and manipulation.[citation needed] Some methods forsimultaneous localization and mapping are based on tactile sensors.[7]
Pressure sensor arrays are large grids of tactels. A "tactel" is a 'tactile element'. Each tactel is capable of detecting normal forces. Tactel-based sensors provide a high resolution 'image' of the contact surface. Alongside spatial resolution and force sensitivity, systems-integration questions such as wiring and signal routing are important.[8] Pressure sensor arrays are available inthin-film form. They are primarily used as analytical tools used in themanufacturing andR&D processes by engineers and technicians, and have been adapted for use in robots. Examples of such sensors available to consumers include arrays built fromconductive rubber,[9]lead zirconate titanate (PZT),polyvinylidene fluoride(PVDF), PVDF-TrFE,[10]FET,[11] and metalliccapacitive sensing[12][13] elements.
Several kinds of tactile sensors have been developed that take advantage of camera-like technology to provide high-resolution data.A key exemplar is the Gelsight technology first developed at MIT which uses a camera behind an opaque gel layer toachieve high-resolution tactile feedback.[14][15] The Samsung "See-through-your-skin" (STS) sensor uses a semi-transparent gel to produce combined tactile and optical imaging.[16]
Strain gauges rosettes are constructed from multiplestrain gauges, with each gauge detecting the force in a particular direction. When the information from each strain gauge is combined, the information allows determination of a pattern of forces or torques.[17]
A variety of biologically inspired designs have been suggested ranging from simple whisker-like sensors which measure only one point at a time[18] through more advanced fingertip-like sensors,[19][20][21] to complete skin-like sensors as on the latestiCub[citation needed]. Biologically inspired tactile sensors often incorporate more than one sensing strategy. For example, they might detect both the distribution of pressures, and the pattern of forces that would come from pressure sensor arrays and strain gauge rosettes, allowingtwo-point discrimination and force sensing, with human-like ability.
Advanced versions of biologically designed tactile sensors includevibration sensing which has been determined to be important for understanding interactions between the tactile sensor and objects where the sensor slides over the object. Such interactions are now understood to be important for human tool use and judging the texture, even curvature, of an object.[19][6] One such sensor combines force sensing, vibration sensing, and heat transfer sensing.[1]
A recent breakthrough bioinspired tactile sensor lets robots "feel" their surroundings with 1.76° precision, enabling blind navigation (0.2mm accuracy) and texture recognition (97% success). Its ultra-robust design withstands extreme deformations for reliable operation in real-world environments.[6]
Recently, a sophisticated tactile sensor has been madeopen-hardware, enabling enthusiasts and hobbyists to experiment with an otherwise expensive technology.[22] Furthermore, with the advent of cheap optical cameras, novel sensors have been proposed which can be built easily and cheaply with a 3D printer.[23]