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Article Excerpt
Streamlined, robust, readily configurable, and economical tactile sensors have key opportunities in varied applications that can benefit from having improved sensing of human touch or presence, impact, or force/pressure, such as robotics, computer or game input devices, musical instruments, sports equipment, toys, security, and automotive (e.g., occupancy sensing or crush zone sensing). Advanced in intelligent machines that offer autonomous mobility generate opportunities and requirements for tactile sensors (as well as vision sensors). Tactile sensors can enhance the safety of such machines and help prevent contact or collision with other objects or systems.
Canpolar.East, Inc. (St. John's, NF, Canada, 709-722-6067)(www.canpolar.com/www.kinotex.com), a licensor of vision and tactile sensor systems and components, has been partnering with companies to cogently leverage its Kinotex(r) fiber-optic tactile sensor technology, originally developed for the Canadian Space Agency, into very down-to-Earth and significant applications, such as touch controllers (used, for example, in PCs and musical instruments), bed patient monitoring, industrial robots, and seat occupancy sensing.
In 1995, the Canadian Space Agency, developer and supplier of the robotic manipulator systems for the International Space Station, contracted a consortium led by Canpolar East to develop a tactile sensing technology for robotic manipulator contact and collision sensing. The optical cavity sensor that was developed can emulate human touch and cover the entire robotic limbs to provide the tactile feedback to prevent the robot's arms from colliding or prevent a robotic hand from inadvertently crushing an object. The patented technology (U.S. Patent # 5,917,180) was licensed by Canpolar East, and is being applied in and developed for varied markets/applications under the trade name Kinotex.
The Kinotex pressure/displacement sensor employs an innovative sensing principle based on deformation of an optical integrating cavity. The sensor is fabricated from common polymer foam materials, such as silicone or urethane. Deformation of the foam generates a change in optical properties proportional to the deformation, and the change can be sensed by a simple optical transducer.
The Kinotex sensor functions by detecting a change in energy intensity in and around an illuminated integrating cavity (comprised of polymer foam material). Deformation of the integrating cavity by an external influence (e.g., pressure) induces a change in the illumination energy intensity. This change is measured; and the information can be used to infer the state of deformation.
The integrating cavity in the Kinotex sensor is typically not a physical cavity, but a virtual space in an isotropic scattering medium. The dimensions of the virtual cavity are defined by the energy scattering properties of the medium.
To robustly measure the characteristic scattering length (CSL) of the medium (the parameter of interest), an illumination source with controlled output energy is embedded in the compressible scattering medium. An energy detector is embedded adjacent to the illumination source in such a way that it cannot receive any energy directly radiating from the source and will only see scattered energy. If the dimensions of the source and the detector apertures are small compared to the CSL of the medium, the detector will see the integrated intensity of the scattered energy in its vacinity.
Integration takes place over a volume around the detector with a radius equivalent to about one characteristic length. The CSL of the medium defines a virtual integrating cavity around a source or a detector. The integrating cavity shrinks if the CSL is reduced. The intensity of the scattered energy inside the cavity increases, as the integrating cavity surrounding an energy source shrinks. If an energy detector is located inside this cavity, it will register an increase in integrated energy intensity. However, if an energy detector is distant (<1 CSL) form the source, it will register a decrease in integrated scattered energy intensity. An appropriately spaced array of sources and detectors in a compressible isotropic scattering medium is bale to provide information about the location, extent, and direction of a compression event.
Key benefits of the Kinotex sensor (whose functional performance is comparable to other force or displacement sensors) include simplicity, robustness, amenability to being inexpensively fabricated in large arrays, and rapid response speed . The Kinotex sensor can be fabricated in varied, arbitrary shapes; and sensitivity and compliance can be engineered to meet diverse user requirements.
The number of sources and detectors used in the Kinotex sensor depends on the application. In crush zone intrusion sensing, a single light source and one receiver can be used. For other applications, it is possible to build a Kinotex sensor containing hundred of transmitters and receivers.
The Kinotex sensors can...
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