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Motion System Design

Better by design: Think matter

When it comes to putting sensors in a fluid-power cylinder, the most common approach is to gun-bore the piston rod and mechanically fasten positioning apparatus and associated electronics. It's not very economical, however, especially for high precision. It also limits stroke and is prone to damage.

A more streamlined approach, using advanced composite technology, is to make the sensor and cylinder wall one and the same. The story begins with a composite developed for stealth aircraft that was later refined with engineers at Xerox. The material in its newest incarnation has both electrically insulating and conductive properties, and is formed with conductive fibers and an insulating layer of an epoxy-fiberglass laminate right into the walls of a new kind of fluid-power cylinder. This embedded conductive-fiber architecture is the signature feature of a product called the Polyslide Intrinsic Sensing Technology (IST) Smart Cylinder, developed with Georgia Tech spinoff, Sentrinsic LLC, Atlanta. Sentrinsic's IST incorporates a non-contacting coupling between the cylinder's piston and an Intrinsic Sensing tube, so voltage amplitude (sensed on the pickup) reflects the moving piston position without a physical wiper. Polygon's completely embedded fiberglass structure maintains the IST's repeatability and physical simplicity.

Soon, designers may create systems with resolution, linearity, outputs, and manufacturing cost tailored to specific application needs. Already at work in U.S. military bomb-detection robotic manipulation, smarter health-monitoring fluid-power cylinders are on the horizon, and the embedded circuitry can provide sensing for other products beyond pneumatic or hydraulic cylinders as well.

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