Measuring the position of a shaft with both linear and rotary motion is a challenging design problem that usually involves two sensors, one for each axes of motion, and two input ports. Three engineers at MTS Sensors just received a patent (U.S. patent 6,600,310) for a sensor technology that does both, potentially saving engineers cost and complexity in their designs. The sensor is an extension of MTS' Temposonics non-contact position sensor technology, which exploits the capability of a magnetostrictive material to deform under the application of a magnetic field. The sensor works by inducing a sonic wave in a magnetostrictive waveguide through the interaction of a magnetic field from a ring-shaped permanent magnet that moves along the sensor tube and a current—or interrogation—pulse. By measuring the elapsed time for the resulting strain pulse to travel along the waveguide to a detector head, the magnet's absolute position can be determined with high accuracy. This sensor takes the concept a step further by employing a second permanent magnet that is helical in shape. In essence, this second magnet provides a reference position so that the amount of rotation of the linear magnet on the shaft can be determined. A first application for the technology is in automatic manual transmissions. Though that may sound like an oxymoron, automakers, in fact, have been looking at ways to take a standard transmission with clutch pedal and manual shift gear selector and automate the two steps. At least two companies are evaluating MTS's two-magnet magnetostrictive position for sensing both linear and rotary motion of the shift shaft as it moves through an H pattern to select the appropriate gear cluster. Engineers say that the sensor resolution can be up to 2 microns, although a version targeted at lower-cost applications has a resolution on the order of 40 microns.
DIY candy, journeys to Mars, coding for road trips, and more. These STEM (science, technology, engineering, and math) activity options will keep kids engaged this summer, from 10-minute activities to more advanced undertakings.
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