Further Development of a Pneumatically Powered Motion System for a High-Speed Scanner
Boyd, Matt S.
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This paper details the redesign of a previous pneumatic motion system for a linear scanner to meet higher performance requirements. The previous design featured a scanner head, two air bearings, and two pneumatic cylinders and was intended to propel the scanner head back and forth in a linear motion at speeds up to 5 m/s. Air was supplied to the air bearings by tethering the scanner head to an air supply with plastic tubing. At speeds nearing 5 m/s, the tether began to oscillate violently and the repeated impacts of the scanner head and pneumatic cylinders caused the entire structure to vibrate. Also, large amounts of energy were lost due to momentum transfer between the scanner head and cylinders and friction within the cylinders themselves. Further, none of the energy of the impact was recovered. These problems were corrected by designing and purchasing new equipment and slightly altering the operation of the scanner. A system of needles was designed to provide air to the air bearings without the use of a tether. New pneumatic cylinders with exceptionally low friction were purchased and a method of precharging the air on the rod sides of the cylinders to a certain pressure was devised to add energy back into the system that is lost during operation. A special valve was designed to accomplish the addition of air into the precharge volumes. Also, a mechanism was designed to greatly minimize the vibration of the table. This structure consists of a large, suspended, inertial mass which holds the pneumatic cylinders so they are not actually mounted on the table which holds the scanning track.