Development of an air servo displacement sensor

This paper introduces a new type of displacement sensor called an “air servo displacement sensor.” The sensor’s piston automatically follows a measured object using a pneumatic servomechanism with a nozzle-flapper that acts as a detecting device. Because the piston is supported by an aerostatic bearing, it experiences almost no friction. An optical linear scale mounted on the piston is used to measure the displacement of the measured object because the gap between the nozzle and the measured object is maintained at a constant level. As a result, this new sensor can successfully perform non-contact displacement measurements over a much longer measuring range, when compared to the traditional air micrometer. The optimal parameters for the sensor structure were obtained using simulations and experiments. Performance accuracy tests with a micrometer showed a repeatability error below ±0.5 μm and a linearity error below ±2 μm, with a measuring range beyond 10 mm. It has been verified that that the sensor exhibits a sufficient level of accuracy for the operational requirements.