In this paper, a new type of displacement sensor with pneumatic feedback system is proposed. The piston of the sensor can follow a measured object automatically by a pneumatic servomechanism with a nozzle-flapper as a sensor. For precise measurement, the piston is supported by an air bearing and has very low friction. The gap between the nozzle and the measured object is kept fixed, so that the displacement of the measured object can be detected by measuring the displacement of the piston by an optical linear scale attached to it. As a result, this sensor can realize noncontacting displacement measurements and has a much longer measuring range compared with the traditional air micrometer.
The optimal parameters of the sensor structure are obtained by means of simulation and experiment. When the accuracy of the sensor is verified using a micrometer, the repeatability error of the sensor is below ±0.5μm and the linearity error of senor is below ±2μm with a measuring range beyond 10mm. It is concluded that this sensor has sufficient accuracy, with the resolution of linear scale to be 0.5μm.
