Realization and installation technique of a capacitive displacement sensor with nano-meter resolution and wide range

Abstract

CLECDiS (contact-type linear encoder-like capacitive displacement sensor) is an improved area-varying capacitive displacement sensor for covering the millimeter range with nanometer resolution. Although the sensor incorporates a new contact mechanism for high sensitivity with a long measurable range, it faces the difficulty of insufficient repeatability of its output signal. The insufficient repeatability is dominantly due to a non-reliable contact condition, because a small change of the contact condition leads to significant distortion of the output signal in the contact operation of the sensor. For this reason, a measurement or positioning system based on CLECDiS remains to be developed, despite its merits such as high dynamic range and easy fabrication.In this thesis, to achieve the implementation of the sensor, various techniques are presented for enhancing repeatability of CLECDiS such as global planarization, electrode sets configuration, drift analysis, shape variation analysis and contact condition control. By using these techniques, the sensor was improved with longer lifespan (over 4 times better), reduced drift, improved sensitivity, and much better repeatability (about 30 times than one of before). Tests of these are performed in this thesis, and the stages using the presented methods are described here (the stages are reported in other articles by co-researchers). In addition, a new type CLECDiS for improving yaw characteristics is presented. The new model sensor has a mechanical guide on its surface for guiding a sensor plate, so it is called 'the guide-type'. The guide-type sensor was designed, fabricated and tested its feasibility. The guide-type sensor has shown its potential to achieve more convenient assembly and higher reliability by reducing yaw error.In summary, the implementation techniques are working well, and they are able to be used for achieving various high dynamic range and ultra-precision positioning system.