Abstract Details

Name: Varun Kumar
Affiliation: Indian Institute of Astrophysics
Conference ID: ASI2017_489
Title : Analysis and design of planar flexible inductor for segment edge sensing in Segmented Mirror Telescopes
Authors and Co-Authors : Padmakar Singh Parihar, Indian Institute of Astrophysics Bangalore. Athul Nakulan, Christ university Bangalore.
Abstract Type : Oral
Abstract Category : Instrumentation and Techniques
Abstract : Edge sensor is a vital component of any segmented mirror telescope (SMT) and their performances highly depend on the performance of edge sensor. In order to achieve very high spatial resolution (few nanometer) and sensitivity, all mirror segments of SMT’s must be precisely positioned with respect to each other to form a single primary mirror. Capacitance-based displacement sensors are widely used for this purpose, but they have inherent sensitivity towards humidity and dust which makes them unsuitable for telescopes installed at high gradient humid regions. Inductance based sensors produce promising results both the cases. Inductive edge sensors work on the principle of mutual inductance variation between two planar inductors. These planar inductors are designed in such way that, once they are mounted on the back of adjacent segment edges, their movement in tip, tilt and piston cause changes in mutual inductance. The nanometer range spatial requirement makes the design of planar inductor quite challenging. The inductive coils are first simulated and analyzed using electromagnetic FEA software for different coil parameters such as geometry of the coil, fixed and variable trace densities, different number of turns in primary and secondary coil etc. The design considerations include number of degree of freedoms to be sensed, required travel range, required spatial resolution and required sensitivity. Based upon the result of simulations, a rectangular planar inductive coil, which gives large sensing range, higher sensitivity, linearity over large range and less cross coupling between various sensing dimensions has been chosen for further evaluation. The coils of the inductive sensor are fabricated on flexible polyimide substrate using classical PCB manufacturing technology which ensures very low weight, thermal stability and it can take the shape of glass block on which it is mounted, this in turn help to improve the linearity of the sensor. The inductive sensor design and development work is being carried out at ITCC laboratory of Indian Institute of Astrophysics. Here we report the design process and current status as well as test results obtained in the laboratory.