| || Method for Thermo-optic Analysis in a Star Sensor
Author : Liu, Hai-bo;Tan, Ji-chun;Yang, Jian-kun;Li, Xiu-jian;Fan, Qing-chun
Source : Defence Science Journal ; Vol:60(3) ; 2010 ; pp 276-281
Subject : 681.586 Sensors;Defence Science Journal
Keywords : Star sensor;optical system;thermo-optic analysis;finite element analysis;FEA;ray tracing
Abstract : An autonomous star sensor is a highly accurate attitude-measuring instrument used in spacecraft, and its performance is restricted by ambient temperature of the outer space. This paper puts forward an effective scheme to the thermooptic analysis using finite element analysis (FEA) and ray tracing in star sensor. Specific difficulties: (a) how to evaluate thermo-optic effect in star sensor, and (b) how to make FEA results useful in optical design mode have been resolved using the scheme. Based on this scheme, the errors of star sensor, which are caused by thermo-optic effects, can be investigated in any complicated temperature condition, and the required temperature scope for the thermal design can be achieved. For example, the errors of the star sensor were 0.0863 and 2.2933, when the temperature differences of the experimental optical system were 10 °C and 5 °C in axial and lateral, respectively.
| || Optimising Performance of a Cantilever-type Micro Accelerometer Sensor
Author : Joshi, B. P.;Chaware, A. S.;Gangal, S. A.
Source : Defence Science Journal ; Vol:57(3) ; 2007 ; pp 261-269
Subject : 681.586 Sensors
Keywords : Micro sensor;FEA;MEMSCAD;Accelerometer;Add-mass technique;Piezoresistive sensor
Abstract : A technique for optimising performance of cantilever-type micro acceleration sensor has been developed. Performance of a sensor is judged mainly by its sensitivity and bandwidth. Maximising product of these two important parameters of inertial sensors helps to optimise the sensor performance. It is observed that placement of a lumped mass (add-mass) on the sensor's proof-mass helps to control both sensitivity and the first resonant frequency of the cantilever structure to the designer's choice. Simulation and modelling of various dimensions of rectangular structures for acceleration sensor with this novel add-mass technique are discussed. Coventorware MEMSCAD has been used to model, simulate, and carry out FEM analysis. A simple analytical model is discussed to elaborate the mechanics of cantilever-type micro accelerometer. The comparison of the results obtained from analytical model and the finite element simulations reveal these to be in good agreement. The advantages of this technique for choosing the two most important sensor parameters (i.e., sensitivity and bandwidth) of an inertial sensor are brought out.