Integrated modelling of microvibrations induced by Solar Array Drive Mechanism for worst-case end-to-end analysis and robust disturbance estimation

Abstract

Modern and future observation Space missions face increasingly more demanding pointing performance requirements. This is accompanied with the development of larger lightweight flexible structures. This paper outlines a methodology for modeling a generic multi-body flexible spacecraft in an end-to-end fashion within the Two-Inputs Two-Outputs Port framework: from disturbance all the way to pointing performance by tacking into account all the uncertainties of each sub-system. A particular focus is dedicated to a novel generic model for Solar Drive Array Mechanisms and its harmonic disturbances produced by the micro-stepping driver and the gearbox imperfections. The proposed model is validated with the on-board telemetries of a European spacecraft. Moreover this paper shows how the proposed model-based approach can be easily used for control design and closed-loop robust performance analysis. Worst-case scenarios of mechanical parameters combination are investigated to provide robust performance certificate of the reference study case. A Linear Parameter-Varying observer, scheduled by the solar array rotor angle, is finally proposed in order to estimate the disturbance torques induced by the gearbox imperfections just using the measurements coming from a classical attitude control system: a star tracker and a gyrometer.

Worst-Case Pointing Performance Analysis for Large Flexible Spacecraft

“…This paper provides a novel tool in MATLAB and SIMULINK environment to perform pointing error budgeting called Pointing Error Library (PELIB) that aims to fill this gap. PELIB which consists of various Matlab functions is a natural extension of the Satellite Dynamics Toolbox (SDT) [5,6,7,8,9,10] already implemented by the authors in the past under ESA, CNES, ONERA, Thales, and Airbus DS contracts for modelling of complex flexible space systems in minimal LFT form. Each function in this library follows the standard and methodology described in ECSS and ESA Handbook from the classification of error sources to the evaluation of pointing error budget.…”