A novel mechanical attitude simulator with adaptive control for micro-satellite

Abstract

A novel simulator of satellite ADCS (Attitude Determination and Control System) was designed in the system dynamics and control research laboratory of Amirkabir University of Technology. Currently industrial models of ADCS are using air bearings to make the system suspended. A prototype was designed with ball bearings and three gimbals to provide three rotational DOFs. We believe that the advantages of our method are that is cost efficiency, improved the accuracy and performance; however, the model uses a high level algorithm for friction compensation. The attitude accuracy of the system is nearly 5 degrees. The goal of this project is tracking and control of the ADCS in conditions in which the friction torque of the ball bearings in gimbals has been compensated. The controller that was implemented in this system uses a nonlinear model based on adaptive control. First, feedback linearization is used to cancel the nonlinearities which then was modified by an adaptive control using a Lyapunov function to estimate the uncertainties such as moments of inertia, eccentricity of the center of mass, and friction. The friction model includes Stribeck, viscous, and Coulumb terms. High level estimators and identifiers are used for estimation and identification of friction model parameters. Finally, the controllers were validated by simulation results.