Inherent nonlinearities and external disturbances alter the dynamics of a satellite attitude control system. This research work introduces a fault tolerant scheme for sensor faults in a satellite attitude control system. To linearize the system dynamics, a Tagaki-Sugeno (T-S) fuzzy model is constructed by approximating the nonlinear function in form of linear models at appropriate operating points. A T-S fuzzy observer based on descriptor systems is constructed using a Linear Matrix Inequality method to simultaneously estimate the states of the system and sensor faults. Constant and time-varying sensor faults are both set as auxiliary state vector in the system dynamics to create an augmented descriptor system. Stability analysis, control design and estimation of the sensor faults and the convergence of the observer were validated using Lyapunov theorem. The estimated states are fed back into the plant to improve the system’s stability and a compensation scheme was designed to improve the system’s output. The workability of this scheme was proven through simulations on MATLAB/SIMULINK platforms.
January 22, 2016
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