| Abstrakt: |
This paper presents a hybrid approach for the design of an adaptive sliding mode attitude controller (SMC) for earth pointing nanosatellites. Quaternion-based models are desirable, because they do not have singularities, but their multiple equilibrium points make it difficult to develop a globally stable controller. In particular, discontinuous controllers can suffer from sensitivity to measurement noise in the case of maneuvers close to 180 ∘ . Additionally, dynamic models are in general subject to a limited knowledge of the parameters involved. In order to deal with the aforementioned issues, the control strategy proposed in this study creates a hybrid sliding surface that avoids unwinding and is robust against measurement errors. Using this sliding surface, a control law is established to stabilize the closed loop, then an adaptive law is added to deal with the unknown inertia uncertainty and disturbances. In the numerical simulation, the performance of the proposed hybrid controller is compared to the discontinuous SMC that is being widely used currently. A detailed analysis of the results reveals that the hybrid approach is robust against external disturbances and parameters uncertainty. Moreover, when measurement noise is added in case of large maneuvers the hybrid adaptive SMC converges faster, and can save up to 3.5 times in energy consumption, making it more efficient than its discontinuous counterpart. [ABSTRACT FROM AUTHOR] |
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