Nonlinear Geometric Observer Design
Student: Y. Wang
This project considers the application of geometric nonlinear control methods to design multi-output continuous-time nonlinear observers. The approach exploits the additional degree of freedom afforded by multiple outputs and focusses on methods with block triangular structure. A main feature of the Block Triangular Form (BTF) coordinates is that they allow single-output designs to be performed in a decentralized manner subsystem-at-a-time on lower dimensional subsystems. The upper states are effectively treated as known measurements given that we have already designed their convergent observer. The reduced dimensionality of the designs can significantly reduce the complexity of the entire multi-output design. In addition to the general BTF, we also consider a transformation to a less broadly applicable Block Triangular Observer Form (BTOF). This form allows for classical exact observer error linearization techniques to be applied in a decentralized manner.
Flatness-based Control of Underactuated Nonlinear Systems
Student: C. Aguilar
This project considers an attitude trajectory tracking problem for a two-input underactuated rigid spacecraft. The attitude of a spacecraft is its orientation in space, and hence, the attitude control problem involves directing the spacecraft to achieve a specified orientation. Spacecraft attitude control has many applications. For example, it is used to avoid solar or atmospheric damage to sensitive components, to point directional antennas and solar panels, and to orient rockets used for orbit manoeuvres. From a practical and theoretical point of view, it is of interest to consider the attitude control problem when some of the actuators have failed, that is, when the spacecraft is underactuated. The literature on trajectory tracking of the attitude for an underactuated spacecraft is scarce compared to that on stabilization. Differential flatness is used in this project to provide a solution to the tracking problem.