Ghulam Farid, Hongwei Mo, Asad H. Baqar, and Syed M. Ali
Quadrotor modelling, UAV, nonlinear control, static feedback linearization
Attitude stabilization along with trajectory following control of a quadrotor aerial robot is a quite problematic challenge due to its instinctive underactuation property. For an underactuated system, selection of output states for linearization is a critical issue. A quadrotor typically owns six output states to be controlled with only four inputs. This study focuses on a static feedback linearization approach and selected outputs are altitude and attitude states, while internal dynamics due to remaining two Cartesian states (x, y) are stabilized using a simple feedback loop. The proposed scheme avoids the use of dynamic feedback linearization to restrain the higher order Lie derivatives from appearing in a controller design process. Three control loops are incorporated in the design instead of conventional two loops and the corresponding advantage is addressed. In addition, comprehensive mathematical modelling is presented that reveals the true nonlinear nature of quadrotor dynamics. These nonlinear dynamics are effectively cancelled out using static feedback which results in a linearized plant model and then classical linear control is applied. Finally, simulation results are presented which validate the superior performance of the adopted control scheme over the avoided one.
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