Robust rigid-body attitude backstepping control

In this work, we present a rigid-body attitude control strategy for tracking desired time-varying orientation under unknown-but-bounded disturbances. The control scheme aims to achieve nominal performance and disturbance attenuation. Initially, a nominal controller is designed to guarantee asymptotically convergence of the error between nominal and reference orientations to the origin in the absence of disturbances, ensuring nominal system performance. Thereafter, considering unknown-but-bounded disturbances, an auxiliary robust adaptive backstepping control approach based on projection modification is employed to ensure the maximum tracking error deviation is ultimately bounded and the adaptive parameters remain bounded. Experimental results with a nano quadcopter corroborate our proposed control strategy.