VELOCITY-FREE ATTITUDE STABILIZATION WITH MEASUREMENT ERRORS
Résumé
This paper addresses the rigid body attitude stabilization problem with the globally nonsingular quaternion representation. Specifically, a passivity-based output feedback controller is considered in the presence of measurement errors. In the absence of uncertainties, it is well known that the body orientation can be stabilized via dynamic extensions in the form of a first-order stable filter from the passivity framework. Once the filter is driven by a noise-corrupted quaternion and the controller employs both the imperfect attitude measurements and the output of the filter, the stability properties of the closed-loop system are weakened. Also, the robustness properties cannot be readily established through the Lyapunov analysis with a typical Lyapunov-like function used for this problem since the time derivative of the function is only negative semi-defmite. However, the strictification technique allows us to build a partially strict Lyapunov-like function and eventually to establish certain conditions that guarantee the boundedness of trajectories.