Inertial Vector Measurements Based Velocity-Free Attitude Stabilization

摘要

The existing rigid body attitude controllers (without angular velocity measurements) involve explicitly the attitude in the feedback. Unfortunately, there does not exist any sensor that directly measures the orientation of a rigid body (without any estimation procedure). Therefore the attitude must be generated from the available sensors via some attitude determination (estimation) algorithms. The most recent and efficient attitude estimation algorithms rely on the body vector measurements and the angular velocity (which is assumed to be unavailable in velocity-free attitude controllers). To overcome this circular reasoning-like problem, we propose a velocity-free attitude stabilization control scheme relying solely on body vector measurements. Moreover, the proposed control law is a priori bounded and does not lead to the so-called unwinding phenomenonUsing the unit-quaternion representation, the same attitude can be represented by two different unit-quaternion, namely $Q$ and ${-}{Q}$. This fact, often leads to the so-called unwinding phenomenon, which is undesirable since some closed-loop trajectories, for some initial conditions close to the desired attitude equilibrium, can undergo an unnecessary homoclinic-like orbit , . encountered in some unit-quaternion based attitude control schemes.