Inertial Vector Measurements Based Velocity-Free Attitude Stabilization

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 phenomenon1encountered in some unit-quaternion based attitude control schemes.