A decoupled sliding mode controller and observer for satellite attitude control

A decoupling sliding mode controller and observer is derived for spacecraft attitude tracking maneuvers and regulation in terms of quaternions. The controller sliding manifold guarantees globally stable asymptotic convergence to the desired time dependent quaternion profile and the quaternion tracking error responds as a linear homogeneous vector differential equation with constant coefficients and desired eigenvalues placement. The full order sliding mode observer is used to avoid quaternion error differentiation noise and to eliminate the need for angular velocity measurement