Dynamic scaling-based noncertainty-equivalent adaptive spacecraft attitude tracking control

This paper presents a novel dynamic scaling-based non-certainty-equivalent adaptive control method for the attitude tracking control problem of spacecraft in the presence of inertia uncertainties. By virtue of the modified dynamic scaling factor and an angular velocity observer, the proposed controller provides a more direct approach to circumvent the integrability obstacle of the basic immersion and invariance (I&I) adaptive method without any information about the bounds of system uncertainties. Compared with the existing filter-based non-certainty-equivalent adaptive attitude controller, the proposed controller achieves significant order reduction in closed-loop systems and removes the constraint on initial values of the parameter lock property. The dynamic gains in the proposed method are modified to have linear growth in the dynamic scaling factor and restricted by the given upper bound in order to avoid bad transient performance. Numerical simulations are presented to highlight the superiority of the proposed method compared with the filter-based I&I control method.