Immersion and Invariance Adaptive Pose Control for Spacecraft Proximity Operations Under Kinematic and Dynamic Constraints

This article studies the six-degrees-of-freedom pose control issue of spacecraft proximity operations subject to kinematic and dynamic constraints, as well as parameter uncertainties. A transformed relative translational dynamics and a line-ofsight frame are introduced to facilitate the pose control design. In this context, an immersion and invariance (I&I) adaptive pose control scheme based on artificial potential functions (APFs) is proposed. Specifically, a class of APFs that are free of local minima are firstly constructed to deal with kinematic and dynamic constraints imposed by certain safety and physical requirements. Secondly, using the dynamic scaling technique, an I&I adaptive pose controller is tactfully designed. This controller is shown to be able to circumvent the realizability condition that is required for most existing adaptive control approaches, but nonetheless may not hold under dynamic constraints. Thirdly, through Lyapunov's direct method, the asymptotic stability of the closed-loop system is analyzed. The proposed method enables the pursuer to arrive at the desired anchoring point with a specified pointing, whilst satisfying both kinematic and dynamic constraints. Moreover, it depends upon the I&I adaptive design philosophy and, therefore, introduces an attracting manifold, whereby the deterministic case of closed-loop performance (no effect of parameter uncertainties) can be asymptotically recovered. Simulation results illustrate the efficiency of the proposed control scheme.