This study focuses on stabilizing the libration dynamics of an electrodynamic tether system (EDTS) using generalized torques induced by the Lorentz force. In contrast to existing numerical optimization methods, a novel analytical feedback control law is developed to stabilize the in-plane and out-of-plane motions of a tether by modulating the electric current only. The saturation constraint on the current is accounted for by adding an auxiliary dynamic system to the EDTS. To enhance the robustness of the proposed controller, multiple perturbations of the orbital dynamics, modeling uncertainties, and external disturbances are approximated using a neural network in which the weighting matrix and approximation error are estimated simultaneously, such that these perturbations are well compensated for during the control design of the EDTS. Furthermore, a dynamically scaled generalized inverse is utilized to address the singular matrix in the control law. The closed-loop system is proven to be ultimately bounded based on Lyapunov stability theory. Finally, numerical simulations are performed to demonstrate the effectiveness of the proposed analytical control law.

A group of cooperative agents can finish complicated missions that are difficult for a large machine. In the past two decades, spacecraft attitude coordination has attracted significant research attention owing to its wide potential applications. This paper presents a survey of recent research progress on the spacecraft attitude consensus problem, paying particular attention to the papers published in major aerospace, dynamics, automation, and robotics journals since 2015. Attitude consensus concepts for centralized, decentralized, and distributed cases are reviewed. This overview summarizes results on system dynamics and consensus algorithms based on frequently used attitude representations, such as Euler angles, modified Rodrigues parameters, unit quaternions, and rotation matrices. Studies conducted under complicated operating conditions are also covered. Experimental results on attitude consensus are discussed. In the final section, the main conclusions are drawn and several potential research directions are provided.

Various promising applications of electrodynamic tether have been proposed for space missions over the past decades. A crucial issue of these missions is to deploy an electrodynamic tether under a rapid and stable state. This paper aims to stabilize the libration motions of a bare electrodynamic tether during its three-dimensional deployment. The tethered system under consideration consists of a main-satellite and a sub-satellite connected to each other through a bare electrodynamic tether. A widely used dumbbell assumption considering the tether as rigid and inflexible is adopted to facilitate the dynamic modeling and analysis of the tethered system. A pair of active control laws is synthesized by simultaneously regulating the electric current and tether tension to achieve an efficient stabilization of the three-dimensional libration of the bare electrodynamic tether in the deployment process. Moreover, comparisons of three groups of numerical simulations are performed to evaluate the influences of orbital inclinations and geomagnetic field models and the performance of the active control laws.