Model predictive control with output feedback for a deorbiting electrodynamic tether system
Hao Wen, Zhengong Zhu, Donging Jin, Hayan Hu
Abstract: This Note presents an output feedback control law of electric current for achieving a fast and stable deorbit of an electrodynamic tether system. The proposed control scheme consists of two main steps. The first step is to remove the requirement of measuring full state. For this purpose, a moving-horizon state estimator is developed to estimate the unmeasured angular states using the most recent samples of the measureable outputs, which are supposed to be the relative end-body positions. The second step is to synthesize a control law for optimizing the deorbiting performance while accounting for the system constraints and nonlinear dynamics. Following the idea of model predictive control, the feedback control law is determined in the second step by solving an open-loop nonlinear optimal control problem with the state estimate as its initial condition. Meanwhile, the imposition of hard state constraint is avoided in the second step by developing an adaptive law of weighting gain for restricting the amplitudes of tether libration. The problems of state estimation and predictive control are discretized using a multiple-interval pseudo-spectral method and then solved via nonlinear programming. Numerical case studies successfully demonstrate that the proposed control schemes achieve the preceding control requirements. As indicated by the simulation results, the system orbits obtained using the proposed schemes demonstrate a clear decreasing tendency in the apoapsis altitude over the time, and successful stabilization of the tether libration can be achieved in the absence of full state feedback and hard state constraints. （期刊无摘要，此摘要为该文简介）
原文链接: https://arc.aiaa.org/doi/abs/10.2514/1.G000535
