Dynamics And Tension Control Of Space Tethered Satellite System

In recent years, space tethered satellite system has been highly valued by the earth and space science field, its broad application prospects can be foreseen in fields like earth orbit conversion, artificial gravity, near-Earth space exploration and deep space exploration.Space tethered satellite system has the character of strong nonlinearity, weak coupling and underactuated drive, in the main time it has limited availability of feedback information, uncertainty of environmental factors and high control reliability requirements, which makes the study of the dynamics and tension control has theoretical significance and engineering application prospect. This article aims to study the dynamics and tension control of tethered satellite systems, by building up the dumbbell model and bead chain model, using fractional-order control and nonlinear backstepping control. The specific research work can be summarized as follows:First of all, based on the second class Lagrange equation, this paper establish kinetic equations of tethered satellite system dumbbell model and gives the dimensionless form of three-dimensional dynamic model, also, by the linearized equations, this paper reviews the classic linear state feedback tension control features which mains using the linear feedback of rope length and its derivative to achieve steady deployment and retrieval of tethered satellite system.Secondly, through the analysis of the dynamics of tethered satellite system dumbbell model, this paper convert it to underactuated Lagrangian system with symmetry, by using appropriate diffeomorphism transformation, a strict feedback form can be deduced and Backstepping control can be designed. The paper also considers the achievability and gives concrete form of the controller, simulation is done to show the effectiveness of the method.Thirdly, in order to take full advantage of the historical memory effect of fractional calculus and consider classic tension control can not achieve high speed control and no overshoot at the same time, this paper brings a new fractional tension control and gives the discrete controller, simulation is done to show that fractional tension control is faster on the release time and retrieval time while having totally no overshot of the system in the same time.Last but not the least, in order to observe the specific form of the space tether, by discretization of the tether, this paper builds up a discrete chain bead tethered satellite model. Different forms of the space tether under different control methods can be observed by bring the control laws for rigid model into the discrete chain bead satellite model.