Research On Deployment Control Of Tethered Satellite System

As a new type of space system,tethered satellite has excellent characteristics in some aspects because of its mutual connection with the actual structure,so it has very important significance in engineering application.The main research of tethered satellite is focused on model and control.Based on the previous models,this paper takes the sliding mode control theory as the core and researches control problem for set position's deployment of tethered satellite system.Firstly,the "dumbbell" model of tethered satellite system is established by the second Lagrange equation.Gauss pseudospectral method is used to plan the optimal trajectory,get release curve where rope length changes over time,and make the in-plane angle close to zero in the end of deployment.Then the traditional sliding mode algorithm is used to track the optimal trajectory,and optimal control simulation of the system is obtained.At the same time considering the traditional sliding mode control's inevitable chattering problem,using the second order sliding mode algorithm to weaken the chattering item,enhance system stability and effectively guarantee the feasibility of its engineering application.Then tethered satellite is considered as an underactuated system.Without any increase in the complexity of algorithm,the sliding mode algorithm based on hurwitz stability is used.Using genetic particle swarm optimization algorithm as intelligent optimization on the sliding surface parameters,the sliding mode surface parameters of optimal convergence time is obtained.Based on RBF neural network's good approximation effect and the characteristic of rapid convergence,the chattering of sliding mode index reaching law's gain is adjusted on real time which can make system not out of sliding mode with minimum cost,optimize control tension of deployment and completely eliminate the chattering phenomenon of driving force within the controllable precision.The Newton-Euler method is used to get the tethered satellite multi-body dynamic model which put the rope into several segments,increases the complexity of the model,and can be more reflecting the reality of deployment of the tethered system than the simple model.Then all kinds of control algorithm we had are used on the bead point model for verification.The results reflect that the various control algorithms in this paper are feasible on practical application of real tethered satellite system.