Study Of Rendezvous Guidance And Control Algorithm Of Tethered Satellite;study Of Rendezvous Guidance And Control Algorithm Of Tethered Satellite

The proposal of Tethered Satellite System(TSS) created a new path for the era of space construction, which also has an important applied potentiality in the field of space system maintenance and support. To come true this application, finding out the methods of tethered satellite's guidance and control algorithm on rendezvous is an emergency problem. For solving this problem, this thesis is based on an important project under National 863 Problem in the field of aerospace, focus on the research of guidance and control algorithm on rendezvous of TSS's sub-satellite and in-plane or out-of-plane target. The main contents of this thesis are depicted as follows:Firstly, the rendezvous tasks, guidance and control strategies of TSS's sub-satellite and in-plane or out-of-plane target are designed. For determining the rendezvous way on sub-satellite and in-plane target, two conditions of how to change the sub-satellite orbit plane are proposed, which can also simplify the design of guidance and control strategies and their algorithm on rendezvous. The rendezvous phase is divided into initial and final phase for correcting the initial deviation and optimizing the TSS's performance function.Secondly, we focus on the method of rendezvous guidance and control algorithm of sub-satellite and in-plane target(in in-plane condition), and solve the following two problems: one is how to prolong the relative position holding time, the other is how to control the relative attitude of sub-satellite and in-plane target.For solving the first problem, two control methods are presented: one is joint control law of combining tether length rate with variable structure control law when the tether is taut(in taut condition) and variable structure control law when the tether is loose(in loose condition). All methods are in consideration of model's uncertainty and interference, analyze the main reasons of the control error and point out the way to reduce its impact on control error.For solving the second problem, the relative attitude control method with Lyapunov function is proposed. The proposed method can also be used in the case that the tether tension arm is unknown. In addition, guidance and control algorithm in approach phase are also studied. However, in the initial phase, trajectory planning is adopted to build guidance algorithm, which is a combination of length rate and variable structure control. The stability of the mentioned algorithm is also analyzed, and the control algorithm takes model's uncertainty and interference. In the final phase, the reason for optimal control is introduced, and the optimal control is realized with the application of Gauss pseudospectral. The conclusion is reached that when the Hamilton function stays as a constant along the optimal orbit, the solution is optimal. Finally, the method of rendezvous guidance and control algorithm of sub-satellite and out-of-plane target(in out-of-plane condition) is studied, and the following two problems are solved: one is how to judge the rendezvous way in out-of-plane condition, the other is how to prolong the relative position holding time in out-of-plane condition. For solving the first problem, the relationship between tether parameters and out-of-plane orbit plane is deduced in loose condition. For the second problem, variable structure control algorithm is presented in loose condition, which can be used in the case that model's uncertainty and interference are existed. Besides that, the guidance and control algorithm in taut condition are also researched, and the reason is to demonstrate the control method in loose condition is prior to the control method in taut condition. In addition, the approach guidance and control algorithm are also studied, and the difference between the case of in-plane condition and the case of out-of-plane lies in the effect of orbit plane.