Research On Attitude Motion Planning And Tracking Control Of Multibody System In Flexible Space Based On Pseudospectral Method

With the development of the aerospace technology,the structures of the spacecraft become more complicated.Free-floating space robots and spacecraft systems with solar arrays have been widely used in space tasks.Under this background,it is necessary to further study the attitude dynamics and control problems of the rigid-flexible space multibody systems.Space robots are considered to play a more and more important role in future space activities,since they can replace human beings to complete several required tasks in outer space.For a free-floating space robot,due to the strong dynamics coupling between the base spacecraft and the manipulator,we can attain the manipulator joints as well as the base spacecraft to the expected configuration at the same time via planning the motion of the manipulator joints.Besides,due to the lightweight feature of the space manipulator,the structural flexibility of the manipulator links should be taken into account so as to meet the requirements of high tracking accuracy and great reliability.As for the attitude dynamics and control of flexible-rigid space multibody systems,the attitude motion planning and trajectory tracking control problems of planar flexible space robot,spatial rigid space robot,and flexible spacecraft solar arrays are studied in this paper.The main content of this paper is as follows:Firstly,the dynamics models of the flexible-rigid space multibody systems,such as planar flexible space robot,spatial rigid space robot,and flexible spacecraft solar arrays,are established based on the Lagrangian method.It is noted that the elastic deformation of the flexible component is described approximately by the assumed mode method.Secondly,the relevant knowledge of the pseudospectral method is introduced.The basic principles and calculation processes of how to use the pseudospectral method to solve the attitude motion planning problem and how to use the indirect pseudospectral method to solve the trajectory tracking control problem are listed.Thirdly,the attitude motion planning problem of the free-floating space robot and the optimal control problem of the deployment process of the flexible spacecraft solar arrays are studied.The attitude motion planning problem of the flexible-rigid space multibody systems is transformed into a nonlinear programming problem by using the pseudospectral method.Then the sequential quadratic programming algorithm is applied to solve the nonlinear programming problem and obtain the optimal trajectory and the optimal controlinputs of the system.Fourthly,the indirect pseudospectral method is used to track the optimal reference trajectory of the flexible-rigid space multibody systems obtained by the pseudospectral method.The trajectory tracking problem is converted to a two-point boundary value problem based on Pontryagin's minimum principle.Pseudospectral method is used to discretize the two-point boundary value problem and obtain the closed-loop optimal state feedback control law.This process dosen't require any integration calculations and has good performance in real time.In this paper,the attitude motion planning and trajectory tracking control problems of the flexible-rigid space multibody systems,such as free-floating space robots and flexible spacecraft solar arrays,are studied.The proposed attitude motion planning and trajectory tracking control algorithms have some theoretic value and the engineering meaning.