Configuration Control Of Free-Floating Space Robots

The research of the space robots is the hot issue in robot field. This thesis finishes following two tasks according to the free-floating robots: the first part is the model construction and analysis for free-floating space robots, the second part is designing the controller based on the model. The second part solves two main problems, including the end-effector point to point control and contour tracking control.Firstly, the kinematic and dynamic models of free-floating space robot are built. Since there isn't any external force exerting on the space robot, the position of the centroid does not change on the free-floating condition, at the meantime, the whole system fulfills the conservation of linear momentum and angular momentum. Thus the paper takes the centroid of the system as the origin of the inertial coordinate and derives the model according to this coordinate. The generalized Jacobian matrix formula can be obtained through derivation of the kinematic model, it describes the relationship between the velocity of the end-effctor and the joint angle. Based on these works, the dynamic singularity and the manipulator workspace of the space robot can be further analyzed. Through comparisons of the models between the ground robots and space robots, the paper concludes that without dynamic singularity, any control algorithm which can be used for fixed-based manipulators also can be employed in control of free-floating space manipulator systems.Secondly, the end-effector point to point control problem of free-floating space robot is investigated. In order to work out this question, the paper obtains the linear state equation by linearizing the space robot model on the operating point. Then a controller is devised by using the parametric approach. The performance index is derived according to the mission requirements, and the final control law can be concluded through optimizing the performance index. The controller's real-timeness and robustness are revealed by simulation outcomes. Meanwhile, this thesis also utilizes the parametric approach to the disturbance suppression when the space robot is in equilibrium, and the controller's effectiveness is verified by simulation results.Finally, the paper discusses the issue on contour tracking control of free-floating space robot. Two methods are adopted to solve this problem. The first method is Backstepping control algorithm. The space robot model is decomposed into recursive subsystems, then the Lyapunov equation and virtual controller are determined for each subsystem by Backstepping method, and the control law can be acquired eventually. The second method is feedback linearization. The linear state equation is gained by eliminating the nonlinear part of the space robot model, then via applying the optimal quadratic methods to the linear equation, the ultimate control law is concluded. Simulation results illustrate that both control algorithms can track the desired continuous contour effectively compared to the traditional transposed Jacobian control, moreover, these two methods can also satisfy the design requirements even through the joint disturbance exists.