Path Planning And Controller Design For Space Target Capturing Manipulator

Space manipulators, specially the space manipulators with autonomy have been widely used in target capturing. To perform the assignment of moving path planing and trajectory tracking control when a space manipulator capturing a target, this paper presents the kinematic equations and dynamic equations of a free floating space manipulator system, and focuses on a path planing problem on how a space manipulator arrives at the destination location when capturing a target under the condition that such manipulator confronts obstacles, a time optimal control problem of space manipulator's moving trajectory palning, and a trajectroy tracking control problem when the uncertainty of system model and additional disturbance are under consideration. This research particularly includes the following four aspects.First, this paper constructs a system model for the space manipulator system, and gives the kinematic equation of such manipulator system. A dynamic equation of such manipulator's joints is also developed by using Lagrange equations, which would be the theoretic basis of the later chapters.Second, for the condition of obstacles, based on artificial potential field function, this paper handles the path planing in joint space. By means of the geometry characteristic features of mechanical arms and obstacles, utilizing collision detection transforms the obstacles in cartesian frame into joint space to yield the obstacle field and free field, then the artifical potential field could be constructed. For the drawback that local minimum point exists in such artifical potential field, a regulation of composition of forces is presented to deal with this problem. At last the optimal trajectory which does not accross with the obstacles is found in joint space.Third, the moving trajectory planing control problem of space capturing is transformed into a standard optimal control problem. The principle of system parameterization, technique of time scale variation and constraints transformation are to format the above optimal control problem into a parameter optimization problem. In order to find the optimal parameter, derive a explicit gradient formula of the objective function on the parameter, and then increase the number of segment points until getting the optimal solution. At last, a simulation about the free floating space manipulator and its corresponding anlyses are given.Fouth, considering the influence of the additional disturbance and uncertainty of system model, present a dynamic model with disturbance about the space manipulator, give a nonsingular fast terminational sliding surface with robustness and interference immunity, which can converge in finite time, design a controller for the trajectory tracking problem of the space manipulator based on the given sliding surface. Such controller figures out the trajectory tracking problem well, and its robustness and interference immunity are confirmed through a numerical simulation.