Dynamics And Control Of Space Robot In Self-Assembling On Orbit

With the wide application of large spacecrafts such as international space station having complicated structure and numerous functions, on-orbit assembly, examine and repair, preserve have become focus problems in the astronautics field, and the on-orbit service technology develops. For the special space condition of the spacecraft, manned on-orbit service faces many problems, so the on-orbit self-assembling based on space robot shows its obvious advantages. The dynamics and control problems of space robot in self-assembling on orbit are researched in this paper.It is chosen as the research object, a floating spacecraft base bringing a space manipulator with six degrees of freedom. The DH method is used to establish the coordinate systems of the manipulator joints and their conversion relationships. The recursion method is applied for kinematics modeling, and the dynamics model of this multi-body system is established based on the second kind of Lagrange equation. The dynamics model is written to MATLAB program, and the simulation results are compared with the commercial software ADAMS to verify the correctness of the dynamics model.The collision model and control model used in the space manipulator on-orbit self-assembling process are designed. The end mass point is used to replace the square interchangeable module, and the taper slot is equivalent with the square assembling hole with wedge angle, for simplify and collision detection analysis. Hertz elastic model is introduced to calculate the collision force considering the friction force meanwhile. The controller is designed based on the manipulator operation space theory. The validity of the collision model and control model is verified via simulation and analysis of assembling and disassembling process.The influence factors in the self-assembling process are listed. The control factor method is applied on the six main influence factors including leading speed coefficient, damping speed coefficient, collision stiffness coefficient, collision damping coefficient, friction coefficient, wedge angle, to simulate respectively. The assembly position error, the end collision force and the base attitude control torque are considered as evaluation indexes. The influence form and the extent of each factor is analyzed.The dynamics and control of space robot in self-assembling on orbit are designed and analyzed in this paper. The results can provide theoretical reference to the space manipulator technology in on-orbit service in the future, and is of certain value for engineering application.