Research On Motion Planning And Control Of Free Floating Space Robot Oriented To On-orbit Service

On-orbit service techniques of spacecraft become the hot spot for the space explorations of human which are more and more frequent and complicated. Space robot system has incomparable superiority in the field of on-orbit service to spacecrafts, especially it has the long life time and good safety when using the free floating space robot system to execute the on-orbit service. Whether the free floating space robot can execute on-orbit service well, the motion planning and control methods research are the important foundations and key theory and technique problems, thus, developing the relevant research has important theoretical and practical significance.To achieve the space target safe rendezvous approaching, the trajectory planning in target capture, stable trajectory tracking control in on-orbit service of free floating space robot, the paper considers the special characteritics possessed by free floating space robot different from the fixed base robot, based on the kinematics and dynamics of free floating space robot system, mainly studies the safe rendezvous path planning of non-cooperative space target, the trajectory planning avoiding dynamics singularity, the trajectory planning with base attitude variation constrainted, the adaptive trajectory tracking control and adaptive robust trajectory tracking control in Cartesian space. Concrete content includes:The motion equation of free floating space robot(the chaser satellite) in the Orbit coordinates is set up; the kinematics equation under non-holonomic constraint of free floating space robot in inertial coordinates is derived, the dynamics parameters characteritics of Jacobian matrix caused by non-holonomic contraints are analyzed, the researchable workspace of free float space robot is given, the joint singular space and the Cartesian singular space of the system are computed based on the Jacobian matrix; dynamics model in joint space of free float space robot based on extended manipulator is set up using Lagrange equation, the inner dynamics of the system is analyzed. The work mentioned above provides the following chapters with the research base.Aiming at rendezvous path planning of free floating space robot(the chaser satellite) in outer space, the path planning method to ensure safe approaching the non-cooperative space target based on the orbit mechanical equation is proposed. The whole rendezvous path planning strategy and safety principle of rendezvous path planning in ultimate approaching stage of free floating space robot are researched; Based on orbit mechanical equation, the moving ellipse locus of free floating space robot is generated using the safety principle to approach the non-cooperative space target in ultimate approaching stage. The method realizes that the space robot system approaches the spinning non-cooperative space target in free floating work mode, and the robot can escape safely when the subsequent work could not be normally completed.The singularity of system Jacobian matrix is relative to the dynamic inertia parameters for the angular momentum conservation equation of free floating space robot is non-integrable, the dynamic singularity resulted from that increases the difficulty of trajectory planning. Aiming at the generalized Jacobian matrix dynamic singularity caused by non-holonomic constraints, employing the scheme of decomposing kinematics equation, an indirect solving inverse kinematics method is obtained by the iterative function constructed. The method avoids direct solving inverse generalized Jacobian matrix, transforms the dynamic singularity to kinematic singularity, and resolves the path relativity caused by system Jacobian matrix singularity. The method avoids dynamics singularity, achieves the non-holonomic trajectory planning of free floating space robot.The status of the base of free floating space robot is freely floating, thus the disturbance to the base attitude due to the manipulator movement is generated, namely the attitude disturbance characteristic exists in the system caused by dynamic coupling of manipulator and base, but the stability of the base attitude is very important to ensure the communication between the system and earth and the normal work of solar battery. Aiming at the attitude disturbance characteristic existing in free floating space robot system, employing redundant manipulator to realize the end-effector of manipulator trajectory planning and ensure the base attitude variation is constrainted simultaneously, mainly studies the fundamental theories and trajectory planning of free floating space robot with zero-disturbance to base attitude. To realize zero-disturbance to base attitude of free floating space robot during the whole motion, the zero-disturbance to base attitude constraint equation with non-holonomic characteristic is introduced, zero-disturbance to base attitude curve group is constructed, a non-holonomic trajectory planning method in joint space is proposed. The method realizes end-effector of manipulator reaches the desired point and ensures zero-disturbance to base attitude simultaneously by planning the manipulator motion only.Some system parameters are difficult to be accurately determined in free floating space robot, thus to track the designed trajectory with good precision, the controller should have the capability of adaptation to modify some parameters of controller automatically to adapt the variation of the control objective. To resolve that the reference trajectory in inertia space can not be realized in joint space and to avoid system dynamic equation can not be parameterized, the extended manipulator method is employed and the adaptive trajectory tracking of free floating space robot in Cartesian space is researched to resolve those problems. Based on the dynamics equation derived in Cartesian space, aiming at the inertia parameter uncertainty of system, the composite adaptive trajectory tracking control in Cartesian space is studied, the controller are designed and the controller stabilities are analyzed respectively. The simulation results show that the adaptive control strategies can ensure the asymptotic stable tracking to the desired trajectory of end-effector.Aiming at the non-parameterized uncertainty of free floating space robot, the external disturbances, the adaptive robust trajectory tracking control of free floating space robot is researched. Based on extended manipulator method, the dynamic models of free floating space robot in Cartesian space considering external disturbances of manipulator and base are set up; the robustness of composite adaptive controller with the external disturbance boundary known is analyzed, then the robustness of revised adaptive law is analyzed; the modification of adaptive law with the external disturbance boundary unknown is researched; combining the sliding mode control, the adaptive sliding mode controller of free floating space robot is designed, the stability and robustness of the controller are analyzed.