Research On Mutibody Dynamics And Target Capturing For Free-Floating Space Robot

With the human beings explore the space deeply, the free-floating space robot will paly animportant role in space exploration, and becomes the hot issue for domestic and foreign scholars. Asthe base of the free-floating space robot in the state of free-floating, the entire system is under thenonholonomic constraint, which making the design of the control more difficult for the free-floatingspace robot capturing the target, so, it is necessary to study the multibody dynamics. Due to the natureof the space system, it requires high efficiency multibody dynamic modeling method. Therefore, thisthesis will focus on resolving some challenging problems, which include the rigid multibodydynamics of the free-floating space robot and expansion its sysytems, the flexible multibodydynamics of free-floating space robot, target capturing method and presents a ground test systemsolution. The main contributions of this thesis are as follows:The high efficiency of the multibody dynamics modeling algorithm based on spatial operatralgreba(SOA) is studied.. The recursive Newton-Euler kinematic equations on screw form for thespace robot are derived, and the techniques of the sequential filtering and smoothing methods inoptimal estimation theory are used to derive an innovation factorization and inverse of the generalizedmass matrix in explicit, and the multibody dynamic equatons for the general multibody dynamicsysytems, the high efficient soluations to the forward multibody dynamics problem and backwardmultibody dynamics problem algorithms are established. The SOA algorithm has a simple mathexpression, high compulational efficiency and clear physical understanding advantages.Based on spatial operator algreba theory, the multibody dynamics of expansion of thefree-floating space robot sysytems are studied, and the general dynamic equations for the treemultibody dynamic system, underactuated multibody dynamic system and close loop multibodydynamic system are established. The high efficient multibody dynamic modeling algorithm can beused for real time dynamic simulation for space systems. Based on sliding mode variable structurecontrol algorithm, analogise to the block generalized mass matrix, under the active control inputs theactive joints and passive joints both can convergence to desired state.The flexible multibody dynamic systems are studied. Using the technology of the finite elementmethod, combing with the rigid multibody dynamic method based on spatial operator algreba theory,the flexible multibody dynamic equations are established, and the high efficient dynamic computationalgorithms for forward and backward dynamic problems are proposed. Based on binocular stereo visual servo method, the target capturing method of the free-floatingspace robot is proposed, and the simulation software is designed. The binocular stereo vision systemis used to measure the position and posture of the target in base body coordinate, and feedback to therobot control system. According to the manpulator’s motion of the space robot compute the motion ofthe base body in the software by the high efficient reat-time dynamic computation algorithm. Formthe simulation software we could found that the target capturing method based on binocular stereovision of the free-floating space robot could implement the target tracking and capturing, indicatingthat the targrt capturing method is feasible.The reliability and feasibility of the spacecrafts Activities, not only need theory verification, butalso need the actual physical test on the ground. By the advantage of the real-time multibody dynamicalgorithm in modeling and computation efficiency, a hybrid ground test platform is proposed. Thebase of the free-floating space robot is connected to the end effector of the6degrees of freedomindustrial robot, according to the manipoulator’s motion of the space robot the base motion iscomputed by high efficient real-time dynamic algorithm, and then uses the industrial robot to simulatethe actual base motion to implement the real base motion in the space of the free-floating space robot.After the ground physical test platform is completed, target capturing method of the free-floatingspace robot could be by verified further experiments.