Automated Assembly Strategy Of Space Structure From Modular Components And Its Ground Experiment

Large space systems,such as space telescopes and giant antennas,are necessary parts in future deep space exploration,navigation communications and astronomical observations.However,due to the delivery capacity limitations of space launch vehicles,such large space systems must be divided into separate modules and constructed by In-Space Assembly(ISA)technology instead of being directly transported into space as a whole.As one of the mainstream methods in the future space operation field,In-Space Assembly(ISA)technology plays an essential role in the deployment of space telescopes and antennas,the reconstruction of spacecraft,the rendezvous and docking of independent spacecraft,as well as the construction of large space structure.The researches on key technologies of In-Space Assembly(ISA)and ground-based verification experiments will provide theoretical foundation and technical support for the construction of future large space systems.This dissertation is motivated by the concept of Robotically Assembled Modular Space Telescope(RAMST)and studies key technical issues of automated assembly of space structures from modular components.A ground-based experiment platform is also constructed to verify the feasibility of the proposed assembly strategy.The main contents of this dissertation are as follows.1)A series of simplified,theoretically scalable hexagonal modular components of a space structure is designed,based on the design of universal connectors and locking mechanisms between modules.Rapid prototyping of these modules is realized by 3D printing technology.2)Combining two kinds of In-Space Assembly robot architectures(fixed-base self-assembly robot architecture and free-flying assembly robot architecture),a ground-based experimental platform that satisfies the precision requirements of verifying the automated assembly strategy is established based on an economical visual measurement system.3)The forward kinematic model of the module transport manipulator in the ground-based experiment platform is established,and the inverse kinematic solutions are obtained by an analytical method.The Hermite interpolation is employed for trajectory planning in the joint space of the manipulator.Thereafter,a PD closed-loop Iterative Learning Control is proposed to manipulate the robotic arm along the planned trajectory to realize grasp,transport and assembly of modules.4)A highly repeatable automated assembly strategy is proposed under the requirements of the assembly task.The grasping stage and installation stage of the strategy are described in details and the overall task sequences of assembling six modules are listed by tables.The effects brought from the visual measurement errors and the physical constraints between modular connectors are effectively reduced via error compensations and attitude adjustments.Finally,a demonstration of the automated assembly task is presented by the ground-based experimental platform,illustrating the feasibility of assembly strategy.