Research On Space Assembly Of Primary Mirror System For Space Telescope

Currently,the world has many types of space telescope.High precision and large-caliber space telescope has the advantage that it will not be disturbed by earth atmosphere and its image resolution is high and other.It is gradually becoming the main future development direction.However,limited by volume and loading of existing launch vehicle,the structure of integral type and unfolded space telescope can easily reach the upper limit of the caliber and can hardly meet the launch requirement of heavy caliber space telescope.Therefore,it is a most feasible method which is proposed currently to construct heavy caliber space telescope through modularization launch and on-orbit assembly method.This thesis proposes the idea for constructing heavy caliber space telescope,launches assembly unit of space telescope which is modularized into the space and finishes on-orbit assembly through space robot.This thesis conducts research for on-orbit assembly of space telescope primary mirror system and the main research content is as follow:Firstly,a kind of modularization space telescope primary mirror system for on-orbit assembly is designed.According to total index requirement of space telescope,the initial whole scheme design of space telescope is conducted.The key point is to conduct design for mechanical connection between sub-mirror modules and locking mechanism of primary mirror system.Two kinds of feasible assembly scheme are constructed.Corresponding sub-mirror module configuration is analyzed.The assembly sequence of primary mirror system is studied.The influence of the assembly clearance between sub-mirror modules for the terminal position precision of assembly positioning chain of primary mirror system is analyzed.Then the optimal trajectory planning method based on time during primary mirror system assembly is studied.The kinematic model of mechanical arm is built.The forward kinematics of mechanical arm is analyzed.The damped least square method is adopted to calculate mechanical arm inverse kinematics.The work space of mechanical arm is analyzed.The applicability to primary mirror system assembly task is verified.Under the joint space,cubic B-spline curve which has good derivative continuity and partial supporting is adopted to conduct trajectory planning for mechanical arm.On this basis,the mechanical arm joint angle and the limit of speed and accelerated speed are taking into consideration.By regarding the shortest operational time as the purpose of optimization,the genetic algorithm is used to conduct optimization for cubic B-spline track of sizing value point.Finally,the assembly and control strategy of main error system is studied and the experimental verification is conducted.According to the characteristic and requirement of on-orbit assembly task,three assembly principles are proposed.The assembly task planning of the primary mirror system is finished.Cartesian space impedance control and the pose adjustment based on force feedback are used and the initial interposition assembly of sub-mirror module is fulfilled.The Cartesian impedance control which has superposed force oscillation is adopted and the middle and later period interposition assembly of sub-mirror module is achieved.The problem of easy blocking due to the fact that the assembly clearance is too small is solved effectively.The typical sub-mirror module assembly experiment platform is built.Kuka mechanical arm is used to conduct the assembly experiment of two types of sub-mirror module and the effectiveness of assembly strategy is verified.