Research On Positioning Technology Of Thermal Insulation Tiles Assembly Based On Measured Model

Thermal insulation tiles are important parts of the thermal protection system for reusable launch vehicle,and their assembly quality has a critical impact on aircraft performance and safety.However,the thermal insulation tiles are characterized with rigidity and brittleness and the array arrangement on the aircraft body as well as form of non-direct contacted fitting,which make that the traditional methods of assembly analysis and positioning are difficult to fully meet the requirements of thermal insulation tile assembly.Therefore,this thesis presents an assembly technology of thermal insulation tile based on the measured model.The measured model constructed with scanned point cloud replaces the theoretical model,and the measured model is participated in the feature calculation during the assembly process.The industrial robot with measurement assistance is used to positioning of thermal insulation tiles.In this thesis,the in-depth study on the construction of measured model,assembly pose optimization and precise positioning of thermal insulation tile is carried out.The main research contents of the thesis are as follows:(1)Aiming at the problem of explicit expression of geometric features and assembly coordination features in assembly calculation,we propose a representation model for geometric features of thermal insulation tiles.Further,we combine the geometric features model and the semantic information to build a comprehensive representation model that named measured model.Based on measured model,the method for evaluating the accuracy of geometric features is studied.Moreover,a concept of the simplest measured model that combines the accuracy information of geometric features is proposed.(2)Based on the concept of measured model of thermal insulation tile,a method for constructing geometric features is proposed.Through the extraction,optimization and division of non-ideal features,the shape of the thermal insulation tile is expressed by three basic elements: point,line and surface.Finally,through the simplification of the mesh,the data reduction of measured model under the condition of feature accuracy is realized.(3)The pose optimization method of assembly for thermal insulation tile with measured model is studied.Firstly,we give the pose transfer model of the assembly of thermal insulation tile by rigid body kinematics theory.On this basis,the constraint state of the assembly of thermal insulation tiles is studied and the multi-constrained fitting model of thermal insulation tile is constructed.Finally,aiming at the problem that the weight coefficient of traditional method is difficult to determine,a pose evaluation model based on tolerance zone is proposed to realize the accurate evaluation of the assembly pose of thermal insulation tiles.(4)For the grasping and positioning of thermal insulation tiles,an online positioning system for thermal insulation tiles based on industrial robot is designed.Based on the system,the coordinate system construction and calibration method are studied,and the online positioning error model and pose transmission model of industrial robot is established to realize the mapping of online measurement data to robot motion parameters.Aiming at the shortcomings of the absolute positioning accuracy of industrial robots,a robot pose compensation method based on online measurement is proposed.The precise positioning of thermal insulation tiles is realized from three aspects: relative pose compensation,absolute positioning compensation and relative translation motion compensation.Based on the research of the above key technologies,we develope a prototype system for the positioning of thermal insulation tiles.Based on the prototype system,the correctness of the theory and method proposed in this thesis is verified with some systematic comprehensive experiments.