Design And Implementation Of Robotic Processing System For Special-shaped Gaskets For Assembly Of Large Aeronautical Components

In the process of large aircraft wing assembly,the gap between non datum planes often occurs because of machining error or deformation in the assembly process,which leads to the decrease of structural strength after assembly.It may leads to the occurrence of vibration in the service process of the aircraft,even affects the operation safety of the aircraft.To reduce the influence of assembly clearance on the whole structure,in the process of assembly,it is necessary to customize the processing gasket to fill the clearance area according to the shape of the clearance.Because the assembly gap is very closed in the space,and the surface of the assembly gasket is a continuous surface with non-uniform thickening,the assembly gasket processing is mainly completed by Trial grinding according to experience.How to obtain the CAD contour of the gasket through the limited measurement data,and to realize the customized processing of the special-shaped non-uniform thickness gasket by robotic processing technology,is of great importance in engineering machining.In this paper,assembly clearance location and required assembly gasket model shape are obtained through aircraft component model assembly,assembly gasket processing allowance calculation is realized,grinding process removal model is deduced,and customized processing parameters and processing track planning of robot are planned.:Aiming at the characteristics of complex thickness distribution and small thickness variation difference of assembly gasket,this paper uses robotic grinding as the processing method of gasket to process standard thickness aluminium alloy material.Based on Preston equation,a material removal model for robotic grinding is established,which realizes effective control of grinding depth during grinding process.The influence of processing parameters on the material removal model for grinding is analyzed.The feed speed in the process of robot machining is selected as the control variable to control the thickness of the gasket during the process of gasket machining.In the actual assembly process,it is relatively difficult to measure the assembly gap accurately in the whole area.At present,there is no effective method.In this paper,by obtaining the assembly gap model from point cloud envelope of each assembly component,the thickness distribution in the assembly gap model is calculated by using the shape diameter function algorithm,and the position of the possible gap and the required gasket shape are obtained by simulation of the assembly operation.On this basis,the gasket point cloud is divided into several areas according to the processing allowance interval by using the point cloud geometric segmentation algorithm based on the approximate planarization idea,and the boundary of each point cloud area is identified by DBSCAN algorithm.The equivalent machining allowance curve of gasket model can be obtained.For the trajectory planning and process planning of robot in the autonomous processing of heterogeneous and non-uniform thickness gaskets,this paper uses the bounding box-based cross-section method as the trajectory planning strategy,and obtains the robot processing trajectory line and corresponding processing residual curve by intersecting the processing residual distribution model with the cross-section.The curve ofrobot feed speed during machining along the trajectory line is calculated by grinding material removal model.The feed speed curve is discretized by using the thinning algorithm,and the discrete points are projected to the machining trajectory of the robotic processing to obtain the discrete track points and the corresponding machining feed speed of the gasket machining.The robotic independent grinding trajectory planning software for customized machining of assembly gasket is developed.The customized machining platform is built by using Efort robot and Festool grinding mechanism,and the assembly gasket between aircraft wing and fuselage is used as the experimental object for machining verification.The test results show that the wing assembly gaskets obtained by the robot grinding method are superior to the traditional manual processing in processing accuracy and surface quality,which verifies the reliability and practicability of the assembly gaskets robot processing system.