Intelligent Planning And Control Of Robot Trajectory For Complex Intersecting Curves Machining

The sphere-pipe intersecting curve is a kind of complex spatial curve,it is the intersection formed by sphere and round pipes on their surface.The cutting and welding tasks of the sphere-pipe intersecting curve are widely exist in aerospace,nuclear power,shipbuilding,pressure vessels and other fields,its automated machining technology has always been a problem in related fields.Today,the cutting and welding of the sphere-pipe intersecting curve still rely on a lot of manual work,which has high labor intensity,harsh operating environment and difficult to guarantee the machining quality.With the development of industrial robot technology,using robots to cut and weld the intersecting curve has become an important development direction in this field.To improve the automation level of sphere-pipe intersecting curve cutting and welding,this thesis conducts in-depth research on sphere-pipe intersection mathematical model and its geometric characteristics,the intelligent planning of robot trajectories for intersecting curve cutting and welding,and the robot trajectory control technology.The thesis systematically solves the robot trajectory intelligent planning and control of the sphere-pipe intersecting curve machining,including trajectory planning of the robot plasma cutting for sphere-pipe intersection with single-Y welding groove,robot welding trajectory planning,reconstruction and planning of the non-ideal sphere-pipe intersecting curve trajectoryFirst,focuses on the complex "one-sphere multi-pipe" sphere-pipe joints,the mathematical model of sphere-pipe intersection is established,which can cover most of the intersection types,and this thesis also gives the parameter expressions of the standard intersecting curve.On this basis,the description of the sphere-pipe intersection two-sided frame is given and the groove coordinate system and the tool coordinate system are established.The cutting trajectory models of the groove and root face are obtained through the spatial transformation between established coordinate systems.Through the research on the geometric model of plasma torch and plasma cutting process characteristics,an intelligent compensation algorithm for plasma beam radius is proposed,which can intelligently compensate the tool radius based on the thickness of the workpiece during machining.At the same time,considering the actual machining conditions,the plasma torch nozzle height control has been studied to ensure the stability of the plasma arc voltage and prevent the interference collision of the nozzle and the workpiece.According to integrating plasma beam radius intelligent compensation and torch nozzle height dynamic control,this thesis gives the robot cutting trajectory'description of sphere-pipe intersecting curveSecondly,based on the sphere-pipe model with single-Y groove,this thesis establishes the weld seam coordinate system,and gives its homogeneous transformation matrix relative to the groove coordinate system,then gives the weld seam curve parameter equation and attitude representation.On the other hand,the mathematical model of the torch attitude is established through analyzing the welding process of intersecting curve welds.To solve the welding problems caused by continuous change of the sphere-pipe weld seam inclination,two solutions are proposed.The first solution is to adjust the welding torch attitude intelligently and supplement it with the swing welding technology,which can effectively solve the problems of up and down slope welding in the welding process.This solution is suitable for the situation where the weld seam inclination is small.Another solution is constituting a welding workstation through combining an industrial robot with a two-axis positioner.Utilizing the linkage of the positioner and the industrial robot,the position and attitude planning of the intersecting curve welding,to ensure the weld inclination angle is always controlled within a very small range.This method is suitable for the case where the weld inclination angle is large and can effectively improve the welding processability.Considering the welding task of sphere-pipe joints with groove and thick-walled workpiece,a multi-layer single-pass swing welding planning method is given.Integrating it into the robot's welding trajectory planning,the trajectory description of sphere-pipe intersecting curve welding is obtained finallyThirdly,the robot machining technology of non-ideal sphere-pipe intersecting curve based on laser measurement is studied.A laser sensor is used to scan the cutting trajectory or welding seam,and the feature points on the actual cutting or welding trajectory are obtained using the proposed measurement and welding seam feature recognition algorithm.Using NURBS curve to fit these feature points,the cutting and weld trajectory of non-ideal sphere-pipe intersecting curve is reconstructed,and then combining the geometric characteristics of the sphere-pipe intersection model,the robot tool attitude reconstruction approach of cutting or welding is given.Finally,MATLAB and ADAMS simulation software are used to verify the related theories and algorithms proposed in this thesis.An intersecting curve robot cutting and welding trajectory verification platform is built to verify the feasibility and accuracy of cutting or welding trajectory planning.And an automatic programming system of intersecting curve robot cutting and welding is developed.The related work of this thesis laid the foundation for the automatic cutting and welding of the sphere-pipe intersecting curve.