Research On Control And Simulation For Laser Flying Marking System And Laser Processing Robot

Laser processing robot is one of the advanced manufacturing techniques which integrates the technologies of lasers, robots, CIMS, CAD\CAM, material processing and so on. The laser beam with high power density was transferred through fiber or mirrors mounted on multi-joints mechanics and the focused laser was controlled to move along with the pre-programmed graphics accurately on the material surface to realize various 2D or 3D processing works of dots, lines or curves and surfaces.In this dissertation, the studies are focused on the control system of 2D laser flying marking and the simulation system of 3D laser processing robots. The control card based on PCI bus and the control software based on windowsWindows OS for laser flying marking were developed, the related algorithms were investigated, which includes motion-tracking model, graphics objects scanning path and laser processing path (LPP) optimization. Different modeling methods for 5-dof laser processing robots were analyzed, the kinematics formula and processing path generating methods were studied and a processing simulation system for 3D robot was realized.Laser processing path optimization problems were analyzed and an immune genetic algorithm was designed to optimize them. A novel path sequence chromosome model that consists of signed integer genes was presented, in which the absolute value of the gene is the stroke index, the position of gene in the chromosome indicates the processing order and the sign represents the processing direction. Two immune operators, smooth immune operator and 3-segs optimal immune operator based on heuristic information were brought forward to improve the GA search performance. Smooth immune operator is based on the common triangle inequality theorem, which was designed to eliminate the self-intersection faults of chromosome. 3-segs optimal immune operator is based on perfect building block theorem and it is a local optimal operator. The combination of both immune operators would improve the search speed and local-search performance of GA significantly. The experimental results showed that 48.96% of air path in a marking graphics was shortened and 8.57% of total laser marking time was reduced. This algorithm could be widely used for other applications such as laser welding, laser marking, laser show and so on.The control algorithms for laser flying marking system have been studied in this dissertation. Different motion-tracing methods including open-loop computing method and closed-loop offset-detecting method were analyzed and compared. For open-loop computing method, the moving offset is computed according to a motion tracing formula, which is only suitable for applications of constant speed. For closed-loop offset detecting method, moving offset is fed back directly from the rotary coder and it represents real displacement of work piece at any moment, hence it is suitable for both applications of constant or variable velocity. Secondly, the flying speed performance of laser flying marking system have been studied. The scanning area limitation (SAL) specialty and defined maximum markable time(MMT) and maximum marking offset(MMO) were proposed. A maximum flying velocity (MFV) formula of laser flying marking system has been deduced and the impacting factors, including marking time, the length of marking graphics in the moving direction and the marking order of graphics object, were studied. All objects entered marking(AEM), rowed first object entered first marking (RFEFM) and first object entering first marking(FEFM), were presented. Experimental results satisfied theoretical MFV calculations and it showed that there was a best MFV performance when using FEFM scanning path algorithm in transverse moving direction. Above work will benefit for the industrial field to improve the performance of laser flying marking system.3D laser processing robot simulation has been investigated in this dissertation. Firstly, the joints mechanics and laser transferring path of different dof robots were analysed. The forward and inverse kinematics equations of 3D laser processing robots (3P2R and 5R structure) have been derived and the location errors of both structure were analyzed. Based on the OpenGL environment we developed a simulation system for 3D laser processing robots, and realized the function of editing processing paths of plane graphics and intersection spline in 3D environment. Based on the Open CASCADE 3D engine, we developed another simulation system for 3D robot, in which the robot model is assembled with IGES files joints model and complex processing path of 3D accessory edges could be generated automatically from its model topology data. These work could be useful for the development of control system or off-line program system for laser processing robots in the future.