Research On The Stiffness And Milling Of A Dual Manipulator Contact Cooperative System

Series industrial robotic arms have been widely used in aerospace,automotive industry and shipbuilding,with specific application processes including welding,grinding and polishing.However,compared with traditional machine tools,the mechanical arm still has disadvantages such as poor positioning accuracy and rigidity,which make it difficult to achieve ideal results in milling with high load strength.In recent years,multi-arm collaborative machining technology has gradually matured,and many defects of traditional single-arm machining have been remedied by its advantages of strong load capacity,high fault tolerance and distributed control.In this paper,a contact collaborative machining method with two mechanical arms is proposed to solve the above problems and applied in milling.The master mechanical arm is used for milling,the slave arm provides mobile auxiliary support to enhance the rigidity of the milling system.Through milling experiments,it is shown that the proposed method has certain advantages,including the following main contents:(1)Kinematic model of KUKA KR 60-3 industrial mechanical arm is established by improved D-H method.The geometric coupling constraint equation of the robot arm in cooperative motion is established and the working space of the cooperative system is analyzed.Jacobi matrix is deduced based on differential transformation method,and collaborative error model and evaluation index of robot arm collaborative system are established.It lays a foundation for the subsequent research on the method of doublearm collaborative machining.(2)A flexible joint is designed to safely realize contact coupling at the end of double arm by analyzing synergy error and actual stiffness requirements.The stiffness model of a dual-arm system with flexible joints is derived.The simulation verification by multi-body mechanical software shows that the design of flexible joint meets the actual requirements.Finally,based on the virtual centralized inertia mass bar method,the end loads of the two mechanical arms are analyzed to provide theoretical basis for milling experiments.(3)Joint stiffness identification experiments are carried out,various positions and positions of the robot arm are selected and loaded differently.Six-dimensional deformation of the end is obtained by structured light three-dimensional scanner,and joint stiffness is fitted by least square method.The machining platform of dual-arm collaborative system is built and the static load deformation test of the dual-arm collaborative system is carried out,which shows that the rigidity performance of the dual-arm collaborative system is significantly improved compared with that of the single-arm system.(4)According to the stiffness performance change of contact-type collaborative system of double mechanical arms,the collaborative milling experiment of double mechanical arms and the single mechanical arm milling experiment are carried out in different directions in different position areas of the work table and the same position area,and the surface quality of the two machining arms along the milling path is analyzed statistically.The results show that contact-type collaborative milling of double mechanical arms has obvious advantages under certain circumstances.