| When the heavy load forging manipulator becomes larger and heavier, the safe operation problem has attracted most attention. It already could not meet the requirements of the mechanism or structure design and optimization on the basis of the static and partial dynamic analysis. In this paper, the rigid-flexible multibody dynamic analysis of the whole manipulator is carried out by the numerical simulation to guide the fatigue analysis and structure optimization.The first step for rigid-flexible analysis is to choose the flexible body. A floating reference coordinate system must be defined to describe the rigid body motion, in which the elastic deformation should be small. Traditionally, the elastic deformation is approximate by the linear combination of main vibrations modes, which is not adequate to describe the deformation of the heavy load forging manipulator with very huge forging force.In this paper, the strategy for selecting the reference coordinate system of a flexible body is introduced firstly. Furthermore, the main modes and constraint modes are described in detail. Then, the multibody dynamical differential equation is deduced using the principle of Jourdain virtual power.In addition, the heavy load manipulator is a parallel servo mechanism with multiple redundant constraints controlled by the intricate hydraulic loops. It requires precise control strategy while modeling in SIMULINK with costly computational efforts. To improve the computational efficiency, we introduce the equivalent nonlinear stiffness of the hydraulic cushion based on Conservation Law and Bernoulli equation.Finally, the geometric model is constructed in UG the codes of the modal analysis of beams, the nonlinear stiffness and the system initial state are written in MATLAB modal analysis of large components is made in ANSYS. All the results are imported into SMPACK, and the flexible multibody dynamic analysis under various working conditions are carried out by numerical simulation.
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